Cover Image

Equipment*Packet:*Ventilators*UMDNS*#:*15613/Date*of*Creation:/December/2,/2015/Creator:/Complied/by/Cassandra/Stanco/for*Engineering/World/Health/(EWH)***Equipment*Packet*Contents:*This/packet/contains/information/about/the/operation,/maintenance,/and/repair/of/external/ventilators/and/ventilators/for/anesthesia/systems.///Part*I:*External*From*the*Packet:** 1. An*Introduction*to*Ventilators:*/PowerPoint/*Part*II:*Included*in*this*Packet:** 1. Operation*and*Use:*a. Brief/Introduction/to/Intensive/Care/Ventilators/(p./3)/b. Brief/Introduction/to/Neonatal/Ventilators/(p./4)/c. Overview/of/Medical/Ventilation/(p./5R8)/d. Operation/and/Use/of/Ventilators/(p./9R13)/e. Testing/Procedures/for/Ventilators/(p./14R20)/2. Diagrams*and*Schematics:*a. Figure/1:/Parts/of/the/Respiratory/System/(p./22)/b. Figure/2:/WHO/Specification/for/Anesthesia/Ventilator/(p./23R27)*3. Preventative*Maintenance*and*Safety:*a. Ventilator/Preventative/Maintenance/Checklist/(p./29)*b. Calibration/of/Ventilators/(p./30R35)*c. Ventilator/Safety/and/Performance/Checklist/(p./36)/4. Troubleshooting*and*Repair:**a. Ventilator/Troubleshooting/Table/(p./38)/5. Resources*for*More*Information*a. Resources/for/More/Information//(p./40)*b. Bibliography/(p./41)** /** *

* 1.*Operation*and*Use*of*Ventilators****Featured*in*this*Section:**/ /Malkin,/Robert./“2.2/Ventilators.”/Medical'Instrumentation'in'the'Developing'World./Engineering/World/Health,/2006.////WHO./“Anesthetic/and/Resuscitation/Equipment.”/Maintenance'and'Repair'of'Laboratory,'Diagnostic'Imaging,'and'Hospital/Equipment'(WHO:/1996),/p./121Z134.///WHO./“Ventilator,/Intensive/Care.”/From/the/publication:/“WHO/Technical/Specifications/for/61/Medical/Devices./WHO./Retrieved/from:/ /Wikipedia./“/Medical/Ventilator.”/Wikipedia,/pp./1Z17./Retrieved/from:/ /////////*/*****
© Copyright ECRI Institute 2011 (not including the GMDN code and device name).

Reproduced with Permission from ECRI Institute’s Healthcare Product Comparison System.

© Copyright GMDN Agency 2011. GMDN codes and device names are reproduced with permission from the GMDN Agency.










n Health problem addressed

Ventilators provide temporary ventilatory support or respiratory
assistance to patients who cannot breathe on their own or who
require assistance to maintain adequate ventilation because of
illness, trauma, congenital defects, or drugs (e.g., anesthetics).

Product description
Ventilators consist of a fl exible breathing circuit, a control system,
monitors, and alarms. The gas is delivered using a double-limb
breathing circuit. The gas may be heated or humidifi ed using
appropriate devices. The exhalation limb releases the gas to the
ambient air. Intensive care ventilators are usually connected to a
wall gas supply. Most ventilators are microprocessor controlled
and regulate the pressure, volume, and FiO2. Power is supplied
from either an electrical wall outlet or a battery.

Principles of operation
The control mode provides full support to patients who cannot
breathe for themselves. In this mode, the ventilator provides
mandatory breaths at preset time intervals and does not allow
the patient to breathe spontaneously. Assist/control modes
also provide full support by delivering an assisted breath
whenever the ventilator senses a patient’s inspiratory effort and
by delivering mandatory breaths at preset time intervals. With
volume-controlled breaths, a control system is used to ensure
that a set tidal volume is delivered during the inspiratory cycle.
Pressure-controlled breaths regulate fl ow delivery to attain and
sustain a clinician-set inspiratory pressure level for a set time so
that the ventilator delivers controlled or assisted breaths that
are time cycled. Combination modes are also available.

Operating steps
Users fi rst check that the unit is ready for use (e.g., run
performance and calibration checks). They next make sure that
settings (including alarm levels) are correct and appropriate for
the patient type and condition. Once completed, the patient
is connected to the ventilator. When the ventilator-patient
connection is completed, users ensure the patient is being
properly ventilated. While patient is being ventilated, caregivers
monitor/evaluate the patient, and respond promptly to alarms.

Reported problems
Risk of acquiring pneumonia may be minimized by following
proper infection control procedures. Leaks in the breathing
circuit or components may prevent the ventilator from delivering
the appropriate amount of ventilation. Proper maintenance and
avoiding operator errors or machine failures can be critical.
Critical changes in patient conditions can be missed if alarms
are not set properly or are not noted by clinical staff.

Use and maintenance
User(s): Physicians, nurses, respiratory
therapist, other medical staff

Maintenance: Biomedical or clinical engineer/
technician, medical staff, manufacturer/

Training: Initial training by manufacturer,
operator’s manuals, user’s guide

Environment of use
Settings of use: Intensive care, critical care
settings, surgery

Requirements: Uninterruptible power source,
battery backup, proper tubing/masks

Product specifi cations
Approx. dimensions (mm): 125 x 40 x 62

Approx. weight (kg): 67

Consumables: Batteries, tubing, masks, fi lters

Price range (USD): 9,000 - 60,000

Typical product life time (years): 8, depends
on hours used

Shelf life (consumables): NA

Types and variations
Cart or stand mounted

Ventilator, Intensive Care
17429 Ventilators, Intensive Care 42411 Intensive-care ventilator, adult/infant

Other common names:
IC ventilators, critical care ventilators, continuous ventilators, positive-pressure ventilators; Adult ventilator; Respirator,
© Copyright ECRI Institute 2011 (not including the GMDN code and device name).

Reproduced with Permission from ECRI Institute’s Healthcare Product Comparison System.

© Copyright GMDN Agency 2011. GMDN codes and device names are reproduced with permission from the GMDN Agency.










n Health problem addressed

Neonatal intensive care ventilators provide ventilatory support
to preterm and critically ill infants who suffer from respiratory
failure and who generally have low-compliance lungs, small
tidal volumes, high airway resistance, and high respiratory
rates. These mechanical ventilators promote alveolar gas
exchange (oxygenation and carbon dioxide [CO2] elimination)
by generating positive pressure to infl ate the lungs of an infant
who is incapable of adequate independent breathing.

Product description
A typical neonatal ventilator system consists of a breathing
circuit, a humidifi cation system, gas-delivery systems, monitors
and their associated alarms, and gas sources for oxygen (O2)
and compressed air. Ventilators also require an integral or
add-on-oxygen-air proportioner (blender) to deliver a fraction
of inspired FiO2 between 21 and 100%. Controls are used to
determine the operating mode and ventilation variables. Most
ventilators have several operating modes.

Principles of operation
Intensive care ventilators designed for neonatal and/or pediatric
respiratory support are mostly time-cycled pressure-control
devices. CPAP is useful for infants with restrictive lung disease
or decreased lung compliance and alveolar collapse (infants with
hyaline membrane disease); PEEP maintains lung volume and
prevents alveolar collapse. High-frequency ventilation delivers
small tidal volumes around a near-constant mean airway pressure
(MAP) at frequencies higher than those produced during the
fastest possible panting (i.e., above 100 breaths per minute),
thus avoiding both high and low extremes of lung volume.

Operating steps
Users fi rst check that the unit is ready for use (e.g., run
performance and calibration checks). They next make sure that
settings (including alarm levels) are correct and appropriate for
the patient type and condition. Once completed, the patient
is connected to the ventilator. When the ventilator-patient
connection is completed, users ensure the patient is being
properly ventilated. While patient is being ventilated, caregivers
should monitor/evaluate the patient, and respond promptly to

Reported problems
Risk of acquiring pneumonia may be minimized by following
proper infection control procedures. Leaks in the breathing
circuit or components may prevent the ventilator from delivering
the appropriate amount of ventilation. Proper maintenance and
avoiding operator errors or machine failures can be critical.
Critical changes in patient conditions can be missed if alarms
are not set properly or are not noted by clinical staff.

Use and maintenance
User(s): Physicians, nurses, respiratory
therapist, other medical staff

Maintenance: Biomedical or clinical engineer/
technician, medical staff, manufacturer/

Training: Initial training by manufacturer,
operator’s manuals, user’s guide

Environment of use
Settings of use: Neonatal intensive care unit
(NICU), pediatric intensive care unit (PICU),
critical care settings, surgery

Requirements: Uninterruptible power source,
battery backup, proper tubing/masks

Product specifi cations
Approx. dimensions (mm): 29 x 53 x 45

Approx. weight (kg): 27

Consumables: Batteries, tubing, masks, fi lters

Price range (USD): 7,500 - 45,000

Typical product life time (years): 8

Shelf life (consumables): NA

Types and variations
Cart or stand mounted

Ventilator, Intensive Care, Neonatal/Pediatric
14361 Ventilators, Intensive Care, Neonatal/Pediatric 14361 Intensive-care ventilator, neonatal/paediatric

Other common names:
Continuous ventilators, neonatal ventilators, pediatric ventilators, positive-pressure ventilators, time-cycled ventilators;
Ventilator, infant

Medical ventilator 1

Medical ventilator

The Bird VIP Infant ventilator

A medical ventilator may be defined as any machine designed to
mechanically move breatheable air into and out of the lungs, to provide
the mechanism of breathing for a patient who is physically unable to
breathe, or breathing insufficiently. See also mechanical ventilation.

While modern ventilators are generally thought of as computerized
machines, patients can be ventilated indefinitely with a bag valve
mask, a simple hand-operated machine. After Hurricane Katrina,
dedicated staff "bagged" patients in New Orleans hospitals for days
with simple bag valve masks.

Ventilators are chiefly used in intensive care medicine, home care, and
emergency medicine (as standalone units) and in anesthesia (as a
component of an anesthesia machine).

In its simplest form, a modern positive pressure ventilator consists of a compressible air reservoir or turbine, air and
oxygen supplies, a set of valves and tubes, and a disposable or reusable "patient circuit". The air reservoir is
pneumatically compressed several times a minute to deliver room-air, or in most cases, an air/oxygen mixture to the
patient. If a turbine is used, the turbine pushes air through the ventilator, with a flow valve adjusting pressure to meet
patient-specific parameters. When overpressure is released, the patient will exhale passively due to the lungs'
elasticity, the exhaled air being released usually through a one-way valve within the patient circuit called the patient
manifold. The oxygen content of the inspired gas can be set from 21 percent (ambient air) to 100 percent (pure
oxygen). Pressure and flow characteristics can be set mechanically or electronically.

Ventilators may also be equipped with monitoring and alarm systems for patient-related parameters (e.g. pressure,
volume, and flow) and ventilator function (e.g. air leakage, power failure, mechanical failure), backup batteries,
oxygen tanks, and remote control. The pneumatic system is nowadays often replaced by a computer-controlled

Modern ventilators are electronically controlled by a small embedded system to allow exact adaptation of pressure
and flow characteristics to an individual patient's needs. Fine-tuned ventilator settings also serve to make ventilation
more tolerable and comfortable for the patient. In Germany, Canada, and the United States, respiratory therapists are
responsible for tuning these settings while biomedical technologists are responsible for the maintenance.

The patient circuit usually consists of a set of three durable, yet lightweight plastic tubes, separated by function (e.g.
inhaled air, patient pressure, exhaled air). Determined by the type of ventilation needed, the patient-end of the circuit
may be either noninvasive or invasive.

Noninvasive methods, which are adequate for patients who require a ventilator only while sleeping and resting,
mainly employ a nasal mask. Invasive methods require intubation, which for long-term ventilator dependence will
normally be a tracheotomy cannula, as this is much more comfortable and practical for long-term care than is larynx
or nasal intubation.

Medical ventilator 2

Life-critical system
Because the failure of a mechanical ventilation system may result in death, it is classed as a life-critical system, and
precautions must be taken to ensure that mechanical ventilation systems are highly reliable. This includes their
power-supply provision.

Mechanical ventilators are therefore carefully designed so that no single point of failure can endanger the patient.
They usually have manual backup mechanisms to enable hand-driven respiration in the absence of power. Some
systems are also equipped with compressed-gas tanks and backup batteries to provide ventilation in case of power
failure or defective gas supplies, and methods to operate or call for help if their mechanisms or software fail.

Ventilator history
The early history of mechanical ventilation begins with various versions of what was eventually called the iron lung,
a form of noninvasive negative pressure ventilator widely used during the polio epidemics of the 20th century after
the introduction of the "Drinker respirator" in 1928, and the subsequent improvements introduced by John Haven
Emerson in 1931.[1] Other forms of noninvasive ventilators, also used widely for polio patients, include Biphasic
Cuirass Ventilation, the rocking bed, and rather primitive positive pressure machines.[1]

In 1949, John Haven Emerson developed a mechanical assister for anesthesia with the cooperation of the anesthesia
department at Harvard University. Mechanical ventilators began to be used increasingly in anesthesia and intensive
care during the 1950s. Their development was stimulated both by the need to treat polio patients and the increasing
use of muscle relaxants during anesthesia. Relaxant drugs paralyze the patient and improve operating conditions for
the surgeon, but also paralyze the respiratory muscles and stop breathing.

In the United Kingdom, the East Radcliffe and Beaver models were early examples, the later using an automotive
wiper motor to drive the bellows used to inflate the lungs.[2] Electric motors were, however, a problem in the
operating theatres of that time, as their use caused an explosion hazard in the presence of flammable anesthetics such
as ether and cyclopropane. In 1952, Roger Manley of the Westminster Hospital, London, developed a ventilator
which was entirely gas driven, and became the most popular model used in Europe. It was an elegant design, and
became a great favourite with European anesthetists for four decades, prior to the introduction of models controlled
by electronics. It was independent of electrical power, and caused no explosion hazard. The original Mark I unit was
developed to become the Manley Mark II in collaboration with the Blease company, who manufactured many
thousands of these units. Its principle of operation was very simple, an incoming gas flow was used to lift a weighted
bellows unit, which fell intermittently under gravity, forcing breathing gases into the patient's lungs. The inflation
pressure could be varied by sliding the movable weight on top of the bellows. The volume of gas delivered was
adjustable using a curved slider, which restricted bellows excursion. Residual pressure after the completion of
expiration was also configurable, using a small weighted arm visible to the lower right of the front panel. This was a
robust unit and its availability encouraged the introduction of positive pressure ventilation techniques into
mainstream European anesthetic practice.

The 1955 release of Forrest Bird's "Bird Universal Medical Respirator" in the United States, changed the way
mechanical ventilation was performed with the small green box becoming a familiar piece of medical equipment.[3]

The unit was sold as the Bird Mark 7 Respirator and informally called the "Bird". It was a pneumatic device and
therefore required no electrical power source to operate.

Intensive care environments around the world revolutionalized in 1971 by the introduction of the first SERVO 900
ventilator (Elema-Schönander). It was a small, silent and effective electronic ventilator, with the famous SERVO
feedback system controlling what had been set and regulating delivery. For the first time, the machine could deliver
the set volume in volume control ventilation.

Ventilators used under increased pressure (hyperbaric) require special precautions and few ventilators can operate
under these conditions.[4] In 1979, Sechrist Industries introduced their Model 500A ventilator which was specifically

Medical ventilator 3

designed for use with hyperbaric chambers.[5]

In 1991 the SERVO 300 ventilator series was introduced. The platform of the SERVO 300 series enabled treatment
of all patient categories, from adult to neonate, with one single ventilator. The SERVO 300 series provided a
completely new and unique gas delivery system, with rapid flow-triggering response.

A modular concept, meaning that the hospital has one ventilator model throughout the ICU department instead of a
fleet with different models and brands for the different user needs, was introduced with SERVO-i in 2001. With this
modular concept the ICU departments could choose the modes and options, software and hardware needed for a
particular patient category.

High frequency percussive ventilation
High-frequency percussive ventilation (HFPV) began to be used in selected centres in the 1980s. It is a hybrid of
conventional mechanical ventilation and high-frequency oscillatory ventilation. It has been used to salvage patients
with persistent hypoxemia when on conventional mechanical ventilation or, in some cases, used as a primary
modality of ventilatory support from the start.[6] [7]

See also
• Mechanical ventilation

External links
• Simulation of an anesthesia machine with a piston ventilator [8]

• International Ventilator Users Network [9] (IVUN), a subsidiary of Post-Polio Health International. Information
about home mechanical ventilation.

• Information about SERVO ventilation [10]

[1] Geddes LA (2007). "The history of artificial respiration". IEEE Engineering in Medicine and Biology Magazine : the Quarterly Magazine of

the Engineering in Medicine & Biology Society 26 (6): 38–41. doi:10.1109/EMB.2007.907081. PMID 18189086.
[2] Russell WR, Schuster E, Smith AC, Spalding JM (April 1956). "Radcliffe respiration pumps". The Lancet 270 (6922): 539–41.

PMID 13320798.
[3] Bellis, Mary. "Forrest Bird invented a fluid control device, respirator & pediatric ventilator" (http:/ / inventors. about. com/ od/

bstartinventors/ a/ Forrest_Bird. htm). . Retrieved 2009-06-04.
[4] Skinner, M (1998). "Ventilator function under hyperbaric conditions" (http:/ / archive. rubicon-foundation. org/ 5927). South Pacific

Underwater Medicine Society Journal 28 (2). . Retrieved 2009-06-04.
[5] Weaver LK, Greenway L, Elliot CG (1988). "Performance of the Seachrist 500A Hyperbaric Ventilator in a Monoplace Hyperbaric

Chamber" (http:/ / archive. rubicon-foundation. org/ 4377). Journal of Hyperbaric Medicine 3 (4): 215–225. . Retrieved 2009-06-04.
[6] Eastman A, Holland D, Higgins J, Smith B, Delagarza J, Olson C, Brakenridge S, Foteh K, Friese R (August 2006). "High-frequency

percussive ventilation improves oxygenation in trauma patients with acute respiratory distress syndrome: a retrospective review" (http:/ /
linkinghub. elsevier. com/ retrieve/ pii/ S0002-9610(06)00052-3). American Journal of Surgery 192 (2): 191–5.
doi:10.1016/j.amjsurg.2006.01.021. PMID 16860628. . Retrieved 2009-06-04.

[7] Rimensberger PC (October 2003). "ICU cornerstone: high frequency ventilation is here to stay" (http:/ / ccforum. com/ content/ 7/ 5/ 342).
Critical Care (London, England) 7 (5): 342–4. doi:10.1186/cc2327. PMID 12974963. PMC 270713. . Retrieved 2009-06-04.

[8] http:/ / www. simanest. org/ vfgs3. html
[9] http:/ / www. ventusers. org
[10] http:/ / www. criticalcarenews. com

Article Sources and Contributors 4

Article Sources and Contributors
Medical ventilator  Source:  Contributors: 16@r, Aitias, AnakngAraw, Arfgab, Artemis-Arethusa, Ayecee, Bdiscoe, Bertrand Bellet,
Braney, Chatbur, Darklilac, Erich gasboy, G716, GSchjetne, Gene Hobbs, Gene Nygaard, Hallbrianh, Hmwith, Hooperbloob, Iamreddave, JamesBWatson, Jfdwolff, Karada, Kartano,
Kosebamse, Lightmouse, MAQUET Critical Care, Medmantis, Mhaitham.shammaa, Michael Devore, MichaelMaggs, Mintleaf, Niels Olson, P199, Parryglitter, Peck10, Piano non troppo,
Posidonious, RadXman, Rama, Rcej, Sahlan73, Serpent's Choice, Sharkface217, Stephan Leeds, Steve2005, Stevenfruitsmaak, VK35, Ventilator63, WAS 4.250, WriterHound, 65 anonymous

Image Sources, Licenses and Contributors
Image:VIP Bird2.jpg  Source:  License: Public Domain  Contributors: Brian Hall

Creative Commons Attribution-Share Alike 3.0 Unported
http:/ / creativecommons. org/ licenses/ by-sa/ 3. 0/

Medical Instruments in the Developing World Malkin

2.2 Ventilators

2.2.1 Clinical Use and Principles of Operation

Many patients in an intensive care and the operating room require the mechanical ventilation of
their lungs. All thoracic surgery patients, for example, require mechanical ventilation. Some
patients simply need assistance breathing, when a patient is recovering from certain illnesses and
operations for example. In any case, ventilators can take over the major effort of respiration for
the patient.

Some people use the term ventilator and respirator interchangeable. They are not the same. A
respirator is a device that supplies or filters air in a harsh environment. The patient is breathing
on their own when they use a respirator. In most cases, without the ventilator, the patient could
not breathe, or would have great difficulty breathing.

Basic Elements of a Ventilator

A ventilator may include a pump which creates pressured air for delivery to the patient. However, in most
cases, compressed gases are connected to the machine. The compressed gas is at a very high pressure,
so a pressure regulator is typically connected to the bottle or the ventilator or both (see bottled gases
chapter for more details). There are generally moisture traps and particulate filters in line with the
incoming gases. The figure below details most of the common components and controls. However, there
is considerable variation between manufacturers.

Ventilators are complex devices. In many cases, the only repairs possible in the field are user error, filters
and rain out.

Some ventilators can accept air, oxygen or a combination of both. Some will measure the
concentration of oxygen delivered to the patient, sounding an alarm if it becomes too high or

Very old ventilators will deliver the pressurized gas directly to the patient. However, this is very rare,
even in the developing world. More common is for the ventilator to measure the volume (usually
derived from measured flow) and pressure of the delivered gases. A computer then controls the
timing and pressure for the next cycle.

Equipment found in the OR, ICU and ER

All ventilators must insure that the patient does not re-breath his own, untreated expired gases,
as they will eventually become excessively concentrated in carbon dioxide. So, in most cases,
the simple volume limited ventilator contains a “non-rebreathing” valve that opens to allow fresh
gas into the cylinder, closes during inflation and opens to allow expiration of the gases from the
lungs into the room or a waste collection canister. In most modern ventilators, the non-
rebreathing valve is in the tubing set (or circuit), in which case it is disposable.

The non-rebreathing valve may have a separate tube connected to the ventilator to force the
valve open and closed. Or, the non-rebreathing valve may operate on the pressure of the
inspiratory gas. In either case, it operates as a one-way valve that allows air to flow from the
inspiratory tube to the patient, but when the patient is expiring gas, blocks the inspiratory tube,
allowing the expired gas to pass through a separate expiratory tube.

Most ventilators will include humidification. Bottled gases delivered from cylinders are too dry for
the human body to moisturize comfortably. Sterile water should be used for humidification, but
often isn’t in the developing world. The water is heated and the vapor drawn into the gas flow to
the patient. In some cases, ultrasound is used to nebulize the water.

Most ventilators have an arm that the patient circuit tubing is attached to. This takes the weight
off of the tubing where it connects to the patient. Most of the tubing fittings are also specific
sizes to make misconnection harder. On adult machines the patient connector at the machine is
22 mm and the patient end of the tubing has a 15 mm connector. These connections are often
missing or manipulated in the developing world to allow for the use of mismatched tubing.

Some ventilators have the ability to heat the tubing or the delivered air or both. This can prevent
“rain-out” of the vapor in the gases being delivered to the patient. On some older systems you
still may find water traps where the “rain-out” collects in the tubing.

Modes of Ventilation

There are many different types or modes of ventilation. Most ventilators can switch between
several modes, but not all. The selection of the ventilator is ideally dependent on the patient’s
condition, but is often dictated by availability in the developing world. In fact, ventilation is so
critical that availability of the appropriate ventilator or ventilator mode often dictates what
procedures can and cannot be conducted in a given hospital.

There are three basic modes of ventilation, volume limited, pressure limited and timed cycle.
Timed cycle is a combination of the other two basic modes. Jet ventilation is a fundamentally
different mode of ventilation, but it is rarely seen in the developing world.

In the volume limited mode a preset volume of gas is delivered to the patient regardless of the
pressure reached in the lungs or the time required to complete the inflation. This is a simple
system where a gas is drawn into a cylinder and then forced out of the cylinder and into the
lungs. It is rarely used by itself in humans because of the lack of pressure sensitivity.

In a simple volume limited ventilator, the cylinder is adjusted for the volume of gas desired. The
motor is rate adjustable, generally between 5 and 50 breaths per minute (respiration rate). The
drive mechanism is a cam that creates a rapid inflation of the lungs and allows for a longer period
of time for the deflation of the lungs.

Medical Instruments in the Developing World Malkin

In the pressure limited mode a pressure limit is set where gas will flow into the lungs until that
pressure is reached, regardless of the volume of gas delivered. This is a simple system where
pressurized gas is passed through a pressure regulator to the desired pressure, then a valve that
allows the gas to enter the patient. It is rarely used by itself in humans because of the lack of
volume sensitivity.

The simplest device typically used on humans is the timed cycle ventilator. This is the most
common mode because it combines both the volume and pressure limited methods of operation.

In the timed cycle mode the physician sets the respiration rate, the tidal volume (the volume of
gas to be delivered), the upper pressure limit, and the inspiratory/expiratory ratio. If the
pressure limit is not exceeded, then the device will deliver the desired volume of air, more or
less evenly during the entire inspiratory time. The inspiratory time is the total respiration time
(one over the respiration rate) times the inspiratory/expiratory ratio. For example, at a tidal
volume of 1 liter, a respiration rate of 20 breaths per minute (3 seconds per breath), and an
inspiratory/expiratory ratio of 0.5 (inspiratory half as long as expiratory), the total inspiratory
time would be 1.0 seconds. One liter of gas would be delivered in one second.

If the pressure limit was exceeded, then an alarm will flash. Gas is still delivered to the patient
when the pressure limit alarm is indicated. However, the pressure is not allowed to exceed the
specified limit. Therefore the tidal volume desired has probably not been reached.

The Jet-Frequency mode is a newer ventilation mode. It is rarely seen in the developing world.
This mode is mostly used on neonates. There is no inspiratory/expiratory ratio and no pressure
limits to be set. The basic principle is a constant series of small volume pulses of gas is supplied
to the patient.

Ventilation Control

There are several modes for controlling the ventilator. The basic modes are controlled and
assisted. However, again, the combination of the two is the most common in practice.

The simplest mode is the controlled ventilation mode. In this mode the patient makes no effort
to initiate respiratory effort. The ventilator delivers a set volume of gas at a set rate for as long
as needed. Some units have a “sigh” level where every so many breaths or minutes the machine
automatically provides the patient with a greater volume of gas.

In the assisted mode of ventilation, the patient will trigger the flow of gas by starting to inhale.
When the patient reaches a preset withdrawn volume or a preset negative pressure, the
ventilator will start the flow of gas into the lungs. The assisted mode is typically used while the
patient is being weaned from the ventilator.

The most common mode is a combination of the controlled and assisted modes. At first, the
patient is on a completely controlled ventilation mode. As the patient starts to recover they will
make efforts to breathe on their own. This is called “fighting the ventilator” and is an important
clinical milestone in the recovery of a patient. Once that milestone is reached, the staff will
switch the ventilator to the assist mode, and begin to wean the patient from the ventilator.

Weaning is accomplished by slowly increasing the amount of negative pressure or withdrawn
volume required to trigger the flow of gas. This weaning process can take from hours to months
depending upon the patient’s condition. If the patient fails to initiate a respiratory effort in a
certain number of seconds the machine will automatically switch back to controlled ventilation
mode, breathing for the patient until another respiratory effort is made by the patient.

Equipment found in the OR, ICU and ER

2.2.2 Common Problems

Ventilators are one of a small group of life support devices that if it fails death will occur unless
there is intervention by staff and a replacement device available. In addition, the lungs are a
very delicate tissue which can be easily destroyed by a poorly calibrated ventilator. With that
knowledge it is paramount that the ventilators are kept in top working condition.

However, the dangers posed by a lack of ventilation combined with the dangers posed by a
poorly calibrated ventilator places the developing world engineer in a very difficult position. On
the one hand, without specific training on the ventilator at hand, you may endanger the patient
by working on the device. On the other hand, with no substitute ventilator available, you will
surely jeopardize the patient if you do not work on the device.

The inside of the Bennet ventilator illustrates the complexity of the
device. Fortunately, the required repairs are typically simple. If they are not, repair in the field
may not be possible.

Fortunately, ventilators are very reliable devices. The most common problems are user error, the
power supply, filtration and the tubing. The most common problem with user error is that the
controls are not standardized between manufacturers and the manuals were either not supplied
with the donation or were supplied in a language that the hospital staff does not speak.

If the problem is related to the power supply to the ventilator or a simple mechanical problem
(such as the wheels, lid or tubing arm) repair is straightforward.

The most common problem with the tubing is that disposable tubing is being reused. The non-
rebreathing valve may break or the tubing may leak. Leaks can be fixed with epoxy or a silicon
sealant in most cases. The non-rebreathing valve cannot be repaired in general. However, it
may be possible to adapt the non-rebreathing valve from one leaking circuit to be used on
another circuit that doesn’t leak, but has a non-rebreathing problem.

If the problem is not one of the problems described above, it is probably better not to attempt to
fix the ventilator without specialized training. However, your decision should be made in careful
consultation with the physicians. Discuss what the risks are to the patient if you do not work on
the machine and what the risks are to the patient if you work on the machine, and it accidentally
over pressurizes or under-ventilates the patient. Ultimately the decision is the physician’s and
you must follow his instructions.

Medical Instruments in the Developing World Malkin

2.2.3 Suggested Minimal Testing
If your repair has been a simple mechanical fix or the power supply. Then you can release the
machine to the floor for use with only simple testing. The simple testing should consist of
measuring the breathing rate (it should be within a few breaths per minute of the setting over the
entire range) and measuring the inspiratory/expiratory ratio (it should be within approximately 20%
of the set ratio). Test the pressure limit by partially occluding the connection to the patient with
your hand. The pressure limit light should flash.

If the ventilator is likely to be used in an intensive care unit, then it will likely be used to wean
patients. In this case, check that the assisted mode is working. After conducting the simple tests,
you can connect the ventilator to yourself. Do this by gently placing the patient tube in your mouth
(being sure that you can easily remove it if there is a problem). In the assisted mode, as long as
you are breathing, the device will deliver gas only when you inhale. Then, remove the tube from
your mouth. The device should take over in a controlled breathing fashion. Place the tube back in
your mouth and breathe normally and the device should automatically return to assisted mode.

If your repair has been on the breathing circuit, then you only need to test the tubing and the non-
rebreathing valve. The tubing should be leak free (occlude one end and blow hard into the other end
with the tube submerged in water. There should be no bubbles. The non-rebreathing valve is a one-
way valve. If it does not have a connection to the ventilator, then you can check it by simply blowing
into the patient connection end and making sure that the air goes down the expiratory tube. Then
suck from the patient end and make sure the air is coming in from the inspiratory tubing. If the non-
rebreathing valve has a connection to the ventilator, then you will have to operate the ventilator.
Check that the gas is flowing down the correct tubing by occluding the other tubing by squeezing the
appropriate tubing and making sure that there is no change in the ability to deliver or collect air.

If your repair has been anything more than power supply, tubing or mechanical, then you must
complete more tests. Be sure to discuss your limited ability to test the machine with the physician and
the potential dangers to his patients before conducting any repairs beyond the power supply, tubing or
simple mechanical repairs. However, if you and the physician determine that you must attempt a
repair; complete at least two more tests before releasing the ventilator: the pressure limit and the
delivered volume. Both the volume and pressure are typically tested with dedicate equipment you will
likely not have. However, they can be approximated.

The pressure limit is adequately tested by connecting the patient tubing to a u-shaped bend of tubing
filled with water. The ventilator should push the far end of the column of water the height of the
pressure setting, and then indicate a pressure limit alarm. For example, if the pressure limit is set to
25 cm of water, then the top of the column of water away from the ventilator should be 25 cm of
water higher than the top of the column of water near to the ventilator. Test several settings of the
pressure limit. Discuss the accuracy of the limit test with the physician.

The volume can be approximated by connecting a balloon to the patient tubing. You must calibrate the
balloon to volume before you begin. The easiest way to do this is to fill the balloon with a known
volume of water. Make two marks on the balloon a fixed distance apart, indicating the volume next to
the mark. Repeat this procedure for several volumes. Now, when the balloon expands to the
indicated volume, the marks should be your set distance apart. To use your calibrated balloon, clamp
off the balloon at the end of the inspiratory cycle. Test several settings of the volume and discuss the
accuracy of the test with the physician.

* 2.*Diagrams*and*Schematics*of*Ventilators****Featured*in*this*Section:***Villarreal,/M./R./“Respiratory/System/Complete/En.”/Wikipedia'Commons./Posted/December/13,/2007./Retrieved/from:/ WHO./“Anesthetic/and/Resuscitation/Equipment.”/Maintenance'and'Repair'of'Laboratory,'Diagnostic'Imaging,'and'Hospital/Equipment'(WHO:/1996),/p./121Z134./// WHO./“Anaesthesia/Ventilator/From/the/publication:/“WHO/Technical/Specifications/for/61/Medical/Devices./WHO./Retrieved/from:/

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i Version No. 1ii Date of initial version 6/13/12iii Date of last modification 6/18/14iv Date of publicationv Done by WHO working group1 WHO Category / Code (under development)2 Generic name Anaesthesia ventilator3 Specific type or variation (optional) Alone or as a part of anesthesia machine4 GMDN name Anaesthesia ventilator5 GMDN code 348516 GMDN category 02 Anaesthetic and respiratory devices 7 UMDNS name Ventilators, Anesthesia8 UMDNS code 101459 UNSPS code (optional)10 Alternative name/s (optional) Ventilator; Anaesthesia unit ventilator; Anesthesia ventilator11 Alternative code/s (optional) MS 42251; S 10145; S 3632512 Keywords (optional) Anesthesia machines, Anesthesia Units, Acute Care, Respired/Anesthetic
13 GMDN/UMDNS definition (optional)

A mains electricity (AC-powered) stand-alone, automatic cycling device used to assist and control alveolar ventilation during general anaesthesia, and is compatible with inhaled anaesthetic agents. It has fewer functions and is less complex to operate than an intensive care ventilator, but adequately meets the patient's ventilation needs for oxygen (O2) and carbon dioxide (CO2) exchange to maintain normal blood gas concentrations. The device provides a mechanical means to deliver the breathing gas to the patient in a controlled pattern, and is equipped with alarms to warn of changes in respiration or the onset of unsafe operating conditions.
14 Clinical or other purpose Provides a mechanical means to deliver the breathing gas to the patient in a controlled pattern, and is equipped with alarms to warn of changes in respiration or the onset of unsafe operating conditions. Ventilators designed to use positive pressure to deliver a prescribed mixture of respiratory and anesthetic gases and vapors to the patient's lungs during surgical procedures that require general anesthesia15 Level of use (if relevant) District Hospital, Provincial Hospital, Specialized Hospital, General Hospital16 Clinical department/ward(if relevant) Surgery (Operating theatre, Operating room)17 Overview of functional requirements Dispenses a controlled mixture of anaesthetic agents (externally supplied), oxygen and air to the patient, gives artificial respiratory support as necessary, fully alarmed with all necessary monitors for continuous operation in operating theatre environment, includes compressor, nebulizer and humidifier, reusable, sterilizable patient masks and connectors, suitable for all ages and body weights of patient, provides port for linkage with ************* anaesthetic delivery system.




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Detailed requirements The unit must be able to measure O2 concentration, airway pressure, and the volume of expired gas. Trend display facility for at least the last 8 hours, with minimum 5 minutes resolutionAutomatic compliance and leakage compensation for circuit and tubes. Closed circuit system with possibility to work in open circuit.Externally supplied anaesthetic gas, oxygen and air mixture ratios fully controllable (mixing system selector for Air-O2 and N2O-O2 gasses mixture management) Expiratory block should be autoclavable and no routine calibration required.Should have the ability to calculate intrinsic PEEP Volume, occlusion pressure and inflection points. Circle breathing circuit to be included, with CO2 absorption chamberNebuliser to deliver particle size of < 3 micron and to be used in both offline and online modes.Automatic patient detection facility preferable. Minimum oxygen enrichment not lower than 25%.Inlet gas supply (O2 / N2O) pressure range at least 35 to 65 psi. Gas supply gauges required, with scales allowing easy reading. Gasses pressure system continuous control with accuracy of at least +/- 10%.At least four analog rotameters (two for oxygen, one for air and one for N2O) with programmed parameters visualization. Digital rotameters are not accepted.Rotameters flow rate range not smaller than 0.0 to 10.0 l/min and resolution at least of 0.2 l/min. Minute volume 2 to 25 L/minute. Tidal volume 20 to 1500ml. Respiratory rate 5 to 70 cycles/minute. Respiratory rate 5 to 70 cycles/minute. I/E ratio 2/1 to 1/4. Inspiration pressure 0 to 80mbar. Peak inspiratory flow 0 to 60 L/minute. Trigger sensitivity 0 to 20mbar. At least the following safety systems:a) oxygen-N2O gasses mixture guaranteed with not less than 25% of Oxygen;b) oxygen leakage or low pressure alarm with simultaneous stop of N2O gas delivery; c) adjustable Pressure Limiting (APL) valve to prevent from too high pressure gas delivering; d) compressed Air leakage or low pressure alarm with automatic passage of the units using air to the oxygen alimentation;e) system safety measure to prevent from the Air and N2O simultaneous delivery.Units should have a power-loss alarm, and the battery backup should have an automatic low-battery alarm. All units should include a backup battery to guard against power loss.


Displayed parameters Facility to measure and display on screen:a) 3 traces against time: pressure, volume and flowb) 3 two-axis displays: Pressure-Volume, Flow-Volume and Pressure-Flowc) Status indicators for ventilator mode, battery life, patient data, alarm settings, clock etc.d) Airway pressure (Peak and Mean).e) Tidal volume (Inspired and Expired).f) Minute volume (Inspired and Expired).g) I:E ratioh) inspiration and expiration timesi) Spontaneous Minute Volumej) Respiratory rate (spontaneous and mechanical)k) Total Frequency.l) Oxygen concentrationm) End tidal CO2 with capnographyn) FiO2 dynamic.o) Intrinsic PEEP and PEEPi Volume.p) Plateau Pressure.q) Resistance and Compliance. r) Blood pressure 20 User adjustable settings Units should have a power-loss alarm, and the battery backup should have an automatic low-battery alarmAlarms for all measured and monitored parameters, including circuit disconnection and gas failure.
21 Components(if relevant) External anaesthetic gas supply connection to be secure but easy to fit and releaseMovable arm holder for supporting patient breathing circuitWhole unit to be mounted on wheeled base, with brakes when in useScreen to be mounted flexibly to enable easy, ergonomic viewingIf O2 / N2O supplied by bottle, holders for bottles to include secure locking mechanismIf O2 / N2O supplied by bottle, bottles to have ******** type connector22 Mobility, portability(if relevant)23 Raw Materials(if relevant)

Electrical, water and/or gas supply (if relevant) Electrical source requirements: Amperage:______; Voltage:______. Power input to be ************* fitted with ********** compatible mains plug.Voltage corrector / stabilizer to allow operation at ± 30% of local rated voltage.Resettable overcurrent breaker required on both live and neutral supply lines.Voltage corrector / stabilizer to allow operation at ± 30% of local rated voltage.An internal battery capable of powering the unit for at least 30 minutes. Compliance with ____ electrical standards and regulations.


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Accessories (if relevant) Breathing circuits (two sets)Reusable masks (two sets each of small, medium and large), textured for easy fit.Filters sufficient for 100 patients’ use Rechargeable batteries with:a) autonomy of at least 1 hours;b) visual alarm in case of low battery;c) automatic passage from line alimentation to battery operating modes;d) system integrated battery charger.26 Sterilization process for accessories (if relevant)27 Consumables / reagents (if relevant)

Spare parts (if relevant) Medical units select them according to their needs, ensuring compatibility with the brand and model of the equipment. 1 reusable ECG sensors and connectors set.1 reusable adult and or pediatric oxygen saturation sensor and connector set.1 reusable adult and or pediatric invasive pressure transducer and connector set.1 reusable adult and or pediatric non-invasive pressure transducer and connector set.1 rectal temperature transducer and connector set.1 adult and or pediatric cardiac output connector set.1 CO2 sensor.29 Other components (if relevant) Some anesthesia units require stand-alone physiologic monitors (modular approach) and/or anesthetic agent monitors, while others have integrated monitors (preconfigured approach)

30 Sterility status on delivery (if relevant) N/A31 Shelf life (if relevant) N/A32 Transportation and storage (if relevant) N/A33 Labelling (if relevant) N/A
34 Context-dependent requirements Capable of being stored continuously in ambient temperature of 0 to 50 deg C and relative humidity of 15 to 90%.Capable of operating continuously in ambient temperature of 10 to 40 deg C and relative humidity of 15 to 90%.
35 Pre-installation requirements(if relevant)36 Requirements for commissioning (if relevant)37 Training of user/s (if relevant) Training of users in operation and basic maintenance shall be providedAdvanced maintenance tasks required shall be documentedSupplier to perform installation, safety and operation checks before handoverLocal clinical staff to affirm completion of installation.38 User care(if relevant) Casing to be splash proof and cleanable with alcohol or chlorine wipes39 Warranty Two year warranty should be provided by the supplier40 Maintenance tasks Advanced maintenance tasks required shall be documented41 Type of service contract Service contract is recommended in case no in-house service experience is avialable to ensure that preventive maintenance will be performed at regular intervals.Pricing for service contracts should be negotiated before the system is purchased.42 Spare parts availability post-warranty43 Software / Hardware upgrade availability Routine software updates should be provided
44 Documentation requirements User, technical and maintenance manuals to be supplied in ************** languageCertificate of calibration and inspection to be providedList to be provided of equipment and procedures required for local calibration and routine maintenanceList to be provided of important spares and accessories, with their part numbers and costContact details of manufacturer, supplier and local service agent to be provided
45 Estimated Life Span 8 to 10 Years





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46 Risk Classification Class C (GHTF Rule 11-1); Class II (USA); Class III (EU, Japan, Canada and Australia)47 Regulatory Approval / Certification


International standards ISO 13485:2003 Medical devices -- Quality management systems -- Requirements for regulatory purposes (Australia, Canada and EU)ISO 14971:2007 Medical devices -- Application of risk management to medical devices IEC 60601-1:2012 Medical electrical equipment - Part 1: General requirements for basic safety and essential performanceIEC 60601-1-1:2000 Medical electrical equipment - Part 1-1: General requirements for safety - Collateral standard: Safety requirements for medical electrical systemsIEC 60601-1-2:2007 Medical electrical equipment - Part 1-2: General requirements for basic safety and essential performance - Collateral standard: Electromagnetic compatibility - Requirements and tests ISO 4135:2001 Anaesthetic and respiratory equipment -- VocabularyISO 5356-1:2004 Anaesthetic and respiratory equipment -- Conical connectors -- Part 1: Cones and socketsISO 5356-2:2012 Anaesthetic and respiratory equipment -- Conical connectors -- Part 2: Screw-threaded weight-bearing connectorsISO 5358:1992 Anaesthetic machines for use with humansISO 5360:2012 Anaesthetic vaporizers -- Agent-specific filling systemsISO 5361:2012 Anaesthetic and respiratory equipment -- Tracheal tubes and connectorsISO 5362:2006 Anaesthetic reservoir bagsISO 5364:2008 Anaesthetic and respiratory equipment -- Oropharyngeal airwaysISO 5366-1:2000 Anaesthetic and respiratory equipment -- Tracheostomy tubes -- Part 1: Tubes and connectors for use in adultsSO 5366-3:2001 Anaesthetic and respiratory equipment -- Tracheostomy tubes -- Part 3: Paediatric tracheostomy tubesISO 5367:2000 Breathing tubes intended for use with anaesthetic apparatus and ventilatorsISO 7376:2009 Anaesthetic and respiratory equipment -- Laryngoscopes for tracheal intubationISO 7396-2:2007 Medical gas pipeline systems -- Part 2: Anaesthetic gas scavenging disposal systemsISO 8835-7:2011 Inhalational anaesthesia systems -- Part 7: Anaesthetic systems for use in areas with limited logistical supplies of electricity and anaesthetic gasesISO 9170-2:2008 Terminal units for medical gas pipeline systems -- Part 2: Terminal units for anaesthetic gas scavenging systemsISO 9360-1:2000 Anaesthetic and respiratory equipment -- Heat and moisture exchangers (HMEs) for humidifying respired gases in humans -- Part 1: HMEs for use with minimum tidal volumes of 250 ml


International standards ISO 9360-2:2001 Anaesthetic and respiratory equipment -- Heat and moisture exchangers (HMEs) for humidifying respired gases in humans -- Part 2: HMEs for use with tracheostomized patients having minimum tidal volumes of 250 mlISO 11197:2004 Medical supply unitsISO 11712:2009 Anaesthetic and respiratory equipment -- Supralaryngeal airways and connectorsISO 15001:2010 Anaesthetic and respiratory equipment -- Compatibility with oxygenISO 10524-1:2006 Pressure regulators for use with medical gases -- Part 1: Pressure regulators and pressure regulators with flow-metering devicesISO/TS 18835:2004 Inhalational anaesthesia systems -- Draw-over vaporizers and associated equipmentISO 21969:2009 High-pressure flexible connections for use with medical gas systemsISO 23328-1:2003 Breathing system filters for anaesthetic and respiratory use -- Part 1: Salt test method to assess filtration performanceISO 23328-2:2002 Breathing system filters for anaesthetic and respiratory use -- Part 2: Non-filtration aspectsISO 23747:2007 Anaesthetic and respiratory equipment -- Peak expiratory flow meters for the assessment of pulmonary function in spontaneously breathing humansISO 26782:2009 Anaesthetic and respiratory equipment -- Spirometers intended for the measurement of time forced expired volumes in humansISO 26825:2008 Anaesthetic and respiratory equipment -- User-applied labels for syringes containing drugs used during anaesthesia -- Colours, design and performanceISO 27427:2010 Anaesthetic and respiratory equipment -- Nebulizing systems and componentsISO 80601-2-12:2011 Medical electrical equipment -- Part 2-12: Particular requirements for basic safety and essential performance of critical care ventilatorsISO 80601-2-13:2011 Medical electrical equipment -- Part 2-13: Particular requirements for basic safety and essential performance of an anaesthetic workstationISO 80601-2-55:2011 Medical electrical equipment -- Part 2-55: Particular requirements for the basic safety and essential performance of respiratory gas monitors


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Reginal / Local Standards ASTM F1101-90(1996) Standard Specification for Ventilators Intended for Use During AnesthesiaASTM F1208-89(2005) Standard Specification for Minimum Performance and Safety Requirements for Anesthesia Breathing SystemsASTM F1850-00(2005) Standard Specification for Particular Requirements for Anesthesia Workstations and Their ComponentsASTM F2002-01 Standard Terminology Relating to Anesthesia and Respiratory EquipmentJIS T 7201-1:1999 Inhalational anaesthesia systems -- Part 1 Anaesthetic machines for use with humans JIS T 7201-2-1:1999 Inhalational anaesthesia systems -- Anaesthetic and respiratory equipment -- Conical connectors -- Part 2-1 Cones and sockets JIS T 7201-2-2:1999 Inhalational anaesthesia systems -- Anaesthetic and respiratory equipment -- Conical connectors -- Part 2-2: Screw-threaded weight-bearing connectors JIS T 7201-3:2005 Anaesthetic reservoir bags JIS T 7201-4:2005 Breathing tubes intended for use with anaesthetic apparatus and ventilators JIS T 7201-5:1999 Inhalational anaesthesia systems -- Part 5: Anaesthetic circle breathing systems JIS T 7211:2005 Breathing system filters for anaesthetic and respiratory use -- Part 1: Salt test method to assess filtration performance JIS T 7212:2005 Breathing system filters for anaesthetic and respiratory use -- Part 2: Non-filtration aspects

50 Regulations US regulations 21 CFR part 820 21CFR section 868.5160 gas-machine, anesthesia JP regulations MHLW Ordinance No.169 34851000 Anaesthesia ventilator (Japan)

// / 3.*Preventative*Maintenance*of*Ventilators****Featured*in*this*Section:*****Developing/World/Healthcare/Technology/(DHT)/Laboratory./“Ventilator:/How/to/Calibrate.”/Biomedical'Technician'Assistant'(BTA)'Skills/(DHT/Lab:/2011).///Engineering/World/Health./“VentilatorsZSafety/&/Performance/Checklist./Engineering'World'Health.///Strengthening/Specialised/Clinical/Services/in/the/Pacific./User'Care'of'Medical'Equipment:'A'first'line'maintenance'guide'for'end'users./(2015)./ * *

User Care of Medical Equipment – First line maintenance for end users


User Care Checklist – Anaesthesia Machines and Ventilators



9 Remove any dust, dirt, water, waste matter, tape and paper


9 If any leak is audible, check with soapy solution

9 Check all seals, connectors, adapters and parts are tight

9 Check all moving parts move freely, all holes are unblocked


9 Report any faults to technician immediately

9 After checks, depressurize system and replace all caps / covers



9 Clean inside and outside with damp cloth and dry off

9 Remove dirt from wheels/any moving parts


9 Check connections for leakage with soap solution and dry off

9 Check all fittings and valves for proper assembly

9 Replace soda lime if it has changed colour

9 Replace any deteriorated hoses and tubing

9 If seal, plug, cable or socket are damaged, replace


9 When next used, check pressure gauges rise

9 When next used, check there are no leaks

Every six months
Biomedical Technician check required

Knowledge Domain: Mechanical
Unit: Calibration
Skill: Ventilator

Tools and Parts Required:

1) Large jug
2) Transparent rubber tube, at

least 40 cm in length
3) Rubber or latex glove
4) Balloon
5) Syringe, largest available
6) String, at least 1 m

7) Tape measure or ruler
8) Marker
9) Watch
10) Pen or pencil
11) Graduated cylinder (1L)
12) Large tub

A ventilator is a machine used to assist patients in breathing. A ventilator can breathe
for patients entirely. A ventilator may include a pump or compressed gases to provide
gas to the patient. There are three basic modes of ventilation: volume limited, pressure
limited, and timed cycle.
x Volume limited ventilation delivers a predetermined volume of gas to the patient.
x Pressure limited ventilation delivers gas until a predetermined pressure is

reached in the lungs.
x Timed cycle ventilation delivers gas based on a predetermined volume, pressure,

respiration rate, and inspiratory/expiratory ratio. In timed cycle ventilation, the
predetermined volume is delivered at the respiration rate as long as the
predetermined pressure is not exceeded.

A ventilator uses a non-rebreathing valve to prevent the patient from breathing his own
expired gas. This valve opens when the patient expires gas.

Ventilators are complicated machines. They may include computer screens. You usually
need the manual to operate the ventilator, even for calibration. Below are two different

Identification and Diagnosis
Calibration of ventilators does not require diagnosis. Calibrate each ventilator every 6
months as part of your planned preventative maintenance.

Before a ventilator is placed into service, it should be calibrated to insure patient safety.
Three outputs must be calibrated: pressure, volume, and flow.

Pressure Calibration
1. Construct a manometer to measure pressure in centimeters of H2O.

a. Use a large non-inflatable jug as the reservoir. Most water jugs will work.
b. Fill the jug half-full with water.
c. Insert the patient output from the ventilator into the plastic jug. Also insert one

end of the clear plastic tubing into the plastic jug. The end of the plastic tube
should be near the bottom.

d. Seal the tubes with latex gloves and tape. Insure that no air can escape from
the jug opening.

2. Set the pressure limit on the ventilator. Record this pressure in Table 1 below.

3. Hold the clear plastic tubing straight up. Use a tape measure to measure the peak
height of the water in cm H2O. Measure from the water level in the jug to the
maximum height reached in the clear plastic tubing. Record this measurement in
Table 1 below. The height of the water is the pressure.

Patient output 
(from ventilator)

Clear plastic tubing 
(for measurement)

4. Repeat Steps 2-3 for four settings of pressure.

5. To determine if the ventilator is accurate enough, show your table to the physician
that uses the ventilator.

Set Pressure (Step 2) Measured Pressure (Step 3)

Table 1: Pressure Calibration

Volume Calibration
1. Insure that the ventilator’s patient output tube is at least 80cm long. If the output tube

is too short, change the tube to a longer one.

2. Set the ventilator to 500 mL. 500 mL is the average volume of a breath in adults.

measurement at 
water level in 
the jug 

Hold the clear 
plastic tubing 

3. Fill a plastic tube with water. The tub should be big enough to comfortable fit a 1 liter
graduated cylinder

4. Fill a 1 liter graduated cylinder entirely with water. Insure there are no air bubbles.
Set the graduated cylinder upside down in the container.

5. Place the patient output tube inside the graduated cylinder.

6. Turn on the ventilator. Allow the ventilator to deliver one breath. The top of the
graduated cylinder should fill with air. Turn off the ventilator. Read the water level on
the graduated cylinder. Record this value in Table 2 below.


7. Repeat Steps 1-6 to complete the table. You should measure three trials for three
different volumes.

8. To determine if the ventilator is sufficiently accurate and precise, show your table to
the physician that uses the ventilator.


Set Volume
(Step 1)

Measured Volume
(Step 6)

400 ml

400 ml

400 ml

500 ml

500 ml

500 ml

600 ml

600 ml

600 ml

Table 2: Volume Calibration

Flow Calibration
1. Set the ventilator to deliver a constant volume per breath. Set the ventilator to deliver

the number of breaths per minute you wish to test. Record the number of breaths in
Table 3 below.

2. Attach a latex glove to the output of the ventilator so each breath is visible. Measure
the number of breaths that occur in one minute using a watch. Record the number of
breaths that occur in one minute in Table 3 below.

3. Repeat Steps 1-2 for four total settings of breaths per minute.

4. To determine if the ventilator is accurate enough, show your table to the physician
that uses the ventilator.

Desired Breaths Per Minute
(Step 1)

Measured Breaths Per Minute
(Step 2)

Table 3: Flow Calibration

Your instructor will give you a ventilator. Calibrate the ventilator in all available modes of
ventilation. Your instructor must verify your work before you continue.

Proper calibration of ventilators is crucial. Proper calibration involves repeated
measurements. Ventilators are critical pieces of medical equipment. The wrong
pressure, volume or flow could result in death.

Preventative Maintenance and Calibration
Do not use a ventilator if it does not pass the calibration procedure. Common problems
are caused by cracks or leaks in the tubing. The non-rebreathing valve can also be a
source of failure. Check for cracks, leaks, or a loose connection of the non-rebreathing

Ventilators- Safety & Performance Checklist Physical)Integrity)["""]"Good"["""]"Poor"or"["""]"Do"Not"Use.""["""]"Check"Earth"Resistance"(ohms)"_____"=<".50"Ohms"["""]"Leakage"Current"Tests."Chassis"Leakage"_____"(=<"300"micro"amps)""Monitors)and)Alarms."""The"following"parameters"are"commonly"monitored"and"should"be"inspected"for"accuracy"(generally"within"10%)"according"to"the"manufacturer’s"specifications:"["""]"Breathing"rate"________"["""]"Inspiratory"time"_______"["""]"Peak"inspiratory"pressure"(PIP)"_______"["""]"Peak"or"mean"inspiratory"flow"_______"["""]"PEEP"_______"["""]"Mean"airway"pressure"(MAP)"_______"["""]"Volume"(both"tidal"and"minute"volume)"______"["""]"Fraction"of"inspired"oxygen"(FIO2)"_____"["""]"Temperature"of"inspired"air"______""

*4.*Troubleshooting*and*Repair*of*Ventilators****Featured*in*this*Section:*****Strengthening/Specialised/Clinical/Services/in/the/Pacific./User'Care'of'Medical'Equipment:'A'first'line'maintenance'guide'for'end'users./(2015)./ *///////////** *******

User Care of Medical Equipment – First line maintenance for end users


Troubleshooting – Anaesthesia Machines and Ventilators

Fault Possible Cause Solution


Equipment is not running

No power at mains socket

Electrical cable fault

Check power switch is on.
Replace fuse with correct voltage
and current rating if blown.
Check mains power is present at
socket using equipment known to
be working. Contact electrician
for rewiring if power not present.

Refer to electrician for repair


No gas output

No O2 pressure in cylinder / gas

Check pressure gauges for gas
pressure (about 4 bar or 4 kg/cm2)

Restore gas supply or replace gas

Replace O2 cylinder and/or N2O
cylinder in case of low pressure.


O2 failure, power failure or
breathing alarm not working

Alarm battery is low.

Alarm device is not working

Call biomedical technician to fix
the problem.


Machine has leaks

Poor seal
(commonly occurring around
tubing connections, flow valves
and O2 / N2O yokes)

Cylinders not seated in yokes

Clean leaking seal or gasket,
replace if broken. If leaks remain,
call technician for repair.

Refit cylinders in yokes and
retest. If leaks remain, call
technician for repair.


Flowmeter fault

Over tightening of the needle
valve or sticking of the float / ball

Refer to biomedical technician


Electrical shocks

Wiring fault

Refer to electrician immediately

5.*Resources*for*More*Information*about*Ventilators***Featured*in*this*Section:****/WHO./“Routine/Maintenance/Models.”/From/the/publication:/Maintenance'and'Repair'of'Laboratory,'Diagnostic'Imaging,'and'Hospital/Equipment'(WHO:/1996).////WHO./“Fault/Diagnosis/and/Repair/Modules.”/From/the/publication:/Maintenance'and'Repair'of'Laboratory,'Diagnostic'Imaging,'and'Hospital/Equipment'(WHO:/1996).///// /**////* *//////

Resources*for*More*Information:/*/*Internal*Resources*at**For*more*information*about*maintenance*and*repair*of*ventilators*and*the*use*of*ventilators*in*anesthesia*systems*please*see*these*resources*in*the*BMET*Library!*/// 1. Stanco,/Cassandra/ed./for/Engineering/World/Health./“Anesthesia/Machine/Packet.”/Engineering'World'Health,/2015.//// 2. WHO./“Anesthetic/and/Resuscitation/Equipment.”/Maintenance'and'Repair'of'Laboratory,'Diagnostic'Imaging,'and'Hospital/Equipment'(WHO:/1996),/p./121Z134./*/

Ventilator*Bibliography:////Engineering/World/Health./“VentilatorsZSafety/&/Performance/Checklist./Engineering'World'Health.///Malkin,/Robert./“2.2/Ventilators.”/Medical'Instrumentation'in'the'Developing'World./Engineering/World/Health,/2006./// /Strengthening/Specialised/Clinical/Services/in/the/Pacific./User'Care'of'Medical'Equipment:'A'first'line'maintenance'guide'for'end'users./(2015).///WHO./“Anaesthesia/Ventilator/From/the/publication:/“WHO/Technical/Specifications/for/61/Medical/Devices./WHO./Retrieved/from:/“Anesthetic/and/Resuscitation/Equipment.”/Maintenance'and'Repair'of'Laboratory,'Diagnostic'Imaging,'and'Hospital/Equipment'(WHO:/1996),/p./121Z134.///WHO./“Ventilator,/Intensive/Care.”/From/the/publication:/“WHO/Technical/Specifications/for/61/Medical/Devices./WHO./Retrieved/from:/“/Medical/Ventilator.”/Wikipedia,/pp./1Z17./Retrieved/from:/,/M./R./“Respiratory/System/Complete/En.”/Wikipedia'Commons./Posted/December/13,/2007./Retrieved/from:/ ****

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