Descripción elemental y funcional de los Ventiladores Pulmonares.

1. Ventilators
WHO. “Ventilator, Intensive Care, Neonatal/Pediatric.” From the publication: “WHO Technical Specifications for 61 Medical Devices.
WHO. Retrieved from: http://www.who.int/medical_devices/management_use/mde_tech_spec/en/

2. Summary
• Respiration System
Anatomy
• Respiratory Control
• Clinical Use
• Specifications
• History
• Principles of Operation
• Variables
• Operation Modes
• Block Diagram
• Commercial Examples
• Patient’s Safety
• Preventive
Maintenance
• Common Problems
• Test Procedures
• Artificial Lung

3. Respiration System
Anatomy
Sunshineconnelly at English Wikibooks [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

4. Respiration System Anatomy
National Heart Lung and Blood Institute (National Heart Lung and Blood Institute) [Public domain], via Wikimedia Commons

5. Respiration System
Anatomy
3D Yoga (2008), View of diaphragm during respiration [video]. Retrieved from https://www.youtube.com/watch?v=hp-gCvW8PRY

6. • The amount of air flowing into and out of
the lungs with each breath is called the tidal
volume (TV).
• Typical adult = 500 mL (quiet breathing)
• Possible to inhale a volume 7 x TV
Respiration System
Anatomy

7. Respiration Volumes
Kapwatt (2014), Output of a spirometer [image]. Retrieved from https://en.wikipedia.org/wiki/File:Lungvolumes_Updated.png

8. O2 saturation vs PO2
Ratznium at English Wikipedia
Later versions were uploaded by
Aaronsharpe at en.wikipedia.
(Transferred from en.wikipedia to
Commons.) [Public domain], via
Wikimedia Commons

9. Respiratory Failure
• Lungs, or the heart and lungs, are not able to
sufficiently oxygenate the blood and body tissue.
• Often, the ability to excrete CO2 is also impaired.
• Examples
– Apnea
– Tuberculoses
– Pneumonia
– Edema
PaO2 (partial pressure ) < 50 mm Hg
PaCO2 > 50 - 60 mm Hg

10. Respiratory Control
Brain
Nerves
Bellows
AirwaysAlveoli
It only requires one disrupted
“link” to cause respiratory failure !
Patrick J Lynch (2006), Lungs [drawing]. Retrieved from https://en.wikipedia.org/wiki/Lung#/media/File:Lungs_diagram_detailed.svg

11. Respiratory Control
CHEMORECEPTORS BARORECEPTORS INFLATION RECEPTORS
PROPIROCEPTORS IRRITATION
ARTERIAL
BLOOD
RESPIRATORY
MUSCLES
MEDULLARY AND
PONS
RESPIRATORY
CENTERS
CEREBRAL
CORTEX, LIMBIC
SYSTEM,
HYPOTHALMUS
Virginia Reid (2016), Respiratory Control [drawing]. Adapted from previous image (unknown)

12. Respiratory Control
During exercise:
– Respiration rate increases
– Inhalation time is faster than exhalation time
– Respiratory flow wave shapes become more
trapezoidal
– Expiratory reserve volume decreases.

13. Ventilator Clinical Use
• When should a patient be ventilated:
– Lung injury and respiratory failures
– All thoracic surgery cases

14. Effects of Major Surgery & Anesthesia
• Respiratory Center in Brain
– Narcotic drugs
• Neuromuscular Connections
– Paralyzing agents
• Thoracic Bellows
(rib cage and diaphragm)
Chest or abdominal incision
WHO. “Ventilator, Intensive Care.” From the publication: “WHO Technical Specifications for 61 Medical Devices. WHO. Retrieved from:
http://www.who.int/medical_devices/management_use/mde_tech_spec/en/
Ventilator Clinical Use

15. Effects of Major Surgery & Anesthesia
• Airways (upper & lower)
– Dry, irritating gases
• Lungs
(bronchioles, alveoli and capillaries)
– Pain, and ineffective cough
Ventilator Clinical Use

16. Respirator vs Ventilator
• Respirator is a device that supplies or filters
air in a harsh environment
By John Dimos and Paul Satti [Public domain], via Wikimedia
Commons, retrieved from
https://commons.wikimedia.org/wiki/File:Air-
Purifying_Respirator.jpg

17. • Input/ Output :
– Atmosphere air or/and
– Oxygen or/and
– Nitrogen
Specifications

18. Mechanical Ventilators
History
• Negative-pressure ventilators (“iron lungs”)
• Non-invasive ventilation first used in Boston
Children’s Hospital in 1928
• Used extensively during polio outbreaks in
1940s – 1950s

19. History
Problems
• Venous blood pool in the
abdomen (reducing
cardiac output)
• Less accessible for
patient care and
monitoring
• Difficult synchronization
with patient’s effort
Negative-pressure ventilators
Photo Credit: Content Providers(s): CDC [Public domain], via Wikimedia Commons, retrieved from https://commons.wikimedia.org/wiki/File:Poumon_artificiel.jpg

20. History
Positive-pressure ventilators
• Invasive ventilation first used at
Massachusetts General Hospital in
1955
• Now the modern standard of
mechanical ventilation
Allows treatment of patients with high
lung resistance and low compliance
Average of 833 patient days of
mechanical ventilation per hospitals
per year in USA.

21. Principles of Operation
National Heart Lung and Blood Institute (NIH) (National Heart Lung and Blood Institute (NIH)) [Public domain],
via Wikimedia Commons. Retrieved from https://commons.wikimedia.org/wiki/File:Ventilators.jpg

22. Principles of Operation
Malkin, Robert. “2.2 Ventilators.” Medical Instrumentation in the Developing World. Engineering World Health, 2006.

23. Wiley - Encyclopedia of Biomedical
Engineering - 6 Vol. Set - RESPIRATION
MEASUREMENTS
Pressure
Principles of Operation

24. Input Variables
• Modes of Ventilation
• Output
– Exponential
– Ramp
– Rectangular
– Sinusoidal
• Alarm Systems
• Frequency
• Volume
• Flow
• Pressures Malkin, Robert. “2.2 Ventilators.” Medical
Instrumentation in the Developing World.
Engineering World Health, 2006.

25. Operation Modes
• Mandatory Ventilation
– Volume controlled (limited) ventilation
– Pressure controlled ventilation
– Timed cycle (combination of volume and pressure)
• Spontaneous Ventilation (Assisted Mode)
(still controlling the breath rate, flow rate, and the
tidal volume)
– Continuous Positive Airway Pressure (CPAP)
– Pressure Support

26. Operation Modes
Pressure regulated volume control
By Eduardo Mireles-Cabodevila, MD (The Cleveland Clinic Foundation) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia
Commons. Retrieved form https://commons.wikimedia.org/wiki/File:Pressure_regulated_volume_control_graphic.jpg

27. Operation Modes
Spontaneous Ventilation
– Continuous Positive Airway Pressure (CPAP)
L. Droll (2005), Cpap cycle [image]. Retrieved
from
https://commons.wikimedia.org/wiki/File:CPAP.jp
g

28. Operation Modes
Spontaneous Ventilation
– Pressure Support
This mode is similar to the CPAP mode with the exception that
during the inspiration the ventilator attempts to maintain the patient
airway pressure at a level above PEEP. In fact, CPAP may be
considered a special case of pressure support ventilation in which
the support level is fixed at the atmospheric level.
In this mode, when the patient’s airway pressure drops below the
therapist-set sensitivity line, the ventilator inspiratory breath delivery
system raises the airway pressure to the pressure support level
(>PEEP), selected by the therapist. The ventilator stops the flow of
breathable gases when the patient starts to exhale and controls the
exhalation valve to achieve the set PEEP level.

29. Ventilators Parts
• Power supply
• Compressed air and oxygen
• A drive mechanism to push oxygen
• A control mechanism
• Humidifier

30. Block Diagram
Malkin, Robert. “2.2 Ventilators.” Medical Instrumentation in the Developing World. Engineering World Health, 2006.

31. Diagram
• Boyle’s Ether Vaporizer
WHO. “Anesthetic and Resuscitation Equipment.” Maintenance and Repair of Laboratory, Diagnostic Imaging, and Hospital Equipment (WHO: 1996), p. 121-134.

32. Air Moisture
• 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)

33. Air Moisture
• Humidifier
Pass air over liquid to pick up natural vapor
• Vaporizer
Heat liquid to increase amount of vapor
• Nebulize
Turn liquid to fine spray by passing gas through liquid or by
ultrasonic agitation

34. Air Moisture
• Some ventilators heat the tubing or air to prevent
“rain-out” of the vapor delivered to the patient.
• Older systems may have water traps

35. Review
• Forced breathing or assisted breathing for patient
• Inputs: Gases (usually air & oxygen) plus water for
humidification
• Outputs: Humidified (and warmed) gas to patient
• Modes of operation: Pressure limited, volume limited
or timed cycle
• Modes of initiation: controlled and assisted

36. Commercial Examples
WHO. “Ventilator, Intensive Care, Neonatal/Pediatric.” From the publication: “WHO Technical Specifications for 61 Medical Devices.
WHO. Retrieved from: http://www.who.int/medical_devices/management_use/mde_tech_spec/en/

37. Patient’s Safety
• Barotrauma
– PIP(peak inspiratory pressure) > 45 cmH2O
• Volutrauma
– VT > 6-8 ml/Kg
• Oxygen Toxicity
– Prolonged FIO2 (fraction of inspired oxygen)
of 1.0

38. Patient’s Safety
• Pneumonia (most common)
• Hypotension

39. Preventive Maintenance
• Filters cleaning
• Leak troubleshooting
• Calibration
• Change O2 sensor
• Use of gloves
LadyInGrey (2005), Disposable Nitrile Gloves [photograph].
Retrieved from
https://commons.wikimedia.org/wiki/File:Disposable_nitrile_
glove.jpg

40. Common Problems
• In the US it is illegal for
uncertified engineers/technicians
to work on ventilators
• Never work on a ventilator when
connected to a patient

41. Common Problems
• User error
• Power supply
• Filtration
• Tubing

42. Common Problems
• User error
– Controls are not standardized
between manufacturers
– Manuals were either not supplied
with the donation or were supplied
in a language that the hospital staff
does not speak

43. Common Problems
• Tubing
– Disposable tubing is being reused...The non-
rebreathing valve may break or the tubing
may leak.

44. Common Problems
• If the problem is not one of these problems, 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

45. Test Procedures
• Measuring the breathing rate and
measuring the I:E ratio (approximately
20% of the set ratio)
• The pressure limit: Partially occluding the
connection to the patient with your hand
(light should flash)

46. Test Procedures
• Assisted mode:
– Place the patient tube in your mouth (The device will
deliver gas only when you inhale)
– Remove the tube from your mouth (The device should
take over in a controlled mode)
– Place the tube back in your mouth and breathe
normally and the device should automatically return to
assisted mode

47. Test Procedures
• Breathing circuit:
– Leak test - occlude one end and blow hard into the
other end with the tube submerged in water…should
be no bubbles
– Soapy water
Erich Schulz, Brisbane (en:Image:Syringe.jpg) [Public domain], via Wikimedia Commons

48. Test Procedures
• Breathing circuit:
– Leak test - occlude one end and blow hard into the
other end with the tube submerged in water…should
be no bubbles
– Non-rebreathing
• Blow 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

49. Test Procedures
• Pressure Limit:
– Connect 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