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CONTINUOUS POSITIVE
AIRWAY PRESSURE
CPAP
Objectives
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Define CPAP
Understand pathophysiology
EMS applications
Protocol implementation
What is CPAP???
• CPAP increases pressure in the lungs and holds
open collapsed alveoli, pushes more oxygen
across the alveolar membrane, and forces
interstitial fluid back into the pulmonary
vasculature.
• This improves oxygenation, ventilation and ease
of breathing.
• The increased intrathoracic pressure decreases
venous return to the heart and reduces the
overwhelming preload (pressure in the ventricles
at the end of diastole).
• This lowers the pressure that the heart must
pump against (afterload), both of which improve
left ventricular function.
So why does oxygen pass into the blood?
Pressure Gradient
Deoxygenated blood has a lower partial pressure of oxygen
than alveolar air so oxygen transfers from the air into the
blood.
CPAP alters the pressure gradient!
7.5cm H20 CPAP
1cm H2O is equal to 0.735mm Hg.
7.5cm H2O CPAP increases the partial pressure of the
alveolar air by approximately 1%.
This increase in partial pressure ‘forces’ more oxygen
into the blood.
Even this comparatively small change is enough to
make a clinical difference.
Perfusion
• Refers to the process of circulating blood
through the pulmonary capillary bed
• In order for perfusion to occur, the
following must be intact:
– A properly functioning heart (pump)
– Proper vascular “size”
– Adequate blood volume / hemoglobin
The Requirements Of CPAP
 The real requirement is for Continuous
CONSTANT Positive Airway Pressure
 A stable airway pressure as prescribed in order to
reduce work of breathing (WOB)
CPAP is oxygen therapy in
its most efficient form.
 Simple Masks
 Venturi Masks
 Humidifiers
 CPAP
Important Aim Of CPAP Is To
Increase Functional Residual
Capacity (FRC)
 Volume of gas remaining in lungs at endexpiration
 CPAP distends alveoli preventing collapse on
expiration
 Greater surface area improves gas exchange
Physiological Effects Of
CPAP
 Increases PSO2
 Increases FRC
 Reduces work of breathing
Indications for Use
• Treatment of severe
respiratory distress
CHF/COPD/Asthma
• RR>25 bpm
• Retractions, accessory muscle
use or fatigue
• SAO2 < 94% at any time
• Near drowning
• Pt must be able to maintain
own airway and be able to
follow commands.
Exclusion Criteria
• BP <90 mmHg
• Unconscious
• Inadequate
respiratory rate
• Cardiac arrest
• Unable to obtain
adequate seal
• Pnuemothorax
• Active emesis
CPAP And Pulmonary Edema
 Severe pulmonary edema is a frequent cause of
respiratory failure
 CPAP increases functional residual capacity
 CPAP increases transpulmonary pressure
 CPAP improves lung compliance
 CPAP improves arterial blood oxygenation
 CPAP redistributes extravascular lung water
(Rasanen 1985)
Redistribution Of Extravascular
Lung Water With CPAP
Benefits/Advantages of CPAP
• CPAP reduces work of breathing by
keeping the “wet” alveoli open
• If the alveoli are open at the end of
expiration, energy is not consumed on the
next inhalation
• Work of breathing is reduced relieving
respiratory muscle fatigue
Benefits/Advantages of CPAP
• A higher alveoli pressure will result in a
stoppage of fluid movement into the
alveoli
• Increase in airway pressure results in
improved gas exchange
CPAP And Acute Respiratory
Failure
 CPAP overcomes inspiratory work imposed by auto-peep
 CPAP prevents airway collapse during exhalation
 CPAP improves arterial blood gas values
 CPAP may avoid intubation and mechanical ventilation
(Miro 1993)
WHAT ABOUT THE
EMPHYSEMA PATIENT?
Important Point
• Emphysema
patients do not
respond
predictably to
CPAP
As a general rule…
• The larger the “barrel chest” and the more
pronounced the accessory muscles, the
more caution we should use with CPAP
What is needed for CPAP
application.
•
Oxygen source capable of producing 50 psi.
•
Flow regulator which delivers either a fixed oxygen concentration
at 30% or an adjustable flow regulator.
– Venturi
– Micro channels
•
Tight fitting mask to which the oxygen/air mixture output of the
generator is attached and applied to the patient.
•
Positive End-Expiratory Pressure (PEEP) valve connected to the
exhalation port which maintains a constant pressure in the circuit.
• What are some signs and symptoms of
respiratory distress??
What is needed for CPAP
application.
•
Oxygen source capable of producing 50 psi.
•
Flow regulator which delivers either a fixed oxygen concentration
at 30% or an adjustable flow regulator.
– Venturi
– Micro channels
•
Tight fitting mask to which the oxygen/air mixture output of the
generator is attached and applied to the patient.
•
Positive End-Expiratory Pressure (PEEP) valve connected to the
exhalation port which maintains a constant pressure in the circuit.
• What are some signs and symptoms of
respiratory distress??
CPAP Contraindications
• CPAP may be contraindicated for patients with
any of these conditions:
– Unconscious
– Apnea
– Pneumothorax
– Decreased cardiac output and gastric
distention
– Severe facial injury
– Hypotension secondary to hypovolemia
– Uncontrolled vomiting
Explain the Procedure to your
Patient
• Explain to your patient that in order to get
the best possible results from a CPAP
device. Ask them to inhale through the
nose and exhale through the mouth
against the pressure produced by the
CPAP machine.
• If they do not know what to expect, it is
similar to the air felt when sticking your
head out of the car window when moving.
The Whisperflow
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Here is a step by step review of the operation
of the Whisperflow CPAP device.
• Properly assess
pt for baseline
Pulse Oximetry
• Attach high pressure hose to portable tank
using short adapter hose. It may be best to
load the patient first
and start CPAP early in the transport:
conserves portable tank
for ER transfer.
• Assemble mask and tubing, don't forget to
place the
filter on air intake of the CPAP device
The Whisperflow
Prepare mask,
strap
rearrangement
might be
necessary
Explain the
procedure to the
patient. Turn the
unit on (all the
way) & turn the
FLOW on (all the
way)
Have the patient place the mask
on his/her face tightly. Some
"coaching" will help the patient
transition from holding the mask
near their face to creating a
seal. It's OK for the patient to
hold the mask without using the
straps if they're more comfortable
that way. When he is comfortable
with the feeling of the mask
you may secure it to his head
tightly so that no leaks are
noticed.
Final Application Steps
Next you'll need
to fine-tune the
unit by
decreasing the
FLOW until a
slight outward
flow is felt while
the patient
inhales.
You can easily add nebulized
albuterol to the
patient's treatment by cutting
the tubing at a joint
and inserting a 'T' and
nebulizer with
6 liters oxygen attached.
After loading the
patient to the
unit you'll need
to
transfer to the
onboard oxygen.
Do it quickly turn on the main
first!
By using the patient's pulse-ox
level as a guide you may adjust
the amount of oxygen up to
achieve desired oxygen
saturation, usually 90 -93%.
If the mask is not tolerated
after coaching…remove it!!!
A few things to
remember...
• When the flow valve is open all the way, with the
oxygen valve closed, you are giving the patient
28% oxygen and a portable tank will last quite
some time!
• By increasing the oxygen flow, you'll use more
liters per minute - as much as 140! Be careful,
you'll run out!
• If you reach the point that air is blowing out of
the air intake on the device your oxygen flow is
too high.
• When swapping from portable to main oxygen
tanks warn the patient that the flow will stop for a
few seconds but they will still be able to breathe,
then swap quickly!
Oxygen Tanks
At 28-30% FiO2 , a full tank should last
approximately:
• D cylinder=28 minutes
• E cylinder=40-50 minutes
• M cylinder=about 4 hours
• FiO2 is fraction of inspired oxygen.
(at 100% FiO2 a D cylinder tank will last approximately 3-4 minutes. Use
what you need, but be prepared with additional cylinders)
Case Study for CPAP
You are called to a 76-year old male who is complaining
of dyspnea. Upon arrival, you find the patient sitting
on a chair leaning forward. He is diaphoretic,
cyanotic and has a respiratory rate of 48. Upon
auscultation you hear fine crackles throughout both
lung fields and he is hypertensive.
http://www.eresp.com/CPAPosSim.swf
Works Cited and Thank
You
Thank you to EMS Personnel at Dallas Ambulance, ST Paul Fire, Salem Fire, Rural Metro,
Washington Co EMS, MTCI, Albany Fire, Marion County, and Mercy Flights for sharing
information regarding CPAP. The following websites were also use as resources.
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http://www.dhfs.state.wi.us/ems/EMSsection/Protocols/CPAP/CPAP_Protocol.pdf
http://www.ems1.com/columnists/dan-white/articles/390898-A-Look-at-CPAP-for-EMS
http://caradyne.respironics.com/whisperflow.htm
http://phillydan.spaces.live.com/Blog/cns!B2AD15EED4F62B2B!236.entry
http://elearning.respironics.com/main_ProdTrainCourse_pr.asp
http://www.jcems.net/cgi-bin/news.cgi
http://www.eresp.com/CPAPosSim.swf
http://www.miamitwp.org/fireems/training/skill_sheet_ems.htm
http://www.emsresponder.com/features/article.jsp?id=1738&siteSection=16
http://www.maconnc.org/ems/CPAP.html
http://www.merginet.com/index.cfm?pg=airway&fn=CPAPuser
http://emsstaff.buncombecounty.org/inhousetraining/cpap/cpap_overview2.htm
http://www.doctorfowler.com/lecturepage.shtml
Questions and answers