Gold Cross Ambulance
CPAP
Continuous
Positive
Airway
Pressure
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Presentation Structure
1. Goal of CPAP in the field
2. CPAP and its
physiological effects
3. CPAP delivery systems
4. Medical applications of
CPAP
5. When not to use CPAP
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Goal of CPAP
To have an effective way to treat
CHF/COPD
Medications are continued throughout patient
care
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History of CPAP
1912 - Maintenance of lung expansion during thoracic surgery (S. Brunnel)
1937 - High altitude flying to prevent hypoxemia. (Barach et al)
1967 - CPPB + IPPV to treat ARDS (Ashbaugh et al)
1971 - Term CPAP introduced, used to treat HMD in neonates (Gregory et al)
1972 - CPAP used to treat ARF (Civetta et al)
1973 - CPAP used to treat COPD (Barach et al)
1981 - Downs generator (Fried et al)
1982 - Modern definition of CPAP (Kielty et al)
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CPAP and Patient
Airway Pressure
‘The application of positive airway pressure throughout the
whole
respiratory cycle to spontaneously breathing patients.
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CPAP and Partial Pressure
‘The pressure of a gas mixture is equal to the sum of the
partial pressures of its constituents.
This allows oxygen into the blood during inspiration and
Carbon Dioxide out during expiration.
Example : Air at sea level has a pressure of 760mm Hg.
Air is 21% oxygen and 79% nitrogen.
partial pressure of oxygen is 760 X 21% = 159mm Hg
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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.
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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.
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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)
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CPAP is oxygen therapy in
its most efficient form.
Simple Masks
Venturi Masks
Humidifiers
CPAP
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Important Aim Of CPAP Is
To Increase Functional
Residual Capacity (FRC)
Volume of gas remaining in lungs at end-expiration
CPAP distends alveoli preventing collapse on expiration
Greater surface area improves gas exchange
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Physiological Effects Of
CPAP
Increases PSO2
Increases FRC
Reduces work of breathing
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Essential Components Of
A CPAP System
1. Flow generator
2. CPAP valve
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Whisperflow Flow
Generators
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Caradyne Isobaric CPAP
Valve
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Patient Connections -
Face Mask
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The High Flow System In
Operation
Air Supply In
Total Flow 60 L/min
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Application of CPAP
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Application Continued
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CPAP System
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Gold Cross Ambulance
Current Uses of CPAP
1. Ambulance/Emergency Room
2. Pre-Operative (Anesthesia)
3. Intensive Care
4. Recovery Room
5. General Ward
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Clinical Applications of
CPAP
Condition Area for Treatment
ARDS Emergency
Pulmonary edema Emergency
Acute Respiratory Failure Emergency
CHF/COPD Emergency
Anesthesia Pre Operative
Atelectasis ICU/General Ward
Alternative to Mechanical Ventilation ICU/General Ward
Weaning from Mechanical Ventilation ICU/General Ward
Also:
Left Ventricular Failure
Renal Failure
Sleep Apnea
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Adult Respiratory Distress
Syndrome (ARDS)
Characteristics
Hypoxemia
Reduced compliance
Large intrapulmonary shunt
CPAP in early stages may
Correct hypoxemia
Improve compliance
Reduce intrapulmonary shunt
(Schmidt 1975)
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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)
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Redistribution Of
Extravascular Lung Water
With CPAP
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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)
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When Not To Use Mask
CPAP
Hypercapnia
Pneumothorax
Hypovolemia
Severe facial injuries
Patients at risk of vomiting
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Common Complications
With CPAP
Pressure sores
Gastric distension
Pulmonary barotrauma
Reduced cardiac output
Hypoventilation
Fluid retention
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CPAP Training Flow Sheet
No Exclusion Criteria Present
-Respiratory/Cardiac Arrest
-Pt.unable to follow commands
-Unable tp maintain patent airway independently
-Major Trauma
-Suspicion of a Pneumothorax
-Vomiting or Active GI Bleed
-Obvious signs/Symptoms of Pulmonary infection
2 or more of the following Respiratory Distress
Inclusion Criteria
-Retractions of accessory muscles
-Brochospasm or Rales on Exam
-Respiratory Rate > 25/min.
-O2 Sat. < 92% on high flow O2
Administer CPAP using Max FIO2
Stable or Improving Reassess Patient Deteriorating
-Contact Medical Control with report
-Continue CPAP -Discontinue CPAP unless advised by Medical Control ,
-Continue COPD/Asthma/Pulmonary Edema Protocol -Continue Asthma/COPD/Pulmonary Edema Protocols
-Contact Medical Control with a Report
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