1. CPAP BASICS
GRANT COUNTY
APRIL 2014

2. OBJECTIVES
Establish a protocol for Continuous Positive Airway Pressure usage for pre-hospital respiratory distress
Discuss the basic principles of Continuous Positive Airway Pressure and its application
Review the physiological effects of CPAP
Discuss the indications and contraindications of CPAP usage

3. Definitions “Learn the Lingo”
NIPPV: Non-Invasive Positive Airway Pressure
Includes BiPAP, CPAP, Bag valve mask
Continuous Positive Airway Pressure (CPAP)
What we will be using
Bi-Level Positive Airway Pressure (Bi-PAP)
Often used in the hospital once the patient arrives
PEEP: Positive End Expiratory Pressure
A value we can measure on ventilated patients (ie, closed circuit)
Both BiPAP and CPAP provide a small amount of PEEP

4. BIPAP vs CPAP BiPAP CPAP Continuous Pressure
Pressures are different between inhalation and exhalation (ie, 12/8 cm/H20)
Not commonly used in the field or at home due to the complexity of delivery/devices
Needs monitoring of delivered pressures
Expensive
CPAP
Continuous Pressure
Same pressure during exhalation and inhalation
Used in the field and at home
Less complicated devices for delivery
Needs little monitoring
Set it and it’s good
Cheaper

5. CPAP Continuous positive pressure delivery system
Provides more airway pressure than a non-rebreather mask but less than BVM
Similar to sticking your head out of a window while traveling at highway speeds 

6. CPAP Usage Advantages Non-invasive Easily Applied Easily Removed
Useful for many types of respiratory distress
CHF, COPD, Asthma, Pneumonia, Near drownings
Able to give nebs and other medications “in-line” or while it is applied
Can serve as a “bridge” to give patients extra respiratory support as the other medications and treatments have time to take effect (ie. Nitro/lasix, duonebs, steroids, etc)
Can help avoid intubations for patients that are likely to rapidly improve with adjunct treatments

7. CPAP Advantages “Alternative” to ETT Intubation
Some patients are not great candidates for intubations or are frail and likely to have a difficult extubation
Prospective randomized trials have shown 50-70% of patients with a severe COPD exacerbation who receive non-invasive ventilation can avoid intubation
Prehospital use of CPAP for moderate-severe respiratory failure has been proven effective
Reduction in intubation rate of 30%
Absolute Reduction in mortality of 21% In appropriately selected patients who received CPAP instead of usual care (intubation)
COPD patients who are intubated typically are ventilator dependent for longer periods (difficult to extubate), causes increased morbidity with pneumonia risk and risk for spontaneous pneumothorax

8. Why cpap? Positive Pressure! Redistributes lung fields (inflates)
Reduces work of breathing
Counteracts intrinsic PEEP
Pursed lip breathing
Improves Lung Compliance
Reverses Atelectasis
Collapsed alveoli
Decreases Preload/Afterload
Beneficial esp for CHF patients
Decreased V/Q mismatch (ventilation/perfusion)
Improves Gas Exchange

9. V/Q Mismatch Ventilation and perfusion mismatch Causes:
Pulmonary Edema
Pneumonia
Increased dead space (collapsed or atelectatic lung)
Pulmonary embolism
Shunt

10. Normal v/q Upper Lungs V>P Mid Lungs V=P Lower Lungs V<P
Overall Avg:80%

11. High v/q Ratio Caused by lack of perfusion (ventilation is normal)
Pulmonary embolism
Cardiac arrest
Hypovolemia/shock
Normal phenomenon in dead space
Upper lung, V>P

12. Low V/Q ratio Enough Perfusion, not enough ventilation Atelectasis
Increased secretions
Mucus plugging
Bronchial intubation
shunt

13. Partial Pressure of gas
Hypothetical pressure of a gas in the atmosphere were it to occupy the same volume of space as the mixture it is in
Air at sea level has a pressure of 1 atmosphere, or 760 mmHg
Air is 21% oxygen at sea level
The partial pressure of room air 02 is 760 x 0.21 = 159 mmHg

14. Pressure Gradients
The difference in pressure between a higher concentration of gas and a lower concentration of gas is called a pressure gradient
Gas has a tendency to move from a higher partial pressure to a lower partial pressure until equilibrium is established
This pressure gradient is what causes oxygen to enter the blood and CO2 to leave the blood (gas exchange)
Happens at the alveolar level
Expired air has oxygen content of about 16%, so the parital pressure is 760 mmHg x 0.16 = 121 mmHg
The pressure gradient of oxygen between room air (159mmHg) and blood oxygen (121mmHg) creates a gradient to allow oxygen exchange

15. CPAP and Pressure Gradients
CPAP changes the pressure gradient
CPAP is measured by cmH2O
1 cm H2O = mmHg
Typically CPAP is applied at either 5 or 10 cmH2O
This increases the partial pressure by 2.25%
Increased partial pressure of oxygen delivered results in greater differential and improved oxygen exchange
The clinical effects can be impressive with even this small change

16. Mechanical effects Increased airway pressure with CPAP
Stent open airways that are at risk of collapse due to excess fluid or edema
Inflates alveoli and prevents collapse during expiration
Creates greater surface area= better exchange of gases
Decreases the work of breathing by preventing continual collapse of the airways
Patient senses easier breathing, less work esp on inspiration
Maintains gas exchange over a longer period of time

17. Physiological effects of cpap
Increased oxygen levels
Reduced work of breathing
Reduced V/Q mismatch

18. Grant county protocol
Indications: moderate to severe respiratory distress from the following:
Pulmonary edema/CHF (including from near drownings)
Acute Asthma exacerbation not responding quickly to usual treatments
COPD exacerbation failing conventional treatments
Pneumonia

19. contraindications DO NOT USE CPAP IF:
The patient is unconscious or altered
GCS<13-14 or unable to protect their own airway
Hypotensive (SBP <90 mmHg)
Vomiting
Suspected pneumothorax (ensure equal bilateral breath sounds prior to application)
Trauma
Facial abnormalities
Unable to obtain mask seal (large beard, etc)
Extreme caution in pulmonary fibrosis (lowest pressure setting if used)
Dementia (moderate or severe)

20. Procedure
Know your CPAP device and how to adjust it (many options out there)
Overall goal is to increase airway pressure and improve oxygen delivery/gas exchange
Verbally coach patient, explain the procedure
Apply waveform capnography (ETCO2)
Apply CPAP with pressure of 5-10 cmH20
Coach and reassure the patient (slow, deep breaths)
Watch for resistance and apprehension
Check for leaks around the mask/ensure good seal
Reassess lung sounds and vitals q3-5 minutes

21. Procedure In line nebs can be administered while the CPAP is on
Nitroglycerin may be administered by momentarily lifting the facemask
If the patient becomes more confused or is not tolerating the CPAP mask and still has severe distress, move to ETT intubation or other advanced airway measures

22. Precautions
CPAP may cause a drop in blood pressure due to increased intrathoracic pressure
Watch for GI distention, which may lead to vomiting
Patient may become claustrophobic or unwilling to tolerate mask
Sometimes coaching can overcome this, give them direct feedback on inhalation and exhalation
Use with great caution in patients with dementia, must have cognitive ability to understand what CPAP does

23. Special notes
Proceed to advanced airway for patients with worsening respiratory distress or decreasing level of consciousness
Not for use in children <12 years old
Advise receiving hospital of CPAP application so they can prepare and have respiratory therapy on standby

24. Important Points
Pulmonary Edema patients often improve within minutes of application of CPAP
CPAP is to pulmonary edema like D50 is to hypoglycemia
Visual inspection if chest wall movement should demonstrate improved respiratory excusion
Bilateral chest wall movement, retractions, etc
“Look, listen and feel”

25. CPAP vs intubate When to do what:
Respiratory distress = increased effort and frequency of breathing in maintaining normal O2 and CO2 in the blood
Respiratory Failure = inability to maintain normal amounts of O2 and CO2 in the blood

26. Respiratory distress Signs of respiratory distress:
Tachypnea
Tachycardia
Accessory muscle use
Decreased Tidal Volume
Paradoxical breathing (abdominal muscles)
CPAP can generally be used on these patients

27. Respiratory Failure Declining tidal volume
Irregular or gasping breaths
Poor color = poor perfusion = poor oxygen exchange
Not likely to improve without invasive measures
Decline in LOC
Hypercarbia
Hypoxemia
High CO2 lowers pH, causing acidosis
Acidosis causes further metabolic changes and ultimately leads to cardiac arrest

28. Summary
CPAP can provide an adjunct to allow medications to take effect (“Buys time”)
CPAP reverses CHF induced pulmonary edema
CPAP can prevent prolonged ventilation that can occur after intubation
Non-invasive = can be used on DNI
Fixes V/Q mismatch, opens airways, increases oxygen pressure gradient, reduces work of breathing