CPAP BASICS

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 • 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 • BiPAP • 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

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 = 0.725 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