CPAP BASICS GRANT COUNTY APRIL 2014

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

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

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

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 

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

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

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

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

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

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”

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

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

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

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