GRANT COUNTYAPRIL 2014

CPAP BASICS

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

OBJECTIVES

“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

DEFINITIONS

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

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 VS CPAP

Continuous positive pressure delivery systemProvides more airway pressure than a non-

rebreather mask but less than BVMSimilar to sticking your head out of a window

while traveling at highway speeds

CPAP

Non-invasiveEasily AppliedEasily RemovedUseful for many types of respiratory distress

CHF, COPD, Asthma, Pneumonia, Near drowningsAble to give nebs and other medications “in-line”

or while it is appliedCan 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 USAGE ADVANTAGES

“Alternative” to ETT Intubation Some patients are not great candidates for intubations or are

frail and likely to have a diffi cult 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 (diffi cult to extubate), causes increased morbidity with pneumonia risk and risk for spontaneous pneumothorax

CPAP ADVANTAGES

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

WHY CPAP?

Ventilation and perfusion mismatchCauses:

Pulmonary EdemaPneumonia Increased dead space (collapsed or atelectatic lung)

Pulmonary embolismShunt

V/Q MISMATCH

Upper LungsV>P

Mid LungsV=P

Lower LungsV<P

Overall Avg:80%

NORMAL V/Q

Caused by lack of perfusion (ventilation is normal)Pulmonary embolismCardiac arrestHypovolemia/shock

Normal phenomenon in dead spaceUpper lung, V>P

HIGH V/Q RATIO

Enough Perfusion, not enough ventilationAtelectasis Increased secretionsMucus pluggingBronchial intubationshunt

LOW V/Q RATIO

Hypothetical pressure of a gas in the atmosphere were it to occupy the same volume of space as the mixture it is inAir at sea level has a pressure of 1 atmosphere, or 760 mmHg

Air is 21% oxygen at sea levelThe partial pressure of room air 02 is 760 x 0.21 = 159 mmHg

PARTIAL PRESSURE OF GAS

The diff erence 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

PRESSURE GRADIENTS

CPAP changes the pressure gradientCPAP is measured by cmH2O

1 cm H2O = 0.725 mmHgTypically CPAP is applied at either 5 or 10

cmH2OThis 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

CPAP AND PRESSURE GRADIENTS

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

MECHANICAL EFFECTS

Increased oxygen levelsReduced work of breathingReduced V/Q mismatch

PHYSIOLOGICAL EFFECTS OF CPAP

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

GRANT COUNTY PROTOCOL

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)

CONTRAINDICATIONS

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

PROCEDURE

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 maskSometimes 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

PRECAUTIONS

Proceed to advanced airway for patients with worsening respiratory distress or decreasing level of consciousness

Not for use in children <12 years oldAdvise receiving hospital of CPAP application

so they can prepare and have respiratory therapy on standby

SPECIAL NOTES

Pulmonary Edema patients often improve within minutes of application of CPAPCPAP is to pulmonary edema like D50 is to hypoglycemia

Visual inspection if chest wall movement should demonstrate improved respiratory excusionBilateral chest wall movement, retractions, etc

“Look, listen and feel”

IMPORTANT POINTS

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

CPAP VS INTUBATE

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 DISTRESS

Declining tidal volumeIrregular or gasping breathsPoor 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

RESPIRATORY FAILURE

CPAP can provide an adjunct to allow medications to take effect (“Buys time”)

CPAP reverses CHF induced pulmonary edemaCPAP can prevent prolonged ventilation that

can occur after intubationNon-invasive = can be used on DNIFixes V/Q mismatch, opens airways, increases

oxygen pressure gradient, reduces work of breathing

SUMMARY