CPAP for NYS EMTs is coming

                                                                  CPAP FOR EMS

Continuous Positive Airway Pressure (CPAP) devices will be coming to NYS EMT's shortly.  Here is a short guide to CPAP.  Since we do not know yet how the NYS BLS Protocols will permit EMTs to use CPAP we will keep it very general for now. It will obviously be used in Acute Pulmonary Edema, but it is unclear if it will be allowed in other emergency situation.

Before we start just remember that CPAP cannot be used in any patient with any of the following conditions EVEN if they are in respiratory distress:

1. Decreased Mental Status / Inability to sit up / Altered Mental Status
2. Respiratory arrest / Apnea /  Respiratory failure / poor inspiratory effort
3. Pneumothorax / Trauma to the thorax / Subcutaneous Emphysema
4. Any form of Shock / Hypotension
5. Nausea / Vomiting / any risk of aspiration
6. Facial Trauma / Abnormalities

How CPAP Works:

Continuous Positive Airway Pressure, (CPAP), is the maintenance of positive pressure throughout the complete respiratory cycle, (inspiration and expiration), when breathing spontaneously. CPAP is not the same as Positive End Expiratory Pressure or PEEP. PEEP only provides pressure on the expiratory side by offering resistance to exhalation using a spring-loaded valve or air flow.

 

1. During the inspiratory phase, patients in distress will have to create a higher flow rate of air to meet their needs, this will present as an increase in work-of-breathing (WOB). Patients in respiratory distress may need to achieve inspiratory flow rates greater than 65 liters per min (LPM). With the inspiratory support of CPAP, the patient does not have to work as hard to inhale and overcoming the auto PEEP in the lung. Auto-PEEP represents the abnormal, and usually undetected, residual pressure above atmospheric remaining in the alveoli at end-exhalation due to air trapping.  The auto PEEP has to be overcome each time a person inhales, for a healthy person the work is minimal and goes unnoticed. However, those patients with stiff lungs, (CHF and Pulmonary Fibrosis), have to work extremely hard to overcome the increased auto PEEP on every breath.

 

2. The increased inspiratory pressure also increases the size, therefore the surface area of the

alveoli, providing a greater opportunity for gas exchange or respiration. The process increases the

Functional Residual Capacity (FRC) of the lung. The FRC is the area where gas exchange takes place.

 

3. Since a greater oxygen percentage is able to reach the alveoli during CPAP, the partial pressure

of the oxygen molecule will be greater. The higher partial pressure will allow more oxygen to

diffuse into the blood stream improving oxygenation.

 

4. Fluid in the alveolar space cannot only make the lung stiff, (increasing inspiratory

work-of-breathing), it also creates a barrier that can reduce gas exchange. The pressure from CPAP

can reduce the fluid by forcing fluid out of the alveolar space back into the interstitium.

 

5. During the expiratory phase, the patient will breathe against a threshold of resistance that

works as a pneumatic splint to hold the airways open. Patients with chronic lung disease have

weakened airways that have a tendency to collapse on expiration, causing air trapping. Having the

airways stinted open during exhalation will make inspiration on the next breath less difficult.

 

6. The resistance during exhalation can open non-ventilated areas of the lung recruiting alveoli

that have collapsed due to atelectasis, (a collapse of lung tissue affecting part, or all, of one

lung effecting gas exchange).

 7. CPAP decreases pre-load and after-load on the heart reducing the heart’s workload. However, a reduction in pre-load and after-load will have an effect on the patient’s blood pressure. Patients

should have a systolic blood pressure of at least 100 mmHg before starting CPAP.

 

What Types of Patients Are NOT Candidates for CPAP?

Being able to assess and determine who is, and who is not, a candidate for CPAP has a great impact on whether CPAP will be effective or not. CPAP can be a very effective treatment for patients in respiratory distress but is not indicated for patients in respiratory failure. Respiratory distress patients are still compensating even though they may be working hard. It is not uncommon for respiratory distress patients to have oxygen saturations (SpO2 ) and carbon dioxide, (CO2), levels within normal range. Key determinants include; is the patient alert, (even though they are working hard), and can they follow directions. Patients that have gone into respiratory failure may exhibit a decrease in work-of-breathing, CO2 levels climbing, oxygen saturations falling, and their level of consciousness declining, (most likely from CO2 narcosis). CPAP is not indicated for respiratory failure patients.

 

CPAP and Congestive Heart Failure (CHF):

The treatment of Congestive Heart Failure, (CHF), by EMS has changed significantly in the last couple of years. The mainstays of CHF treatment (ALS) in the pre-hospital setting are CPAP and nitroglycerin. The efficacy of Lasix and Morphine is under scrutiny and has been removed from many EMS ALS protocols. Many systems that adopt CPAP start with CHF. The effects of CPAP are well suited for the physiologic issues associated with this disease. Pulmonary edema, associated with CHF, makes the lungs stiff and it is difficult for the patient to inhale; and can be observed as difficulty breathing during the inspiratory phase of ventilation or inspiratory shortness-of-breath. Since CHF is primarily a heart problem, CPAP addresses the side effects of a failing heart and its impact on the lungs.  CHF is a process that will continue to spiral down the cardiogenic shock pathway until the cycle is broken. As the patient’s heart fails, more fluid ends up in the lungs. With more fluid in the lungs, less oxygen makes it to the heart muscle, so the heart fails even more. The first step in stopping the cycle is the early use of CPAP. If the patient does not have lung disease then the airways should function normally and not collapse on exhalation. In this case, the inspiratory pressure will force the fluid out of the lungs, expand the alveoli which, in turn, will increase gas exchange (respirations) improving oxygenation.In addition, with the airways being held open by the expiratory resistance, the patient does not have to overcome

the auto PEEP at the beginning of each breath. With the improvement of gas exchange and reduced impact of auto PEEP, the patient’s work-of-breathing will be reduced. With the reduced work, there will be less stress on the heart. A key factor in the initiation of CPAP is the patient’s blood pressure. It is recommended that the systolic blood pressure be at least 100 mmHg before starting CPAP due to the reduction in pre-load and after-load.

 

More to come after the protocols are released.