Continuous positive airway pressure, or CPAP, is a non-invasive treatment method intended for patients who are experiencing respiratory distress but are still able to maintain their own airway. CPAP was originally used for people who experience obstructive sleep apnea to increase pressure in the upper airway and prevent tracheal collapse during sleep. However, it has been found to be a great tool in the pre-hospital setting and decreases the need for more invasive airway management, such as intubation. Although effective, endotracheal intubation can be difficult in the field and contains some complications and disadvantages. If used early enough, CPAP can prolong the need for intubation or even replace the need for it altogether. It is important to remember though, that CPAP only treats the symptoms of respiratory distress; it does not fix the main problems the patient is suffering from.

Who needs it?

Continuous positive airway pressure is indicated for patients whose oxygen demand has exceeded their ability to compensate for their lack of oxygen. It has been proven to be extremely helpful for people with fluid in their lungs (pulmonary edema), Chronic Obstructive Pulmonary Disease (COPD), and acute bronchospasms, such as asthma. Other reasons people may need CPAP include toxic inhalation, drowning, flail chest and various lung infections such as pneumonia. It should be used on patients who are alert and able to follow commands, show signs of respiratory distress, have rapid breathing, and a pulse oximetry of less than 90%. It is important, however to follow your protocols on when to use CPAP.

How it works

Continuous positive airway pressure improves ventilation and respiration by increasing the pressure in the lungs. The continuous pressure opens up the alveoli and prevents them from collapsing. This allows more oxygen to be forced across the alveolar membrane, and pushes out any fluid in the lungs, forcing it back into the pulmonary circulation. This improves oxygenation to the blood and eases the work of breathing. In addition, it increases intrathoracic pressure, which decreases venous return to the heart. This decreases the hearts preload, which is especially beneficial for patients suffering from pulmonary edema caused by congestive heart failure. However, it can result in hypotension.

Using CPAP

The CPAP device generally consists of a generator, corrugated circuit tubing, a one-way valve with a filter, and a mask. Be sure to have a full oxygen cylinder because CPAP uses a large amount of oxygen. Connect the circuit and attach it to the oxygen cylinder. Apply the mask to the patients face and allow them to hold it to get comfortable with it. The device may be scary to some patients or might make them feel claustrophobic. They may need to be coached through the experience until they are comfortable with it. If it is their first time using it, explain that it feels like they are sticking their head out of a car window and they must exhale against the resistance. The resistance on expiration is called positive end-expiratory pressure, or PEEP. There is a valve that controls the PEEP setting and it should be set between 5-10 cm H2O. Once they are comfortable with the mask, attach the head strap and ensure a tight seal around the nose and mouth. Continue to reassess the patients’ lung sounds and vitals.

Contraindications

Although CPAP is effective for patients in respiratory distress, it will not breathe for them and therefore should not be used on unconscious patients or patients with altered mental status. It should not be used in cases of hypoventilation or any cases of airway compromise. Due to the air pressure, there is a risk of aspiration and so it should not be used on patients who are experiencing any nausea or vomiting. Do not use it if you are unable to obtain a tight mask seal such as with patients who have too much facial hair or facial trauma. Do not use if you suspect the patient has a pneumothorax. And lastly, do not use it if the patient is not able to tolerate it.