Lesson 4 – Continuous Positive Airway Pressure (CPAP)

Introduction to CPAP

Continuous Positive Airway Pressure (CPAP) is a non-invasive technique used to manage respiratory emergencies. It delivers constant positive pressure throughout the breathing cycle, which helps to open the airways, improve oxygenation, and reduce the work of breathing. CPAP is commonly used in conditions such as congestive heart failure, COPD exacerbations, and severe asthma attacks. In this lesson, we'll cover the mechanism of action, indications, contraindications, proper setup, and monitoring of CPAP.

How CPAP Works

CPAP works by delivering constant positive pressure during both inhalation and exhalation. This helps keep the alveoli open, improving oxygenation and ventilation. It also helps reduce the patient's work of breathing. CPAP increases the functional residual capacity of the lungs, which is the volume of air left after normal exhalation. The pressure prevents the collapse of alveoli, ensuring better gas exchange. It also improves ventilation-perfusion matching, where air is directed to areas of the lung that are properly perfused with blood. Additionally, CPAP reduces preload and afterload in the heart, which can help in certain cardiac conditions.

Mechanism of Action of CPAP

CPAP improves the functioning of the lungs by maintaining positive pressure. It keeps alveoli open and maximizes gas exchange. In pulmonary edema, CPAP helps to push fluid from the alveoli into the pulmonary capillaries, allowing the alveoli to expand more easily. This improves the overall functioning of the lungs. CPAP also reduces diaphragm fatigue by decreasing the work of breathing, allowing for better oxygenation and improved ventilation. The mechanism is akin to inflating tiny balloons in the lungs to improve gas exchange.

Indications for CPAP

CPAP is indicated for several respiratory conditions, including:

Congestive Heart Failure with Pulmonary Edema: Helps push fluid from the alveoli, improving oxygenation.

COPD Exacerbations: Reduces the work of breathing and improves gas exchange.

Severe Asthma Attacks: Can help manage respiratory distress by providing better airflow and improving oxygenation.

Pneumonia: Improves gas exchange by keeping the alveoli open.

Near-Drowning: Enhances ventilation and oxygenation in patients who have inhaled water.
Always follow local protocols for specific indications, and consult medical direction when in doubt.

Contraindications for CPAP

While CPAP is effective, it is contraindicated in certain situations, including:

Respiratory Arrest: CPAP cannot be used effectively for patients who are no longer breathing and require more invasive ventilation.

Severe Decreased Level of Consciousness: Patients who are unconscious or cannot tolerate a mask may not benefit from CPAP.

Hypotension: CPAP can worsen hypotension, especially if systolic blood pressure is below 90 mmHg.

Active Vomiting or High Aspiration Risk: CPAP can increase the risk of aspiration in these patients.

Pneumothorax: Positive pressure could worsen a pneumothorax.

Facial Trauma: It may be difficult to achieve a proper seal for the mask, making CPAP ineffective.
Always be mindful of these contraindications and follow your local protocols.

CPAP System Components

CPAP systems consist of several key components:

CPAP Device or Generator: The machine that generates the continuous positive pressure.

Face Mask: Delivers the pressure to the patient, available in various sizes to ensure a proper fit.

Tubing: Connects the mask to the CPAP device and oxygen source.

Pressure Gauge: Allows you to monitor and adjust the pressure delivered to the patient.

Filter: Some systems include filters to clean the air before it reaches the patient.
Make sure you are familiar with the specific CPAP system used in your service as the components can vary between manufacturers.

Setting Up CPAP

Setting up CPAP involves several steps:

Assemble Equipment: Gather all necessary components, including the CPAP device, mask, tubing, and oxygen source.

Connect the CPAP to the Oxygen Source: Attach the device to the oxygen source and ensure the connection is secure.

Set the Initial Pressure: Start with 5-10 cm of water, but always follow local protocols for specific pressure settings.

Select Mask Size: Choose a mask that fits appropriately to ensure a good seal.

Patient Communication: Explain the procedure to the patient to reduce anxiety and encourage cooperation.

Apply the Mask: Ensure the mask fits well, with a good seal, and secure it comfortably on the patient's face.
Communication is key to ensuring the patient’s cooperation for CPAP success. Always monitor the patient’s comfort and adjust as necessary.

Monitoring CPAP Effectiveness

Once CPAP is in use, it’s critical to monitor the patient’s response:

Pulse Oximetry: Track oxygen saturation levels. CPAP should improve oxygen levels.

Respiratory Rate & Effort: Look for a reduction in respiratory rate and effort as CPAP takes effect.

Blood Pressure: Monitor regularly, as CPAP can affect hemodynamics, particularly blood pressure.

Heart Rate & Rhythm: Observe for any changes in heart rate or rhythm.

Mental Status, Skin Color, and Temperature: Keep an eye on these parameters for improvements.
If the patient’s condition worsens or doesn’t improve despite CPAP, be ready to switch to alternative ventilation support. Continuously reassess.

Issues During CPAP Administration

Several issues may arise when using CPAP:

Air Leaks: If the mask isn’t sealed properly, air can leak out, reducing effectiveness. Adjust the mask or try a different size.

Patient Discomfort or Claustrophobia: Patients may struggle with the mask due to discomfort. Reassure them and explain the benefits of the procedure.

Skin Breakdown: Extended use of the mask can cause skin irritation or breakdown, particularly on the bridge of the nose.

Hypotension: If blood pressure drops, reduce the pressure or discontinue CPAP.

Gastric Distension: Air can enter the stomach, causing discomfort and potential complications. Encourage the patient to burp if needed.

Equipment Malfunctions: Always have backup equipment and a backup plan in place.
Be proactive in troubleshooting and adapting your approach based on the patient's response.