Continuous Positive Airway Pressure

Anatomy and Physiology

Patients inhale air through the nose. Air passes through the nasopharynx, oropharynx, larynx, trachea, bronchi, bronchioles, and finally reaches the alveoli. Portions of the respiratory tract may become obstructed by excess tissue, tonsillar overgrowth, weakened musculature, fatty deposits, or secretions. The forced air delivered by CPAP helps keep the airways patent and prevent collapse.[2]

Indications

Airway collapse can occur from various causes, and CPAP helps maintain airway patency in many of these instances. This pathology is commonly seen in adults and children with obstructive sleep apnea (OSA), a condition marked by cessation or pauses in breathing during sleep. OSA can result from factors such as obesity, hypotonia, and adenotonsillar hypertrophy.

In the neonatal intensive care unit, CPAP is used to treat preterm infants with underdeveloped lungs and respiratory distress syndrome due to surfactant deficiency.[3][4] This therapy also helps manage hypoxia and reduce the work of breathing in infants with conditions such as bronchiolitis, pneumonia, or tracheomalacia, where the airways are collapsible.

CPAP aids in hypoxic respiratory failure related to congestive heart failure by improving cardiac output and enhancing V/Q matching. This treatment can also assist oxygenation via PEEP before endotracheal intubation and facilitate extubation in patients who still require positive pressure but do not need invasive ventilation. These benefits are particularly useful for conditions such as OSA in patients with obesity or congestive heart failure.

Contraindications

CPAP is unsuitable for individuals who are not spontaneously breathing. Patients with poor respiratory drive typically require invasive ventilation or noninvasive ventilation using CPAP, often in combination with additional pressure support and a backup rate (BiPAP). Relative contraindications for CPAP include the following:

• Lack of cooperation
• Anxiety
• Reduced consciousness or inability to protect the airway
• Unstable cardiorespiratory status or respiratory arrest
• Facial trauma or burns
• Recent facial, esophageal, or gastric surgery
• Air leak syndrome (eg, pneumothorax with bronchopleural fistula)
• Copious respiratory secretions
• Severe nausea and vomiting
• Severe air trapping diseases with hypercarbia (eg, asthma, chronic obstructive pulmonary disease)

CPAP is an effective therapy for managing various respiratory conditions, but proper patient selection is crucial to avoid complications. Careful consideration of contraindications ensures the safe and appropriate use of this therapy in clinical practice.

Equipment

CPAP therapy utilizes machines specifically designed to deliver a continuous flow of constant pressure.[5] Some CPAP machines include additional features, such as heated humidifiers, to enhance patient comfort. Key components of a CPAP machine include the interface for delivering pressure, which can vary based on the mask used.

CPAP may be administered through several interfaces. Nasal CPAP uses nasal prongs that fit directly into the nostrils or a small mask that covers the nose. Nasopharyngeal CPAP is delivered through a nasopharyngeal tube, an airway inserted through the nose with its tip terminating in the nasopharynx. This method bypasses the nasal cavity and delivers CPAP more distally. CPAP via a face mask involves a full mask covering both the nose and mouth, ensuring a secure seal. This interface is particularly useful for patients who breathe through their mouths or require preoxygenation before intubation while still breathing spontaneously. A CPAP machine also includes straps to secure the mask, a hose or tube connecting the mask to the machine’s motor, a motor that blows air into the tube, and an air filter to purify the air entering the nose.

Bubble CPAP is a mode of delivering CPAP used in neonates and infants, where pressure in the circuit is maintained by immersing the distal end of the expiratory tubing in water.[6] The depth of the tubing in the water determines the generated pressure (CPAP). Blended and humidified oxygen is delivered via nasal prongs or nasal masks. As the gas flows through the system, it "bubbles" through the expiratory tubing into the water, producing a characteristic sound. Pressures typically range from 5 to 10 cm H2O. Effective and safe use of the bubble CPAP system requires skilled nurses and respiratory therapists.

For patients using CPAP at home, regular use during overnight sleep and daytime naps is essential. Some CPAP units feature a timed pressure "ramp" setting, which starts airflow at a low level and gradually increases pressure to the set level, helping patients adjust more comfortably.

Preparation

In an out-of-hospital setting, patients on CPAP should initially be monitored in a sleep lab, where a technologist manually titrates settings to determine the optimal pressure for minimizing apnea. A sleep doctor or pulmonologist can assist in selecting the most comfortable mask, trialing a humidifier chamber, or using a different CPAP machine that offers multiple or autoadjusting pressure settings. Autotitrating CPAP machines employ computer algorithms and pressure transducer sensors to automatically adjust the pressure to the ideal level for eliminating apneic events.

Complications

The first few nights on CPAP may be challenging as patients adjust to the therapy. Many initially find the mask uncomfortable, claustrophobic, or embarrassing. Side effects of CPAP treatment can include congestion, a runny nose, dry mouth, or nosebleeds, with the use of humidification often alleviating these symptoms. Masks may cause skin irritation or redness. Using the correct size mask and adequate padding can help prevent pressure sores. The mask and tubing should be cleaned regularly, inspected, and replaced every 3 to 6 months. Abdominal distension or bloating may occur, which rarely leads to nausea, vomiting, and aspiration. These issues may be minimized by reducing pressure or performing gastric decompression through a tube in hospitalized patients.

Compliance

Despite the many benefits of CPAP therapy, compliance remains a significant challenge in both inpatient and outpatient settings. Physicians should closely monitor patient compliance, especially during the initiation of CPAP therapy, to ensure long-term success.[7] Patients must report any adverse effects that may limit compliance, which the physician should promptly address. Ongoing follow-up with an annual office visit is essential to check the equipment, adjust settings as needed, and ensure proper mask and interface fit. Continued patient education on the importance of regular use and involvement in support groups can help maximize the benefits of CPAP therapy.

In rare instances, hospitalized patients may greatly benefit from CPAP but may not tolerate the mask or comply due to delirium, agitation, or age-related factors in children or older adults. In these cases, mild sedation with low-dose fentanyl or dexmedetomidine can help improve compliance until CPAP therapy is no longer needed. However, close monitoring is critical, as sedatives or anxiolytics can decrease consciousness and respiratory drive. If adequate minute ventilation and oxygenation cannot be achieved, escalation to BiPAP or intubation with mechanical ventilation should be considered, in accordance with the patient’s code status and care goals.

Clinical Significance

CPAP is a widely used mode of PEEP delivery in both hospital and outpatient settings, including home therapy for sleep apnea.[8] The benefits of initiating CPAP treatment include improved sleep quality, a reduction or elimination of snoring, and decreased daytime sleepiness. Many patients report enhanced concentration, memory, and cognitive function. CPAP can also help alleviate pulmonary hypertension and reduce blood pressure. It is safe for patients of all ages, including children.

CPAP improves V/Q matching and helps maintain functional residual capacity. Unlike invasive mechanical ventilation, CPAP avoids complications such as excessive sedation and the risks of volutrauma and barotrauma. In the inpatient setting, CPAP therapy should be closely monitored with regular checks of vital signs, blood gases, and clinical status. If signs of deterioration appear, mechanical ventilation should be considered.

Enhancing Healthcare Team Outcomes

CPAP is commonly prescribed by primary care providers, nurse practitioners, internists, and neurologists for patients with OSA. However, good compliance hinges on thorough patient education. Many patients discontinue use due to discomfort after a short period. While CPAP is an effective temporary treatment for OSA, it does not reduce the risk of cardiac complications. Patients should also be encouraged to lose weight, adopt a healthy diet, quit smoking, and engage in regular exercise to improve overall health outcomes.[9]