Obstructive Sleep Apnea (OSA) is treated using Positive Airway Pressure (PAP) devices. This therapy delivers a stream of pressurized air through a mask to mechanically hold the upper airway open, preventing obstruction. Although CPAP (Continuous Positive Airway Pressure) is often used generically, it is only one of several distinct types of devices available. Understanding the functional differences between these machines is important for effective treatment, as each addresses specific patient needs and breathing patterns.
Standard Continuous Positive Airway Pressure
The standard CPAP machine is the foundational technology in PAP therapy, delivering a single, fixed pressure setting of air throughout the entire night. This constant pressure is determined during a titration study, which identifies the minimum pressure required to keep the airway open. The pressure, measured in centimeters of water (cm H₂O), remains constant during both inhalation and exhalation. This fixed delivery consistently splints the airway open, effectively eliminating apneas and hypopneas for many individuals with mild to moderate OSA. Some CPAP devices include a “ramp” feature, which starts at a low pressure and gradually increases to the prescribed setting.
Automatic Positive Airway Pressure Devices
Automatic Positive Airway Pressure (APAP) devices, or auto-CPAP, do not deliver a single fixed pressure. Instead, APAP machines use built-in sensors and algorithms to continuously monitor breathing patterns and airway resistance in real-time. This allows the machine to automatically adjust the pressure level throughout the night within a prescribed minimum and maximum range. The machine raises the pressure only when it detects an obstructive event, such as snoring, and lowers it once the airway is stable again. This dynamic adjustment ensures the user receives only the pressure needed, often resulting in a lower average pressure compared to fixed-pressure CPAP.
BiLevel Positive Airway Pressure Devices
BiLevel Positive Airway Pressure (BiPAP) devices deliver two distinct pressure settings. This device provides a higher pressure for inhalation, known as Inspiratory Positive Airway Pressure (IPAP), and a lower pressure for exhalation, called Expiratory Positive Airway Pressure (EPAP). The difference between these two pressures is known as pressure support, which assists the user’s breathing effort. The lower EPAP setting is beneficial for patients who struggle to exhale against the high fixed pressure of a standard CPAP machine, reducing the work of breathing. BiPAP devices are commonly reserved for individuals with more severe OSA, those requiring higher overall pressures, or patients with other respiratory conditions like COPD or Central Sleep Apnea.
Factors Influencing Device Selection
The selection of a specific PAP device relies heavily on the individual’s diagnostic results and clinical needs. The Apnea-Hypopnea Index (AHI), which measures breathing events per hour, is a primary factor in determining OSA severity and guiding the initial choice of therapy. Patient tolerance for the pressure and the presence of other medical conditions also play a role. The prescribing physician or sleep specialist considers which device mechanism is most likely to achieve therapeutic success and ensure patient adherence. Non-functional factors, such as the need for integrated heated humidification or a compact device for frequent travelers, also influence the final selection.