Continuous Positive Airway Pressure (CPAP) is often confused with medical oxygen therapy. While CPAP delivers air, its primary mechanism and goal are fundamentally different. This distinction centers on mechanical support using pressure versus gas supplementation using concentration. Understanding how each device functions is necessary to clarify their respective roles in respiratory care.
How CPAP Works: Focusing on Air Pressure
CPAP therapy operates by delivering a constant stream of pressurized air to the user’s upper airway. The machine draws in ambient air from the room, filters it, and pressurizes it to a specific setting prescribed by a doctor. This mechanical force acts like a pneumatic splint, preventing the soft tissues in the throat from collapsing during sleep. The primary purpose of CPAP is to maintain an open airway, addressing the physical issue underlying conditions like Obstructive Sleep Apnea (OSA).
The treatment’s effectiveness relies entirely on this continuous positive pressure, measured in centimeters of water (cmH2O). By mechanically keeping the airway open, the user is able to breathe normally, which allows for efficient gas exchange and prevents the drops in blood oxygen levels that characterize apnea events. Since the machine uses standard room air, it does not increase the concentration of oxygen delivered. The therapy is mechanical, addressing an anatomical obstruction, rather than a chemical treatment focused on gas composition.
Medical Oxygen Therapy: Focusing on Gas Concentration
Medical oxygen therapy, in contrast to CPAP, is a prescribed medication focused on increasing the concentration of oxygen inhaled by the patient. This treatment specifically addresses hypoxemia, a condition involving low blood oxygen levels caused by underlying medical issues. Conditions such as Chronic Obstructive Pulmonary Disease (COPD), severe pneumonia, or heart failure often compromise the body’s ability to efficiently transfer oxygen from the lungs to the bloodstream.
Oxygen delivery devices, such as oxygen concentrators, filter room air to remove nitrogen, creating a gas mixture enriched with 87% to 93% pure oxygen. This highly concentrated gas is delivered through a nasal cannula or mask to boost the blood’s oxygen saturation to a healthy range (typically 94% to 96%). The therapy’s goal is purely chemical, supplementing the body’s gas levels to ensure all organs receive adequate oxygen. It does not provide the positive pressure required to physically support the airway.
Combining CPAP and Oxygen: Separate Treatments Working Together
Although CPAP is not oxygen therapy, the two treatments can be combined when a patient has two distinct medical needs. A person may require CPAP to prevent upper airway collapse from sleep apnea and also need supplemental oxygen due to a coexisting condition, such as advanced lung disease. This combined approach is frequently used for patients with “overlap syndrome,” a diagnosis involving both OSA and COPD.
When combined, the CPAP machine continues to provide the necessary pressure for airway patency, while a separate oxygen source is introduced into the circuit. This is typically accomplished using a small connector, often called a “bleed-in” adapter, which attaches to the CPAP tubing or mask. The oxygen from the external source is then bled into the stream of pressurized air. This integration demonstrates that CPAP acts as the delivery vehicle for pressure, and the concentrated oxygen is a distinct additive, confirming they are separate therapies utilized in tandem.