Continuous Positive Airway Pressure (CPAP) therapy is the standard method for managing Obstructive Sleep Apnea (OSA), providing a steady stream of pressurized air to keep the airway open during sleep. The effectiveness of this therapy is measured by the Apnea-Hypopnea Index (AHI), which calculates the average number of breathing-related events—apneas (complete pauses) and hypopneas (partial obstructions)—that occur per hour of sleep. An AHI under five is generally considered successful treatment. A rising AHI signals that an underlying factor is compromising the pressure delivery or the physical integrity of your airway, indicating a decline in the therapy’s ability to maintain an open airway.
Mask Fit and Seal Integrity
For CPAP therapy to be effective, the physical interface between the user and the machine must maintain a perfect seal. Air leaks, whether around the mask’s edges or through the mouth, are a primary cause of an elevated AHI because they reduce the pressure delivered to the airway. Manufacturers often specify a maximum acceptable leak rate, such as 24 liters per minute for some nasal masks. Exceeding this threshold means the necessary therapeutic pressure is not reaching the throat.
Poor mask sizing is a frequent culprit, as a mask that is too large or too small struggles to form an airtight seal against the face. Over time, the materials forming the seal, particularly silicone cushions or nasal pillows, begin to degrade. These components absorb skin oils and stretch out, losing the firmness and elasticity required to maintain pressure. Replacing the cushion or pillow monthly is often necessary to prevent material degradation from causing significant leaks.
Strap tension also plays a role. Headgear that is too loose allows the mask to shift and break the seal, while headgear pulled too tight can distort the silicone cushion, leading to leaks or causing discomfort that disrupts sleep. If the mask frame itself is old, it may become brittle or lose its shape, which further compromises the overall fit. Regular inspection for visible tears, stiffness, or discoloration in all mask components is necessary to ensure optimal pressure delivery.
Machine Settings and Component Maintenance
Issues originating within the CPAP device or its components can contribute to a rising AHI by restricting airflow or decreasing functional pressure. The air filter, which traps dust, pollen, and other fine particles, should be changed monthly. A clogged filter restricts air intake, forcing the machine to work harder and reducing its efficiency in delivering the set pressure.
Condensation, known as “rainout,” occurs when warm, humidified air cools inside the tubing, causing water droplets to form. This water can lead to gurgling sounds, splash onto the face, and create discomfort. Such discomfort often causes the user to inadvertently remove the mask or shift position, halting therapy. Using a heated tube or adjusting humidity settings can mitigate this effect, but the presence of water itself disrupts continuous airflow.
Beyond maintenance, the therapeutic pressure setting may become inadequate due to the natural progression of the underlying condition. The pressure prescribed during the initial sleep study is a snapshot in time and may no longer be sufficient to keep the airway open years later. A re-evaluation of the pressure setting is necessary if a patient notices a sustained increase in AHI. This is also true if there is an accidental alteration to pressure relief features, such as Expiratory Pressure Relief (EPR) or C-Flex, which momentarily lower the pressure during exhalation.
Personal Health and Lifestyle Shifts
Changes in personal health and daily habits can directly alter the severity of Obstructive Sleep Apnea, increasing the pressure needed to maintain a clear airway and elevating the AHI. Weight fluctuation is a significant factor. Gaining weight often results in fat deposits accumulating around the neck and upper airway, which increases the likelihood of tissue collapse during sleep. This physical change means the current CPAP pressure is no longer high enough to counteract the increased resistance in the airway.
The consumption of certain substances can profoundly affect muscle tone in the throat. Alcohol acts as a central nervous system depressant, relaxing the muscles and making the airway more prone to collapse, leading to an average increase of about four apnea events per hour. Similarly, new prescription medications, particularly sedatives, muscle relaxers, or narcotic pain medicines, have a comparable effect by depressing the reflexes that normally help keep the airway open.
Acute physical health issues, such as nasal congestion from seasonal allergies or a common cold, can force the user to breathe through their mouth. This compromises the seal of a nasal mask and decreases effective pressure. Positional changes during sleep are another common variable. Many individuals experience more frequent obstructive events when sleeping on their back due to gravity pulling the tongue and soft palate backward. Addressing these variables often requires consulting a healthcare provider to determine if a new sleep study or pressure titration is necessary.