A manual CPAP machine delivers continuous positive airway pressure with a consistent fixed level of pressure to stent open the upper airway during sleep for a patient with obstructive sleep apnea. Manual CPAP machines are also called fixed pressure machines for CPAP. The amount of air pressure needed for effective sleep therapy varies by person and is a value prescribed by the physician after a sleep study. The pressure is measured in centimeters of water pressure (cmH20). The typical manual CPAP machine can deliver pressure settings between 4 cmH20 and 20 cmH20.
A flow generator inside the manual CPAP machine pulls in air from the room. The air is pressurized and sent back out through a tube to the CPAP mask or nasal pillows worn by the patient. The manual CPAP machine monitors the pressure and adjusts the output of flow to maintain a consistent pressure equal to the prescribed CPAP amount. Flow rates are higher to achieve higher pressures and reduced for lower pressures.
Dryness in the mouth and nose, difficulty falling asleep, and trouble tolerating the forced air flow are the most common complaints from CPAP users. CPAP machines are smarter than ever today, and many have features to eliminate or reduce these side effects to CPAP therapy for sleep disorders. CPAP machines differ in size, range of noise output, and by the types of features they have for reducing potential complications and barriers to consistent, effective CPAP use. Machines also differ in what data they capture and how that data is stored and retrieved for use by you or by you and your physician.
A ramp setting creates a deliberate lag between the time when the machine is turned on and when the full prescribed pressure is delivered. The ramp gives the patient time to get in bed, read, watch TV, or do a crossword puzzle before the full flow starts. The intentional lag may make it easier to get to sleep.
A ramp feature is commonplace on manual CPAP machines but how it works varies by model. Some machines have a preset ramp time while other models let the patient set the timer. On some CPAP devices, the ramp phase may be gradual: the pressure initializes very low and rises incrementally over the set period. On other machines, the pressure stays dormant until the device detects an airway obstruction. The machine uses the detected obstruction as the signal to ramp up to the ordered pressure level.
Although manual CPAP devices intentionally provide a fixed level of pressure, some models include an option to reduce the pressure toward the end of an exhalation, just before an inspiration. This drop-in pressure may make it more comfortable for the patient to take the next inward breath. Although CPAP does not push air in during inspiration, some people find it uncomfortable to breathe in when there is a constant flow of air. This sensation can be particularly troubling when the amount of needed pressure is in the higher ranges.
By monitoring the patient’s expiratory flow rate, these smart machines taper the pressure down just before inspiration to make it easier to inhale. As soon as it senses the patient is about to exhale, it flexes back up to the ordered CPAP level. For example, if the ordered CPAP level is 12 cmH20, the machine may drop the pressure to 10 cm H2O at the end of exhalation.
Oral and nasal dryness, hoarseness, and nose bleeds are potential CPAP complications. Humidification can prevent or remedy these concerns. Heated humidifiers may be built into a CPAP machine or available for purchase separately. Without humidification, the flow from the CPAP machine tends to be cool and dry. Humidifiers warm up the air and saturate it with water vapor.
Some machines maintain the humidity rate and air temperature at a fixed point, while others provide ambient monitoring and adjust the humidity and temperature level up or down to best meet the need in the moment. The dynamic adjustment helps reduce an effect known as “rain out,” which occurs when warm, humidified gas cools as it travels through the tubing to the patient. Some machines have heated tubing to help minimize condensation accumulation. Humidifiers require sterile water. On some units, the user pours water into the humidifier. Other machines have detachable containers.
Most brands of masks function well with any brand of CPAP machine. Some machines, however, have software that takes input regarding the mask in use. The machine then automatically compensates flow delivery using information about that mask’s design and leak profile. This feature may make it easier to get a good fit with a mask. Generally, this type of leak compensation requires that the patient chooses a mask that is compatible with the software.
Manual CPAP machines all have alarms that emit audible alerts if it is having difficulty maintaining the set pressure. These alarms are most often related to the mask leaking too much. These alarms may also go off if the patient has pulled off the mask or blocked the exhalation ports on the mask. Machines differ in how wide a variance they allow or how long the delay is before the alert sounds.
Some machines include a leak test option that allows the patient to run a test with the mask on to see if the leaks around the face and mask are sufficiently sealed.
All CPAP equipment tracks some data regarding usage, but there is considerable variation in what information is recorded and tracked and how it is retrieved. Increasingly, machines use a wireless connection to upload data to the internet or a smartphone application. Machines that do not have a wireless connection may have data retrieval via an SD card or USB port. The data may include things like how often the CPAP was in use and whether the patient had obstructive or apneic events despite wearing the CPAP. You or your physician can look at the data to determine if the ordered CPAP parameters are working for you. Some machines integrate with smartphone applications both for data capture and sharing and for setting adjustments.
CPAP machines of all types need a stable location near the bed with easy access to a power supply. The machine should be flat and not easily jostled. The CPAP user must make sure the CPAP tubing reaches their bed space without difficulty. Longer hoses are usually available for purchase if needed.
CPAP machines pull air in from the room through a filter that removes dust and other particles. The filter needs to be replaced as recommended to prevent device obstructions and failures. The hose or tubing requires daily cleaning. The humidifier also requires cleaning and sterile water replenished. Follow the manufacturer’s recommendations for cleaning and part replacements. Adhering to the recommendations keeps the user healthy and prolongs the life of the machine.
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