Automatic CPAP Machine and Fixed Pressure CPAP Machine Compared
POSTED 02 Oct 2015

CPAP therapy is so far your best option if you have been diagnosed with obstructive sleep apnoea. There are two types of CPAP machine and your choice depends on the device recommended by your doctor.

CPAP Machine Types

There are two types of CPAP machine available for therapy and they are automatic pressure machine and fixed pressure machine.
An APAP or automatic CPAP device has a range of built-in sensors that calculates the required pressure level of the patient at any given time. This device can detect when a patient is about to stop breathing so that it raises the pressure of the machine automatically to make sure that patient’s airway remains open. When the patient’s breathing returns to normal, the air pressure automatically decreases. With an APAP, a patient is afforded less air pressure during therapy which makes for a more restful and peaceful sleep.

A fixed pressure machine is set at the recommended pressure level all the time. The pressure must be prescribed by a qualified doctor based on his findings. In most cases, the prescribed pressure changes over time because factors such as losing or gaining weight can readily affect the patient’s level of OSA severity thus making changes in the required CPAP therapy pressure.

Which is better: CPAP orAuto-PAP?

CPAP machines are generally calibrated to create a pressure that starts from 4cm/H2O to 20cm/H20. Most of the CPAP machines in the market today have ramp up feature that makes it easier for new users to adapt to the therapy. This ramp up feature starts the machine at a very low level then as the minutes tick by, the pressure gradually increases to the recommended level for the rest of the entailed therapy. The ramp up time takes less than 20 minutes to reach the recommended pressure level.

An auto-CPAP machine has the same operational range as the CPAP device, with the pressure gradually leveling up to the patient’s requirement as he enters into the different stages of sleep. The deeper the sleep, the more relaxed a person becomes thus making him more susceptible to events of breathing cessation. If this is the case, an auto-APAP machine should be the preferred choice. An APAP machine is programmable to work the same way as a fixed-pressure CPAP. This is more ideal as the doctor can virtually determine which device works best for his patients.

An Auto-CPAP machine can be adjusted to a minimum and maximum pressure. If the required air pressure range is 8cm/H2O to 12cm/H2O, the device will maintain that pressure all through therapy. Note though that a too low pressure might trigger episodes of apnoea. In this case, the pressure level must be increase to therapeutic level.
CPAP and APAP machines might leak during therapy thereby affecting the efficiency of the machine. Regular use of either fixed-pressure CPAP or APAP may cause stuffy nose and dry mouth to the patient.


Based on a study conducted by the Respiratory Sleep Disorders Unit of St. Vincent’s University Hospital in Ireland, CPAP and APAP therapies are equally efficient in the long term management and treatment of mild to moderate OSA patients.

If you have been diagnosed with OSA, call us now so we can discuss the possible course of treatment for you.

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