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Continuous positive airway pressure (CPAP) is a method of respiratory ventilation used primarily in the treatment of sleep apnea, for which it was first developed. CPAP ventilation can also be used during the "weaning off" period of a ventilated intensive care patient, in exacerbations of chronic obstructive pulmonary disease (COPD), pulmonary edema and other settings of respiratory failure.
CPAP Machine
A device called a CPAP machine is used mainly by patients at home for the treatment of sleep apnea. In sleep apnea, the patient's airway becomes restricted as their muscles relax naturally during sleep, which causes arousal from sleep. The CPAP machine stops this phenomenon by delivering a constant stream of compressed air via a face mask and hose, splinting the airway (keeping it open under air pressure) so that unobstructed breathing becomes possible, reducing and/or preventing apneas and hypopneas.
The CPAP machine blows air at a set pressure (called the titrated pressure), usually programmed into the machine by a sleep technician during an overnight study in a sleep laboratory. This is the pressure of air at which most (if not all) apneas and hypopneas have been prevented, and is usually measured in centimetres of water cm/H20. CPAP treatment is highly effective in treating obstructive sleep apnea, although sometimes only partial improvement results. The other recognised type of sleep apnea (caused by central apnea) cannot be treated using CPAP.
Prospective CPAP candidates are often reluctant to use this therapy, since the face mask and hose to the machine looks uncomfortable and clumsy, and the airflow required for some patients can be vigorous. Some patients adjust to the treatment within a few weeks, others struggle for longer periods. This is usually directly in proportion to the amount of support they are given from their DME (Durable Medical Equipment) Provider, or how much support they seek out on their own. Air humidifiers (which increase patient comfort by eliminating the dryness of the compressed air) can be easily added to the patient breathing circuit of most CPAP machines, generally increasing the likelihood of CPAP tolerance and compliance. The improvement in the quality of sleep due to CPAP treatment will often be noticed after a single night's use.
The latest CPAP machines are smaller, lighter, and much less noisy than older versions. Additionally, more sophisticated models of CPAP machine are coming onto the market for home use, the most popular of which is the auto-titrating CPAP, also known as Intelligent CPAP (iCPAP), or AutoPAP (APAP). This type of machine uses a pressure sensor to enable the machine to alter the CPAP pressure on a breath-by-breath basis by measuring the resistance in the patient's breathing, thus giving the patient exactly the pressure they need at a given moment and avoiding the compromise of fixed pressure CPAP. The iCPAP usually has the capability to record a great deal of information which can be downloaded and analysed by a sleep physician to ensure the treatment is having the desired effect. Currently, auto-titrating CPAP machines cost around 3-4 times that of a conventional fixed pressure machine, but as manufacturing costs come down it is more than likely that this type of machine will become prevalent.
CPAP has also been used to prevent premature infants from going into respiratory failure thereby preventing the need for intubation. Chung CM. (1978) CPAP in infants with idiopathic respiratory distress syndrome. Mod Med Asia. 1978 May;14(5):26-30. *
Travelling with CPAP
Few airport inspectors have not seen the portable machines, so travel with them is not a problem, although the airline should always be consulted before attempting travel with a CPAP machine, mainly because if the passenger is on a long haul flight, they will need to be seated close to a power outlet - the latest machines are capable of being powered by the 400 Hz power supply used on most commercial aircraft. Supplementary oxygen, sometimes prescribed for use with a CPAP machine, can cause problems with some airlines who are hesitant to allow travel with oxygen bottles in the cabin, due to the increased risk of fire.
Availability
CPAP machines are only available by prescription. A sleep study at an accredited sleep lab is usually necessary before treatment can start. This is because the pressure settings on the CPAP machine must be tailored to a patient's treatment needs. A doctor, who may be a Respiratory Medicine, Ear Nose and Throat (ENT) or Neurology specialist, will interpret the results from the initial sleep study and estimate the correct pressure from experience. This is later confirmed with a follow up sleep study during which the patient wears the CPAP mask and pressure is adjusted up and down from the prescribed setting to find the optimal setting.
In the U.S., CPAP machines are available at large discounts online. Usually the online retailers will be able to work with insurance providers, Medicare or Medicaid. In some locations a government program, separate from Medicare, can be used to claim a reimbursement for all or part of the cost of the CPAP device.
In the UK, CPAP machines are available on NHS prescription after a diagnosis of sleep apnea.
References
See also
Intensive care medicine | Medical equipment | Medical treatments | Pulmonology
"Continuous positive airway pressure"