Positive airway pressure

A typical CPAP machine houses the air pump in a case lined with sound-absorbing material for quieter operation. A hose carries the pressurized air to a face mask that encloses the oral and nasal airways.

Positive airway pressure (PAP), also known as "continuous positive airway pressure" (CPAP), is a method of respiratory ventilation used primarily in the treatment of sleep apnea. A CPAP machine delivers air into your airway through a specially designed mask. The mask does not breathe for you; it increases air pressure in your throat so that your airway does not collapse. CPAP is considered the most effective nonsurgical treatment for the alleviation of snoring and obstructive sleep apnea.

Before the invention of the CPAP machine, a recommended course of action for a patient with sleep apnea or habitual snoring was a tracheostomy (tracheotomy).

With A CPAP machine, the pressure delivered into the airway is continuous during both inspiration and expiration. BiPAP differs from CPAP in that the pressure during expiration may be adjusted separately from the pressure delivered during inspiration.

CPAP is not a cure; it must be used every night for life. The first few nights of using CPAP tend to be difficult. The most common problem with CPAP is that people do not use the machine every night, or they take off the mask during the night because it becomes uncomfortable. Non-compliant patients experience a full return of obstructive sleep apnea and related symptoms.

Machine

A CPAP machine is used mainly by patients for the treatment of sleep apnea at home. Obstructive sleep apnea occurs when the the upper airway becomes narrow as the muscles relax naturally during sleep. This reduces oxygen in the blood and causes arousal from sleep. The CPAP machine stops this phenomenon by delivering a stream of compressed air via a nose or full-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 prescribed pressure (also called the titrated pressure). The necessary pressure is usually determined by a sleep physician after review of a study supervised by a sleep technician during an overnight study (polysomnography) in a sleep laboratory.

CPAP treatment can be highly effective in treatment of obstructive sleep apnea. For some patients, the improvement in the quality of sleep and quality of life due to CPAP treatment will be noticed after a single night's use.

Prospective CPAP candidates are often reluctant to use this therapy, since the nose mask and hose to the machine look 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, and some discontinue treatment entirely.

Types

• Fixed-pressure CPAP (Continuous Positive Airway Pressure) provides one constant pressure to the patient
• APAP or AutoPAP or AutoCPAP (Automatic Positive Airway Pressure) automatically titrates, or tunes, the amount of pressure delivered to the patient to the minimum required to maintain an unobstructed airway on a breath-by-breath basis by measuring the resistance in the patient's breathing, thereby giving the patient the precise pressure required at a given moment and avoiding the compromise of fixed pressure.
• VPAP™ or BiPAP® (Variable/Bilevel Positive Airway Pressure) provides two levels of pressure: one for inhalation (IPAP) and a lower pressure during exhalation (EPAP)
• xPAP ST (Spontaneous Time) is a machine that forces a number of set breaths per minute and is used to treat patients with central apneas.

Components

• Flow generator (PAP machine) provides the compressed air
• Hose connects the flow generator (sometimes via a humidifer) to the inferface
• Interface (mask) provides the connection to the user's airway

Optional features

• Humidifier adds moisture to the air
  • Heated: Heated water chamber that can increase patient comfort by eliminating the dryness of the compressed air. The temperature can usually be adjusted or turned off to act as a passive humidifier if desired.
  • Passive: Air is blown through an unheated water chamber and is dependent on ambient air temperature. It is not as effective as the heated humidifier described above, but can increase patient comfort by eliminating the dryness of the compressed air.
• Ramp is used to temporarily lower the pressure to allow the user to fall asleep more easily. The pressure gradually rises to the prescribed level over a period of time that can be adjusted by the patient and/or the DME provider.
• Exhalation pressure relief: Gives a short drop in pressure during exhalation to reduce the effort required. This feature is known by the trade name C-Flex® in some PAPs made by Respironics and EPR™ in ResMed machines.
• Data logging records basic compliance info or detailed event logging, allowing the sleep physician (or patient) to download and analyze data recorded by the machine to verify treatment effectiveness.

Such features generally increase the likelihood of PAP tolerance and compliance.

Care and maintenance

As with all durable medical equipment, proper maintenance is essential for proper functioning, long unit life and patient comfort. The care and maintenance required for PAP machines varies with the type and conditions of use, and are typically spelled out in a detailed instruction manual specific to the make and model.

Most manufacturers recommend that the end user perform weekly maintenance. Units must be checked regularly for wear and tear and kept clean. Worn or frayed electrical connections may present a shock or fire hazard; worn hoses and masks may reduce the effectiveness of the unit. Most units employ some type of filtration, and the filters must be cleaned or replaced on a regular schedule. Hoses and masks accumulate exfoliated skin, particulate matter, and can even develop mold. Humidification units must be kept free of mold and algae. Because units use substantial electrical power, housings must be cleaned without immersion.

Portability

Since continuous compliance is an important factor in the success of treatment, it is of importance that patients who travel have access to portable equipment. Progressively, nPAP units are becoming lighter and more compact, and often come with carrying cases. Dual-voltage power supplies permit many units to be used internationally. Battery operation allows the equipment to be used in remote areas.

Air travel presents special considerations. Most airport security inspectors have seen the portable machines, so screening rarely presents a special problem. Increasingly, machines are capable of being powered by the 400 Hz power supply used on most commercial aircraft and include manual or automatic altitude adjustment.

Some patients on PAP therapy also use supplementary oxygen. When provided in the form of bottled gas, this can present an increased risk of fire and is subject to restrictions. As of November, 2006, most airlines permit the use of oxygen concentrators.

Availability

In many countries, PAP 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 PAP 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 United States, PAP machines are often available at large discounts online, but a patient purchasing a PAP personally must handle the responsibility of securing reimbursement from his or her insurance Medicaid. Many of the internet providers that deal with insurance such as Medicare will provide upgraded equipment to a patient even if he or she only qualifies for a basic PAP. 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 PAP device.
• In the United Kingdom, PAP machines are available on National Health Service prescription after a diagnosis of sleep apnea or privately from the internet provided a prescription is supplied.
• In Australia, PAP machines can be bought from internet or physical stores on the provision of a prescription from a doctor. Low-income earners who hold a Commonwealth Health Care Card should enquire with their state's health department about programs that provide free or low-cost PAP machines. Those who have private health insurance are usually eligible for a partial rebate on the cost of a CPAP machine. Superannuation may be released for the purchase of essential medical equipment such as PAP machines, on the provision of letters from two doctors, one of whom must be your specialist, and an application to the Australian Prudential Regulation Authority (APRA).