POSITIVE PRESSURE THERAPY

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Since its first description in 1981, considerable advances have been made in systems used to deliver positive airway pressure for the treatment of patients with obstructive sleep-disordered breathing (OSDB).101 The present generation of machines uses microprocessors and are small, quiet, and easily portable to facilitate their use while traveling. The software in many of the newer generation machines allows for the objective assessment of patient compliance by monitoring both the total time on and time at the prescribed pressure. Positive pressure can be delivered at a fixed pressure throughout the breathing cycle, as in the case of continuous positive airway pressure (CPAP), at two different fixed pressures in response to inspiration and expiration, as in bilevel pressure, or at a variable positive pressure in response to changes in airflow or snoring sounds, as is the case in autotitrating systems.98

Most machines can be run on European or North American electrical current, and off alternate power sources such as a car battery. The nasal and oronasal interfaces that are available incorporate a variety of materials and designs. The newer masks provide patients with improved fit and comfort. Positive airway pressure remains the initial medical treatment of choice for the sleep apnea/hypopnea syndromes.98 It has essentially eliminated the need for emergency tracheostomy in patients with obstructive sleep apnea (OSA).

In this article we discuss the utility of positive airway pressure in OSDB—its mechanism of action, benefits, and complications. We review the important topic of compliance and discuss current approaches to improve the long-term use of this highly effective treatment modality. Finally, we will offer our perspective on the future of positive airway pressure therapy for OSDB.

Section snippets

Mechanism of Action

CPAP systems consist of a blower unit that generates and directs airflow downstream to the patient. The positive pressure is generated by variations in delivered airflow and resistance in the system. When CPAP is delivered by way of a nasal interface, the soft palate seals against the tongue, resulting in a pressurized upper airway (Fig. 1). Pressure is maintained by increasing airflow in response to small leaks, involving the mask or mouth. The collapsible region of the upper airway is

BILEVEL POSITIVE AIRWAY PRESSURE

Previous work by a number of investigators75, 79, 85, 94 has shown that upper airway resistance increases during expiration despite the absence of negative intrapharyngeal pressure accompanying inspiration. Sanders et al79 subsequently speculated that the instability of the upper airway during expiration is the initial event in the sequence leading to obstructive apnea. Mahadevia et al49 further substantiated that concept by demonstrating that apnea frequency could be reduced by the application

VARIABLE (AUTOTITRATING) CPAP

The pressure required to stabilize the upper airway during sleep is influenced by several factors, including body position, sleep stage, sleep deprivation, sedatives, and alcohol. * It would appear to be theoretically advantageous to use a positive-pressure device that would raise and lower the pressure delivered in response to those conditions. A number of positive-pressure devices that provide variable

SPECIAL CONSIDERATIONS

Patients with OSDB treated with positive airway pressure should be re-evaluated at regular intervals to reinforce the importance of continued treatment, assess compliance and response to treatment, and address any side effects or complications of the therapy. In patients who complain of persistent daytime sleepiness, an objective evaluation of machine use should be obtained prior to repeat polysomnography. That can be accomplished easily by securing an hour “meter read” of machine use. Most

FUTURE DIRECTIONS

Considerable advances have been made in our understanding of positive airway pressure therapy for OSDB. A wide variety of masks are available that improve patient comfort and acceptance of the interface. The current generation of CPAP and bilevel positive airway pressure systems is relatively quiet, highly portable, and durable. Compliance should be monitored objectively in all patients treated chronically with positive airway pressure. As is the case with any chronic disease, it is clear that

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    Address reprint requests to Patrick J. Strollo, Jr, MD University of Pittsburgh School of Medicine Division of Pulmonary, Allergy and Critical Care Medicine 3459 Fifth Avenue, Suite S-643 Pittsburgh, PA 15213

    Supported in part by Department of Veterans Affairs Medical Center and NHLBI Training Grant NHLBI2T32HL0756311A2.

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