Intelligent CPAP systems: clinical experience.

Nasal continuous positive airway pressure (CPAP) remains the treatment of choice for obstructive sleep apnoea (OSA) syndrome. It is believed to work by pneumatically splinting the upper airway. 2 As the pressure is gradually increased the subject passes through a spectrum of gradually decreasing severity of obstruction. 4 Frankobstructiveapnoeas,hypopnoeas, and desaturation first disappear, then 2–4 cm H2O higher snoring and most respiratory arousals disappear, leaving only silent inspiratory airflow limitation associated with high respiratory work. This occurs at an average pressure of 8 cm H2O. A further increase of 2 cm H2O produces a 75% reduction in respiratory work and normal breathing. A higher pressure is required to prevent apnoeas in REM sleep and in the supine position, and the lowest pressure is required in slow wave sleep in the lateral position. Although nasal CPAP has no serious side eVects in subjects with uncomplicated sleep apnoea syndrome, there are several minor side eVects that reduce patient compliance and quality of life. These are chiefly pressure related, the most frequent being dryness, burning, and congestion of the nasal mucosa, discomfort exhaling against the pressure, chest wall discomfort, middle ear discomfort, mask and machine noise, conjunctivitis from leaks into the eyes, and air swallowing. The first goal of treatment initiation is therefore a “pressure titration” to find a pressure that makes a reasonable trade-oV between increasing eVectiveness at eliminating respiratory related events and avoiding unpleasant side eVects. Current practice is to perform the titration in the laboratory with full polysomnography, gradually increasing the pressure through the spectrum described above, in all body positions and sleep stages. This is skilled, tedious, and expensive work. Furthermore, it is controversial whether the pressure determined in this way will still be correct in a month or a year’s time after resolution of upper airway trauma and sleep deprivation, or with cold dry weather, seasonal allergy, or ingestion of alcohol. 6 11 14 15 Auto-titrating systems provide a method for determining a single fixed pressure, suitable for subsequent long term home treatment with a conventional CPAP device. Their goal is to avoid the cost and labour of a manual titration. Conversely, auto-adjusting systems are intended for long term home treatment. Their goal is to improve eVectiveness and/or reduce side eVects by ensuring that the instantaneous pressure is always close to optimal. 16 This paper will concentrate on experience at the Ruhrlandklinik using AutoSet Clinical, an in-laboratory auto-titrating system, and AutoSet Portable which can be used either as an auto-titrating or an auto-adjusting system (ResMed, Sydney).