Intelligent CPAP systems: clinical experience

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Abstract
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.1 2 As the pressure is gradually increased the subject passes through a spectrum of gradually decreasing severity of obstruction.3 4 Frank obstructive apnoeas, 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.5 Although nasal CPAP has no serious side effects in subjects with uncomplicated sleep apnoea syndrome, there are several minor side effects 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.6-11 The first goal of treatment initiation is therefore a “pressure titration” to find a pressure that makes a reasonable trade-off between increasing effectiveness at eliminating respiratory related events and avoiding unpleasant side effects.12 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.13 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 …

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