[Nasal CPAP therapy of obstructive sleep apnea syndrome with expiratory pressure reduction: a prospective randomized study of acceptance of treatment during therapy initiation].

It is often difficult to achieve adequate acceptance of nasal continuous positive airway pressure (CPAP) therapy by patients with OSA. Many patients find it particularly inconvenient to expire against the treatment pressure. With this in mind, we have attempted to improve acceptance of CPAP therapy by using a bilevel system that reduces the treatment pressure during expiration. 52 patients were randomized either to initial treatment with CPAP therapy followed by bilevel treatment, or to treatment in reversed order. During bilevel therapy the ratio of inspiratory to expiratory pressure was fixed at 1:0.6. After each treatment the patients were interviewed on the basis of visual analogue scales to establish their subjective evaluation of such parameters as general well-being, quality of sleep, comparison of the respective treatment pressures, and possible preference for one of the two systems for long-term treatment. The minimal effective inspiratory treatment pressure during bilevel therapy (IPAP) and the minimal effective CPAP pressure were closely correlated (r = 0.89). There was no difference between the apnoea hypopnoea indices during CPAP therapy as compared with bilevel therapy. Most patients (57%) felt the treatment pressure with the bilevel system to be lower (p = 0.048). There were no differences in patients' well-being early in the morning, or in their assessment of sleep quality. The majority of patients (52%) preferred bilevel therapy for long term treatment, while 38% preferred CPAP therapy (n.s.). In a subgroup of 13 patients with a treatment pressure of > or = 10 mbar during CPAP therapy 10 patients (77%) gave preference to the bilevel system (n.s.). In a considerable number of patients the acceptance of treatment can be improved by using a bilevel system for initiation of nasal positive pressure therapy.