Randomized Cross-over Trials of the Effect of Heated Humidified CPAP Versus Non-humidified CPAP on Nasal Physiology

Introduction-Rationale:

Nasal continuous positive airway pressure (CPAP) is considered to be the "gold standard" of obstructive sleep apnoea (OSA) treatment [1]. The most common side effects are nasal congestion, stuffiness or dryness and rhinorrhea which have been reported in up to 68% of patients responding to a questionnaire about nasal CPAP. In many of them, CPAP compliance is accordingly compromised.

The mechanisms by which CPAP provokes nasal symptoms have been thoroughly studied only in healthy volunteers and a rodent model. Indeed, Richards et al demonstrated that mouth leaks causing high unidirectional nasal airflow increased nasal airway resistance and this response could be largely prevented by heated humidification of the inspired air. Similarly, Togias et al showed an elevated release of inflammatory mediators (histamine, prostaglandin D2, kinins) in nasal wash fluids when compressed cold and dry air was delivered through the nose. This effect was also prevented when warm and moist air was delivered. More recently, Almendros et al provided evidence that CPAP use in rats triggered early nasal inflammation.

Of the variety of methods used to treat nasal symptoms during CPAP treatment, the most common is humidification of the inspired air. However, the mechanism Oby which humidified CPAP attenuates nasal symptoms has never been assessed objectively in OSA patients. Therefore, the purpose of this study is to examine the effect of humidified CPAP on nasal airway physiology with combined measurements of nasal resistance and level of inflammatory markers. Our hypothesis is that the addition of heated humidification in CPAP decreases nasal airway resistance and nasal mucosal inflammation markers and thus, ameliorates nasal symptoms of OSAS patients.

Study design: