Effect of high versus low ambient humidity on the severity of obstructive sleep apnoea
- aDivision of Respiratory Medicine, bDepartment of Psychiatry, cUniversity of Saskatchewan, Saskatoon, Saskatchewan, Canada
- Dr M F Fitzpatrick, Division of Respiratory and Critical Care Medicine, Richardson House, Queen’s University, Kingston, Ontario, Canada K7L 3N6.
- Received 16 October 1998
- Revision requested 19 January 1999
- Revised 15 March 1999
- Accepted 11 May 1999
Abstract
BACKGROUND Surface tension forces appear to make a significant contribution to upper airway closure in patients with obstructive sleep apnoea (OSA). It is possible that drying of the upper airway mucosa at night might contribute to these surface tension forces and the severity of OSA might therefore change with alteration of the ambient humidity.
METHODS A randomised single blind crossover study of high ambient relative humidity (HRH) versus low ambient relative humidity (LRH) was performed in 12 men of mean (SD) age 49 (9) years with mild OSA (apnoea/hypopnoea index (AHI) 14 (5.2)). On one night patients slept in continuous HRH (85 (4)%, range 80–93%) and on the other in LRH (16 (4)%, range 11–22%).
RESULTS The AHI was similar on the HRH and LRH nights (mean difference 3; 95% CI –2 to 9, p = 0.20) and no statistically significant differences in AHI were observed on the two nights after standardising for body position and sleep stage. Sleep stage distribution and the proportion of time spent in the supine position were similar on the HRH and LRH nights. The number of non-respiratory arousals was also similar on the two nights.
CONCLUSION Altering ambient humidity alone has no significant impact on the severity of OSA.
