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This Article Full Text Full Text (PDF) All Versions of this Article: 574/3/859    most recent jphysiol.2005.102129v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Verma, M. Articles by Kirkness, J. P. Search for Related Content PubMed PubMed Citation Articles by Verma, M. Articles by Kirkness, J. P. Related Collections Respiratory

¹ Ludwig Engel Centre for Respiratory Research, Westmead Hospital, Westmead, NSW 2145, Australia
² The University of Sydney, Camperdown, NSW 2006, Australia
³ University of Western Sydney, Penrith, NSW 1797, Australia

We have recently demonstrated that the severity of sleep-disordered breathing in obstructive sleep apnoea hypopnoea syndrome (OSAHS) can be reduced by lowering the surface tension () of the upper airway lining liquid (UAL). Morning xerostomia (related to oral breathing during sleep) is reported by most OSAHS patients. In the present study we examine relationships between breathing route, oral mucosal ‘wetness’ and the of UAL. We studied eight healthy subjects (age, 25 ± 5 years [mean ± S.D.]; body-mass index, 23 ± 2 kg m^–2) during a 120 min challenge of both nasal-only breathing (mouth taped) and oral-only breathing (nose clip), each on a separate day (randomized). Both oral mucosal ‘wetness’ (5 s contact gravimetric absorbent paper strip method) and the (‘pull-off’ force technique) of 0.2 µl samples of UAL obtained from the posterior pharyngeal wall were measured at 15 min intervals (mouth tape removed and replaced as required). Upper airway mucosal ‘wetness’ increased during 120 min of nasal breathing from 4.0 ± 0.4 (mean ± S.E.M.) to 5.3 ± 0.3 µl (5 s)^–1 but decreased from 4.5 ± 0.4 to 0.1 ± 0.2 µl (5 s)^–1 with oral breathing (both P < 0.001, repeated-measures ANOVA, Tukey's multiple comparison test, post hoc test). Concurrently, the of UAL decreased from 59.3 ± 2.2 to 51.8 ± 0.98 mN m^–1 with nasal breathing but increased from 64.4 ± 2.7 to 77.4 ± 1.1 mN m^–1 with oral breathing (P < 0.001). For the group and all conditions studied, of UAL values strongly correlated with upper airway mucosal ‘wetness’ (correlation coefficient, r² = –0.34, P < 0.001; linear regression). We conclude that oral breathing increases and nasal breathing decreases the of UAL in healthy subjects during wakefulness. We speculate that nasal breathing in OSAHS patients during sleep may promote a low of UAL that may contribute to reducing the severity of sleep-disordered breathing.

(Received 2 March 2006; accepted after revision 8 May 2006; first published online 11 May 2006)
Corresponding author J. P Kirkness: Ludwig Engel Centre for Respiratory Research, Westmead Hospital, Westmead, NSW 2145, Australia. Email: jason_kirkness{at}wmi.usyd.edu.au

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