Am. J. Respir. Crit. Care Med., Volume 159, Number 5, May 1999, 1551-1555

Dysfunctional Mechanical Coupling of Upper Airway Tissues in Sleep Apnea Syndrome

FRÉDÉRIC SÉRIÈS, CLAUDE CÔTÉ, and SYLVAIN ST. PIERRE

Unité de Recherche, Centre de Pneumologie de l'Hôpital Laval; and Laboratoire de Neurosciences and Ear, Nose, and Throat Department, Centre Hospitalier de l'Université Laval, Université Laval, Ste. Foy, Québec, Canada

The mechanical effect of musculus uvulae (MU) contraction on in vitro uvular shortening and/or displacement was measured in 15 patients with a sleep apnea hypopnea syndrome (SAHS) and in 8 snorers. Using freshly resected uvular tissues, passive and active uvular tissue-specific elastance and shortening were determined during stimulation of MU. No difference was found in maximum tetanic tension measured on uvular tissue between the two groups (47.2 ± 14.8 g in SAHS and 39.1 ± 16.5 g in snorers). Passive uvular-specific elastance was significantly less in snorers (0.36 ± 0.27 g/% Lo) compared with patients with SAHS (0.84 ± 0.39 g/% Lo) (p = 0.006). There was a negative correlation between uvular shortening and passive uvular specific elastance (r = 0.69, p = 0.05). Maximal tetanic tension developed by isolated MU was higher in SAHS than in snorers (45.8 ± 23.1 and 30.0 ± 8.3 g, respectively, p = 0.04). A strong positive relationship was found between the apnea index and specific uvular elastance (r = 0.55, p = 0.007). We conclude that there is a significant difference between the uvular tissue elastance of SAHS and snorers, and that this difference influences the mechanical efficiency of MU contraction.

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