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1 Ludwig Engel Centre for Respiratory Research, Westmead Hospital and University of Sydney, Westmead, NSW, Australia
* To whom correspondence should be addressed. E-mail: jason_kirkness{at}wmi.usyd.edu.au.
We have previously shown that lowering surface tension (
) of upper airway lining liquid (UAL) reduces upper airway opening (anesthetized humans) and closing (anesthetized rabbits) pressures. We now hypothesize that in sleeping obstructive sleep apnea hypopnea syndrome (OSAHS) patients lowering of UAL will enhance upper airway stability and decrease the severity of sleep disordered breathing. Methods: Nine OSAHS patients (respiratory disturbance index (RDI): 49±8 events/hr (SEM), diagnostic night) participated in a two part, one night, polysomnography study. In the first part, UA closing pressures (during NREM sleep, PCRIT) were measured and samples of UAL (awake) were obtained before and after instilling 2.5mL of surfactant (Exosurf®, Glaxo Smith Kline) into the posterior pharynx. The of UAL was determined using the "pull-off" force technique. In the second part subjects received a second application of 2.5mL surfactant and then slept the remainder of the night (205±30 min). Results: Instillation of surfactant decreased the of UAL from 60.9±3.1 mN/m (Control) to 45.2±2.5 mN/m (Surfactant) (n=9, p<0.001). PCRIT decreased from 1.19±1.14 cm H2O (Control) to -0.56±1.15 cm H2O (Surfactant) (n=7, p<0.02). Compared with the second half of diagnostic night, surfactant decreased RDI from 51±8 events/hr to 35±8 events/hr (n=9, p<0.03). The fall in RDI (
RDI) correlated with the fall in of UAL () (RDI=1.8x, r=0.68, p=0.04). Hypopneas decreased ~50% from 42±8 events/hr to 20±5 events/hr (n=9, p<0.03, paired t-test). The of UAL measured next morning remained low at 49.5±2.7 mN/m (n=9, p<0.001, ANOVA, compared with Control). Conclusion: Instillation of surfactant reduced the of UAL in OSAHS patients, decreased PCRIT and the occurrence of hypopneas. Therapeutic manipulation of of UAL may be beneficial in reducing the severity of sleep disordered breathing in OSAHS patients.
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