ABSTRACT
<p><b>OBJECTIVE</b>To study the effect of different jaw forward distance on forced inspiratory airflow(FIF) in non-apnea subjects and patients with obstructive sleep apnea hypopnea syndrome (OSAHS) and to evaluate the effective jaw forward distance for the treatment of OSAHS with the oral appliance.</p><p><b>METHODS</b>FIF was measured in 18 non-apnea subjects and 18 OSAHS patients at supine and lateral body positions with different jaw forward distances (the percentages of maximum jaw forward distance): 0%, 25%, 50% and 75%. FIF were converted to percentage values (FIF%, x(-) ± s) followed by averaged. Then the results were analyzed by one-way analysis of variance and paired t-test with α = 0.05.</p><p><b>RESULTS</b>For non-apnea subjects, there was no significant difference in the FIF values between different jaw forward distances as well as different body positions. For OSAHS patients, the mean FIF% at supine and lateral body positions were 107.1% ± 29.0% and 112.0% ± 33.1% at jaw forward 50%, and were 106.4% ± 20.7% and 116.8% ± 36.4% at jaw forward 75%, respectively, which were significantly higher than those (84.0% ± 18.3% and 98.3% ± 24.0%) at jaw forward 0% or those (92.7% ± 21.8% and 103.7% ± 22.6%) at jaw forward 25%, respectively. But there was no statistical difference in FIF between the two groups of jaw forward 50% and jaw forward 75% and no statistical difference in FIF between supine and lateral body positions in the same forward position.</p><p><b>CONCLUSION</b>Jaw forward 50% is a effective jaw forward distance by oral appliance for the treatment of OSAHS and can improve the airway ventilation in OSAHS patients.</p>