Effect of Jaw Position and Posture on Forced Inspiratory Airflow in Normal Subjects and Patients With Obstructive Sleep Apnea

¹ From the UCLA Diagnostic Sciences and Orofacial Pain Department, Los Angeles
² From the UCLA Sleep Disorder Center, Los Angeles

Objective: This study evaluated whether substantial airflow changes occur by changing both body posture and jaw position in normal subjects and patients with obstructive sleep apnea (OSA).

Design: A case-control design was utilized to assess group differences (OSA vs control) and each subject served as his/her own control subject to assess condition differences (jaw position and body posture changes). Subjects included 16 male patients with OSA (aged 33 to 71 years) whose conditions were diagnosed at the UCLA Sleep Disorders Laboratory with a polysomnographic recording, and 9 male non-OSA subjects (aged 22 to 52 years). The experimental intervention in the study involved alterations in body posture and jaw positioning. Airflow changes were determined using a spirometer that assessed the velocity of airflow during a forced inspiration. Subjects in this study all had the middle portion (25 to 75%) of their maximum forced inspiratory flow (FIF_25.75) curve measured in three positions: (1) normal jaw position-upright body posture (N-U); (2) normal jaw position-supine body posture (N-S); and (3) protrusive jaw position-supine body posture (P-S).

Setting: The study was conducted at the UCLA Dental Clinical Research Center.

Results: Both groups had a significant decrease in their FIF_25.75 upon reclining, and there were no significant group differences regarding the magnitude of this change. Both groups also had a nearly full recovery of their FIF_25.75 airflow when their jaws were positioned forward while reclining.

Conclusions: These data document that when a patient is in a supine position, a 100% protrusive jaw position allows significantly more inspiratory airflow to occur.

Key Words: forced inspiratory airflow • jaw position • obstructive sleep apnea (OSA) • posture • spirometry

Submitted on December 27, 1993
Accepted on February 26, 1996

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