Influence of body tilt within the sagittal plane on odor identification performance.

Odor identification performance, nasal airflow resistance, blood pressure, and heart rate were assessed in 8 men and 8 women in the following body tilt positions within the sagittal plane: 0 degree (upright), 90 degrees (supine), 135 degrees, and 180 degrees (upside down). The order of testing across the tilt conditions was systematically counterbalanced using a Latin square procedure. Average odor identification performance decreased monotonically as a function of increased body tilt. Significant decreases in heart rate and blood pressure were observed as the body was tilted from the upright condition, although blood pressure was equivalent in the upright and upside down conditions. Nasal resistance was highly variable and was not systematically altered as a function of body tilt. These data support the hypothesis that olfactory function, like visual, auditory, and vestibular function, is significantly influenced by body position within a gravitational field.