Oronasal Distribution of Ventilation During Exercise in Normal Subjects and Patients with Asthma and Rhinitis

Nasal contribution to breathing with exercise: effect of race and gender

“…As in previous studies (3,7,14,21,22,25,31), our laboratory has shown that the nasal contribution to breathing decreases with increasing exercise (Fig. 1).…”

“…Schultz and Horvath (27) showed that, within an individual, nasal work of breathing was the most repeatable variable at crossover to oral breathing in subjects and thus a potential candidate for determining the initiation of oral augmentation during exercise. Many previous studies, however, have not found good correlations between R nose and the switch to oronasal breathing (7,14,25) between individuals, perhaps because the maximal inspiratory flow through the nose (MIF nose ) may be determined by more than R nose as measured under resting flow conditions (5,6,24). Bridger and Proctor (5,6) suggested that collapsibility of the nasal valve (referred to as alar collapse) plays a role in MIF nose that is independent of R nose downstream of the collapse point (i.e., flow-limiting segment).…”

“…The subject was fitted with a nasal mask (Respironics, Murrysville, PA) (approximate dead space of 60 ml) that was similar to that used in pulmonary sleep laboratories and modified to allow insertion of a mass flowmeter (Korr Medical Technologies, Salt Lake City, UT) to detect nasal airflow (21,22). Total ventilation (V E) was determined by respiratory inductance plethysmography (Respitrace) (calibrated by spirometry) (4,7,30). The Respitrace bands (abdomen and rib cage) were fixed to the subject's torso with adhesive tape to minimize slippage during exercise.…”

“…The level of ventilation at which this switch from nasal to oronasal breathing occurs has been previously referred to as the "oronasal switching point" (21). A number of studies, however, have shown that oronasal breathing occurs at resting ventilation in some individuals (3,7,14). Characterizing the ventilation level and variability across individuals for the relative contribution of nasal to total breathing is critical to the construction of ventilation activity patterns for accurately constructing the airflow apportionment (nasal or mouth) at various ventilation rates associated with different activities.…”

“…The level of exercise at which the oronasal switching point occurs and the relative contributions of oral vs. nasal breathing at rest and during exercise have been studied by a number of investigators (3,7,14,21,22,25,27,31). The physiological determinants of the relative contributions to nasal and oral breathing during exercise are still not well understood.…”