Absence of nasal air flow during pursed lips breathing. The soft palate mechanisms.

During pursed-lips (PL) breathing, even though expiratory air-flow resistance is probably higher than during nasal breathing, there is no air flow through the nose. This should imply an active mechanism that prevents air from escaping through the nares. In 6 patients with chronic obstructive lung disease (FEV1/FVC 34.5 +/- 11.8%; mean +/- 1 SD), nasal resistance averaged 2.6 +/- 0.5 cm H2O.L-1.s-1, whereas translabial resistance (during PL expiration) was 5.7 +/- 0.7 cm H2O.L-1.s-1 (p less than 0.005 by paired t test). Nasal air flow during PL expiration was zero. In all patients, cineradiographic studies showed during the expiratory phase of PL breathing that the soft palate rose to closely contact the posterior pharyngeal wall, completely occluding the entrance to the nasopharynx. This upward movement of the soft palate was of active nature. The palate muscles should be considered as accessory respiratory muscles.