Glottal aperture during panting with voluntary limitation of tidal volume.

A disadvantage of the forced oscillatory technique for measuring total respiratory resistance (namely, that it is usually done during quiet breathing or breathing holding--breathing patterns where the glottic aperture may be highly variable) was overcome by making the measurement during panting. The imposed forced oscillations (Hz) were distinguished from the spontaneous quiet breathing and panting frequencies by ensemble averaging. However, when panting was voluntary restricted so as to standardize the quiet breathing and panting flow amplitudes, resistance values frequently increased. The suggestion that partial glottal closure occurred during voluntarily restricted panting was confirmed by simultaneous inspection of the glottis with a fiberoptic bronchoscope. Thus, maximal opening of the glottis is assured only during unrestricted panting.