Influence of lung inflation on the cross-sectional area of central airways in normals and in patients with lung disease.

The influence of lung inflation on the cross-sectional area of the trachea and main bronchi was investigated in 2 normal subjects, 2 patients with emphysema, and 1 patient with pulmonary fibrosis. Fiberoptic cinebronchoscopy was used to measure the cross-sectional area of the airways using calibrated small Teflon discs placed on the airway wall as reference. As an estimate of airway compliance at intermediate lung volumes, radial distensibility was defined as the change in cross-sectional area per change in airway pressure minus esophageal pressure divided by the cross-sectional area at functional residual capacity.

Continuous measurement of respiratory resistance in asthmatic children.

In 13 children (7-13 years old) with bronchial asthma in remission, respiratory system resistance was continuously measured by the forced oscillation method at 10 Hz, using on-line digital computer analysis. Corrections were made for mouth impedance which was determined from a prior Valsalva maneuver. Functional residual capacity was also periodically determined by the body plethysmographic technique in order to allow calculation of specific respiratory system conductance (SGRS).

Tracheal mucous transport in experimental canine asthma.

Tracheal mucous velocity (TMV) was measured in experimental canine asthma. All 10 sensitive dogs exposed to an aerosol of Ascaris suum extract showed a decrease in TMV to about one-third of base-line values within 45 min whereas only half of them (reactors) responded with bronchospasm as measured by a significant reduction in specific respiratory system conductance (SGrs). Mean TMV remained decreased at the end of the 2-h observation period when mean SGrs had returned to base-line values in the reactors.

Effects of lung inflation on pulmonary arterial blood volume in intact dogs.

The isolated effects of alterations of lung inflation and transmural pulmonary arterial pressure (pressure difference between intravascular and pleural pressure) on pulmonary arterial blood volume (Vpa) were investigated in anesthetized intact dogs. Using transvenous phrenic nerve stimulation, changes in transmural pulmonary arterial pressure (Ptm) at a fixed transpulmonary pressure (Ptp) were produced by the Mueller maneuver, and increases in Ptp at relatively constant Ptm by a quasi-Valsalva maneuver. Also, both Ptm and Ptp were allowed to change during open airway lung inflation.

Relationship between frequency dependence of lung compliance and distribution of ventilation.

The previously demonstrated empirical association between frequency dependence of lung compliance and distribution of ventilation, the latter determined by the N(2) washout technique, was confirmed by establishing a mathematical link between the two tests. By assuming a two-compartment system with known compliances and making corrections for Pendelluft and common dead space mixing effects, the ratio of dynamic to static compliance (C(dyn)/C(st)) for any respiratory frequency can be calculated from the compartmental analysis of the N(2) washout at a single respiratory frequency. By using these equations, a good correlation was found between calculated and measured C(dyn)/C(st) in dogs with artificially induced bronchial obstruction and in young smokers or young nonsmokers after carbachol inhalation.