Reproducibility of pulmonary function tests under laboratory and field conditions.

The reproducibility of pulmonary function tests in the laboratory and in a mobile field survey vehicle has been studied. Groups of laboratory workers were studied at base and a random sample of 38 coalminers was examined in the mobile laboratory. The intra-subject variability of some newer tests of lung function, including closing volume and maximum flow at low lung volumes, has been compared with that of well-established tests, such as lung volumes and forced expiratory volume from two measurements made more than one day apart. Most measurements were slightly less reproducible in the study of coalminers than in the laboratory personnel. Conventional tests, such as forced expiratory volume in one second, lung volumes, single breath CO transfer factor, and exercise ventilation were very reproducible, the coefficients of variation (cov) being generally between 5% and 10%. The closing volume test, maximum expiratory flow at low lung volumes, and the single breath N2 index were less reproducible: cov between 15% and 39% in the miners. The forced expired time and volume of isoflow, measured only on laboratory workers, however, exhibited greater reproducibility than previously reported (cov = 10% and 15% respectively). It is suggested that, when assessing the repeatability of lung function tests, account should be taken of the circumstances in which the intra-subject variability was measured.

Inertial deposition of particles in human branching airways.

This paper concerns the inertial deposition of aerosol particles in models of human branching airways. Homogeneous monodisperse aerosols of known characteristics were generated using a spinning disc atomizer. These were paused through simple bend systems of differing geometries, and the fractional deposition measured by a fluorimetric technique. The parameter characterizing 50 per cent deposition in the bend was found to agree with that predicted theoretically. Deposition in five models of bifurcating airways having geometries generally compatible with existing anatomical data was studied using essentially the same experimental procedure. The magnitude of the inertial deposit was measured and the overall effect of fluid-flow rate, particle size, branching angle and size of model determined. The results were compared with exsting theoretical estimates of impaction in a bifurcating airway.