George Obminski

Standardization of inhalation provocation tests: Influence of nebulizer output, particle size, and method of inhalation

Standardization of inhalation tests requires a knowledge of factors that will affect the response. We measured the output and particle size of six types of nebulizers used for inhalation tests. Output varied considerably between nebulizers of different types (0.12 to 1.59 ml/min) and to a lesser extent between nebulizers of the same type. Particle size varied between 0.8 and 5.2 micrometer aerodynamic mass median diameter (AMMD). The influence of these two properties on bronchial response to inhaled methacholine was examined. Nebulizer output but not particle size (between 1.3 and 3.6 micrometer AMMD) altered the response. We also examined the effect of change in inspiratory time during inhalation from residual volume to total lung capacity on lung deposition of radiolabeled aerosol and on the provocative concentration of histamine required to reduce the 1-sec forced expiratory volume (FEV1) by 20% (PC20). A reduction in inspiratory time from 8 to 2 sec resulted in a lower total lung dose, relatively more aerosol deposited in central airways, and a higher PC20. The results emphasize the importance of keeping nebulizer output and pattern of breathing constant when performing inhalation provocation tests if consistent results are to be obtained.

Enhanced pulmonary and active skeletal muscle gas exchange during intense exercise after sprint training in men

1 This study investigated the effects of 7 weeks of sprint training on gas exchange across the lungs and active skeletal muscle during and following maximal cycling exercise in eight healthy males. 2 Pulmonary oxygen uptake (V̇O2) and carbon dioxide output (V̇CO2) were measured before and after training during incremental exercise (n= 8) and during and in recovery from a maximal 30 s sprint exercise bout by breath‐by‐breath analysis (n= 6). To determine gas exchange by the exercising leg muscles, brachial arterial and femoral venous blood O2 and CO2 contents and lactate concentration were measured at rest, during the final 10 s of exercise and during 10 min of recovery. 3 Training increased (P < 0.05) the maximal incremental exercise values of ventilation (V̇E, by 15.7 ± 7.1%), V̇CO2 (by 9.3 ± 2.1%) and V̇O2 (by 15.0 ± 4.2%). Sprint exercise peak power (3.9 ± 1.0% increase) and cumulative 30 s work (11.7 ± 2.8% increase) were increased and fatigue index was reduced (by −9.2 ± 1.5%) after training (P < 0.05). The highest V̇E, V̇CO2 and V̇O2 values attained during sprint exercise were not significantly changed after training, but a significant (P < 0.05) training effect indicated increased V̇E(by 19.2 ± 7.9%), V̇CO2(by 9.3 ± 2.1%) and V̇O2(by 12.7 ± 6.5%), primarily reflecting elevated post‐exercise values after training. 4 Arterial O2 and CO2 contents were lower after training, by respective mean differences of 3.4 and 21.9 ml l−1 (P < 0.05), whereas the arteriovenous O2 and CO2 content differences and the respiratory exchange ratio across the leg were unchanged by training. 5 Arterial whole blood lactate concentration and the net lactate release by exercising muscle were unchanged by training. 6 The greater peak pulmonary V̇O2 and V̇CO2 with sprint exercise, the increased maximal incremental values, unchanged arterial blood lactate concentration and greater sprint performance all point strongly towards enhanced gas exchange across the lungs and in active muscles after sprint training. Enhanced aerobic metabolism after sprint training may contribute to reduced fatigability during maximal exercise, whilst greater pulmonary CO2 output may improve acid‐base control after training.