RESUMO
Fourteen healthy males (mean age 54.7 yr) described maximal flow volume curves after Air breathing (AB) and after inspiring 10 deep breaths of a mixture of 80% Helium/20% Oxygen (He/O2). Vmax 50% FVC as obtained from the AB curves was 3.11 +/- 1.27 lps, and this increased by 38.1 +/- 17%, with He/O2. The Vmax 50% He-O2/Air ratio was 1.32 +/- 0.17, while the V iso V was 1.1 +/- 0.35 liters (30.9% of the FVC). Inhalation of 80 micrograms (4 puffs) of Ipratropium bromide, a vagolytic aerosol, or salbutamol (200 micrograms; 2 puffs), a beta 2 adrenergic stimulant did not alter the He/O2 curves significantly. As another aspect of the study, airflow variables viz. Vmax 50% of the FVC, Vmax 25%-75%, and Vmax 25% were measured from the AB curves, and the effect of bronchodilator aerosols was investigated in order to evaluate the degree of control of the bronchomotor tone by either the adrenergic receptors, or the vagus. Only the Vmax 25%-75% increased significantly with Salbutamol administration. While the degree of increase brought about by salbutomol aerosol for all of the variables under investigation was more than that seen with ipratropium br., the difference in this increase between the two bronchodilators used was not significant. The result may indicate that almost an equivocal influence is exerted by the two arms of the autonomic nervous system on bronchomotor tone in middle aged normal males, and that a more sensitive test (viz He-O2 breathing) does not elucidate this any further.