title: Human pulmonary resistance: effect of frequency and gas physical properties.
abstract: We have investigated a new technique that could be specific for detecting small airway diseases. We measured resistance in nine subjects, evaluating the effect of breathing 80% He-20%O2, air, and 80% SF6-20% O2 at different flow rates (0.25--1.01 l/s) and frequencies (4--12 Hz). To test the sensitivity and specificity of this new technique, we used intravenous histamine infusion to cause peripheral constriction. During histamine infusion six of nine subjects showed the following changes: 1) dynamic compliance decreased; 2) subjects developed frequency dependence of compliance, and 3) there was no significant change in pulmonary resistance or Rrs (respiratory resistance) at 4 Hz. These data suggested a time-constant discrepancy in the periphery due to histamine infusion. These six subjects also developed frequency dependence of resistance (delta Rrs from 4 to 12 Hz), which was significant when breathing air (-22 +/- 6%) and maximal when we used He-O2 (-32 +/- 3%). We conclude that He-O2 can improve the specificity of frequency dependence of Rrs for detecting events occurring in the peripheral airways.
mesh_terms: D000328:Adult; D000403:Airway Resistance; D005459:Fluorides; D005652:Functional Residual Capacity; D006371:Helium; D006632:Histamine; D006801:Humans; D008170:Lung Compliance; D008173:Lung Diseases, Obstructive / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D010100:Oxygen; D013455:Sulfur
chemical_list: D006371:Helium; D013455:Sulfur; D006632:Histamine; D005459:Fluorides; D010100:Oxygen