Histamine-induced asthma in children: effects on the ventilation-perfusion relationship.
Asthma was provoked by histamine inhalation in five children in order to study the hypoxaemia that might ensue and the underlying ventilation-perfusion (VA/Q) mismatching. The distribution of the VA/Q ratios was measured by a multiple inert gas technique before the provocation, during the asthmatic attack and after salbutamol inhalation. All children displayed a unimodal distribution of ventilation and perfusion under baseline conditions. During asthma they all developed a bimodal distribution, one mode lying within normal VA/Q regions but with increased perfusion to regions with VA/Q ratios of 0.1-1, which correlated with the observed hypoxaemia; the other mode was centered on a VA/Q ratio of approximately 10 and the magnitude of this mode correlated with FEV1 in percent of the predicted value. Salbutamol improved the VA/Q distribution and restored the blood gases to normal. We hypothesize that histamine-induced asthma causes a state of hyperinflation which compromises regional ventilation and blood flow, resulting in a VA/Q mismatching with one normal and one high VA/Q mode, and hypoxaemia.
D000293:Adolescent; D000420:Albuterol / Q000627:therapeutic use; D001158:Arteries; D001249:Asthma / Q000139:chemically induced* / Q000188:drug therapy / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output / Q000187:drug effects; D002648:Child; D005260:Female; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D008297:Male; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D012123:Pulmonary Ventilation / Q000187:drug effects; D014692:Ventilation-Perfusion Ratio / Q000187:drug effects
D002245:Carbon Dioxide; D006632:Histamine; D000420:Albuterol; D010100:Oxygen