Bronchoconstrictor effects of a deep inspiration in patients with asthma.
A deep inspiration from functional residual capacity to total lung capacity, performed at a low flow rate by a group of 40 unselected adult patients with asthma, yielded an immediate and transient increase (71 per cent, P smaller than 0.001) in specific airway resistance. In 2 of the 40, deep inspiration provoked an attack of asthma. The effect of deep inspiration can be attributed to a vagal bronchoconstrictor reflex, because it was prevented or decreased in most of the cases by inhalation of an anticholinergic drug. Beta-adrenergic blockade by propranolol potentiated in a minority of subjects the bronchoconstrictor response to deep inspiration. Deep expiration also induced a bronchoconstrictor effect, which was weaker than that of deep inspiration. It follows that functional studies of asthmatics may be biased if the technique requires maximal respiratory maneuvers.
D000293:Adolescent; D000328:Adult; D000403:Airway Resistance; D001249:Asthma / Q000188:drug therapy / Q000503:physiopathology*; D001980:Bronchi / Q000187:drug effects; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D009241:Ipratropium / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010993:Plethysmography, Whole Body; D011433:Propranolol / Q000494:pharmacology; D012115:Residual Volume; D012119:Respiration
D011433:Propranolol; D009241:Ipratropium