UCL Discovery

Abstract

Studies of lung function were carried out on 8 asthmatics during and after an acute attack. Inequality of ventilation as measured by the argon alveolar plateau (Ar(1-2] showed gradual improvement during the period of observation in most of these asthmatic subjects. Residual inequality of ventilation was detected in these subjects during clinical 'remission' when compared to values for Ar(1-2) in normal subjects (P less than 0.01). The degree of inequality of ventilation observed correlated with hypoxaemia (P less than 0.05). All subjects tested with helium-oxygen flow-volume curves were initially 'non-responders', but 7 out of 8 became responders during their clinical recovery. This suggests that the main site of airflow obstruction may be in the peripheral airways in acute severe asthma but that this improves during clinical recovery and then the main site of airflow limitation switches to the larger airways. The mean respiratory exchange ratio difference between one and two litres of expiration R(1-2) was raised in the first 4 days of observation (P less than 0.05) reflecting the presence of ventilation-perfusion imbalance. However no residual imbalance was detected in the mean R(1-2) after day 11