Measuring the change in a patient's ability to blow three times in quick succession into a peak flow meter during an acute asthma attack predicts the length of time they will stay in hospital. If confirmed, use of this simple measure could improve patient outcome, say the authors of a research pointer in this week's BMJ.
The team recruited 43 successive patients presenting with acute exacerbation of asthma to two hospitals. Each patient was asked to blow deeply, three times, into a peak flow meter, ensuring a gap of less than 10 seconds between blows.
Using these three sequential readings, the team calculated the ratio of the first to last peak expiratory flow (last:first ratio) by dividing the third peak expiratory flow by the first, and related this to length of hospital stay.
Fifteen patients had a last:first ratio of less than 1, and 28 had a ratio of 1 or more. Length of hospital stay for the group with a ratio of less than 1 was three days compared with only one day for the group with a ratio of 1 or more.
This association suggests that the change in flow with repeated blows is likely to reflect a physiological phenomenon such as the effects of deep inspiration on airway caliber, explain the authors. Patients with a low ratio therefore might have recovered more slowly because of greater inflammation of their airways, they conclude.
(Reference: Peak expiratory flow sequence in acute exacerbations of asthma BMJ Volume 322, p 1281.)
[Contact: Dr. Chris Brightling]
25-May-2001
