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We have concerns about the CAOS study’s interpretation of prognostic estimates by grouping chronic obstructive pulmonary disease (COPD) and asthma together1: this may underestimate the true discrepancy suggested.
Asthma and COPD are essentially different diseases, in terms of aetiology, clinical course of exacerbations, and responses to critical care interventions—for example, ventilatory management. Furthermore, the inhospital death rates for intubated patients are notably different, at 20-30% for COPD2 3 and about 10% for asthma.4
Both diseases have differing prognostic indicators of outcomes, which may have an important influence on intensive care clinicians’ judgments on whether to admit such patients.
We believe that patients with severe asthma are much less likely to be refused admission to intensive care or intubation than patients with severe exacerbations of COPD. Furthermore, perceptions of out of hospital survival for asthma are likely to be better than for COPD. We therefore speculate that the difference between predicted and actuarial survival of the CAOS cohort is likely to have been an underestimate of the prognostic pessimism in a COPD cohort.
Is it not this particular group who we are really concerned may be “missing out” on the services of intensive care units? We would welcome presentation of the data for COPD alone.
Competing interests: None declared.