Patterns of Ventilatory Response to Carbon Dioxide during Recovery from Severe Asthma

Abstract

1. Ventilatory response to CO₂ was measured regularly by a rebreathing technique in nineteen patients with severe asthma from the day of presentation to the time of clinical recovery. 2. Ventilatory response to CO₂ increased during recovery in sixteen patients and the increased ventilatory response correlated well with increase of FEV₁. Among these sixteen patients only one showed elevation of arterial CO₂ tension at the time of presentation. 3. Ventilatory response to CO₂ failed to increase during recovery in three patients despite increases in FEV₁. All three patients showed elevation of arterial CO₂ tension at the time of presentation. 4. In five patients (including three of the four with initial hypercapnia) ventilatory response to CO₂ after recovery remained below the previously reported lower limit for normal subjects. The limits of normality were explored by examining ventilatory response to CO₂ in seventeen outstanding athletic performers. Values for ventilatory response to CO₂ both above and below the previously defined ‘normal range’ were found. The normal ventilatory response to CO₂ covers a 14-fold range from 0.57 to 8.17 1 min⁻¹ mmHg⁻¹ Pco₂.