Dyspnoea at rest and at the end of different exercises in patients with near-fatal asthma.

Blunted perception of dyspnoea under resistive loading has been observed in patients with a history of near-fatal asthma (NFA). The perception of dyspnoea at rest and at the end point of various exercises was assessed in such patients. Respiratory function and exercise capacity (6-min walking distance, incremental cycloergometry and inspiratory threshold loading) were assessed in seven NFA and eight non-NFA patients. Dyspnoea (Borg scale) was measured at rest and at the end point of the various exercises. Dyspnoea at rest was significantly lower in NFA patients. Although exercise tolerance was similarly reduced in both the NFA and non-NFA groups, dyspnoea at peak cycle exercise was significantly lower in the former (2.6+/-2 versus 6.1+/-3.8 (Borg scale; mean+/-SD)), who mainly (86%) stopped because of leg discomfort. A similar trend was observed in the 6-min walking distance and inspiratory threshold loading tests. Dyspnoea at peak exercise was the best indicator of the NFA condition, with a sensitivity of 100% and specificity of 63% for a Borg scale score of < or = 6. Perception of dyspnoea is blunted in near-fatal asthma patients at both rest and the end point of various forms of exercise. Dyspnoea at peak exercise is the best indicator of the near-fatal asthma condition.