Related Experiment Videos
Role of cooling and drying in hyperventilation induced asthma
R D Farley1, M K Albazzaz, K R Patel
1Department of Respiratory Medicine, Western Infirmary, Glasgow.
Thorax
|April 1, 1988
Summary
Airway cooling, not drying, predominantly triggers exercise-induced asthma during hyperventilation. This study found cold air significantly worsened FEV1 compared to dry air challenges in asthmatic and normal subjects.
Area of Science:
- Respiratory Physiology
- Pulmonary Medicine
- Exercise-Induced Asthma
Background:
- Exercise-induced asthma is linked to respiratory heat loss.
- The specific trigger—airway cooling or drying—remains debated.
Purpose of the Study:
- To differentiate the effects of airway cooling versus drying on FEV1 in asthmatic and normal subjects.
- To identify the primary stimulus for hyperventilation-induced asthma.
Main Methods:
- Subjects underwent isocapnic cold air hyperventilation (CAH) and dry ambient air hyperventilation (AAH).
- Changes in FEV1 were measured at varying ventilation rates.
- Respiratory heat exchange rates (sensible and latent heat loss) were calculated.
Main Results:
- Cold air hyperventilation (CAH) caused a greater fall in FEV1 than ambient air hyperventilation (AAH) across all ventilation levels.
- Latent heat loss (drying) was identical in both challenges.
- Sensible heat loss (cooling) was substantially higher during CAH compared to AAH.
Conclusions:
- The rate of convective cooling in the upper airway is the predominant stimulus for hyperventilation-induced asthma.
- Findings suggest that airway cooling plays a more critical role than airway drying in triggering asthma symptoms during hyperventilation.