Clinical value of rebreathing test in obstructive lung diseases

The ventilatory response to CO2 inhalation, using rebreathing method, was studied in normal subjects and in patients with bronchial asthma and chronic obstructive lung disease. The patients with lung disease had flatter CO2 response curves. However, it the ventilation was expressed as a fraction of the maximal voluntary ventilation, the difference between normal subjects and patients disappeared. The reduced ventilatory response of these patients may be of mechanical origin and not depending on reduced CO2 sensitivity. The high lung volume of these patients may be the mean factor of the mechanical disadvantage of thoracomuscular system.