Tolerance Curves of Carbon Dioxide during Rebreathing in Normal Subjects, Pulmonary Emphysema and Obesity

¹ Clinic of Physical Therapy, Medical School, Komensky University, and the Research Institute of Physical Medicine, Balneology and Climatology

The tolerance curves for CO₂ were investigated in 11 normal subjects, eight patients with pulmonary emphysema and seven with obesity using the rebreathing method for CO₂. The tolerance curves were shifted to the right in emphysema and obesity in contrast to normal subjects for the beginning of hyperventilation by higher partial pressures of alveolar O₂. The correlation of these values with PaCO₂ was significant only in obesity. The character of the curves and the degree of hvperventilation were not significantly different from that in normal subjects. This confirms the postulate that the decreased response of the respiratory center to CO₂ is the primary factor in the decreased respiratory response to CO₂ in emphysema and obesity. The values of partial pressures of O₂ and CO₂ at the termination of the investigation confirmed the elimination of hypoxic stimulus.