Ventilatory Response to CO2. I. A Psychobiologic Marker of the Respiratory System*

Abstract

When a gas mixture containing CO2 is breathed by a healthy subject, alveolar ventilation is increased. The ratio .DELTA. ventilation/.DELTA. PCO2 [CO2 partial pressure] has been termed the ventilatory response to CO2 (S). Since the development of a rebreathing method in 1967, it is easy to measure this index of the regulation of ventilation. This index, although showing considerable interindividual variation (range, 0.5-9 l/min per mm PCO2 [CO2 partial pressure]), tends to be consistent over time for any given individual. Positive correlations between S and personality traits such as anxiety, extroversion, and aggression and negative correlations between S and certain scales of the Minnesota Multiphasic Personality Inventory (MMPI: depression, psychopathology, psychasthenia and social introversion) were found in previous studies. It was hypothesized that S may be a psychogiologic marker of the respiratory system. A project in which 82 normal subjects (40 male, 32 female) were stuied with both psychologic (Eysenck Personality Inventory, Catell 16PF [Personality Factor], and 168-item MMPI) and rebreathing tests was undertaken to investigate this possibility further. A strong corelation between S and neurotic personality traits wa sfound, but this correlation appeared valid only in female subjects.