Interrelation between lung volume, arterial CO₂ tension, and respiratory activity

¹ Roswell Park Memorial Institute, Buffalo, New York

In anesthetized cats with open thorax the activity of the respiratory muscles (diaphragm and abdominal muscles) is studied as a function of lung volume and arterial CO₂ tension. It is shown that the sensitivity of the inspiratory muscles to a given change in lung volume (V) (Hering-Breuer reflex) varies with the arterial pCO₂ level, and conversely, that the CO₂ sensitivity of the inspiratory motor system is dependent upon the volume of the lungs. The relations are fairly linear and can be expressed by the equation: M – M₀ = K (p_a CO₂ – p₀) (V₀ – V), in which M represents inspiratory motor activity and M₀, p₀, and V₀ and K are constants. The activity of the expiratory muscles is not dependent on CO₂.

Submitted on September 24, 1964

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