Effects of chest compression on reflex ventilatory drive and pulmonary function

¹ Cardiovascular Research Institute, University of California School of Medicine, San Francisco, California

External compression of the chest sufficient to reduce the lung volume (FRC) by 1 liter in eight normal subjects interfered with the mechanical function of the lungs. We have confirmed the findings of Caro et al. (J. Clin. Invest. 39: 573, 1960), who showed a decrease in lung compliance and an increase in respiratory rate. Neither returned to normal when the compressing force was removed, and it was not until the subject took a deep breath that the lungs returned to their control state. We also found a reduction in anatomical dead space and alveolar hyperventilation. Arterial blood gas tensions showed evidence of complex ventilation-perfusion abnormalities, which could not be explained by any single factor. We think the hyperventilation associated with chest compression is reflex in origin and related to a decrease in lung volume rather than to any change in transpulmonary pressure.