Fig. 2
From: Pitfalls of assessment of autonomic function by heart rate variability
Schema of the effects of physiological RSA and its inversion (inverse RSA) on the relationship between alveolar gas volume and capillary blood flow during inspiration and expiration. Horizontal red bows and vertical green arrows indicate the volume of blood flow and the direction of gas flow, respectively. Physiological RSA improves respiratory gas exchange efficiency through matching between alveolar ventilation and capillary perfusion throughout the respiratory cycle, while the inversion of the relationship (inverse RSA) results in increased alveolar dead space (wasted ventilation) and increased intrapulmonary shunt. (Revised figure in reference [61])