Ventilation-Perfusion Relationship in Young Healthy Awake and Anesthetized-Paralyzed Man

Effect of positive end-expiratory pressure on pulmonary shunt and dynamic compliance during abdominal surgery

“…27 It has been shown previously that pulmonary shunt increases during anaesthesia and muscle paralysis. [28][29][30] A mean shunt of ∼8% (range 0-23%) 29 has been demonstrated in young patients, with more severe impairment of lung function seen in older patients resulting in higher values [∼15% (range 0-30%)]. 1 In addition, there are some data suggesting lower values of shunt with intravenous anaesthesia, possibly because of more moderate reductions in FRC 31 or a more preserved hypoxic pulmonary vasoconstriction.…”

A prospective crossover comparison of neurally adjusted ventilatory assist and pressure-support ventilation in a pediatric and neonatal intensive care unit population*

“…Patienttriggered modes have a number of distinct advantages over control modes. As breathing effort is preserved, the physiologic benefits of active diaphragmatic contraction are maintained, with improved ventilation/perfusion ratio matching (1)(2)(3)(4)(5)(6)(7)(8), hemodynamics (5, 7, 9Ϫ12), and a reduction in required inspiratory pressure (13)(14)(15). Additionally, atrophy of the diaphragm arising secondary to mechanical offloading is reduced (16).…”

Physiology of the Airway

“…121 In various studies of healthy young to middle-aged patients under general anesthesia, venous admixture (shunt) has been found to average 10%, and the scatter in V /Q A ratios is small to moderate. 119,122 In patients with a more marked deterioration in preoperative pulmonary function, general anesthesia causes considerable widening of the V /Q A distribution and large increases in both low-V /Q A (0.005 < V /Q A < 0.1) (underventilated) regions and shunting. 118,121,123 The magnitude of shunting correlates closely with the degree of atelectasis.…”