If both patients have anatomical dead space of 200 m l, who has better alveolar ventilation?10/6/2023 ![]() ![]() Prematurely born infants with pulmonary disease have a higher dead space than term controls, which may influence the optimum level during volume-targeted ventilation. ![]() V A in infants with RDS or BPD was similar to that of the controls. Minute ventilation was higher in both infants with RDS or BPD compared to the controls. The dead space was higher in 35 infants with respiratory distress syndrome (RDS) and in 26 infants with bronchopulmonary dysplasia (BPD) than in 20 term controls with no respiratory disease. ResultsĮighty-one infants with a median (range) gestational age of 28.7 (22.4–41.9) weeks were recruited. Alveolar ventilation ( V A) was also calculated. Volumetric capnograms were constructed to calculate the dead space using the modified Bohr–Enghoff equation. Expiratory tidal volume and carbon dioxide levels were measured. MethodsĪ prospective study of mechanically ventilated infants was undertaken. We determined if there were differences in dead space and alveolar ventilation in ventilated infants with pulmonary disease or no respiratory morbidity. Depending on the disease condition, additional mechanisms that can contribute to an elevated physiological dead space measurement include shunt, a substantial increase in overall V'A/Q' ratio, diffusion impairment, and ventilation delivered to unperfused alveolar spaces.Dead space is the volume not taking part in gas exchange and, if increased, could affect alveolar ventilation if there is too low a delivered volume. For the range of physiological abnormalities associated with an increased physiological dead space measurement, increased alveolar ventilation/perfusion ratio (V'A/Q') heterogeneity has been the most important pathophysiological mechanism. Although a frequently cited explanation for an elevated dead space measurement has been the development of alveolar regions receiving no perfusion, evidence for this mechanism is lacking in both of these disease settings. An elevated physiological dead space, calculated from measurements of arterial CO2 and mixed expired CO2, has proven to be a useful clinical marker of prognosis both for patients with acute respiratory distress syndrome and for patients with severe heart failure. ![]()
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