![]() In the average adult the alveoli are ventilated by 4L of air and perfused by 5L of blood each minute, giving a V/Q ratio of 0.8 (4:5). This is the ratio of alveolar ventilation to alveolar perfusion. V/Q refers to the ventilation-to-perfusion ratio. Hypercapnia (+/- hypoxaemia) normally results from reduced alveolar ventilation or increased alveolar dead space. Whilst V/Q mismatch, shunts and diffusion limitation cause hypoxaemia they may also feature hypercapnia if the disease process is severe enough. ![]() Though below we discuss them separately they are related and often occur together. There are a number of processes that lead to hypoxaemia and hypercapnia. V D-Alv was higher in infants that have undergone prolonged mechanical ventilation.Īnatomical dead space capnography newborn infants physiological dead space premature.Hypoxaemia is most commonly caused by a V/Q mismatch, hypercapnia is often caused by alveolar hypoventilation. V D-Ana /kg and V D-Alv /kg increased with decreasing weight and gestation. The median V D-Alv /kg was not higher in prematurely born infants compared to term infants after adjusting for differences in respiratory rate and days of ventilation (P = 0.482). The median V D-Ana /kg was higher in prematurely born infants compared to term infants. ![]() V D-Ana and V D-Alv were related to body weight at the time of study. ![]() V D-Alv was determined by subtracting V D-Ana from the physiological dead space which was determined by the Bohr-Enghoff equation. V D-Ana was determined using Fowler's method of volumetric capnography. Retrospective analysis of data collected at King's College Hospital NHS Foundation Trust, London, UK.įifty-six infants (11 term, 45 preterm) were studied at a median age of 8 (IQR 2-33) days. V D-Ana and V D-Alv will be higher in prematurely born compared to term born infants. To compare the anatomical (V D-Ana ) and alveolar dead space (V D-Alv ) in term and prematurely born infants and identify the clinical determinants of those indices. ![]()
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