Regional Ventilation in Infancy

Abstract

There is evidence that in infants with unilateral lung disease, oxygenation improves when the good lung is uppermost--the reverse of the situation in adults. We performed krypton-81m ventilation scanning in 18 infants and very young children (11 days to 27 months old) with and without abnormal chest radiographs. Scanning was performed with the subject supine, in the left decubitus posture (right lung uppermost), and in the right decubitus posture (right lung dependent). Fractional ventilation to the right lung fell when that lung was dependent and rose when it was uppermost (P less than 0.001). This pattern was seen regardless of the appearance of the chest radiograph. The distribution of ventilation away from dependent lung regions represents a reversal of the adult pattern, which may be due to differences between infants and adults in lung mechanics and diaphragmatic function. This study adds further weight to the argument that infants and very young children with unilateral lung disease should be positioned with their normal lung uppermost to optimize gas exchange. It also offers a rational explanation for the observation that infants with unilateral gas trapping can be successfully treated by placing them so that the diseased lung is dependent.

The effect of patient position during trauma surgery on fat embolism syndrome: An experimental study

“…This contradicts the notion of autoregulation of pulmonary blood flow, which redirects blood away from injured areas of the lung to uninjured parts in order to match ventilation and perfusion, especially when the normal lung is dependent (down) for patients with unilateral pulmonary disease. Although this is a known phenomenon2526 present data indicates the opposite, being in agreement with findings indicating that infants have improved ventilation when the affected lung is dependent (down) 31. This observation may be explained by preferential ventilation of the nondependent lung (up), which would lead to subsequent redirection of blood flow to match ventilation and perfusion.…”

“…Baseline measurements of physiologic parameters, blood gases, blood counts and CD62P and CD11/18 levels were obtained. Blue microspheres were injected31 and a right atrial blood sample was obtained to determine the flow rate of the spheres in the pulmonary artery.…”

“…At the 2 h mark, pink microspheres were injected into the pulmonary artery and a blood sample was obtained from the right atrium to determine the rate of flow of the microspheres in the pulmonary vessels. The microsphere method has been used previously 31. Fat embolism in the dog was then induced.…”

“…At the 2 h mark, blood samples were obtained for cell counts, CD62P and CD11/18. Finally, red microspheres were injected into the pulmonary artery31 and a blood sample was obtained from the right atrium to determine the rate of flow of the microspheres in the pulmonary vessels.…”

Respiratory mechanics in ventilated preterm infants: early determinants and outcome

“…Since the peripheral airways are the most substantial part of total respiratory system resistance, peripheral airway closure can have severe consequences, in which mainly basal ventilation is reduced while perfusion is increased, resulting in a significant ventilationperfusion mismatch. 40 The ability of young infants to cope with added respiratory load is also reduced by the configuration of the respiratory pump. Ribs are placed horizontally, reducing the potential for thorax expansion 191 and relying more on diaphragmatic activity to increase thoracic volume.…”