The effect of lung deflation on the position and size of the subclavian vein in mechanically ventilated infants and children.

Background: If lung deflation increases the distance from the subclavian vein (SCV) to the pleura and the diameter of the vein, it might decrease the risk of pneumothorax and increase the success rate of subclavian venous cannulation. We evaluated the effect of lung deflation on the distance from the SCV to the pleura (SCV-pleura distance) and on the cross-sectional area (CSA) of the SCV in mechanically ventilated pediatric patients.

Methods: Fifty patients (25 infants younger than 1 year and 25 children aged 1 to 8 years) were placed supine over a shoulder roll, and their lungs were ventilated with a tidal volume of 6 to 7 mL/kg. Lung deflation was achieved by opening the endotracheal tube to the atmosphere. The SCV-pleura distances and the SCV CSAs were measured using ultrasound at the end of inflation and 0, 30, 60, 90, and 120 seconds after lung deflation. A P value <0.05 was considered statistically significant. Increases of 5% in the distance and 25% in the CSA were defined as clinically relevant.

Results: The available data from 43 patients, 22 infants and 21 children, were analyzed. No clinically relevant changes in the SCV-pleura distance or in the SCV CSA were induced by lung deflation. Neither the SCV-pleura distance nor the CSA showed any further increase with time.

Conclusions: Lung deflation failed to increase the SCV-pleura distance and the CSA of the SCV. Its application is unlikely to be advantageous in avoiding pneumothorax or improving the success rate of subclavian venous cannulation.