Effects of head-up tilt on intrapulmonary shunt fraction and oxygenation during 1-lung ventilation in the lateral decubitus position

Objective

Hypoxemia is a common problem of 1-lung ventilation. Arterial oxygenation progressively decreases after 1-lung ventilation. The surgical position influences the shunt and arterial oxygenation. Therefore we evaluated the effect of head-up tilt on intrapulmonary shunt and oxygenation during 1-lung ventilation in the lateral decubitus position.

Methods

Twenty patients requiring 1-lung ventilation were included in this study. During 1-lung ventilation, hemodynamic and respiratory variables were measured 15 minutes after horizontal positioning in the lateral decubitus position (baseline), 5 and 10 minutes after a 10-degree head-up tilt (T5 and T10, respectively), and 10 minutes after the patient was returned to a horizontal position (T20). Arterial and mixed venous blood analyses were performed at the same time points.

Results

Arterial oxygenation was increased, and shunt was decreased significantly during head-up tilt position in 1-lung ventilation. These changes were accompanied by decreases in the mean arterial pressure and cardiac filling pressures without significant changes in cardiac index.

Conclusions

Head-up tilt during 1-lung ventilation in the lateral decubitus position caused a significant decrease in shunt and an increase in arterial oxygenation that persisted after the patient was returned to the horizontal lateral decubitus position.

CTSNet classification: 1;9

Abbreviations and Acronyms: A-ao₂, alveolar–arterial O₂ gradient, CI, cardiac index, HPV, hypoxic pulmonary vasoconstriction, MAP, mean arterial pressure, OLV, 1-lung ventilation, PCWP, pulmonary capillary wedge pressure, PVRI, pulmonary vascular resistance index, SVRI, systemic vascular resistance index, V/Q, ventilation–perfusion