Q: What is the effect of lateral decubitus position on pulmonary ventilation perfusion? (select one)
A) perfusion increases in the dependent lung
B) perfusion increases in the non-dependent lung
In refractory hypoxemia changing of a patient's position is a frequent trick tried by clinicians at the bedside. It includes prone as well as lateral decubitus position. This may help or may make situation worse. Knowing one basic principle in conjunction with the extent of pathology in each lung may make it easier to decide on which side of lateral decubitus to choose (right vs left).
In lateral decubitus position
- Dependent lung: perfusion increases, ventilation decreases
- Non-dependent lung: perfusion decreases ventilation increases
This ventilation perfusion mismatch occurs due to changed functional residual capacity and compliance.
References:1. Larsson A, Malmkvist G, Werner O. Variations in lung volume and compliance during pulmonary surgery. Br J Anaesth 1987; 59:585.