Lateral decub position and lungs reserve

 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

Answer: A

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.

#pulmonary

References: 

1. Larsson A, Malmkvist G, Werner O. Variations in lung volume and compliance during pulmonary surgery. Br J Anaesth 1987; 59:585. 

 2. Bhuyan U, Peters AM, Gordon I, Davies H, Helms P. Effects of posture on the distribution of pulmonary ventilation and perfusion in children and adults. Thorax. 1989;44(6):480-484. doi:10.1136/thx.44.6.480 

 3. Alcoforado L, Pessôa Filho LC, Brandão DC, Galvão AM, Reinaux CM, Andrade AD. Influence of change in lateral decubitus on pulmonary aerosol deposition. Rev Bras Fisioter. 2011 Aug-Sep;15(4):278-83. English, Portuguese. PMID: 21971723.