Whole lung lavage decreases physiological dead space in patients with pulmonary alveolar proteinosis: two case reports 

BACKGROUND: Pulmonary alveolar proteinosis (PAP) is a rare disease characterized by progressive accumulation of the alveolar surfactant. Whole lung lavage (WLL) using a high volume of warmed saline remains the standard therapy. However, no established bedside monitoring tool can evaluate the physiological effect of WLL in the perioperative period. Indirect calorimetry, which is generally used to measure resting energy expenditure, can detect carbon dioxide (CO(2)) production and mixed-expired partial pressure of CO(2) breath by breath. In this physiological study, we calculated CO(2) elimination per breath (VTCO(2),br) and Enghoff’s dead space using indirect calorimetry and measured the extravascular lung water index to reveal the effect of WLL. CASE PRESENTATION: We measured VTCO(2),br, Enghoff’s dead space, and the extravascular lung water and cardiac indices before and after WLL to assess the reduction in shunt by washing out the surfactant. A total of four WLLs were performed in two PAP patients. The first case involved an Asian 62-year-old man who presented with a 3-month history of dyspnea on exertion. The second case involved an Asian 48-year-old woman with no symptoms. VTCO(2),br increased, and the Enghoff’s dead space decreased at 12 h following WLL. An increase in the extravascular lung water was detected immediately following WLL, leading to a transient increase in Enghoff’s dead space. CONCLUSION: WLL can increase efficient alveolar ventilation by washing out the accumulated surfactant. However, the lavage fluid may be absorbed into the lung tissues immediately after WLL and result in an increase in the extravascular lung water. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13256-023-04085-8.