Background
Pulmonary alveolar proteinosis (PAP) is a rare disease characterized by the progressive accumulation of alveolar surfactant and hypoxemia. Whole lung lavage (WLL) is considered to be a standard therapy to improve oxygenation and quality of life in patient with PAP. Although large amount of warmed saline is used in WLL for the drainage of accumulated surfactant in alveoli, there are no established response criteria to evaluate its therapeutic effect. The aim of this preliminary study is to investigate the effect of single WLL on the efficient alveolar ventilation by measuring the elimination of CO2 and shunt related dead space using 2 patients with PAP.

Materials and Methods
In 4 trials of WLL in 2 patients, we measured CO2 elimination per breath (VTCO2br) by the indirect calorimetry (the breath by breath technique) and dead space calculated by Enghoff’s modification of Bohr’s dead space formula (shunt related dead space). Both parameters were measured  before the initiation of WLL (T1) and immediately and 12 hours after WLL (T2 and T3). Extravascular lung water index (EVLWI) was measured by PiCCO. Patients were ventilated with volume control mode with a fixed tidal volume of 6-8 ml/kg constantly during and after WLL.

Results and Discussion
The volume of saline used for WLL was 10600 ml (left) and 6000 ml (right) in case 1, and 3460 ml (left) and 11150 ml (right) in case 2. VTCO2br at T2 and T3 increased by 3.7 % and 5.3 % compared to that at T1, respectively. Shunt related dead space decreased by 20.8 % at T3 (mean±SD:0.32±5.4) compared to that at T1 (mean±SD:0.40±4.5). Mean EVLWI increased from 11.2 ml/kg before WLL to 14.1 ml/kg 12 hours after WLL. Increase in VTCO2br and decrease in shunt related dead space after WLL indicated that WLL increased efficient ventilation area related to gas exchange. However, lavage fluid might be partially absorbed into pulmonary interstitium, resulting in increase in extravascular lung water.

Conclusions
WLL improved efficient alveolar ventilation by decreasing the shunt area in 2 patients with PAP.

Effect of whole lung lavage on the elimination of CO2 and dead space in patients with pulmonary alveolar proteinosis