Figure 4. Correlation between alveolar dead space expressed in percentage of tidal volume and the percentage of fluctuation of tracheal NO concentration (TRACH-NO) during the administration of NO at 3 and 6 ppm in 11 patients with acute lung injury. At both inspiratory NO concentrations, there is an inverse correlation between the two values, suggesting that the absorption of NO from the lungs decreases with an increase in the alveolar dead space. The small numbers identify patient 11 who was studied twice, during the acute phase (1) and the recovery phase (2) of acute lung injury.