Figure 3.

Accuracy of the nitrogen washin/washout technique. (a) The relation between the EELV measured by increasing the FiO₂ as a function of the EELV obtained decreasing FiO₂. The EELV obtained increasing the FiO₂ was -56 + 1.0078 multiplied by the EELV obtained decreasing the FiO₂ (r² = 0.84, p < 0.0001). (b) The Bland-Altman plot of the EELV measurement obtained increasing the FiO₂and the EELV obtained decreasing the FiO₂. The x axis shows the mean of the two measurements and the difference between the EELV measured by increasing FiO₂ and the y axis shows the EELV obtained decreasing FiO₂ (average difference 48 ± 165 ml, limits of agreement -117–213 ml).