Figure 1

Relationship between lung volume at relaxed end-expiration (Vrel) expressed as a fraction of total lung capacity (TLC) and body mass index (BMI). Open symbols identify measurements of patients 1 to 4, in whom Vrel was measured at zero end-expiratory pressure. Except for the outlier with a BMI of 71, in the expected population BMI range, Vrel/TLC declines by 1% TLC for each 1 kg/m² increase in BMI (r = -0.81).