Fig. 1.

The effects of increasing positive end-expiratory pressure (PEEP) on lung compliance (N = 9) and dead space ventilation (N = 9). Every patient is depicted with a different symbol and color. a Lung compliance decreased with increasing PEEP levels in 8 patients. b Dead space ventilation according to Bohr increased in all patients with increasing PEEP levels. c In response to higher PEEP levels, dead space ventilation according to Enghoff modification (global gas exchange impairment) increased in 3 patients, first decreased and then increased in 3 patients, decreased in 2 patients, and had no effect in 1 patient