Figure 2.

Diaphragm muscle force–frequency relationships in control and mechanical ventilation with and without applied positive end-expiratory airway pressure. Values are mean ± SE (n = 6 animals in each group). *P < 0.01 for controlled mechanical ventilation (CMV-8) compared with control and assist-control mechanical ventilation (AMV-8) for twitch force; CMV and CMV-8 versus corresponding modes of mechanical ventilation without and with positive end-expiratory pressure (PEEP), respectively, at stimulation frequencies of 10 to 100 Hz. The number 8 next to the mode of ventilation denotes the set CPAP or PEEP of 8 cmH₂O. Force was normalized for muscle cross-sectional area (see Material and methods for calculation).