Figure 4. Changes in central venous pressure, cerebrospinal fluid pressure, epidural space pressure, and epidural vein pressure during positive-pressure ventilation with atmospheric pressure (PEEP) during expiration (zero end-expiratory pressure) and with 10 cm H2O PEEP. The influence of PEEP is shown for the thoracic (n = 7) and lumbar (n = 8) regions. Although PEEP increased all pressures, the transmural gradient was unchanged. Values are mean +/- 1 SD.