Fig. 2

Pressure waveforms of CVP, Pes, Paw, and Ppl. Pressure waveforms during the occlusion test (a) and mechanical ventilation (b). a During chest compressions in the occlusion test, the waveforms of Pes and Paw fluctuated similarly; the ratio of the ΔPaw to the ΔCVP was determined and expressed as “κ”. b During mechanical ventilation, the ΔPpl can be calculated by multiplying “κ” with the ΔCVP, assuming that the ratio of the ΔPpl to the ΔCVP during the occlusion test and mechanical ventilation is the same. CVP, central venous pressure; Paw, airway pressure; Pes, esophageal pressure; Ppl, pleural pressure; ΔCVP, change in central venous pressure; ΔPaw, change in airway pressure; ΔPes, change in esophageal pressure; ΔPpl, change in pleural pressure