Systemic blood pressure (Psa), central venous, pulmonary artery, and pulmonary artery occlusion pressures were transduced (Transpac II, Abbott Critical Care, Chicago) and recorded (ТА 2600, Statham Gould, Oxnard, Calif). A horizontal plane through the shoulder was taken as zero reference point for blood pressure measurements. Cardiac output (CO) was measured with the thermal dilution technique (Oximetrix 3, Abbott Critical Care, Chicago).
Gas flow was measured between the tracheal tube and the Y-piece of the ventilator circuit with a heated pneumotachograph (3791, Hans Rudolph, Kansas City, Mo), connected to a differential pressure transducer (DP 1030871, Validyne, Northridge, Calif). Tidal volume (Vt) was derived from the integrated gas flow signal. Expiratory minute ventilation (Ve) was measured for control with a calibrated respirometer (Wright) at the outlet of the gas mixing chamber. Airway pressure (Paw) was measured at the proximal end of the tracheal tube with a differential pressure transducer (MP45-871, Validyne, Northridge, Calif). Esophageal pressure (Pes) was measured with balloon catheter (Mallinckrodt, Argyle, NY) connected to a differential pressure transducer (MP45-871, Validyne, Northridge, Calif) as described previously. canadian neighbor pharmacy
Arterial and venous blood gases and pH were determined immediately after sampling with standard blood gas electrodes (model 1303, Instrumentation Laboratories, Lexington, Mass). Oxygen saturation of the arterial (Sa02) and mixed venous (Sv02) blood, and total hemoglobin and methemoglobin concentrations were determined with a CO-oximeter (model 282, Instrumentation Laboratories, Lexington, Mass). Fractions of inspired oxygen (FI02) and carbon dioxide and fractions of mixed expired oxygen (FE02) and FECO2 were determined with a scattering gas analyzer (Raman, Rascal II, Ohmeda, Louisville, Co).