Pulmonary artery pressure (Ppa) and continuous central venous oxygen saturation (SvO*) were measured with the patient in the supine position using a balloon tip fiberoptic catheter introduced percutaneously through a peripheral vein or the internal jugular vein. Pressure transducers were leveled to the midthorax. Resting Ppa and pulmonary capillary wedge pressure (Pew) were obtained over a period of one hour. At each FIo2, 10 to 20 iced saline cardiac output (CO) measurements were performed. read only
To avoid the confounding effect of wide variations in intrathoracic pressure on Ppa due to chronic lung disease, all pressure readings were taken at functional residual capacity (FRC) with respiration arrested, the patient maintaining an open glottis, and relaxed thoracic and abdominal musculature (FRC maneuver). Separate FRC maneuvers were performed for Ppa pulse pressure, mean Ppa, and Pew. Thus, between 30 and 60 FRC maneuvers were used to calculate the mean hemodynamic values under each Flo* condition. Compliance with the FRC maneuver was monitored by observing intrathoracic pressure reflected by the right atrial pressure tracing. Systemic artery pressure was continuously measured by an indwelling radial artery catheter. Following room air measurements, a variable mixture of nitrogen and oxygen (FIo2~0.13) was administered via tight fitting nasal mask with Oa flow adjusted to bring the patients ear oximeter Sa02 to 80 percent. This was maintained for 10 to 20 minutes after stabilization of Sv02. The same procedure was repeated with the patient breathing from a reservoir bag receiving 100 percent oxygen at a flow of 60 L/min, sufficient to maintain the subjects ear oximeter Sa02 at or above 99 percent. High flow oxygen was maintained 15 to 20 minutes before FRC maneuvers were begun to assure stability of pressures. Successive pressures over a given measurement period and FIo2 were judged stable if there was less than 2 mm variation.
Category: Lung Disease
Tags: chronic lung disease, Pulmonary function, pulmonary vascular hemodynamics