Page 171 - Assessing right ventricular function and the pulmonary circulation in pulmonary hypertension Onno Anthonius Spruijt

recorded using a Powerlab data acquisition system (Chart 5 for Windows, AD Instruments, Sydney, Australia), resting mixed venous oxygen and arterial oxygen blood samples were drawn from the pulmonary artery and radial artery catheters and breath-by-breath measurements were made of VO2, VCO2 and VE (Vmax229, Sensormedica, Yorba Linda, CA, USA).
The exercise protocol consisted of one minute of unloaded cycling followed by two minutes of submaximal exercise (40% of maximal workload (Wmax) during maximal CPET) with continuous recording of hemodynamics. Near the end of exercise, mixed venous and arterial blood samples were again drawn from the pulmonary artery and radial artery catheters.
For subjects whose Wmax was <150W, submaximal workloads were immediately increased to 40% of Wmax after one minute of unloaded exercise. For subjects with a Wmax >150W, a direct increase to 40% of Wmax was too large and therefore these subjects were exercised at one additional intermediate step of one minute of exercise at 35W in PH patients and 45W in control subjects. This intermediate step allowed data comparison at approximately similar absolute work rates in all subjects.
Measurements
CO at rest and during exercise were measured using the direct Fick method. SV was calculated as CO divided by heart rate (HR). Cardiac output and SV were indexed for body surface area (BSA). Pulmonary artery pressures (PAP) were averaged over a period of 15 seconds to be sure that the PAP was measured over multiple respiratory cycles.
The end-systolic elastance (Ees), a load-independent measure of RV contractility, was calculated at rest and during submaximal exercise as:
The maximal isovolumic pressure (Pmax) was determined using the single beat method [11, 12]. Pressure data were averaged over several beats to reduce respiratory variations. The load on the RV was calculated as arterial elastance (Ea):
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