Gas Exchange in Chronic Thromboembolism after Pulmonary Thromboendarterectomy: Methods (Part 2)
Mixed expired gas samples were also analyzed for respiratory gas concentrations using a mass spectrometer. Arterial and mixed venous blood gases and oxygen contents were measured in duplicate immediately after collection using a blood gas analyzer and COoximeter.
A six-view perfusion scan was performed before and after surgery. The subjects were injected intravenously while in the supine position, with ”Tc human albumin macroaggregates. The average activity per injection was 1.5 mCi, each dose containing approximately 350,000 particles. The subjects were imaged sitting upright. The average scan time, including subject positioning, was approximately 40 minutes. A total of 500,000 counts was collected in the anterior, left lateral, and right posterior oblique views. The posterior, right lateral, and left posterior oblique views were imaged for the same time period as the corresponding contralateral view, so that the rate of isotope accumulation in the two views could be compared. All subjects also underwent Xe ventilation scanning, breathing a 10 mCi/L Xe-air mixture in a 6-L xenon ventilator to equilibrium followed by washout imaging. buy levaquin online
Finally, before and after surgery, each patient underwent spirometry using a volume displacement spirometer, lung volume measurements using variable pressure body plethysmography, and measurement of single breath diffusing capacity using a water-sealed spirometer manual system with an infrared CO analyzer. Spirometry and diffusion capacity measurements were performed in accord with ATS recommendations- with the exception of Deo washout and sample collection volumes, which are slightly above the ATS recommendations (mean 120 percent and 110 percent of recommended volume) because a manual collection system was used. The Deo was adjusted for hemoglobin concentration using the Cotes equation. Predicted values for the measurements were calculated using the formulas and lower limits of normal developed by Crapo et al for spirometry, Goldman and Becklake for lung volumes, and Miller et al for diffusing capacity. Results were analyzed using Students paired f-tests.