Gas Exchange in Chronic Thromboembolism after Pulmonary Thromboendarterectomy: Results (Part 4)
In a single case (No. 7), the postoperative log SDq increased, due to the development of a very small amount of perfusion to low Va/Q respiratory units. The remainder of the Va/Q distribution was unchanged postoperatively. Radionuclide scanning revealed resolution of segmental abnormalities in the operated segments in every case, although some subsegmental perfusion defects remained.
The magnitude of improvement in Va/Q matching, as measured by the change in log SDq, correlated well with the magnitude of preoperative vascular obstruction (r = 0.96) when a single outlier (No. 7) was excluded (Fig 2). It was less strongly correlated with the magnitude of preoperative Va/Q mismatching (r=.60). The improvement in Pa02, (P(A-a)Oz, and PaP were less strongly correlated with the magnitude of preoperative obstruction (r = 0.82, 0.67, 0.62 respectively), or with the magnitude of preoperative Va/Q mismatching (r = 0.55, 0.55, 0.63 respectively). Surprisingly, the magnitude of improvement in Va/Q matching, gas exchange, or hemodynamics also correlated poorly with the estimated magnitude of surgical reduction in vascular obstruction. Correlation coefficients were 0.34, 0.54, and 0.23 for log SDq, P(A-a)02, and PaP vs the change in percent obstruction, respectively. buy ortho tri-cyclen online
One gas exchange parameter which was not improved by thromboendarterectomy was the absolute diffusing capacity. The postoperative Deo (66 ±9 percent predicted) was not significantly different from the preoperative value (63 ±11 percent predicted, p>0.05). The ratio of single breath diffusing capacity to single breath lung volume was also unchanged (77 ±13 percent predicted postoperative vs 78 ±13 percent predicted preoperative).
Figure 2. The relationships of the change in Va/Q matching to the degree of preoperative vascular obstruction, d Log SDq is (preop-postop) Log SDq.