Abstract
In these case report, the results of late dead space fraction (fDlate), end-tidal alveolar dead space fraction (AVDSf), arterial-alveolar gradient CO2 [P(a-et)CO2], and slope phase 3 of spirogram of two patients who underwent thromboendarterectomy for pulmonary embolism (PE) are shown. PE was diagnosed by pulmonary scintigraphy, helical tomography, and pulmonary angiography. The calculation of fDlate, AVDSf and P(a-et)CO2 was based on volumetric capnography associated with arterial blood gas analysis. The pre-operative fDlate of the first patient was 0.16 (cutoff 0.12) and AVDSf was 0.30 (cutoff 0.15). However, the fDlate of the second patient was false-negative (0.01) but, the AVDSf was positive (0.28). Postoperative fDlate of the first patient was -0.04 and AVDSf was 0.16; for the second patient, the values were 0.07 and 0.28, respectively. The association of these capnographic variables with image exams reinforces the importance of this noninvasive diagnosis method.
Highlights
It is well-known that unexpected death can occur in consequence of pulmonary thromboembolism (PTE) and anticoagulation is often effective in reducing the possibility of a new embolic event and death
Helical computed tomography (HCT) showed right ventricular filling pressure failure compatible with left descending interlobar artery thromboembolism with areas of pulmonary infarction in lower lobe of left lung. This patient was considered for surgical treatment because of right ventricle occlusion, besides presenting right pulmonary artery thromboembolism, which was highlighted by arteriography
Patient 1 presented a PTE diagnosis by fDlate e alveolar dead space fraction (AVDSf) values, which were confirmed by preoperative images and improvement of postoperative images as well as the capnographic variables
Summary
It is well-known that unexpected death can occur in consequence of pulmonary thromboembolism (PTE) and anticoagulation is often effective in reducing the possibility of a new embolic event and death For this reason, in patients in whom PTE is suspected, noninvasive methods would be preferred and available to be incorporated as part of bedside evaluation. The authors have performed a study enrolling 38 patients with suspected PTE and observed that fDalte was above than 0.12 in normal individuals, and in patients with COPD fDlate was below than 0.12 Another capnographic variable, the end-tidal alveolar dead space fraction (AVDSf) [2] calculate from the equation PaCO2 - PetCO2 / PaCO2, “corrected” fDalte falsenegative result. In the present two-case report, it was possible to correlate the result of pulmonary artery pre and post-thromboendarterectomy scan with fDlate, AVDSf, and the CO2 arterial-alveolar gradient [P(a-ET)CO2]
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