Alveolar dead space and capnographic variables before and after thrombolysis in patients with acute pulmonary embolism

Marcos Mello Moreira¹, Renato G G Terzi¹, Carlos Heitor N Carvalho², Antonio Francisco de Oliveira Neto³, Mônica Corso Pereira⁴, Ilma Aparecida Paschoal⁴

¹Department of Surgery, State University of Campinas, School of Medical Sciences; ²Department of Cardiology, State University of Campinas, School of Medical Sciences; ³Intensive Care Unit of the State University of Campinas, School of Medical Sciences; ⁴Department of Pulmonology, State University of Campinas, School of Medical Sciences, Campinas, Brazil

Abstract: Pulmonary embolism (PE) is a common condition. The central aim of this study was to describe the use of volumetric capnography (VCap) before and after fibrinolytic treatment of major PE. Lung scintigraphy was used as a base of comparison for the results of this treatment. We describe the cases of two conscious and spontaneously breathing patients (20- and 24-year-old women) with major PE undergoing thrombolysis. Curves of CO₂ were obtained by VCap and associated with arterial blood gas analysis and D-dimer. The pattern of VCap was compared with the VCap of health volunteers. Parameters also calculated were: P(a-et)CO₂ gradient, alveolar dead space fraction (AVDSf ), late dead space fraction (f Dlate), and slope phase III (Slp III). The VCap results before and after thrombolysis for patients 1 and 2 were, respectively, P(a-et)CO₂: 12.6 to 5.8 and 7.9 to 1.6 (mmHg); AVDSf: 0.46 to 0.18 and 0.25 to 0.05; fDlate: 0.46 to 0.21 and 0.24 to 0.04; Slp III: 1.75 to 5.10 and 1.21 to 5.61 (mmHg/L). Lung scintigraphy was used to compare VCap results from the two subjects with VCap results from healthy volunteers and pigs before and after treatment associated with arterial blood gas, D-dimer, and showed satisfactory agreement.

Keywords: pulmonary embolism, capnography, respiratory dead space, thrombolysis, fibrin fibrinogen degradation products/fibrin fragment D