Meaning of physiological dead space ventilatio (VD/VT) increase in patient with precapillary pulmonary hypertension (PH)

Introduction: In PH, VD/VT is increased as a consequence of decreased perfusion in ventilated lung1. Thus, the ventilation inefficiency, in terms of gas exchange, is originated by the pulmonary vascular abnormalities which in turn affect pulmonary hemodynamics. Aim of the study: To investigate wether the degree of VD/VT increase correlated with pulmonary hemodynamics (RHC), echocardiographic (Echo) and functional parameters (6MWT and MRC dyspnea score index) in PH patients. Methods: We retrospectively evaluated 15 patients with PH (5 idiopathic, 5 related to scleroderma, 5 related to chronic thromboembolic disease) who underwent RHC, VD/VT, Echo and, 6MWT, and MRC index measurements. Results: Mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) were 44±10 mmHg and 13±5 Wood units, respectively. VD/VT was 29±6 mmHg. Right atrium (RA) and ventricle (RV) volumes at Echo were 45±10 and 33±7 mm, respectively. VD/VT correlated with: cardiac index (r-.61; p.02), PVR (r .73; p<.01), RA (r .74; p.001), RV (r .79; p<.001), 6MWT (r .-0.58; p.03), MRC score (r .60; p.02). Conclusions: in PH, VD/VT seems an useful index to identify hemodynamic and functional derangement. It may be useful for clinical monitoring of this disease. 1. Ting H, et al. Chest 2001;119:824.