Abnormal Responses of Wasted Ventilation Fraction (VD/VT) during Exercise in Patients with Pulmonary Vascular Abnormalities

Abstract

The finding of a rise in VD/VT or failure of VD/VT to fall during exercise has been proposed as a useful noninvasive indicator of pulmonary vaso-occlusive disease in patients with unexplained dyspnea. However, we previously reported a normal fall in VD/VT during exercise in patients with pulmonary hypertension at rest and/or during exercise due to collagen vascular disease. To investigate further the relationship between pulmonary vascular abnormalities and VD/VT responses to exercise, we studied 4 subjects with severe hypoxemia due to cirrhosis or diffuse telangiectasia. We found an abnormal VD/VT response to exercise in these subjects despite normal pulmonary hemodynamics which effectively excluded hemodynamically significant pulmonary vascular obstruction. These findings provide further support for the lack of utility of the VD/VT measurement at rest and during exercise as a screening method for detecting pulmonary vaso-occlusive disease, since the VD/VT cannot only fall appropriately during exercise in patients with pulmonary hypertension but can also remain unchanged or rise during exercise in patients with normal pulmonary hemodynamics

Übersicht über die Entwicklung der invasiven Spiroergometrie (iCPET)

“…Auch konnte bei 4 Patienten mit einer Zirrhose bzw. Teleangiektasien mit normaler pulmonaler Hämodynamik in Ruhe und Belastung kein physiologischer Abfall der V D /V T unter Belastung nachgewiesen werden [76]. Somit kamen die Autoren zu dem Schluss, dass die V D /V T kein geeigneter Screening-Parameter für eine pulmonale Perfusionsstörung darstellt.…”

“…Es soll nicht unerwähnt bleiben, dass es hierzu auch kontroverse Daten gibt. So wurde bei 11 PAH-Patienten mit Kollagenosen gezeigt, dass eine gestörte pulmonale Hämodynamik nicht immer mit einer Zunahme der V D /V T einhergeht 75 . Auch konnte bei 4 Patienten mit einer Zirrhose bzw.…”

Role of Cardiopulmonary Exercise Testing in Patients with Pulmonary Vascular Disease

“…Disadvantages, however, include the fact that the clinician must consider cardiac causes of exercise intolerance in a young patient in ordering the test and underestimation of PAP in certain patients [26]. Perhaps even more important, some symptomatic patients appear to have only mild PHTN at rest or none, but with the stress of exercise (which makes echocardiography technically difficult) dynamic PHTN is elicited [25,27]. If dynamic PHTN represent early and more treatable disease [5,28], a screening test done solely at rest may be inappropriately insensitive.…”