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Abstract

While the hemodynamic effects of spontaneous respiration are normally considered minimal, large increases in negative intrathoracic pressure (ITP) are known to impair left ventricular (LV) function. Increased negative ITP is a hallmark of obstructive respiratory disease, and is often accompanied by elevations in lung volume and changes to the pulmonary vasculature, both of which have adverse effects on LV function through both series and direct ventricular interaction (DVI). While the hemodynamic effects of these stressors in isolation are generally well established, the interaction of these mechanisms, and their summative effect on LV function, has not been investigated. This study examined the hemodynamic effects of increased negative ITP, dynamic lung hyperinflation (DH), increased pulmonary vascular resistance (PVR) and increased preload (VL) alone and in combination in healthy, spontaneously breathing humans using echocardiography to evaluate LV volumes and geometry. Reducing ITP on inspiration to -20 cmH₂O significantly decreased LV SV by 7% (p