Assessing pulmonary congestion in left sided heart failure using pulmonary gas exchange parameters

In clinical practice there is a need for a method to measure pulmonary congestion in left sided heart failure. Current methods, including auscultation and chest X-rays, are imprecise, semiquantitative, and assess fluid accumulation, not impairment of lung function. This paper evaluates the use of a mathematical model of pulmonary gas exchange as a measure of pulmonary congestion in left sided heart failure. Eleven patients with pulmonary congestion were investigated on admission and during anticongestive therapy. Inspired oxygen fraction was varied, and measurements of ventilation and blood gases were used to estimate model parameters i.e. pulmonary shunt and ventilation-perfusion (V/Q) mismatch (ΔPO2). On admission, patients´ parameters were: shunt, median 9.9 % (range 0.0 - 22.2 %), and ΔPO2, 4.3 kPa (range 1.8 - 6.1 kPa), values outside the range of normal subjects (shunt, median 1.2 % range 0.0 -11.1 %, ΔPO2, median 0.1 kPa range 0.0 - 2.0 kPa) (p<0.001). During therapy both shunt and V/Q mismatch were reduced (shunt, median 7.8 % range 3.7 -14.4 %, ΔPO2, median 2.8 kPa range 0.2 - 3.9 kPa). This study illustrates a possible role for gas exchange parameters to quantify pulmonary congestion in patients with left-sided heart failure, and to monitor the effect of therapy.