Effect of lung resection on blood lactate threshold in lung cancer patients

We studied the effect of a decrease in vital capacity (VC) on the blood lactate threshold detected during exercise in 16 preoperative (PRE) and 10 postoperative (POST) lung cancer patients who had undergone lobectomy or pneumonectomy. The PRE patients were selected on the basis of having normal preoperative pulmonary function. The POST patients were selected on the basis of having normal preoperative pulmonary function and a postoperative VC of less than 80%. The oxygen consumption/body surface area at a 2.2 m.mol·l^-1 arterial lactate concentration ( {Mathematical expression}/ BSA at La-2.2) was adopted as the blood lactate threshold. VC/BSA in the POST group significantly correlated with {Mathematical expression}/BSA at La-2.2 (r=0.85, P<0.01), but not in the PRE group. SaO₂ at La-2.2 was 95.4+-1.5% in the PRE group and 95.2+-1.3% in the POST group. SaO₂ at La-2.2 did not correlate with VC/BSA in either group. The hemoglobin concentration (Hb) in the arterial blood correlated significantly with VC/BSA in the POST group (r= 0.65, P< 0.05) but not in the PRE group. These results indicate that {Mathematical expression}/BSA at La-2.2 was restricted by VC in patients with restrictive pulmonary function disorder. Of the three elements of oxygen delivery, Hb was a limiting factor for {Mathematical expression}/BSA at La-2.2 but SaO₂ was not. Cardiac output, which was not measured in our study, was speculated to be another limiting factor for _388-05 at La-2.2