[Is ventilatory anaerobic threshold useful for preoperative assessment?]

The anaerobic threshold (VAT), obtained by measurement of ventilatory volume and by expiratory gas analysis, and the anaerobic threshold (LAT), obtained directly from the lactic acid value in the blood, were compared and evaluated during exercise load in 25 patients with mitral valve disease. Exercise loading was performed with an ergometer using a multistep method of increases of 5 W (Group A, 11 cases) or 10 W (Group B, 14 cases) per minute. The oxygen uptake value at the points of 0.5 mmol.l-1 and 1.0 mmol.l-1 increase in the lactic acid values when compared with the starting values were designated as 0.5 LAT and 1.0 LAT. VAT was found in 4 of 11 (36%) patients in Group A and in 12 of 14 (86%) patients in Group B and the ratio obtained was significantly higher in Group B than in A. The 0.5 LAT values for Group A and B were 2.4 +/- 0.5 and 2.2 +/- 0.3, respectively. The 1.0 LAT values were 2.9 +/- 0.7 and 2.7 +/- 0.4, and among the two groups no significant difference was found concerning 0.5 LAT or 1.0 LAT. VAT was seen in 16 or 25 patients and the average VAT value of the 16 was roughly at the midpoint between the average values for 0.5 LAT and 1.0 LAT. Therefore in patients in which VAT was seen with the expiratory gas method, VAT and LAT values were basically equivalent. However, in Group A, VAT was seen in only 4 of 11 patients and it is a fact that it is difficult to find VAT without a suitable exercise load.