In a recent study, Kawakami et al, suggested that mixed venous blood oxygenation (PvO2) is one of the most important prognostic factors in patients with chronic obstructive lung disease (COLD). The aim of the present study was to evaluate the predictive power of PvO2 in 99 of our own patients with COLD. Lung function and pulmonary hemodynamics were investigated in a stable period of the disease. Follow-up studies were done at least 3 years after initial work-up. Observation time was 5.4 +/- 1.6 years in patients who survived (S) and 2.8 +/- 2.3 years in patients who died (N-S). The two groups differed significantly in the following variables (mean +/- SD for survivors and non-survivors): VC 3.0 +/- 1.0 1 and 2.3 +/- 8.1 1, FEV1 1.6 +/- 0.9 1 and 0.9 +/- 0.4 1, PaO2 9.6 +/- 1.4 and 8.3 +/- 1.7 kPa, SaO2 94 +/- 3% and 90 +/- 6%, PaCO2 5.0 +/- 0.9 kPa and 5.9 +/- 1.1 kPa, mean pulmonary arterial pressure (PAP) 2.6 +/- 0.7 kPa = 19.5 +/- 5.6 mmHg and 3.9 +/- 1.7 kPa = 29.4 +/- 12.9 mmHg, and hematocrit (Ht) 47 +/- 5% and 51 +/- 7%. The following three variables did not differ significantly: cardiac index 3.8 +/- 1.8.1 and 3.3 +/- 1.6, PvO2 5.6 +/- 0.9 kPa and 5.3 +/- 0.9 kPa, and coefficient of oxygen delivery (COD) 5.69 +/- 2.28 and 5.29 +/- 2.35. The number of patients with signs of tissue hypoxia (PvO2 less than 4.66 kPa) was similar in both groups, 7 (S) and 9 (N-S).(ABSTRACT TRUNCATED AT 250 WORDS)