Blood gases at rest and during exercise in patients with alpha1-Pi deficiency

Alpha1-protease inhibitor (Pi) deficiency is associated with a protease-anti-protease imbalance leading to premature destruction of lung tissue and early emphysema. Little is known about the blood gases of these patients in the various stages of the disease. The purpose of this study was to evaluate blood gases in patients with alpha1-Pi deficiency when patients were at rest and during exercise, and to correlate these with lung function measurements. A total of 369 patients with severe alpha1-Pi deficiency had pulmonary function test and blood gas analysis, 282 also had blood gases taken during steady state submaximal exercise testing. Only 21% of the patients had normal blood gases at rest; 71% had mild hypoxaemia; 8% had severe hypoxaemia. Surprisingly, 61% of the patients with mild lung disease and a FEV1 of more than 65% predicted were hypoxaemic. During exercise 65% of the patients had a drop in PO2 of more than 0.40 kPa. FEV1 was a significant predictor for the PO2 values at rest and during exercise. During exercise the arterial-alveolar gradient increased in about 50% and decreased in 25% of the patients. Many patients with alpha1-Pi have blood gas abnormalities. Impaired blood gases in early stages of the disease result in a discrepancy between lung function parameters and blood gases. FEV1 measurements inadequately capture the extent of lung disease in patients with alpha1-Pi deficiency, and both blood gases at rest and during exercise are needed in the assessment of all stages of the disease.