[Disorders of pulmonary gas diffusion in liver cirrhosis].

Unlabelled: There is no consensus on the pathogenesis and incidence of diffusion disorder in chronic liver diseases. It is supposed that the pathogenic mechanisms responsible for the reduction of diffusion capacity in liver diseases are multifactorial, including: ventilation-perfusion mismatching, diffuse interstitial pulmonary diseases and reduced transitory time in hyperperfused lung areas [1]. The increase of diffusion of oxygen molecules within dilated blood vessels during the inspiration of 100% O2 in patients with liver cirrhosis is called "diffusion-perfusion defect" or "alveolar-capillary oxygen disequilibrium" [3].

Aim Of The Study: The aim of the study was to determine how the inadequate pulmonary perfusion and intrapulmonary vascular dilatation affect the diffusion disorder in liver cirrhosis. One of the aims was to establish the correlative relations between diffusion disorder and cirrhosis grade according to Child classification.

Method: The study was performed over the period 1997-2000, including 50 patients with liver cirrhosis. They were diagnosed and treated at the Department of Hepatology and Gastroenterology, Clinical Centre of Serbia, Belgrade. Functional and morphological studies were based on the laboratory tests of liver function and histopathologic findings. The grade of liver insufficiency (A, B or C) was determined according to Child-Pugh score. The alveolar-arterial gradient was calculated from the gas analysis in the arterial blood, in supine and sitting position, in conditions of room air breathing and 100% oxygen. Diffusion parameters were measured by method of single inspiration of carbon monoxide. Spirometry and body pletismography were used for determination of ventilatory disorders.

Results: The reduced transfer factor (TLco) was recorded in 27 (54%) patients, while reduced transfer coefficient (Kco) was found in 33 (66%) patients. The mean TLco value was 7.27 (73%) in Child group A (n = 16); 6.98 (73%) in Child B group (n = 20); 6.65 (71%) in Child C group (n = 14). The comparison of these values in Child A, B and C groups by t-test showed no statistically significant difference (p > 0.05). The mean value of TLco was 7.24 (73%) in patients with spider naevi (n = 19), and 6.86 (72%) in patients without spiders (n = 31), without statistically significant difference among these mean values (t-test, p = 0.52). The restrictive ventilation disorders were present in 14 (28%) patients, while the reduced transfer factor was found in 27 (54%) patients. The incidences of restrictive ventilatory disorders and reduced transfer factor were compared (x2-test). The incidence of TLco, decrease was more significant than the incidence of restrictive disorders (p = 0.0082). The elevated alveolar-arterial gradient was present in 29 (58%) patients. No significant difference was found between alveolar-arterial gradient and diffusion disorders (x2-test, p = 0.62).

Discussion: There is no consensus on the incidence of diffusion disorder in chronic liver diseases. Robin et al. 1982 reported that only 20% of patients with liver cirrhosis had pathological diffusion, presuming that it was induced by reduction of transit time in hyperperfused lung regions [8]. Hourani et al. 1991 reported that the most frequent functional disorder was TLco decrease (52%) in the group of 116 patients planned for liver transplantation [1]. Krowka et al. 1992 found the lowest values of diffusion capacity in patients with Child C grade of liver cirrhosis [11]. Our results confirm the high incidence (54%) of diffusion disorder in liver cirrhosis, but the grade of liver insufficiency (Child score) does not correlate with the reduction of diffusion capacity. Several studies have reported various degrees of restrictive ventilatory disorders, with disproportionately higher reduction of TLco [1, 14, 15]. Our results confirm the higher incidence of diffusion disorder compared to restrictive disorders. Recent studies report that the isolated reduction of TLco is caused mainly by the intrapulmonary vascular dilatation, but the other factors also play the role (diffuse interstitial lung diseases without restrictive disorders in early stages, the passage through nonventilated alveoli, i.e. ventilatory perfusion mismatching and/or the other pulmonary vascular diseases) [16].

Conclusion: The impairment of diffusion capacity is a very common functional disorder in patients with liver cirrhosis and portal hypertension. Disproportionately, higher reduction of the transfer factor compared to restrictive ventilatory disorder, suggests that diffusion disorder is primarily induced by inadequate pulmonary perfusion. The isolated reduction of the transfer factor cannot be only explained in each case by intrapulmonary vascular dilatation.