[Gas exchanges on effort in diffuse pulmonary emphysema (author's transl)]

With the aim of determining the causes of hypoxia which develops on effort in certain emphysema sufferers, gas exchange at rest and effort were studied in 28 patients with diffuse pulmonary emphysema (including one third with large bullous form), with the exclusion of any clinical evidence of bronchitis or asthma. These patients, selected on the basis of the similarity of their clinical, radiological, mechano-spirographic and diffusion criteria, behaved very differently in terms of their gas exchanges during a moderate effort (mean VO2 = 750 ml/mn). The first group of 12 subjects showed a significant fall in pO2 (- 10.5 mmHg on average). The second group of 16 subjects improved by 4 mmHg hypoxaemia present at rest (though more marked than in the first group). The various parameters studied of ventilation, blood gases, and diffusion appeared to indicate a preponderant role played by distributive problems, and in particular the Qs/Qt ratio (calculated on the Fenn and Rahn pO2 and pCO2 diagram) which worsened on effort in the first group whilst it improved in the second, as well as the greater degree of desaturation of mixed venous blood on effort in the first group. The difficulties of a valid physiopathological interpretation are emphasized.