The birth of the single breath (sb) T_LCO: the oxygen secretion controversy

Whether or not the lungs actively secreted oxygen, particularly under stressful conditions (severe exertion, alveolar hypoxia), was an argument which continued for more than 50 years (1870–1923), and involved some of the most distinguished respiratory physiologists of that era, such as JS Haldane, Christian Bohr and August Krogh. The denouement, as told by Krogh's daughter, Bodil Schmidt-Neilsen,1 began 11 years earlier in 1904 when a Danish medical student, Marie Jørgensen, attended a class taught by August Krogh, an instructor in physiology in Christian Bohr's department. They were attracted to each other and married in 1905, and Marie (figure 1) joined August (a Nobel Prize winner in physiology and medicine in 1920) in some aspects of his research. The subsequent publication of a paper in 1915, 100 years ago this year, by Marie Krogh in the Journal of Physiology2 was the pivotal moment in the story. The influence of this paper “The diffusion of gases through the lungs of man”2 continues to this day, long after the oxygen secretion question was settled (in Marie Krogh's favour). Nowadays, pulmonary function laboratories throughout the world use a modification of her single breath transfer factor for carbon monoxide (T_LCO.sb) test, known in North America as the D_LCO.sb (carbon monoxide diffusing capacity); it is an essential part of routine lung function screening, and the only non-invasive test (apart from pulse oximetry) of the gas exchanging efficiency of the lung.

The oxygen secretion story has been told many times.1 ,3 ,4 A century ago, the idea that Claude Bernard's milieu intérieur might be stabilised by alveolar cells secreting oxygen at times …