The hypoxia tolerance test of the heart in children.

Summary Present knowledge of latent cardiac decompensation in children is inadequate.Accordingly, an attempt has been made to come closer to the problem of the reserve forces of the child heart by means of a comparative investigation of the tolerance tests performed on healthy as well as on sick children. For the tolerance test, respiration of air deficient in oxygen has been chosen,as applied earlier to adults by, among others, Dietrich and Schwiegk, Levy and Larsen. A special apparatus suitable for children of all ages, as well as for adults,has been constructed. It consists of an adjustable metal ring with a hood of Plexiglas mounted on one of the ends of the bedstead. Oiled silk is attached to the metal ring which is applied to the shoulders, back, and chest of the patient. In the respiration chamber thus obtained, nitrogen and air are introduced, the oxygen content of which acquires the desired constant value after four and one-half minutes. In the present test series, 9 per cent oxygen was used during ten minutesof tolerance testing. The result, which is of a preliminary nature, is briefly as follows: Thirtynormal cases reacted negatively. Sixteen of twenty-five cases of different heart diseases reacted positively. Seven of these cases represented active rheumatic carditis, four cases being patent ductus Botalli, one case another congenital vitium without cyanosis, one case of morbus ceruleus, and three cases of postmyocarditic conditions. In addition, a group of twenty-nine cases of third sound gallop has been subjected to the tolerance test; these patients have been examined by Carlgren and will be included in his work regarding the gallop rhythm. Nine cases (31 per cent) reacted positively, the twenty remaining, negatively. This result supports Carlgren's theory that the third sound gallop is, to some extent, to be considered a myocardial injury. An examination of the T-waves during the hypoxia test has shown that a considerably more marked depression of the T-wave in all three leads occurred in the cases reacting positively than in those which were not affected by the respiration of air deficient in oxygen. The pulse increased in rate during the tolerance test, both in normal andin pathologic cases. However, the data are still too limited to permit the drawing of any far-reaching conclusions. The test, which is easy to perform, takes only 15 minutes, is free from risks, and will, no doubt, be found suitable for routine clinical work. In contrast to the working tests with registration of the cardiac effect after the completion of the exertion, the respiration of air deficient in oxygen, as in the present case, has the advantage that the heart's reaction can be recorded during the actual tolerance test. This is, in all likelihood, particularly valuable with regard to children, where the heart is characterized by a rapid mode of reaction. Thus, all the changes appearing during the hypoxia test, in normal as well as pathologic cases, had resumed their original value five minutes after the termination of the tolerance test. For the purpose of studying more closely the effect of the hypoxia on thecirculation, larger normal and pathologic series are being planned where, apart from electrocardiographic and phonocardiographic registrations and pulse recording, measurements of the oxygen-saturation of the blood will also be carried out.