PULMONARY VENTILATION AND THE CARBON DIOXID OF THE BLOOD
Journal of the American Medical Association
annihilation. Rehabilitation hospitals in which the badly injured are supplied with artificial limbs and other devices are working successfully and converting the apparently hopelessly maimed into productive, selfsupporting citizens. In fact, these institutions con¬ stitute one of the great triumphs of military and con¬ servative medicine. Every wounded and sick soldier can be instantly located and his condition reported to his friends. In this way the discontent arising from anxious waiting
... anxious waiting for news is avoided. There has been no breakdown in the medical service in the great armies of Europe, as has been the case so often in the past and with us in 1898. When a son is killed in battle, parents seek and find consolation in the proud knowledge that he has died fighting for his home and his country; but when he is wounded or sick and dies from neglect, there is no consolation, and in the most patriotic soul a bitterness against those in authority develops. All this and much more might be said concerning the efficiency of the medical service of our chief allies. What is the explanation of its efficiency? The answer is that the medical officer is given support backed by rank and authority. A line officer in the British Army hesitates a long while before he rejects the advice of his medical colleague, because that colleague has rank and authority commensurate in some degree at least with his own, and is recognized as his superior in the special line of work. Compare this with the record of the congressional inquiry into the conduct of the War Department in the war with Spain, when, according to his own testimony, the commanding officer at Chickamauga in 1898 ostentatiously drank from a well con¬ demned by his medical officer, while his hospitals were filled with typhoid fever patients. We have gone jnto this war with the medical officer invested with no more authority than he had in 1898. Is it unreasonable to ask if we are to repeat the experiences of that time? However, we are told that the line officer of today is much wiser than his predecessor of twenty years ago, and since he makes this statement himself, we must give it credence. We certainly hope that it is true. It is the duty of the medical profession to protest against this condition. The medical men of this country are not slackers, as is shown by the fact that more than one seventh of their total number have voluntarily offered their services to their country, notwithstanding the failure of those in authority to give the reasonable recognition asked. We have asked for increased authority, and in the Army this can be secured only by high rank, because when a medical man goes into the service the government puts its stamp on him just as it does on the coin of the realm ; and 30 cents will not buy a dollar's worth of anything. So far the protest has fallen on deaf ears. Medical men will play the game and do their duty, whatever may be the verdict in this matter; but it should be clearly understood that they are going into the game under a heavy handicap. They will do the best they can ; but if discontent should arise from poor or poorly prepared rations, if respiratory diseases pre¬ vail as the result of overcrowding, if pneumonia becomes widespread because barracks are not heated and soldiers are not warmly clothed and amply pro¬ vided with blankets if all these things happen, the medical officer will continue to do the best he can under the conditions, but he will not be responsible for the conditions. PULMONARY VENTILATION AND THE CARBON DIOXID OF THE BLOOD The renewal of the air in the lungs, with which the blood exchanges its gaseous constituents, is brought about by muscular movements, which are under the control of the nervous system. When it was discovered that the functioning of this regulatory mechanism was in large part dependent on the chemical composition of the blood reaching the respiratory center, the natural tendency was to ascribe the stimulation of the latter to a fall in the oxygen tension in the circulatory system. It is now understood, however, that until the oxygen tension falls very decidedly, no noteworthy change in the ventilation of the lungs takes place so long as an increase of carbon dioxid tension is prevented. The classic investigation of Haldane and Priestley, reported in 1905, has demonstrated in a convincing way that the total volume of air sent in and out of the lungs in a unit of time by the respiratory movements is regulated by the carbon dioxid tension of arterial blood, which is the same as that of the alveolar air of the lungs. Subsequently, Haldane and his co-workers showed, in 1913, that the alveolar oxygen pressure can be varied within wide limits with¬ out sensibly affecting the excitability of the respiratory center to carbon dioxid.1 Whether certain types of clinical dyspnea are due, primarily, to retained carbonic acid, rather than to other acids formed in metabolism, has frequently been asked by those engaged in the study of acidosis in its relation to pathologic symptoms. The difficulties in answering this question have been due in part to the lack of suitable methods for the detection of very small deviations from the normal in the composition of the blood. Indirect methods, such as the determination of the alveolar carbon dioxid and the total carbonate con¬ centration of the blood, have become popular in the study of the interrelations between the composition of the blood and the respiratory exchange. In the physio¬ logic laboratory of the Western Reserve University School of Medicine, Cleveland, Scott2 has noted in 1. Campbell, J.