Hurley L. Motley

PULMONARY EMPHYSEMA: PHYSIOLOGIC FACTORS IN DIAGNOSIS AND ADVANCES IN THERAPY

A satisfactory procedure for measuring vital capacity is from spirogram tracings made with an apparatus such as the Collins 13.5-liter respirometer (1). This method provides not only a dynamic recording of the total vital capacity but a volume measurement with respect to time (three seconds), and permits study of the characteristic features of the breathing curve (Fig. 1). Vital capacity is commonly measured by having the individual take a deep breath and then blowout the air as far as possible. It may also be determined by having the subject first blow the air out of the lungs as far as possible and then take in a maximum deep breath. There is no evidence that the latter procedure is not as valid as the former, for clinical study. In the normal individual there is no significant difference between the results of the two methods, but in patients with pulmonary emphysema a more accurate value is frequently obtained by the second method. In either procedure, the measurement obtained is the volume difference between maximal inflation and maximal deflation of the lungs. The level of the diaphragm may shift with position and activity. For this reason, the determination of vital capacity in two separate steps (as the sum of inspiratory reserve and expiratory reserve) is subject to error. If the vital capacity is significantly greater when the patient is lying down than when he is standing up, a severe degree of pulmonary insufficiency is indicated.

Sodium Bicarbonate in Respiratory Acidosis

To the Editor:— Readers may get the wrong impression from Dr. Plums letter. The primary approach is to improve the airways and increase alveolar ventilation. A very low arterial blood pH is incompatible with life if allowed to persist; hence it is desirable to elevate the pH out of the low critical range as rapidly as possible. In such cases sodium bicarbonate can be added to a continuous intravenous drip, using at least 10 to 20 gm of sodium bicarbonate in a liter of fluid. Arterial blood pH should be used to monitor the amount of bicarbonate administered, since it is possible to overshoot the normal pH range and produce a significant alkalosis. I have been using this procedure for over 15 years with no adverse effects. Procedures to increase the alveolar ventilation are instituted as rapidly as possible once the diagnosis is made. When the initial pH is below