314 THE RESPIRATION 



Table II 



The Relation of the Vital Capacity of the Lungs to the Clinical Condition in 



Patients with Heart Disease* 



(Peabody and Went/worth.) 



'Certain cases were tested several times and, owing to changes in the vital capacity they appear 

 in more than one group. In the "mortality" column they are included only in the lowest group into 

 which they fell. "Symptoms of decompensation" indicate dyspnea while at rest in bed or on very 

 slight exertion. Under "working" are included only those actually at work, and able to continue. 

 Many other patients in Group II were able to work, but they are not included as they were still in 

 the hospital. 



Table II shows that there is a remarkably close relationship between 

 the clinical condition of cardiac patients, particularly as regards the 

 tendency to dyspnea, and the vital capacity of the lungs. Peabody and 

 Wentworth believe that the determination of the vital capacity affords 

 a clinical test as to the functional condition of the heart, since compen- 

 sated patients who do not complain of dyspnea on exertion have a nor- 

 mal vital capacity. Patients with more serious disease in whom dyspnea 

 is a prominent symptom, have a low vital capacity; and the decrease in 

 vital capacity runs parallel with the clinical condition. As a patient 

 improves, his vital capacity tends to rise ; as he becomes worse, it tends 

 to fall. In other diseases in which mechanical conditions interfere with 

 the movements of the lungs, the tendency to dyspnea corresponds closely 

 to the decrease in the vital capacity. The cause of the decrease in the 

 vital capacity of the lung in cardiac decompensation is difficult to ex- 

 plain satisfactorily. It may be the limitation in the movements of the 

 lungs produced by engorgement of the pulmonary vessels, by the weak- 

 ness of the intercostal muscles, the rigidity of the bony thorax, 

 emphysema, or accumulation of fluid in the pleural cavities. 



In cardiac disease the air in the lungs at the end of a normal expiration 

 is usually increased. This is similar to the condition which attends exer- 

 cise, and is probably ;i physiological adaptation 1<> give optimum aeration 

 to the blood, as explained above. 



