Carl Moyer

Costal and Abdominal Respiratory Movements in Relation to Nervous Control of Breathing

Changes in body circumference associated with respiratory movements were simultaneously recorded in the dog at 6 different levels—3 costal and 3 abdominal. (Fig. 1.) Continuous registration of respiratory movements with this method showed variations in type from time to time in the same individual. Some of these changes were spontaneous; others were elicited by deliberate introduction of new variables. Analysis of measurements on 31 female and 73 male dogs failed to show any relation between sex and mode of breathing. Comparing the magnitude of increased costal circumference with the magnitude of increased abdominal circumference 34.3% of 106 dogs were found to breathe more with the chest than with the abdomen. Using our new method of comparing costal and abdominal accommodation of air by grossly correcting for the greater costal circumference and greater length of chest 79% were found to be costal breathers. The mean ratio of costal to abdominal accommodation for all of the dogs studied was 2.15 indicating a decided predominance of costal breathing in the dog. A shifting from a more costal or more abdominal type towards the other respective type was frequently preceded by a momentary and sporadic stretching of the extremities. At times, periodic fluctuations in respiratory movements occurred, limited to either costal or abdominal levels. These findings suggested that periodicity may be a localized phenomenon dependent on chemical sensitivity in the cord. Great irregularities in the magnitude of respiratory excursions occurred mostly from changing inspiratory circumference. Under these conditions the expiratory circumference may remain surprisingly uniform. In some experiments the expiratory circumferences changed as well. At times the expiratory circumference of the chest showed gross fluctuations while those of the abdomen remained perfectly constant. The reverse also occurred.