David Peppi

Breathing pattern during CO2 inhalation obtained from motion of the chest and abdomen

A method is described for obtaining tidal volume from movements of the chest and abdomen utilizing electromagnetic sensors. Tidal volume obtained from these sensors was linearly related to tidal volume simultaneously obtained with a spirometer within an error of 14 per cent. With this method, the ventilation-tidal volume relationship was studied during CO2 inhalation. This relationship was curvilinear and closely approximated a parabola: Vt = a Ve + b VE2, where Vt = tidal volume and Ve = minute ventilation. The numerical value of b was always negative so that at high ventilations the tidal volume tended to level off and increases in ventilation occurred primarily as a result of increases in frequency. The value of tidal volume and the ratio of tidal volume to vital capacity at which leveling off of the tidal volume occurred was variable among individuals and often differed in the same individual on different occasions. Added resistive and elastic loads altered the Ve — Vt curves in the direction of minimal respiratory force or minimal respiratory work. The use of a mouthpiece, directional valve and noseclip did not alter the Ve — Vt relationship. There was no sex difference in the proportions of the total tidal volume contributed by chest and abdomen motion and these proportions did not change significantly with increasing ventilation in the majority of subjects.

The effect of progressive exercise on the equilibrium rebreathing cardiac output method

The equilibrium CO2 rebreathing method has been used in the study of exercise cardiac output (Q) in health and disease, but the requirement for a steady state has usually limited its application to step function exercise. This limits testing to only a few levels of exertion in a laboratory session. We have devised a treadmill test where the grade is flat at the beginning and rises continuously at 1%.min-1 after stable measurements are obtained during level walking. The walking speed is determined by the subjects comfort and tolerance for fast walking. In series I seven normal subjects were studied with this protocol, and an automated system was employed for estimation of Q and oxygen uptake (VO2). For comparison of steady state and progressive tests, an interpolation method was devised which furnished a value of Q (progressive) that could exist at the value of VO2 obtained during the steady state. The average difference in Q so estimated between the steady state and the unsteady state was 0.3 l.min-1, SD = 1.7. This difference was less than the difference between averages of duplicate values of Q obtained during the steady state (1.11.min-1, SD = 16), and the difference between the two differences was not significant. Based on 51 determinations of Q and VO2 in eight normal subjects the unsteady state procedure furnished an average value of the relation slope of delta Q/delta VO2(-1) of 4.8 l.l-1. We conclude that the equilibrium CO2 method can be used to depict the Q, VO2 relationship over the range of VO2 at which rebreathing is tolerable.

Significance of relative rib cage and abdomen motion in patients with chronic obstructive pulmonary disease

Changes in intrapleural pressure (ΔPpl) and abdomen pressure (ΔPab) were related to changes in the anterior-posterior diameter of the rib cage (ΔRC) and abdomen (ΔAb) in 17 patients with chronic obstructive pulmonary disease (COPD).ΔPab-ΔPpl equalsΔPdi, the change in transdiaphragmatic pressure. Measurements were made during quiet inspiration in the semierect position.ΔAb/(ΔAb+ΔRC) was used as a measure of relative abdomen motion, andΔPab/ΔPdi was used as a measure of the relative contribution of descent of the diaphragm to the breathing process. Patients with COPD developed greater ΔPdi than normal subjects. This increasedΔPdi was the result of relatively more intercostal and accessory muscle activity rather than increased diaphragm motion. Despite this, patients with COPD showed the same relative abdomen motion as did normal subjects. Observation of relative chest and abdomen motion in patients with COPD is a poor guide to relative use of the rib cage muscles and diaphragm.