Breath Holding After Exercise

¹ From the Applied Physiology Branch, Directorate of Medical Research, Chemical Warfare Laboratories, Army Chemical Center, Maryland

Breath holding time was measured after exercise at five grades of work in a group of 12 men. An average of 1.4 seconds elapsed between the signal, which was given without warning, and the cessation of inhalation. During this time the volume inhaled varied with the phase of the breathing cycle in which the signal was given; it was greatest when the signal was given in the quarter cycles immediately before and after the beginning of inspiration. Since breath holding time was unaffected by the phasing of the signal, it is thought the volume of the lung was adjusted to enable the hold to begin with a full lung (full in the sense of a full tidal volume characteristic of the previous grade of work). The mean breath holding time decreased from 25.8 seconds after the lowest grade of work to 5.8 seconds after the highest. It was proposed that the stimulus to breathe at the end of the hold was the same after all grades of work. The stimulus was evaluated in terms of a rate of accumulation of a chemical stimulating condition proportional to the previous respiratory minute volume, multiplied by the length of the hold and divided by the estimated volume of the lungs during the hold. Calculated in this way the value assigned to the stimulus varied from 1.0 to 1.3 among the grades of previous work. In half the trials alternating gasps and holds were continued after the initial hold for a total of 30 seconds. The succeeding breath holding times were essentially of the same length as the first. The volume of the succeeding gasps varied only slightly with the previous grade of work.