Physiological and conventional breath-hold breaking points.

logical and conventional breath-hold breaking points. J. Appl. Physiol. 37(3) : 291-296. 1974.-The course of breath-hold (BH) can be characterized by a) voluntary inhibition of respiratory muscular activity, b) onset and maintained involuntary ventilatory activity (IVA) with glottis closed, and c) voluntary opening of glottis. While type c has been widely studied, the present study focused on type b. The intraesophageal pressure (IEP), BH time and oxygen-demand relationship, and factors responsible for the onset of IVA were studied during BH with air and BH with oxygen at rest and during steady-state exercise at 167 kgm*min? IVA generates periodic subatmospheric pressure in the thoracic cavity, while at the onset of BH the IEP is above ambient. The effect of this periodic subatmospheric intrathoracic pressure on the cardio-vascular functions is discussed. The relationship between 90, (ml. s-l) and BH time (T, s) can be described by T = a (1 /Voz) +