[Spontaneous ventilation in anesthesia. Introduction].
The "ventilatory requirement" can be measured in every conscious subject. But it cannot be appreciated under general anaesthesia. General anaesthesia produce a difference between the amount of spontaneous breathing of the subject and his "ventilatory requirement". A metabolic debt can appear without ventilatory compensation. So spontaneous breathing is never indicated during general anaesthesia. It can be tolerated in some technical situations when controlled breathing is impossible.
D000768:Anesthesia, General; D006801:Humans; D012119:Respiration; D012121:Respiration, Artificial
II. La ventilation spontanée en anesthésie Introduction.