Effect of hypnotic suggestions on the respiratory response to transient CO 2 breathing in man

Abstract

The transient ventilatory response to two breaths of 20% CO 2 was measured repeatedly in three normal human subjects. Responses were recorded under two conditions and compared: 1. 1. The subject normally conscious and uninformed about the precise nature of the experiment. 2. 2. The subject hypnotised and suggestions made to render the subject unaware of the sensation of breathing and of the experimental surroundings. The response (Δv̇ emax/ΔP CO 2 max) varied widely within and between subjects under both conditions. With subjects pooled, the mean response when hypnotised (O.62 litre·mm Hg −1·min −1) was greater than the mean response when normally conscious (O.41. litre·mm Hg −1·min −1), (O.05 < P < O.1, 2-sided t-test). This finding suggests that the transient ventilatory response to 20% CO 2 is not due solely to psychological factors associated with the taste and awareness of CO; breathing and is consistent with an arterial chemoreflex response which is partly inhibited by higher centres in the normal conscious state.