Possible causes of prolonged apnœa / by W.D.M. Paton.

  • William Paton
Date:
[1958]
Catalogue details

Licence: In copyright

Credit: Possible causes of prolonged apnœa / by W.D.M. Paton. Source: Wellcome Collection.

    9/30 page 257
    continue. One wonders if there is not a field for investigation here. It might be worthwhile to study the duration of apnoea which is pro¬ duced by varying degrees of overventilation in patients anaesthetised with standard procedures. If one knew what the usual range of varia¬ tion was it would help considerably in assessing the odds that a given patient was apnoeic from this particular cause; and it would help in laying down a standard test period during which ventilation could be suspended in order to test whether overventilation was involved. AFFERENT STIMULATION It is possible to suspend respiration temporarily by various forms of sensory stimulation. The apnoea of getting into a cold bath is one example. Excitation of the vagus nerve or sensory nerves in animals can produce the same effect, and there are chemical compounds, active on chemoreceptors, which can amongst other effects depress the respiration temporarily. One would have thought these observa¬ tions too far removed from clinical practice to have much relevance, were it not for such reports as that a patient, following an operation, would fail to breathe properly despite all usual measures until the cuff on an indwelling tracheal tube was deflated9. The significance of this is certainly arguable. It may be that the act of deflation of the cuff constituted a stimulus to the trachea. Alternatively, it may be that the continued inflation of the cuff produced a sustained excitation of an unusual kind to vagal afferent fibres in the wall of the trachea, and that its removal allowed normal respiratory rhythm to reoccur. At all events, it raises the possibility that forms of afferent sensory stimula¬ tion, which might not necessarily have to reach consciousness, might suppress breathing or simply disorganise the normal, rhythmically synchronised, respiratory activity. One wonders in this connection what effect those sensory stimuli have during the immediate post¬ operative period, which later constitute post-operative pain. The fact that sensation is not reaching consciousness does not necessarily mean that it is devoid of physiological effect in the body. AFFERENT PARALYSIS At the risk of appearing to wish to ride two horses simultaneously, I must also raise the converse point to the one just mentioned. There is good evidence that normal respiration is often driven by central nerv¬ ous influences other than those arriving from chemoreceptor excita¬ tion. For instance, the hyperpnoea seen in muscular exercise starts sooner, and may be greater, than would be accounted for by blood gas exchanges. Reflexes from muscles and joints have been proposed to account for these results. This implies that interference with the
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