ABSTRACT
AIM: Reductions in arterial oxygen partial pressure activate the peripheral chemoreceptors which increase ventilation, and, after cessation of breathing, reduce heart rate. We tested the hypothesis that facial cooling facilitates these peripheral chemoreflex mechanisms. METHODS: Chemoreflex control was assessed by the ventilatory response to hypoxia (10% O2 in N2) and the bradycardic response to voluntary end-expiratory apnoeas of maximal duration in 12 young, healthy subjects. We recorded minute ventilation, haemoglobin O2 saturation, RR interval (the time between two R waves of the QRS complex) and the standard deviation of the RR interval (SDNN), a marker of cardiac vagal activity throughout the study. Measurements were performed with the subject's face exposed to air flow at 23 and 4 degrees C. RESULTS: Cold air decreased facial temperature by 11 degrees C (P < 0.0001) but did not affect minute ventilation during normoxia. However, facial cooling increased the ventilatory response to hypoxia (P < 0.05). The RR interval increased by 31 +/- 8% of the mean RR preceding the apnoea during the hypoxic apnoeas in the presence of cold air, compared to 17 +/- 5% of the mean RR preceding the apnoea in the absence of facial cooling (P < 0.05). This increase occurred despite identical apnoea durations and reductions in oxygen saturation. Finally, facial cooling increased SDNN during normoxia and hypoxia, as well as during the apnoeas performed in hypoxic conditions (all P < 0.05). CONCLUSION: The larger ventilatory response to hypoxia suggests that facial cooling facilitates peripheral chemoreflex mechanisms in normal humans. Moreover, simultaneous diving reflex and peripheral chemoreflex activation enhances cardiac vagal activation, and favours further bradycardia upon cessation of breathing.
Subject(s)
Cold Temperature , Face/innervation , Reflex/physiology , Adult , Apnea/physiopathology , Autonomic Nervous System/physiopathology , Blood Pressure/physiology , Body Temperature Regulation/physiology , Bradycardia/physiopathology , Chemoreceptor Cells/physiology , Heart Rate/physiology , Humans , Hypoxia/physiopathology , Male , Oxygen/blood , Oxygen Consumption/physiology , Partial Pressure , Skin Temperature/physiology , Young AdultABSTRACT
If in the final analysis the value of the projected treatment can only be considered relative to results obtained by therapy which it has motivated, would it not be possible as implied to assure from the very beginning its effects? The author's research based on statistical and clinical analysis of 233 files drawn up by the Policlinique psychiatrique de Lausanne, between 1967 and 1975, allows an affirmative reply. And if on the one hand this work goes as far as to relativise or even to negate the capacities of the therapist (a therapist considered mediocre obtaining almost identical results to one who is not seen as such), and on the other to show that all the inconstant elements studied are no longer likely to be mastered by the medical prerogatives alone, the latter is not put into doubt but simply becomes better adjusted to prevailing socio-cultural conditions.
