Effect of water temperature on bradycardia during nonapneic facial immersion in man

Cardiovascular responses elicited by different simulated diving manoeuvres

It has been documented that placing an ice-bag on the forehead causes similar cardiac and vascular responses as face immersion. There has been disagreement concerning the contribution of separate cold stimulation on the face and breathholding in the diving response. This study set out to unravel the extent to which these two factors contribute individually to the observed cardiovascular changes during the combined manoeuvre. It further aimed to reveal whether peripheral vascular responses to these stimuli are different in forearm and calf. We observed a significant rapid increase in the RR-interval, which was maintained until the end of the 25-s observation period and a homogeneous vasoconstriction in forearm and calf, despite minor changes in arterial blood pressure, during breathholding, placing the icebag on the forehead and the combined stimuli. Cardiac and peripheral vascular responses to the combined manoeuvre did not differ significantly from the responses elicited by the two stimuli separately. This test is another example that illustrates the heterogeneous cardiovascular response involving both parasympathetic and sympathetic activation. Moreover, since the icebag on the forehead test is technically easy to perform and does not require the active co-operation of the patient, it may be a valid method to replace a full face immersion test accompanied by breathholding.

Power spectrum analysis of heart rate fluctuations and respiratory movements associated with cooling the human skin

A length of respiratory movement and instantaneous heart rate was divided into 32 segments to adopt computerized power spectrum analysis. An array of frequency spectrum across all the segments was then constructed to demonstrate sequential changes in the respiratory rhythm (0.4 Hz), low (less than 0.1 Hz) and high (0.2-0.4 Hz)-frequency components of heart rate fluctuations associated with lowering the skin temperature. A significant increase in the power for the low and high frequency components of heart rate fluctuations accompanying bradycardia occurred by cooling the face to 0 and 10 degrees C, while cooling the foot to 0 degrees C yielded a significant increase and decrease in the power for the former and latter component, respectively, without change in heart rate. The spectral power for respiratory movements was not altered by these stimuli. The maximal change in the power for low- and high-frequency components as well as in the heart rate during cooling the face and foot to 0 degrees C was found to correlate negatively with the relative resting magnitude of the respective parameter in the pre-stimulus period. Similar relationship existed only with the power for low-frequency component of heart rate fluctuations when lowering the temperature of foot to 10 degrees C. The power spectrum array employed in this study thus enabled us to estimate the effectiveness of skin cooling on the three hemodynamic parameters.

Limitations of facial immersion as a test of parasympathetic activity in man

1. The heart rate response to immersion of the face in water, as an isolated manoeuvre or in combination with apnoea, was studied in eight normal volunteers to establish the conditions under which it could be used as a standardized, simple, non-invasive and reproducible test of parasympathetic activity. 2. The following procedures were evaluated: (a) 10 s apnoea in air at different lung volumes; (b) facial immersion in water for 2 min at various temperatures (5, 15 and 25 degrees C), with respiration maintained through a closed circuit; (c) combination of immersion and apnoea at different lung volumes. Three volunteers were re-evaluated after pharmacological blockade with atropine sulphate (0.04 mg/kg body weight). 3. The results showed that: (a) apnoea in air triggered lung volume-dependent heart rate responses; (b) facial immersion in water induced transient bradycardia which was maximum between 20 and 30 s of immersion; (c) there was no appreciable difference in the bradycardia evoked by immersion at different temperatures; (d) the combination of immersion and apnoea caused heterogeneous heart rate responses with no potentiation of bradycardia in relation to each manoeuvre as performed separately; (e) atropine did not reduce the magnitude of bradycardia induced by immersion in two of the subjects studied. 4. The variability of responses observed in the present study was probably due to the multiple receptors and afferent pathways that are simultaneously excited during these manoeuvres. As a consequence, the autonomic efferent response will depend on the unpredictable net effect of interaction of these mechanisms. This is a limiting factor for the standardization of this test as a simple and reproducible method for the assessment of parasympathetic activity. 5. Furthermore, the results obtained under pharmacological blockade indicate that the vagal efferent mechanism is not the only factor responsible for the bradycardia caused by facial immersion without apnoea.

Supraventricular tachycardia in infants: use of the "diving reflex"

The effectiveness of the "diving reflex" in treating paroxysmal supraventricular tachycardia (PSVT) in 10 infants aged under 6 months is demonstrated. No rhythm disturbances were encountered during the maneuver, even in patients receiving digitalis. The recommended water temperature is 5 degrees C and the total time of facial immersion, between 6 and 7 seconds. The diving reflex might be considered the first therapeutic approach in infants under 6 months old with PSVT.

The use of the diving reflex to terminate supraventricular tachycardia in a 2-week-old infant

The use of the diving reflex to terminate a case of paroxysmal supraventricular tachycardia (PST) is described in a 2-week-old infant who presented in severe congestive heart failure with supraventricular tachycardia at a rate of 300. The infant's face was placed in a basin of ice water at 5 degrees C. for 5 seconds with manual occlusion of the infant's nostrils to prevent aspiration. The PST converted to a sinus rhythm of 120 within 3 seconds of facial immersion. The physiology of the diving reflex is reviewed and the uses and hazards of this reflex in terminating attacks of PST in infants is discussed.

Conversion of paroxysmal atrial tachycardia by facial immersion in ice water

Based on the concept of the classic diving reflex, which produced bradycardia, a technique for treating uncomplicated, but symptomatic, paroxysmal atrial tachycardia was developed. This technique consists of facial immersion for 15 to 30 seconds in water at 10 C (50 F). Of ten patients 9 (90%) achieved rapid conversion without complications. This technique may be especially useful for those patients resistant to more conventional methods of inducing conversion of paroxysmal atrial tachycardia.