Cardiovascular changes induced by cold water immersion during hyperbaric hyperoxic exposure.

The present study was designed to assess the cardiac changes induced by cold water immersion compared with dry conditions during a prolonged hyperbaric and hyperoxic exposure (ambient pressure between 1.6 and 3 ATA and PiO(2) between 1.2 and 2.8 ATA). Ten healthy volunteers were studied during a 6 h compression in a hyperbaric chamber with immersion up to the neck in cold water while wearing wet suits. Results were compared with measurements obtained in dry conditions. Echocardiography and Doppler examinations were performed after 15 min and 5 h. Stroke volume, left atrial and left ventricular (LV) diameters remained unchanged during immersion, whereas they significantly fell during the dry session. As an index of LV contractility, percentage fractional shortening remained unchanged, in contrast to a decrease during dry experiment. Heart rate (HR) significantly decreased after 5 h, although it had not changed during the dry session. The changes in the total arterial compliance were similar during the immersed and dry sessions, with a significant decrease after 5 h. In immersed and dry conditions, cardiac output was unchanged after 15 min but decreased by almost 20% after 5 h. This decrease was related to a decrease in HR during immersion and to a decrease in stroke volume in dry conditions. The hydrostatic pressure exerted by water immersion on the systemic vessels could explain these differences. Indeed, the redistribution of blood volume towards the compliant thoracic bed may conceal a part of hypovolaemia that developed in the course of the session

GENESE D'UN APPAREILLAGE BIOMEDICAL POUR LA PREVENTION DES HYPOTHERMIES INDUITES PAR LES PERFUSIONS MASSIVES EN OXYOLOGIE

BESANCON-BU Médecine pharmacie (250562102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Aqua jogging-induced pulmonary oedema.

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La cryothérapie gazeuse hyperbare (conception, validation, observations cliniques d'une nouvelle technique de cryothérapie)

BESANCON-BU Médecine pharmacie (250562102) / SudocSudocFranceF

To the editor: the definition of diastolic suction is most often based on intraventricular pressure and volume changes.

International audienc

Hyperbaric gaseous cryotherapy: effects on skin temperature and systemic vasoconstriction.

International audienceOBJECTIVE: To compare skin-surface cooling caused by the application of an ice bag (15min) and the projection of carbon dioxide microcristals (2min) under high pressure (75 bar) and low temperature (-78 degrees C), a modality called hyperbaric gaseous cryotherapy. DESIGN: Randomized controlled trial with repeated measure. SETTING: Laboratory experiment. PARTICIPANTS: Twelve healthy male subjects (mean +/- standard deviation, 22.9+/-1.8y). INTERVENTIONS: Ice bag and hyperbaric gaseous cryotherapy were randomly applied on the skin of the nondominant hand. MAIN OUTCOME MEASURE: Skin temperature of the cooled (dorsal and palmar sides) and contralateral (dorsal side) hands were continuously measured with thermistor surface-contact probes before, during, and after (30min) cooling. RESULTS: Hyperbaric gaseous cryotherapy projection induced a large decrease (P<.05) of the dorsal skin temperature of the cooled hand (from 32.5 degrees +/-0.5 degrees C to 7.3 degrees +/-0.8 degrees C) and a significant decrease of the skin temperature of the palmar side and of the contralateral hand. The skin temperature of the dorsal side of the cooled hand was decreased with an ice bag (from 32.5 degrees +/-0.6 degrees C to 13.9 degrees +/-0.7 degrees C, P<.05). However, the lowest temperature was significantly higher than during hyperbaric gaseous cryotherapy, and no significant changes in the other skin temperatures were observed. Rewarming was equal after the 2 modalities, highlighting a more rapid increase of the skin temperature after hyperbaric gaseous cryotherapy. CONCLUSIONS: Hyperbaric gaseous cryotherapy projection decreased the skin temperature of the cooled and contralateral hand, suggesting a systemic skin vasoconstriction response. On the other hand, the vascular responses triggered by ice pack cooling appeared limited and localized to the cooled area

[Physiological assessment of a gaseous cryotherapy device: thermal effects and changes in cardiovascular autonomic control]

International audiencePURPOSE: The aim of the study was to assess thermal effects and cardiovascular autonomic control with application of a gaseous cryotherapy device to the hand. MATERIAL AND METHODS: Before, during and after cooling of the left hand, we continuously evaluated cutaneous temperature of the right and left hands, as well as heart rate (HR) and arterial blood pressure (BP) and their neurovegetatif control (HR and BP variability) in 8 healthy subjects. Comparison of cooling caused by projection of CO(2) microcrystals (2 min) under high pressure (75 bar) and low temperature (-78 degrees C) to that with application of a latex ice pack (15 min). Assessment of whether cooling triggered any changes in cardiovascular autonomic control, especially as compared with responses by the hand cold-pressure test (2 min). RESULTS: CO(2) projection in the left hand induced a steep decrease (-26 degrees C) in temperature followed by a rapid increase and a cutaneous vasoconstriction of the right hand, with significant increases in BP and cardiac parasympathetic activity. Cardiovascular responses were similar to those with application of the hand cold-pressure test. Application of an ice pack decreased cutaneous temperature to a lesser extent (-19 degrees C) and more slowly, without changing BP or indices of HR and BP variability. CONCLUSION: CO(2) projection caused "thermal shock" and triggered a systemic cutaneous vasoconstriction response, with activation of indices of both ortho- and parasympathetic activity, as with the hand cold-pressure test. Vascular responses during ice pack cooling appeared solely localised to the cooled area, without any significant change in autonomic cardiovascular control

Effects of the cold pressor test on cardiac autonomic control in normal subjects.

International audienceThe cold pressor test (CPT) triggers in healthy subjects a vascular sympathetic activation and an increase in blood pressure. The heart rate (HR) response to this test is less well defined, with a high inter-individual variability. We used traditional spectral analysis together with the non-linear detrended fluctuation analysis to study the autonomic control of HR during a 3-min CPT. 39 healthy young subjects (23.7+/-3.2 years, height 180.4+/-4.7 cm and weight 73.3+/-6.4 kg) were divided into two groups according to their HR responses to CPT. Twenty subjects have a sustained increase in HR throughout the test with reciprocal autonomic interaction, i.e. increase in sympathetic activity and decrease vagal outflow. In the 19 remainders, HR decreased after an initial increase, with indication of involvement of both sympathetic and vagal outflow. Baseline evaluation of the subjects revealed no difference between the two groups. Nevertheless, a higher sympathetic activity at the skin level during CPT was present in the group with decreased HR. Further studies are needed to explain why healthy subjects react differently to the CPT and if this has potential clinical implications

Régulation neurovégétative des fonctions cardiovasculaires (étude lors de l'exercice, de l'entraînement, du surentraînement et lors de l'immersion)

Nous avons étudié les ajustements des systèmes cardiovasculaire et neurovégétatif à l'exercice (avec/sans entraînement) et à l'immersion (thermoneutralité /froid, courte/longue durée ). Ils peuvent être bénéfiques : l'immersion à la thermoneutralité minimise l'activité sympathique et les ajustements fonctionnels ; l'entraînement accroît la part d'activité parasympathique à destinée cardiaque (repos couché, orthostatisme, exercice). Ils peuvent aussi être délétères pour des sujets aux fonctions amoindries : la déshydratation suivant l'immersion gêne les réglages vasomoteurs ; une forte activité sympathique suit la mauvaise gestion des charges d'entraînement ; le froid augmente les résistances vasculaires et active simultanément les deux branches efférentes du système neurovégétatif. Les réponses décrites ici chez l 'homme sain permettent de réfléchir aux conditions d'exposition de sujets malades, pour qui la réadaptation par l'exercice, immergé ou non, est de plus en plus souvent envisagée.We studied the effects of exercise (with/without exercise training) and water immersion (thermoneutral/cold, short/long duration) on cardiovascular and autonomic nervous system requirements. These responses appeared beneficial in some conditions : thermoneutral water immersion minimizes sympathetic activity and the control requirements; exercise training shifts autonomic control towards p-arasympathetic predominance (supine rest, orthostatism, exercise). Other responses appeared potentially deleterious for subjects with limited functions: post immersion dehydration hampers vasomotor adjustments ; a wrong management of training loads triggers a high sympathetic activation ; cold exposure increases peripheral resistances and activates the two efferent limbs of the autonomic nervous system. These results in healthy subjects provide landmarks for procedure proposaIs to patients in whom rehabilitation through exercise, submerged or not, are now frequently considered.BESANCON-BU Médecine pharmacie (250562102) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Intermittent versus constant aerobic exercise: effects on arterial stiffness.

International audienceAerobic exercises (of sufficient duration and intensity) decreases arterial stiffness. However, the direct relationship between the type of aerobic exercise (i.e. constant versus interval) and the alteration in arterial stiffness has been poorly explored. We evaluated the hemodynamic responses of 11 healthy males (22.5 +/- 0.7 years, height 177.7 +/- 1.1 cm, body mass 70.5 +/- 2.4 kg) following acute constant (CE) and intermittent cycling exercise (IE). Exercise duration and intensity (mean heart rate) were matched during both exercises (142.9 +/- 2.4 bpm for CE and 144.2 +/- 2.4 bpm for IE). Heart rate (HR) and cardiac output (CO) were measured throughout the whole session, while blood pressure and pulse wave velocity (PWV) were measured during pre exercise and 30 min recovery. Arterial stiffness and cardiac autonomic control were assessed through PWV and heart rate variability, respectively. After IE, lower limb arterial stiffness was significantly and steadily decreased compared to pre exercise value (from 8.6 +/- 0.1 to m s(-1) to 7.6 +/- 0.3 to m s(-1) at 30 min) and was lower than after CE (8.2 +/- 0.3 m s(-1) at 30 min, which did not significantly change compared to pre exercise: 8.7 +/- 0.2 m s(-1)). We hypothesized that the higher HR and lower arterial stiffness after IE were likely due to variations in peripheral vascular changes during the exercise which may trigger the release of endothelial or metabolic vasoactive factors. These data appear to show that IE may result in a greater stimulus for vascular adaptations when compared to CE