Depth of SCUBA Diving Affects Cardiac Autonomic Nervous System.

The present study investigated the influence of SCUBA dives with compressed air at depths of 10 and 20 m on ECG-derived HRV parameters in apparently healthy individuals. We hypothesized that cardiac sympathetic activity (measured by HRV parameters) adapts proportionally to diving depth, and that both time- and frequency-domain parameters are sensitive enough to track changes in cardiac ANS function during diving activities and subsequently during the recovery period. Eleven healthy middle-aged recreational divers (nine men and two women, age 43 ± 8, all nonsmokers) volunteered to participate in the present study.

Effects of Oxygen Prebreathing on Bubble Formation, Flow-Mediated Dilatation, and Psychomotor Performance during Trimix Dives.

This research was performed to examine the effects of air and oxygen prebreathing on bubble formation, flow-mediated dilatation, and psychomotor performance after scuba dives. Twelve scuba divers performed two dives using a gas mixture of oxygen, nitrogen, and helium (trimix). In a randomized protocol, they breathed air or oxygen 30 min before the trimix dives.

The Influence of Oral Cannabidiol on 24-h Ambulatory Blood Pressure and Arterial Stiffness in Untreated Hypertension: A Double-Blind, Placebo-Controlled, Cross-Over Pilot Study.

Introduction: Studies reveal that cannabidiol may acutely reduce blood pressure and arterial stiffness in normotensive humans; however, it remains unknown if this holds true in patients with untreated hypertension. We aimed to extend these findings to examine the influence of the administration of cannabidiol on 24-h ambulatory blood pressure and arterial stiffness in hypertensive individuals.

Methods: Sixteen volunteers (eight females) with untreated hypertension (elevated blood pressure, stage 1, stage 2) were given oral cannabidiol (150 mg every 8 h) or placebo for 24 h in a randomised, placebo-controlled, double-blind, cross-over study.

Larger splenic emptying correlate with slower EPOC kinetics in healthy men and women during supine cycling.

Purpose: The present study investigated whether larger splenic emptying augments faster excess post-exercise O consumption (EPOC) following aerobic exercise cessation.

Methods: Fifteen healthy participants (age 24 ± 4, 47% women) completed 3 laboratory visits at least 48-h apart. After obtaining medical clearance and familiarizing themselves with the test, they performed a ramp-incremental test in the supine position until task failure.

No differences in splenic emptying during on-transient supine cycling between aerobically trained and untrained participants.

Purpose: The role of splenic emptying in O transport during aerobic exercise still remains a matter of debate. Our study compared the differences in spleen volume changes between aerobically trained and untrained individuals during step-transition supine cycling exercise at moderate-intensity. We also examined the relationship between spleen volume changes, erythrocyte release, and O uptake parameters.

Spleen emptying does not correlate with faster oxygen kinetics during a step-transition supine cycling.

This manuscript quantified spleen volume changes and examined the relationship between those changes and oxygen uptake kinetics during supine cycling. Ten volunteers (age = 22 ± 3), completed 3 step transitions from 20 W to their power output at 90% gas exchange threshold. Ultrasonic measurements of the spleen were performed each minute.

Acute flywheel exercise does not impair the brachial artery vasodilation in healthy men of varying aerobic fitness.

Background: The cardiovascular response to variable load exercise on a flywheel ergometer is still unknown.

Objective: This study examined the effects of flywheel exercise on cardiovascular response and brachial artery vasodilation capacity in healthy, active men.

Methods: In this cross-sectional study, nineteen men (20-57 years old) completed three laboratory visits, including a ramp exercise test to determine their maximal oxygen uptake JOURNAL/blpmo/04.

Influence of oxygen enriched gases during decompression on bubble formation and endothelial function in self-contained underwater breathing apparatus diving: a randomized controlled study.

Aim: To assess the effect of air, gas mixture composed of 50% nitrogen and 50% oxygen (nitrox 50), or gas mixture composed of 1% nitrogen and 99% oxygen (nitrox 99) on bubble formation and vascular/endothelial function during decompression after self-contained underwater breathing apparatus diving.

Methods: This randomized controlled study, conducted in 2014, involved ten divers. Each diver performed three dives in a randomized protocol using three gases: air, nitrox 50, or nitrox 99 during ascent.

2D speckle tracking echocardiography of the right ventricle free wall in SCUBA divers after single open sea dive.

The presence of circulating gas bubbles and their influence on pulmonary and right heart hemodynamics was reported after uncomplicated self-contained underwater breathing apparatus (SCUBA) dive(s). Improvements in cardiac imaging have recently focused great attention on the right ventricle (RV). The aim of our study was to evaluate possible effects of a single air SCUBA dive on RV function using 2D speckle tracking echocardiography in healthy divers after single open sea dive to 18 meters of seawater, followed by bottom stay of 47 minutes with a direct ascent to the surface.

Diving and pulmonary physiology: Surfactant binding protein, lung fluid and cardiopulmonary test changes in professional divers.

Alteration of breathing pattern ranging from an increase of respiratory rate to overt hyperventilation during and after SCUBA diving is frequently reported and is associated with intrathoracic fluid overload. This study was undertaken to assess breathing efficiency after diving and the association with damage of alveolar cells. Ventilation efficiency (VE/VCO) during maximal cardiopulmonary exercise test (CPET) before and 2h after a standard protocol dive has been analyzed in twelve professional males divers (39.

Blood pooling in extrathoracic veins after glossopharyngeal insufflation.

Purpose: Trained breath-hold divers hyperinflate their lungs by glossopharyngeal insufflation (GPI) to prolong submersion time and withstand lung collapse at depths. Pulmonary hyperinflation leads to profound hemodynamic changes.

Methods: Thirteen divers performed preparatory breath-holds followed by apnea with GPI.

Effect of repetitive SCUBA diving on humoral markers of endothelial and central nervous system integrity.

During SCUBA diving decompression, there is a significant gas bubble production in systemic veins, with rather frequent bubble crossover to arterial side even in asymptomatic divers. The aim of the current study was to investigate potential changes in humoral markers of endothelial and brain damage (endothelin-1, neuron-specific enolase and S-100β) after repetitive SCUBA diving with concomitant assessment of venous gas bubble production and subsequent arterialization. Sixteen male divers performed four open-water no-decompression dives to 18 msw (meters of sea water) lasting 49 min in consecutive days during which they performed moderate-level exercise.

The effects of low-dose epinephrine infusion on spleen size, central and hepatic circulation and circulating platelets.

In several conditions associated with adrenergic stimulation, an increase in peripheral count of larger platelets has been observed, but the mechanism remained elusive. Larger platelets have greater prothrombotic potential and increase the risk of acute thrombotic events. The human spleen retains one-third of total body platelets, with mean volume (MPV) about 20% greater than that of circulating platelets.

Effects of successive air and nitrox dives on human vascular function.

SCUBA diving is regularly associated with asymptomatic changes in cardiac, pulmonary and vascular function. The aim of this study was to evaluate the changes in vascular/endothelial function following SCUBA diving and to assess the potential difference between two breathing gases: air and nitrox 36 (36% oxygen and 64% nitrogen). Ten divers performed two 3-day diving series (no-decompression dive to 18 m with 47 min bottom time with air and nitrox, respectively), with 2 weeks pause in between.

A no-decompression air dive and ultrasound lung comets.

Introduction: Increased accumulation of extravascular lung water after repetitive deep trimix dives was recently reported. This effect was evident 40 min post-dive, but in subsequent studies most signs of this lung congestion were not evident 2-3 h post-dive, indicating no major negative effects on respiratory gas exchange following deep dives. Whether this response is unique for trimix dives or also occurs in more frequent air dives is presently unknown.

Venous and arterial bubbles at rest after no-decompression air dives.

Purpose: During SCUBA diving, breathing at increased pressure leads to a greater tissue gas uptake. During ascent, tissues may become supersaturated, and the gas is released in the form of bubbles that typically occur on the venous side of circulation. These venous gas emboli (VGE) are usually eliminated as they pass through the lungs, although their occasional presence in systemic circulation (arterialization) has been reported and it was assumed to be the main cause of the decompression sickness.

High incidence of venous and arterial gas emboli at rest after trimix diving without protocol violations.

SCUBA diving is associated with generation of gas emboli due to gas release from the supersaturated tissues during decompression. Gas emboli arise mostly on the venous side of circulation, and they are usually eliminated as they pass through the lung vessels. Arterialization of venous gas emboli (VGE) is seldom reported, and it is potentially related to neurological damage and development of decompression sickness.

Successive deep dives impair endothelial function and enhance oxidative stress in man.

The aim of this study was to assess the effects of successive deep dives on endothelial function of large conduit arteries and plasma pro-oxidant and antioxidant activity. Seven experienced divers performed six dives in six consecutive days using a compressed mixture of oxygen, helium and nitrogen (trimix) with diving depths ranging from 55 to 80 m. Before and after first, third and sixth dive, venous gas emboli formation and brachial artery function (flow-mediated dilation, FMD) was assessed by ultrasound.

Glossopharyngeal insufflation induces cardioinhibitory syncope in apnea divers.

Apnea divers increase intrathoracic pressure voluntarily by taking a deep breath followed by glossopharyngeal insufflation. Because apnea divers sometimes experience hypotension and syncope during the maneuver, they may serve as a model to study the mechanisms of syncope. We recorded changes in hemodynamics and sympathetic vasomotor tone with microneurography during breath holding with glossopharyngeal insufflation.

Ultrasonic evidence of acute interstitial lung edema after SCUBA diving is resolved within 2-3h.

Recently, an increase in extravascular lung water (EVLW) accumulation with diminished left ventricular contractility within 60 min after SCUBA diving was reported. We have observed previously that diving was associated with reduced diffusing lung capacity for carbon monoxide (DLCO) and arterial oxygen pressure for up to 60-80 min postdive. Here we investigated whether increased EVLW persists 2-3h after successive deep dives in a group of seven male divers.

Assessment of extravascular lung water and cardiac function in trimix SCUBA diving.

Unlabelled: An increasing number of recreational self-contained underwater breathing apparatus (SCUBA) divers use trimix of oxygen, helium, and nitrogen for dives deeper than 60 m of sea water. Although it was seldom linked to the development of pulmonary edema, whether SCUBA diving affects the extravascular lung water (EVLW) accumulation is largely unexplored.

Methods: Seven divers performed six dives on consecutive days using compressed gas mixture of oxygen, helium, and nitrogen (trimix), with diving depths ranging from 55 to 80 m.

Effects of successive air and trimix dives on human cardiovascular function.

Introduction: The use of trimix (a mixture of oxygen, helium, and nitrogen) has significantly increased among the diver population. However, data indicating how trimix dives at most common depths affect the cardiovascular function are sparse. The purpose of this study was to investigate the cardiovascular effects of trimix dives and compare them with air dives and to determine whether the repetition of dives in successive days affects their extent.

Effects of indomethacin on cerebrovascular response to hypercapnea and hypocapnea in breath-hold diving and obstructive sleep apnea.

We tested whether breath hold divers (BHD) and obstructive sleep apnea (OSA) subjects had similar middle cerebral artery velocity (MCAV) responses to hypercapnea and hypocapnea. We analyzed changes in MCAV (cm/s) in response to hypocapnea and hyperoxic hypercapnea during placebo or after 90 min of oral indomethacin (100 mg) in BHD (N=7) and OSA (N=7). During control hypercapnea MCAV increased for 54.

Cardiovascular regulation during apnea in elite divers.

Involuntary apnea during sleep elicits sustained arterial hypertension through sympathetic activation; however, little is known about voluntary apnea, particularly in elite athletes. Their physiological adjustments are largely unknown. We measured blood pressure, heart rate, hemoglobin oxygen saturation, muscle sympathetic nerve activity, and vascular resistance before and during maximal end-inspiratory breath holds in 20 elite divers and in 15 matched control subjects.