Alex Rizzato

Hyperbaric oxygen therapy modulates serum OPG/RANKL in femoral head necrosis patients

Abstract Hyperbaric oxygen therapy (HBOT) has beneficial effects on avascular necrosis of femoral head (ANFH), but its mechanism of action is still unclear. We investigated if HBOT upregulates serum osteoprotegerin (OPG) and/or inhibits osteoclast activation. 23 patients with unilateral ANFH at stage I, II and III consented to the study: the patients received standard HBOT. Serum OPG levels were obtained at the beginning of HBOT (T0), after 15 sessions (T1), 30 sessions (T2), after a 30-day break (T3), and after 60 sessions (T4). Magnetic resonance imaging (MRI) was obtained at T0 and about one year from the end of HBO treatments. Lesion size was compared between pre- and post-HBOT. 19 patients completed the study. HBOT reduced pain symptoms in all patients. HBOT significantly reduced lesion size in all stage I and II patients and in 2 of 11 stage III patients. HBOT increased serum OPG levels but receptor activator of nuclear factor kappa-B ligand (RANKL) levels did not change.

Environmental Physiology and Diving Medicine

Man’s experience and exploration of the underwater environment has been recorded from ancient times and today encompasses large sections of the population for sport enjoyment, recreational and commercial purpose, as well as military strategic goals. Knowledge, respect and maintenance of the underwater world is an essential development for our future and the knowledge acquired over the last few dozen years will change rapidly in the near future with plans to establish secure habitats with specific long-term goals of exploration, maintenance and survival. This summary will illustrate briefly the physiological changes induced by immersion, swimming, breath-hold diving and exploring while using special equipment in the water. Cardiac, circulatory and pulmonary vascular adaptation and the pathophysiology of novel syndromes have been demonstrated, which will allow selection of individual characteristics in order to succeed in various environments. Training and treatment for these new microenvironments will be suggested with description of successful pioneers in this field. This is a summary of the physiology and the present status of pathology and therapy for the field.

An overview of protective strategies against ischemia/reperfusion injury: The role of hyperbaric oxygen preconditioning

Ischemia/reperfusion (I/R) injury, such as myocardial infarction, stroke, and peripheral vascular disease, has been recognized as the most frequent causes of devastating disorders and death currently. Protective effect of various preconditioning stimuli, including hyperbaric oxygen (HBO), has been proposed in the management of I/R.

Spirometry and oxidative stress after rebreather diving in warm water

Introduction Hyperbaric oxygen (HBO₂) therapy and use of enriched air can result in oxidative injury affecting the brain, lungs and eyes. HBO₂ exposure during diving can lead to a decrease in respiratory parameters. However, the possible effects of acute exposure to oxygen-enriched diving on subsequent spirometric performance and oxidative state in humans have not been recently described recently. We aim to investigate possible effects of acute (i) hyperbaric and (ii) hyperbaric hyperoxic exposure using scuba or closed-circuit rebreather (CCR) on subsequent spirometry and to assess the role of oxidative state after hyperoxic diving. Methods Spirometry and urine samples were obtained from six well-trained divers (males, mean ± SD, age: 43.33 ± 9.16 years; weight: 79.00 ± 4.90 kg; height: 1.77 ± 0.07 meters) before (CTRL) and after a dive breathing air, and after a dive using CCR (PO₂ 1.4). In the crossover design (two dives separated by six hours) each subject performed a 20-minute session of light underwater exercise at a depth of 15 meters in warm water (31-32°C). We measured urinary 8-isoprostane and 8-OH-2-deoxyguanosine evaluating lipid and DNA oxidative damages. Results Different breathing conditions (air vs. CCR) did not significantly affect spirometry. A significant increase of 8-OH-dG (1.85 ± 0.66 vs. 4.35 ± 2.12; P ⟨ 0.05) and 8-isoprostane (1.35 ± 0.20 vs. 2.59 ± 0.61; P ⟨ 0.05) levels after CCR dive with respect to the CTRL was observed. Subjects did not have any ill effects during diving. Conclusions Subjects using CCR showed elevated oxidative stress, but this did not correlate with a reduction in pulmonary function.

Effects of the Ketogenic diet in overweight divers breathing Enriched Air Nitrox

Central Nervous System Oxygen Toxicity (CNS-OT) is one of the most harmful effects of Enriched Air Nitrox (EAN) diving. Protective factors of the Ketogenic Diet (KD) are antioxidant activity, the prevention of mitochondrial damage and anti-inflammatory mechanisms. We aimed to investigate if a short-term KD may reduce oxidative stress and inflammation during an hyperoxic dive. Samples from six overweight divers (mean ± SD, age: 55.2 ± 4.96 years; BMI: 26.7 ± 0.86 kg/m2) were obtained a) before and after a dive breathing Enriched Air Nitrox and performing 20-minute mild underwater exercise, b) after a dive (same conditions) performed after 7 days of KD. We measured urinary 8-isoprostane and 8-OH-2-deoxyguanosine and plasmatic IL-1β, IL-6 and TNF-α levels. The KD was successful in causing weight loss (3.20 ± 1.31 Kgs, p < 0.01) and in limiting lipid peroxidation (3.63 ± 1.16 vs. 1.11 ± 0.22; p < 0.01) and inflammatory response (IL-1β = 105.7 ± 25.52 vs. 57.03 ± 16.32, p < 0.05; IL-6 = 28.91 ± 4.351 vs. 14.08 ± 1.74, p < 0.001; TNF-α = 78.01 ± 7.69 vs. 64.68 ± 14.56, p < 0.05). A short-term KD seems to be effective in weight loss, in decreasing inflammation and protective towards lipid peroxidation during hyperoxic diving.

Hyperbaric oxygen therapy ameliorates osteonecrosis in patients by modulating inflammation and oxidative stress

Abstract Early stages of avascular necrosis of the femoral head (AVNFH) can be conservatively treated with hyperbaric oxygen therapy (HBOT). This study investigated how HBOT modulates inflammatory markers and reactive oxygen species (ROS) in patients with AVNFH. Twenty-three male patients were treated with two cycles of HBOT, 30 sessions each with a 30 days break between cycles. Each session consisted of 90 minutes of 100% inspired oxygen at 2.5 absolute atmospheres of pressure. Plasma levels of tumor necrosis factor alfa (TNF-α), interleukin 6 (IL-6), interleukin 1 beta (IL-1β) and ROS production were measured before treatment (T0), after 15 and 30 HBOT sessions (T1 and T2), after the 30-day break (T3), and after 60 sessions (T4). Results showed a significant reduction in TNF-α and IL-6 plasma levels over time. This decrease in inflammatory markers mirrored observed reductions in bone marrow edema and reductions in patient self-reported pain.

Arterial blood gas analysis in breath-hold divers at depth

The present study aimed to evaluate the partial pressure of arterial blood gases in breath-hold divers performing a submersion at 40 m. Eight breath-hold divers were enrolled for the trials held at “Y-40 THE DEEP JOY” pool (Montegrotto Terme, Padova, Italy). Prior to submersion, an arterial cannula in the radial artery of the non-dominant limb was positioned. All divers performed a sled-assisted breath-hold dive to 40 m. Three blood samplings occurred: at 10 min prior to submersion, at 40 m depth, and within 2 min after diver’s surfacing and after resuming normal ventilation. Blood samples were analyzed immediately on site. Six subjects completed the experiment, without diving-related problems. The theoretically predicted hyperoxia at the bottom was observed in 4 divers out of 6, while the other 2 experienced a reduction in the partial pressure of oxygen (paO2) at the bottom. There were no significant increases in arterial partial pressure of carbon dioxide (paCO2) at the end of descent in 4 of 6 divers, while in 2 divers paCO2 decreased. Arterial mean pH and mean bicarbonate (HCO3−) levels exhibited minor changes. There was a statistically significant increase in mean arterial lactate level after the exercise. Ours was the first attempt to verify real changes in blood gases at a depth of 40 m during a breath-hold descent in free-divers. We demonstrated that, at depth, relative hypoxemia can occur, presumably caused by lung compression. Also, hypercapnia exists at depth, to a lesser degree than would be expected from calculations, presumably because of pre-dive hyperventilation and carbon dioxide distribution in blood and tissues.