Saturday, June 30
Enrico Camporesi, MD
"Hyperbaric Oxygen Therapy for Aseptic Necrosis of the Femoral Head andof the Femoral Condyli"
Osteonecrosis of the knee (ONK) is a form of aseptic necrosis resulting from ischemia to subchondral bone tissue. Typically, common surgical treatments are invasive and palliative or time-limited. Hyperbaric oxygen (HBO2) therapy may provide a non-invasive alternative by improving oxygenation and reperfusion of ischemic areas, both for distal femoral condyli, as recently described, or for a similar malady of the femoral head, previously published.
Gerardo Bosco, MD
Pre-conditioning (PC) has been described as the hyperbaric oxygen (HBO2) experience before a critical event, with the aim to prevent a specific clinical condition, and its development as a valuable complement both in diving medicine (Bosco, 2010) as well as prior to ischemic or inflammatory situations. PC is a preventive treatment that triggers endogenous cascades, which can protect from stress-activated and stress-reactive responses. A possible mechanism of HBO-PC mediating beneficial effects has been described as attenuation of the production of proinflammatory cytokines in response to an inflammatory stimulus such as surgery and modulation of the immune response. HBO-PC protocols are performed at 2.0–2.5 atmospheres absolute (ATA), and usually only applied for one or a few days. The physical adaptations in response to alterations in atmospheric oxygen appear to extend not only to survival, but also a preconditioned state.
Similar to ischemic and stress preconditioning, many different paradigms have been used to demonstrate that either rapid or delayed tolerance is affected by the HBO2 therapy. Irrespective of the cause of injury, inflammatory cytokines released after the primary event trigger leukocyte activation and free radical release, causing secondary damage and extension of injury. Thus, modulating inflammatory molecules has the potential benefit of limiting leukocyte-mediated extension of injury. Many studies demonstrated a protective mechanism of HBO-PC in the injured brain, heart, or liver. Previous data by Yang and colleagues on animals demonstrated that HBO2 inhibits TNF-α production during intestinal, brain and muscle ischemia-reperfusion and it has a beneficial effect, mediated by decreased production of IL-6, IL-1β, dopamine and lactate (Bosco, 2007; Yang, 2001;2006;2010). Studies on animals showed that HBO-PC can protect the brain from ischemia-reperfusion injury and that Sirt1 is a potential molecular target for therapeutic approaches (Ding, 2017). In man, HBO-PC induces endogenous cardioprotection subsequent to ischemic reperfusion injury (Allen, 2014).
Additionally, clinical HBO-PC showed effects before surgery. A single preoperative hyperbaric oxygen treatment on the day before surgery may reduce the complication rate in pancreatic resection (Bosco, 2014). In liver surgery, studies demonstrated to increase the number of new cells and the density of microcirculation in the regenerating liver after HBO-PC (Theodoraki, 2011). Furthermore, hyperbaric oxygen preconditioning improves postoperative dysfunctions by reducing oxidant stress and inflammation (Gao, 2017). A recent experimental paper has identified an important mechanism involved in triggering the beneficial effect of HBO-PC, as the intracellular induction of heme-oxygenase-1 in hepatic IR injury. Moreover, in dive medicine HBO-PC reduced bubble formation and platelets activation; HBO-PC might enhance lymphocyte antioxidant activity and reduce reactive oxygen species levels. Pre-breathing oxygen in water may also preserve calcium homeostasis, suggesting a protective role in the physiological lymphocyte cell functions (Bosco, 2010; Morabito, 2011).
Whether the various preconditioning protocols contribute to the different results should be investigated in further studies and applied to diverse surgical procedures, especially major surgeries leading to postoperative ICU admission. Therefore, HBO-PC is an encouraging and feasible therapeutic strategy for protecting organs from the subsequent lethal stimulus.
Shai Efrati, MD
Clinical studies published in recent years present convincing evidences that hyperbaric oxygen (HBO2) therapy can be the coveted neurotherapeutic method for brain repair of neurological incidents like traumatic brain injury and stroke. This new understanding leads to a paradigm change in the way that we refer to chronic brain injuries; from now these should be thought of like other non-healing wounds in other parts of the body.
Gerardo Bosco, MD
"Adaptive mechanisms in breath-hold divers"
The human body faces extreme physiological challenges while immersed with voluntary breath-holding. Breath-hold diving is potentially associated to extreme environmental factors such as increased hydrostatic pressure, hypoxia, hypercapnia, hypothermia and strenuous exercise. Physiological adaptations can depend among the time of breath suspension and the depth of diving. While descending chest squeeze and blood redistribution occur. Indeed, blood as being an incompressible fluid from peripheral circulation is shifted to the chest. The intrathoracic blood volume increases. Moreover, face immersion results in induced bradycardia, due to the diving reflex. Conversely, breath-holding at rest, out of water, induces non-significant changes in heart rate. Breath-hold swimming, even on the surface, instead causes pronounced bradycardia. During deep diving a higher O2 consumption and a fall in alveolar and blood O2 content was observed. Consequently, alveolar CO2 pressure increases due to chest compression while descending.
Peter Lindholm, MD
"Pulmonary pathophysiology in deep breath-hold diving"
Deep breath-hold diving may expose the lungs to the limits of known human physiology. We will discuss barotrauma of descent with pulmonary edema, glossopharyngeal hyperinsufflation and arterial gas embolism.
Alessandro Marroni, MD
"Breaking news on breath-hold diving research"