Expression of Mitochondrial Respiratory Chain Complexes in the Vaginal Wall in Postmenopausal Women with Pelvic Organ Prolapse.

BACKGROUND/AIMS: Pelvic organ prolapse (POP) is a common disease affecting adult women. It is a result of the vaginal wall disorder as well as damage of the supportive structures contributing to the integrity of the pelvic floor. Mitochondrial disorders may have an important role in the vaginal wall degeneration leading to POP. The goal of this research is to examine if POP is associated with an altered expression of mitochondrial respiratory chain complexes. METHODS: Samples of vaginal tissue were collected from 16 postmenopausal women: 10 had POP and 6 had other forms of benign gynecological disease. Using western blot, samples were analyzed to assess the expression of mitochondrial proteins including citrate synthase (CS), individual complexes of the mitochondrial respiratory chain and alpha smooth muscle actin (SMA). RESULTS: A significantly reduced expression of SMA and complex II in vaginal tissue of women with POP was found, compared to the control group (p < 0.05), with a tendency for a reduced expression of CS (p = 0.06) and other complexes in the POP group. CONCLUSIONS: Our results indicate that there is a decreased quantity of the smooth muscle and a decreased expression of mitochondrial markers in the vaginal wall of women with prolapse suggesting their possible role in the pathogenesis of POP.

Effects of scuba diving on vascular repair mechanisms.

A single air dive causes transient endothelial dysfunction. Endothelial progenitor cells (EPCs) and circulating angiogenic cells (CAC) contribute synergistically to endothelial repair. In this study (1) the acute effects of diving on EPC numbers and CAC migration and (2) the influence of the gas mixture (air/nitrox-36) was investigated. Ten divers performed two dives to 18 meters on Day (D) 1 and D3, using air. After 15 days, dives were repeated with nitrox-36. Blood sampling took place before and immediately after diving. Circulating EPCs were quantified by flow cytometry, CAC migration of culture was assessed on D7. When diving on air, a trend for reduced EPC numbers is observed post-dive, which is persistent on D1 and D3. CAC migration tends to improve acutely following diving. These effects are more pronounced with nitrox-36 dives. Diving acutely affects EPC numbers and CAC function, and to a larger extent when diving with nitrox-36. The diving-induced oxidative stress may influence recruitment or survival of EPC. The functional improvement of CAC could be a compensatory mechanism to maintain endothelial homeostasis.

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-100ß) 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. Before and after dives 1 and 4 blood was drawn, and bubble production and potential arterialization were echocardiographically evaluated. In addition, a control dive to 5 msw was performed with same duration, water temperature and exercise load. SCUBA diving to 18 msw caused significant bubble production with arterializations in six divers after dive 1 and in four divers after dive 4. Blood levels of endothelin-1 and neuron-specific enolase did not change after diving, but levels of S-100ß were significantly elevated after both dives to 18 msw and a control dive. Creatine kinase activity following a control dive was also significantly increased. Although serum S-100ß levels were increased after diving, concomitant increase of creatine kinase during control, almost bubble-free, dive suggests the extracranial release of S-100ß, most likely from skeletal muscles. Therefore, despite the significant bubble production and sporadic arterialization after open-water dives to 18 msw, the current study found no signs of damage to neurons or the blood-brain barrier.

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. Arterial/endothelial function was assessed using SphygmoCor and flow-mediated dilation measurements, and concentration of nitrite before and after diving was determined in venous blood. Production of nitrogen bubbles post-dive was assessed by ultrasonic determination of venous gas bubble grade. Significantly higher bubbling was found after all air dives as compared to nitrox dives. Pulse wave velocity increased slightly (~6%), significantly after both air and nitrox diving, indicating an increase in arterial stiffness. However, augmentation index became significantly more negative after diving indicating smaller wave reflection. There was a trend for post-dive reduction of FMD after air dives; however, only nitrox diving significantly reduced FMD. No significant differences in blood nitrite before and after the dives were found. We found that nitrox diving affects systemic/vascular function more profoundly than air diving by reducing FMD response, most likely due to higher oxygen load. Both air and nitrox dives increased arterial stiffness, but decreased wave reflection suggesting a decrease in peripheral resistance due to exercise during diving. These effects of nitrox and air diving were not followed by changes in plasma nitrite.

Association Between Personal Activity Intelligence and Mortality: Population-Based China Kadoorie Biobank Study.

OBJECTIVE: To prospectively investigate the association between personal activity intelligence (PAI) - a novel metabolic metric which translates heart rate during physical activity into a simple weekly score - and mortality in relatively healthy participants in China whose levels and patterns of physical activity in addition to other lifestyle factors are different from those in high-income countries. PATIENTS AND METHODS: From the population-based China Kadoorie Biobank study, 443,792 healthy adults were recruited between June 2004 and July 2008. Participant's weekly PAI score was estimated and divided into four groups (PAI scores of 0, ≤50, 51-99, or ≥100). Using Cox proportional hazard analyses, we calculated adjusted hazard ratios (AHRs) for cardiovascular disease (CVD) and all-cause mortality related to PAI scores. RESULTS: During a median follow-up of 8.2 (interquartile range, 7.3 to 9.1) years, there were 21,901 deaths, including 9466 CVD deaths. Compared with the inactive group (0 PAI score), a baseline weekly PAI score greater than or equal to 100 was associated with a lower risk of CVD mortality, an AHR of 0.87 (95% CI, 0.81 to 0.94) in men, and an AHR of 0.84 (95% CI, 0.78 to 0.92) in women, after adjusting for multiple confounders. Participants with a weekly PAI score greater than or equal to 100 also had a lower risk of all-cause mortality (AHR, 0.93; 95% CI, 0.89 to 0.97 in men, and AHR, 0.93; 95%, 0.88 to 0.98 in women). Moreover, this subgroup gained 2.7 (95% CI, 2.4 to 3.0) years of life, compared with the inactive cohort. CONCLUSION: Among relatively healthy Chinese adults, the PAI metric was inversely associated with CVD and all-cause mortality, highlighting the generalizability of the score in different races, ethnicities, and socioeconomic strata.

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. METHODS: A single no-decompression field dive to 33 m with 20 min bottom time was performed by 12 male divers. Multiple ultrasound lung comets (ULC), bubble grade (BG), and single-breath lung diffusing capacity (DLCO) measurements were made before and up to 120 min after the dive. RESULTS: Median BG was rather high with maximal values observed at 40 min post-dive [median 4 (4-4)]. Arterialization of bubbles from the venous side was observed only in one diver lasting up to 60 min post-dive. Despite high BG, no DCS symptoms were noted. DLCO and ULC were unchanged after the dive at any time point (DLCO(corr) was 33.6 +/- 1.9 ml x min(-1) mmHg(-1) pre-dive, 32.7 +/- 3.8 ml x min(-1) x mmHg(-1) at 60 min post-dive, and 33.2 +/- 5.3 ml x min(-1) x mmHg(-1) at 120 min post-dive; ULC count was 4.1 +/- 1.9 pre-dive, 4.9 +/- 3.3 at 20 min post-dive, and 3.3 +/- 1.9 at 60 min post-dive. DISCUSSION: These preliminary findings show no evidence of increased accumulation of extravascular lung water in male divers after a single no-decompression air dive at the limits of accepted Norwegian diving tables.

Differences in production of reactive oxygen species and mitochondrial uncoupling as events in the preconditioning signaling cascade between desflurane and sevoflurane.

BACKGROUND: Signal transduction cascade of anesthetic-induced preconditioning has been extensively studied, yet many aspects of it remain unsolved. Here, we investigated the roles of reactive oxygen species (ROS) and mitochondrial uncoupling in cardiomyocyte preconditioning by two modern volatile anesthetics: desflurane and sevoflurane. METHODS: Adult rat ventricular cardiomyocytes were isolated enzymatically. The preconditioning potency of desflurane and sevoflurane was assessed in cell survival experiments by evaluating myocyte protection from the oxidative stress-induced cell death. ROS production and flavoprotein fluorescence, an indicator of flavoprotein oxidation and mitochondrial uncoupling, were monitored in real time by confocal microscopy. The functional aspect of enhanced ROS generation by the anesthetics was assessed in cell survival and confocal experiments using the ROS scavenger Trolox. RESULTS: Preconditioning of cardiomyocytes with desflurane or sevoflurane significantly decreased oxidative stress-induced cell death. That effect coincided with increased ROS production and increased flavoprotein oxidation detected during acute myocyte exposure to the anesthetics. Desflurane induced significantly greater ROS production and flavoprotein oxidation than sevoflurane. ROS scavenging with Trolox abrogated preconditioning potency of anesthetics and attenuated flavoprotein oxidation. CONCLUSION: Preconditioning with desflurane or sevoflurane protects isolated rat cardiomyocytes from oxidative stress-induced cell death. Scavenging of ROS abolishes the preconditioning effect of both anesthetics and attenuates anesthetic-induced mitochondrial uncoupling, suggesting a crucial role for ROS in anesthetic-induced preconditioning and implying that ROS act upstream of mitochondrial uncoupling. Desflurane exhibits greater effect on stimulation of ROS production and mitochondrial uncoupling than sevoflurane.

Disturbed Fatty Acid Oxidation, Endoplasmic Reticulum Stress, and Apoptosis in Left Ventricle of Patients With Type 2 Diabetes.

Chronic heart failure is a common complication in patients with type 2 diabetes mellitus (T2DM). T2DM is associated with disturbed metabolism of fat, which can result in excessive accumulation of lipids in cardiac muscle. In the current study, we assessed mitochondrial oxidation of carbohydrates and fatty acids, lipid accumulation, endoplasmic reticulum (ER) stress, and apoptosis in diabetic left ventricle. Left ventricular myocardium from 37 patients (a group of patients with diabetes and a group of patients without diabetes [ejection fraction >50%]) undergoing coronary artery bypass graft surgery was obtained by subepicardial needle biopsy. The group with diabetes had a significantly decreased rate of mitochondrial respiration fueled by palmitoyl-carnitine that correlated with blood glucose dysregulation, while there was no difference in oxidation of pyruvate. Diabetic myocardium also had significantly decreased activity of hydroxyacyl-CoA dehydrogenase (HADHA) and accumulated more lipid droplets and ceramide. Also, markers of ER stress response (GRP78 and CHOP) and apoptosis (cleaved caspase-3) were elevated in diabetic myocardium. These results show that, even in the absence of contractile failure, diabetic heart exhibits a decreased mitochondrial capacity for ß-oxidation, increased accumulation of intracellular lipids, ER stress, and greater degree of apoptosis. Lower efficiency of mitochondrial fatty acid oxidation may represent a potential target in combating negative effects of diabetes on the heart.

Exercise Reveals Proline Dehydrogenase as a Potential Target in Heart Failure.

The benefits of physical activity in cardiovascular diseases have long been appreciated. However, the molecular mechanisms that trigger and sustain the cardiac benefits of exercise are poorly understood, and it is anticipated that unveiling these mechanisms will identify novel therapeutic targets. In search of these mechanisms we took advantage of unbiased RNA-sequencing (RNA-seq) technology to discover cardiac gene targets whose expression is disrupted in heart failure (HF) and rescued by exercise in a rat model. Upon exhaustive validation in a separate rat cohort (qPCR) and human datasets, we shortlisted 16 targets for a cell-based screening, aiming to evaluate whether targeted disruption of these genes with silencing RNA would affect the abundance of a CVD biomarker (BNP, B-type natriuretic peptide) in human cardiomyocytes. Overall, these experiments showed that Proline Dehydrogenase (PRODH) expression is reduced in human failing hearts, rescued by exercise in a rat model of HF, and its targeted knockdown increases BNP expression in human cardiomyocytes. On the other hand, overexpression of PRODH increases the abundance of metabolism-related gene transcripts, and PRODH appears to be crucial to sustain normal mitochondrial function and maintenance of ATP levels in human cardiomyocytes in a hypoxic environment, as well as for redox homeostasis in both normoxic and hypoxic conditions. Altogether our findings show that PRODH is a novel molecular target of exercise in failing hearts and highlight its role in cardiomyocyte physiology, thereby proposing PRODH as a potential experimental target for gene therapy in HF.

Age-related attenuation of isoflurane preconditioning in human atrial cardiomyocytes: roles for mitochondrial respiration and sarcolemmal adenosine triphosphate-sensitive potassium channel activity.

BACKGROUND: Clinical trials suggest that anesthetic-induced preconditioning (APC) produces cardioprotection in humans, but the mechanisms of APC and significance of aging for APC in humans are not well understood. Here, the impact of age on the role of two major effectors of APC, mitochondria and sarcolemmal adenosine triphosphate-sensitive potassium (sarcKATP) channels, in preconditioning of the human atrial myocardium were investigated. METHODS: Right atrial appendages were obtained from adult patients undergoing cardiac surgery and assigned to mid-aged (MA) and old-aged (OA) groups. APC was induced by isoflurane in isolated myocardium and isolated cardiomyocytes. Mitochondrial oxygen consumption measurements, myocyte survival testing, and patch clamp techniques were used to investigate mitochondrial respiratory function and sarcKATP channel activity. RESULTS: After in vitro APC with isoflurane, the respiratory function of isolated mitochondria was better preserved after hypoxia-reoxygenation stress in MA than in OA. In isolated intact myocytes, APC significantly decreased oxidative stress-induced cell death in MA but not in OA, and isoflurane protection from cell death was attenuated by the sarcKATP channel inhibitor HMR-1098. Further, the properties of single sarcKATP channels were similar in MA and OA, and isoflurane sensitivity of pinacidil-activated whole cell KATP current was no different between MA and OA myocytes. CONCLUSION: Anesthetic-induced preconditioning with isoflurane decreases stress-induced cell death and preserves mitochondrial respiratory function to a greater degree in MA than in OA myocytes; however, sarcKATP channel activity is not differentially affected by isoflurane. Therefore, effectiveness of APC in humans may decrease with advancing age partly because of altered mitochondrial function of myocardial cells.

Mitochondrial energy metabolism in baby hamster kidney (BHK-21/C13) cells treated with karnozin extra® / Metabolismo energético mitocondrial en células de riñón de hámster bebé (BHK-21 / C13) tratadas con karnozin extra®

SUMMARY: Carnosine is known as a natural dipeptide, which inhibits the proliferation of tumor cells throughout its action on mitochondrial respiration and cell glycolysis. However, not much is known about its effects on the metabolism of healthy cells. We explored the effects of Karnozin EXTRA® capsule with different concentrations of L-carnosine, on the cell viability and the expressions of intermediate filament vimentin (VIM) and superoxide dismutase (SOD2) in normal fibroblasts BHK-21/C13. Furthermore, we investigated its action on the energy production of these cells. Cell viability was quantified by the MTT assay. The Clark oxygen electrode (Oxygraph, Hansatech Instruments, England) was used to measure the "intact cell respiration rate", state 3 of ADP-stimulated oxidation, maximum oxidation capacity and the activities of complexes I, II and IV. Results showed that Karnozin EXTRA® capsule in concentrations of 2 and 5 mM of L-carnosine did not induce toxic effects and morphological changes in treated cells. Our data revealed a dose-dependent immunofluorescent signal amplification of VIM and SOD2 in the BHK-21/C13 cell line. This supplement substantially increased the recorded mitochondrial respiration rates in the examined cell line. Due to the stimulation of mitochondrial energy production in normal fibroblasts, our results suggested that Karnozin EXTRA® is a potentially protective dietary supplement in the prevention of diseases with altered mitochondrial function.

RESUMEN: La carnosina se conoce como dipéptido natural, que inhibe la proliferación de células tumorales a través de su acción sobre la respiración mitocondrial y la glucólisis celular. Sin embargo, no se sabe mucho de sus efectos sobre el metabolismo de las células sanas. Exploramos los efectos de la cápsula Karnozin EXTRA® con diferentes concentraciones de L-carnosina, sobre la viabilidad celular y las expresiones de vimentina de filamento intermedio (VIM) y superóxido dismutasa (SOD2) en fibroblastos normales BHK-21 / C13. Además, estudiamos su acción sobre la producción de energía de estas células. La viabilidad celular se cuantificó mediante el ensayo MTT. Se utilizó el electrodo de oxígeno Clark (Oxygraph, Hansatech Instruments, Inglaterra) para medir la "tasa de respiración de células intactas", el estado 3 de oxidación estimulada por ADP, la capacidad máxima de oxidación y las actividades de los complejos I, II y IV. Los resultados mostraron que la cápsula de Karnozin EXTRA® en concentraciones de 2 y 5 mM de L- carnosina no indujo efectos tóxicos ni cambios morfológicos en las células tratadas. Nuestros datos revelaron una amplificación de señal inmunofluorescente dependiente de la dosis de VIM y SOD2 en la línea celular BHK-21 / C13. Este suplemento aumentó sustancialmente las tasas de respiración mitocondrial registradas en la línea celular examinada. Debido a la estimulación de la producción de energía mitocondrial en fibroblastos normales, nuestros resultados sugirieron que Karnozin EXTRA® es un suplemento dietético potencialmente protector en la prevención de enfermedades con función mitocondrial alterada.

The impact of consecutive freshwater trimix dives at altitude on human cardiovascular function.

Self-contained underwater breathing apparatus (SCUBA) diving is regularly associated with numerous asymptomatic changes in cardiovascular function. Freshwater SCUBA diving presents unique challenges compared with open sea diving related to differences in water density and the potential for dive locations at altitude. The aim of this study was to evaluate the impact of freshwater trimix diving at altitude on human cardiovascular function. Ten divers performed two dives in consecutive days at 294 m altitude with the surface interval of 24 h. Both dives were at a depth of 45 m with total dive time 29 and 26 min for the first and second dive, respectively. Assessment of venous gas embolization, hydration status, cardiac function and arterial stiffness was performed. Production of venous gas emboli was low, and there were no significant differences between the dives. After the first dive, diastolic blood pressure was significantly reduced, which persisted up to 24 h. Left ventricular stroke volume decreased, and heart rate increased after both dives. Pulse wave velocity was unchanged following the dives. However, the central and peripheral augmentation index became more negative after both dives, indicating reduced wave reflection. Ejection duration and round trip travel time were prolonged 24 h after the first dive, suggesting longer-lasting suppression of cardiac and endothelial function. This study shows that freshwater trimix dives with conservative profiles and low venous gas bubble loads can result in multiple asymptomatic acute cardiovascular changes some of which were present up to 24 h after dive.

Role of KATP Channels in Beneficial Effects of Exercise in Ischemic Heart Failure.

PURPOSE: Exercise training reduces pathological remodeling and improves cardiac function in ischemic heart failure; however, causal mechanisms underlying the cardiac benefits of exercise are poorly understood. Because opening of adenosine triphosphate (ATP)-sensitive K ⁺(KATP) channels protects the heart during myocardial stress, we hypothesized that such a mechanism is responsible for some of the cardiac benefits induced by exercise in postinfarction chronic heart failure (CHF). METHODS: Left ventricular myocytes were isolated from three groups of rats: Sham, CHF Tr (4 wk after myocardial infarction, rats underwent 8 wk of aerobic interval training 5 d·wk⁻¹) and CHF Sed (rats sedentary for 12 wk after infarction). Cardiomyocyte survival after oxidative stress exposure (200 µM H2O2) and calcium handling (cells loaded with Fura-2 AM and electrically paced at 1 Hz) were assessed in the presence of KATP channel inhibitor glibenclamide. Expression of KATP subunits (SUR2A and Kir6.2) was evaluated using immunoblotting. RESULTS: Exercise improved cardiac function in CHF Tr animals. Cardiomyocytes from CHF Sed rats were more susceptible to oxidative stress-induced cell death than CHF Tr and Sham cardiomyocytes, with glibenclamide completely abolishing the protective effect of exercise. Glibenclamide did not affect cardiomyocyte survival in Sham or CHF Sed rats. In addition, exercise increased the systolic Ca²âº transient amplitude and improved diastolic Ca²âº removal in CHF Tr cardiomyocytes (compared with CHF Sed); both were significantly attenuated by glibenclamide. Exercise resulted in increased expression of KATP channel subunits in CHF Tr hearts, with more pronounced and significant effect on SUR2A. CONCLUSIONS: Our data suggest that KATP channel upregulation induced by chronic exercise likely mediates some of exercise-induced beneficial effects on cardiac function in postischemic heart failure.

Aerobic interval training attenuates remodelling and mitochondrial dysfunction in the post-infarction failing rat heart.

AIMS: Following a large myocardial infarction (MI), remaining viable muscle often undergoes pathological remodelling and progresses towards chronic heart failure. Mitochondria may also be affected by this process and, due to their functional importance, likely contribute to the progression of the disease. Aerobic interval training (AIT) has been shown effective in diminishing pathological myocardial transformation, but the effects of AIT on mitochondrial function in hearts undergoing remodelling are not known. METHODS AND RESULTS: Adult female Sprague-Dawley rats were randomized to either 8 weeks of aerobic interval treadmill running (5 days/week), which started 4 weeks after left coronary artery ligation (MI-Trained), or a sedentary group (MI-Sedentary). Echocardiography was performed before and after the 8-week period, at which point the left ventricles (LVs) were also harvested. Twelve weeks after surgery, MI-Sedentary rats had significantly lower LV fractional shortening compared with MI-Trained rats. Complex I-dependent respiration assessed in isolated LV mitochondria was decreased by ∼37% in MI-Sedentary and 17% in MI-Trained animals (group differences P < 0.05), compared with sham-operated animals. This was paralleled with diminished ATP production and increased degree of protein oxidation in MI-Sedentary rats. The enzymatic activity of complex I was also decreased to a greater extent in MI-Sedentary than in MI-Trained animals, with no evidence of its reduced expression. When complex II substrate was used, no differences among the three groups were observed. CONCLUSION: Exercise reduces LV contractile deterioration in post-infarction heart failure and alleviates the extent of mitochondrial dysfunction, which is paralleled with preserved complex I activity.

Determinants of arterial gas embolism after scuba diving.

Scuba diving is associated with breathing gas at increased pressure, which often leads to tissue gas supersaturation during ascent and the formation of venous gas emboli (VGE). VGE crossover to systemic arteries (arterialization), mostly through the patent foramen ovale, has been implicated in various diving-related pathologies. Since recent research has shown that arterializations frequently occur in the absence of cardiac septal defects, our aim was to investigate the mechanisms responsible for these events. Divers who tested negative for patent foramen ovale were subjected to laboratory testing where agitated saline contrast bubbles were injected in the cubital vein at rest and exercise. The individual propensity for transpulmonary bubble passage was evaluated echocardiographically. The same subjects performed a standard air dive followed by an echosonographic assessment of VGE generation (graded on a scale of 0-5) and distribution. Twenty-three of thirty-four subjects allowed the transpulmonary passage of saline contrast bubbles in the laboratory at rest or after a mild/moderate exercise, and nine of them arterialized after a field dive. All subjects with postdive arterialization had bubble loads reaching or exceeding grade 4B in the right heart. In individuals without transpulmonary passage of saline contrast bubbles, injected either at rest or after an exercise bout, no postdive arterialization was detected. Therefore, postdive VGE arterialization occurs in subjects that meet two criteria: 1) transpulmonary shunting of contrast bubbles at rest or at mild/moderate exercise and 2) VGE generation after a dive reaches the threshold grade. These findings may represent a novel concept in approach to diving, where diving routines will be tailored individually.

The influence of varying inspired fractions of O2 and CO2 on the development of involuntary breathing movements during maximal apnoea.

The growing urge to breathe that occurs during breath-holding results in development of involuntary breathing movements (IBMs). The present study determined whether IBMs are initiated at critical levels of hypercapnia and/or hypoxia during maximal apnoea. Arterial blood gasses at the onset of IBM were monitored during maximal voluntary breath-holds. Eleven healthy men performed breath holds after breathing air, hyperoxic-normocapnia, hypoxic-normocapnia, and normoxic-hypercapnia. Pre-breathing of the gas mixtures facilitated the IBM onset, reducing the time-to-onset for ∼46% (hyperoxic condition) and for ∼80% (hypoxic condition) compared to the normoxic air breathing time. A strong correlation (R=0.83, P=0.002) between arterial partial pressure of CO2 (PaCO2) at IBM onset after pre-breathing hyperoxic and hypercapnic gas mixtures was observed, suggesting the existence of a possible IBM PaCO2 threshold level of ∼6.5 ± 0.5 kPa. No clear "threshold" was observed for partial pressure of arterial O2(PaO2). However, we observed that IBM onset was influenced, in part, by an interaction between PaO2 and PaCO2 levels during maximal apnoea. This study demonstrated the complex interaction between arterial blood-gases and the physiological response to maximal breath holding.

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. The goal of the present study was to evaluate the generation of VGE in a group of divers using a mixture of compressed oxygen, helium, and nitrogen (trimix) and to probe for their potential appearance in arterial circulation. Seven experienced male divers performed three dives in consecutive days according to trimix diving and decompression protocols generated by V-planner, a software program based on the Varying Permeability Model. The occurrence of VGE was monitored ultrasonographically for up to 90 min after surfacing, and the images were graded on a scale from 0 to 5. The performed diving activities resulted in a substantial amount of VGE detected in the right cardiac chambers and their frequent passage to the arterial side, in 9 of 21 total dives (42%) and in 5 of 7 divers (71%). Concomitant measurement of mean pulmonary artery pressure revealed a nearly twofold augmentation, from 13.6 ± 2.8, 19.2 ± 9.2, and 14.7 ± 3.3 mmHg assessed before the first, second, and the third dive, respectively, to 26.1 ± 5.4, 27.5 ± 7.3, and 27.4 ± 5.9 mmHg detected after surfacing. No acute decompression-related disorders were identified. The observed high gas bubble loads and repeated microemboli in systemic circulation raise questions about the possibility of long-term adverse effects and warrant further investigation.

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. In addition, plasma antioxidant capacity (AOC) was measured by ferric reducing antioxidant power, and the level of oxidative stress was assessed by thiobarbituric acid-reactive substances (TBARS) method. Although the FMD was reduced to a similar extent after each dive, the comparison of predive FMD showed a reduction from 8.6% recorded before the first dive to 6.3% before the third (P = 0.03) and 5.7% before the sixth dive (P = 0.003). A gradual shift in baseline was also detected with TBARS assay, with malondialdehyde values increasing from 0.10 ± 0.02 µmol l⁻¹ before the first dive to 0.16 ± 0.03 before the sixth (P = 0.005). Predive plasma AOC values also showed a decreasing trend from 0.67 ± 0.20 mmol l⁻¹ trolox equivalents (first day) to 0.56 ± 0.12 (sixth day), although statistical significance was not reached (P = 0.08). This is the first documentation of acute endothelial dysfunction in the large conduit arteries occurring after successive deep trimix dives. Both endothelial function and plasma pro-oxidant and antioxidant activity did not return to baseline during the course of repetitive dives, indicating possible cumulative and longer lasting detrimental effects.

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. The echocardiographic parameters (bubble grade, lung comets, mean pulmonary arterial pressure (PAP), and left ventricular function) and the blood levels of the N-terminal part of pro-brain natriuretic peptide (NT-proBNP) were assessed before and after each dive. RESULTS: Venous gas bubbling was detected after each dive with mean probability of decompression sickness ranging from 1.77% to 3.12%. After each dive, several ultrasonographically detected lung comets rose significantly, which was paralleled by increased pulmonary artery pressure (PAP) and decreased left ventricular contractility (reduced ejection fraction at higher end-systolic and end-diastolic volumes) as well as the elevated NT-proBNP. The number of ultrasound lung comets and mean PAP did not return to baseline values after each dive. CONCLUSIONS: This is the first report that asymptomatic SCUBA dives are associated with accumulation of EVLW with concomitant increase in PAP, diminished left ventricular contractility, and increased release of NT-proBNP, suggesting a significant cardiopulmonary strain. EVLW and PAP did not return to baseline during repetitive dives, indicating possible cumulative effect with increasing the risk for pulmonary edema.