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Objective: Hyperoxia is known to influence cardiovascular and endothelial function, but it is unknown if there are differences between younger and older persons. The aim of this study was to monitor changes in myocardial diastolic function and flow-mediated dilatation (FMD) in younger and elderly volunteers, before and after exposure to relevant hyperbaric hyperoxia. Methods: 51 male patients were separated into two groups for this study. Volunteers in Group 1 (n=28, mean age 26±6, “juniors”) and Group 2 (n=23, mean age 53±9, “seniors”) received standard HBO2 protocol (240kPa oxygen). Directly before and after hyperoxic exposure in a hyperbaric chamber we took blood samples (BNP, hs-troponin-t), assessed the FMD and echocardiographic parameters with focus on diastolic function. Results: After hyperoxia we observed a high significant decrease in heart rate and systolic/diastolic FMD. Diastolic function varied in both groups: E/A ratio showed a statistically significant increase in Group 1 and remained unchanged in Group 2. E/e’ ratio showed a slight but significant increase in Group 1, whereas e’/a’ ratio increased in both groups. Deceleration time increased significantly in all volunteers. Isovolumetric relaxation time remained unchanged and ejection fraction showed a decrease only in Group 2. There were no changes in levels of BNP and hs-troponin-t in either group. Conclusion: Hyperoxia seems to influence endothelial function differently in juniors and seniors: FMD decreases more in seniors, possibly attributable to pre-existing reduced vascular compliance. Hyperoxia-induced bradycardia induced a more pronounced improvement in diastolic function in juniors. The ability of Group 1 to cope with hyperoxia-induced effectsdid not work in the same manner as with Group 2.

BACKGROUND: Seasickness is a risk aboard a ship. Histamine is postulated as a causative agent, inversely related to the intake of vitamin C. Persons with mastocytosis experienced improvement of nausea after the intake of vitamin C. OBJECTIVE: To determine whether vitamin C suppresses nausea in 70 volunteers who spent 20 minutes in a life raft, exposed to one-meter-high waves in an indoor pool. METHOD: Double-blind placebo-controlled crossover study. Two grams of vitamin C or placebo was taken one hour before exposure. Blood samples were taken one hour before and after exposure to determine histamine, diamine oxidase, tryptase, and vitamin C levels. Symptom scores were noted on a visual analog scale. On the second day the test persons were asked which day they had felt better. RESULTS: Seven persons without symptoms were excluded from the analysis. Test persons had less severe symptoms after the intake of vitamin C (p < 0.01). Scores on the visual analog scale were in favor of vitamin C, but the difference was not significant. Twenty-three of 63 persons wished to leave the raft earlier: 17 after the intake of placebo and 6 after the intake of vitamin C (p < 0.03). Women (p < 0.02) and men below 27 years of age (p < 0.02) had less pronounced symptoms after the intake of vitamin C. Histamine (p < 0.01) and DAO levels were increased after the intake of vitamin C (p < 0.001) and after placebo (n.s.). The fact that the second test day was rated less stressful by most volunteers is indicative of habituation. CONCLUSIONS: Some of the data show that vitamin C is effective in suppressing symptoms of seasickness, particularly in women and men younger than 27 years of age, and is devoid of side effects. Histamine levels were initially increased after the test persons had been exposed to waves.

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Hypovolemia is known to be a predisposing factor of decompression illness (DCI) while diving. The typical clinically impressive neurological symptoms of DCI may distract from other symptoms such as an incipient hypovolemic shock. We report the case of a 61‐year‐old male Caucasian, who presented with an increasing central and peripheral neural failure syndrome and massive hypovolemia after two risky dives. Computed tomography (CT) scans of the chest and Magnetic resonance imaging scans of the head revealed multiple cerebral and pulmonary thromboembolisms. Transesophageal echocardiography showed a patent foramen ovale (PFO). Furthermore, the patient displayed hypotension as well as prerenal acute kidney injury with elevated levels of creatinine and reduced renal clearance, indicating a hypovolemic shock. Early hyperbaric oxygen (HBO) therapy reduced the neurological deficits. After volume expansion of 11 liters of electrolyte solution (1000 mL/h) the cardiopulmonary and renal function normalized. Hypovolemia increases the risk of DCI during diving and that of hypovolemic shock. Early HBO therapy and fluid replacement is crucial for a favorable outcome.

During exposure to 280 kPa oxygen at rest a constant delay of approximately 20 min precedes the onset of central nervous oxygen toxicity. An increase in CBFV may indicate the impending seizure.

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