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Biomedical subjects

H Ornhagen

Publications and source records attributed to H Ornhagen.

14 recordsLinked to original sources
PubMed2003

Incidence and risk factors for symptoms of decompression sickness among male and female dive masters and instructors--a retrospective cohort study.

UNLABELLED: The aim was to determine the incidence of symptoms of decompression sickness (DCS) in dive masters and instructors in relation to number of dives and possible risk factors. STUDY DESIGN: Retrospective cohort study of dive masters and instructors in Sweden. STUDY BASE: All dive masters and instructors listed with PADI, NAUI and CMAS in Sweden as of January 1st 1999 (2380 divers). METHODS: The dive masters and instructors received a validated questionnaire on diving activities and symptoms of DCS in 1999. 1516 men and 226 women answered, i.e. 73% of the initial study base. RESULTS: DCS symptoms were reported by 190 divers. The incidence of DCS symptoms was 1.52 for males and 1.27 for females per 1000 dives. Dive masters, divers not performing decompression-stop dives, divers not practicing advanced diving and divers with a low number of total lifetime dives had a higher proportion (p < 0.05) of DCS symptoms per 1000 dives. There were no major differences in DCS symptom incidence related to sex, age, asthma, overweight or alcohol abuse in this study.

Adult↗
PubMed2002

Erythropoietin concentrations during 10 days of normobaric hypoxia under controlled environmental circumstances.

Serum erythropoietin levels (s-[epo]), haemoglobin concentration ([Hb]), haematocrit (hct), and ferritin concentration ([fer]) were measured in seven healthy male volunteers (20-23 years) exposed continuously to hypoxia (PO(2) 14 kPa) for 10 days. Serum erythropoietin concentration increased significantly from 9.5 +/- 3.51 to 33.6 +/- 11.64 U L(-1) (P < 0.05) after 2 days of hypoxia. Thereafter, s-[epo] decreased. However, after 10 days s-[epo] was 18.7 +/- 5.83 U L(-1) which was still increased above the pre-hypoxia level (P < 0.05). Serum haemoglobin concentration and hct increased over the 10 days of hypoxia, [Hb] from 152 +/- 8.9 to 168 +/- 9.2 gL(-1) (P < 0.001), and hct from 43 +/- 2.4 to 49 +/- 2.6% (P < 0.001). Ferritin concentration decreased significantly during the hypoxic exposure from 82 +/- 46.9 to 44 +/- 31.7 mmol L(-1) after 10 days (P < 0.01). In conclusion, the initial increase of s-[epo] under controlled normobaric hypoxia was marked, 353%, and levelled off after 5-10 days at 62-97% above normoxia level. There was also a significant increase in [Hb] and hct and a decrease in [fer] after 10 days of exposure to normobaric hypoxia.

Adaptation, Physiological↗
PubMed2000

Cerebrospinal fluid levels of monoamine compounds and cholecystokinin peptides after exposure to standardized barometric pressure.

BACKGROUND: Connections between mood changes and weather have been described throughout the ages, and in more recent years, there have been reports on a relationship between atmospheric pressure and neurotransmitter levels in cerebrospinal fluid. METHODS: To further investigate this issue under strictly standardized conditions, we have lumbar-punctured 8 healthy males under low (963 hPa) and high (1064 hPa) barometric pressure, using a pressure chamber. RESULTS: Under high pressure, the tyrosine concentrations in the cerebrospinal fluid (CSF) were lower, while the cholecystokinin tetrapeptide (CCK-4) levels were higher. No differences between low and high pressure were found for tryptophan, 5-hydroxyindolacetic acid (5-HIAA), dopamine (DA), and sulphated cholecystokinin octapeptide (CCK-8S). The serum level of CCK-8S was higher under high pressure. On comparing concentration ratios between the second and the first CSF fraction, we found significantly increased ratios for homovanillic acid (HVA) and 4-hydroxy-3-methoxyphenylglycol (HMPG), but a decreased ratio for tyrosine under high pressure. The difference in the concentration ratios of HVA between low and high pressure correlated negatively with age. Intraspinal pressure correlated negatively with tapping time at low pressure. CONCLUSION: Our results are in line with the hypothesis that atmospheric pressure influences CSF levels of monoamine compounds and cholecystokinin peptides.

Adult↗
PubMed1997

Effects of reduced oxygen partial pressure on cognitive performance in confined spaces.

The reduction of oxygen levels is a technique used both for fire fighting and fire protection in confined spaces. The purpose of this study was to find out if and how reduced oxygen levels affect cognitive performance in a small group of persons living in a confined space such as a submarine. In 3 separate experiments lasting for 11 to 14 days, a total of 22 men were exposed to normoxic and different levels of hypoxic normobaric atmospheres (15, 14, and 13 kPa O2). Each participant completed a cognitive test battery twice every 24-hr period in the first 2 experiments, but only once a day in the 3rd experiment. Performance in almost all tests improved with the number of test sessions performed, despite reductions of the oxygen partial pressure. Under the conditions tested, cognitive performance decrements could not be observed if inspiratory oxygen partial pressure was kept above 13 kPa.

Adult↗
PubMed1997

Effects of normobaric hypoxic confinement on visual and motor performance.

INTRODUCTION: The use of reduced oxygen levels has been suggested for fire prevention in closed spaces, such as submarines. However, if humans are to work and live in environments with reduced oxygen levels, the effect of hypoxia on human performance must be further assessed. METHODS: In 3, 11- to 14-d confinements a total of 22 subjects were exposed to different levels of normobaric hypoxia (13, 14, and 15 kPa O2), for up to 10 d, with intervening periods of normoxia. In each experiment eight subjects were divided into two teams, working in 6-h shifts around the clock. Subjects performed tests of spatial orientation, visual reaction time, parallel processing and motor skills. Performance tests and questionnaires were administered once or twice in every 24-h period. RESULTS: All of the subjects appeared to tolerate the acute reduction in oxygen partial pressure well. In many of the tests performance improved with time as a result of learning, despite reductions in the oxygen level. No reduction in performance or decrease in rate of learning was observed at any of the oxygen levels tested. CONCLUSIONS: Oxygen levels down to 14 kPa appear not to impair visual and motor performance during rest.

Adult↗
PubMed1993

Breathing volumes and gas exchange during simulated rapid free ascent from 100 msw.

The crew of a disabled submarine can be rescued by means of free ascent through the water to the surface. Pulmonary gas exchange was studied during simulated rapid free ascent in subjects standing immersed to the neck in a pressure chamber. The pressure was rapidly increased to 1.1 MPa [100 meters seawater (msw)] followed by decompression at 0.03 MPa/s (3 msw/s). Effective inspired tidal volume, as estimated by an Ar dilution method, fell gradually to zero during decompression from 20 to 0 msw. Directly determined expired tidal volumes were increased up to two to three times at the time of return to surface pressure compared with pre- and postdecompression volumes. End-tidal PCO2 was increased on compression and fell to a nadir of 3.4 kPa (25 Torr) at the time of return to surface pressure. Thus, intrapulmonary gas expansion caused simultaneous inspiratory hypoventilation and expiratory hyperventilation. If O2-enriched gas is to be used to reduce the risk of decompression sickness, it should be administered early during decompression to alter the intrapulmonary gas composition. The time course of arterial PCO2 changes as reflected by end-tidal values during short-lasting compression/decompression would act to promote inert gas supersaturation in the brain.

Adult↗
PubMed1992

Reduced voluntary non-visual suppression of the vestibulo-ocular reflex gain during nitrous oxide narcosis.

The effect of subanesthetic nitrous oxide (N2O) narcosis (21%) on the vestibulo-ocular reflex (VOR) and on voluntary non-visual suppression of the VOR was studied in 12 subjects, using a velocity step rotational test. Gain and time constant of the VOR were calculated by computer. During tests, the subjects were required either to perform mental arithmetic or to attempt to follow an imaginary target rotating with them in the dark. Voluntary non-visual suppression of gain was significantly reduced during exposure to N2O, though there was no statistically significant effect of N2O on gain per se. The time constant was unaffected either by voluntary suppression or by N2O. The reducing effect of N2O on voluntary non-visual suppression of VOR gain is assumed to be due to reduced alertness. Reduced voluntary non-visual suppression of VOR may imply reduced visual-vestibular interaction, which might be one explanation of the complaints of dizziness associated with fatigue or with ingestion of certain sedatives.

Adult↗
PubMed1989

Evaluation of smooth pursuit and voluntary saccades in nitrous oxide-induced narcosis.

The effect of inhaling nitrous oxide on pursuit eye movements (PEM) and voluntary saccades was studied in nine healthy subjects. Eye movements were recorded before, during, and 10 min after exposure for 15 min to normoxic mixtures of 14%, 21%, and 28% nitrous oxide. At all concentrations, there was a significant decrease in gain of PEM at a target velocity of 60 degrees/s, the decrease being of comparable magnitude at concentrations of 14% and 21%. By 10 min after exposure to nitrous oxide, the gain of PEM had recovered to pre-test values. There was also a highly significant decrease in the peak velocity of voluntary saccades at all concentrations of nitrous oxide; the decrease was more pronounced at the higher concentrations, and the existence of a dose-dependent relationship is suspected. Exposure to 21% nitrous oxide for only 2 min was enough to induce significant reduction in peak velocity of voluntary saccades. By 10 min after exposure to nitrous oxide, the peak velocity of voluntary saccades had recovered but had not reached pre-test values. The findings suggest that both PEM and voluntary saccades decrease with reduced alertness in mild narcosis. Moreover, as the effects of nitrous oxide are considered typical of inert gases in general, our findings suggest that voluntary eye movements may also be a suitable variable for use in assessing the effects of inert gas narcosis.

Adult↗
PubMed1977

Eustachian tubal function during immersion.

The effects of head-out immersion on active and passive middle ear pressure equilibration were studied in three otologically normal scuba divers. Results were compared with the equilibration capacity recorded in the nonimmersed sitting and supine positions. Head-out immersion had only a minor effect on the ability to equilibrate the middle ear pressure actively during descent; passive ear clearing during ascent was slightly more difficult compared with this capacity in the sitting nonimmersed position. In the supine position ear clearing was significantly more difficult during both ascent and descent, which indicates that it is preferable to assume an upright body posture during exposures to pressure changes in dry pressure chambers. Mechanisms that might influence the ability to equilibrate the middle ears are discussed.

Adult↗
PubMed1975

Nausea and abdominal discomfort--possible relation to aerophagia during diving: an epidemiologic study.

Gastrointestinal (GI) distension by gas expansion may be more of a problem in diving than is usually recognized. In response to a written questionnaire, 2053 scuba divers gave information about GI discomfort such as pain, nausea, and vomiting in connection with diving. One hundred and eleven reports (5.4% of 2053) were considered possible cases of significant GI distension because the majority of divers had their symptoms during ascent and a significant number of them got relief from belching. Difficult middle ear pressure equilibration was a particular problem among divers with GI symptoms. It may have induced frequent swallowing, causing air ingestion and consequent GI problems. Steep, head-first descents appear to have been employed in some dives, leading to GI discomfort presumably be creating large mouth-to-stomach gas-pressure differences. It was concluded that swallowing or any procedure leading to entry of gas into the stomach should be avoided and that belching during diving should be recommended.

Abdominal Pain↗
PubMed1975

Influence of body posture and ear clearing on body buoyancy during diving.

The amount of gas introduced into the gastrointestinal (GI) tract during diving was studied by underwater weighing. The influence of body posture and ear clearing methods was determined. Ten subjects were studied in wet simulated dives to a 30-m depth. Clearing the ears by swallowing and descending head first gave a mean weight reduction (before dive-after dive) of 0.29 kg; descending in the upright position gave a mean weight reduction of 0.16 kg. Swallowing during descent (upright posture) caused a 0.11 kg greater weight reduction than blowing against the clamped nose. The greatest weight reduction (1.34 kg) occurred in a head-first dive (swallowing) with 7 cycles of depth changes between 30 and 25 m. During the ascent the subject experienced considerable abdominal discomfort. It was concluded that swallowing during diving, particularly in the head-down position, may introduce large amounts of gas into the GI tract and that during diving one should try to eliminate ingested gas by belching.

Aerophagy↗