Hans Örnhagen

Effects of hyperbaric pressure and temperature on atria from ectotherm animals (Rana pipiens and Anguilla anguilla)

1. Spontaneously beating atria from frogs (R. pipiens) and eels (A. anguilla) were compressed hydraulically to 10 MPa. Effects on beating frequency and twitch tension were studied. 2. At low temperatures (8-10 degrees C) compression to 10 MPa caused a slowing of the beat frequency. No effects were noted at higher temperatures (16-24 degrees C). Twitch tension was decreased by pressure at low temperatures and increased at high temperatures. 3. Differences were noted between preparations from cold and warm acclimatized frogs, and from silver and yellow eels, respectively. 4. The effect of temperature acclimatization on pressure and temperature sensitivity is discussed in relation to data on cardiac phospholipid fatty acid composition.

A metabolic simulator for unmanned testing of breathing apparatuses in hyperbaric conditions.

BACKGROUND A major part of testing of rebreather apparatuses for underwater diving focuses on the oxygen dosage system. METHODS A metabolic simulator for testing breathing apparatuses was built and evaluated. Oxygen consumption was achieved through catalytic combustion of propene. With an admixture of carbon dioxide in the propene fuel, the system allowed the respiratory exchange ratio to be set freely within human variability and also made it possible to increase test pressures above the condensation pressure of propene. The system was tested by breathing ambient air in a pressure chamber with oxygen uptake (Vo₂) ranging from 1-4 L · min(-1), tidal volume (VT) from 1-3 L, breathing frequency (f) of 20 and 25 breaths/min, and chamber pressures from 100 to 670 kPa. RESULTS The measured end-tidal oxygen concentration (Fo₂) was compared to calculated end-tidal Fo₂. The largest average difference in end-tidal Fo₂during atmospheric pressure conditions was 0.63%-points with a 0.28%-point average difference during the whole test. During hyperbaric conditions with pressures ranging from 100 to 670 kPa, the largest average difference in Fo₂was 1.68%-points seen during compression from 100 kPa to 400 kPa and the average difference in Fo₂during the whole test was 0.29%-points. CONCLUSION In combination with a breathing simulator simulating tidal breathing, the system can be used for dynamic continuous testing of breathing equipment with changes in VT, f, Vo2, and pressure.

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.