Susan Kayar - Academia.edu (original) (raw)

Papers by Susan Kayar

Journal of applied physiology (Bethesda, Md. : 1985), 2001

A probabilistic model was used to predict decompression sickness (DCS) outcome in pigs during exp... more A probabilistic model was used to predict decompression sickness (DCS) outcome in pigs during exposures to hyperbaric H(2) to quantify the effects of H(2) biochemical decompression, a process in which metabolism of H(2) by intestinal microbes facilitates decompression. The data set included 109 exposures to 22-26 atm, ca. 88% H(2), 9% He, 2% O(2), 1% N(2), for 0.5-24 h. Single exponential kinetics described the tissue partial pressures (Ptis) of H(2) and He at time t: Ptis = integral (Pamb - Ptis). tau(-1) dt, where Pamb is ambient pressure and tau is a time constant. The probability of DCS [P(DCS)] was predicted from the risk function: P(DCS) = 1 - e(-r), where r = integral (Ptis(H(2)) + Ptis(He) - Thr - Pamb). Pamb(-1) dt, and Thr is a threshold parameter. Inclusion of a parameter (A) to estimate the effect of H(2) metabolism on P(DCS): Ptis(H(2)) = integral (Pamb - A - Ptis(H(2))). tau(-1) dt, significantly improved the prediction of P(DCS). Thus lower P(DCS) was predicted by mic...

Mitochondrial Dysfunction, 1993

Aviation Space and Environmental Medicine, 2008

It is just 100 years since the publication of J. S. Haldane&amp;amp;amp;#39;s groundbreak... more It is just 100 years since the publication of J. S. Haldane&amp;amp;amp;#39;s groundbreaking work on the prevention of decompression sickness (DCS). While we still do not know the exact mechanisms that underlie DCS, probabilistic modeling now allows good estimation of risk for a given set of conditions, although reduction of risk to zero remains impractical. Unfortunately, individual monitoring for intravascular bubbles has not proven a good predictor of symptomatic DCS. Current research aims to identify underlying biological factors that, once understood, may allow development of preventive measures and treatment that go beyond recompression. With one or more drugs to combat DCS, we should be able to eliminate the residual risk, extend dive profiles beyond current limits, and rescue people who have exceeded the limits and taken a hit.

Comparative Biochemistry and Physiology Part A: Physiology, 1981

Aviation, Space, and Environmental Medicine, 2008

Aviation Space and Environmental Medicine, Aug 1, 2006

Environmental temperature is commonly thought to modulate decompression sickness (DCS) risk, but ... more Environmental temperature is commonly thought to modulate decompression sickness (DCS) risk, but the literature is mixed regarding which conditions elicit the greatest risk. If temperature is a risk factor, then managing thermal exposure may reduce DCS incidence. We analyzed whether hot or cold conditions during or immediately after a hyperbaric exposure altered DCS incidence in a rat model. Rats (eight groups of five animals in each of nine conditions; mean body mass +/- SD = 259.0 +/- 9.2 g) were placed in a dry chamber that was pressurized with air to 70 m (8 ATA) for 25 min, followed by rapid (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 30 s) decompression under a series of temperature conditions (35 degrees, 27 degrees, or 10 degrees C during compression; 35 degrees, 20 degrees, or 10 degrees C post-decompression). Animals were observed for 30 min post-decompression for signs of DCS. DCS incidence in the 27 degrees C compression/20 degrees C post-decompression group was 50% by design. Data from all nine groups of paired temperature conditions were compared with each other using analysis of variance, Chi-square tests, and logistic regression. No significant differences in DCS incidence were found among the groups (30-52.5% DCS incidence per group, 42% DCS incidence overall). This animal model emphasized potential temperature effects attributable to tissue N2 load acquired during compression; there was no evidence that environmental temperature from 10-35 degrees C during or post-dive modulated DCS incidence. It remains to be determined if temperature modulates DCS risk as a function of variable N2 elimination rates.