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Biomedical subjects

D Kerem

Publications and source records attributed to D Kerem.

35 records · Page 2Linked to original sources
PubMed1988

Ventilatory response to transient hypoxia in O2 divers.

This study addresses the question of whether repeated acute exposure to hyperbaric oxygen, such as encountered in O2 diving, affects the peripheral oxygen chemosensors. Groups of nondivers, active O2 divers, and ex-O2 divers, as well as active air scuba divers, were given 1 or both of 2 tests that measure the ventilatory response to transient hypoxia. Results showed that all groups of divers have a mean response similar to or higher than that of nondivers as well as that of normal subjects, as reported in the literature. A repeat test on 10 diving candidates before and after 200 h of accrued O2 diving also did not show an impairment in the hypoxic ventilatory response. Oxygen diving within the established depth and time limits does not seem to cause cumulative damage to the peripheral O2 chemosensors.

Adult↗
PubMed1984

Independence of hypoxic death of inspiratory PCO2 in rats and fossorial mole rats.

Laboratory white rats and fossorial mole rats (Spalax ehrenbergi) were subjected to progressive hypoxia by enclosure in a thermoregulated, confined atmosphere. Variable levels of environmental CO2 were obtained by controlling the duration of CO2 absorbance. Rats had preimplanted electroencephalographic (EEG) and electrocardiographic (EKG) electrodes and a rectal temperature probe. Animals were followed until their last gasp and EEG flattening, at which time the chamber's atmosphere was analyzed. The mole rat demonstrated a significantly lower terminal PIO2 [20.9 +/- 3.5 (SD) vs. 38.0 +/- 8.4 (SD) Torr]; however, in both animals terminal PIO2 was independent of PICO2 over a range of the latter of 0-117 Torr. Rats showed a progressive decline in rectal temperature from a PIO2 of 80 Torr on, amounting finally to 2.3 degrees C. The rats' oxygen consumption was maintained down to a PIO2 of 65 Torr and declined from then on. A group of rats with maximal CO2 accumulation showed a greater decline of rectal temperature and a steeper drop of VO2 with respect to PO2 compared to a group with no CO2 buildup. The main result was unexpected, in view of the theoretical synergism of the adverse effects of hypoxia and hypercapnia, and should reorient current thinking on survival and resuscitation in confined spaces.

Animals↗
PubMed1983

Factors affecting ventilatory lung function in young Navy selectees.

Ventilatory lung function was studied in 528 Navy selectees 16 to 23 yr of age. Analysis of the pulmonary function data indicated that height and chest circumference were the best "predictors" of forced vital capacity (FVC) and forced expiratory volume in one second (FEV1). Other factors, such as amount of sports activity, ethnicity, weight, or Quetelet index, were of minimal predictive value. Linear prediction formulas of ventilatory lung function for young male adults of this age range were derived. Analysis of variance showed that the apparently greater FVC found in smokers than that found in nonsmokers was related to the smokers being older and consequently taller than the nonsmokers. After adjusting for age (even in this narrow age range) and height, no difference in pulmonary function between the 2 groups could be demonstrated.

Adolescent↗
PubMed1981

Bubble dynamics in perfused tissue undergoing decompression.

A mathematical model describing bubble dynamics in a perfused tissue undergoing decompression is presented, taking into account physical expansion and inward diffusion from surrounding supersaturated tissue as growth promoting factors and tissue gas elimination by perfusion, tissue elasticity, surface tension and inherent unsaturation as resolving driving forces. The expected behavior after a step reduction of pressure of a bubble initially existing in the tissue, displaying both growth and resolution has been demonstrated. A strong perfusion-dependence of bubble resolution time at low perfusion rates is apparent. The model can account for various exposure pressures and saturation fractions of any inert gas-tissue combination for which a set of physical and physiological parameters is available.

Animals↗
PubMed1981

The transportable recompression rescue chamber as an alternative to delayed treatment in serious diving accidents.

This report summarizes experience in the use of a Transportable Recompression Rescue Chamber (TRRC) for one man in the rapid initiation of treatment and evacuation in severe scuba diving accidents. An evacuation system is described which incorporates the centralized management of all diving accidents and standardized TRRCs capable of interlocking under pressure with the stationary medical chamber. Oxygen breathing capability in the TRRC allows the use of up-to-date U.S. Navy oxygen treatment tables. Included are 19 cases of Type II decompression sickness and pulmonary barotrauma with neurological manifestations, most of which occurred at remote diving sites with no nearby walk-in chambers. Case analysis includes distance and means of evacuation, delay in initiating therapy, time spent in TRRC, and initial and final outcome. Together, TRRCs and airborne evacuation to a stationary medical chamber insures a minimal delay between the onset of symptoms and the start of recompression therapy. The use of the TRRC is a prime factor in minimizing delay. No complications associated with the use of TRRCs have been encountered. Ideally, evacuation should be made in a pressurized two-compartment (for a victim and an attendant) chamber. However, if this is not available we strongly advocate the use of one-man pressurized TRRCs over unpressurized evacuation.

Barotrauma↗
PubMed1981

Interactions of thiopentone, light mineral oil, and pressure at frog sciatic nerve.

Combinations of thiopentone, light mineral oil, and pressure to as much as 160 ATA were applied to the isolated, thermostated (18 degrees C) frog sciatic nerve. Amplitude and rise rate of the compound action potential were examined and compared to the response in Ringer's solution. Immersion in mineral oil caused no change in the response. Pressure, whether applied by helium or after immersion in mineral oil, caused mainly reversible slowing of the response, as did thiopentone by itself, up to at least 5.1 mM. Thiopentone (3.2mM) and helium pressure up to 114 ATA were reversibly synergistic, in that the response was markedly slowed and reduced. Nerves that had been immersed in 3.2 mM thiopentone were placed in mineral oil; this procedure caused a reduction in the size of the response. Application of pressure then eliminated the response, and decompression did not lead to its recovery until the nerve was repeatedly rinsed in Ringer's solution. The findings question the inertness of mineral oil to excitable membranes and indicate that caution should be exercised in its use as a compression medium.

Animals↗
PubMed1980

Alveolar Pco2 during rest and exercise in divers and non-divers breathing O2 at 1 ATA.

The extent of hypercapnia in oxygen-breathing subjects was investigated during rest and exercise (650 kpm/min). Divers, ex-divers, and non-divers were studied. Carbon dioxide retention was judged by end-tidal Pco2 values achieved after a few minutes at each state. End-breath-hold (EBH) PAco2 was also measured in the two states to assess the contribution of breathing pattern to CO2 retention. Findings indicated a pronounced hypoventilation and hypercapnia in the divers during exercise, and a mean exercise EBH PAco2 value 15 mmHg greater than that in non-divers. Ex-divers had group mean values not significantly different from those of active divers. Superimposed inspired CO2 load caused similar elevations in PAco2 values in divers and non-divers. We concluded that CO2 retention in exercising oxygen-breathing divers cannot be accounted for solely as a conditioned breathing behavior, may be due partly to a reduced central responsiveness of CO2, and is not dependent on current diving activity.

Adolescent↗
PubMed1980

Ventilatory and occlusion-pressure responses to hypercapnia in divers and non-divers.

Ventilatory (VE/PCO2) and occlusion-pressure (P0.1/PCO2) responses to progressive hypercapnia (rebreathing method of Read (1)) were estimated in 20 normal subjects and 22 scuba divers. Indexes of CO2 sensitivity (slopes of response curves) and absolute response values under strong CO2 drive (PCO2 = 60 mmHg) were significantly lower in the diver group. Individual CO2 sensitivity did not correlate with either diving experience or current diving activity. Positively skewed (log-normal) frequency distribution curves of individual CO2 sensitivities were drawn for the divers and for a larger sample of normal controls (using data from other studies). All divers' values fell in the lower range of non-diver control values and about one-third were below the normal range (mean +/- 2 SD) for CO2 sensitivity. We concluded that our divers did not represent a distinct population different from the normal one but rather a group of normal healthy subjects with either an inherent or acquired relatively low CO2 response. The rebreathing technique is strongly advocated as a tool for investigating divers' CO2 sensitivity and its implications in underwater environments.

Adult↗
PubMed1978

Influence of a GABA transaminase inhibitor on central nervous system oxygen toxicity.

A decrease in brain GABA concentration has been implied as the cause of convulsions induced by hyperbaric oxygen (HOP). We therefore examined the influence of sodium valproate, an anticonvulsant and GABA transaminase inhibitor on HOP-induced convulsions in rats. The mean latency of occurrence of the first electrical discharge in the ECoG and the appearance of the first clinical seizure in awake chronically implanted rats was unchanged by administration of sodium valproate prior to HOP exposure. We conclude that either the sodium valproate inhibition of GABA removal is insufficient to compensate for HOP inhibition of its production, or else that GABA concentration changes are not causally related to HOP-induced seizures.

4-Aminobutyrate Transaminase↗