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Biomedical subjects

L S Goodman

Publications and source records attributed to L S Goodman.

At least 19 recordsLinked to original sources
PubMed2000

Heart rate and blood pressure responses to +Gz following varied-duration -Gz.

BACKGROUND: The push-pull effect has been defined previously as decreased +Gz tolerance caused by previous baseline zero or -Gz exposure. Earlier work indicates that the delay in BP (BP) recovery during +Gz is a function of time at -G7, and is due to the lengthened time-course of sympathetically mediated peripheral vasoconstriction. HYPOTHESIS: The purpose of this study was to retrospectively determine whether heart rate (HR) varies with BP as duration at preceding -Gz increased. METHODS: Continuous ECG R-R interval data from 15 s of +2.25Gz after preceding 2, 5, 10, or 15 s at 2Gz obtained from previous experiments were analyzed and compared with the previously reported BP data. Repeated measures ANOVA and regression analyses were used to compare +2.25Gz HR responses after the four -Gz conditions and one control +2.25Gz condition. RESULTS: An initial rapid rise in HR was observed for all conditions with a consistent steady-state plateau achieved after the first 7 s of +2.25Gz. However, there were significant differences in mean HR attained during the +2.25Gz plateau for preceding 15 s -2.0 Gz vs. the control, 2, 5, and 10s -Gz conditions (109+/-1.1 vs. 102+/-1.8, 100+/-2.0, 97+/-1.1 and 101+/-1.1, bpm, respectively; p<0.05). CONCLUSIONS: HR, unlike BP, increases briskly across all preceding -Gz time conditions, adapting within the initial baroreflex-compensatory time frame typically expected for +Gz exposures. These results suggest there may be a threshold effect for HR response. Consequently, vasoconstrictor response is a critical adaptive mechanism during +Gz when preceded by long (>10 s) -Gz exposures.

Adaptation, Physiological↗
PubMed1998

The effect of lower body positive pressure on the cardiovascular response to exercise in sedentary and endurance-trained persons with paraplegia.

Exercise intolerance in persons with paraplegia (PARAS) is thought to be secondary to insufficient venous return and a subnormal cardiac output at a given oxygen uptake. However, these issues have not been resolved fully. This study utilized lower-body positive pressure (LBPP) as an intervention during arm crank exercise in PARAS in order to examine this issue. Endurance-trained (TP, n = 7) and untrained PARAS (UP, n = 10) with complete lesions between T6 and T12, and a control group consisting of sedentary able-bodied subjects (SAB, n = 10) were tested. UP and TP subjects demonstrated a diminished cardiac output (via CO2 rebreathing) during exercise compared to SAB subjects. Peak oxygen uptake (O2peak) remained unchanged for all groups following LBPP. LBPP resulted in a significant decrease in heart rate (HR) in UP and TP (P < 0.05), but not SAB subjects. LBPP produced an insignificant increase in cardiac output (Q) and stroke volume (SV). The significant decrease in HR in both PARA groups may indicate a modest hemodynamic benefit of LBPP at higher work rates where circulatory sufficiency may be most compromised. We conclude that PARAS possess a diminished cardiac output during exercise compared to the able-bodied, and LBPP fails to ameliorate significantly their exercise response irrespective of the conditioning level. These results support previous observations of a lower cardiac output during exercise in PARAS, but indicate that lower-limb blood pooling may not be a primary limitation to arm exercise in paraplegia.

Adult↗
PubMed1995

Central adaptations in aerobic circuit versus walking/jogging trained cardiac patients.

This study was done to determine (a) whether in coronary artery disease (CAD) left ventricular (LV) adaptations differed after 6 months of walking/jogging (legs-only, LO) versus aerobic circuit training (arms and legs, AL) versus a control group, and (b) whether a transfer of fitness to the untrained arms in the LO group was related to superior LV adaptations. Peak oxygen uptake for arm and leg ergometry and for cycle ergometry using radionuclide cardiac angiography were performed before and after training. Leg and arm VO2peak increased significantly by 13% in the AL group, and by 13% and 7%, respectively, for the LO group. LV function was greater after training for the LO versus the AL group. Improvements in systolic and diastolic function and a speculated hypervolemia explain these LV adaptations. In CAD patients, walking/jogging produces greater LV function improvements versus circuit training, possibly due to differences in the exercised muscle mass.

Adaptation, Physiological↗
PubMed1995

Cardiovascular effects of varying G-suit pressure and coverage during +1 Gz positive pressure breathing.

With the continued evolution of anti-G suits, used to counter the cardiovascular dysfunction arising from +1 Gz hypoxia protection positive pressure breathing (PPB), it was hypothesized that full-coverage anti-G-suits would offer equal protection while using lower inflation pressures than the traditional 4:1 ratio. Nine experienced subjects were exposed to 2 min of 70 mm Hg PPB while wearing either the COMBAT EDGE (CE) and Tactical Life Support System (TLSS) garments with the G-suit inflated to 4 x breathing pressure, and the Advanced Tactical Anti-G-Suit (ATAGS) at 4, 3, 2, and 1 x the breathing pressure. All subjects were measured with impedance cardiography (IC), and six were measured simultaneously with both IC and the Cardioscint nuclear probe. IC-estimated stroke volume, relative left ventricular (LV) end-diastolic volume, LV ejection fraction, and peak filling rate were depressed most in the CE and ATAGS 1 conditions (p < 0.001). Heart rate and mean arterial blood pressure changes were highest and lowest, respectively, using the CE and ATAGS 1 garments (p < 0.001). There were no differences in these variables between the TLSS and ATAGS 2-4 conditions. Thus, protection against the PPB-induced fall in LV preload and cardiovascular function may still be adequately afforded by lower G-suit inflation pressures when using full-coverage anti-G suits during PPB intended for high altitude-protection.

Blood Pressure↗
PubMed1994

Measurement of left ventricular function during arm ergometry using the VEST nuclear probe.

A chest-mounted left ventricular (LV) nuclear probe (VEST) for use during arm and leg ergometry is presented, with a discussion of the validity and reproducibility of LV function measures at rest and exercise. During both arm and leg ergometry in trained subjects, transient changes in LV function/volumes were observed. LV ejection fraction and relative end-systolic and end-diastolic volumes were 25 to 30% less with the arms versus the legs, agreeing with data from other studies using conventional techniques. At peak exercise with both limbs, LV ejection fraction and relative LV end-systolic volume increased, followed by immediate postexercise normalization. The effect was greatest with the arms and reflects the effect of high intramuscular and arterial pressures generated during arm cranking, leading to increased LV afterloading. The VEST permits rapid and noninvasive assessment of LV function during arm exercise, avoiding the limitations of other techniques.

Blood Pressure↗
PubMed1994

Increased G-suit coverage improves cardiac preloading conditions during positive pressure breathing.

A miniaturized nuclear probe (MNP) and multiple gated cardiac blood pool imaging (RCBI) were used to measure left ventricular function during positive pressure breathing (PPB) while wearing an extended-coverage (EC) vs. standard-coverage (SC) anti-G-suit. Seven subjects were exposed to 4.0 and 9.3 kPa PPB wearing each anti-G-suit during 3 min of PPB at ground level. Ejection fraction was unchanged using both techniques. The atrial component to diastolic filling was greater with the SC suit (p < 0.02). Using the MNP, end-diastolic and end-systolic volumes declined non-linearly over time at both PPB levels; these declines were greater with the SC G-suit (p < 0.001). Left ventricular preload declines during PPB. This is attenuated with increased G-suit coverage, confirming prior results using impedance cardiography. RCBI is less sensitive than MNP's for measuring non-steady-state cardiac physiology such as PPB.

Adult↗
PubMed1994

Cardiovascular responses with standard and extended bladder coverage G-suits during rapid decompression.

This study compared the cardiovascular responses of subjects exposed to 60,000 ft. rapid decompressions while wearing the Combined Advanced Technology Enhanced Design "G" Ensemble (COMBAT EDGE or CE) and the Tactical Life Support System (TLSS). Eight subjects were rapidly decompressed from 22,500 ft (6,858 m) to 60,000 ft (18,288 m), once wearing the CE ensemble and once wearing the TLSS ensemble. There were significant differences in heart rate, stroke volume, cardiac index, and mean arterial pressure (p < 0.0001), due to garment type, with TLSS providing better cardiovascular support. Oxygen saturation did not decrease to the same degree with CE as with TLSS (p < 0.0001). Both TLSS and CE provided sufficient physiological support to maintain oxygen saturations above 65% during the 3-min exposures to 60,000 ft altitude. Short-term physiological support at higher altitudes with greater PPB levels or longer duration excursions at 60,000 ft may not be possible without the greater G-suit bladder coverage and cardiovascular support provided by TLSS-type garments.

Adult↗
PubMed1993

Effect of extending G-suit coverage on cardiovascular responses to positive pressure breathing.

The purpose of this study was to compare cardiovascular responses of subjects exposed to long-duration positive pressure breathing (PPB) while wearing a standard (Combat Edge; CE) vs. extended coverage (Tactical Life Support System; TLSS) G-suit. Twelve experienced subjects, wearing TLSS and CE, were separately exposed to counterbalanced 60, 70, 80, and 88 mm Hg PPB for up to 10 min continuously. Termination resulted if presyncopal symptoms arose. G-suit inflation was 4 x mask/jerkin pressure. Using TLSS, all subjects completed 10 min of PPB at all levels, vs. 7 and 5 subjects completing 10 min at 80 and 88 mm Hg, respectively, using the CE ensemble (p < 0.001). Heart rate was significantly elevated at all PPB levels using CE (p < 0.0001) vs. TLSS. Stroke and Cardiac Indexes were significantly lower with CE at all levels vs. TLSS (p < 0.0001), and mean arterial blood pressure failed to be maintained at the 80 and 88 PPB mm Hg levels using CE (p < 0.0001). Extended G-suits afford superior protection against PPB-induced cardiovascular dysfunction vs. standard ensembles and consequently permit use of higher levels of PPB. This is due to the larger and more uniform application of pressure in the leg G-suit bladders, augmenting venous return and stroke volume.

Adult↗
PubMed1992

Ego receptivity and hypnotizability--two pilot studies: a brief communication.

Ego receptivity has been described as important for the psychotherapy process and as a characteristic of hypnosis (Deikman, 1974: Dosamantes-Alperson, 1979; Fromm, 1979). Receptivity also has been associated with a measure of absorption (Tellegen, 1981). In the first pilot study with 6 dance/movement therapy students, higher observer ratings of receptivity were associated with greater hypnotizability (r = .79, df = 4, p less than .05, 2-tailed test). In the second pilot study, the correlation was replicated (r = .51, df = 12, p = .06, 2-tailed test) with 14 dance/movement therapy students. In the second pilot study, receptivity did not correlate with absorption. Receptivity and absorption, however, accounted for 54% of hypnotizability population variance in a step-wise multiple regression. Receptivity accounted for a unique part of the variance after the effects of absorption were removed. It was concluded that receptivity should be explored as a potential predictor of hypnotizability, and that a reliable scaled measure of receptivity should be developed.

Adult↗
PubMed1992

Cardiovascular responses to positive pressure breathing using the tactical life support system.

The improved protection afforded by the Tactical Life Support System (TLSS) vs. other partial pressure ensembles has not been reported with respect to the cardiovascular effects of positive pressure breathing (PPB). Nine seated subjects wearing TLSS were exposed to 30, 50, and 70 mm Hg PPB (breathing air) with four times this pressure in the G-suit. Experiments were conducted at ground-level in order, separated by 4 min rest and preceded by a 1-min control period. Stroke volume and cardiac output (SV, CO) and indexes (SI, CI) were determined by impedance cardiography. Mean arterial pressure (MAP) was directly related to PPB level, increasing by 23%, 32%, and 47% for each PPB level, respectively (p less than 0.01). HR, SV, and CO were unaffected after 4 min of 30, 50, and 70 mm Hg PPB. The results indicate that cardiovascular function decay is less severe than that reported using other PPB ensembles at similar PPB levels. Improved protection is most likely due to the greater pressurization of the G-suit and the 45% greater bladder volume in the leg bladders, leading to restored venous return and SV.

Adult↗
PubMed1991

Cardiovascular adaptations in Andean natives after 6 wk of exposure to sea level.

Six male Quechua Indians (34.0 +/- 1.1 yr, 159.5 +/- 2.1 cm, 60.5 +/- 1.6 kg), life-long residents of La Raya, Peru (4,350-m altitude with an average barometric pressure of 460 Torr), were studied using noninvasive methods to determine the structural and functional changes in the cardiovascular system in response to a 6-wk deacclimation period at sea level. Cardiac output, stroke volume, and left ventricular ejection fractions were determined using radionuclide angiographic techniques at rest and during exercise on a cycle ergometer at 40, 60, and 90% of a previously determined maximal O2 consumption. Subjects at rest were subjected to two-dimensional and M-mode echocardiograms and a standard 12-lead electrocardiogram. Hemoglobin and hematocrit were measured on arrival at sea level by use of a Coulter Stacker S+ analyzer. After a 6-wk deacclimation period, all variables were remeasured using the identical methodology. Hemoglobin values decreased significantly over the deacclimation period (15.7 +/- 1.1 to 13.5 +/- 1.2 g/dl; P less than 0.01). The results indicate that the removal of these high-altitude-adapted natives from 4,300 m to sea level for 6 wk results in only minor changes to the cardiac structure and function as measured by these noninvasive techniques.

Acclimatization↗
PubMed1991

Right ventricular hypertrophy detected by echocardiography in patients with newly diagnosed obstructive sleep apnea.

We used polysomnography, echocardiography and ventilatory measurements to study 50 patients suspected of having OSA to determine a link to RVH. Twenty-eight patients (56 percent) had OSA and 20 (71 percent) of those had isolated RVH. We evaluated patients with RVH and divided them into two groups, those with apnea and those without apnea. The patients with sleep apnea were younger, weighed more, had greater BSA and had lower average oxygen saturations during the sleep study period. We divided the group with apnea into those with RVH and those without it. Those patients with RVH had a higher AI, longer average apnea time, a greater duration of longest apnea and a lower average oxygen saturation for the period of the sleep study. In addition, those with RVH had a lower average oxygen saturation during each apneic episode with a p value equaling 0.09.

Adolescent↗
PubMed1988

Ventilatory threshold and training heart rate in exercising cardiac patients.

The purpose of this study was to determine the relationship between previously prescribed training heart rates (THR) for patients training for six months or more in a cardiac rehabilitation program (CRP), calculated Karvonen percentage heart rate reserve (THRk), and the ventilatory threshold (VT). In twenty male patients (ages 41-63) with documented coronary heart disease (CAD) [non-medicated] mean training heart rate (THR, 75% HRmax) was determined by a telemetry during training sessions. Incremental treadmill testing for determinations of the gas-exchange VT VOE vs. (VO2, Excess CO2) was performed, and the HR at the VT (VTHR) was determined. VO2max was 35.57 +/- 5.57 mL.kg-1.min-1; the VT, expressed as a percentage of VO2max, was 54.45%. The mean THR (133.8 +/- 13.4 bpm) and calculated THRk (141.1 +/- 9.74 bpm) were significantly greater (p less than .05) than the VTHR (124.8 +/- 15.5 bpm), indicating that VT occurs below intensities determined by other methods.

Adult↗
PubMed1985

Steps in loudness summation.

The dependence of binaural loudness summation on interaural phase of tones ranging between 250 and 1400 Hz was investigated in a series of experiments using a loudness-matching procedure. Observers matched loudness of monaural-binaural and binaural-binaural pairs of alternating tones by adjusting the amplitude of one of the two. Adjustable and reference components of each tone pair were equal in frequency and were varied independently in interaural phase angle through the range +/- 177 degrees. For each tone frequency, steps in loudness summation of approximately 3 dB were obtained in the vicinity of a constant value of phase angle, theta t, which depends on the Hornbostel-Wertheimer constant (tau H) according to the relations theta t = 2 pi f tau H for tones of low frequency (f less than or equal to 1/2 tau H), and theta t = 2 pi(1 - f tau H) for tones of higher frequency (1/2 tau H less than or equal to f less than or equal to 1/tau H). Spatial relationships among alternating tones observed in the above conditions covaried with relative loudness in a complex manner, but exhibited qualitative changes in the vicinity of theta t.

Dominance, Cerebral↗
PubMed1979

Diazepam and drug-associated deaths. A survey in the United States and Canada.

This study describes a population of deceased persons in which death was generally caused by ingestion of numerous drugs, of which diazepam was only one agent. This drug occurred with high frequency relative to the total case load at each site, but its toxicological importance was often of a low order, and its role in the fatal cases was judged as minimal.

Adolescent↗