Biomedical subjects

K M Gallagher

Publications and source records attributed to K M Gallagher.

6 recordsLinked to original sources

PubMed1999

Ventilatory responses to dynamic exercise elicited by intramuscular sensors.

PURPOSE: Eight subjects, aged 27.0+/-1.6 yr, performed incremental workload cycling to investigate the contribution of skeletal muscle mechano- and metaboreceptors to ventilatory control during dynamic exercise. METHODS: Each subject performed four bouts of exercise: exercise with no intervention (CON); exercise with bilateral thigh cuffs inflated to 90 mm Hg (CUFF); exercise with application of lower-body positive pressure (LBPP) to 45 torr (PP); and exercise with 90 mm Hg thigh cuff inflation and 45 torr LBPP (CUFF+PP). Ventilatory responses and pulmonary gas exchange variables were collected breath-by-breath with concomitant measurement of leg intramuscular pressure. RESULTS: Ventilation (VE) was significantly elevated from CON during PP and CUFF+PP at workloads corresponding to > or = 60% CON peak oxygen uptake (VO2peak) and during CUFF at workloads > or = 80% CON VO2peak, P < 0.05. The VO2 at which ventilatory threshold occurred was significantly reduced from CON (2.17+/-0.28 L x min(-1)) to 1.60+/-0.19 L x min(-1), 1.45+/-0.15 L x min(-1), and 1.15+/-0.11 L x min(-1) during CUFF, PP, and CUFF+PP, respectively. The slope of the linear regression describing the VE/CO2 output relationship was increased from CON by approximately 22% during CUFF, 40% during PP, and 41% during CUFF+PP. CONCLUSIONS: As intramuscular pressure was significantly elevated immediately upon application of LBPP during PP and CUFF+PP without a concomitant increase in VE, it seems unlikely that LBPP-induced increases in VE can be attributed to activation of the mechanoreflex. These findings suggest that LBPP-induced reductions in perfusion pressure and decreases in venous outflow resulting from inflation of bilateral thigh cuffs may generate a metabolite sensitive intramuscular ventilatory stimulus.

Adult↗

PubMed1999

Carotid baroreflex function during prolonged exercise.

The present investigation was designed to uncouple the hemodynamic physiological effects of thermoregulation from the effects of a progressively increasing central command activation during prolonged exercise. Subjects performed two 1-h bouts of leg cycling exercise with 1) no intervention and 2) continuous infusion of a dextran solution to maintain central venous pressure constant at the 10-min pressure. Volume infusion resulted in a significant reduction in the decrement in mean arterial pressure seen in the control exercise bout (6.7 +/- 1.8 vs. 11.6+/- 1.3 mmHg, respectively). However, indexes of central command such as heart rate and ratings of perceived exertion rose to a similar extent during both exercise conditions. In addition, the carotid-cardiac baroreflex stimulus-response relationship, as measured by using the neck pressure-neck suction technique, was reset from rest to 10 min of exercise and was further reset from 10 to 50 min of exercise in both exercise conditions, with the operating point being shifted toward the reflex threshold. We conclude that the progressive resetting of the carotid baroreflex and the shift of the reflex operating point render the carotid-cardiac reflex ineffectual in counteracting the continued decrement in mean arterial pressure that occurs during the prolonged exercise.

Adult↗

PubMed1996

Diminished forearm vasomotor response to central hypervolemic loading in aerobically fit individuals.

The aim of this study was to test the hypothesis that cardiopulmonary baroreflex control of forearm vascular resistance (FVR) during central hypervolemic loading was less sensitive in exercise trained high fit individuals (HF) compared to untrained average fit individuals (AF). Eight AF (age: 24 +/- 1 yr and weight: 78.9 +/- 1.7 kg) and eight HF (22 +/- 1 yr 79.5 +/- 2.4 kg) voluntarily participated in the investigation. Maximal aerobic power (determined on a treadmill), plasma volume and blood volume (Evans blue dilution method) were significantly greater in the HF than AF (60.8 +/- 0.7 vs. 41.2 +/- 1.9 ml.kg-1.min-1, 3.96 +/- 0.17 vs 3.36 +/- 0.08 1, and 6.33 +/- 0.23 vs 5.28 +/- 0.13 1). Baseline heart rate (HR), central venous pressure (CVP), mean arterial pressure (MAP, measured by an intraradial catheter or a Finapres finger cuff), forearm blood flow (FBF, plethysmography), and FVR, calculated from the ratio (MAP-CVP)/FBF, were not different between the HF and the AF. Lower body negative pressure (LBNP, -5, -10, -15, and -20 torr) and passive leg elevation (LE, 50 cm) combined with lower body positive pressure (LBPP, +5, +10, and +20 torr) were utilized to elicit central hypovolemia and hypervolemia, respectively. Range of CVP (from LBNP to LE+LBPP) was similar in the AF (from -3.9 to +1.9 mm Hg) and HF (from -4.0 to +2.2 mm Hg). However, FVR/CVP was significantly less in the HF (-1.8 +/- 0.1 unit.mm Hg-1) than AF (-34 +/- 0.1 unit.mm Hg-1). The FVR decrease in response to increase in CVP was significantly diminished in the HF (-1.46 +/- 0.45 unit.mm Hg-1) compared to the AF (-4.40 +/- 0.97 unit.mm Hg-1), and during LBNP induced unloading the FVR/CVP of the HF (-2.01 +/- 0.49 unit.mm Hg-1) was less (P < 0.08) than the AF (-3.28 +/- 0.69 unit.mm Hg-1). We concluded that the cardiopulmonary baroreceptor mediated FVR reflex response was significantly less sensitive to changes in CVP in individuals who practice exercise training.

Adult↗

PubMed1996

Arterial and cardiopulmonary baroreflexes in 60- to 69- vs. 18- to 36-yr-old humans.

This study was designed to test the hypothesis that aging diminished baroreflex function during central hypovolemia. Eleven healthy young and eleven older (age 60-69 yr) individuals were assessed by using heart rate (HR) and mean arterial pressure (MAP) responses to neck pressure and suction during rest and lower body negative pressure (LBNP) of -15 Torr. The slope of forearm vascular resistance to central venous pressure during low-level LBNP was assessed as the index of cardiopulmonary baroreflex sensitivity. Baseline cardiovascular variables were not significantly different between the groups. In addition, there was no group difference in cardiopulmonary baroreflex (-3.6 vs. -3.7 units/mmHg for young vs. older, respectively) or carotid baroreflex (-0.39 vs. -0.35 beats.min-1.mmHg-1 and -0.26 vs. -0.35 mmHg/mmHg, for young vs. older, respectively) sensitivity. LBNP did not affect either HR or MAP, whereas it decreased CVP and increased FVR in both groups. LBNP significantly augmented the carotid-HR (-0.47 +/- 0.03 beats.min-1.mmHg-1) and carotid-MAP (-0.42 +/- 0.04 mmHg/mmHg) reflex gains in the young subjects only. We concluded that there was no difference in the discrete baroreflex function between the two age groups; however, the interaction of cardiopulmonary baroreceptors with carotid baroreflex function was absent in the older subjects, suggesting that the central integration of afferent neural inputs from the discrete baroreceptors was altered with aging.

Adult↗

PubMed1995

AIDS among the homeless of Boston: a cohort study.

We wanted to compare demographics, risk behaviors, AIDS-defining diagnoses, and survival between homeless and housed persons with AIDS in Boston from 1983 to 1991. Our retrospective cohort study used chart review to identify homeless AIDS cases and data from the Massachusetts AIDS Surveillance Program for comparison of homeless and nonhomeless cases. Seventy-two homeless and 1,536 nonhomeless Boston residents were reported to have AIDS between Jan. 1, 1983, and July 1, 1991. Homeless persons with AIDS were more likely to be African American or Latino (81 vs. 39%, p < 0.0001) and have i.v. drug use as a risk behavior (75 vs. 19%, p < 0.0001). The AIDS-defining diagnoses among the homeless were more commonly disseminated Mycobacterium tuberculosis (9 vs. 2%, p < 0.0001) and esophageal candidiasis (17 vs. 9%, p < 0.01). These differences were not seen when the populations were stratified by i.v. drug use. No significant difference in survival between the homeless and nonhomeless cohorts was found. Homeless individuals with human immunodeficiency virus are significantly different than housed persons, and at greater risk of invasive opportunistic infections. Appropriate clinical strategies can be developed to provide needed care to homeless persons with HIV.

Acquired Immunodeficiency Syndrome↗

PubMed1989

The Boulder and/or the Vail model: training preferences of clinical psychologists.

This study examined the preferences of Division 12 members (N=442) for doctoral training models (Boulder,Vail, equally Boulder and Vail) as a function of the respondent's own training program and current professional activities. Fifty percent favored the Boulder model, 14% the Vail model, and the remaining 36% both equally. However, as expected, preferences varied reliably according to one's doctoral training: Only 7% of the psychologists trained in a strong Boulder tradition preferred the Vail model, while only 10% of those trained in a strong Vail tradition favored the Boulder model. Current activities also were related systematically to training preference. These results argue for a more informed and restrained dialogue on the issue, which should be guided by the light of data rather than the heat of passion.

Colorado↗