Journal of applied physiology
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We investigated the effects of modified hemoglobin on regional blood flow and function of different organs during hyperdynamic sepsis. Fourteen sheep were surgically prepared for the study. After a 5-day recovery period, a continuous infusion of live Pseudomonas aeruginosa bacteria was begun and maintained for 48 h. ⋯ PHP infusion did not decrease regional blood flow, measured with fluorescent microspheres, below the baseline values in any of the analyzed tissues. None of the investigated blood chemistry variables showed any changes indicative of impaired organ function after PHP infusion. In our model of ovine sepsis we found no side effects after PHP infusion that would limit the use of PHP as a nitric oxide scavenger in sepsis.
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Clinical Trial
Qualitative aspects of exertional dyspnea in patients with interstitial lung disease.
We compared qualitative and quantitative aspects of perceived exertional dyspnea in patients with interstitial lung disease (ILD) and normal subjects and sought a physiological rationale for their differences. Twelve patients with ILD [forced vital capacity = 64 +/- 4 (SE) %predicted] and 12 age-matched normal subjects performed symptom-limited incremental cycle exercise tests with measurements of dyspnea intensity (Borg scale), ventilation, breathing pattern, operational lung volumes, and esophageal pressures (Pes). Qualitative descriptors of dyspnea were selected at exercise cessation. ⋯ Borg-O2 uptake (VO2) and Borg-ventilation slopes were significantly greater during exercise in patients with ILD (P < 0.01). At peak exercise, when dyspnea intensity and inspiratory effort (Pes-to-maximal inspiratory pressure ratio) were similar, the distinct qualitative perceptions of dyspnea in patients with ILD were attributed to differences in dynamic ventilatory mechancis, i.e., reduced inspiratory capacity, heightened Pes-to-tidal volume ratio, and tachypnea. Factors contributing to dyspnea intensity in both groups were also different: the best correlate of the Borg-VO2 slope in patients with ILD was the resting tidal volume-to-inspiratory capacity ratio (r = 0.58, P < 0.05) and in normal subjects was the slope of Pes-to-maximal inspiratory pressure ratio over VO2 (r = 0.60, P < 0. 05).
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The purpose of the present study was to determine the separate and combined effects of aerobic fitness, short-term heat acclimation, and hypohydration on tolerance during light exercise while wearing nuclear, biological, and chemical protective clothing in the heat (40 degrees C, 30% relative humidity). Men who were moderately fit [(MF); <50 ml . kg-1 . min-1 maximal O2 consumption; n = 7] and highly fit [(HF); >55 ml . kg-1 . min-1 maximal O2 consumption; n = 8] were tested while they were euhydrated or hypohydrated by approximately 2.5% of body mass through exercise and fluid restriction the day preceding the trials. Tests were conducted before and after 2 wk of daily heat acclimation (1-h treadmill exercise at 40 degrees C, 30% relative humidity, while wearing the nuclear, biological, and chemical protective clothing). ⋯ In both MF and HF groups, hypohydration significantly increased Tre and heart rate and decreased the respiratory exchange ratio and the TT regardless of acclimation state. Overall, the rate of rise of skin temperature was less, while DeltaTre, the rate of rise of Tre, and the TT were greater in HF than in MF subjects. It was concluded that exercise-heat tolerance in this uncompensable heat-stress environment is not influenced by short-term heat acclimation but is significantly improved by long-term aerobic fitness.
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Airway dilation is one of the many autonomic responses to exercise. Two neural mechanisms are believed to evoke these responses: central command and the muscle reflex. Previously, we found that activation of central command, evoked by electrical and chemical stimulation of the mesencephalic locomotor region, constricted the airways rather than dilated them. ⋯ We found that activation of the hypothalamic locomotor region by electrical and chemical stimuli evoked fictive locomotion and, for the most part, airway constriction. Fictive locomotion also occurred spontaneously, and this too, for the most part, was accompanied by airway constriction. We conclude that central command plays a minor role in the airway dilator response to exercise.
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Randomized Controlled Trial Clinical Trial
Apnea and periodic breathing in bed-sharing and solitary sleeping infants.
Mother-infant bed sharing, compared with the solitary sleeping condition, has recently been associated with several physiological and behavioral effects. Because the physiological effects of bed sharing may also include respiratory changes, we compared the incidence of central and obstructive apneas and periodic breathing in bed-sharing and solitary sleeping infants. Twenty routinely bed-sharing mother-infant pairs and fifteen routinely solitary sleeping pairs slept for 3 nights in a sleep laboratory. ⋯ In both groups, there was a significantly higher frequency of periodic breathing events on the bed-sharing night than on the solitary night. These findings demonstrate that the bed-sharing environment can have a significant impact on respiratory control in the infant. Evidence is also presented to suggest that routine bed sharing may result in subtle neurophysiological and/or developmental differences in infants.