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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Effects of moderate hypercapnia (10% CO2) on rectal temperature, oxygen consumption and body weight loss were examined during and after acute hypothermia induced by cold and helium-oxygen. 2. Hypothermia induction time was reduced significantly by hypercapnia. Rewarming tended to be faster in hypercapnic animals than in normocapnic animals. 3. Hypercapnia significantly reduced body weight loss when measured during hypothermia and during normothermia after rewarming. 4. Oxygen consumption during cooling was decreased by hypercapnia. 5. Exposure to 10% CO2 during cooling may spare energy substrate and favor survival in hypothermia.
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PMID:Effects of moderate hypercapnia on hypothermia induced by cold He-O2 in rats. 809 75

To investigate the effects of digitalis on chemoreflexes in humans, we measured muscle sympathetic nerve activity (microneurography), minute ventilation, oxygen saturation, end-tidal carbon dioxide, mean arterial pressure, heart rate, and central venous pressure during stimulation of peripheral chemoreceptors with hypoxia, during stimulation of central chemoreceptors with hypercapnia, and during a cold pressor test before and after digitalis and placebo in 10 healthy volunteers on two different days (randomized, double-blind, cross-over design). Digitalis did not affect baseline measurements significantly. Despite similar changes in oxygen saturation and end-tidal carbon dioxide during hypoxia and hypercapnia with both placebo and digitalis, digitalis significantly potentiated overall ventilatory responses to hypoxia (+67 +/- 12% before versus +98 +/- 3% after digitalis; mean +/- SEM; P < .01) but did not affect the response to hypercapnia. Sympathetic nerve activity increased by 25 +/- 9% during hypoxia before digitalis and 30 +/- 10% during hypoxia after digitalis (P = NS) and increased by 38 +/- 18% during hypercapnia before digitalis and 26 +/- 11% during hypercapnia after digitalis (P = NS). Digitalis did not significantly change responses to the cold pressor test. Placebo had no effect on ventilatory and sympathetic nerve activity responses. We conclude that digitalis selectively augments ventilatory responses to peripheral chemoreceptor stimulation by hypoxia.
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PMID:Differential effects of digitalis on chemoreflex responses in humans. 812 54

We investigated in conscious rats the characteristics and modes of action of CO2 on thermoregulation and ventilatory control during cold stress. In a group of 10 rats studied intact and after carotid body denervation, measurements of metabolic rate (VO2), ventilation (V), shivering, and colonic temperature (Tc) were made at controlled ambient temperatures (Ta) of 25, 20, 15, 10, and 5 degrees C. Animals were exposed on different days to 1) normoxia, 2) normoxia and 4% CO2, 3) 12% hypoxia, or 4) 10.8% hypoxia and 4% CO2. The following results were obtained. 1) During CO2 exposure in normoxia or hypoxia, VO2 is increased at Ta of 25 degrees C and decreased for lower Ta. These effects are partly mediated by carotid body afferents. 2) Shivering and nonshivering thermogenesis and therefore Tc regulation are affected by CO2 exposure as shown by relationships between VO2-Tc and VO2-shivering intensity. 3) V is controlled by PO2 and PCO2 directly through their peripheral and central actions but also indirectly through their effects on VO2. Our conclusions are as follows. 1) Control of Tc is markedly dependent on PCO2 level. Carotid body afferents play a role, but direct central effects acting on the different sources of thermogenesis and possibly on thermolysis are most prominent. 2) As far as control of V is concerned, during hypercapnia in normoxia or hypoxia, several analogies may be formed between exposure to cold and muscular exercise, both of which increase VO2 and V, suggesting common integrative mechanisms at the central nervous system level.
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PMID:Ventilatory and metabolic responses to cold and CO2 in intact and carotid body-denervated awake rats. 812 76

Prenatal correction of certain cardiac lesions with a poor prognosis may have advantages over postnatal repair. For this to be done, safe and effective support of the fetal circulation must be devised. Studies involving fetal cardiac bypass have demonstrated progressive fetal hypoxemia, hypercapnia, and acidosis, indicating placental dysfunction. We performed fetal cardiac bypass in 18 fetal lambs (126 to 140 days' gestation) to assess the effect of flow rate on fetal oxygenation and metabolism and function of the placenta as an in vivo oxygenator. Fetal cardiac bypass was done for a 30-minute study period at normothermia in all fetuses. During the study period the fetal aorta was cross-clamped and cold cardioplegia was administered to the heart so there was no fetal cardiac contribution to systemic output. Nine fetuses underwent studies at low flow rates (109 +/- 20 mL.kg-1.min-1) and 9 at higher flow rates (324 +/- 93 mL.kg-1.min-1). At the lower flow rate, mean aortic pressure, arterial pH, and oxygen tension decreased whereas carbon dioxide tension and lactate levels increased when compared with prebypass levels. At the higher flow rate mean aortic pressure, pH, oxygen tension, carbon dioxide tension, and lactate levels remained similar to prebypass levels during the 30-minute study period. When the animals were weaned from the bypass circuit after studies at high flow rates, arterial oxygen tension and pH decreased whereas carbon dioxide tension increased to levels similar to those in the low-flow group.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Fetal cardiac bypass: improved placental function with moderately high flow rates. 831 87

The effects of CO2 on laryngeal receptors were studied in ten anaesthetized, paralysed, artificially ventilated cats using a preparation in which the upper airway was isolated in situ and artificially ventilated. This allowed CO2 to be confined to the upper airway and enabled responses to CO2 to be recorded whilst the larynx was being ventilated under physiological conditions. Single-unit afferent activity was recorded from the superior laryngeal nerve and the pressure and thermal sensitivity of receptors determined. Carbon dioxide responses were tested by switching from upper airway ventilation with room air to mixtures containing 5 and 9% CO2 with 21% O2 in N2. Fibres were classified into two broad groups, tonic and quiescent, depending on their level of activity when the larynx was not being ventilated. All tonic fibres responded to either positive or negative pressure. Quiescent fibres were either positive or negative pressure receptors, cold receptors or had no response to pressure or cold airflow. The majority of all categories of fibres were significantly affected by CO2 in a reversible and usually concentration-dependent manner. Tonic fibres were inhibited, regardless of pressure sensitivity. Quiescent negative and positive pressure receptors were excited and inhibited respectively whilst cold receptors and fibres with no response to occlusion were excited. Laryngeal hypoxia and systemic asphyxia and hypercapnia had no effect on receptor activity. We conclude that the majority of laryngeal receptors are sensitive to CO2 and that this receptivity may be important in the control of ventilation and upper airway muscle activity.
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PMID:Carbon dioxide-sensitive superior laryngeal nerve afferents in the anaesthetized cat. 831 45

We examined changes in ventilation and metabolic rate during hypothermia (36-27 degrees C) induced with exposure to helium-oxygen and cold in halothane anesthetized ground squirrels (Spermophilus lateralis) and rats. As a consequence of proportionate decreases in VCO2 and breathing frequency, the VE/VCO2 in both species remained constant. The changes which occurred in breathing pattern were also similar in the two species; an increase in TI and TE along with emergence of apneic periods between breaths at body temperatures below 31 degrees C. VT/TI and TI/TTOT decreased but VT remained constant with progressive hypothermia. The ventilatory responses to hypercapnia and hypoxia decreased to the same extent as the ventilatory and metabolic requirements in the ground squirrel but not the rat. The changes in VE and VCO2 during hypothermia in the ground squirrel predicted well the values observed in deep hibernation. We conclude that regulation of ventilation at reduced body temperatures is tightly coupled to metabolic demand.
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PMID:Ventilation is coupled to metabolic demands during progressive hypothermia in rodents. 835 48

Weight loss reduces many of the health hazards associated with obesity including insulin resistance, diabetes mellitus, hypertension, dyslipidemia, sleep apnea, hypoxemia and hypercarbia, and osteoarthritis. Potential adverse effects of weight loss include a greater risk for gallstone formation and cholecystitis, excessive loss of lean body mass, water and electrolyte problems, mild liver dysfunction, and elevated uric acid levels. Less consequential problems such as diarrhea, constipation, hair loss, and cold intolerance may also occur. The short-term adverse effects are not severe enough to contraindicate weight loss, nor do they outweigh its short-term benefits.
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PMID:Short-term medical benefits and adverse effects of weight loss. 836 5

We have investigated at ambient temperatures (Tam) of 25 and 5 degrees C the effects of ambient hypoxia (Hxam; fractional inspired O2 = 0.14) and hypercapnia (fractional inspired CO2 = 0.04) on ventilation (V), O2 uptake (VO2), and colonic temperature (Tc) in 12 conscious rats before and after carotid body denervation (CBD). The rats were concomitantly exposed to CO hypoxia (HxCO; fractional inspired CO = 0.03-0.05%), which decreases arterial O2 saturation by approximately 25-40%. The results demonstrate the following. 1) At Tam of 5 degrees C, in both intact and CBD rats, V/VO2 is larger when Hxam or CO2 is associated with HxCO than with normoxia. At Tam of 25 degrees C, this is also the case except for CO2 in CBD rats. 2) At Tam of 5 degrees C, the changes in VO2 and Tc seem to result from additive effects of the separate changes induced by Hxam, CO2, and HxCO. It is concluded that, in conscious rats, central hypoxia does not depress respiratory activity. On the contrary, particularly when VO2 is augmented during a cold stress, both V/VO2 during HxCO and the ventilatory responses to Hxam and CO2 are increased. The mechanisms involved in this relative hyperventilation are likely to involve diencephalic integrative structures.
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PMID:Ventilatory and metabolic responses to ambient hypoxia or hypercapnia in rats exposed to CO hypoxia. 921 71

Fifty patients at risk for postoperative lung dysfunction and undergoing elective coronary revascularization have been randomly assigned to receive normothermic (36 degrees C) perfusion with warm heart protection (NP group) or hypothermic (28 degrees C) perfusion with cold heart protection (HP group). Lung function before and after cardiopulmonary bypass (CPB) was studied through the determination of the intrapulmonary shunt (Qs/Qt), the alveoloarterial oxygen gradient (A-a delta O2), and the artero-alveolar carbon dioxide gradient (a-A delta CO2). The Qs/Qt after CPB was significantly lower in the NP group (27.1 +/- 2.6 vs 35.7 +/- 2.3) as well as the A-a delta O2 (50.2 +/- 1.5 vs 57.6 +/- 2.4), both data returned to comparable between the groups after 3 h in the intensive care unit. The a-A delta CO2 was significantly lower after CPB in the NP group (5.2 +/- 0.74 vs 8.2 +/- 0.8). Hospital stay and mortality were comparable in the two groups; intubation time and rate of early extubation showed a trend in favour of the NP group; the rate of patients suffering hypoxia and/or hypercapnia after extubation was significantly lower in the NP group (12%) versus the HP group (44%). Normothermia seems to exert a protective effect against lung dysfunction after CPB. The absence of a rewarming injury associated with reperfusion, a limitation of the hypothermic-induced vasoconstriction due to local cooling of the lung and a better compliance of the normothermic lung are hypothesized as beneficial effects of the 'all-warm' strategy.
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PMID:Normothermic perfusion and lung function after cardiopulmonary bypass: effects in pulmonary risk patients. 930 Apr 76

Thermoregulatory, respiratory, and perceptual responses to acute CO2 exposure during light exercise (75 W) were assessed in 12 U.S. Navy divers clad only in swim trunks while immersed to the neck in water at 18 degrees and 34 degrees C. The CO2 exposures consisted of a linear 10-min ramp increase in the inspired fraction of CO2 (FICO2) from 0 to 6% followed by 5 min of breathing 6% CO2. The ability to detect and rate the severity of hypercarbia, as well as subjective changes in thermal comfort, were assessed by comparing subjective ratings given during the CO2 exposures with those given during immersion trials where the FICO2 was maintained at 0%. Hypercarbia was recognized earlier and, at a given PETCO2, was perceived to be greater during cold- than during warm-water immersions (P < 0.01). The CO2 exposures did not affect the thermal balance of divers as assessed by changes in heat flux and rectal temperature. However, increased feelings of warmth were reported during both the cold and warm immersions when breathing raised concentrations of CO2 (P < 0.01). During the cold immersions, acute exposure to 6% CO2 significantly decreased forearm blood flow (P < 0.05), but did not affect finger blood flow. It is concluded that PETCO2 levels can reach unacceptably high concentrations (> 60 mmHg) before hypercarbia can be reliably detected by working divers. Furthermore, the ability to detect hypercarbia is poorer when immersed in warm water than when in cold water.
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PMID:Physiologic and perceptual responses to hypercarbia during warm- and cold-water immersion. 956 81


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