Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Central respiratory drive responding to pH changes was eliminated by bilateral coagulation or cold block of area S (intermediate area) on the ventral medullary surface in 7 anaesthetized cats. Arterial pH, PCO2, and PO2 (4 cats) and the respiratory response to hypoxia and hypercapnia (6 cats) were observed before and after coagulation. After coagulation in hyperoxia the arterial pH dropped from 7.30 to 7.09, the arterial PCO2 was elevated from 4.80 kPa to 8.17 kPa (6 cats). Ventilation increased by 477 ml at a PCO2a of 6.58 kPa when PO2a was reduced from 39.5 kPa to 8.5 kPa before coagulation, after coagulation ventilation increased by 241 ml (4 cats). The peripheral chemoreceptors guaranteed spontaneous breathing even in hyperoxia. The data reveal that the loss of respiratory homeostasis by elimination of the S areas is due to the loss of central chemosensitive drive with concomitant reduction of peripheral chemoreceptor effect.
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PMID:Respiratory response to hypoxia and hypercapnia after elimination of central chemosensitivity. 4 38

Unanesthetized and unrestrained rats, chronically cannulated in the carotid artery, were exposed to normal air (NA) and Helox (21% O2, 79% He) at ambient temperatures (Ta) of 22 and -10 degrees C. In Helox at Ta = 22 degrees C, the Vo2 was 1.39 ml O2/g-h and the Vco2 0.98 ml CO2/g-h, 145 and 126%, respectively, of the values in NA at Ta = 22 degrees C. The arterial Pao2, Paco2, and pH were comparable in Helox and NA at Ta = 22 degrees C. In Helox at Ta = -10 degrees C, rats invariably became hypothermic after exposure of 0.75 to 1.5 h. During the induction of hypothermia the decrease of Vo2 and Vco2 was oscillatory, Pao2 and pH increased, and Paco2 decreased significatnly (P less than 0.05). Minimum Vo2 and Vco2 during hypothermia averaged 0.71 ml O2/g-h and 0.50 ml CO2/g-h, 23 and 22%, respectively, of the values in normothermic animals at Ta = -10 degrees C. Minimum body temperature during hypothermia was clamped at 21.7 +/- 0.3 degrees C (X +/- SE) by increasing Ta to 19 degrees C. When Helox was replaced by NA, hypothermic rats rewarmed spontaneously, returning to normothermia within 4 h. The data suggest that hypothermia induced by Helox plus cold does not seem to be due to respiratory failure, as systemic hypoxia or hypercapnia were not observed. The controlled hypothermia cycle reported here provides a model for dynamic studies of thermogenic mechanisms both at the normothermic and hypothermic states without the interference of drugs and other nonphysiological treatments.
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PMID:Metabolic and respiratory responses during Helox-induced hypothermia in the white rat. 24 22

The relationship between body weight (BW) and the changes in colonic temperature (deltaTc) was analyzed in newborn, adult, and old guinea pigs. No correlation could be demonstrated between BW and, deltaTc in response to cold with the exception of the 10 to 20 day-old group. In hypercapnia statistically significant or almost significant coefficient were obtained in three groups, showing--as expected--that the fall in Tc tended to decrease with increasing BW. In hypoxia a statistically significant coefficient was obtained in the young adult group, demonstrating that--contrary to expectation--the fall in Tc tended to be greater with increasing BW.
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PMID:The role of the body mass: body surface ratio in thermo-regulatory responses to cold, hypoxia, and hypercapnia in new-born, adult, and aged guinea pigs. 27 15

Most of the previous literature concerning otologic problems in compressed gas environments has emphasized middle ear barotrauma. With recent increases in commercial, military, and sport diving to deeper depths, inner ear disturbances during these exposures have been noted more frequently. Studies of inner ear physiology and pathology during diving indicate that the causes and treatment of these problems differ depending upon the phase and type of diving. Humans exposed to simulated depths of up to 305 meters without barotrauma or decompression sickness develop transient, conductive hearing losses with no audiometric evidence of cochlear dysfunction. Transient vertigo and nystagmus during diving have been noted with caloric stimulation, resulting from the unequal entry of cold water into the external auditory canals, and with asymmetric middle ear pressure equilibration during ascent and descent (alternobaric vertigo). Equilibrium disturbances noted with nitrogen narcosis, oxygen toxicity, hypercarbia, or hypoxia appear primarily related to the effects of these conditions upon the central nervous system and not to specific vestibular end-organ dysfunction. Compression of humans in helium-oxygen at depths greater than 152.4 meters results in transient symptoms of tremor, dizziness, and nausea plus decrements in postural equilibrium and psychomotor performance, the high pressure nervous syndrome. Vestibular function studies during these conditions indicate that these problems are due to central dysfunction and not to vestibular end-organ dysfunction. Persistent inner ear injuries have been noted during several phases of diving: 1) Such injuries during compression (inner ear barotrauma) have been related to round window ruptures occurring with straining, or a Valsalva's maneuver during inadequate middle ear pressure equilibration. Divers who develop cochlear and/or vestibular symptoms during shallow diving in which decompression sickness is unlikely or during compression in deeper diving, should be placed on bed rest with head elevation and avoidance of maneuvers which result in increased cerebrospinal fluid and intralabyrinthine pressure. With no improvement in symptoms after 48 hours, exploratory tympanotomy and repair of a possible labyrinthine window fistula should be considered. Recompression therapy is contraindicated in these cases...
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PMID:Diving injuries to the inner ear. 40 82

Rats with dietary potassium (K) depletion have an altered breathing pattern compared to age matched control rats. The K depleted rats also have a decreased body weight gain, basal metabolic rate and body temperature. In this study, age matched controls are underfed (UFC) to match for body weight gain and metabolic rate and controls are exposed to different ambient temperatures to alter metabolism and body temperature. Compared to UFC rats with the same body weight and basal metabolic rate the K depleted rats breathe slower and with a larger tidal volume in the basal state and in response to hypercapnia and hypoxia. With heat stress body temperature is increased in K depleted rats as is metabolic rate. While frequency is increased it is still slower than in controls at the same ambient and body temperatures. We conclude that the low metabolic rate and body temperature of K depleted rats is not the cause of the altered breathing pattern. In addition, it is shown that the hypothermia of K depletion is present only at ambient temperatures below the thermoneutral zone and that is is apparently due to an inability of the K depleted rat to increase metabolic heat production with cold stress.
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PMID:Breathing in the potassium depleted rat: the role of metabolic rate and body temperature. 50 31

Threshold temperatures for shivering in acute and chronic hypercapnia were determined in guinea pigs by measuring the time course of cervical cord temperature, skin temperature, oxygen consumption (Vo2), and electrical muscle activity during cold exposure (15 degrees C). Prior to acute exposure to CO2, the shivering threshold was determined in each animal during control conditions breathing air. With increasing CO2 concentrations (5,7.5, and 15% CO2) the shivering thresholds fell to lower temperatures, decreasing by approximately 40 degrees C at 15% CO2. The shift of the shivering threshold to lower values found during acute exposure to 15% CO2 was reversed after chronic exposure to 15% CO2 for 3 days, which marks the time of metabolic adaptation to CO2.
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PMID:Threshold temperatures for shivering in acute and chronic hypercapnia. 97 34

The control of hindlimb and renal vascular beds by vagal afferents was studied, in anesthetized spontaneously breathing rabbits in which the carotid sinus and aortic depressor nerves were cut, by measuring the increase in vascular resistance (constant-flow perfusion with autologous blood) during bilateral vagal cold block (VCB). The effect of hypercapnia was studied with both increased ventilation (caused by inspiration of mixtures of CO2 in O2) and decreased ventilation (caused by infusion of gallamine during O2 breathing). The increase in hindlimb resistance with VCB was correlated with respiratory minute volume but not with PCO2; the reverse was true for the increase in renal resistance. Without VCB the renal vessel constriction caused by the hypercapnia was markedly attenuated, provided that there were minimal respiratory movements; the resistance increased dramatically when these movements were abolished or with VCB. Thus, the powerful central effect of CO2 on the renal vessels can be counteracted by vagal afferents activated by lung movement; even minimal respiratory activity can cause this effect.
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PMID:Modification of vagal depressor reflex by CO2 in spontaneously breathing rabbits. 111 75

Bilateral lung transplantation (BLT) is a recently described procedure based on two sequential single-lung transplantations (SLT), which are performed by a transverse sternobithoracotomy. It does not require either cardiac arrest or routine use of cardiopulmonary bypass (CPB). The intraoperative management of 10 patients suffering from end-stage pulmonary disease is reported. Implantation of the first graft is quite similar to a SLT. Problems encountered during this procedure (ie, hypoxemia, hypercapnia, or low cardiac output) were due to restricted pulmonary and cardiac reserve. Preoperative and intraoperative assessment of the recipient's respiratory and cardiac status was, therefore, of prime importance. Mild preoperative pulmonary hypertension, well-preserved right ventricular function, and removal of the less well-perfused lung limited these difficulties; no patient required partial CPB at this stage. During the second lung implantation, gas exchange was provided by the first grafted lung. Measurements of pulmonary vascular resistance (PVR), venous admixture (Qva/Qt), and dead space (VD/VT) assessed with the arterial-to-end-tidal CO2 difference were used to confirm the adequacy of perfusion and V/Q matching. In one patient, partial CPB was instituted because of surgical difficulty related to inadequate size matching of the lungs. In the other patients, first graft function was satisfactory and the second graft was implanted without CPB. With chest closure, PVR returned to nearly normal values (range, 57-293, mean 167 dynes.s.cm-5) and Qva/Qt increased (range, 3 to 36, mean 20%). This limited series demonstrates that CPB is optional during this procedure. Good selection of recipients and donors, good lung preservation methods, and a short duration of cold ischemia are essential to success.
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PMID:Anesthesia for bilateral lung transplantation without cardiopulmonary bypass: initial experience and review of intraoperative problems. 149 95

1. In four awake dogs we measured EMG activity of three inspiratory and four expiratory muscles during sustained central chemoreceptor stimulation (CO2 inhalation), and peripheral chemoreceptor stimulation (intravenous infusion of almitrine bismesylate (almitrine)). By using this selective pharmacological stimulation of the peripheral chemoreceptors and reversibly cold-blocking pulmonary stretch receptors, we were able to determine the effects of each type of stimulation on respiratory muscle recruitment in the absence of such complicating influences as pulmonary stretch receptor feedback, cerebral hypoxia or hypocapnia, and differences in breathing pattern. 2. During 10 min of steady-state hyperpnoea (minute ventilation VI, approximately twice eupnoea) caused by either hypercapnia or isocapnic stimulation of the carotid bodies with almitrine, all three inspiratory and all four expiratory muscles demonstrated significant and sustained elevations in EMG activity. 3. With both types of chemoreceptor stimulation, as tidal volume, VT, increased, so did the mean electrical activities of the crural diaphragm (r = 0.88), costal diaphragm (r = 0.93), parasternals (r = 0.82), triangularis sterni (r = 0.74), transversus abdominis (r = 0.77), external obliques (r = 0.68) and internal intercostals (r = 0.75). 4. In each dog, the response of ventilation and of the diaphragmatic EMG to a given level of central or peripheral chemoreceptor stimulation is highly reproducible from one test day to the next. On the other hand, accessory inspiratory and expiratory abdominal and rib cage muscles in two of the four dogs showed highly significant changes from day to day in the amount of their EMG activity at any given VT. 5. During steady-state ventilatory stimulation, 2 min intervals were chosen during which the two types of chemoreceptor stimulation had caused hyperpnoeas with similar values for VT, total time per breath (TTOT) and inspiratory time divided by the total time (TI/TTOT). Comparison of EMG activities during these matched hyperpnoeas revealed that there were no differences in the activities of any of the muscles between the two forms of stimulation. We conclude that peripheral chemoreceptor stimulation causes significant and sustained recruitment of expiratory muscles even in the absence of pulmonary feedback and that both expiratory and inspiratory muscles are recruited to the same extent during peripheral chemoreceptor stimulation as they are during an identical hyperpnoea caused by central chemoreceptor stimulation.
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PMID:Respiratory muscle recruitment during selective central and peripheral chemoreceptor stimulation in awake dogs. 159 81

To assess the responsiveness of the cerebral vessels to chronic hypercapnia, we measured middle cerebral artery flow velocity by transcranial Doppler ultrasound in 20 normal subjects and in 14 COLD patients before and after stimulation by progressive hypercapnia (rebreathing test) or by intravenous administration of an acetazolamide bolus. The results showed no statistically significant difference in baseline flow velocity between the normal subjects and the COLD patients. The COLD patients showed a reduced cerebral vascular responsiveness to both stimuli. Cerebral blood flow is normal in chronic hypercapnia and the mechanism by which compensation is achieved leads to a decrease in cerebral vascular responsiveness.
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PMID:Cerebral vascular responsiveness in chronic hypercapnia. 162 40


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