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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pattern of change in ventilatory variables after inhalation of pure N2 for two breaths was studied in normal children and adults. In six subjects the trends of change were compared to the ventilatory response to transient hypercapnia. We observed differences in the patterns of increasing ventilation with an initial abrupt increase of tidal volume for transient hypoxia and a progressive change for hypercapnia. In both cases respiratory frequency was progressively but unsystematically enhanced. A highly significant positive correlation was demonstrated between individual sensitivities to CO2 and O2, with a greater response to hypercapnia (5.6 time) than to hypoxia. Finally, a very short-latency decrease in expiratory duration occurred in the first breath after inhalation of hypercapnic mixture, supporting the recent data of Cunningham et al. (1977).
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PMID:Pattern of the ventilatory response to transient hypoxia in man: differences from transient hypercapnic test. 9 21

We report two cases of patients with Von Recklinghausen disease. They exhibited typical cutaneous and diffuse intrapulmonary lesions accompanied by effort dyspnea. Multiple radiological abnormalities were noticed and the pictures showed nodular and interstitial lesions as well as emphysematous areas. Pulmonary function tests revealed more or less marked hypoxemia without hypercapnia, and decreased maximal expiratory flows due, at least in part, to a loss of elastic recoil.
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PMID:[Von Recklinghausen's disease: functional pulmonary changes. 2 case reports]. 9 31

The experiments on 18 guinea pigs were divided into two groups and each group was arranged in such a way that the effect of hypercapnia (generated by breathing 10% CO2-90% O2) was investigated with and without inhibition of carbonic anhydrase by methazolamide, 25 mg/kg, in the first group and acetazolamide, 50 mg/kg, in the second group, administered intravenously. The endocochlear potentials (EP) and endocochlear PO2 were recorded by microelectrodes introduced into the scala media, and cochlear microphonics (CM) were monitored by a silver-wire electrode from the round window. In the first exposure to hypercapnia (20-40 min) EP increased about + 6 mV. At the same time CM decreased; the reason for this is not yet known. During the second period of hypercapnia (80-100 min) when carbonic anhydrase was inhibited with methazolamide and acetazolamide, EP did not elevate as during the first period when carbonic anhydrase was not inhibited. In this work, under specific conditions, it was observed for the first time that carbonic anhydrase affects the generation of EP.
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PMID:Carbonic anhydrase in the generation of cochlear potentials. 10 17

In a group of 21 cats, the middle cerebral artery pressure (MCAP) was recorded by means of a catheter introduced into the artery at its origin, just distal to the occlusion. The effects of hypertension, hypercapnia, and hypocapnia were studied. In a group of five cats, both middle cerebral arteries (MCA) were catherized and the pressure was recorded simultaneously on both sides. In another group of five cats, O2 tension measurements were made with the aid of oxygen electrodes in the brain tissue, the occluded MCA, and the common carotid artery. Some of the results obtained in this study are compared with the results of a previous study where monkeys were used as experimental animals.
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PMID:Haemodynamic changes in the cerebral circulation of the cat during occlusion of the middle cerebral artery. 10 Oct 24

Thirteen years' experience with home oxygen for patients with advanced chronic obstructive pulmonary disease are reviewed. Home oxygen is safe and relieves pulmonary hypertension and elevated RBC mass in some, but not all patients. Marked clinical improvement is the most important result of long-term home oxygen use, including reduced hospitalizations and return to gainful employment for a few patients. Chronic compensated carbon dioxide retention is well tolerated and adaptive in cases of severe chronic airflow obstruction. New oxygen concentrators are effective in correcting hypoxemia and may make home oxygen administration more convenient and less expensive.
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PMID:Outpatient oxygen therapy in chronic obstructive pulmonary disease. A review of 13 years' experience and an evaluation of modes of therapy. 10 79

A specific and quantitative immunological method for the determination of human erythrocyte carbonic anhydrase (HCA) isoenzyme B has been used to determine the contents of enzyme in the erythrocytes from healthy persons and from subjects with chronic obstructive lung disease. The investigations have shown a statistically significant increase of HCA type B in the erythrocytes of subjects suffering from chronic obstructive lung disease and hypercapnia. Subjects with chronic obstructive lung disease and normal PaCO2 showed no difference from normal subjects. No correlation was found between PaCO2 and human erythrocyte carbonic anhydrase.
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PMID:Carbonic anhydrase isoenzyme B in erythrocytes of subjects with chronic obstructive lung disease. 10 3

It is accepted that in hypercapnia the rise in cerebrospinal fluid bicarbonate concentration (CSF [HCO3-]) occurs because of local HCO3--generating mechanisms, dependent on carbonic anhydrase, as well as on diffusion of HCO3- from plasma. To investigate further the regulation of CSF [HCO3-], CSF HCO3- formation was studied under conditions of pure isocapnic CSF "metabolic" acidosis. In anesthetized normocapnic dogs CSF [HCO3-] was lowered to approximately 15 mmol/l by perfusing the brain ventricles with a low HCO3- solution for 45 min. In dogs with normal plasma [HCO3-], CSF [HCO3-] rose by approximately 7 mmol/l in 2 h after the end of the perfusion. Lowering plasma [HCO3-] to 10 mmol/l by infusing HCl, limited the CSF [HCO3-] rise to 2 mmol/l, indicating the importance of plasma HCO3- for the restoration of CSF [HCO3-]. The small and persistent rise of CSF [HCO3-] at low plasma [HCO3-] occurred against a concentration gradient with blood. Intraventricular injection of acetazolamide had no further effect on this small rise. It is concluded that under the conditions of our experiments the CSF [HCO3-] rise is significantly dependent on plasma [HCO3-] and the caronic anhydrase-dependent HCO3- generation in the CNS is less important.
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PMID:Restoration of CSF [HCO3-] after its experimental lowering in normocapnic conditions. 11 88

A technique is described for the production of subarachnoid haemorrhage in baboons and their subsequent recovery for chronic study of cerebrovascular reactivity. The baboons make complete neurological recoveries but the response of their cerebral circulation to hypercapnia is impaired one week later. Baseline values of cerebral blood flow and of cerebral oxygen consumption are unaffected at this time. There is no evidence of hypoxic brain damage.
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PMID:Delayed effects of subarachnoid haemorrhage on cerebral metabolism and the cerebrovascular response to hypercapnia in the primate. 11 80

The effects of elevated plasma CO2 partial pressure (PCO2) and [HCO3-] on cerebrospinal fluid (CSF) HCO3- accession have been reviewed in the context of the basal route of CSF HCO3- formation. The basal rate of 53 mM/h appears to be a consequence entirely of formation, via the reaction CO2 + OH- leads to HCO3-. Two-thirds of this rate is catalyzed by carbonic anhydrase, and the remainder uncatalyzed. The HCO3- accession matches 37% that of sodium, so that the HCO3- rate is involved with CSF turnover. When PCO2 is elevated twofold, the rate of HCO3- formation increase 10%, and results in elevation of CSF [HCO3-] by 5 mM in 1 h. Also, when plasma [HCO3-] is elevated 15 mM, CSF [HCO3-] rises about 5 mM/h; this is transfer of HCO3- "as such" by diffusion from plasma. The effects of hypercapnia and metabolic alkalosis on CSF HCO3- accumulation are additive, but they occur by separate processes. The effect of hypercapnia is an exaltation of the normal process due to increased substrate (CO2), but that of increased plasma HCO3- is due to imposition of an abnormal diffusion gradient for this ion between plasma and CSF. The effect of hypercapnia in elevating brain HCO3- operates to maintain brain pH and is also based on the formation of HCO3- from CO2. Brain HCO3- may also be a source of CSF HCO3-. Relations have been sought between the chemically calculated rates of HCO3- formation in CSF and those observed. The chemically calculated catalytic rate is 1,600 times greater than that observed, agreeing with the fact that more than 99.9% of choroid plexus carbonic anhydrase must be inhibited to yield a decrease in fluid formation or ion transport from plasma to CSF. The calculated uncatalyzed rate agrees closely with what is observed after complete inhibition of the enzyme. These considerations support the idea that all the HCO3- reaching the CSF is formed from CO2, rather than by transfer of the ion from plasma to CSF.
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PMID:Effect of varying CO2 equilibria on rates of HCO3- formation in cerebrospinal fluid. 11 42

Ten healthy subjects were tested for their peripheral respiratory chemosensitivities by the withdrawal technique two times on separate days. Hypoxic hypercapnia of PET, O2 75, 65 AND 55 mmHg with PET, CO2, 5 mmHg higher than the control level was replaced by 100% O2 two times with spontaneous respiration. Then, breath-by-breath depression calculated in minute ventilation (delta V) was observed during the period 5-20 sec after the first O2 inhalation. The results were analyzed by the linear relationship between PET, O2 and 1n delta V, and PaO2 and 1n delta V. Delta V at P02 50 mmHg, delta V50, was 9.09 +/- 6.81 liters/min (mean +/- SD) in PET, O2-1n delta V analysis and 9.22 +/- 7.46 liters/min in PaO2-1n delta V analysis, respectively. The averaged day to day variation of delta V50 expressed by SE in % was 5.3% in PET, O2-1n delta V analysis and 11.5% in PaO2-1n delta V analysis, respectively.
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PMID:A quantitative evaluation for peripheral respiratory chemosensitivities by the withdrawal test in man. 12 Apr 62


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