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Query: UMLS:C0085383 (hypocapnia)
 1,697 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A marked increase in the prostaglandin E (PGE) content in the cerebrospinal fluid (CSF) and the arterial blood of cats was observed under conditions of 3-minute hypocapnia. During 30-minute hypocapnia a restoration of the initial PGE level was seen. The PGE content in CSF increased while in the arterial blood it decreased comparatively to the control under conditions of 3-minute hypercapnia. In 30-minute hypercapnia the PGE amount in the CSF and the blood dropped in comparison with 3-minute hypercapnia being below the basal level in the blood. It is suggested that in hypocapnia PGE should limit its constrictive effect on the cerebral vessels while under conditions of hypercapnia they are to promote the realization of the cerebral vessel reaction to CO2.
Biull Eksp Biol Med 1979 Sep
PMID:[Variations in prostaglandin E content in the arterial blood and cerebrospinal fluid under conditions of hypo- and hypercapnia]. 51 23

The joint response of the respiratory and panting centres of fully-conscious unidirectionally-ventilated chickens to simultaneous combinations of hyperthermia and hypo-/hypercapnia was examined. The response was monitored by changes in the rate and amplitude of movements of the body wall and gular apparatus respectively. The response to a combination of hyperthermia plus hypercapnia bore indications of a linear summation of the individual responses of the panting centre and respiratory centre to the respective thermal and chemical stimuli. A more complex response was elicited by a combination of hyperthermia plus hypocapnia. In this case the inhibition of respiratory movements induced by the hypocapnia (hypocapnic apnea) permitted a more forceful manifestation of the component of the thermoreflex which acts via the hyoid muscles and which is responsible for the synchronous 'gular flutterin'. The rate of gular fluttering increased by up to 150% as compared to normal panting. The experimental procedure therefore provided a technique for breaking the central linkage which normally constrains the rhythm of the hyoid muscles to the more dominant rhythm of the respiratory muscles.
Respir Physiol 1978 Sep
PMID:Experimentally induced antagonism of chemical and thermal reflexes in the respiratory system of fully conscious chickens. 70 90

A syndrome characterized by hypoxemia aggravated by exercise, orthodeoxia, hypocapnia, and evidence of hyperdynamic circulation, but otherwise normal indices of pulmonary air flow, volume, and distribution of ventilation has been observed as an infrequent complication of hepatic cirrhosis. An illustrative case is described, the features of which support the presence of a shunt or shunt-like mechanism consisting of low-resistance vascular communications within the lung. We suggest that this may represent the existence of a hepatopulmonary syndrome analogous to the hepatorenal syndrome.
Chest 1977 Sep
PMID:Exercise-aggravated hypoxemia and orthodeoxia in cirrhosis. 89 Dec 82

The brains of nine cats were subjected to bitemporal electric convulsive treatment. The current (AC, 220 V, 50 Hz, ca. 500 mA, 500 ms) was applied two to five times. Pial vessels were observed through a skull window. Immediately after current application, some pial arteries exhibited segmental spastic constriction which usually did not disappear until the animals were killed. Before sacrificing the animals, 20 min after convulsive treatment they were perfused with a carbon suspension. In some cortical areas blackening was impaired indicating that perfusion was not complete. Electron-microscopic investigation revealed that spasm also occurred in arterioles of the brain parenchyma. Many arterial vessels, some of them possessing only one muscular cell sheat, had collapsed so that the lumen was merely a small cleft. The spasms were irregularly distributed and confined to small segments of the vessel. Small arteriolar vessels were more affected than large pial arteries. Arterial spasms continued for 20 min. In a total of 39 control animals spastic constriction was observed only once; this animal had been subjected to prolonged hypocapnia.
Arch Psychiatr Nervenkr (1970) 1977 Sep 14
PMID:Spastic constriction of cerebral vessels after electric convulsive treatment. 93 91

Cerebral blood flow, electrical activity, and neurological function were studied in rabbits subjected to either 15 minutes of oligemia (20 torr cerebral perfusion pressure) or complete cerebral ischemia produced by cisterna magna infusion. During oligemia, flow was reduced from 68.4 +/- 4.2 ml/100 gm/min to 26.3 +/- 4.4 (p less than .01), and during ischemia animals had no proven flow. By 5 minutes after oligemia or ischemia significant symmetrical hyperemia occurred and there was no evidence of the no-reflow phenomenon. The electroencephalogram became isoelectric significantly later and returned significantly sooner in oligemia than in ischemia. Oligemic animals had earlier and better return of neurological function than their ischemic counterparts, although postinsult hypocapnia improved functional recovery in both groups. These experiments do not support the concept that oligemia is a more severe insult than complete ischemia. In intracranial hypertension produced by this model, the no-reflow phenomenon does not occur.
J Neurosurg 1975 Sep
PMID:Experimental cerebral oligemia and ischemia produced by intracranial hypertension. Part 1: Pathophysiology, electroencephalography, cerebral blood flow, blood-brain barrier, and neurological function. 115 66

We have measured force-frequency curves of the sternocleidomastoid muscle in six patients at three different levels of isoflurane anaesthesia (1.0, 1.4 and 1.8 MAC). Spontaneous ventilation was suppressed by mild hypocapnia induced by mechanical ventilation. An anterior force vector of the sternocleidomastoid muscle was measured during isometric contraction induced by supramaximal electrical stimulation at 20, 50 and 100 Hz to the i.m. accessory nerves of the muscle. The force response at 20 Hz and 50 Hz did not change with an increase in isoflurane concentration, but it decreased at 100 Hz as isoflurane concentration increased. The reduction in the force at 100 Hz may be caused mainly by impaired neuromuscular transmission.
Br J Anaesth 1992 Sep
PMID:Sternocleidomastoid muscle contractility at different levels of isoflurane anaesthesia in humans. 138 39

We conducted a retrospective analysis on 311 patients with clinical diagnosis of pulmonary embolism (PE) in a period of 3 years. 163 patients were excluded based on clinical-laboratorial criteria. The remaining 146 patients had a median age of 69 years (range: 30-91 years). 54% of the patients were male. We found dyspnea (94%), abnormal cardiopulmonary observation (89%), risk factors for venous thromboembolism (74%), tachycardia (53%), cyanosis (49%), and neck vein distension (45%) to be the most frequent findings. 64% of the patients had heart failure, 32% had myocardial ischemia, 13% had cancer, and 11% had myocardial infarction. Lactic dehydrogenase (LDH) was higher than two-fold in 54% of the patients. There was severe hypoxemia in 55% of the cases and hypocapnia in 43% of the cases. Creatinine phosphokinase (CPK) was elevated in 16% of the cases. Electrocardiography was suggestive of PE in 37% of the cases. Echocardiography showed right heart dysfunction in 30% of the cases, 92% of the patients were treated with heparin, 37 patients (25%) died, 54% of which during the first 4 days after admittance. Trying to define an index of mortality in PE we evaluated all patients by discriminant analysis coming up with 14 items with good discriminative power. By approximation of their odds-ratios we determined how many points would correspond to each item in the total sum.(ABSTRACT TRUNCATED AT 250 WORDS)
Rev Port Cardiol 1992 Sep
PMID:[Pulmonary embolism--mortality risk]. 147 67

The responses of intracranial pressure (ICP) to hyperbaric oxygen (HBO) therapy and arterial gas pressures were investigated. ICP was measured through a ventricular or spinal drainage catheter in patients with brain tumor or cerebrovascular disease. Changes in ICP, heart rate (HR), arterial blood pressure (ABP), and transcutaneous partial pressure of carbon dioxide (PtcCO2) or oxygen (PtcO2) were recorded continuously during air or 100% O2 breathing at 1 and 2.5 atmospheres absolute (ATA). HR and PtcCO2 decreased and mean ABP was unchanged during HBO inhalation. ICP was reduced at the beginning and tended to increase gradually during HBO inhalation. The change from air to O2 without altering respiratory frequency and volume caused a gradual increase of ICP and PtcCO2 with a transient ICP reduction in an artificially respirated patient. Intentionally reduced respiration to maintain PtcCO2 at the value at 2.5 ATA with air caused the ICP to return to near the value at 2.5 ATA with air even during HBO inhalation. These findings suggest that reduced ICP is initially due to direct cerebral vasoconstriction caused by hyperoxia and is maintained mainly by induced hypocapnia during HBO inhalation. Care is required when giving HBO therapy to patients with a high ICP and/or who are respirated artificially.
Neurol Med Chir (Tokyo) 1991 Sep
PMID:Intracranial pressure responses during hyperbaric oxygen therapy. 172 71

The objectives of these experiments were 1) to describe the effect of maximum treadmill exercise on gas exchange, arterial blood gases, and arterial blood oxygenation in rats acclimated for 3 wk to simulated altitude (SA, barometric pressure 370-380 Torr) and 2) to determine the contribution of acid-base changes to the changes in arterial blood oxygenation of hypoxic exercise. Maximum O2 uptake (VO2max) was measured in four groups of rats: 1) normoxic controls run in normoxia (Nx), 2) normoxic controls run in acute hypoxia [AHx inspiratory PO2 (PIO2) approximately 70 Torr], 3) SA rats run in hypoxia (3WHx, PIO2 approximately 70 Torr), and 4) SA rats run in normoxia (ANx). VO2max (ml STPD.min-1.kg-1) was 70.8 +/- 0.9 in Nx, 46.4 +/- 1.9 in AHx, 52.6 +/- 1.1 in 3WHx, and 70.0 +/- 2.4 in ANx. Exercise resulted in acidosis, hypocapnia, and elevated blood lactate in all groups. Although blood lactate increased less in 3WHx and ANx, pH was the same or lower than in Nx and AHx, reflecting the low buffer capacity of SA. In AHx and 3WHx, arterial PO2 increased with exercise; however, O2 saturation of hemoglobin in arterial blood (SaO2) decreased. In vitro measurements of the Bohr shift suggest that SaO2 decreased as a result of a decrease in hemoglobin O2 affinity. The data indicate that several features of hypoxic exercise in this model are similar to those seen in humans, with the exception of the mechanism of decrease in SaO2, which, in humans, appears to be due to incomplete alveolar-capillary equilibration.
J Appl Physiol (1985) 1991 Sep
PMID:Maximum oxygen uptake and arterial blood oxygenation during hypoxic exercise in rats. 175 99

We investigated the validity of transcranial Doppler recordings for the analysis of dynamic responses of cerebral autoregulation. We found no significant differences in percentage changes among maximal (centerline) blood flow velocity, cross-sectional mean blood flow velocity, and signal power-estimated blood flow during 24-mm Hg stepwise changes in arterial blood pressure. We investigated blood flow propagation delays in the cerebral circulation with simultaneous Doppler recordings from the middle cerebral artery and the straight sinus. The time for a stepwise decrease in blood flow to propagate through the cerebral circulation was only 200 msec. Brief (1.37-second) carotid artery compression tests also demonstrated that the volume compliance effects of the cerebral vascular bed were small, only about 2.2% of normal blood flow in 1 second. Furthermore, transients associated with inertial and volume compliance died out after 108 msec. We also investigated the hypothesis that autoregulatory responses are influenced by hyperventilation using the same brief carotid artery compressions. One second after release, the flow index increased by 17% during normocapnia and 36% during hypocapnia. After 5 seconds, the flow index demonstrated a clear oscillatory response during hypocapnia that was not seen during normocapnia. These results suggest that the intact human cerebral circulation in the absence of pharmacological influences does not function as predicted from pial vessel observations in animals.
Stroke 1991 Sep
PMID:Assessment of cerebral autoregulation dynamics from simultaneous arterial and venous transcranial Doppler recordings in humans. 153 Jul 27


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