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Carbon Dioxide Tension (carbon + dioxide_tension)
Selected AbstractsThe influence of exercise on foot perfusion in diabetesDIABETIC MEDICINE, Issue 10 2007D. T. Williams Abstract Aims, Diabetic foot disease is associated with both macro- and microvascular disease. Exercise has both positive and negative effects on the perfusion of lower limbs with peripheral arterial occlusive disease (PAOD). We aimed to measure changes in foot perfusion following a brief period of lower-limb exercise in individuals with and without Type 2 diabetes and non-critical PAOD. Methods, Subjects were allocated to groups according to the presence or absence of diabetes, PAOD on colour duplex imaging and clinically detectable peripheral neuropaÍthy. Transcutaneous oxygen tension (TcPO2), transcutaneous carbon dioxide tension (TcPCO2), ankle-brachial pressure indices, toe pressures and toe-brachial pressure indices (TBI) were measured. Results, One hundred and sixteen limbs were studied in 61 subjects. Post-exercise, toe pressure and TBI increased in the non-diabetic group with arterial disease, but not in the groups with diabetes. Foot TcPO2 values increased in groups with diabetes and TcPCO2 decreased in all groups with arterial disease. Increased chest TcPO2 and decreased TcPCO2 were demonstrated in the groups with diabetes. Conclusions, Elevations in foot TcPO2 and reductions in TcPCO2 indicate improved cutaneous perfusion response to local heating post-exercise. Elevated toe pressures in the non-diabetes group suggest that improved perfusion may be associated with enhanced lower limb macrovascular haemodynamics. However, improvements in TcPO2 and TcPCO2 at foot and chest sites in diabetes imply a global change in cutaneous perfusion. The results suggest that brief exercise results in an improvement in cutaneous perfusion in non-critical PAOD, particularly in individuals with diabetes. [source] A study of the effect of a resistive heat moisture exchanger (trachinaze) on pulmonary function and blood gas tensions in patients who have undergone a laryngectomy: A randomized control trial of 50 patients studied over a 6-month periodHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 5 2003Andrew Simpson Jones MD Abstract Background. Previous work from this department has shown that resistive tracheostomy filters increase the partial pressure of oxygen in capillary blood and also provide a significant amount of heat/moisture exchange. Until now it has not been shown whether there is any long-term beneficial effect and in particular whether raised tissue oxygenation is maintained using a practical filter device. Methods. We carried out a 6-month randomized control trial including 50 laryngectomees. Twenty-five patients were treated with the Liverpool Heat Moisture Exchange device incorporating an airway resistor (Trachinaze). Another 25 patients were treated with a placebo device. Relevant subjective and objective data were collected before and at the end of the study. The objective measurements were capillary oxygen tension (which parallels blood arterial tension), carbon dioxide tension, FEV1, FVC, and PIF. Patients were reviewed at intervals throughout the study. Data were analyzed using the Mann,Whitney U test and the paired t test to test the difference between the active device and placebo at 6 months. Results. Subjective lower airway parameters, including cough, number of chest infections, mucus production, and shortness of breath at rest, were significantly improved in the active group compared with the placebo group. The objective parameters FEV1, FVC, and PIF were not significantly different. Capillary oxygen tension, however, was highly significantly raised in the active group at 6 months. Conclusions. Trachinaze is highly superior to placebo at improving subjective pulmonary parameters, including shortness of breath. It is also superior in its ability to maintain an increased peripheral tissue oxygen tension over a 6-month period. © 2003 Wiley Periodicals, Inc. Head Neck 25: 000,000, 2003 [source] Regional cerebral blood flow responses to hyperventilation during sevoflurane anaesthesia studied with PETACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2010L. SCHLÜNZEN Background: Arterial carbon dioxide tension (PaCO2) is an important factor controlling cerebral blood flow (CBF) in neurosurgical patients. It is still unclear whether the hypocapnia-induced decrease in CBF is a general effect on the brain or rather linked to specific brain regions. We evaluated the effects of hyperventilation on regional cerebral blood flow (rCBF) in healthy volunteers during sevoflurane anaesthesia measured with positron emission tomography (PET). Methods: Eight human volunteers were anaesthetized with sevoflurane 1 MAC, while exposed to hyperventilation. During 1 MAC sevoflurane at normocapnia and 1 MAC sevoflurane at hypocapnia, one H215O scan was performed. Statistical parametric maps and conventional regions of interest analysis were used for estimating rCBF differences. Results: Cardiovascular parameters were maintained constant over time. During hyperventilation, the mean PaCO2 was decreased from 5.5 ± 0.7 to 3.8 ± 0.9 kPa. Total CBF decreased during the hypocapnic state by 44%. PET revealed wide variations in CBF between regions. The greatest values of vascular responses during hypocapnia were observed in the thalamus, medial occipitotemporal gyrus, cerebellum, precuneus, putamen and insula regions. The lowest values were observed in the superior parietal lobe, middle and inferior frontal gyrus, middle and inferior temporal gyrus and precentral gyrus. No increases in rCBF were observed. Conclusions: This study reports highly localized and specific changes in rCBF during hyperventilation in sevoflurane anaesthesia, with the most pronounced decreases in the sub cortical grey matter. Such regional heterogeneity of the cerebral vascular response should be considered in the assessment of cerebral perfusion reserve during hypocapnia. [source] Clinical evaluation of a valveless non-absorber breathing system in spontaneously breathing canine patientsJOURNAL OF SMALL ANIMAL PRACTICE, Issue 5 2000D. J. Holden A valveless non-absorber breathing system novel to veterinary anaesthesia is described. The performance of this system was evaluated in 35 anaesthetised spontaneously breathing dogs weighing between 2,1 and 56 kg. Fresh gas flows were reduced incrementally until rebreathing (defined as an increase in end-Inspired carbon dioxide tension above 0.2 per cent) started to occur, as measured by capnography. A significant relationship (P<0.0001) between critical fresh gas flow and bodyweight was determined, and a mean critical fresh gas flow rate of 145 ±21 ml/kg/minute was derived for 15 dogs weighing 10 kg or less (mean 6.7 ±2.6 kg) and one of 98 ±16 ml/kg/minute for the remaining 20 dogs weighing 11 kg or greater (mean 30.2 ±13.9 kg). The fresh gas requirements for each group were found to differ significantly (P<0.0001), although the correlation between critical fresh gas flow and bodyweight was not Significant (P=0.054) in the dogs weighing 10 kg or less. It is suggested that the system may prove an economical and useful addition to the breathing systems currently used in canine anaesthesia. [source] Arterial oxygen tension increase 2,3 h after hyperbaric oxygen therapy: a prospective observational studyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 1 2007B. Ratzenhofer-Komenda Background:, Inhalation of hyperbaric oxygen (HBO) has been reported to decrease arterial oxygen tension (PaO2) in the early period after exposure. The current investigation aimed at evaluating whether and to what extent arterial blood gases were affected in mechanically ventilated intensive care patients within 6 h after HBO treatment. Methods:, Arterial blood gases were measured in 11 ventilated subjects [nine males, two females, synchronized intermittent mandatory ventilation (SIMV) mode] undergoing HBO therapy for necrotizing soft tissue infection (seven patients), burn injury (two patients), crush injury (one patient) and major abdominal surgery (one patient). Blood gases were obtained with the patients in the supine position under continuous analgesia and sedation before the hyperbaric session (baseline), during isopression, after decompression, after each transport, and 1, 2, 3 and 6 h after exposure. Heart rates and blood pressures were recorded. Intensive care unit (ICU) ventilator settings remained unchanged. Transport and chamber ventilator settings were adjusted to baseline with maintenance of tidal volumes and positive end-expiratory pressure (PEEP) levels. The hyperbaric protocol consisted of 222.9 kPa (2.2 absolute atmospheres) and a 50-min isopression phase. The paired Wilcoxon's test was used. Results:, Major findings (median values, 25%/75% quantiles) as per cent change of baseline: PaO2 values decreased by 19.7% (7.0/31.7, P < 0.01) after 1 h and were elevated over baseline by 9.3% (1.5/13.7, P < 0.05) after 3 h. SaO2, alveolar-arterial oxygen tension difference and PaO2/FiO2 ratio behaved concomitantly. Acid-base status and carbon dioxide tension were unaffected. Conclusion:, Arterial oxygen tension declines transiently after HBO and subsequently improves over baseline in intensive care patients on volume-controlled mechanical ventilation. The effectiveness of other ventilation modes or a standardized recruitment manoeuvre has yet to be evaluated. [source] Prevention and management of brain edema in patients with acute liver failureLIVER TRANSPLANTATION, Issue S2 2008Fin Stolze Larsen Key Points 1Intracranial pressure is the pressure exerted by the cranial contents on the dural envelope and consists of the partial pressures of the brain, blood, and cerebrospinal fluid. 2Severe cases of acute liver failure are frequently complicated by brain edema (due to cytotoxic edema) and an increase in cerebral blood flow while the cerebrospinal fluid volume remains constant. 3The development of intracranial hypertension in patients with acute liver failure may be controlled by manipulation of the position, body temperature, plasma tonicity, arterial carbon dioxide tension, and arterial pressure. 4If intracranial hypertension evolves despite these first-tier interventions, increased sedation, induction of hypothermia (body temperature of 33°C to 34°C), and the use of anti-inflammatory drugs may help secure brain viability. Liver Transpl 14:S90,S96, 2008. © 2008 AASLD. [source] Respiratory muscle strength and muscle endurance are not affected by acute metabolic acidemiaCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2009Tessa A. C. Nizet Summary Respiratory muscle fatigue in asthma and chronic obstructive lung disease (COPD) contributes to respiratory failure with hypercapnia, and subsequent respiratory acidosis. Therapeutic induction of acute metabolic acidosis further increases the respiratory drive and, therefore, may diminish ventilatory failure and hypercapnia. On the other hand, it is known that acute metabolic acidosis can also negatively affect (respiratory) muscle function and, therefore, could lead to a deterioration of respiratory failure. Moreover, we reasoned that the impact of metabolic acidosis on respiratory muscle strength and respiratory muscle endurance could be more pronounced in COPD patients as compared to asthma patients and healthy subjects, due to already impaired respiratory muscle function. In this study, the effect of metabolic acidosis was studied on peripheral muscle strength, peripheral muscle endurance, airway resistance, and on arterial carbon dioxide tension (PaCO2). Acute metabolic acidosis was induced by administration of ammonium chloride (NH4Cl). The effect of metabolic acidosis was studied on inspiratory and expiratory muscle strength and on respiratory muscle endurance. Effects were studied in a randomized, placebo-controlled cross-over design in 15 healthy subjects (4 male; age 33·2 ± 11·5 years; FEV1 108·3 ± 16·2% predicted), 14 asthma patients (5 male; age 48·1 ± 16·1 years; FEV1 101·6 ± 15·3% predicted), and 15 moderate to severe COPD patients (9 male; age 62·8 ± 6·8 years; FEV1 50·0 ± 11·8% predicted). An acute metabolic acidemia of BE ,3·1 mmol.L,1 was induced. Acute metabolic acidemia did not significantly affect strength or endurance of respiratory and peripheral muscles, respectively. In all subjects airway resistance was significantly decreased after induction of metabolic acidemia (mean difference ,0·1 kPa.sec.L,1 [95%-CI: ,0·1 ,,0·02]. In COPD patients PaCO2 was significantly lowered during metabolic acidemia (mean difference ,1·73 mmHg [,3·0 ,,0·08]. In healthy subjects and in asthma patients no such effect was found. Acute metabolic acidemia did not significantly decrease respiratory or peripheral muscle strength, respectively muscle endurance in nomal subjects, asthma, or COPD patients. Metabolic acidemia significantly decreased airway resistance in asthma and COPD patients, as well as in healthy subjects. Moreover, acute metabolic acidemia slightly improved blood gas values in COPD patients. The results suggest that stimulation of ventilation in respiratory failure, by induction of metabolic acidemia will not lead to deterioration of the respiratory failure. [source] Is Helicobacter pylori a True Microaerophile?HELICOBACTER, Issue 4 2006Stephanie Bury-Moné Abstract Background:, There is no general consensus about the specific oxygen and carbon dioxide requirements of the human pathogen Helicobacter pylori. This bacterium is considered a microaerophile and consequently, it is grown under atmospheres at oxygen tensions 5,19% and carbon dioxide tensions 5,10%, both for clinical and basic and applied research purposes. The current study compared the growth of H. pylori in vitro, under various gas atmospheres, and determined some specific changes in the physiology of bacteria grown under different oxygen partial pressures. Methods:, Measurements of bacterial growth under various conditions were carried out employing classical solid and liquid culture techniques. Enzymatic activities were measured using spectrophotometric assays. Results:,H. pylori and all the other Helicobacter spp. tested had an absolute requirement for elevated carbon dioxide concentrations in the growth atmosphere. In contrast with other Helicobacter spp., H. pylori can tolerate elevated oxygen tensions when grown at high bacterial concentrations. Under 5% CO2, the bacterium showed similar growth in liquid cultures under oxygen tensions from microaerobic (< 5%) to fully aerobic (21%) at cell densities higher than 5 × 105 cfu/ml for media supplemented with horse serum and 5 × 107 cfu/ml for media supplemented with ,-cyclodextrin. Evidence that changes occurred in the physiology of H. pylori was obtained by comparing the activities of ferredoxin:NADH (nicotinamide adenine dinucleotide) oxidoreductases of bacteria grown under microaerobic and aerobic atmospheres. Conclusions:,H. pylori is a capnophile able to grow equally well in vitro under microaerobic or aerobic conditions at high bacterial concentrations, and behaved like oxygen-sensitive microaerophiles at low cell densities. Some characteristics of H. pylori cells grown in vitro under microaerobic conditions appeared to mimic better the physiology of organisms grown in their natural niche in the human stomach. [source] | ||||||||||