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Inspired Oxygen Concentration (inspired + oxygen_concentration)
Selected AbstractsHigh total antioxidant activity and uric acid in tracheobronchial aspirate fluid of preterm infants during oxidative stress: an adaptive response to hyperoxia?ACTA PAEDIATRICA, Issue 3 2000G Vento The effect of O2 exposure, expressed by mean daily fractional inspired oxygen concentration (FiO2), was evaluated during the first 6 d of life in the tracheobronchial aspirate fluid of 16 mechanically ventilated preterm infants in terms of both antioxidant response and oxidative damage, by measuring total antioxidant activity, uric acid concentrations and protein carbonyl content. Each day linear regression analysis was performed and a positive correlation was found between total antioxidant activity and FiO2 during the study period, especially on day 2 of life (r= 0.91, p < 0.0001), but uric acid correlated only in the first 3 d, especially on the 2nd day (r= 0.83, p < 0.0001). No correlation was found between carbonyl content and FiO2. The highest values of total antioxidant activity (416 and 790 ,mol l,1) were found in 2 babies ventilated with highest FiO2: 1 and 0.80, respectively. Total antioxidant activity was not detectable or was very low in the babies not requiring O2 therapy. The highest value of uric acid (270 ,mol l,1) was found in the baby ventilated with 100% oxygen. Uric acid concentrations obtained in these babies were much higher then those reported in the bronchoalveolar lavage fluid of adults. Preterm babies seem to have an antioxidant response in the tracheobronchial aspirate fluid following an oxidative stress and uric acid may be physiologically important as an antioxidant of the respiratory tract, especially during the first days of life. [source] Episodes of hypoxemia during synchronized intermittent mandatory ventilation in ventilator-dependent very low birth weight infantsPEDIATRIC PULMONOLOGY, Issue 1 2005Steve R.E. Firme MD Abstract Distinct patterns of asynchrony, and episodes of hypoxemia, may occur in a spontaneously breathing preterm infant during conventional intermittent mandatory ventilation (IMV) on traditional time-cycled, pressure-limited ventilators. Synchronized IMV (SIMV) and assist/control ventilation are frequent modes of patient-triggered ventilation used with infant ventilators. The objective of this study was to use computerized pulse oximetry to quantify the occurrence of episodes of hypoxemia (oxygen desaturation) during SIMV vs. IMV, in preterm infants ,1,250 g who required mechanical ventilation at ,14 days of age. We performed a randomized, crossover study with each infant being randomized to IMV or SIMV (Infant Star ventilator) for initial testing for a 1-hr period. Patients were subsequently tested on the alternate modality after a stabilization period of 10 min at the same ventilator and fractional inspired oxygen concentration (FiO2) settings. Pulse oximetry data were obtained with a Nellcor N-200 monitor, a microcomputer, and a software program (SatMaster). An investigator blinded to the randomized assignment evaluated all measurements. Eighteen very low birth weight (VLBW) infants with a birth weight of 777,±,39 g (mean,±,SEM) and gestational age 25.1,±,0.3 weeks were studied. The average pulse oximeter oxygen saturation (SaO2) was higher on SIMV than IMV (P,<,0.01). During SIMV, these infants had significantly fewer episodes of hypoxemia (duration of episodes of oxygen desaturation as a percentage of scorable recording time) to 86,90% SaO2 (P,<,0.01), 81,85% SaO2 (P,<,0.01), and 76,80% SaO2 (P,<,0.05) when compared to IMV. There was also a significant decrease in percentage of time of desaturation to SaO2,<,90% (P,=,0.002),,<,85% SaO2 (P,=,0.003), and <80% SaO2 (P,=,0.02) during SIMV vs. IMV. Our preliminary findings indicate that the use of SIMV in a population of VLBW ventilator-dependent infants (,14 days of age) results in better oxygenation and decreased episodes of hypoxemia as compared to IMV. © 2005 Wiley-Liss, Inc. [source] An assessment of the efficiency of the Glostavent® ventilatorANAESTHESIA, Issue 8 2009T. M. Bailey Summary In parts of the world where supplies of oxygen and electricity are erratic, ventilating patients' lungs can be problematic. Should the electricity supply fail, gas driven ventilators have an advantage as they can continue functioning. However, many are extravagant in their requirement for the driving gas. The Glostavent® ventilator was designed to minimise these requirements. We measured the duration of ventilation achieved by the Glostavent ventilator using an E-size oxygen cylinder at a range of minute volumes, and the inspired oxygen concentration achieved by recycling the driving gas. The period of mechanical ventilation from a single E-size cylinder ranged from 11 h 8 min (SD 4 min) with a minute volume of 7 l.min,1 to 18 h 15 min (SD 7 min) with a minute volume of 3 l.min,1. The mean fractional inspired oxygen concentration achieved by recycling the driving gas without further inspired oxygen supplementation was 0.33. We conclude that the Glostavent ventilator performs as efficiently and cost effectively as predicted. [source] PERIOPERATIVE HIGH-DOSE OXYGEN THERAPY IN VASCULAR SURGERYANZ JOURNAL OF SURGERY, Issue 6 2007Phillip J. Puckridge Background: Patients undergoing infrainguinal bypass surgery have reduced baseline tissue oxygen tension and high rates of wound infections. The hypoxaemia worsens during surgery, potentially reducing the ability to combat bacterial lodgement. We investigated whether high-dose perioperative oxygen administration to patients undergoing infrainguinal arterial surgery results in increased tissue oxygenation. Methods: Ten consecutive patients undergoing infrainguinal arterial surgery had transcutaneous partial pressure of oxygen (TcpO2) measured preoperatively, intraoperatively after arterial clamps applied, postoperatively and at discharge. Measurements were taken with inspired oxygen concentration (FiO2) of 30% then 80%. Arterial blood gases were measured at the same times. Results: Tissue oxygenation showed no difference intraoperatively while arterial clamps were in place, but significantly higher tissue oxygenation was seen with use of high-dose oxygen (FiO2 80%) postoperatively (P < 0.05). Carbon dioxide levels in tissue increased while arterial clamps were in place (P < 0.01) and pH fell intraoperatively and following reperfusion (P < 0.05). Conclusion: The administration of high-dose oxygen to vascular surgical patients undergoing lower-limb arterial surgery results in increased tissue oxygen concentrations when perfusion is not reduced by the presence of arterial clamps. These results suggest the administration of high-dose oxygen intraoperatively may be beneficial in reducing wound infections, but further research is required. [source] Cardiac baroreflex control in humans during and immediately after brief exposure to simulated high altitudeCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2002Frédéric Roche Summary To examine the baroreflex response in humans during and immediately after acute hypoxia exposure, the cardiac baroreflex sensitivity (BRS) was studied using adaptation of RR intervals in response to spontaneous systolic blood pressure fluctuations (sequences methodology) in 11 unacclimatized subjects. All measurements were made under fixed breathing rate, and realized consecutively at baseline level (20 min), at an inspired oxygen concentration of 11% (15 min) and again under normoxic conditions (20 min; recovery period). The spontaneous baroreflex response decreases progressively during hypoxic exposure, causing a tachycardic response at this FiO2 without any significant alteration of the systolic or diastolic blood pressure. The magnitude of decrease for this variable at the end of exposure averaged 42·9 ± 15·6%. The simultaneous spectral analysis of heart rate (HR) variability in hypoxic condition confirmed an alteration in the parasympathetic activity (HFnu: ,17·8 ± 30·9% versus basal conditions, P<0·01) counterbalanced by an exaggerated sympathetic activity (LFnu: +33 ± 42·4%, P<0·05) at the sinus node. Interestingly, we could observe an enhanced cardiac baroreflex response during the period following the inhalation of the hypoxic mixture (+130·6 ± 15·6% of basal conditions, P<0·001). There is a relationship with a significant and abrupt increase in the parasympathetic control of HR (mean HR reached 111 ± 8·1% of the mean basal HR, P<0·01). These results suggest that brief exposure to hypoxia under rate-controlled ventilation is associated with a significant alteration in the spontaneous cardiac baroreflex. This important cardiac autonomic imbalance is followed by a significant increase in the cardiac parasympathetic drive even after the disappearance of the hypoxic stimulus. [source] | ||||||||||