Search results for "partial pressure"
showing 10 items of 145 documents
Quantification of Regional Intrapulmonary Oxygen Partial Pressure Evolution during Apnea by 3He MRI
1999
We present a new method to determine in vivo the temporal evolution of intrapulmonary oxygen concentrations by functional lung imaging with hyperpolarized (3)Helium ((3)He-->). Single-breath, single-bolus visualization of (3)He--> administered to the airspaces is used to analyze nuclear spin relaxation caused by the local oxygen partial pressure p(O(2))(t). We model the dynamics of hyperpolarization in the lung by rate equations. Based hereupon, a double acquisition technique is presented to separate depolarization by RF pulses and oxygen induced relaxation. It permits the determination of p(O(2)) with a high accuracy of up to 3% with simultaneous flip angle calibration using no additional …
High-frequency oscillatory ventilation and an interventional lung assist device to treat hypoxaemia and hypercapnia
2004
A male patient accidentally aspirated paraffin oil when performing as a fire-eater. Severe acute respiratory distress syndrome ( P a 2 / F 2 ratio 10.7 kPa) developed within 24 h. Conventional pressure-controlled ventilation (PCV) with high airway pressures and low tidal volumes failed to improve oxygenation. Hypercapnia ( P a 2 12 kPa) with severe acidosis (pH<7.20) ensued. Treatment with high-frequency oscillatory ventilation (HFOV) and a higher adjusted airway pressure (35 cm H2O) improved the P a 2 / F 2 ratio within 1 h from 10.7 to 22.9 kPa, but the hypercapnia and acidosis continued. Stepwise reduction of the mean airway pressure (26 cm H2O), and oscillating frequencies (3.5 Hz), as …
Predicting hypoxia in cystic fibrosis patients during exposure to high altitudes
2006
Abstract Background For patients with cystic fibrosis (CF)-related partial respiratory insufficiency and reduced arterial oxygen tension at ground level, the mild hypobaric environment on commercial jet aircraft poses the risk of severe hypoxemia. Thus, physicians should be able to estimate the extent of in-flight hypoxia. Objectives To derive tools for estimating the expected drop in arterial oxygen partial pressure (paO 2 ) and oxygen saturation (saO 2 ) in young adult CF patients with mild to moderate airway obstruction during exposure to the hypobaric conditions aboard commercial aircraft and to test the predictive power of a hypobaric chamber simulation. Methods Blood gases of 12 CF pa…
Performance of EasyBreath Decathlon Snorkeling mask for delivering continuous positive airway pressure
2021
AbstractDuring the COVID-19 pandemic, the need for noninvasive respiratory support devices has dramatically increased, sometimes exceeding hospital capacity. The full-face Decathlon snorkeling mask, EasyBreath (EB mask), has been adapted to deliver continuous positive airway pressure (CPAP) as an emergency respiratory interface. We aimed to assess the performance of this modified EB mask and to test its use during different gas mixture supplies. CPAP set at 5, 10, and 15 cmH2O was delivered to 10 healthy volunteers with a high-flow system generator set at 40, 80, and 120 L min−1 and with a turbine-driven ventilator during both spontaneous and loaded (resistor) breathing. Inspiratory CO2 par…
Human Corticotropin-Releasing Hormone in Man: Dose-Response of Minute Ventilation and End-Tidal Partial Pressures of Carbon Dioxide and Oxygen*
1987
The respiratory stimulant properties of iv injections of 33, 67, and 100 micrograms synthetic human corticotropin-releasing hormone (hCRH) were studied in 12 normal men in a single blind, placebo-controlled trial. All doses of hCRH induced a respiratory stimulation in every subject, and the stimulation was dose dependent. The onset of respiratory stimulation occurred within 15-30 sec after hCRH infusion was started. Initially, there was an increase in tidal volume (VT), followed by an increase in respiratory rate. The maximum minute ventilation (VE) occurred 60-120 sec after starting the injection. The 33-micrograms hCRH dose induced a 35% increase in VE from 6.3 +/- 0.6 (+/- SD) to 9.7 +/-…
Application of C1-Esterase Inhibitor During Reperfusion of Ischemic Myocardium
2001
Background—Complement activation during reperfusion of ischemic myocardium augments myocardial injury, and complement inhibition with C1-esterase inhibitor (C1-INH) at the time of reperfusion exerts marked cardioprotective effects in experimental studies. Application of C1-INH in newborns, however, was recently reported to have dangerous and even lethal side effects. This study addresses the essential role of dosage in studies using C1-INH.Methods and Results—Cardioprotection by C1-INH was examined in a pig model with 60 minutes of coronary occlusion followed by 120 minutes of reperfusion. C1-INH was administered intravenously 5 to 10 minutes before coronary reperfusion without heparin at a…
Arterial and mixed venous blood gas status during apnoea of intubation--proof of the Christiansen-Douglas-Haldane effect in vivo.
1989
The Christiansen-Douglas-Haldane effect, in short the Haldane effect, describes the dependence of the CO2 binding of blood on the degree of oxygenation of haemoglobin. Under the physiological conditions of an ‘open’ system between blood and alveoli the partial pressure of arterial C02 (PaCO2), must be less than that of mixed venous blood (P[Formula: see text]CO2). During the unphysiological conditions of a ‘closed’ system, e.g. hyperoxic apnoea, i.e. continuous oxygen uptake without CO2 delivery by the lungs, the Paco2 will not only approximate the P[Formula: see text]CO2 but will even exceed it. Without the Haldane effect, rapid adjustment of Paco2 to P[Formula: see text]CO2 would be expe…
Une méthode rapide et simple pour l'estimation de la position de la courbe de dissociation de l'oxyhémoglobine
1989
The methods currently available for assessing the oxyhaemoglobin dissociation curve parameters are expensive, lengthy, require a large volume of blood, and the results obtained are modified by anaesthetic gases. The equipment required for the method described includes: a microtonometre, microcuvettes, 3 gas bottles containing different oxygen, carbon dioxide and nitrogen mixtures (4.5%, 5.6%, 89.9%; 3.5%, 5.6%, 90.9%; 2.5%, 5.6%, 91.9% respectively), a microxymetre, and a micropHmetre. The samples in the microcuvettes are incubated at 37 degrees C in a gas flow of 45 ml.min-1 from the bottles. SO2 is then read using the microxymetre. P50, i.e. PO2 at 50% saturation, is calculated, as well a…
Stable bioenergetic status despite substantial changes in blood flow and tissue oxygenation in a rat tumour.
1994
Experiments on s.c. rat tumours (DS sarcoma) were performed to determine whether chronic or acute changes in tumour perfusion necessarily lead to changes in tissue oxygenation and bioenergetic status since, as a rule, blood flow is thought to be the ultimate determinant of the tumour bioenergetic status. Based on this study, there is clear experimental evidence that growth-related or acute (following i.v. administration of tumour necrosis factor alpha) decreases in tumour blood flow are accompanied by parallel alterations in tissue oxygenation. In contrast, tumour energy status remains stable as long as flow values do not fall below 0.4-0.5 ml g-1 min-1, and provided that glucose as the mai…
Acute changes of systemic parameters in tumour-bearing rats, and of tumour glucose, lactate, and ATP levels upon local hyperthermia and/or hyperglyca…
1991
Arterial blood pressure and relevant parameters of the arterial blood (O2 and CO2 tensions, pH, haematocrit, serum electrolytes and osmolality) were determined in tumour-bearing rats upon local hyperthermia (HT) and/or hyperglycaemia (HG). Tumour heating was performed in a saline bath (44 degrees C) for 120 min; hyperglycaemia was induced by i.v. infusion of 40% glucose solution for 150 min [blood glucose levels: 35-40 mM during heating; total amount of glucose: 1.19 g/100 g body wt.; infusion rates: 0.31 ml (100 g body wt.)-1 min-1 for 2 min, 0.02 ml (100 g body wt.)-1 min-1 for 88 min, and 0.01 ml (100 g body wt.)-1 min-1 for 60 min]. Immediately after treatment, glucose, lactate and ATP …