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Query: UMLS:C0729233 (Thoracic)
 6,478 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The goal of this study was to determine whether hypoxia alters expression of endothelial nitric oxide synthase (eNOS) in the systemic circulation. Rats breathed either air or 10% oxygen for 12 hours, 48 hours, or 7 days. Thoracic aortas were excised and either mounted in organ bath myographs or frozen in liquid nitrogen for later extraction of protein and RNA. eNOS protein (Western blotting) was decreased (20% of normoxic control) after 12 hours, 48 hours, and 7 days of hypoxia. eNOS mRNA (ribonuclease protection assay) was similarly reduced. Acetylcholine (10(-4) mol/L) reversed phenylephrine (10(-5) mol/L) preconstriction by 53.3+/-5.6% in aortic rings from normoxic rats and 26.1+/-4.8% in rings from rats exposed to hypoxia for 48 hours (P<0.05), with comparable impairment of relaxation by the calcium ionophore A23187 (10(-5) mol/L). Responses to diethylamine nitric oxide and 8-bromo-cGMP were unaffected. Aortic cGMP levels after incubation with acetylcholine (10(-6) mol/L) averaged 14.0+/-1.8 fmol/mg in rings from normoxic rats compared with 8.7+/-1.0 fmol/mg in rings from hypoxic rats (P<0. 05). Similarly, nitrate concentration (by capillary electrophoresis) in the media in which the rings were incubated was reduced in the hypoxic group (5.6+/-0.23 micromol/L for hypoxic rats and 7.8+/-0.7 micromol/L for normoxic rats). Impaired endothelial NO release may handicap the vascular responses that defend vital organ function during hypoxia.
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PMID:Downregulation of endothelial nitric oxide synthase in rat aorta after prolonged hypoxia in vivo. 1074 3

In general, based on the above studies of the effects of supplemental oxygen on reducing mortality and improving sleep and exercise function in certain patient groups, patients whose disease is stable on a full medical regimen with PaO2 < or = 55 mm Hg (SaO2 < or = 88%) should be considered for LTOT. Patients with PaO2 of 55-59 mm Hg with signs of tissue hypoxemia (i.e., cor pulmonale, polycythemia, impaired cognition) should also be considered for LTOT. Oxygen therapy should also be considered for those who desaturate during sleep or exercise. These guidelines have been adopted by Medicare as reimbursement criteria and have also been endorsed by the American Thoracic Society. Indications for LTOT endorsed by the American Thoracic Society and published in the "Standards for the Diagnosis and Care of Patients with COPD" are shown in Table 6. More research is required to investigate the use of supplemental oxygen in patients who suffer nocturnal desaturation but do not have signs of end organ dysfunction, those who have an improvement in dyspnea with supplemental oxygen, and in normoxemic patients with impaired exercise performance who improve while inspiring supplemental oxygen.
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PMID:Effects of long-term oxygen therapy on mortality and morbidity. 1077 86

The purpose of this study was to determine the frequency of hypoxemia and pulmonary mineralization using 99mTc-methylene diphosphonate (99mTc-MDP) in dogs with pituitary-dependent hyperadrenocorticism (PDH). Twenty-one dogs with PDH were prospectively evaluated using thoracic radiography, arterial blood gas analysis, and bone phase and pulmonary perfusion scintigraphy (using 99mTc-macro-aggregated albumin [99mTc-MAA]). The radiographs and bone and perfusion studies were evaluated subjectively. An averaged quantitative count density ratio was calculated between the thorax and cranial thoraco-lumbar vertebrae from lateral thoracic 99mTc-MDP images. Thoracic:vertebral ratios were calculated using 99mTc-MDP studies from 21 control dogs. The thoracic:vertebral ratios were compared between the 2 groups (PDH and control). The mean age (+/-SD) of the 21 PDH dogs was 10.2 (+/-3) years, whereas the mean age of the control group was 9.8 (+/-3) years. Seven of the 21 dogs with PDH were hypoxemic (defined as an arterial partial pressure of oxygen [PaO2] < 80 mm Hg) with an average PaO2 (+/-SD) of 62 (+/-15) mm Hg. Of the 7 hypoxemic dogs, 2 were found to have pulmonary mineralization based on bone scintigraphic images. Pulmonary perfusion abnormalities were not identified using 99mTc-MAA in any of the 21 PDH dogs. Six PDH dogs had an abnormal interstitial pulmonary pattern and 5 of these dogs were hypoxemic. The average quantitative thoracic:vertebral ratio was not significantly different between the PDH and control dogs (0.5 +/- 0.4 versus 0.4 +/- 0.1, P = .16). Causes of hypoxemia other than pulmonary thromboembolism should be considered in dogs with PDH. Pulmonary mineralization may contribute to hypoxemia in dogs with PDH.
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PMID:Frequency of pulmonary mineralization and hypoxemia in 21 dogs with pituitary-dependent hyperadrenocorticism. 1077 86

The objectives of this study were to evaluate the reliability and accuracy of a new impedance cardiograph device, the Physio Flow, at rest and during a steady-state dynamic leg exercise (work intensity ranging from 10 to 50 W) performed in the supine position. We compared cardiac output determined simultaneously by two methods, the Physio Flow (QcPF) and the direct Fick (QcFick) methods. Forty patients referred for right cardiac catheterisation, 14 with sleep apnoea syndrome and 26 with chronic obstructive pulmonary disease, took part in this study. The subjects' oxygen consumption values ranged from 0.14 to 1.19 l x min(-1). The mean difference between the two methods (QcFick - QcPF) was 0.04 l x min(-1) at rest and 0.29 l x min(-1) during exercise. The limits of agreement, defined as mean difference +/- 2SD, were -1.34, +1.41 l x min(-1)] at rest and -2.34, +2.92 l x min(-1) during exercise. The difference between the two methods exceeded 20% in only 2.5% of the cases at rest, and 9.3% of the cases during exercise. Thoracic hyperinflation did not alter QcPF. We conclude that the Physio Flow provides a clinically acceptable and non-invasive evaluation of cardiac output under these conditions. This new impedance cardiograph device deserves further study using other populations and situations.
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PMID:A new impedance cardiograph device for the non-invasive evaluation of cardiac output at rest and during exercise: comparison with the "direct" Fick method. 1095 74

An audit was undertaken to assess the compliance to British Thoracic Society guidelines (1997) in the prescription of long-term oxygen treatment (LTOT) in Bassetlaw District General Hospital. A total of 34 patients were prescribed LTOT in our hospital between March 1993 and October 1998. The average age of patients was 71 years, 31 patients had COPD and three had chronic asthma. Only ten patients were clinically stable at the time of assessment. None of the measurements were repeated after a period of three weeks before prescribing LTOT. Adherence to guidelines in the prescription of LTOT was poor in our audit.
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PMID:Audit on prescription of long-term oxygen treatment. 1118 27

Thoracic organ transplantation is an effective form of treatment for end-stage heart and lung disease. Despite major advances in the field, transplant patients remain at risk for acute allograft dysfunction, a major cause of early and late mortality. The most common causes of allograft failure include primary graft failure secondary to inadequate heart and lung preservation during cold storage, cellular rejection, and various donor-recipient-related factors. During cold storage and early reperfusion, heart and lung allografts are vulnerable to intracellular calcium overload, acidosis, cell swelling, injury mediated by reactive oxygen species, and the inflammatory response. Brain death itself is associated with a reduction in myocardial contractility, and recipient-related factors such as preexisting pulmonary hypertension can lead to acute right heart failure and the pulmonary reimplantation response. The development of new methods to prevent or treat these various causes of acute graft failure could lead to a marked improvement in short- and long-term survival of patients undergoing thoracic organ transplantation.
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PMID:Acute allograft failure in thoracic organ transplantation. 1122 70

Despite publication of several management guidelines for COPD, relatively little is known about standards of care in clinical practice. Data were collected on the management of 1400 cases of acute admission with Chronic Obstructive Pulmonary Disease in 38 UK hospitals to compare clinical practice against the recommended British Thoracic Society standards. Variation in the process of care between the different centres was analysed and a comparison of the management by respiratory specialists and nonrespiratory specialists made. There were large variations between centres for many of the variables studied. A forced expiratory volume in one second measurement was found in only 53% of cases. Of the investigations recommended in the acute management arterial blood gases were performed in 79% (interhospital range 40-100%) of admissions and oxygen was formally prescribed in only 64% (range 9-94%). Of those cases with acidosis and hypercapnia 35% had no further blood gas analysis and only 13% received ventilatory support. Long-term management was also deficient with 246 cases known to be severely hypoxic on admission yet two-thirds had no confirmation that oxygen levels had returned to levels above the requirements for long-term oxygen therapy. Only 30% of current smokers had cessation advice documented. To conclude, the median standards of care observed fell below those recommended by the guidelines. The lowest levels of performance were for patients not under the respiratory specialists, but specialists also have room for improvement. The substantial variation in the process of care between hospitals is strong evidence that it is possible for other centres with poorer performance to improve their levels of care.
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PMID:Audit of acute admissions of COPD: standards of care and management in the hospital setting. 1140 9

The aim of the present study was to compare the evolution of pulmonary haemodynamics and of arterial blood gases in chronic obstructive pulmonary disease (COPD) patients with mild-to-moderate hypoxaemia, with or without sleep-related oxygen desaturation. COPD patients with daytime arterial oxygen partial pressure in the range 56-69 mmHg were included prospectively. Sleep-related oxygen desaturation was defined as spending > or = 30% of the nocturnal recording time with arterial oxygen saturation <90%. From the 64 patients included, 35 were desaturators (group 1) and 29 were nondesaturators (group 2). At baseline (t0), patients with sleep-related desaturation had a significantly higher daytime (mean +/- SD) arterial carbon dioxide partial pressure (Pa,CO2) (44.9 +/- 4.9 mmHg versus 41.0 +/- 4.1 mmHg, p=0.001) whereas mean pulmonary artery pressure (mPAP) was similar in the two groups. After 2 yrs (t2) of follow-up, 22 desaturators and 14 nondesaturators could be re-evaluated, including pulmonary haemodynamic measurements. None of the nondesaturator patients became desaturators at t2. The difference between the two groups in terms of daytime Pa,CO2 was still present at t2. The mean changes in mPAP from t0 to t2 were similar between the two groups, as were the rates of death or requirement for long-term oxygen therapy (American Thoracic Society criteria) during follow-up of up to 6 yrs. The presence of sleep-related oxygen desaturation is not a transitional state before the worsening of daytime arterial blood gases, but is a characteristic of some chronic obstructive pulmonary disease patients who have a higher daytime arterial carbon dioxide partial pressure. Such isolated nocturnal hypoxaemia or sleep-related worsening of moderate daytime hypoxaemia does not appear to favour the development of pulmonary hypertension, nor to lead to worsening of daytime blood gases.
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PMID:Outcome of COPD patients with mild daytime hypoxaemia with or without sleep-related oxygen desaturation. 1148 15

In the Netherlands, domiciliary oxygen therapy is regularly prescribed incorrectly and thus inefficiently, and the policies surrounding this therapy are inconsistent. This applies particularly to patients with chronic hypoxaemia due to chronic obstructive pulmonary disease (COPD). In order to establish a scientific basis for a uniform prescription policy, guidelines have been developed under the auspices of the Dutch Thoracic Society with the support of the Dutch Institute for Health Care Improvement. Based on scientific research, recommendations have been formulated for the indications and aims of domiciliary oxygen therapy and long-term oxygen therapy (LTOT). The most important recommendations (summarised on the back of an oxygen application form) are: domiciliary oxygen therapy is only indicated for severe hypoxaemia by day at rest; if domiciliary oxygen therapy was prescribed following recovery from an acute exacerbation or hospitalisation, the arterial oxygen tension should be rechecked within three months of starting oxygen therapy; prescription of LTOT is only justified in case of an optimal (non-)medical regimen, clinical stability, and chronic hypoxaemia, and providing a number of preconditions, such as smoking cessation (partly due to the fire hazard), have been met; LTOT is a lifelong therapy that should be prescribed for at least 15, and preferably 24, hours per day, and the oxygen flow rate settings for rest, exertion and sleep should be adjusted to meet the patient's needs; for ambulatory patients, the prescribing physician should consider the portability of the oxygen equipment; as patient education and supervision are essential to secure the success of LTOT, the prescribing physician should cooperate with the general practitioner, the district nurse and the oxygen supplier in this respect.
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PMID:[CBO guideline 'Oxygen therapy at home']. 1184 72

The objective of this study was to determine the frequency and severity of decreased arterial oxy-hemoglobin saturation during exercise in adults with cystic fibrosis at 1,500 m above sea level. A convenience sample of 50 adults with cystic fibrosis who did not have hypoxemia (oxygen saturation, < 90%) at rest were evaluated. Spirometry was performed according to American Thoracic Society standards, and maximal exercise tests were performed on an electronically braked cycle ergometer using a ramp protocol individualized for each patient. Pulse oximetry was measured every 2 min. When exercising at high altitude, 45 of 50 patients had a decrease in arterial oxy-hemoglobin saturation from baseline to some degree. In 29 patients, oxy-hemoglobin saturation fell below 90%; in 14 patients, it fell below 85%; and in 4 patients, it fell below 80%. Oxy-hemoglobin saturation decreased to < 90% in 12 of 14 patients with severe pulmonary disease (FEV(1) < 40% predicted), in 15 of 26 patients with moderate disease (40% less than or equal to FEV(1) < 70% predicted), in 2 of 6 patients with mild disease (70% less than or equal to FEV(1) < 90% predicted), and in 0 of 4 with normal pulmonary function (FEV(1) greater than or equal to 90%). Percent predicted FEV(1) (r = 0.57; P < 0.0001) and FEV(1)/FVC ratio (r = 0.52; P < 0.0001) most highly correlated with arterial oxy-hemoglobin saturation at peak exercise. We conclude that at 1,500 m above sea level, adult CF patients with obstructive airways disease are at significant risk for decreased arterial oxy-hemoglobin saturation during exercise. A supervised exercise test should be considered prior to recommending an exercise program for such patients.
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PMID:Oxygen saturation in adult cystic fibrosis patients during exercise at high altitude. 1174 46


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