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Biomedical subjects

C C Christensen

Publications and source records attributed to C C Christensen.

At least 19 recordsLinked to original sources
PubMed2005

Hypoxaemia in chronic obstructive pulmonary disease patients during a commercial flight.

The aim of the study was to investigate hypoxaemia in chronic obstructive pulmonary disease patients during a commercial flight. The effect of a commercial flight, lasting 5 h 40 min, on arterial blood gas levels and symptoms in 18 chronic obstructive pulmonary disease patients with a pre-flight percutaneous oxygen saturation of 94% and self-reported ability to walk 50 m without severe dyspnoea was studied. The arterial oxygen tension (Pa,O2) decreased from sea level to cruising altitude (10.3+/-1.2 versus 8.6+/-0.8 kPa), but, thereafter, except for one patient, remained stable throughout the flight. During light exercise, however, there was further desaturation (percutaneous oxygen saturation 90+/-4 versus 87+/-4%). After 4 h, a decrease in arterial carbon dioxide tension (5.0+/-0.4 versus 4.8+/-0.4 kPa) and an increase in cardiac frequency (87+/-13 versus 95+/-13 beats x min(-1)) were observed. A pre-flight Pa,O2 of >9.3 kPa did not secure an acceptable in-flight Pa,O2. Aerobic capacity showed the strongest correlation with in-flight Pa,O2. In conclusion, following an initial decrease in arterial oxygen tension, chronic obstructive pulmonary disease patients in a stable state of their disease seem to maintain a stable arterial oxygen tension throughout a flight of intermediate duration, except when walking along the aisle. However, a decrease in arterial carbon dioxide tension, indicating compensatory hyperventilation, could imply a risk of respiratory fatigue during longer flights.

Aerospace Medicine↗
PubMed2004

Effect of exercise mode on oxygen uptake and blood gases in COPD patients.

Patients with chronic obstructive pulmonary disease (COPD) are characterised by decreased exercise tolerance, and, more variably, exercise induced hypoxaemia (EIH). Evaluation of physical work capacity and physiological responses to exercise may be performed by various procedures, but there are diverging opinions as to which exercise test should be preferred. In the current study, oxygen uptake and arterial blood gases in COPD patients have been compared during submaximal and maximal exercise on treadmill and ergometer bicycle. Treadmill exercise resulted in higher peak oxygen uptake than bicycle exercise (1111+/-235 vs. 987+/-167 ml min(-1), P<0.02), while the plasma lactate levels were higher during cycling (1.8+/-0.8 vs. 3.8+/-1.7 mmol l(-1), P<0.001). Neither carbon dioxide output, ventilation, nor rate of perceived exertion (Borg RPE scale) showed significant differences between the two modes of exercise. The EIH during both maximal (delta Sa,O2 = -5.6+/-4.2 vs. -3.4+/-5.1%) and sub-maximal exercise was more pronounced during treadmill walking than during cycling. The present study indicates that the VO2peak in COPD patients is higher, the maximal lactate concentrations lower and the development of EIH more pronounced when exercise testing is performed on a treadmill than on a bicycle ergometer.

Adult↗
PubMed2004

Relationship between exercise desaturation and pulmonary haemodynamics in COPD patients.

Pulmonary hypertension (PH) in patients with chronic obstructive pulmonary disease (COPD) has traditionally been explained as an effect of hypoxaemia. Recently, other mechanisms, such as arterial remodelling caused by inflammation, have been suggested. The aim of this study was to investigate whether exercise-induced PH (EIPH) could occur without concurrent hypoxaemia, and whether exercise-induced hypoxaemia (EIH) was regularly accompanied by increased pulmonary artery pressure or pulmonary vascular resistance index (PVRI). Pulmonary haemodynamics in 17 patients with COPD of varying severity, but with no or mild hypoxaemia at rest, were examined during exercise equivalent to the activities of daily living (ADL) and exhaustion. EIPH occurred in 65% of the patients during ADL exercise. Pulmonary arterial pressure during exercise was negatively correlated with arterial oxygen tension, but EIPH was not invariably accompanied by hypoxaemia. Conversely, EIPH was not found in all patients with EIH. The resting PVRI was negatively correlated with arterial oxygen tension during ADL exercise, but an elevated PVRI without EIH occurred in 35% of the patients. In conclusion, exercise-induced pulmonary hypertension occurred during exercise equivalent to the activities of daily living in chronic obstructive pulmonary disease patients with no or mild hypoxaemia at rest. Although pulmonary artery pressure and arterial oxygen tension were negatively correlated during exercise, a consistent relationship between hypoxaemia and pulmonary hypertension could not be demonstrated. This may indicate that mechanisms other than hypoxaemia contribute significantly in the development of pulmonary hypertension in these patients.

Activities of Daily Living↗
PubMed2002

Effect of hypobaric hypoxia on blood gases in patients with restrictive lung disease.

Several publications have reported effects of hypobaric conditions in patients with chronic obstructive pulmonary disease. To the current authors' knowledge, similar studies concerning patients with restrictive lung disease have not been published. The effect of simulated air travel in a hypobaric chamber on arterial blood gases, blood pressure, and cardiac frequency during rest and 20 W exercise, and the response to supplementary oxygen in 17 patients with chronic restrictive ventilatory impairment has been investigated. Resting oxygen tension in arterial blood (Pa,O2) decreased from 10.4+/-1.6 kPa at sea level to 6.5+/-1.1 kPa at 2,438 m simulated altitude, and decreased further during light exercise in all patients (5.1+/-0.9 kPa). Pa,O2 at this altitude correlated positively with sea-level Pa,O2 and transfer factor of the lung for carbon monoxide (TL,CO), and negatively with carbon dioxide tension in arterial blood (Pa,CO2). Pa,O2 increased to acceptable levels with an O2 supply of 2 L x min(-1) at rest and 4 L x min(-1) during 20 W exercise. In conclusion, most of the patients with restrictive ventilatory impairment developed hypoxaemia below the recommended levels of in-flight oxygen tension in arterial blood during simulated air travel. Light exercise aggravated the hypoxaemia. Acceptable levels of oxygen tension in arterial blood, with only a minor increase in carbon dioxide tension in arterial blood, were obtained by supplementary oxygen.

Adult↗
PubMed2000

Development of severe hypoxaemia in chronic obstructive pulmonary disease patients at 2,438 m (8,000 ft) altitude.

The arterial oxygen tensions (Pa,02) in chronic obstructive pulmonary disease (COPD) patients travelling by air, should, according to two different guidelines, not be lower than 7.3 kPa (55 mmHg) and 6.7 kPa (50 mmHg), respectively, at a cabin pressure altitude of 2,438 m (8,000 ft). These minimum in-flight Pa,O2 values are claimed to correspond to a minimum Pa,O2 of 9.3 kPa (70 mmHg) at sea-level. The authors have tested whether this limit is a safe criterion for predicting severe in-flight hypoxaemia. The authors measured arterial blood gases at sea-level, at 2,438 m and at 3,048 m (10,000 ft) in an altitude chamber at rest and during light exercise in 15 COPD patients with forced expiratory volume in one second (FEV1) <50% of predicted, and with sea-level Pa,O2 >9.3 kPa. Resting Pa,O2 decreased below 7.3 kPa and 6.7 kPa in 53% and 33% of the patients, respectively, at 2,438 m, and in 86% and 66% of the patients at 3,048 m. During light exercise, Pa,O2 dropped below 6.7 kPa in 86% of the patients at 2,438 m, and in 100% of the patients at 3,048 m. There was no correlation between Pa,O2 at 2,438 m and pre-flight values of Pa,O2, FEV1 or transfer factor of the lung for carbon monoxide. In contrast to current medical guidelines, it has been found that resting arterial oxygen tension >9.3 kPa at sea-level does not exclude development of severe hypoxaemia in chronic obstructive pulmonary disease patients travelling by air. Light exercise, equivalent to slow walking along the aisle, may provoke a pronounced aggravation of the hypoxaemia.

Aged↗
PubMed1999

Hemodynamic and neuroendocrine effects for candoxatril and frusemide in mild stable chronic heart failure.

OBJECTIVES: The study aimed to assess the hemodynamic and neuroendocrine effects of candoxatril and frusemide compared with placebo in patients with mild chronic heart failure. BACKGROUND: Candoxatril is an atriopeptidase inhibitor. It increases circulating levels of atrial natriuretic peptide leading to natriuresis and diuresis, which alleviate the symptoms of a failing heart. METHODS: This was a multicenter, randomized, double-blind study. Forty-seven patients with mild stable chronic heart failure received candoxatril 400 mg/day, frusemide 40 mg/day or placebo for up to six weeks. Cardiac indices were determined at rest and during exercise, and blood samples were taken for laboratory analysis. Assessments were performed at baseline (day 0) and after six weeks (day 42). RESULTS: In comparison with placebo, both drugs significantly reduced mean pulmonary capillary wedge pressure following the first dose administration. Only candoxatril significantly reduced pulmonary capillary wedge pressure during exercise on day 0, while both drugs significantly reduced this parameter on day 42. Changes in the remaining hemodynamic parameters were comparable for both drugs relative to placebo. Frusemide significantly increased mean plasma renin activity (days 0 and 42), and the mean aldosterone concentration (day 42) in comparison with placebo, whereas candoxatril caused no significant changes in any of the hormonal parameters assessed. CONCLUSIONS: These results show that candoxatril, 400 mg/day, has a similar hemodynamic profile to frusemide, 40 mg/day, but it does not induce adverse neuroendocrine effects. Candoxatril therefore appears to offer a clinically significant advantage over frusemide, providing an alternative therapeutic approach to the treatment of patients with mild stable chronic heart failure.

Adolescent↗
PubMed1998

[Medical problems among airline passengers].

Worldwide, there are more than one billion air travelers each year. Flying in a modern jet airliner is a safe, efficient and relatively comfortable mode of transport, although a few susceptible passengers may be adversely affected by environmental and physiological stresses like pressure change, reduced level of oxygen, dry air, immobility due to cramped seating, noise, vibration and turbulence, in addition to stressful airports. This article describes these factors and their medical implications and includes some practical medical advice to travellers. Reported inflight illness and injuries in two major Scandinavian airlines 1993-97 are presented.

Aerospace Medicine↗
PubMed1993

[Invasive or transcutaneous measurements of oxygen saturation and blood gases? An evaluation of pulse oximetry and transcutaneous measurement of PO2 and PCO2 during rest and exercise].

Arterial and transcutaneous measurements of the oxygen saturation (SO2), the partial pressure of oxygen (PO2) and the partial pressure of carbon dioxide (PCO2 were compared during rest before and after cycling, and during submaximal and maximal exercise, in 12 adult patients with cystic fibrosis. SO2 was measured non-invasively using two different pulse oximeters (Radiometer and Ohmeda, respectively) and PO2 and PCO2 were registered with a transcutaneous electrode (Radiometer). The coefficients of correlation between arterial and transcutaneous values were respectively 0.95 (Radiometer) and 0.85 (Ohmeda) for SO2, 0.77 for PO2, and 0.75 for PCO2. On average the differences between arterial and transcutaneous values were small, but varied by 3-4% (2SD) for SO2, 2.0 kPa for PO2 and 1.0 kPa for PCO2. Our results indicate that pulse oximetry is a reasonably good way of detecting severe arterial hypoxemia during work, whereas the transcutaneous measurements of PO2 and PCO2 show such large variations that this method cannot be recommended for clinical use.

Adult↗
PubMed1993

Collagen alterations in chronically sun-damaged human skin.

The major histological characteristic of sun-damaged skin is the accumulation of an elastotic material that appears to replace collagen. This elastotic material consists primarily of elastin and histological studies suggest a large loss of collagen in the dermis of chronically sun-damaged skin. In this study, we examine the content and distribution of collagen and procollagen in sun-damaged human skin. The total collagen content of sun-damaged skin was 20% less than nonsolar-exposed skin (524 micrograms collagen per mg total protein in sun-damaged skin and 667 micrograms collagen per mg total protein in nonsolar-exposed skin). In addition, there was a 40% decrease in the content of intact amino propeptide moiety of type III procollagen in sun-damaged skin (0.68 U per 50 mg wet weight) as compared to nonsolar-exposed skin (1.12 U per 50 mg wet weight). The data suggest that this change in collagen content is due to increased degradation. The distribution of collagen in sun-damaged skin was examined by indirect immunofluorescence. Mild digestion of sun-damaged skin with elastase removed the elastin and revealed the presence of collagen in the elastotic material. Therefore, the elastin appears to mask the presence of collagen fibers in the dermis of sun-damaged skin.

Aged↗
PubMed1992

Lung function and radiographic signs of pulmonary fibrosis in oil exposed workers in a cable manufacturing company: a follow up study.

Thirty seven workers employed for at least three years in oil impregnation of cables during 1963-83 were followed up in 1990 to study the development of pulmonary fibrosis and consequences for lung function. They had been exposed to concentrations of mineral oil vapours of 50-100 mg/m3, and concentrations of oil mist of 0.5-1.5 mg/m3. All 29 living persons were traced. For each person one control matched for age, height, and smoking habits was selected. Among 25 workers followed up with radiographic studies, 10 cases of pulmonary fibrosis were found, by contrast with one case in the control group (p less than 0.01). Chest radiographs from 1979-80 and 1989-90 were reviewed. The profusion of small opacities increased in seven of 16 persons during 10 years without exposure. Seventeen workers had lung function tests. The bellows function (VC, FEV1, MVV) and lung volumes (TLC, RV) did not differ from those in the matched controls (p greater than 0.05), but the carbon monoxide transfer factor (TLCO) was decreased. The largest reduction of TLCO (1.5 mmol/kPa/min) was found among workers exposed for 10 years or more (p less than 0.05). Arterial blood gases were not affected at rest, but during maximum tread mill exercise, PO2 and HbO2 were reduced in exposed workers compared with controls, particularly among those exposed for at least 10 years (p less than 0.05). Exposure to low viscosity oil mist and vapour is the most plausible cause of the fibrosis. Unaffected bellows function, reduced TLCO, and decreased arterial blood oxygen during exercise is compatible with peribronchiolar fibrosis.

Adult↗
PubMed1992

Rabid bat diagnosed in Hawaii.

Since 1966, the Hawaii State Government has been conducting Fluorescent Rabies Antibody (FRA) testing on animal brains as part of a statewide rabies-surveillance program. On April 3, 1991, the Department of Health (DoH) laboratory diagnosed the first case of rabies detected in the State. A large brown bat, Eptesicus fuscus fuscus, captured in a transport container that had just been off-loaded from a ship at Honolulu harbor, was caught. It's brain was examined and showed typical fluorescent staining patterns for rabies virus. The USPHS Centers For Disease Control (CDC) rabies laboratory confirmed the diagnosis 2 days later. The successful interception of this rabid animal was the result of close cooperation between the private sector (Sea Land Service, Hawaiian Stevedores) and the Hawaii State Government Departments of Health and of Agriculture.

Animals↗
PubMed1991

Matching three classifications of secondary students to differential levels of study guides.

This study examined the effectiveness of matching three classifications of secondary students (17 with learning disabilities, 18 remedial, and 47 nondisabled) to differential levels of study guides. The students, 45 males and 37 females, were enrolled in science and social studies classes in middle school and high school. In one treatment, students were assigned multilevel study guides containing different levels of referential cues, with the guides implemented through three instructional groups: teacher-directed, dyadic, and independent. In another treatment, the same students were assigned single-level study guides that did not contain referential cues, with the guides implemented as an independent activity. An equivalent time samples design was arranged, with six multilevel and six single-level treatments randomly assigned in two-session blocks. The dependent measures consisted of two types of test items, factual and interpretive. The results of group analyses indicated that multilevel study guides were more effective than single-level study guides in all classes and overall on factual questions, with individual analyses verifying that the greatest benefit occurred for the teacher-directed students. On interpretive test items, the results of group analyses favored the multilevel study guides in high school social studies and overall, with individual analyses revealing few remarkable differences for students in any instructional group. A trend analysis revealed little practice effect over time in either treatment. Several methodological and clinical issues involved in matching heterogeneous students to differential levels of textbook instruction in secondary programs are discussed.

Achievement↗
PubMed1990

Doxazosin in combination with atenolol in essential hypertension: a double-blind placebo-controlled multicentre trial.

Doxazosin (mean dose 11 mg) given once daily in combination with 100 mg atenolol (n = 44) was compared with placebo and atenolol (n = 43) in a double-blind, multicenter study in patients with mild to moderate essential hypertension. In the atenolol/doxazosin-treated group, standing blood pressure significantly decreased by 17.0/12.3 mm Hg compared to 6.2/6.7 mm Hg in the atenolol/placebo group whereas supine blood pressure decreased by 13.2/9.8 mm Hg and 9.2/6.0 mm Hg, respectively in the two groups. Serum lipids did not change significantly in either group. The majority of side-effects reported were mild and transient. This study confirms that doxazosin may be safely combined with a beta-blocker. Doxazosin proved to be well tolerated and effective in patients with blood pressure refractory to atenolol alone.

Adolescent↗
PubMed1990

The response of the light reflex of retinal vessels to reduced blood pressure in hypertensive patients.

The response of retinal arteries and veins to 3 months of antihypertensive medication was studied in 10 patients (39-56 years old) with essential hypertension. We used computerized microdensitometry on fundus photographs, a technique allowing for objective and simultaneous measures of the caliber of blood columns and the width and intensity of their central 'light reflex'. A moderate lowering of diastolic and systolic blood pressures (P less than 0.001) resulted in a significant reduction in the intensity of reflection from retinal arteries (38.6%; P less than 0.005). An increase in the width of the blood column (2.8%; n.s.) and the reflex (8.6%; n.s.) was indicated. Traditionally, changes in light reflectivity has been associated with arteriosclerosis of the vessel wall. The study shows, however, that the vascular reflex is most sensitive to changes in the systemic blood pressure. This signals a need for critical reviewal of interpretation and usefulness of classical grading systems of ophthalmoscopic signs of hypertensive retinopathy.

Adult↗
PubMed1988

Changes in coronary haemodynamics and myocardial metabolism at rest and during exercise after a cardiotonic drug (prenalterol) in patients with coronary artery disease.

To elucidate the myocardial metabolic and haemodynamic effects of an inotropic drug in patients with coronary artery disease (CAD) without evident congestive heart failure (CHF), the acute effects of prenalterol were studied in nine patients. Patients with documented CAD by leftsided cardioangiography and end-diastolic pressure greater than 15 mm Hg were included in the study. They were examined at rest and during supine exercise at a level just below their anginal threshold before and after prenalterol. At rest, rate pressure product (RPP) increased by 40% (P less than 0.01), cardiac index rose 20% (P less than 0.01), cardiac venous flow (CVF) increased by 18% (P less than 0.05), and myocardial oxygen consumption (MVO2) increased by 20% (P less than 0.05) after prenalterol administration. Despite a decrease in mean pulmonary capillary venous pressure (PCV) of 40% (P less than 0.01), myocardial lactate extraction fell significantly (P less than 0.01) and lactate production was observed in three of nine patients compared to before prenalterol administration. During exercise, RPP increased by 20% (P less than 0.01), cardiac index remained unchanged, CVF increased by 25% (NS) and MVO2 showed a tendency to an increase (NS) after prenalterol administration. Mean PCV pressure decreased by 30% (P less than 0.01). Myocardial lactate extraction was markedly reduced during exercise (P less than 0.01) and five of nine patients showed lactate production compared to that before prenalterol administration. Thus, despite a decrease in left ventricular filling pressure, increased myocardial oxygen demand occurred after acute administration of prenalterol. Prenalterol and probably similar inotropic drugs should be used cautiously in patients with CAD without clinical evidence of congestive heart failure.

Catheterization, Swan-Ganz↗
PubMed1986

Mutation and enhanced virus transformation of cultured hamster cells by exposure to gaseous ethylene oxide.

Ethylene oxide is a classical mutagen and a carcinogen based on evidence from studies in experimental animals. It is widely distributed in industrial, research, hospital, and food environments. In an effort to explore the use of newly developed methods for exposing mammalian cells to gaseous or volatile mutagens/carcinogens, Chinese hamster V79 cells were treated for 2 hr with gaseous ethylene oxide, in sealed treatment chambers, and assayed for survival and mutagenic response by analysis of induced resistance to 6-thioguanine or ouabain. Significant numbers of mutants were produced at both genetic markers by 1,250-7,500 ppm ethylene oxide. Similarly, primary Syrian hamster embryo cells were treated for 2 or 20 hr with gaseous ethylene oxide in sealed treatment chambers and subsequently assayed for survival and increased sensitivity to SA7 virus transformation. Treatment concentrations extended from toxic to several nontoxic concentrations. After 2-hr ethylene oxide treatment at 625-2,500 ppm a significant enhancement of virus transformation was observed. At 20 hr after treatment no enhancement was observed. Treatment of hamster cells with ethylene oxide in both bioassay systems yielded concentration-related, quantitative results.

Adenoviruses, Simian↗