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Biomedical subjects

O F Pedersen

Publications and source records attributed to O F Pedersen.

At least 91 records · Page 5Linked to original sources
PubMed1984

Measurements of alveolar concentrations of toluene.

The use of a photoionisationdetector (PID) for measurement of alveolar concentrations of gases and vapours was evaluated during a human exposure experiment with toluene. Two other methods, the standard gaspipette method and the gasbag /charcoal method, was tested for comparison. The best method appeared to be the PID-method. The major disadvantage in using this instrument was the missing selectivity towards individual compounds in a mixed atmosphere. In all other respects, the method is just as good as or better than the standard gaspipette method and the gasbag method. Results from 40 measurements with the three methods on 16 persons were examined statistically, and the average toluene absorption at 100 ppm exposure levels was estimated to be 1.6 mg/min.

Adult↗
PubMed1984

Cardiopulmonary response to exercise in patients with neuromuscular diseases.

In order to evaluate the possible effects of respiratory muscle training in patients with neuromuscular disease, we examined the cardiopulmonary response in 13 patients and 17 healthy controls by recording flow volume curves, ECG and alveolar carbon dioxide levels and collecting mixed expiratory air in Douglas bags. The cardiopulmonary response of our patients was not significantly different from that of the controls, and therefore we see no reason to avoid muscle training in patients with such disease.

Adolescent↗
PubMed1984

Factors determining residual volume in normal and asthmatic subjects.

We have studied the mechanisms determining the residual volume (RV), by inducing temporary changes in RV through respiratory manoeuvres and bronchodilation. Four asthmatic and 5 normal subjects inhaled placebo, salbutamol, and ipratropium bromide, and performed maximum expiratory manoeuvres after partial and maximal inspiration. RV and static lung pressure-volume measurements were made in each experiment. After bronchodilation, RV increased in both groups after a maximal inspiration, while bronchodilatation, as such, decreased RV in both groups. We also found unexpectedly that in the asthmatic patients, the static transpulmonary pressure (Pst) at low lung volumes increased after bronchodilatation. Our findings can be explained if bronchodilators open-up closed airways, and if a preceding maximal inspiration decreases the elastic recoil pressure of the lungs causing a change of the lung volume at which airway closure occurs. The results also support that Pst at low lung volume is influenced by airway closure and underestimates the elastic recoil pressure of the lungs, even in normal subjects. We postulate that the increase in Pst at low lung volumes after bronchodilatation is due to smaller amounts of trapped gas.

Adult↗
PubMed1983

Density dependence of maximal flow in dogs with central and peripheral obstruction.

In 12 anesthetized, tracheotomized, vagotomized, open-chested, mongrel dogs we measured end and side hole airway pressures during forced expiration using a Pitot static probe. Volume was obtained as the integral of flow from a dog plethysmograph with frequency response adequate to 20 Hz. Equal pressure points (EPPs) and choke points (CPs) were located with dogs breathing air or a mixture of 80% helium-20% oxygen (HeO2) before and after partial obstruction of the trachea and intravenous histamine and propranolol. At 50% of vital capacity (VC) the CP was in the trachea in 11 of 12 dogs. Partial obstruction of the trachea decreased flow during the plateau of the maximum expiratory flow-volume curve (MEFVC) with the CP remaining in the trachea. The MEFVC plateau was extended to a lower lung volume. At 50% of VC the EPP moved downstream and density dependence remained high. Histamine and propranolol caused EPPs and CPs to move towards the periphery and density dependence to decrease. The shape of the MEFVC changed as the plateau was shortened and, in some instances, abolished. A plateau on the MEFVC could be regenerated by partial obstruction of the trachea. This was accompanied by return of the CP to the trachea and an increase in density dependence. Changes in density dependence were found to be a result of both the relocation of sites of flow limitation and differences in local CP areas with HeO2 and air.

Airway Obstruction↗
PubMed1983

Human response to controlled levels of toluene in six-hour exposures.

The nasal mucus flow, lung function, subjective response, and psychometric performance of 16 young healthy subjects was studied during 6-h exposures to clean air and to 10, 40 or 100 ppm of toluene under controlled conditions. The toluene exposures did not affect nasal mucus flow or lung function. At 100 ppm irritation was experienced in the eyes and in the nose. There was a significant deterioration in the perceived air quality and a significant increased odor level during all exposures to toluene. The test battery investigated visual perception, vigilance, psychomotor functions, and higher cortical functions and comprised five-choice, rotary pursuit, screw-plate, Landolt's rings, Bourdon Wiersma, multiplication, sentence comprehension, and word memory tests. In these eight tests measuring 20 parameters, no statistically significant effects of the toluene exposure occurred. For three tests (multiplication errors, Landolt's rings, and the screw plate test) there was a borderline significance (0.05% less than p less than 0.10%). The subjects felt that the tests were more difficult and strenuous during the 100-ppm exposure, for which headache, dizziness, and feeling of intoxication were significantly more often reported. The exposures to 10 and 40 ppm did not result in any adverse effects.

Adult↗
PubMed1982

Airway compliance and flow limitation during forced expiration in dogs.

Bronchial pressure measured by means of a Pitot static probe, esophageal pressure, and airflow were monitored during forced lung deflations in six anesthetized dogs. Dynamic transmural pressure-cross-sectional area area curves (Ptm-A curves) were constructed for three intrathoracic tracheal positions and one right lower lobal bronchial position. From the Ptm-A curves the maximal possible flow (Vmax) through the airways at each of the four positions was calculated and compared with the overall maximal flow obtained during the same deflation. The peak of the maximal expiratory flow-volume curve (MEFV curve) equaled the calculated Vmax at more than one position in the trachea but did not reach the Vmax calculated for the more peripheral position. During the transition between the peak and the plateau of the MEFV curve, the Ptm-A curve often changed shape, indicating an abrupt change in the "tube law," probably due to changes in axial tension of the airway. During the flow-volume curve plateau, measured flow was near an estimated Vmax at a single point in the trachea. At lower lung volumes where the MEFV curve descends from the plateau, measured flow equaled Vmax calculated for the right lower lobe position. This indicates that after an initial period with no localized choking a "choke point" develops and eventually moves toward the periphery. We conclude that measurement of dynamic Ptm-A curves allows a precise prediction of maximal expiratory flows from the properties of the airways.

Animals↗
PubMed1982

Density dependence of maximum expiratory flow in the dog.

Airway lateral and impaction pressures were measured during expiratory flow limitation in six anesthetized, vagotomized, tracheally intubated, open-chest dogs with the lungs filled with air or a mixture of 80% helium-20% oxygen (HeO2). Pressures were measured in the vicinity of equal pressure points (EPP) and choke points (CP). Maximum flow (Vmax) was ensured by demonstrating no increase in flow with a 50% increase of driving pressure. At 50% vital capacity, mean density dependence (VmaxHeO2/Vmaxair) was 1.58, which was less than 1.69 predicted for fully density-dependent flow. Transmural pressure and airway area at CP and EPP (located on air) were significantly less with HeO2 than with air. Frictional losses between the alveoli and CP were 40% greater with HeO2 than with air. These enhanced losses were mostly peripheral to the EPP. Frictional loss upstream from the EPP was 47% of the total pressure loss on air and increased to 70% on HeO2. The data at 50% VC suggest that these higher frictional losses with HeO2 resulted in decreased density dependence of Vmax due to different pressure distribution along the airway with a lower transmural pressure and smaller area at the CP.

Air↗
PubMed1982

Maximal expiratory flows and forced vital capacity in normal, asthmatic and bronchitic subjects after salbutamol and ipratropium bromide.

A total of 2,880 maximum expiratory flow-volume curves were performed in a controlled double-blind cross-over examination designed to evaluate the bronchodilating effects of two different nebulized doses of salbutamol (1.75 and 0.875 mg) and ipratropium bromide (0.175 and 0.0875 mg) inhaled by 8 normal, 8 asthmatic, and 8 bronchitic subjects. FEV1, FVC, and flows at 50% FVC and at three fixed volumes below TLC have been measured over a period of 6 h on the maximum expiratory flow-volume curve. In the normal subjects, salbutamol seems to have a smaller bronchodilating effect than ipratropium bromide both at high and low lung volumes. After salbutamol the average initial FEV1 increased from 4.0 to 4.3 liters, whereas after ipratropium bromide it increased to 4.4 liters. In our asthmatic patients the initial response to salbutamol was much larger than to ipratropium bromide. After salbutamol FEV1 increased from 1.8 to 2.7 liters in 60 min, whereas after ipratropium bromide it increased to 2.4 liters in 120 min. In our bronchitic patients the difference between the two drugs seems to be very small. After both drugs FEV1 increased from 1.6 to 2.1 liters. The choice of drug for treatment of the condition would then depend on how well the individual patients tolerate the two drugs.

Adult↗
PubMed1982

Serum antibodies and immunoglobulins in smokers and nonsmokers.

Antibodies to antigens in humidifier water were detected by double immunodiffusion in 30 of 63 (47.6%) persons who were exposed to aerosols from a water humidification unit in a cigar plant, whereas no antibodies could be detected in 49 unexposed blood donors (P less than 0.001). The presence of antibodies could not be related to fever or pulmonary symptoms (cough, expectoration, dyspnoe). Antibodies were found in 14 (93.3%) of 15 nonsmokers and in only 13 (31.7%) of 41 smokers (P less than 0.001), and the titres were highest in nonsmokers. Serum IgG and IgA levels were higher in nonsmokers than in smokers, and the variances within the groups were significantly different (F less than 0.05 and F less than 0.05, respectively). The mean serum IgM values were not significantly different in the two groups. Antibodies to Candida albicans and Escherichia coli 04 and 075 were detected with equal prevalences and titres in smokers and nonsmokers. These findings suggest that tobacco smoking may suppress the humoral immune response to inhaled antigens but not to antigens which are supposed to be absorbed through membranes other than those of the bronchopulmonary system. They may partly explain the reported increased incidence of allergic alveolitis in nonsmokers.

Adolescent↗
PubMed1980

The relationship between maximal ventilation, breathing pattern and mechanical limitation of ventilation.

1. The extent to which the pattern of breathing at maximal ventilation in man is affected by the mechanical properties of the respiratory pump has been studied. 2. The maximal effort flow volume (MEFV) loop has been used to calculate the shortest possible inspiratory (TI) and expiratory (TE) durations associated with the highest ventilation for all tidal volumes (VT). These minimal TIS and TES hve been plotted on a VT-TI-TE diagram. 3. Such predicted minimal TIS and TES were compared with observed minimal values from five healthy subjects who tried to reach their maximal ventilations during three experimental conditions: maximal voluntary hyperventilation, rebreathing, and graded exercise. 4. We have found that exercise increases the maximal flows at all lung volumes and confirmed that rebreathing has no such effect. 5. During hyperventilation the mechanical limits were followed closely for all VTS. During exercise and rebreathing the VT-TI and the VT-TE relationships showed a definite maximum of VT at submaximal ventilation in half the cases. The calculated minimal TIS and TES were approached but not reached. This indicates that maximal ventilation is not entirely limited by the mechanical properties of the respiratory pump, but that mechanical factors influence the regulation of breathing pattern when ventilation approaches the maximal capacity of the respiratory pump.

Adult↗
PubMed1980

Effect of freon inhalation on maximal expiratoryflows and heart rhythm after treatment with salbutamol and ipratropium bromide.

The purpose of this investigation was to determine whether inhalation of a freon gas mixture, the propellant of the commercial metered-dose aerosols, consisting of freon 11, freon 12, and freon 114, reduces the bronchodilating effects of inhaled salbutamol or ipratropium bromide or causes cardiac arrhythmias in control, asthmatic and bronchitic subjects. FEV1 and flows measured at different lung volumes on the maximal effort expiratoryflow-volume curve were measured during a period of 6 h. Inhalation of freon caused no significant overall reduction in the salbutamol and ipratropium bromide response in any group. Arrhythmias only occurred among the asthmatic and bronchitic patients, and were most frequent after salbutamol. Ventricular extrasystoles occurred in three cases, all after salbutamol and in two of these in combination with freon inhalation. In one patient there was furthermore hyposia and hypercapnia. The combination of the effects of hypoxia, hypercapnia, catecholamines and freon on the heart is therefore a more likely cause of arrhythmia than the effect of freon alone.

Adult↗
PubMed1979

A double blind cross-over study of maximal expiratory flows and arterial blood gas tensions in normals, asthmatics and bronchitics after salbutamol and ipratropin.

8 normals, 8 asthmatics and 8 bronchitics inhaled comparable doses of ipratropin and salbutamol. Five different flow-volume parameters were measured before and at intervals from 3 to 360 minutes after inhalation, on a total number of 2880 maximal effort expiratory flow-volume curves. Arterial blood gas tensions were measured before and 60 minutes after inhalation. In all parameters a significant larger effect (p less than 0.05) of ipratropin was found in normals, but in different time intervals. The parameter FEV1 and MEF at 50% of FVC showed the largest effect of salbutamol during the interval from 3 to 60 minutes in the asthma patients. None of the parameters showed significant difference in drug effects in the bronchitis patients. The findings suggested a more peripheral action of ipratropin than of salbutamol in the normals. No significant change in gas tensions were found after inhalation in any of the three groups.

Albuterol↗
PubMed1977

The compliance curve for the flow limiting segments of the airway. II. Experiments with human subjects.

Maximum effort flow-static recoil curves were obtained in 5 healthy subjects breathing air, He/O2, and SF6/O2 mixtures. In 4 of them maximum effort flows corresponded to really maximal flows and their curves were transformed into compliance curves for the flow limiting segments of the airway and analyzed from the point of view of a previously presented lung model (Pedersen and Nielsen 1976). The results showed, that viscosity dependent pressure losses from the alveoli to the flow limiting segments were minimal for air and SF6/O2, but not for He/O2. When viscosity dependent pressure lossess could be negleted, then expiration of gases of different densities gave almost identical compliance curves for the flow limiting segments. This supported the applicability of the model. The calculated compliance curves for the flow limiting segments were compared with data from the literature, and the findings indicated that flow limitation during expirations with just maximal flows throughout began in the extrapulmonary airways and moved upstream during the expiration.

Adolescent↗
PubMed1977

The effect of oxygen on peripheral airways.

In ten normal young subjects four alveolar O2-concentration levels ranging from about 7% to 95% were obtained by breathing different concentrations of oxygen in nitrogen at a constant alveolar CO2-concentration of about 5%. Maximum expiratory flows at 60% TLC were measured at each level and corrected for the influence of the expired gas density on flow. The corrected maximum flows were not significantly different, which is taken as evidence of no effect of oxygen on tone of peripheral bronchi.

Adult↗
PubMed1977

The compliance curve for the flow limiting segments of the airway. I. Model studies.

By means of a pilot-static tube airway compliance curves describing the cross-sectional area (A) as a function of transmural pressure (Ptm) were constructed for several locations in the elastic airway of a mechanical model of the lung. From these curves local relations between elastic recoil pressure of the lung (Pel) and maximal expiratory flow (Vmax) were calculated and compared with the experimentally determined Pel-Vmax curve for the entire airway, i.e. all parts in series. Theory and experiments showed that the latter was the lower borderline of all the local Pel-Vmax curves. This means that the maximal flow through the entire airway at a given Pel is determined by the segment of the airway, having the smallest Vmax, just as the maximal strength of a chain is determined by its weakest link. The relation between the critical transmural pressure (Ptm-) and the corresponding cross-sectional area (A-) was derived from the experimental Pel-Vmax curve. This Ptm--A- curve had a composed appearance, which was found to reflect parts of the different local Ptm-A curves and transitions between them because of movement of the flow limiting site within the airway. The Ptm--A- curve depends on the elastic properties of the flow limiting segment, and the slope of this curve (dA-/dPtm-) is the compliance of the flow limiting segment. Significant frictional pressure losses upstream from the site of flow limitation caused underestimation of both A- and dA-/dPtm-, but downstream pressure losses had no influence on the Ptm--A- curve.

Airway Resistance↗