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Biomedical subjects

H Magnussen

Publications and source records attributed to H Magnussen.

At least 325 records · Page 18Linked to original sources
PubMed1979

Dco at various breath-holding times: comparison in patients with chronic bronchial asthma and emphysema.

Measurement of Dco is known to be dependent upon functional inhomogeneities. Because different types of inhomogeneities are operative in patients with bronchial asthma and patients with emphysema, different changes of Dco with increasing breath-holding time, tA, are to be expected. We studied the change of Dco with increasing breath-holding time in healthy subjects, patients with asthma bronchiale and patients with emphysema. In the patients the severity of airway obstruction was about the same. The following results were obtained: (a) in healthy subjects and in the asthmatics Dco decreased with tA, in a similar manner, approaching a value (ml . min-1 . Terror-1) of 34.7 and 31.6 at 10 sec, respectively, and (b) in patients with emphysema Dco increased with tA, yielding negative values at small tA: 1.5 sec-23.4; 10 sec: 11.7. From these results we suggest that in healthy subjects and in patients with bronchial asthma parallel inhomogeneities influence the course of Dco. In emphysema the time couse of Dco is best explained with a faster intrapulmonary mixing of He compared to CO. This behavior indicates that in emphysema low Dco values can be mainly attributed to large diffusional resistances (stratification) within the lungs.

Adult↗
PubMed1979

[An experimental and clinical study of the effect of ketotifen in the treatment of extrinsic bronchial asthma (author's transl)].

The therapeutic value of ketotifen (Zaditen), a new anti-allergic drug, was studied in patients with extrinsic bronchial asthma. a) In 8 persons the protective effect on bronchial provocation tests with allergen was examined 3 and 14 days after treatment and compared with cromoglycate (Intal); b) 19 patients were treated for 6 months with 2 x 1 milligram ketotifen (n = 7), 2 x 2 mg ketotifen (n = 7), 2 x 1 mg clemastine (Tavegil) (n = 5). The results were as follows: a) The amount of inhaled allergen causing a fall of 20% in FEV1.0/VC was 9-12 times larger with both therapeutic regimens. b) Ketotifen definitely improved the asthmatic symptoms as compared with clemastine. The improvement was independent of the dosage. Side-effects occurred more frequently with clemastine. The study confirms the in vitro demonstrated anti-analphylactic properties of ketotifen; that it can be taken by mouth is of particular clinical interest.

Asthma↗
PubMed1979

[The value of lung biopsy in the radiological stage of bihilar adenopathy of sarcoidosis (author's transl)].

The classification of intrathoracic sarcoidosis into stages is based on radiological criteria. As pulmonary involvement is often considered to be an indication for corticosteroid therapy a comparison was made between the X-ray picture and lung biopsy in stage I sarcoidosis. Non-caseating epitheloid granulomas were found in 9 of 12 patients. The material was obtained by open biopsy in 8 patients and by the transbronchial approach in one case. Open and transbronchial biopsy failed in 3 patients to demonstrate sarcoid granulomas. The results suggest that the presence of mottling in the chest roentgenogram does not provide the rationale for treatment. Further studies will show whether irreversible damage to lung tissue could be prevented if lung biopsies were taken and, consequently, steroid therapy initiated, at an earlier stage of the disease.

Adult↗
PubMed1979

[The value of measurements of oscillatory resistance in the evaluation of lung function. A comparative study in adults and children (author's transl)].

Measurements of total oscillatory impedance (ROS) together with spirometric and body plethysmographic determinations were made in adults and children and the results were compared. In adults (n = 260) correlation was less close (r = 0.53) than it was in 88 children (r = 0.82). Even if ROS was of similar magnitude the phase shift between pressure and flow tended to be more negative than it was in children. These differences are presumably due to anatomical differences between the adult and the growing lung. In interpretation of the results it is suggested that the differences in the ratio: airways compliance/airways resistance reflect changes arising from age and disease processes.

Adolescent↗
PubMed1979

[Normal values of respiratory resistance in childhood (oscillation method) (author's transl)].

Normal values for respiratory resistance were determined by means of the oscillation method in 257 children and adolescents of both sexes aged 3--17 years. Respiratory resistance, measured by both the oscillatory and plethysmographic method, increased in inverse proportion to body height, body weight, body surface and age. Normal values can be estimated by means of the equation: y = 14.51--0.064X (X = hight in centimetres).

Adolescent↗
PubMed1976

Pulmonary O2 diffusing capacity at exercise by a modified rebreathing method.

The rebreathing technique for the measurement of the pulmonary O2 diffusing capacity, DO2, previously developed for resting conditions [Cerretelli et al., J. appl. Physiol. 37, 526-532 (1974)] has been modified for application to exercise and simplified to one rebreathing maneuver only. The changes consist: 1) in administering in the course of a normoxic exercise a priming breath of an O2 free mixture just before the onset of rebreathing in order to achieve rapidly the appropriate starting PO2 values on the linear part of the O2 dissociation curve as required by the method; 2) in calculating mixed venous blood O2 tension by extrapolation of the alveolar to mixed venous blood PO2 equilibration curve, instead of determining it separately. While the mean DO2 value of 21 measurements on 5 subjects at rest was 30 ml-min-1 - Torr-1 +/- 3 (S.E.), in 2 subjects exercising on a bicycle ergometer, DO2 was found to increase from a resting value of about 32 ml- min-1 - Torr-1 to 107 ml - min-1 - Torr-1 for an eightfold increase of O2 uptake. The validity and the applicability of the method are critically discussed.

Humans↗
PubMed1976

Gas exchange in air sacs: contribution to respiratory gas exchange in ducks.

Air sac gas exchange was studied in ducks by measuring the rates of inert gas uptake and of O2 and CO2 equilibration in caudal thoracic air sac whose ventilation was prevented by surgival sealing of the ostia. The data were analyzed on a model incorporating three possible routes by which air sac gas could be exchanged with the surrounding tissue: (1) into the blood perfusing the air sac walls; (2) into the adjoining air sac via tissue membranes; (3) into the bronchial system of the lung via diffusion through lung tissue bordering upon the caudal thoracic air sac. Exchange rates of gases via the two latter paths were found to be small as compared with the first route. From application of model parameters to O2 and CO2 exchange in air sacs under physiological conditions the following conclusions were drawn: (1) the caudal thoracic air sac makes the major contribution to total gas exchange between air sacs and blood; (2) this exchange can account for less than 5% of total respiratory gas exchange; (3) the exchange is too small to account for the O2 and CO2 partial pressures in caudal thoracic air sacs of ducks. Other mechanisms like gas exchange in neopulmonic parabronchi, which conduct air to the caudal air sacs during inspiration or re-inspiration of dead space appear to play a more significant role in the deviation of O2 and CO2 partial pressures in the caudal air sacs from those in inspired air.

Air Sacs↗
PubMed1976

Convective and diffusive gas mixing in human lungs: experiments and model analysis.

Equilibration of inspired with lung residual gas was studied by a single-breath technique for varying breath-holding time with He, Ar, and SF6 as test gases. The ratio of end-expired (FE') to mean lung concentration after expiration (FL) was always below unity, indicating imperfect mixing of gas in the lung. The ratio of FL/FE' for all gases increased with tB, for any tB the ratio was smallest for SF6 and greatest for He. Similarly, Bohr dead space (VD) at any given tB was greatest for SF6 and smallest for He, with VD decreasing toward an asymptotic value common for all gases as tB increased. The results were analyzed quantitatively on a serial three-compartment model of the lung. Model analysis suggests that both diffusion and convection are effective in equilibrating test gases in the lung during breath holding. Further, stratified inhomogeneities in the absence of convective gas mixing in the alveolar space would seriously limit alveolar respiratory gas exchange; with convection, however, stratification is likely to impose only moderate constraints on resting gas exchange.

Computers↗