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Biomedical subjects

U Smidt

Publications and source records attributed to U Smidt.

At least 37 records · Page 2Linked to original sources
PubMed1981

Intrapulmonary gas transport of He and SF6 in healthy subjects and patients with chronic obstructive lung disease.

Intrapulmonary mixing of inert gases of different diffusivity, He and SF6, was studied in 5 healthy subjects before and after bronchoconstriction induced by acetylcholine and in 4 patients with chronic obstructive lung disease by analyzing alveolar plateaus, determined at various breath-holding times, tBH. The following results were obtained: (a) In healthy subjects in patients the slope of the alveolar plateau-e.e. the partial pressure difference between 750 and 1,250 ml of expirate-decreased for both gases with increasing 5BH.(b) In healthy subjects complete mixing within the alveolar space occurred faster for He than for SF6. In the patients the change of the alveolar slope was similar for both gases and no horizontal plateau was attained within the experimental range of tBH.(c) In healthy subjects after bronchoconstriction the behavior of the alveolar plateaus resembled that of the patients. However, the differences between He and SF6 were smaller. From these results we suggest that in healthy subjects efficient mixing of inspired gas with lung gas is brought about by diffusion and convection. After acetylcholine these mechanisms are less effective to overcome the inequalities produced by parallel inhomogeneities. In the patients there is a considerable decrease in overall mixing efficiency, probably due to large diffusional resistance within peripheral lung units, so that convection here is the main mechanism contributing to a flattening of the alveolar plateau.

Acetylcholine↗
PubMed1981

Determination of respiratory resistance by an oscillation method. Studies of long-term and short-term variability and dependence upon lung volume and compliance.

The respiratory resistance (Ros) as measured by an oscillation method, and the airway resistance (Raw) as measured by body plethysmography were determined in 10 healthy volunteers thrice daily every week over a period of 22 weeks. Ros in 9 of this group was measured at different breathing levels at constant respiratory rate and volume. Additionally, the phase angle between oscillatory pressure and flow (phi), the thoracic gas volume, the end-tidal volume, the functional residual capacity, Raw and the lung compliance were determined. Furthermore Ros of 116 patients was measured together with the lung and thorax compliance. Compared to Raw, the variability of Ros is smaller and the sensitivity is higher. There is a reciprocal relationship between Ros and lung volume, lung compliance, and compliance of the lung and thorax system. Therefore, measurements of Ros should be performed at a normal, stabilized mean breathing level.

Adult↗
PubMed1979

[Oscillatory determination of functional residual capacity (FRC)].

The washing-in of a low density gas (80% He, 20% O2) into the lung is being eased by greater diffusibility and diminished work of breathing. Helium analysis was performed by means of the oscillation method with an equipment suitable for the assessment of resistance to breathing. The density of helium gas mixture is being compared to the density of ambient air.

Functional Residual Capacity↗