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Biomedical subjects

H Bachofen

Publications and source records attributed to H Bachofen.

At least 55 records · Page 3Linked to original sources
PubMed1983

Morphometric estimates of diffusing capacity in lungs fixed under zone II and zone III conditions.

Comparative morphometric estimates of the diffusing capacity (DL) were made in rabbit lungs fixed by vascular perfusion under lower zone II and zone III conditions and in lungs fixed by instillation of fixatives into the airways. Owing to a reduction of both capillary volume and membrane diffusing capacity DL of zone II lungs (0.074 +/- 0.007 (SD) ml . sec-1 . mbar-1). was found to be lower by some 25% than DL of instillation-fixed lungs (0.102 +/- 0.012 (SD) ml . sec-1 . mbar-1). The average value of DL of air-filled zone III lungs, on the other hand, almost matched the DL of instillation-fixed lungs. However, DL is not equal in all regions but increases along the vertical axis of zone III lungs. Hence, the previous conclusion that morphometric estimates of DL in instillation-fixed lungs reflects a structural limit for O2 diffusion, which cannot be reached under physiologic conditions, must be revised.

Animals↗
PubMed1982

A model for mechanical structure of the alveolar duct.

The appearance of the microstructure of the lung as revealed in transmission and scanning electron micrographs of perfusion-fixed air- and saline-filled lungs suggests the following model for the structure of the alveolar duct. There are two networks of force-bearing elements. The first is an interdependent part of the peripheral connective tissue system that starts from the pleura and extends into the interlobar and interlobular fissures. At the sublobular level, its geometry is not yet fully clear. This network is extended by changes in lung volume and is insensitive to surface tension. The second network is composed of the line elements that form the rims of the alveolar openings. This network is the terminal part of the axial fiber system that surrounds bronchi, bronchioli, and arteries. The line elements of this network are extended by the outward force of surface tension. The two-dimensional alveolar walls that form the alveoli are negligible mechanical components except as platforms for surface tension at the air-liquid interface. An analysis of the mechanics of this model yields relations among surface area, recoil pressure, lung volume, and surface tension that are consistent with published data for lung volumes below 80% of total lung capacity.

Animals↗
PubMed1982

Electron microscopy of rapidly frozen lungs: evaluation on the basis of standard criteria.

In recent years there has been a debate about the validity of the various methods for fixing lung tissue for electron microscopy in a state that faithfully reflects the physiological conditions prevailing at the time of fixation. Mazzone et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 45: 325-333, 1978) introduced a method of rapid freezing followed by freeze-substitution fixation and found good preservation of fine structure; they claimed this method to be superior to others because it allowed careful control of physiological conditions. We have tested the suitability of this method for morphometric studies, where random sampling requires homogeneity of tissue preservation. The results are discussed on the basis of some standard criteria for the faithfulness of structural preservation. In terms of external standards, it was confirmed that one can find parts of the lung tissue samples to show a picture that is compatible with the established equivalent image of eucaryotic cells and tissues; however, the structure of blood was poorly preserved. In terms of the internal standards the method was found to yield inconsistent results; the specimens showed a wide spectrum of images of alveolar septa and capillaries, with "good preservation" limited to a very narrow area; furthermore, the method has a low level of reproducibility. We conclude that for the lung the method of freeze-substitution fixation is not suitable for morphometric work.

Animals↗
PubMed1982

Perfusion fixation of lungs for structure-function analysis: credits and limitations.

The quality of tissue preservation in lungs fixed by vascular perfusion has been reevaluated. Excised rabbit lungs inflated to 60% of total lung capacity were perfused (zone III conditions) with different but widely used fixatives. The effects of the perfusates on pertinent physiological variables have been assessed by a continuous monitoring, the effects on the pulmonary microstructure by qualitative and morphometric analysis of electron micrographs. Important results include the following. 1) Perfusions with isotonic glutaraldehyde at flow rates within the physiological range produce large increases of perfusion pressure and lung weight that reflect intracellular, interstitial, and intra-alveolar edema. 2) No edema occurs if glutaraldehyde is added to isotonic buffer solutions (total osmolarity 510 mosM). 3) Glutaraldehyde as sole perfusate does not fully eliminate the retractive force of lung tissue. Upon release of transpulmonary pressure the lungs retract by an indeterminable amount. 4) Satisfactory results can be obtained by sequential perfusion with osmium tetroxide and uranyl acetate or glutaraldehyde (510 mosM) followed by osmium tetroxide and uranyl acetate. The latter combination yields optimal preparations to study the alveolar and capillary architecture but causes a hyperosmotic volume loss of lung cells (cell shrinkage).

Animals↗
PubMed1982

Surfaces and volumes of alveolar tissue under zone II and zone III conditions.

The functional anatomy of alveolar septa has been studied in rabbit lungs fixed by vascular perfusion under middle zone II and zone III conditions at a constant lung inflation level of 60% of total lung capacity. Capillary volume increases down the vertical axis of the lungs in both conditions and is larger by about 30% in zone III than in zone II lungs. The concomitant changes of free alveolar, epithelial, and capillary surface areas are small. Capillary volume increases within the observed range of pressures neither by recruitment of collapsed capillaries nor by unfolding of pleats of alveolar septa and capillary walls, but rather by deformation and distension of tissue: scanning electron micrographs reveal a more conspicuous bulging of capillaries in zone III than in zone II lungs. Accordingly, the mechanical structure of alveolar septa appears to be largely consistent with a sheet-flow model.

Animals↗
PubMed1981

[Bronchoconstrictive side effects of timolol eye drops in patients with obstructive lung disease].

A double-blind crossover study in seven patients with glaucoma and obstructive lung disease revealed a considerable and significant bronchoconstrictive side effect on topically administered timolol maleat. Comparative treatment of these patients with an ophthalmic solution containing 3% carbachol did not yield a statistically significant bronchial reaction. However, the observation of serious lung function impairment in three patients suggests that carbachol is not a safe alternative for the treatment of glaucoma in patients with obstructive lung disease. Whenever a deterioration of airway obstruction occurs in elderly patients, or bronchial asthma becomes manifest late in life, topically administered beta-adrenergic-receptor blocking and cholinergic agents must be considered causative factors: optimal communication between all physicians caring for glaucoma patients is an essential prerequisite.

Aged↗
PubMed1981

[Accumulation of eosinophils in the nasal secretion in patients with bronchial asthma].

From October 1977 to September 1979 69 out of 500 asthmatic patients were selected in whom case histories, skin tests and IgE blood-levels formed a sub-group with more or less pure allergic asthma and a sub-group with more or less pure intrinsic asthma. All the patients exhibited a large quantity of granulocytes in the bronchial and nasal secretions. Special attention was paid to the contents of eosinophils in the nasal smear and in the bronchial mucus. The intrinsic subgroup had a (non significantly) greater incidence of 100% eosinophils in the bronchial secretion than the allergic sub-group (p less than 0.1). Unexpectedly, the reverse was found in the nasal secretions: only 33% of the intrinsics (9 cases) and as many as 67% of the allergics (28 cases) exhibited 100% eosinophils in the nasal mucus (p less than 0.025). Thus, when discussing the two forms of asthma, allergic and intrinsic, it is always necessary to bear in mind the possible paradoxical behaviour between nasal and bronchial mucus: pure eosinophilia in the lower respiratory tract may often be found concomitantly with pure neutrophilia in the upper respiratory tract, when some of the criteria for intrinsic asthma are fulfilled.

Asthma↗
PubMed1981

Effects of glutaraldehyde or osmium tetroxide fixation on the osmotic properties of lung cells.

The osmotic properties of lung cells have been tested before and after perfusion fixation of isolated, perfused lungs with either glutaraldehyde or osmium tetroxide. The testing procedure was to add hypertonic sucrose to the perfusate for several minutes and monitor the lung weight response (an 'osmotic transient'). Each lung was perfused with one or the other fixative solutions for 10 min, then the perfusate was changed back to Ringer-lactate before the post-fixation test was conducted. The results indicate that osmium tetroxide makes the cell membranes as permeable to sucrose as to water, and that sucrose thus causes no osmotic volume change. Glutaraldehyde, on the other hand, apparently preserves the impermeability of the cell membranes to sucrose, but the osmotic volume response is attenuated, indicating that significant changes in the cells have occurred.

Aldehydes↗
PubMed1981

Lung tissue volume changes induced by hypertonic NaCl: morphometric evaluation.

Lung tissue was examined to determine how the volumes of alveolar septum components change when NaCl is added to the vascular perfusate, increasing the osmolarity by 70 mosM. Isolated rabbit lungs were perfused with Ringer solution containing dextran, either with or without added NaCl, and fixed by vascular perfusion. Tissue samples from both "control" and "hypertonic" lungs, prepared for electron microscopy, were examined using established morphometric procedures. Volumes of septal cells, interstitial space, capillary lumen, surface-lining layer, and endothelial and epithelial areas were measured, all normalized against the endothelium basement-membrane area. Results showed that hypertonic NaCl caused a reduction in total cell and surface-lining layer volumes but no change in interstitial or capillary lumen volumes. This supports the hypothesis that small molecules have no osmotic effect across the pulmonary capillary endothelium but do cause a fluid flux from cells and across the alveolar epithelium. Areas and volume measurements for different septal cell types suggest a heterogeneous response: epithelial cells showed significant decreases and endothelial cells changed little, if at all.

Air Pressure↗
PubMed1980

[Euphyllin retard and "exercise-induced" asthma].

In a double blind crossover experiment the protective effect of theophylline slow-releasing coated tablets (Euphyllin retard) on exercise-induced asthma has been compared with that of a placebo. Sixteen patients with bronchial asthma (mean age 23 years, range 16-49 years) who were selected in a preliminary test exhibited an FEV1 decrease greater than 15% 10 minutes after an exhausting 6 minute run on the treadmill. Euphyllin retard and placebo were given 6 hours before the exercise test. Venous blood was sampled 6 hours prior to and immediately before exercise in order to determine the plasma concentrations of theophylline by a tritium radioimmunoassay method. FEV1 was measured prior to and immediately after exercise, 10 and 20 minutes later and after a final orciprenaline inhalation. A group of 9 patients (group 1) has plasma concentrations of theophylline lower than 6.2 microgram/ml (4.8 +/- 0.9 microgram/ml), and a group of 7 patients (group 2) had concentrations higher than 10.0 microgram/ml (13.8 +/- 3.3 microgram/ml). Compared with placebo, a protective effect of Euphyllin retard could be observed in group 2 only (p < 0.025). In group 1 the asthma protection was indistinguishable form that of placebo. Hence, plasma concentrations higher than 10 microgram/ml appear to be required to protect asthmatics from exercise-induced asthma. Although in some patients an effective concentration can be achieved by the recommended dose of one tablet of Euphyllin retard (350 mg aminophylline) every 12 hours, the importance of measuring plasma concentrations must be emphasized in view of the variable absorption and elimination of theophylline. Side effects may occur at concentrations higher than 15 microgram/ml.

Asthma↗
PubMed1979

[Follow-up of severe adult respiratory distress syndrome].

The results are presented of the clinical, radiological and pulmonary function follow ups in 6 patients 19 to 35 months after the onset of a most severe adult respiratory distress syndrome (ARDS). The previously healthy young patients required ventilatory support for 16 to 135 days, reflecting the severity of the ARDS. In agreement with earlier studies, lung function improved rapidly in the first year but barely thereafter. Nineteen to 35 months after the ARDS a mild to moderate degree of restrictive ventilatory impairment could be detected in all our patients, associated with a significant arterial hypoxemia on exercise in five. Additionally, three patients showed signs of reversible airway obstruction. If the subacute course rather than the acute phase of the disease is taken as the criterion, there appears to be a relationship between the severity of the ARDS and the residual impairment of lung function. The fact that even most severe lung damage eventually led to a more or less significant loss of the functional reserves of the lung, but hardly ever ended in chronic respiratory failure, justifies all possible intensive care efforts in the treatment of those patients.

Adult↗
PubMed1979

[The rate of isometric inspiratory pressure change as a measure for the CO2 sensitivity of the respiratory center in patients with obstructive lung disease].

In healthy persons with and without loaded breathing, in asthmatics, and in patients with chronic obstructive lung disease (COLD) the rate of isometric inspiratory pressure development ([dp/dt]max) has been measured in order to assess the clinical significance of (dp/dt)max as an index of the motor output of the respiratory center in response to increased levels of carbon dioxide. During unloaded breathing normal subjects showed an excellent correlation between the ventilatory and the (dp/dt)max responses to CO2. Normal persons breathing through an external expiratory flow resistance, the asthmatics, and the patients with COLD had not only a blunted ventilatory response, but also a reduced (dp/dt)max response. The parallel changes observed in both variables indicate that under conditions of mechanical loading the (dp/dt)max does not exclusively reflect the motor output of the respiratory center, but is influenced by other factors such as the work of breathing and the mechanical efficiency of the respiratory pump. Accordingly, measurements of (dp/dt)max are of little help in deciding whether the development of CO2 retention in patients with obstructive airway disease is primarily due to increased mechanical load or to decreased sensitivity of the respiratory center.

Adult↗
PubMed1979

Alterations of mechanical properties and morphology in excised rabbit lungs rinsed with a detergent.

To assess the influence of alterations of lung surfactant on the geometry of peripheral air spaces, the morphology of detergent-rinsed rabbit lungs was studied. In comparison to normal excised rabbit lungs, fixed in the same manner by vascular perfusion at different points on the deflation pressure-volume curve, the most important differences are as follows. 1) With decreasing lung volume there is a progressive collapse of alveoli; at low lung volume (40% of total lung capacity (TLC) (most alveoli are collapsed, and the air is contained in overextended ducts. 2) Accordingly, the alveolar surface area-to-volume ratio is considerably smaller in particular at medium and low lung volumes. 3) There is only a slight change of mean air-space curvature between 80 and 40% TLC. Hence, the results indicate that in detergent-rinsed lungs volume changes are brought about predominantly by recruitment and derecruitment of alveoli. It appears that both a normal surfactant and the mechanical interdependence within the fibrous continuum are required to maintain a normal respiratory surface area within the lung volume range of normal breathing.

Animals↗
PubMed1979

Alveolar volume-surface area relation in air- and saline-filled lungs fixed by vascular perfusion.

The influence of volume changes and interfacial forces on the geometry of peripheral air spaces was studied in excised rabbit lungs inflated with either air or saline and fixed by vascular perfusion at four points of the deflation limb of the pressure-volume curve corresponding to 100, 80, 60, and 40% of the total lung capacity (TLC). In air-filled lungs pleating and folding of alveolar septa were observed, especially in alveolar corners. However, the alveolar surfaces were smooth, except at low lung volumes where some surface crumpling occurred. In saline-filled lungs pleats were absent; the alveolar surface was irregular at all inflation levels due to undulating walls and bulging capillaries. Morphometry indicated that at all alveolar volumes (VA) the surface areas (SA) were larger in saline- than air-filled lungs. No simple mathematical function was found to characterize the relation between SA and VA over the entire volume range studied. Within the range of normal breaths (80 to 40% TLC) the best fit for n in the function SA = k.VnA was 0.58 for saline-filled lungs (r = 0.93) and 0.33 for air-filled lungs (r = 0.68), suggesting different and complex deflation patterns.

Animals↗
PubMed1979

A simple method for computing airway resistance and specific airways conductance from scalar plethysmographic recordings.

An alternative procedure to evaluate plethysmographic tracings is described for the determination of airway resistance (Raw) and specific airway conductance (SGaw). Raw and SGaw obtained with this method reflect the average resistive impedance over one breathing cycle. Although both work and apparative expenditures are minimal, the results are well comparable with those calculated with more involved methods. The technique is particularly well suited for patients with impaired cooperation since SGaw can be determined without measuring the intrathoracic gas volume.

Airway Resistance↗