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Biomedical subjects

J Kohl

Publications and source records attributed to J Kohl.

At least 55 records · Page 3Linked to original sources
PubMed1984

Breathing pattern and stretch receptor activity during high frequency ventilation.

In anaesthetized rabbits the effects of high frequency ventilation (HFV) on breathing pattern and on stretch receptor (SR) activity were examined in order to elucidate the mechanism underlying the inhibition of respiration during HFV. An attempt was undertaken to compare the effects of HFV with those of static lung inflations. HFV applied in frequencies between 5 Hz and 25 Hz and with peak airway pressure (Paw) between 5 and 15 cm H2O led - proportionally to Paw - to a gradual prolongation of expiration up to an apnoea. Similar effects occurred during lung inflations, although at higher Paw than during HFV. HFV-induced apnoea was accompanied by a tonic phrenic and diaphragmatic activity which was absent during inflation-induced apnoea. In addition to the activity due to spontaneous breathing, during HFV the SR discharge rate increased with each positive airflow pulse particularly in the expiratory phase, whereas the inspiratory discharge rate was less affected. During static lung inflations there was a parallel increase of both inspiratory and expiratory SR activity, the expiratory discharge rate, however, remaining lower and the inspiratory discharge rate rising more than during HFV. It is concluded that the HFV-induced increase of expiratory SR discharge rate may account for the inhibition of spontaneous breathing during HFV. The persistence of phrenic and diaphragmatic activity during HFV-induced apnoea is thought to be due to activation of irritant receptors.

Animals↗
PubMed1984

Gas concentration profiles along airways of dog lungs during high-frequency ventilation.

Following equilibration with inert gases (He and SF6), dog lungs were partially washed out, either by high-frequency ventilation (HFV) or by conventional mechanical ventilation (CMV), to varied inert gas clearance levels, at which expirograms were recorded by mass spectrometry. Relative alveolar slopes were distinctly positive for HFV and tended to increase with lung clearance; they were, however, smaller than those of CMV and were smaller for He than for SF6 during both ventilatory modes. Fowler dead space was smaller for HFV than for CMV, with significant differences between test gases only during CMV. Plots of concentration against linear distance between measuring site and alveolar region showed that most of the total concentration drop during HFV occurred, with nearly linear slope, along the endotracheal tube and the upper airways, with no difference between He and SF6. In the alveolar region, on the other hand, relative concentration gradients were similar for HFV and CMV, both showing separation of He and SF6. The data suggest that gas transport in the upper airways during HFV is not diffusion limited. Gas mixing in alveolar regions, although more complete for HFV than for CMV, is limited by diffusion; however, this incomplete gas mixing does not appreciably limit overall gas transport during HFV.

Animals↗
PubMed1982

The effect of pulmonary stretch receptor activity on the respiratory response to ammonia-inhalation.

The contribution of pulmonary stretch receptor (SR) activity to the changes in breathing pattern (f, VT, tI, tE, tI: tE) following inhalation of ammonia vapour has been studied in rabbits at three levels of lung distension, i.e., three levels of SR activity, and during reversible SO2-blockade of SR. The result show that the increase in breathing frequency (f) and the decrease in tidal volume (VT) due to ammonia inhalation are almost identical for animals with and without blockade of SR, whereas the duration of inspiration and expiration (tI, tE) as well as their relationship (tI:tE) vary considerably, the variations depending on the level of SR activity. For a given tI the expiration was longer in animals with SR intact than in animals with SR blocked. It is concluded that in rabbits the increased activity of SR after inhalation of ammonia counteracts significantly the predominant effects of irritant (deflation) receptor stimulation, thus rendering possible a longer expiration.

Ammonia↗
PubMed1981

Relation between pedalling- and breathing rhythm.

The relationship between pedalling- and breathing rhythm was studied in 34 medical students (non-cyclists") and 10 racing cyclists on an electromagnetic bicycle-ergometer, the effective work load of which (50 W, 100 W, 150 W, 200 W) was independent of the pedalling rate. The criteria used were integer p/b ratios (pedalling rate being a multiple of breathing frequency) and phase coupling (the breathing phases starting preferentially at a certain angle of the pedalling cycle). Unconsciously occurring coordination of pedalling and breathing rhythm was found in the majority of the test persons; 70%-100% of the racing cyclists, 50%-63% of the regularly breathing and 25%-33% of the decreased with increasing work load. Phase coupling was even more frequent than integer p/b ratios and was not affected by increasing work load. The majority of racing cyclists (unlike the non-cyclists) coupled the inspiration-onset with the onset of either the left or the right leg movement. Expiratory phase coupling, however, was analogous in all groups; expiration began preferentially at mid-contraction of either leg. The results are discussed in terms of relative (nervous) coordination. It is concluded that the tendency to coordination between pedalling- and breathing rhythm increases with pedalling training and with regularity of breathing.

Adult↗
PubMed1980

Stretch receptor activity during irritant-induced tachypnoea in the rabbit.

The activity in single vagal fibres arising from lung stretch receptors was recorded in rabbits during normal breathing at rest and during tachypnoea caused by inhalation of histamine or ammonia. The rate of argon elimination from the lungs was analysed to estimate the accompanying changes of lungs ventilation. The results show that the majority of stretch receptors increased their activity during irritant-induced tachypnoea, the discharge frequency being always higher inspiration than during expiration. Only a few fibres did not change or decreased their activity. The comparison of the results with previous findings in guinea-pig revealed that the discharge pattern of stretch receptors following inhalation of irritants was different in these two species, whereas the respiratory reactions and the unevenness of ventilation were comparable. It is suggested that the differences in the discharge pattern of stretch receptor fibres during irritant-induced hyperpnoea in rabbit and guinea-pig are due to differences in the location of the stretch receptors concerned.

Ammonia↗
PubMed1978

The effect of arterial hypertension of focal ischemic edema. An experimental study.

The middle cerebral artery (MCA) of cats was occluded permanently for 24h to study the influence of arterial hypertension during the early phase of focal ischemia upon the development of endema and changes of the blood-brain barrier (BBB). In normotensive animals MCA occlusion results in a hemispheric weight increase of about 8% and marked water and electrolyte alterations in both the grey and white matter of the MCA territory. The RISA space increases mainly in the grey matter. Hypertension aggravates these changes significantly, whereby water and electrolyte changes in the grey matter are predominantly concerned, while there is a preferential increase of the RISA space in the white matter. It is suggested that arterial hypertension aggravates the ischemic edema and enhances a vasogenic type of edema in the white matter.

Animals↗
PubMed1978

The microvibrations of the body, an index for examination stress.

Changes of whole-body microvibrations (MV) were quantitatively analyzed in 123 voluntary subjects during two examination situations and compared with the results obtained during the ensuing vacation. The force oscillations in the three space directions were measured during quiet bipedal standing and simultaneously recorded as a time function with the rectified and integrated force-time function (= rectified impulse). The rectified impulses related to body weight were used as a measure for the MV. Immediately before the examinations, all the subjects showed high values. These decreased significantly in the control measurement if the subjects passed the exams, but remained relatively high in the subjects who failed. In all three measurements, smokers and candidates who took tranquilizers before the exams show higher MV values than do the other subjects. Females are less tense than males, a difference particularly significant in the vertical (z) direction. The rectified impulse in this direction correlates positively with the estimated cardiac output. Body weight and body length show a positive correlation with the MV values in the horizontal forward-backward (x) and vertical (z) direction. The measurement of the whole-body MV enables quantitative evaluation of the complex load due to an examination situation. The hypothesis that different types of stress or personality affect given directions in space requires further investigation.

Adult↗
PubMed1975

The Hering-Breuer reflexes in the bronchial asthma attack.

The correlation between pulmonary stretch receptor activity and inspiration-expiration duration quotient as well as respiratory frequency (Hering-Breuer reflexes) has been established before and during an asthma attack in the guinea-pig. The Hering-Breuer reflexes subserving the self-regulation of breathing during uninfluenced spontaneous breathing no longer prevail after induction of a bronchial asthma attack. Increased stretch receptor activity following increased lung volume does not lead to inhibition of inspiratory activity (lung inflation reflex), but to an enhancement of the asthmatic tachypnoea. The latter is assumed to result from the expiratory self-compression of the lungs (lung deflation reflex). The enhancement of the deflation reflex by increasing lung volume during the asthma attack is discussed with regard to the uneven ventilation and the conditions in lung mechanics underlying the excitation of the lung deflation or collapse endings.

Animals↗
PubMed1975

The influence of procaine and isoprenaline on the lung deflation reflex during the histamine-induced bronchial asthma attack.

The histamine-induced respiratory reflex response arising from the lung deflation (irritant) receptors was influenced by both procaine and isoprenaline, but in an essentially different manner. Procaine administered via the pulmonary circulation prevented or interrupted the asthmatic tachypnoea associated with stimulation of the lung deflation receptors. The effect was less consistently obtained when the drug was given by way of the bronchial circulation or as an aerosol. It is concluded that the lung deflation receptors in the guinea-pig are located in sites easily accessible by way of the pulmonary circulation, i.e., in the peripheral airways. Isoprenaline, irrespective of the way of administration, counteracted the asthmatic increase in bronchial resistance which underlies the stimulation of the lung deflation receptors. A respiratory response, however, characterized by increased respiratory rate, still occurred when the drug was administered either before or after histamine inhalation. The tachypnoic response to isoprenaline is probably of central origin.

Aerosols↗