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  • 1
    Electronic Resource
    Electronic Resource
    Cardiac afferents and the renal response to positive pressure ventilation in the dog (1986)
    Springer
    Intensive care medicine 12 (1986), S. 147-152 
    Details
    ISSN: 1432-1238
    Keywords: Cardiac afferents ; Denervation of the heart ; Controlled mechanical ventilation ; Positive airway pressure ; Kidney function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of cardiac denervation on renal function during spontaneous breathing (SB) and controlled mechanical ventilation (CMV) were investigated in six mongrel dogs. Selective and reversible blockade of cardiac afferents was achieved by instillation of procaine 2% into the pericardium. Application of procaine 2% into the pericardium during SB caused a statistically significant depression of urine flow (-55%), of sodium (-64%) and potassium excretion (-42%), and of inulin (-21%) and PAH-clearance (-30%). After institution of CMV with a positive end-expiratory pressure (PEEP) of 10 cm H2O a further, statistically significant decrease in urine flow (-42%) and sodium excretion (-70%) and of the inulin (-15%) and PAH-clearance (-38%) was observed. Global hemodynamics, mean arterial pressure (MAP), central venous pressure (CVP), mean pulmonary artery pressure (MPAP) and cardiac index (CI) did not change significantly after installing procaine 2% into the pericardium during SB. After institution of CMV an increase in CVP and MPAP occurred whereas MAP and CI remained unchanged. During the following periods of spontaneous breathing first with blockade of cardiac afferents and later after washing out the procaine with NaCl 0.9% all parameters of renal function approached control levels as measured in the first period of spontaneous breathing without cardiac denervation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254930
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Total inspiratory work with modern demand valve devices compared to continuous flow CPAP (1988)
    Springer
    Intensive care medicine 14 (1988), S. 632-639 
    Details
    ISSN: 1432-1238
    Keywords: Continuous flow CPAP ; Demand valve CPAP ; Electromechanical lung model ; Work of breathing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The inspiratory work exerted by an electromechanical lung model in drawing a 500ml breath, was assessed by planimetry of pressure/volume loops for six commercial demand valve CPAP devices (Servo B and C from Siemens, EV-A and UV-2 from Dräger, the Puritan Bennett 7200 and the Engström ERICA) and compared to the loading of a conventional high flow CPAP system. The effect of trigger sensitivity and inspiratory pressure support on inspiratory work was also investigated in some cases. The lung model allowed for calibrated changes in compliance and airway resistance. In the non-assisted CPAP mode, all machines required slightly larger amounts of inspiratory work than the continuous flow CPAP system. Most machines were comparable in performance but the ERICA and the Servo B required up to 22% more work than the continuous flow CPAP system and represented the maximal increase of total work due to any given machine. The greater part of total inspiratory work was due to lung compliance and airway resistance, factors external to the machines. Halving complicance doubled the work and exchanging a 7 for a 9 mm i.d. endotracheal tube in the circuit increased work by about 3% regardless of machine. Decreasing trigger sensitivity from 0 to 2 cm H2O for the Servo B increased work by up to 24%. Using 5 cm H2O of inspiratory pressure support decreased work for all machines up to 36% maximally. In conclusion, under the chosen experimental conditions the inspiratory work of breathing was only minimally increased with the following demand valve systems in comparison to a continuous flow CPAP system: Servo C, EV-A, UV-2, and Bennett 7200. The remaining required additional work could be eliminated by using inspiratory pressure support. However, triggering effort remains the unavoidable additional load of demand valve CPAP systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00256768
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A comparison of the stimulus-response curves of aortic and carotid sinus baroreceptors in decerebrated cats (1979)
    Springer
    Pflügers Archiv 383 (1979), S. 47-53 
    Details
    ISSN: 1432-2013
    Keywords: Baroreceptor response curves ; Aortic vs. carotid baroreceptors ; Sensitivity of baroreceptors ; Working range of baroreceptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recordings of total nerve activity suggested differences in the sensitivities and working ranges between aortic and carotid sinus baroreceptors. This result however, conflicts with single fibre studies from isolated receptor zones. Thus it appeared of some interest to compare the function curves of aortic and carotid sinus baroreceptors in the intact animal. This was achieved by comparing the response characteristics of two groups of aortic and carotid sinus baroreceptors in decerebrated cats. One smaller group consisted of 11 receptor pairs, each member of the pair being studied simultaneneously in the same cat, and a larger group consisting of 98 aortic and 49 carotid sinus baroreceptors studied independently of each other. The response of each receptor to wide pressure variations was recorded by inflating and deflating an intraaortic catheter tip balloon. Function curves were derived by plotting receptor discharge in terms of spikes per second against mean aortic pressure. No significant differences were found either in the slope of the function curves or their mean pressures at minimum activity, the latter appearing to be set by the working blood pressure level. Thus it was concluded that aortic and carotid sinus baroreceptors differ neither in their sensitivities nor in their working ranges when in their physiological environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584474
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Fentanyl activates a particular population of vagal efferents which are cardioinhibitory (1980)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 312 (1980), S. 57-61 
    Details
    ISSN: 1432-1912
    Keywords: Fentanyl ; Vagal efferents ; Cardioinhibitory efferents ; Heart rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to determine whether and how opiates affect vagal efferents, effects of fentanyl on single fibre discharge in the cervical vagus in dogs were studied. Dependent upon the responses to induced increases in blood pressure, 3 types of vagal efferents were classified: Type A (n=9) with an increase, type B (b=4) with a decrease and type C (n=27) with no change in rate of discharge. Fentanyl (0.01 mg/kg i.v.) activated type A efferents which are considered as cardioinhibitory, but it did not activate type B and type C efferents. The activation was antagonized by naloxone. Cumulative doses of fentanyl (0.0025–0.16 mg/kg i.v.) produced a progressive increase in the discharge rate of type A efferents and a decrease in heart rate. These effects were maximum at 0.04 mg/kg (n=7). Blood pressure was only slightly affected. The changes in discharge rate and heart rate were strongly and negatively correlated (r=−0.82, P〈0.001). At maximum cardioinhibitory effects of fentanyl, blood pressure increases were able to further activate type A efferents and to decrease heart rate. The results show that fentanyl acts differentially on various vagal efferents. Only type A (cardioinhibitory) efferents are activated. It is hypothesized that the opiate receptor system in the brain plays a physiological role in the control of heart rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00502575
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    Paper (German National Licenses)
    Fulltext
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