Acta anaesthesiologica Scandinavica
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Acta Anaesthesiol Scand · Aug 1979
The circulatory response to specific ventilatory patterns using a tidal volume ventilator.
The circulatory response to different ventilatory patterns during artificial ventilation was examined in 17 sternotomized piglets. A constant CO2-tension level was maintained in all investigations by reference to analyses of the end-tidal infra-red CO2 fraction and arterial CO2-tension. The greatest variation in mean values for end-tidal CO2-tension was 0.2 kPa. ⋯ Higher cardiac output, lower pulmonary vascular resistance and systemic vascular resistance were measured at f = 11 (inspiration 20%) than at f = 30 (inspiration 50%). An increase in inspiration time by about 100% at the lower ventilatory frequency (f = 11) resulted in a significant but uncompensated decrease in cardiac output and stroke volume. These results demonstrate the value of a rapid insufflation in order to give longer expiration time per minute for the benefit of the venous return and cardiac output.
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Acta Anaesthesiol Scand · Aug 1979
Erythrocyte damage caused by the Haemotherm microwave blood warmer.
Blood units (59) were warmed with the Haemotherm microwave blood warmer and seven units were warmed in a water bath for comparison. The influence of the final blood temperature, the size and the hematocrit of the units on the erythrocyte lesion was studied. Extracellular hemoglobin and potassium, hematocrit, osmotic fragility and mean cellular volume were used as indicators of red cell damage. ⋯ Therefore, erythrocyte concentrates in a Fenwal blood bag should never be warmed by the Haemotherm. The mean plasma hemoglobin increase of the ten whole blood units warmed by the Haemotherm to +36.0-36.8 degrees C was 123 mg/l. The results of the present study indicate that microwaves per se are not harmful to erythrocytes but that poor penetrance of microwaves, together with insufficient blood mixing during warming, are the critical factors leading to hemolysis.
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Acta Anaesthesiol Scand · Aug 1979
Can postoperative pulmonary conditions be improved by treatment with the Bartlett-Edwards incentive spirometer after upper abdominal surgery?
During the immediate postoperative course after upper abdominal surgery, pulmonary complications often occur, caused, inter alia, by reduced regional ventilation and by atelectases as a result of: (1) narrowing of the small peripheral bronchi, and (2) impaired respiratory function. Based on these pathophysiological mechanisms, an instrument (Bartlett-Edwards Incentive Spirometer) has been devised, which aims at giving the patient an opportunity of sustained maximal inspiration under standardized and controlled conditions. ⋯ In general, we have a low frequency of severe postoperative pulmonary complications, as compared with the results reported in the literature. We ascribe this to our very effective pre- and postoperative respiratory therapy.
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Acta Anaesthesiol Scand · Aug 1979
Experimental studies on artificial ventilation using a tidal volume ventilator. Mechanics and dynamics of ventilation.
In 24 piglets (2.7-24.5 kg b.w.), the mechanics of ventilation, the accuracy of dosage of respiratory volumes, and the influence of the ventilator's volume/pressure characteristics (Cvent, "internal compliance") on the dynamic course of insufflation were studied. A linear relationship was shown to exist between tidal volume and end-inspiratory tracheal pressure and between tidal volume and insufflation time. The insufflation time was reduced to about 50% of previously registered values. ⋯ The use of greater power from the ventilator resulted in a significant shortening of the duration of insufflation and vice versa. The duration of insufflation is the parameter of choice in evaluating the efficiency of the ventilatory equipment. When the ventilator's performance is defined, measurements of the duration of insufflation may enable evaluation of conditions within the lungs.
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Acta Anaesthesiol Scand · Aug 1979
Influence of ventilatory frequencies and ventilator volume/pressure quotients on pulmonary ventilation using a tidal volume ventilator.
The influence of ventilatory frequency and the ventilator's "internal state of gas compression" (Cvent) on mechanics of ventilation, pulmonary ventilation, gas distribution, gas exchange and lung perfusion was studied with free airway and experimental regional airway obstruction in 10 piglets (7-12 kg b. w. ), using a tidal volume ventilator. The VDphy/VTexp ratio was greater at f = 30 than at f = 10.3 cycles/min. This could be related to a significant increase in the VDanat/VTexp ratio at f = 30, while VDc/VTexp and VDlav/VTexp were unchanged at both frequencies. ⋯ With Cvent 20, the ventilation of the lung bases was reduced, which was compensated for by a large increase in ventilation within the apical areas of the lungs, while gas distribution within the unobstructed areas was more evenly distributed with Cvent 80. Ventilation at Cvent 20 showed no essential advantage over Cvent 80. Only in lungs extremely difficult to ventilate and with ventilatory frequencies over 50 cycles/min could possible indications for Cvent 20 be seen.