Abstract
Since the introduction of synchronized intermittent mandatory ventilation (SIMV) several advantages have been attributed to this ventilatory mode, one of them being a more homogeneous distribution of ventilation and perfusion than during controlled mechanical ventilation (CMV). Up to now no data are available to confirm whether this is true when SIMV is used in combination with inspiratory pressure support (IPS). Therefor, we compared the influence of CMV and SIMV+IPS on the distributions of ventilation and perfusion in 9 patients undergoing weaning from postoperative mechanical ventilation. Continuous distributions of ventilation and perfusion were assessed using the multiple inert gas elimination technique (MIGET). SIMV+IPS did not induce any change in the hemodynamic or oxygenation parameters, in particular CI and PaO2 remained constant. Physiological dead space\((\dot V_D /\dot V_T )\) increased, but PaCO2 remained unchanged due to increased minute ventilation (from 9.5±0.9l·min−1 to 11.3±1.2l·min−1). The perfusion distributions remained unaltered; there was no change in\(\dot Q_S /\dot Q_T \) nor in the perfusion of the low\(\dot V_A /\dot Q\) lung regions. This result was underscored by the unchanged dispersion of the perfusion distribution (log\(SD\dot Q\)). The increased\(\dot V_D /\dot V_T \) was caused by increased inert gas dead space (from 22.0±9.6 to 26.8±8.7%) which was accompanied by increased ventilation of lung regions with high\(\dot V_A /\dot Q\) ratios (\((10< \dot V_A /\dot Q< 100)\)) in 3 patients. These results show that in our group of patients partial removal of CMV together with pressure support assistance of spontaneous ventilation did not induce a clinically significant loss of the efficiency of the breathing pattern. Since the unchanged hemodynamic parameters were accompanied by increased minute ventilation, arterial blood gases did not deteriorate. Hense, SIMV+IPS proved to be useful for weaning from postoperative mechanical ventilation.
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Downs JB, Klein EF, Desautels D, Modell JH, Kirby RR (1973) Intermittent mandatory ventilatior: a new approach to weaning patients from mechanical ventilators. Chest 64:331–335
Weismann M, Rinaldo JE, Rogers RM, Sanders MH (1983) Intermittent mandatory ventilation. Am Rev Respir Dis 127:641–647
Wolff G, Brunner JX, Grädel E (1986) Gas exchange during mechanical ventilation and spontaneous breathing. Chest 90:11–17
Brochard L, Pluskwa F, Lemaire F (1987) Improved efficacy of spontaneous breathing with inspiratory pressure support. Am Rev Respir Dis 136:411–415
Wagner PD, Saltzmann HA, West JB (1974) Measurement of continuous distributions of ventilation perfusion ratio: theory. J Appl Physiol 36:588–599
Radermacher P, Šantak B, Becker H, Falke KJ (1989) Prostaglandin E1 and nitroglycerin reduce pulmonary capillary pressure but worsen ventilation-perfusion distribution in patients with adult respiratory distress syndrome. Anesthesiology 70:601–606
Wagner P, West JB (1980) Ventilation Perfusion Relationships. In: West JB (ed) Pulmonary gas exchange, vol 1. Academic Press, New York, pp 233–235
Cohen CA, Zagelbaum G, Gross D, Roussos C, Macklem PT (1982) Clinical manifestations of inspiratory muslce fatigue. Am J Med 73:308–316
Lemaire F, Teboul JL, Cinotti L, Giotto G, Abrouk F, Steg G, Maquin-Marier I, Zapol WM (1988) Acute left ventricular dysfunction during successful weaning from mechanical ventilation. Anesthesiology 69:171–179
Torres A, Reyes A, Roca J, Wagner PD, Rodriguez-Roisin R (1989) Ventilation-perfusion mismatching in chronic obstructive pulmonary disease during ventilatory weaning. Am Rev Respir Dis 140:1246–1250
Viale JP, Annat GJ, Bouffard YM, Delafosse BX, Bertrand OM, Motin JP (1988) Oxygen cost of breathing in postoperative patients. Chest 93:506–509
Brochard L, Horf A, Lorino H, Lemaire F (1989) Inspiratory pressure support prevent diaphragmatic fatigue during weaning from mechanical ventilation. Am Rev Respir Dis 139:513–521
Shikora SA, Bistrian BR, Borlase BC, Blackburn GL, Stone MD, Benotti PN (1990) Work of breathing: Reliable predictor of weaning and extubation. Crit Care Med 18:157–162
Nunn JF (1987) Non-respiratory functions of the lung. In: Nunn JF (ed) Applied respiratory physiology. Butterworths, London, pp 284–286
Dantzker DR, Cowenhaven WM, Willoughly WJ, Kirsh MM, Bower JS (1982) Gas exchange alterations associated with weaning from mechanical ventilation following coronary artery bypass grafting. Chest 82:674–677
Beydon L, Radermacher P, Cinotti L, Rekik N, Beloucif S, Lemaire F (1988) Multiple inert gas technique and81mKr/99mTc ventilation perfusion ratio distribution during difficult weaning (abstr). Am Rev Respir Dis 137:141
Pomoppidan H, Loewenstein E (1972) Acute respiratory failure in the adult. N Engl J Med 287:1–26
Froese AB, Bryan AC (1974) Effects of anesthesia and paralysis on diaphragmatic mechanics in man. Anesthesiology 41:242–255
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Supported by Deutsche Forschungsgemeinschaft (Fa 139/1-2)
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Šantak, B., Radermacher, P., Sandmann, W. et al. Influence of SIMV plus inspiratory pressure support on\(\dot V_A /\dot Q\) distributions during postoperative weaning. Intensive Care Med 17, 136–140 (1991). https://doi.org/10.1007/BF01704716
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DOI: https://doi.org/10.1007/BF01704716