Review: Artifical ventilation with positive end-expiratory pressure (PEEP)

Abstract

CPPV (continuous positive pressure ventilation) is obviously superior to IPPV (intermittent positive pressure ventilation) for the treatment of patients with acute respiratory insufficiency (ARI) and results within a few minutes in a considerable increase in the oxygen transport. The principle is to add a positive end-expiratory plateau (PEEP) to IPPV, with a subsequent increase in FRC (func-tional residual capacity) resulting in reopening in first and foremost.the declive alveolae, which can then once again take part in the gas exchange and possibly re-commence the disrupted surfactant production. In this manner the venti!ation/perfusion ratio in the diseased lungs is normalized and the intrapulmonary shunting of venous blood (Qs/Qt) will decrease. At the same time the dead space ventilation fraction (Vo/VT) normalizes and the compliance of the lungs (CL) increases. The PEEP value, which results in a maximum oxygen transport, and the lowest dead space fraction, also appears to result in the greatest total static compliance (CT) and the greatest increase in mixed venous oxygen tension (PVo2); this value can be termed "optimal PEEP". The greater the FRC is, with an airway pressure = atmospheric pressure, the lower the PEEP value required in order to obtain maximum oxygen transport. If the optimal PEEP value is exceeded the oxygen transport will fall because of a falling Qt (cardiac output) due to a reduction in venous return. CT and PV02 will fall and Vo/VT will increase. Increasing hyperinfiation of the alveolae will result in a rising danger of alveolar rupture. The critical use of CPPV treatment means that the lungs may be safeguarded against high oxygen percents. The mortality of newborn infants with RDS (respiratory distress syndrome) has fallen considerably after the general introduction of CPPV and CPAP (continuous positive airway pressures). The same appears to be the case with adults suffering from ARI (acute respiratory insufficiency). Abbreviations and Explanations (A-a) DO 2 = Alveolo-arterial-0 2-difference C L ARI = Acute respiratory insufficiency C T CaO2 = Arterial O2-content CVO 2 CaO 2-0702 = O2-extraction ratio ETP CaO2 ERV (CaO2-CvO2) x ()t = "QO2 = O2-uptake, consumption FRC CC = Closing capacity IC CV = Closing volume IPPV CPAP = Continuous positive airway pressure CPPV (IPPV + PEEP) = Continuous positive pressure ventilation IRV = Lung compliance = "Total static compliance" = Mixed venous O2-content ("02-reserve") = End Tidal point = Expiratory reserve volume = Functional residual capacity = Inspiratory capacity = Intermittent positive pressure ventilation = Inspiratory reserve volume 78 MABP MAP PaCO 2 PaO 2 PEEP [hTO 2 PVR 0S/t~t 0t RAW RDS RV TLC VE VD VD/VT VT Heart work (W) ZEEP = Mean arterial blood pressure = Mean airway pressure = Arterial CO2-tension = Arterial O2-tension = Positive end-expiratory pressure = Mixed venous O2-tension = Pulmonary vascular resistance = "Wasted perfusion", lung shunt in fraction of Qt = Cardiac output = Airway resistance = Respiratory distress syndrome = Residual volume = Total lung capacity = Alveolar ventilation = Physiologic dead space = "Wasted ventilation", dead space ventilation in fraction of tidal volume = Tidal volume = Qt x MABP = Zero (ambient) end expiratory pressure .