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 (functional residual capacity) resulting in re-opening 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 ventilation/perfusion ratio in the diseases lungs is normalized and the intrapulmonary shunting of venous blood (Qs/Qt) will decrease. At the same time the dead space ventilation fraction (VD/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 PVO2 will fall and VD/VT will increase. Increasing hyperinflation 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).

Practice of Excessive FIO2 and Effect on Pulmonary Outcomes in Mechanically Ventilated Patients With Acute Lung InjuryThe authors respond to: Practice of Excessive FIO2 and Effect on Pulmonary Outcomes in Mechanically Ventilated Patients With Acute Lung Injury

“…The risks were explained in studies from several years ago. 2,3 The conclusion in this trial was that managing V D /V T may be clinically useful, but that particular parameter was one of the least statistically significant in their Table 2.…”

“…Therefore, treating the anemia or low cardiac output should be done first, and mild hypoxemia may be acceptable in some situations, as reported by Martin et al 3 They suggested that hypoxia triggers a complex network of cellular signaling pathways that may result in protective responses. 3 Protocol-driven F IO 2 titration should be combined with a clear understanding that high F IO 2 We thank Dr Alkhuja and Ms Duffy for reviewing our paper, their thoughtful insight about the physiology of oxygen delivery, and their call for education of health care staff about the same. We agree with their ideas about optimization of cardiac output and anemia for increasing oxygen delivery when required to do so.…”

D1/D2-dopamine receptor agonist dihydrexidine stimulates inspiratory motor output and depresses medullary expiratory neurons

“…Lung inflation activates vagal pulmonary afferents (1) that promote dopamine release in the brain stem (13). An increase in lung volume also results in vagally mediated inhibition of expiratory muscle activity, which can increase FRC (39) and VPR (45). Thus when metabolic demand and CO 2 production increase inspiratory effort, suppression of expiratory motor output might improve chest wall compliance with favorable consequences on FRC and VPR.…”

Dose‐response comparisons of five lung surfactant factor (LSF) preparations in an animal model of adult respiratory distress syndrome (ARDS)

“…The differences between the protein-free and the protein-containing LSF preparations were even more pronounced if dose-response comparisons were performed based on the Pao2 values during the 2nd PEEP reduction. It is well known that PEEP by itself has beneficial effects on oxygenation (Stokke, 1976). Thus, if a moderately active LSF like Exosurf or PL-LSF is combined with ventilation under high PEEP, it is possible to re-establish gas exchange in the lung (Rider et al, 1992).…”