Journal of applied physiology
-
Tidal volume delivered by mechanical ventilation to a sedated patient is distributed in a nonphysiological pattern, causing atelectasis (underinflation) and overdistension (overinflation). Activation of the diaphragm during controlled mechanical ventilation in these sedated patients may provide a method to reduce atelectasis and alveolar inhomogeneity, protecting the lungs from ventilator-induced lung injury while also protecting the diaphragm by preventing ventilator-induced diaphragm dysfunction. We studied the hypothesis that diaphragm contractions elicited by transvenous phrenic nerve stimulation, delivered in synchrony with volume-control ventilation, would reduce atelectasis and lung inhomogeneity in a healthy, normal lung pig model. ⋯ NEW & NOTEWORTHY Temporary transvenous diaphragm neurostimulation has been shown to mitigate diaphragm atrophy in a preclinical model. This study contributes to this work by demonstrating that diaphragm neurostimulation can also offer lung protection from ventilator injury, providing a potential solution to the dilemma of lung- versus diaphragm-protective ventilation. Our findings show that neurostimulation on every breath preserved [Formula: see text]/[Formula: see text], end-expiratory lung volume, alveolar homogeneity, and required lower pressures than lung-protective ventilation over 50 h in healthy pigs.
-
Regional viscoelastic properties of thoracic tissues in acute respiratory distress syndrome (ARDS) and their change with position and positive end-expiratory pressure (PEEP) are unknown. In an experimental porcine ARDS, dorsal and ventral lung (R2,L and E2,L) and chest wall (R2,cw and E2,cw) viscoelastic resistive (R) and elastic (E) parameters were measured at 20, 15, 10, and 5 cmH2O PEEP in supine and prone position. E2 and R2 were obtained by fitting the decay of pressure after end-inspiratory occlusion to the equation: Pviscmax (t) =R2 e-t/τ2, where t is the length of occlusion and τ2 time constant. ⋯ Prone position tended to decrease lung viscoelastic resistive component. PEEP had a significant effect on dorsal lung viscoelastic elastance. Finally, lung viscoelastic resistance correlated with the amount of lung collapse assessed by electrical impedance tomography.