Static and Dynamic Transpulmonary Driving Pressures Affect Lung and Diaphragm Injury during Pressure-controlled versus Pressure-support Ventilation in Experimental Mild Lung Injury in Rats

Abstract

Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New Background Pressure-support ventilation may worsen lung damage due to increased dynamic transpulmonary driving pressure. The authors hypothesized that, at the same tidal volume (VT) and dynamic transpulmonary driving pressure, pressure-support and pressure-controlled ventilation would yield comparable lung damage in mild lung injury. Methods Male Wistar rats received endotoxin intratracheally and, after 24 h, were ventilated in pressure-support mode. Rats were then randomized to 2 h of pressure-controlled ventilation with VT, dynamic transpulmonary driving pressure, dynamic transpulmonary driving pressure, and inspiratory time similar to those of pressure-support ventilation. The primary outcome was the difference in dynamic transpulmonary driving pressure between pressure-support and pressure-controlled ventilation at similar VT; secondary outcomes were lung and diaphragm damage. Results At VT = 6 ml/kg, dynamic transpulmonary driving pressure was higher in pressure-support than pressure-controlled ventilation (12.0 ± 2.2 vs. 8.0 ± 1.8 cm H2O), whereas static transpulmonary driving pressure did not differ (6.7 ± 0.6 vs. 7.0 ± 0.3 cm H2O). Diffuse alveolar damage score and gene expression of markers associated with lung inflammation (interleukin-6), alveolar-stretch (amphiregulin), epithelial cell damage (club cell protein 16), and fibrogenesis (metalloproteinase-9 and type III procollagen), as well as diaphragm inflammation (tumor necrosis factor-α) and proteolysis (muscle RING-finger-1) were comparable between groups. At similar dynamic transpulmonary driving pressure, as well as dynamic transpulmonary driving pressure and inspiratory time, pressure-controlled ventilation increased VT, static transpulmonary driving pressure, diffuse alveolar damage score, and gene expression of markers of lung inflammation, alveolar stretch, fibrogenesis, diaphragm inflammation, and proteolysis compared to pressure-support ventilation. Conclusions In the mild lung injury model use herein, at the same VT, pressure-support compared to pressure-controlled ventilation did not affect biologic markers. However, pressure-support ventilation was associated with a major difference between static and dynamic transpulmonary driving pressure; when the same dynamic transpulmonary driving pressure and inspiratory time were used for pressure-controlled ventilation, greater lung and diaphragm injury occurred compared to pressure-support ventilation.

Noninvasive respiratory support and patient self-inflicted lung injury in COVID-19: a narrative review

“…Due to the shortage of ICU beds during the pandemic, 35 a relatively high number of patients were treated with non-invasive respiratory support for many days even when their clinical status would have required intubation and invasive mechanical ventilation, which may have led to P-SILI. In COVID-19, four potential mechanisms of P-SILI may be suggested: 1) increased lung stress/strain, 36 , 37 , 38 , 39 2) inhomogeneous distribution of ventilation, 4 40 3 ) changes in lung perfusion, 16 23 and 4) patient-ventilator asynchronies during non-invasive positive pressure ventilation (NPPV). 41 42 Increased lung stress/strain …”

Calculation of Transpulmonary Pressure From Regional Ventilation Displayed by Electrical Impedance Tomography in Acute Respiratory Distress Syndrome

“…ARDS requires, indeed, more precise fine-tuned ventilation, since the wide and unpredictable characteristics of the disease, especially the amount of alveolar and interstitial edema, make it difficult to develop a standard that fits all the patients and conditions. Personalizing mechanical ventilation in patients affected by ARDS aims to keep under control different variables, each one affecting the different components of VILI pathophysiology (Nieman et al, 2017 ; Tonetti et al, 2017 ; Pinto et al, 2020 ). DP L is the pressure to which the lung parenchyma is cyclically exposed during tidal breathing and represents the stress applied to the lung, not considering the pressure needed to overcome the chest-wall resistance.…”

Physiological and Pathophysiological Consequences of Mechanical Ventilation

“…Due to limited availability of ICU beds, a relatively high number of patients were treated with noninvasive respiratory support for many days, which may lead to P-SILI. Four potential mechanisms of P-SILI in COVID-19 have been suggested: (1) increased lung stress/strain, 85 (2) inhomogeneous distribution of ventilation, 82 (3) changes in lung perfusion, 86 and (4) patient–ventilator asynchronies during noninvasive positive-pressure ventilation. 87…”