Respiratory mechanics in patients with acute respiratory distress syndrome

Abstract

Despite the recognition of its iatrogenic potential, mechanical ventilation remains the mainstay of respiratory support for patients with acute respiratory distress syndrome (ARDS). The low volume ventilation has been recognized as the only method to reduce mortality of ARDS patients and plateau pressure as the lighthouse for delivering safe ventilation. Recent investigations suggest that a ventilation based on lung mechanics (tidal ventilation tailored to the available lung volume able to receive it, i.e., driving pressure) is a successful approach to improve outcome. However, currently available bedside mechanical variables do not consider regional mechanical properties of ARDS affected lungs, which include the role of local stress risers at the boundaries of areas with different aeration. A unifying approach considers lungrelated causes and ventilation-related causes of lung injury. These last may be incorporated in the mechanical power (i.e., amount of mechanical energy transferred per unit of time). Ventilation-induced lung injury (which includes the self-inflicted lung injury of a spontaneously breathing patient) can therefore be prevented by the adoption of measures promoting an increase of ventilable lung and its homogeneity and by delivering lower levels of mechanical power. Prone position promotes lung homogeneity without increasing the delivered mechanical power. This review describes the recent developments on respiratory mechanics in ARDS patients, providing both bedside and research insights from the most updated evidence.

Influence of Positive End-Expiratory Pressure Titration on the Effects of Pronation in Acute Respiratory Distress Syndrome: A Comprehensive Experimental Study

“…Prone position reduced both respiratory system and transpulmonary driving pressures with each PEEP titration technique. MP is a recently introduced measurement, combining several components of VILI in one metric (Tonetti et al, 2017;Russotto et al, 2018); it was not affected by prone positioning in our study, independent of PEEP titration, as it was the case for lung stress. The global lung strain was reduced by pronation only with BP ARDS .…”

Fluctuations of driving pressure during mechanical ventilation indicates elevated central venous pressure and poor outcomes

“…During ARDS, the decrease in lung compliance (C RS ) is attributable to the reduction in the airspace volume due to alveoli collapse as a result of inflammatory cells, fluid, and superimposed pressure, along with impairment of surfactant function. 20 C RS is a marker of disease severity because C RS varies in proportion to the number of aerated and recruitable lung units. 21 Our study further raises the suspect that pathologic pulmonary vascular tension in patients with hypoxia may be further destroyed by inappropriate mechanical ventilation, and revealed as widely range of DP as well as worsen RV function characteristic.…”

Hypercapnia in the critically ill: insights from the bench to the bedside

“…HC was also observed to impair neutrophil phagocytosis and thus alter bacterial clearance [54]. An emerging paradigm here is patient self-induced lung injury (P-SILI), where intense breathing effort may instigate or exacerbate lung injury, and could lead to profoundly different outcomes in ventilated and spontaneously breathing animals (or patients), which might explain some of the increased injury seen [55][56][57][58]. Interestingly, another study of E. coli administration in spontaneously breathing rats showed that HC at 5% for 24 h enhanced inflammation in the lung but reduced inflammation in the spleen [59].…”