Definition and epidemiology of acute respiratory distress syndrome

Abstract

Fifty years ago, Ashbaugh and colleagues defined for the first time the acute respiratory distress syndrome (ARDS), one among the most challenging clinical condition of the critical care medicine. The scientific community worked over the years to generate a unified definition of ARDS, which saw its revisited version in the Berlin definition, in 2014. Epidemiologic information about ARDS is limited in the era of the new Berlin definition, and wide differences are reported among countries all over the world. Despite decades of study in the field of lung injury, ARDS is still so far under-recognized, with 2 out of 5 cases missed by clinicians. Furthermore, although advances of ventilator strategies in the management of ARDS associated with outcome improvements-such as protective mechanical ventilation, lower driving pressure, higher PEEP levels and prone positioning-ARDS appears to be undertreated and mortality remains elevated up to 40%. In this review, we cover the history that led to the current worldwide accepted Berlin definition of ARDS and we summarize the recent data regarding ARDS epidemiology.

Prevention and treatment of acute lung injury with time-controlled adaptive ventilation: physiologically informed modification of airway pressure release ventilation

“…The ARDSnet Low Vt (LVt) method is intended to protect the non-dependent normal lung tissue from overdistension (OD) and reduce alveolar recruitment/ derecruitment (R/D) with positive end expiratory pressure (PEEP), while resting severely injured tissue by allowing it to remain collapsed throughout the ventilation cycle [2]. However, this strategy has not further reduced ARDS mortality [1,[3][4][5][6][7][8][9][10][11]. This suggests that our understanding of ARDS pathophysiology remains [12] all using the airway pressure release ventilation (APRV) mode but with different methods: a Stock et al used a CPAP phase that encompassed 60% of each breath, a release phase of 1.27 s and a respiratory rate (RR) of 20/min [98]; b Davis et al decreased the respiratory rate by prolonging both the CPAP and release phase [99]; c Gama de Abreau et al adjusted their CPAP and release phase to values typical of a conventional breath [100]; d Roy et al minimized the release phase and extended CPAP to occupy 90% of each breath, typical of the time-controlled adaptive ventilation (TCAV) method [83].…”

“…The current understanding is that open and collapsed tissues are not delineated into compartments, but are rather intermingled throughout the entire lung [17][18][19][20][21]. The unchanged mortality associated with the LVt method may also reflect the fact that maintaining lung tissue collapse ("resting") may not be protective [1,[3][4][5][6][7][8][9][10][11]. The atelectatic lung does not exchange gas, is susceptible to pneumonia, and may ultimately lead to collapse induration and fibrosis with the inability to re-inflate or epithelialize the airspace [22][23][24].…”

“…Current ARDS treatment is supportive: protective mechanical ventilation, typically using lower tidal volume ventilation (Vt) and low-moderate positive end expiratory pressure (PEEP) [2]. Unfortunately, current protective ventilation strategies have not lessened ARDS mortality rate [1,[3][4][5][6][7][8][9][10][11]. The determinant of VILI is not the "mode" of ventilation, but the way parameters of the mechanical breath are set and combined.…”

Medical Conditions

“…AHRF which represents a common end-point to multiple pathological processes either local or systemic may have many medical conditions as aetiology. We can divide more or less the main determinants into two categories: pulmonary and extrapulmonary [2]. Table 11.1 listed the common causes of AHRF.…”

“…Moreover, some demographic and environmental risk factors are related to the development of ARDS. These include older age and specific genetic variants [2,6]. In this chapter, we review the medical diseases associated with AHRF and the related treatment options.…”