Long-Term Outcome

ARDS is characterized by specific morphological changes of the lung with an initial exudative and then a proliferative phase. The exudative phase, maximal during the first week after the onset of ARDS, is characterized by capillary congestion and intra-alveolar edema subsequently followed by alveolar type I cell necrosis. The later repair phase is characterized by intense proliferation of alveolar type II cells and interstitial fibroblasts [24, 25]. This phase can either result in normal tissue resolution or progress toward fibrosis if lung injury is persistent. Fibrosis is rare during the first week of evolution of ARDS. However, it can be observed as early as the second week of evolution, and its prevalence markedly increases beyond the third week after the onset of ARDS, especially in ARDS of pulmonary origin [62]. The patients with fibrosis have more altered lung compliance and more frequently interstitial opacities on chest X-ray [63]. After recovery, they may have more long-term residual pulmonary dysfunction than the others [64]. Patients with many radiologic reticulations on chest CT scan 6 months after hospital discharge had altered total lung capacity, forced vital capacity, and carbon monoxide diffusion capacity [65]. In this last study, a chest CT scan performed 14 days after ARDS onset could predict altered quality of life. However, ARDS survivors who have had fibrosis also had more severe disease and more prolonged duration of mechanical ventilation than the others. Moreover, restrictive pulmonary function can be due not only to pulmonary impairment but also to extrapulmonary complications, such as depression and neuromuscular weakness. Herridge and colleagues have followed ARDS survivors discharged from the hospital for 5 years [66, 67]. Among them, 89% were alive at 1 year and 68% at 5 years. They had normal lung volumes and spirometry measurements by 6 months, but carbon monoxide diffusion capacity remained low, and 6-min walk test was abnormal throughout the 12-month follow-up [66]. At 5 years, pulmonary spirometry was normal or near normal, but patients did not return to normal predicted levels of physical function with persistent exercise limitation and decreased physical quality of life [67]. The median 6-min walk distance was 281 m at 3 months, 422 m at 1 year, and 436 m at 5 years (76% of predicted distance), and, although younger patients had a greater rate of recovery than older patients, neither group returned to normal predicted levels of physical function at 5 years. Health- related quality of life was mainly altered due to extrapulmonary complications. Actually, muscle weakness and fatigue were the main reasons for their functional limitation [66-68]. Moreover, 1 or 2 years after ARDS, the majority of survivors present with clinically significant general anxiety, depression, and posttraumatic stress disorder symptoms [69] and even sometimes psychiatric symptoms [70] Short- and long-term quality of life is markedly altered in ARDS survivors [71] and seems more altered at 12 months than in other critically ill patients with similar severity but without ARDS during their ICU stay [72]. However, in another study, the quality of life was similar between ARDS and non-ARDS patients, and functional status at 6 months after hospitalization could be largely explained by baseline condition [73].