Lung protective mechanical ventilation and two year survival in patients with acute lung injury: prospective cohort study

Abstract

Objective To evaluate the association of volume limited and pressure limited (lung protective) mechanical ventilation with two year survival in patients with acute lung injury.Design Prospective cohort study.Setting 13 intensive care units at four hospitals in Baltimore, Maryland, USA.Participants 485 consecutive mechanically ventilated patients with acute lung injury.Main outcome measure Two year survival after onset of acute lung injury.Results 485 patients contributed data for 6240 eligible ventilator settings, as measured twice daily (median of eight eligible ventilator settings per patient; 41% of which adhered to lung protective ventilation). Of these patients, 311 (64%) died within two years. After adjusting for the total duration of ventilation and other relevant covariates, each additional ventilator setting adherent to lung protective ventilation was associated with a 3% decrease in the risk of mortality over two years (hazard ratio 0.97, 95% confidence interval 0.95 to 0.99, P=0.002). Compared with no adherence, the estimated absolute risk reduction in two year mortality for a prototypical patient with 50% adherence to lung protective ventilation was 4.0% (0.8% to 7.2%, P=0.012) and with 100% adherence was 7.8% (1.6% to 14.0%, P=0.011).Conclusions Lung protective mechanical ventilation was associated with a substantial long term survival benefit for patients with acute lung injury. Greater use of lung protective ventilation in routine clinical practice could reduce long term mortality in patients with acute lung injury.Trial registration Clinicaltrials.gov NCT00300248. IntroductionSurvivors of severe critical illness, such as acute lung injury, and its more severe subset, acute respiratory distress syndrome (ARDS), commonly experience increased mortality and morbidity in the months and years after hospital discharge. [1][2][3] Compared with age matched and sex matched controls, patients discharged from intensive care are two to five times more likely to die during three to 15 years' follow-up. 3 Few interventions have been evaluated for improving this increased long term mortality. 4 Randomised trials and meta-analyses have shown that use of volume limited and pressure limited mechanical ventilation (lung protective ventilation) in patients with acute lung injury substantially decreases short term mortality. [5][6][7][8][9] A randomised trial of lung protective ventilation carried out by the ARDS Network 8 found an 8.8% absolute reduction in short term mortality. This trial evaluated a ventilator tidal volume of 6 mL/kg predicted body weight (calculated on the basis of a patient's sex and height 8 ) and a plateau pressure (airway pressure measured after a 0.5 second end inspiratory pause) of ≤30 cm of water compared with a tidal volume of 12 mL/kg predicted body weight and a plateau pressure of ≤50 cm of water. Understanding the effect of lung protective ventilation on long term survival is important, 4 5 especially since critical care interventions with a mortality benefit at hospital dischar...

Recruitment Maneuvers and PEEP Titration

“…In subjects with mild ARDS, the mortality was 27.2% in the higher-PEEP group and 19.4% in the lower-PEEP group (adjusted relative risk 1.37, 95% CI 0.98 -1.92). This analysis suggests that treatment with lower PEEP should be used with mild ARDS, and higher PEEP should be used with moderate and severe ARDS (P aO 2 5. Evidence is not currently available to suggest that one approach to setting PEEP leads to better outcomes than other approaches.…”

“…Subsequent studies have confirmed a survival benefit for low V T ventilation. 5,6 Some studies have reported regional overdistention even with P plat Ͻ30 cm H 2 O, suggesting that there might not be a safe P plat . 7,8 Thus, the lungs should be ventilated with P plat as low as possible.…”

What's Next After ARDS: Long-Term Outcomes

“…DOI: 10.4187/respcare.04644 Studies investigating the long-term outcomes within 1 y after ARDS Weinert (1997) 14 HRQOL: SF-36 6-41 mo (median 15 mo) after diagnosis HRQOL: all domains were below those of general population with similar physical difficulties to out-patients with chronic medical condition, but more deficits in social and mental domains Desai (1999) 19 Radiological findings 110-267 d (mean 196.2 d) CT scan: reticular pattern with anterior distribution was the most frequent abnormality (85% of subjects), related to duration of ventilation Angus (2001) 16 Survival 6-12 mo 55.7 Ϯ 3.7% at 6 with no change at 12 mo Neuropsychological disability Depression, anxiety, or insomnia in 46% of subjects; cognitive impairment in 21% Nöbauer-Huhmann (2001) 20 Pulmonary function 6-10 mo PFT: mild restrictive pattern (33% of subjects), mild obstructive pattern (33% of subjects) Radiological findings CT scan: lung fibrosis in 87% of subjects; lesions were more represented in nondependent lung regions Herridge (2003) 21 Survival 3, 6, and 12 mo after ICU discharge 26 Pulmonary function 6 mo PFT: abnormality in 67% of subjects, restrictive pattern in 58% of subjects; D LCO mild-moderate impairment; 6MWT; 60-65% of predicted distance Radiological findings CT scan: the extent of lung lesion was Ͻ25% of total lung volume in non-dependent regions (continued) and long-term follow-up characterized by a high mortality rate. 18 To quantify this survival gap, Wang et al 28 compared short-and long-term mortality in subjects with ARDS. Hospital mortality was significantly lower (24%) than 1-y mortality after hospital discharge (41%) regardless of the etiology of ARDS.…”

“…[10][11][12] However, patients who survive ARDS remain at risk for mortality and may have persistent morbidity. [13][14][15][16][17][18] This article will review the long-term outcomes after ARDS, focusing on mortality, health-related quality of life (HRQOL), neuropsychological disability, radiological findings, and pulmonary dysfunction (Table 1).…”

Better Ventilator Settings Using a Computerized Clinical Tool

“…Poor compliance with ventilation strategy guidelines/expert opinions can be seen throughout the literature. 9,10 Because the time to irreversible injury is short, prompt recognition of abnormal V T is imperative. 3 Minimizing ventilator-induced lung injury is an integral part of patient care in the modern ICU.…”