S3P4Q14EA1 by sladner


									Title: Clinical Epidemiology of Acute Lung Injury and Acute Respiratory Distress Syndrome: Incidence, Diagnosis and Outcomes
Authors: Avecillas JF, Freire AX, Arroliga AC
Clinics in Chest Medicine 2006; 27(4):549-57

Key Points
    •    A wide range of incidence is reported for ALI/ARDS, depending on the clinical definitions used, cultural, demographic and socioeconomic
         differences in study populations, different study periods, and different study designs.
    •    Clinical diagnosis is problematic, with variations in timing and methodology of applying clinical tests such as chest xray and pulmonary
         capillary wedge pressure.
    •    Mortality from ARDS/ALI appears in some, but not all studies to be declining.
    •    Survivors have long term disabilities, including physical and neurocognitive disabilities that have not been well studied and have
         implications for future treatment.

Clinical Conclusions

Mortality rates from ALI/ARDS vary greatly, due to a heterogeneity of patients, illness and treatments. Better training and standards in clinical
measurements, such as PCWP, may improve interobserver variability and improve the ability to study treatments and outcomes from ARDS.
Survivors of ARDS require long-term rehabilitation from both physical and neurocognitive problems they incur after ARDS treatment: this problem
is likely to grow as the number of survivors of ARDS/ALI increases.

Section Highlights
     Incidence [Table 1]
          •    Estimates of ARDS/ALI have varied from 1.5 to 8.3 cases per 100,000 persons, depending on the population studied and the
               definitions of ALI and ARDS used.
          •    Using 1994 definitions of ALI/ARDS developed by the American European Consensus Conference (AECC) on ARDS the incidence has
               been estimated of 64.2 cases per 100,000 person-years. A crude incidence in another study was 58.7 cases per 100,000 person-
          •    The highest incidence of ARDS appears to occur in sepsis and with multiple transfusions, and the lowest incidence in trauma and
               patients with drug overdose.
     Diagnosis [Table 2]
          •    Pathological diagnosis of diffuse alveolar damage is the standard for diagnosis of ALI/ARDS
          •    Open lung biopsy in selected patients appears safe and alters therapy in up to 60% of cases.
          •    Limitations of the AECC definitions include variability in interpretation of chest xrays, wide clinical variation in measuring pulmonary
               capillary wedge pressure (PCWP) and variability in the timing of measurement of PaO2/FiO2 ratio or chest xray, which might impact
               patient selection for various clinical studies. Some authors have challenged the use of a PAWP of < 18 mm Hg as a cutoff to rule out
               heart failure.


           •    Reported mortality rates from 23-71%. [Table 3]
           •    Overall mortality rates have improved during the last 20 years, ranging from 29-42%.
           •    However some reports show constant, not declining, mortality rates

          •     Most ALI/ARDS survivors present with moderate-to-severe pulmonary impairment with low forced vital capacity (FVC), forced
                expiratory volume at 1 sec (FEV1), FEV1/FVC ration, total lung capacity (TLC) and carbon monoxide diffusing capacity (DLCO).
                Pulmonary function improved substantially 3 months after extubation, with additional slight improvement at 6 months.
             •   Herridge and colleagues showed that patients studied 3, 6 and 12 months after ICU discharge had functional limitations due to
                 muscle wasting and weakness, entrapment neuropathy, heteroptopic ossification, and decreased lung function. Determinants of
                 inability to exercise during 1 year follow up included use of steroids in the ICU, presence of illness acquired in the ICU, rate of
                 resolution of lung injury and multiorgan dysfunction as measured by changes in Lung Injury Score and Multiple Organ Dysfunction
             •   Many patients have impaired memory, attention, concentration, mental processing speed, and global intelligence decline, that
                 persists for 2 years.
             •   Up to 27.5% of ARDS survivors suffer from post traumatic stress disorder.


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