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Mechanical Ventilation: A Marker of End of Life?
By Michael Young, MD
Synopsis: This study of outcomes among more than 50,000 elderly Medicare beneficiaries found that activities of daily living and mobility had deteriorated substantially more among those who had been hospitalized the previous year, and that only 27% of those who had received mechanical ventilation were alive 1 year after hospitalization.
Source: Barnato AE, Albert SM, Angus DC, et al. Disability among elderly survivors of mechanical ventilation. Am J Respir Crit Care Med 2011;183:1037-1042.
A recent examination of the Medicare database illustrates that survival rates after in-hospital cardiopulmonary resuscitation (CPR) remained unchanged from 1992 to 2005.1 In fact, the proportion of patients discharged to home after CPR decreased over time. These discouraging results occurred despite the numerous improvements in CPR and ICU care and the development of Rapid Response Teams. Clinician response to these data that confirm poor outcomes after in-hospital CPR appears divided. One perspective is that these findings indicate a compelling need for additional research to develop more effective resuscitation techniques. An alternative view is that the outcomes of CPR will remain poor unless we limit the application of CPR to populations with a better chance of a good outcome.
In a similar fashion, the long-term survival rates of elderly patients who require mechanical ventilation for acute respiratory failure appear disappointing,2 despite many exciting advances in ICU care. These data may be at odds with the impression of many clinicians, patients, and families of the ability of mechanical ventilation to save the lives of our elderly ICU population. When artificial ventilation was first used 60 years ago during the polio epidemic in Scandinavia, the mortality rate of respiratory failure among polio victims dropped from 87% to 40%.3 These impressive results likely helped stimulate the growth of ICU care and the widespread application of mechanical ventilation. In the past two decades, a number of studies have identified patient characteristics that predict higher risk of death among populations of ICU patients who require mechanical ventilation. Less is known about the long-term functional status and quality of life of elderly survivors of mechanical ventilation.
The present study by Barnato et al of Medicare recipients who require mechanical ventilation adds to our understanding of outcomes of mechanical ventilation in the elderly beyond the dichotomous outcome of who lived vs. who died at the time of hospital discharge. Using data from the Medicare Beneficiary Survey from 1996 to 2003, Barnato and colleagues compared the level of disability in the following three groups of patients: 1) patients requiring hospitalization without mechanical ventilation (n = 11,347), 2) patients hospitalized who received mechanical ventilation (n = 534) and 3) patients who were not hospitalized (n = 42,890).
To compare disability levels between groups, the authors use a scoring system that relied on patient-reported mobility and the validated Katz Activities of Daily Living (ADL) Scale score, weighted from 0 (no disability) to 100 (completely disabled). Among patients who received mechanical ventilation, only survivors were used in the study set. The authors also excluded both patients who resided in nursing homes at the time of study entry and patients enrolled in group health plans. Demographic information included age, sex, race, marital status, income, baseline cognitive score, ADL score, and mobility score. The not-hospitalized patients were statistically significantly younger at 76 ± 7 years (SD) vs. the hospitalized patients without mechanical ventilation at 78 ± 7 years, but similar to the hospitalized patients with mechanical ventilation at 76 ± 7 years. The demographic baselines were otherwise similar for all three groups. The time interval between hospital discharge and post-hospital assessment for patients hospitalized with or without mechanical ventilation was a mean of 128 ± 96 and 162 ± 102 days, respectively.
The main outcomes are summarized in Table 1. The ADL disability and mobility difficulty scores worsened among patients who were hospitalized without mechanical ventilation and deteriorated still further among patients who were hospitalized with mechanical ventilation. Among patients who were hospitalized with mechanical ventilation, the death rate was alarmingly high at the time of the outpatient follow-up. Patients who died before the first outpatient follow-up evaluation were censored from analysis. Thus, the true proportion of patients who died within days to several months after receiving mechanical ventilation is likely much higher than the 73% noted in Table 1, above.
Limitations of this study include reliance on patient or family self-reported information to calculate pre- and post-ADL and mobility scores. In addition, the time that the first assessment post-hospitalization occurred varied. The authors also suggest that survivor bias and non-response bias likely underestimates the true magnitude of the post-hospitalization disability. The demographic information available to compare the baselines between the three groups is limited, raising the possibility that important baseline differences between groups exist but were not measured. Also these data do not provide insight into which patient factors predict a higher vs. lower risk of death and disability among patients who received mechanical ventilation. Finally, the number of patients in the group who received mechanical ventilation is limited and the authors did not include sample size calculations to determine the number of patients required to avoid both Type I and Type II errors.
Despite its limitations, this study provides us with at least three important insights. First, it confirms previous observations that mechanical ventilation in the elderly is associated with an extremely high risk of death within days to months of receiving mechanical ventilation. Second, this study indicates that elderly survivors of mechanical ventilation are at great risk to suffer significant increases in disability. Third, this study should prompt investigators to examine populations of elderly patients who receive mechanical ventilation for patient types most likely to benefit from mechanical ventilation and the type of clinical care that reduces the risk of death and significant disability among those who survive.
This study also should stimulate physicians to be circumspect about reflexively providing mechanical ventilation for the elderly. The outcome of mechanical ventilation in the elderly appears worse than the poor outcomes described when dialysis is initiated among residents of nursing homes.4 Although precise comparisons are not available, the risk of death and disability among elderly patients who receive mechanical ventilation appear grossly similar to the extraordinary risk of death and disability of patients who receive inpatient CPR.
If the goal of mechanical ventilation is survival for weeks to months after a stay in the ICU and return to pre-hospital baseline function, from a population perspective, mechanical ventilation is largely a failed therapy. Clearly, we need better science so we may identify the elderly patients most likely to benefit from a trial of mechanical ventilation and a better understanding of the clinical care required to improve the outcomes of elderly patients who receive mechanical ventilation. Arguably, an even higher priority is to provide elderly patients, their families, and clinicians with viable alternatives to mechanical ventilation, which is so often associated with death within days to weeks, or possibly worse, survival with great disability.
1. Ehlenbach WJ, Barnato AE, Curtis JR, et al. Epidemiologic study of in-hospital cardiopulmonary resuscitation in the elderly. N Engl J Med 2009;361:22-31.
2. Wunsch H, Guerra C, Barnato AE, et al. Three-year outcomes for Medicare beneficiaries who survive intensive care. JAMA 2010;303:849-856.
3. Berenson RA. Intensive Care Units (ICUs): Clinical Outcomes, Costs, and Decision-making (Health Technology Case Study 28). Prepared for the Office of Technology Assessment, U.S. Congress, OTA-HCS-28. Washington, DC: November 1984.
4. Kurella Tamura M, Covinsky KE, Chertow GM, et al. Functional status of elderly adults before and after initiation of dialysis. N Engl J Med 2009;361:1539-1547.