By Betty Tran, MD, MSc
Associate Professor of Medicine, Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine, Chicago
SYNOPSIS: In this retrospective, population-based cohort study, patients with frailty spent more time on mechanical ventilation, had longer intensive care unit and hospital stays, and had higher mortality than patients without frailty.
SOURCE: Okahara S, Subramaniam S, Darvall JN, et al. The relationship between frailty and mechanical ventilation. A population-based cohort study. Ann Am Thorac Soc 2022;19:264-271.
Frailty is a clinically recognized state of increased vulnerability to stressors. It is a result of decreased physiologic reserve and function such that a “minor” insult results in a dramatic and disproportionate change in health status.1,2 This study sought to investigate the relationship between frailty and invasive mechanical ventilation given previous mixed findings in this area.
This was a retrospective population-based cohort study using the Australian and New Zealand Intensive Care Society (ANZICS) Adult Patient Database, which includes more than 90% of patients admitted to Australian and New Zealand intensive care units (ICUs). All patients 16 years of age or older requiring invasive mechanical ventilation within the first 24 hours of ICU admission with frailty score documentation were included; only the first ICU admission per hospitalization was counted. Frailty was defined using the Canadian Study of Health and Aging Clinical Frailty Scale (CFS), a clinical judgment-based tool combining comorbidity, cognitive impairment, and disability domains.3 For this study, patients with a CFS score of 4 or lower were defined as nonfrail, while those with scores of 5 or higher were considered frail. The primary outcome was total duration of mechanical ventilation, including all episodes during the same ICU admission. Secondary outcomes included ICU length of stay, ICU mortality, ICU readmission during the hospitalization, hospital length of stay, and hospital mortality.
Overall, 59,319 patients were included in the study analysis. Of these, 14% met criteria for frailty. These patients were older, more likely to be female, had higher illness severity scores, had a higher prevalence of chronic disease (cardiovascular, lung, renal), and were more likely to be admitted for emergent reasons. Patients with frailty had a longer duration of mechanical ventilation compared to non-frail patients (27 [13-81] vs. 16 [7-44] hours; P < 0.001). Frail patients also had longer ICU and hospital lengths of stay and higher ICU and in-hospital mortality. In subgroup analyses, the relationship between frailty and mechanical ventilation differed with age. In patients younger than 60 years, the duration of mechanical ventilation was longer in those with high frailty scores. In contrast, older patients had smaller differences in duration of mechanical ventilation between CFS scores. Specifically, in patients with frailty, the probability of stopping invasive mechanical ventilation increased with every additional decade of age by 4% (hazard ratio [HR], 1.04; 95% confidence interval [CI], 1.02-1.06; P < 0.001). In patients without frailty, this relationship was inverted, with every decade of age decreasing the probability of mechanical ventilation cessation by 6% (HR, 0.94; 95% CI, 0.93-0.95; P < 0.001). Among ICU survivors, younger patients with high CFS scores received a longer duration of mechanical ventilation. Among ICU patients who died during their admission, both younger patients with frailty and older patients without frailty tended to have longer duration of mechanical ventilation.
COMMENTARY
Frailty is common in older adults, but younger patients with chronic diseases, such as advanced malignancy and cirrhosis, also often meet these criteria. Therefore, frailty offers an important construct to better understand functional performance, mobility, and nutritional status prior to ICU admission. The key findings in this study were that frailty was independently associated with a lower probability of cessation of mechanical ventilation, increased mortality, and longer ICU and hospital lengths of stay. The relationship between frailty and mechanical ventilation differed by age, with younger frail patients more likely to receive prolonged mechanical ventilation. Finally, frailty was associated with prolonged mechanical ventilation among ICU survivors but was a less important differentiating factor among those who died in the ICU.
Major strengths of this study included its large cohort of patients in multiple ICUs in two countries, the use of competing risk analyses to address potential confounding factors, and the deliberate analysis of age as an effect modifier on the relationship between frailty and duration of mechanical ventilation (the study’s figure 3 heat map of mechanical ventilation hours by frailty and age groups is particularly insightful). Since this was a retrospective population-level study, data on whether patients were offered re-intubation or reasons for cessation of mechanical ventilation (e.g., liberation following a successful spontaneous breathing trial vs. transition to end-of-life care) are not available. It is possible that younger frail patients were supported with invasive mechanical ventilation for longer based on their age and/or previously stated goals of care compared to older patients who may have transitioned sooner to comfort care-focused measures. In addition, data on noninvasive mechanical ventilation and high-flow oxygen support were not included. Although this may have increased the number of study participants, I suspect it would not alter the key findings.
Considering frailty as a risk factor for prolonged mechanical ventilation will be useful if this information can help identify high-risk patients early in their ICU stay that may benefit from earlier and more intense rehabilitation and ventilator weaning with the goal of improving morbidity and mortality. These data also may help providers during discussions of prognosis and expectations with patients and surrogates as they navigate their ICU stay with the hope of improving communication and aiding in shared decision-making, especially during goals of care discussions.
REFERENCES
- Xue QL. The frailty syndrome: Definition and natural history. Clin Geriatr Med 2011;27:1-15.
- Clegg A, Young J, Iliffe S, et al. Frailty in elderly people. Lancet 2013;381:752-762.
- Rockwood K, Song X, MacKnight C, et al. A global clinical measure of fitness and frailty in elderly people. CMAJ 2005;173:489-495.
In this retrospective, population-based cohort study, patients with frailty spent more time on mechanical ventilation, had longer intensive care unit and hospital stays, and had higher mortality than patients without frailty.
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