key: cord-0985398-fd0jhxgo
authors: Sison, Stephanie M.; Sivakumar, Gayathri K.; Caufield-Noll, Christine; Greenough, William B.; Oh, Esther S.; Galiatsatos, Panagis
title: Mortality outcomes of patients on chronic mechanical ventilation in different care settings: A systematic review
date: 2021-02-13
journal: Heliyon
DOI: 10.1016/j.heliyon.2021.e06230
sha: dedb1d18dcc384192ca4b7fab9a0dd5c8f3381a6
doc_id: 985398
cord_uid: fd0jhxgo

OBJECTIVES: To determine the outcomes of chronically ventilated patients outside the setting of intensive care units. DESIGN: Systematic review. SETTING AND PARTICIPANTS: Studies evaluating patients on chronic invasive mechanical ventilation in different care settings. METHODS: A systematic literature search of the PubMed, Embase, Cochrane Library, CINAHL (EBSCOhost), LILACS and Scopus databases from inception to March 27, 2020. Studies reporting mortality outcomes of patients ≥18 years of age on chronic invasive mechanical ventilation in intensive care units and other care settings were eligible for inclusion. RESULTS: Sixty studies were included in the systematic review. Mortality rates ranged from 13.7% to 77.8% in ICUs (n = 17 studies), 7.8%–51.0% in non-ICUs including step-down units and inpatient wards (n = 26 studies), and 12.0%–91.8% in home or nursing home settings (n = 19 studies). Age was associated with mortality in all care settings. Weaning rates ranged from 10.0% to 78.2% across non-ICU studies. Studies reporting weaning as their primary outcome demonstrated higher success rates in weaning. Home care studies reported low incidences of ventilator failure. None of the studies reported ventilator malfunction as the primary cause of death. CONCLUSIONS AND IMPLICATIONS: Mortality outcomes across various settings were disparate due to methodological and clinical heterogeneity among studies. However, there is evidence to suggest non-ICU venues of care as a comparable alternative to ICUs for stable, chronically ventilated patients, with the additional benefit of providing specialized weaning programs. By synthesizing the global data on managing chronically ventilated patients in various care settings, this study provides health care systems and providers alternative venue options for the delivery of prolonged ventilatory care in the context of limited ICU resources.

Advances in critical care medicine and the application of invasive mechanical ventilation in the intensive care unit (ICU) have led to improved short-term survival and mortality outcomes in acutely critically ill patients [1] . With the increase in the number of ventilator-dependent individuals, there have been concerns about equitable access to ICU resources for critically ill patients, particularly the duration of ventilatory support warranted for such patients.

Acute respiratory failure due to severe acute respiratory coronavirus 2 (SARS-CoV-2) has led to an unprecedented rise in the number of critically ill patients requiring invasive mechanical ventilation, predominantly among older adults and those with multiple comorbidities [2] . In the current scientific literature, rates of invasive mechanical ventilation range from 2% to 47% in patients infected with coronavirus 2019 [3, 4, 5] . Guidelines and recommendations on the management of tracheostomy in patients requiring mechanical ventilation during the COVID-19 pandemic have been published [6] . Although the data is still emerging on the average duration of intubation among COVID-19 patients, some studies report mechanical ventilator support for a median of 18 days (IQR 9-28) to a maximum of 31 days [7, 8] . As the growing incidence of COVID-19 strains the very limits of resource capacity in intensive care units and as healthcare providers are forced to make burdening decisions regarding patient care, it is becoming increasingly important to understand whether ventilator support can be provided safely in alternate clinical settings, particularly for patients requiring longer durations of mechanical ventilation.

In the past, chronically ventilated patients have been transitioned to various alternative care settings after stabilization of a critical illness to prevent overutilization of critical care resources [9, 10] . Depending on the availability of resources such as infrastructure and technology in different regions of the world, patients are transitioned outside of the ICU to general medical or surgical units, specialized respiratory units, subacute facilities, long-term care facilities such as nursing homes (NH), or home care [1, 11] . In some instances, patients remain in the ICU for extended periods when a healthcare system is unable to provide complex care for ventilated patients in a non-ICU setting [12] .

In 1998, clinical guidelines regarding the management of chronically ventilated patients outside the ICU was published where experts outlined the criteria for ICU discharge and described characteristics of potential alternative care settings. Albeit clinical outcomes of chronically ventilated patients in alternative care settings were discussed briefly, the need for comprehensive survival-and mortality-related data collection from various care settings was broadly acknowledged [11] . While many studies have since published on this topic, there are no systematic reviews examining the mortality outcomes across different care settings to date [13] .

Given that some countries have yet to reach the peak of the COVID-19 pandemic, and as the risk of outbreak recurrence remains, it is critical to review and synthesize available evidence on clinical outcomes associated with chronic mechanical ventilation in care settings outside of the intensive care unit and provide healthcare providers and healthcare systems guidance on optimizing ventilatory care for patients. We aim to systematically review mortality outcomes of chronically ventilated patients across various care settings to determine the safety of chronically ventilated patients. Additionally, as older adults have been disproportionately impacted by COVID-19, we examined reported mortality outcomes of older mechanically ventilated patients in care settings outside of the ICU.

This systematic review was conducted and reported in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement [14] .

An electronic search of the PubMed, Embase (Embase and Embase classic), Cochrane Library, CINAHL (EBSCOhost), LILACS, and Scopus databases, from inception to March 27, 2020, were completed. A combination of keywords and controlled vocabulary terms was used and divided into two distinct search themes. The first theme related to any medical condition requiring chronic or prolonged mechanical ventilation and included the following terms: artificial respiration, mechanical ventilation, and chronic or prolonged mechanical ventilation. Venues of care formed the second concept of our research framework and were identified with the following terminology: health care delivery, home health care, home care, chronic disease hospitals, care venues, community or long-term care, intermediate units, nursing home, chronic ventilator units, and step-down units. The search strategy from all databases is detailed in Supplementary Table S1 . Reference lists of included studies were hand-searched to identify additional relevant articles.

Two reviewers (S.M.S and G.K.S) independently reviewed all titles and abstracts. Studies were then further assessed for relevance and selected for full-text review if they met the inclusion criteria. Covidence, an online data extraction tool, was used to screen and select studies for inclusion.

Studies were included for the following criteria: i) a majority of the study cohort were aged 18 years with at least 50% of the study population invasively ventilated; ii) clearly identified care setting; and iii) mortality while admitted in the specified care setting was reported. All studies using iterations of the terms 'chronic,' 'prolonged,' 'long-term,' or 'dependent' (e.g., ventilator-dependent) mechanical ventilation to describe the study population were included. The authors agreed upon this criterion to account for various ventilation lengths considered as "prolonged" which can range from as short as 24 h to as long as 14-21 days [15] .

Studies were restricted to original research published in the English language. Review articles, abstracts, conference proceedings, editorials, and opinion pieces were excluded. If the reported mortality outcome was related to the investigation of a specific intervention, the study was excluded. However, weaning was an exception to this rule if it was inherent to the services offered by the care setting.

Standardized abstraction forms were created a priori to extract relevant information according to the research objectives. Two independent reviewers (S.M.S. and G.K.S.) conducted the data extraction. Retrieved data included the author, year of publication, geographic location, care setting, study characteristics including study design and minimum ventilation requirement of the cohort, and population characteristics including age, duration of ventilation and sample size. Additional information, including characteristics of non-ICU care settings and underlying cause of respiratory failure, were extracted for comprehensive data analysis. The mortality rate was the primary outcome measure. If mortality rate was not reported, the number of deaths in a given sample was extrapolated to determine the rate. Secondary outcomes included risk factors for mortality and other commonly reported outcomes which may reflect the safety of the care setting. Risk factors significantly associated with mortality using multivariable analysis were collected if the association was found in at least two studies. Disagreements and discrepancies between reviewers were resolved through discussion and consensus.

Study quality was evaluated by two reviewers (S.M.S. and G.K.S.) using the National Institute of Health (NIH) Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies [16] . All discrepancies in study ratings were resolved in a consensus meeting. Eligible studies were not excluded based on overall study quality.

Our search yielded 3,990 titles and references from electronic databases. Eleven additional studies were included from hand searches. After duplicate studies were removed, 2,689 abstracts were screened, and 410 full-text articles were assessed for study eligibility. A total of 60 studies were included for qualitative synthesis ( Figure 1 ). Table 1 provides an overview of the characteristics of the 60 included studies [9, 10, 12, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73] . Three major care settings were identified among selected studies: 1) ICU; 2) step-down units or wards, also referred to as 'non-ICU' settings; and 3) home or nursing home [11] . Studies on non-ICU settings were primarily from North America and Europe, while studies on ICU and home care were globally distributed. Among the 60 full-text articles, 28 studies reported mortality as their primary outcome measure.

The methodological assessment of included studies is detailed in Supplementary Table S2 . Fifty-three studies were determined to have a 'fair' or 'good' study quality as per the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. The remaining seven studies were deemed to be of inadequate methodological rigor but were still included in the qualitative analysis.

Patient characteristics and mortality outcomes by ICU, non-ICU, and home/NH settings are presented in Tables 2, 3 , and 4. Fourteen out of 17 (82%) ICU and 21 out of 26 (81%) non-ICU studies reported a mean or median age of 60 years or older. Subjects in the home/NH study cohort tended to be younger, with only 9 out of 18 (50%) of the studies reporting a mean or median age of 60 years or older (Tables 2, 3 , and 4).

The minimum duration of ventilation of patients for inclusion in ICU studies ranged from 2 to 21 days. Most non-ICU studies required a ventilation duration of 14 days, except for one study [44] . While the ventilation requirements for home care/NH-based studies were not always reported, a majority of studies reported a minimum ventilation duration of 12 months (Tables 2, 3, and 4). Additionally, studied non-ICU and home/NH settings had their own criteria for admission which influenced characteristics of cohorts. Many non-ICU settings required patients to be hemodynamically stable without the need for pressors and have a tracheostomy with a ventilation requirement of FiO 45% and PEEP 8 [31, 37, 41, 46, 51, 60, 72] . Other non-ICU settings had additional requirements such as absence of multi-organ failure [66] , dialysis requirement [19, 60, 66] , uncontrolled infection [10, 40, 51, 60] , invasive or continuous monitoring needs [34, 51, 60, 69, 72] , and presence of rehabilitation potential [22, 34, 37, 38, 40, 60, 64, 65, 66] . Only Carson et al. [23] which had a mortality rate of 49.6%, had a liberal criterion accepting patients on vasopressors. Similar to many of the non-ICU settings, patients needed to be medically stable for home transfer, although specific details were not provided by any of the home care studies. Mortality rates across different care settings ranged broadly from 13.7% to 77.8% in ICUs (Table 2) , 7.8%-51.0% in non-ICUs (Table 3) , and 12.0%-91.8% in home/NH settings (Table 4 ). Among studies reporting data from home/NH settings, studies with longer follow-up durations reported higher mortality rates.

Six studies, which specifically examined outcomes of older adults, identified an expansive range of mortality outcomes [9, 17, 28, 34, 38, 45] . Abita gao glu [17] and Seneff et al. [9] reported mortality rates of 9.8% and 51.0% among ventilated patients aged 60 years in the ICU and step-down unit, respectively. An ICU study of patients aged 80 years old reported one of the highest mortality rates (77.8%) [28] . In comparison, studies of octogenarians in non-ICU settings reported mortality rates of 5.3% [38] , 21.8% [45] , and 27% [34] but the minimum length of ventilation differed between ICU and non-ICU studies.

Age was the most frequently studied risk factor for mortality across all care settings. A total of 6 studies (3 ICU [29, 30, 59 ] and 3 non-ICU [34, 45, 51] ) examined age as a risk factor for short-term, in-patient mortality. Among these studies, only 2 ICU [29, 30] studies reported an association between increasing age and higher mortality. A total of 19 studies (7 ICU [24, 29, 33, 42, 43, 47, 52] , 9 non-ICU [9, 20, 23, 35, 38, 40, 51, 66, 69] and 3 home care [18, 49, 63] ) examined the association between age and long-term mortality. Of these, 5 ICU [24, 29, 42, 43, 47] , 7 non-ICU [9, 20, 23, 38, 40, 66, 69] and 1 home care [18] studies reported significantly higher long-term mortality in older age groups. Fifteen these studies examined mortality up to 1-year while the rest had 6 months to 5 years follow-up time [9, 35, 66, 69] .

APACHE [74] and SAPS [75] scores, despite being measures of ICU mortality risk, were studied and were found to be associated with both short-term and long-term mortality in ICU [30, 43] and non-ICU studies [9, 45, 51] . Scores were obtained on admission to the studied care setting. Other risk factors associated with short-and long-term mortality in ICU studies included an immunocompromised state [29, 30] , respiratory disease as a cause of admission [30, 42] , low platelet counts [24, 52, 59] , presence of organ dysfunction [24, 29, 30, 47, 59] , and vasopressor use [24, 47, 59] . The latter three variables were collected at day 21 of mechanical ventilation. In non-ICU studies, low albumin level [45, 51] was associated with short-term mortality. In contrast, etiology of acute illness [9, 20, 51] and weaning outcome at the non-ICU setting [20, 66] were associated with long-term mortality. For home care or NH settings, only one study identified a risk factor associated with mortality heart failure or cerebrovascular disease as an underlying diagnosis [18] .

Weaning outcomes were reported in 20 out of 26 (77%) of non-ICU studies [10, 19, 20, 22, 23, 26, 31, 34, 37, 38, 40, 41, 46, 51, 56, 57, 60, 64, 65, 66] . Weaning rates, or the percent of the study subjects that achieved successful weaning, ranged from 10.0% to 78.2%. The criteria for successful weaning varied considerably across these studies. If the definition of "weaned" included patients who continue to require non-invasive ventilation (NIV), the weaning rates were between 61.3% to 78.2% [22, 40, 66] . However, these rates dropped to a range of 25.3%-59.9% if ongoing use of NIV was not a criterion for a successful wean [31, 34, 37, 56, 57, 60, 65] . Additionally, successful weaning rates varied greatly depending on the minimum duration of time a patient needed to be ventilator-independent to be labelled as "weaned." Studies requiring 48 h [26, 34] or 7 days [19, 64, 66] of spontaneous breathing had weaning rates between 59.9%-67.5% and 32.0%-61.3%, respectively. If the weaning criteria required spontaneous breathing up to discharge [10, 20, 51, 56] , weaning rates ranged between 37.9% to 68.7%. Numerous studies with weaning as the primary outcome excluded patients identified as irreversibly ventilator dependent. Such studies [20, 22, 26, 34, 37, 38, 40, 60, 65, 66] had higher rates of weaning (43.0%-78.2%) compared to studies with weaning as a secondary outcome and with liberal inclusion criteria (10.0%-68.7%) [19, 23, 31, 41, 46, 51, 56] . Ten [21, 39, 49, 54, 55, 61, 62, 63, 71, 73] out of 19 (52%) home care/NH studies reported on hospitalization and complications rates. Chronically mechanically ventilated patients in home care settings requiring at least one hospitalization ranged between 44.1% to 60.0% [49, 61, 63, 73] . However, when examined for a follow-up period of one-year, Sancho et al. [63] and Rose et al. [61] calculated a mean hospitalization per patient of only 0.82 (SD 0.98) and 1.7 (SD 2.9), respectively; and Guber et al. [39] demonstrated that patients were admitted to the hospital for an average of 3.3 days annually. Additionally, patients on home mechanical ventilation spent more than 94% of their time outside of the hospital [21] or were hospital-free for about 1.1 years [61] .

Ventilator malfunction was among the cited reasons for hospitalization in 7.7% [55] to 28.6% [73] of home care patients. Other studies [54, 62] reported ventilator failure as a cause of complication but did not state whether these patients required hospitalization. For example, Muir et al. [54] identified ventilator failure as the cause of acute respiratory failure in 3.9% (4/102) of patients, while Saiphoklang and colleagues [62] reported ventilator failure as a complication in 1.9% of cases (1/53). None of the home care studies reported ventilator malfunction as a primary cause of death [12, 49, 55, 62, 73] , except for Fischer et al. [36] , in which ventilator failure was not ruled out as a cause of cardiac arrest in one patient. Lastly, pulmonary infection (e.g., pneumonia) was the most common medical complication in patients ventilated at home [49, 54, 62, 63, 73] . Other reported complications included tracheostomy-related problems, such as loose tracheostomy, tracheostomy stenosis/granulation tissue formation [49, 54, 62, 63] , and pneumothorax [54, 62, 73] .

This systematic review synthesizes the global experience of managing care of chronically ventilated patients in and outside of ICU settings. In light of the ongoing COVID-19 pandemic, the identification and consideration of other care venues for delivering high-quality ventilatory support for patients is warranted, particularly in resource-strained ICU settings. We observed that while mortality outcomes within and between care settings were disparate, mortality outcomes of patients in non-ICU studies were crudely comparable to those in intensive care units. Interestingly, mortality rates due to ventilator failure were low in home care, demonstrating the future potential of home care as an alternate care venue. Older age was identified as a key risk factor for mortality across all care settings.

Our main study limitation is the considerable clinical heterogeneity among included studies. Clinical characteristics related to study populations such as age and disease etiology, as well as differences in facility staffing, admission criteria and care objectives, varied broadly among included studies. In addition, factors including total ventilation duration and illness acuity or severity inevitably contributed to disparities in mortality outcomes. Although a meta-analysis of included studies was (11) Total MV duration** PMV: 27 (22) 38 (14.5) LOS, length of stay; MV, mechanical ventilation; NR, not reported; PMV, prior duration of mechanical ventilation. * Values are presented as mean (SD) unless otherwise specified. If the range or IQR was not stated, only the mean or median was reported.

y Tracheostomy must be in place for at least one week before a subject is transferred.

z Subjects were presented in subcategories; the mean (range) was reported for each subcategory. For simplified data presentation, only the range of reported values has been shown.

x Length of prior mechanical ventilation was only given for 40 subjects who were admitted for weaning.

|| Denominator used to calculate the mortality rate was 1,414 instead of 1,419. not possible due to significant heterogeneity, the strength of this systematic review lies in the rigorous synthesis of the care and outcomes of chronically ventilated patients in different care settings across the globe. Our most notable finding was discovering evidence that suggest safety of non-ICU settings. Three-quarters of non-ICU studies had mortality rates at par with ICU studies which particularly examined patient cohorts who were considered stable for transfer out of the ICU but remained in the unit due to lack of alternative care settings [17, 48, 50, 58] . A study by Krieger et al. [44] had a considerably low mortality rate of 27.2% compared to most ICU studies despite requiring only a minimum ventilation duration of 3 days, which meant early transfer out of the ICU. A retrospective study by Seneff et al. [9] demonstrated no significant differences in 6-month mortality rates between ventilated patients transferred to a non-ICU setting and ventilated patients who remained in an acute hospital setting. Lastly, Gracey et al. [38] , which examined patient outcomes before and after the establishment of a non-ICU setting in a tertiary hospital, found improvement in survival with the availability of the venue. In addition to these outcomes, non-ICU settings provide patient-centered programs aimed at weaning and rehabilitation which are integral for patient recovery and improved clinical outcomes.

Given these findings, a non-ICU setting is thus a potential alternative setting for stable patients requiring prolonged ventilation during the COVID-19 pandemic and in the event of limited ICU resources. Newly established units or existing units such as non-ICU respiratory care units, long-term care facilities, and hospital wards can be used as care settings. In terms of staffing, nurse-to-patient ratios can range from 1:2 to 1:4, although there was one study that had a nurse-to-patient ratio of 1:6 [44] . To ensure safety, patient transfers from the ICU to a non-ICU setting should be limited to those with cardiorespiratory stability [11] .

With respect to home care, increased risk for viral transmission to family members or caregivers may limit its role in the current COVID-19 pandemic. However, considering its benefits such as improved quality of life, decreased rate of hospitalization and length of stay [13] , and reduced health care costs [39, 54, 73] , further discussion is warranted to consider home care as a possible alternative. In our systematic review, higher mortality rates were seen among home care patient populations. However, mortality rates of home care studies should be assessed with caution as there were considerable methodological and clinical heterogeneity including variable differences in observation periods and underlying etiology, respectively. For example, five studies [21, 25, 35, 54, 68] demonstrated higher mortality rates but also had extended periods of study observation. Muir et al. [54] also had the highest mortality rate as the entirety of the study cohort had a diagnosis of COPD, a disease known to cause poor mortality outcomes [66, 76] . Additionally, comparison of home care to other care settings could not be made due to differences not only in ventilation duration but also in patient and study factors. Despite these limitations, we found that home care has only been studied head-to-head with nursing homes and has been shown to have better survival outcomes [35, 64] . Although the reason is unclear, this suggests that ventilator care, albeit daunting and seemingly complex, can safely occur outside centralized health care institutions. Indeed, our systematic review underscores that ventilator failure is rarely the cause of death for patients on home mechanical ventilation [77] and there is no increased risk of hospitalizations as a result of home mechanical ventilation [13, 21, 39, 61, 63] .

Our study illustrates the safety of providing ventilatory care in settings outside the intensive care unit, more than two decades after the release of the consensus statement on "Mechanical Ventilation Beyond the Intensive Care Unit." [11] Moving forward, we recommend future prospective studies wherein two or more venues of care are directly compared within a study to minimize confounding and selection bias. Moreover, we implore researchers to identify additional or alternative measures of mortality and/or survival to sufficiently estimate the impact of a care setting on life expectancy. Lastly, as safety is not contingent on mortality or survival outcomes, clinical outcomes such as complication rates, hospitalization rates, and quality of life should also be compared across care settings.

With the COVID-19 pandemic pressing the limits of ICU bed and ventilator capacities, critically ill patients requiring prolonged mechanical ventilation can quickly overwhelm healthcare systems. Safe and high-quality care can be delivered to ventilator-dependent patients in non-ICU settings such as long-term acute care facilities or hospital wards as these settings demonstrated mortality rates comparable to that of intensive care units. Future investigations with direct comparisons of two or more care settings may add value to the findings of this systematic review and equip health systems with alternative settings to safely care for patients on prolonged mechanical ventilation in resource-limited settings.

All authors listed have significantly contributed to the development and the writing of this article.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Data included in article/supplementary material/referenced in article.

The authors declare no conflict of interest.

Supplementary content related to this article has been published online at https://doi.org/10.1016/j.heliyon.2021.e06230.

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