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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Med.</journal-id>
<journal-title>Frontiers in Medicine</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Med.</abbrev-journal-title>
<issn pub-type="epub">2296-858X</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/fmed.2023.1202754</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Medicine</subject>
<subj-group>
<subject>Review</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>The effects of early mobilization in mechanically ventilated adult ICU patients: systematic review and meta-analysis</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name><surname>Wang</surname> <given-names>Lijie</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/2275744/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Hua</surname> <given-names>Yusi</given-names></name>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Wang</surname> <given-names>Luping</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/1513377/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Zou</surname> <given-names>Xia</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Zhang</surname> <given-names>Yan</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Ou</surname> <given-names>Xiaofeng</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="corresp" rid="c001"><sup>&#x0002A;</sup></xref>
</contrib>
</contrib-group>
<aff id="aff1"><sup>1</sup><institution>Department of Critical Care Medicine, West China Hospital of Sichuan University</institution>, <addr-line>Chengdu, Sichuan</addr-line>, <country>China</country></aff>
<aff id="aff2"><sup>2</sup><institution>Department of Anesthesiology, West China Hospital of Sichuan University</institution>, <addr-line>Chengdu, Sichuan</addr-line>, <country>China</country></aff>
<author-notes>
<fn fn-type="edited-by"><p>Edited by: Christian Waydhas, Department Trauma Surgery, Germany</p></fn>
<fn fn-type="edited-by"><p>Reviewed by: Bj&#x000F6;rn Weiss, Charit&#x000E9; University Medicine Berlin, Germany; Aidos Konkayev, Astana Medical University, Kazakhstan; Shane Patman, University of Notre Dame Australia, Australia</p></fn>

<corresp id="c001">&#x0002A;Correspondence: Xiaofeng Ou <email>xiao.ou2006&#x00040;163.com</email></corresp>
</author-notes>
<pub-date pub-type="epub">
<day>28</day>
<month>06</month>
<year>2023</year>
</pub-date>
<pub-date pub-type="collection">
<year>2023</year>
</pub-date>
<volume>10</volume>
<elocation-id>1202754</elocation-id>
<history>
<date date-type="received">
<day>09</day>
<month>04</month>
<year>2023</year>
</date>
<date date-type="accepted">
<day>02</day>
<month>06</month>
<year>2023</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#x000A9; 2023 Wang, Hua, Wang, Zou, Zhang and Ou.</copyright-statement>
<copyright-year>2023</copyright-year>
<copyright-holder>Wang, Hua, Wang, Zou, Zhang and Ou</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/"><p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p></license> </permissions>
<abstract>
<sec>
<title>Background</title>
<p>The effects of early mobilization (EM) on intensive care unit (ICU) patients remain unclear. A meta-analysis of randomized controlled trials was performed to evaluate its effect in mechanically ventilated adult ICU patients.</p></sec>
<sec>
<title>Methods</title>
<p>We searched randomized controlled trials (RCTs) published in Medline, Embase, and CENTRAL databases (from inception to November 2022). According to the difference in timing and type, the intervention group was defined as a systematic EM group, and comparator groups were divided into the late mobilization group and the standard EM group. The primary outcome was mortality. The secondary outcomes were ICU length of stay, duration of mechanical ventilation (MV), and adverse events. EM had no impact on 180-day mortality and hospital mortality between intervention groups and comparator groups (RR 1.09, 95% CI 0.89&#x02013;1.33, <italic>p</italic> = 0.39). Systemic EM reduced the ICU length of stay (LOS) (MD &#x02212;2.18, 95% CI &#x02212;4.22&#x02013;&#x02212;0.13, <italic>p</italic> = 0.04) and the duration of MV (MD &#x02212;2.27, 95% CI &#x02212;3.99&#x02013;&#x02212;0.56, <italic>p</italic> = 0.009), but it may increase the incidence of adverse events in patients compared with the standard EM group (RR 1.99, 95% CI 1.25&#x02013;3.16, <italic>p</italic> = 0.004).</p></sec>
<sec>
<title>Conclusion</title>
<p>Systematic EM has no significant effect on short- or long-term mortality in mechanically ventilated adult ICU patients, but systematic EM could reduce the ICU LOS and duration of MV.</p></sec></abstract>
<kwd-group>
<kwd>early mobilization</kwd>
<kwd>mechanical ventilation</kwd>
<kwd>ICU</kwd>
<kwd>mortality</kwd>
<kwd>ICU length of stay</kwd>
</kwd-group>
<counts>
<fig-count count="5"/>
<table-count count="2"/>
<equation-count count="0"/>
<ref-count count="40"/>
<page-count count="11"/>
<word-count count="6063"/>
</counts>
<custom-meta-wrap>
<custom-meta>
<meta-name>section-at-acceptance</meta-name>
<meta-value>Intensive Care Medicine and Anesthesiology</meta-value>
</custom-meta>
</custom-meta-wrap>
</article-meta>
</front>
<body>
<sec sec-type="intro" id="s1">
<title>1. Introduction</title>
<p>Mechanically ventilated patients in ICUs are usually associated with short- or long-term complications, which are associated with increased mortality and mechanically ventilated duration, the longer length of ICU LOS and hospital LOS, reduced quality of life, and increased utilization of medical care (<xref ref-type="bibr" rid="B1">1</xref>). While the patients are being mechanically ventilated, EM has been proposed as a promising intervention to counteract these complications, and research suggests that it is a safe and feasible intervention (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B3">3</xref>).</p>
<p>There was evidence of the feasibility of EM to strengthen muscles (<xref ref-type="bibr" rid="B4">4</xref>&#x02013;<xref ref-type="bibr" rid="B6">6</xref>), improve Medical Research Council (MRC) and Barthel Index scores (<xref ref-type="bibr" rid="B7">7</xref>), and reduce the incidence of ICU-acquired weakness (<xref ref-type="bibr" rid="B8">8</xref>, <xref ref-type="bibr" rid="B9">9</xref>), delirium rate (<xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B10">10</xref>), and physical disability post&#x02013;intensive care (<xref ref-type="bibr" rid="B11">11</xref>). It also prevented the occurrences of vein thrombosis, ventilator-associated pneumonia, and pressure sores (<xref ref-type="bibr" rid="B7">7</xref>, <xref ref-type="bibr" rid="B12">12</xref>). Moreover, it shortens the duration of MV, length of ICU stay, and hospitalization (<xref ref-type="bibr" rid="B13">13</xref>, <xref ref-type="bibr" rid="B14">14</xref>).</p>
<p>However, numerous studies found EM with no or inconclusive evidence for a benefit. Many meta-analyses have concluded that EM of ICU patients has no effects on improvements in the functional status, muscle strength, quality of life (QOL) or health care utilization outcomes, ICU LOS, hospital LOS, ICU mortality and hospital mortality (<xref ref-type="bibr" rid="B15">15</xref>, <xref ref-type="bibr" rid="B16">16</xref>), and physical function- and mental health-related quality of life at 2&#x02013;3 months and 6 months post-hospital discharge (<xref ref-type="bibr" rid="B12">12</xref>, <xref ref-type="bibr" rid="B17">17</xref>). Most importantly, questions have recently arisen not only about the impact of EM on long-term outcomes but also about its safety. In an international, multicenter, randomized, controlled trial of 750 mechanically ventilated adult ICU patients, the TEAM study investigators and the ANZICS clinical trials group showed that an increase in EM did not improve survival, but it was associated with increased adverse events (<xref ref-type="bibr" rid="B18">18</xref>). On the other hand, because there is no unified concept of &#x0201C;early&#x0201D; in the EM literature, most studies believe that any mobilization activity is early if is commenced any time during the course of MV (<xref ref-type="bibr" rid="B19">19</xref>) or between 48 and 72 h after the start of MV (<xref ref-type="bibr" rid="B20">20</xref>, <xref ref-type="bibr" rid="B21">21</xref>).</p>
<p>Therefore, based on a lack of consensus with published findings about the effects of EM in patients requiring MV in ICU, a meta-analysis of RCTs was conducted to comprehensively assess the benefits and adverse effects of EM in critically ill patients and requiring MV.</p></sec>
<sec sec-type="methods" id="s2">
<title>2. Methods</title>
<sec>
<title>2.1. Protocol and registration</title>
<p>This study was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (<xref ref-type="bibr" rid="B22">22</xref>). The protocol has been registered on the international prospective register of systematic reviews website (PROSPERO: <ext-link ext-link-type="uri" xlink:href="https://www.crd.york.ac.uk/prospero/">https://www.crd.york.ac.uk/prospero/</ext-link>), and the registration number is CRD42022380303.</p>
</sec>
<sec>
<title>2.2. Eligibility criteria</title>
<p>Studies were included according to the following inclusion criteria: (1) Population: adult patients (&#x02265;18 years old) requiring MV at enrollment or during the ICU stay. (2) Design: RCT published in English. (3) Intervention: patients in the intervention group received systematic EM. Based on previously published meta-analyses (<xref ref-type="bibr" rid="B23">23</xref>), systematic EM was defined as any physical or occupational therapy targeting muscle activation, initiated within 3 days after ICU admission and performed according to a clearly defined protocol or specific clinical criteria in all eligible patients. (4) Comparators: patients in the control group received late mobilization (i.e., mobilization initiated 3 days or more after ICU admission) or standard EM (i.e., mobilization initiated within 3 days but less systematic) (<xref ref-type="bibr" rid="B23">23</xref>). (5) Outcomes: the primary outcome was mortality (including 180-day mortality and hospital mortality). The secondary outcomes were ICU LOS, duration of MV, and adverse events.</p>
<p>Studies that enrolled patients with pediatric, animal, or cell-based studies and studies published in narrative reviews, abstracts, commentaries, editorials case reports, and duplicate publications were excluded.</p>
</sec>
<sec>
<title>2.3. Information sources and search strategy</title>
<p>A computerized literature search was performed in Medline, Embase, and CENTRAL databases (from inception to November 2022) by two independent investigators using the keywords &#x0201C;intensive care unit,&#x0201D; &#x0201C;early mobilization,&#x0201D; &#x0201C;mechanical ventilation,&#x0201D; and &#x0201C;randomized controlled trial,&#x0201D; as well as their respective synonyms and derivations. The exact search strategy is provided in <xref ref-type="supplementary-material" rid="SM1">Supplementary File 1</xref>. The publication language was restricted to English.</p>
<p>After deduplication, two reviewers independently screened the titles and abstracts of all articles in order to detect the potential studies. Disagreements during the review process were resolved through discussion or consultation with an experienced senior reviewer. The pooled full-text references were then assessed to select eligible studies and when disagreement occurred, the dealing method is the same as mentioned above.</p>
</sec>
<sec>
<title>2.4. Data extraction</title>
<p>Two independent investigators adopted a standard collection form to extract related data from the included trials. The following information was extracted from each study: first author, year of publication, country, number of patients in intervention groups and comparator groups, patients&#x00027; baseline characteristics, patient admission diagnoses, intervention description, time to first intervention, intervention frequency, intervention duration, and adverse events. Discrepancies between the researchers were resolved through discussion or arbitration by a third researcher.</p>
</sec>
<sec>
<title>2.5. Risk of bias assessment</title>
<p>The risk of bias in included studies was assessed using the Cochrane risk of bias tool, and the overall risk of bias for an individual trial was classified as high risk (when the risk of bias was high in at least one domain), low risk (when the risk of bias was low in all domains), or unclear (when the risk of bias was unclear in at least one domain) (<xref ref-type="bibr" rid="B24">24</xref>).</p>
</sec>
<sec>
<title>2.6. Data synthesis</title>
<p>Considering these studies differ in the timing and type of interventions, results are reported stratified by a comparator category (systematic EM, late mobilization, and standard EM). According to these studies (<xref ref-type="bibr" rid="B23">23</xref>, <xref ref-type="bibr" rid="B25">25</xref>, <xref ref-type="bibr" rid="B26">26</xref>), eligible comparators were categorized as: systematic EM (i.e., mobilization initiated within 3 days of admission to the ICU with), late mobilization (i.e., mobilization initiated 3 days or more after ICU admission), standard EM (i.e., mobilization initiated within 3 days but less systematically, or without clear initiated timing for mobilization). It is worth mentioning that one of these studies included an intervention description of the control group that received mobilization therapy after leaving the ICU (the ICU LOS is 18.3 &#x000B1; 4.2 days), so this was defined as within the late mobilization category.</p>
<p>All statistical analyses were performed in this study using Review Manager 5.4 version (RevMan, The Cochrane Collaboration, Oxford, United Kingdom). For continuous variables (e.g., ICU LOS and duration of MV), mean differences (MDs) with 95% CIs were calculated using the inverse-variance (I-V) test, while for dichotomous variables (e.g., mortality and adverse events), risk ratios (RRs) with 95% confidence intervals (CIs) were calculated using the Mantel&#x02013;Haenszel (M-H) test. In this study, some trials presented the indicators as a median and interquartile range (IQR), which were transferred into mean and standard deviation (SD) (<xref ref-type="bibr" rid="B27">27</xref>, <xref ref-type="bibr" rid="B28">28</xref>). Comparable results were shown by fixed- or random effects and 95% confidence intervals.</p>
<p>Study heterogeneity was assessed by using the <italic>I</italic><sup>2</sup> statistics (<xref ref-type="bibr" rid="B29">29</xref>). If significant heterogeneity (<italic>I</italic><sup>2</sup> &#x0003C; 50%) was present, the fixed-effects model was used. Otherwise, the random-effects model was used. A two-sided <italic>P</italic>-value of &#x02264; 0.05 was considered to be statistically significant.</p></sec></sec>
<sec sec-type="results" id="s3">
<title>3. Results</title>
<sec>
<title>3.1. Search results</title>
<p><xref ref-type="fig" rid="F1">Figure 1</xref> shows the study selection process. The initial search identified 1,885 publications, of which 694 were excluded because of duplication. After reviewing the titles and abstracts, 1,147 were excluded because these articles&#x00027; research type, population, or language were unqualified. After browsing full-text, nine RCTs (<italic>n</italic> = 1,756 patients) were eligible for inclusion and analysis in this meta-analysis (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B13">13</xref>, <xref ref-type="bibr" rid="B18">18</xref>, <xref ref-type="bibr" rid="B30">30</xref>&#x02013;<xref ref-type="bibr" rid="B33">33</xref>).</p>
<fig id="F1" position="float">
<label>Figure 1</label>
<caption><p>PRISMA flow diagram of the study selection.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fmed-10-1202754-g0001.tif"/>
</fig>
</sec>
<sec>
<title>3.2. Study characteristics</title>
<p>The baseline characteristics of the included studies are presented in <xref ref-type="table" rid="T1">Table 1</xref>. Of the nine trials included, seven were published after 2015, while only two were published before that year, one in 2009 (<xref ref-type="bibr" rid="B2">2</xref>) and the other in 2014 (<xref ref-type="bibr" rid="B31">31</xref>). The included studies provided data from 883 people randomized to the intervention group and 873 people in the control group. In addition to the study conducted by Dong (<xref ref-type="bibr" rid="B30">30</xref>), the remaining eight trials reported the male-to-female ratio, which was about 42% in the intervention group and 43% in the comparator group. The mean age of the intervention group and the comparator group was similar, and the age difference in only two articles was large (<xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B30">30</xref>), which may be due to the small sample size of the two trials and random error in sampling. Eight studies reported primary study outcomes [180-day mortality (<xref ref-type="bibr" rid="B18">18</xref>, <xref ref-type="bibr" rid="B32">32</xref>, <xref ref-type="bibr" rid="B33">33</xref>) and hospital mortality (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B13">13</xref>, <xref ref-type="bibr" rid="B31">31</xref>)], and these studies reported secondary outcome measures: ICU LOS (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B13">13</xref>, <xref ref-type="bibr" rid="B30">30</xref>&#x02013;<xref ref-type="bibr" rid="B33">33</xref>), duration of MV (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B13">13</xref>, <xref ref-type="bibr" rid="B30">30</xref>&#x02013;<xref ref-type="bibr" rid="B32">32</xref>), and adverse events (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B18">18</xref>, <xref ref-type="bibr" rid="B30">30</xref>&#x02013;<xref ref-type="bibr" rid="B33">33</xref>).</p>
<table-wrap position="float" id="T1">
<label>Table 1</label>
<caption><p>Summary of included studies and study participants.</p></caption> 
<table frame="box" rules="all">
<thead>
<tr style="background-color:#8f9496">
<th valign="top" align="left"><bold>Study</bold></th>
<th valign="top" align="left"><bold>Country, timeframe</bold></th>
<th valign="top" align="left"><bold>Population</bold></th>
<th valign="top" align="left"><bold>Group</bold></th>
<th valign="top" align="left"><bold>No. of participants</bold></th>
<th valign="top" align="left"><bold>Females <italic>n</italic> (%)</bold></th>
<th valign="top" align="left"><bold>Age Mean (SD)/ Median (IQR)</bold></th>
<th valign="top" align="left"><bold>APACHEII score Mean (SD)/ Median (IQR)</bold></th>
<th valign="top" align="left"><bold>Patient admission diagnoses</bold></th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">Schweickert et al. (<xref ref-type="bibr" rid="B2">2</xref>)</td>
<td valign="top" align="left">USA, 2005&#x02013;2007</td>
<td valign="top" align="left">Adult ICU patients, mechanically ventilated &#x0003C; 72 h, independent at baseline</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">49</td>
<td valign="top" align="left">29 (59.2)</td>
<td valign="top" align="left">57.7 (36.3&#x02013;69.1)</td>
<td valign="top" align="left">20.0 (15.8&#x02013;24.0)</td>
<td valign="top" align="left">Lung injury (56%), COPD exacerbation (10%), acute exacerbation of asthma (9%), sepsis (15%), hemorrhage (3%), malignancy (3%), other (5%)</td>
</tr> <tr>
<td/>
<td/>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">55</td>
<td valign="top" align="left">23 (41.8)</td>
<td valign="top" align="left">54.4 (46.5&#x02013;66.4)</td>
<td valign="top" align="left">19.0 (13.3&#x02013;23.0)</td>
<td/>
</tr> <tr>
<td valign="top" align="left">Dong et al. (<xref ref-type="bibr" rid="B31">31</xref>)</td>
<td valign="top" align="left">China, 2010&#x02013;2012</td>
<td valign="top" align="left">Adult ICU patients, mechanically ventilated between 48 and 72 h with expected ventilation of &#x02265; 1 week, clear consciousness, cardiovascular and respiratory stability</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">30</td>
<td valign="top" align="left">9 (30.0)</td>
<td valign="top" align="left">55.3 (16.1)</td>
<td valign="top" align="left">15.0 (4.2)</td>
<td valign="top" align="left">Abdominal infections (18%), ARDS (32%), sepsis (7%), severe acute pancreatitis (15%), pneumonia (23%), COPD exacerbation (5%)</td>
</tr> <tr>
<td/>
<td/>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">30</td>
<td valign="top" align="left">10 (33.3)</td>
<td valign="top" align="left">55.5 (16.2)</td>
<td valign="top" align="left">16.0 (4.1)</td>
<td/>
</tr> <tr>
<td valign="top" align="left">Hodgson et al. (<xref ref-type="bibr" rid="B4">4</xref>)</td>
<td valign="top" align="left">Australia/New Zealand, 2013&#x02013;2014</td>
<td valign="top" align="left">Adult ICU patients, mechanically ventilated within 72 h of ICU admission</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">29</td>
<td valign="top" align="left">8 (25.9)</td>
<td valign="top" align="left">64 (12)</td>
<td valign="top" align="left">19.8 (9.8)</td>
<td valign="top" align="left">N/A</td>
</tr> <tr>
<td/>
<td/>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">21</td>
<td valign="top" align="left">12 (57.1)</td>
<td valign="top" align="left">53 (15)</td>
<td valign="top" align="left">15.9 (6.9)</td>
<td/>
</tr> <tr>
<td valign="top" align="left">Morris et al. (<xref ref-type="bibr" rid="B33">33</xref>)</td>
<td valign="top" align="left">USA, 2009&#x02013;2014</td>
<td valign="top" align="left">Adult ICU patients, acute respiratory failure requiring mechanical ventilation</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">150</td>
<td valign="top" align="left">84 (56.0)</td>
<td valign="top" align="left">55 (17)</td>
<td valign="top" align="left">NA</td>
<td valign="top" align="left">Acute respiratory failure (98%), coma (2%)</td>
</tr> <tr>
<td/>
<td/>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">150</td>
<td valign="top" align="left">82 (54.7)</td>
<td valign="top" align="left">58 (14)</td>
<td valign="top" align="left">NA</td>
<td/>
</tr> <tr>
<td valign="top" align="left">Schaller et al. (<xref ref-type="bibr" rid="B10">10</xref>)</td>
<td valign="top" align="left">USA/Germany, 2011&#x02013;2015</td>
<td valign="top" align="left">Adult surgical ICU patients, mechanically ventilated for &#x0003C; 48 h and for at least further 24 h, functionally independent at baseline</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">104</td>
<td valign="top" align="left">39 (37.5)</td>
<td valign="top" align="left">66 (48&#x02013;73)</td>
<td valign="top" align="left">16 (12&#x02013;22)</td>
<td valign="top" align="left">Visceral surgery (27%), vascular surgery (17%), ENT and ophthalmological surgery (10%), transplant surgery (4%), neurosurgery (3%), orthopedic surgery (3%), thoracic surgery (3%), gynecological surgery (2%), urological surgery (1%), plastic surgery (1%), medical or neurological diagnosis (6%), trauma (26%)</td>
</tr> <tr>
<td/>
<td/>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">96</td>
<td valign="top" align="left">35 (36.5)</td>
<td valign="top" align="left">64 (45&#x02013;76)</td>
<td valign="top" align="left">17 (11&#x02013;22)</td>
<td/>
</tr> <tr>
<td valign="top" align="left">Dong et al. (<xref ref-type="bibr" rid="B13">13</xref>)</td>
<td valign="top" align="left">China, 2012&#x02013;2015</td>
<td valign="top" align="left">Adult patients, prolonged mechanical ventilation &#x0003E; 72 h, eligible for coronary artery bypass surgery</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">53</td>
<td valign="top" align="left">33 (62.3)</td>
<td valign="top" align="left">62.6 (12.8)</td>
<td valign="top" align="left">16.3 (4.2)</td>
<td valign="top" align="left">Coronary artery bypass surgery (100%)</td>
</tr> <tr>
<td/>
<td/>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">53</td>
<td valign="top" align="left">31 (58.5)</td>
<td valign="top" align="left">60.2 (15.1)</td>
<td valign="top" align="left">17.2 (4.3)</td>
<td/>
</tr> <tr>
<td valign="top" align="left">Eggmann et al. (<xref ref-type="bibr" rid="B32">32</xref>)</td>
<td valign="top" align="left">Switzerland, 2012&#x02013;2016</td>
<td valign="top" align="left">Adult ICU patients, expected to stay on mechanical ventilation for at least 72 h, independent before critical illness</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">58</td>
<td valign="top" align="left">22 (37.9)</td>
<td valign="top" align="left">65 (15)</td>
<td valign="top" align="left">23.0 (7.0)</td>
<td valign="top" align="left">Cardiac surgery (18%), neurology/neurosurgery (8%), other surgery (12%), gastroenterology (12%), trauma (4%), respiratory insufficiency (22%), hemodynamic insufficiency (23%), other (2%)</td>
</tr> <tr>
<td valign="top" align="left">Dong et al. (<xref ref-type="bibr" rid="B30">30</xref>)</td>
<td valign="top" align="left">China, 2019&#x02013;2020</td>
<td valign="top" align="left">Adult ICU patients, Prolonged MV (&#x0003E; 72 h), clear consciousness, cardiovascular and respiratory stability, no history of chronic mental illness or COPD</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">39</td>
<td valign="top" align="left">NA</td>
<td valign="top" align="left">59.05 &#x000B1; 17.61</td>
<td valign="top" align="left">15.90 &#x000B1; 6.01</td>
<td valign="top" align="left">N/A</td>
</tr> <tr>
<td/>
<td/>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">41</td>
<td valign="top" align="left">NA</td>
<td valign="top" align="left">64.44 &#x000B1; 14.72</td>
<td valign="top" align="left">17.78 &#x000B1; 8.40</td>
<td/>
</tr> <tr>
<td valign="top" align="left">Hodgson et al. (<xref ref-type="bibr" rid="B18">18</xref>)</td>
<td valign="top" align="left">Australia/ New Zealand/ Germany/ Ireland/UK/ Brazil, 2018&#x02013;2021</td>
<td valign="top" align="left">Adult ICU patients (&#x02265; 18 years of age), mechanical ventilation, condition was sufficiently stable to make mobilization potentially possible</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">371</td>
<td valign="top" align="left">128 (34.5)</td>
<td valign="top" align="left">60.5 &#x000B1; 14.8</td>
<td valign="top" align="left">18.2 &#x000B1; 6.8</td>
<td valign="top" align="left">Sepsis (66.3%), Trauma (3.9%), COVID-19 (2.3%), others (27.5%)</td>
</tr>
<tr>
<td/>
<td/>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">370</td>
<td valign="top" align="left">146 (39.5)</td>
<td valign="top" align="left">59.5 &#x000B1; 15.2</td>
<td valign="top" align="left">18 &#x000B1; 6.9</td>
<td/>
</tr>
</tbody>
</table>
</table-wrap>
<p>Considering the difference between studies in the timing and type of interventions, some results are reported stratified by a comparator category (systematic EM, late mobilization, and standard EM). According to the study definition, five studies were classified (<xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B18">18</xref>, <xref ref-type="bibr" rid="B30">30</xref>&#x02013;<xref ref-type="bibr" rid="B32">32</xref>) as comparing systematic EM vs. standard EM, and the other four studies (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B13">13</xref>, <xref ref-type="bibr" rid="B33">33</xref>) were classified as systematic EM vs. late mobilization (in <xref ref-type="table" rid="T2">Table 2</xref>). Different studies intervene in different ways, including head up, transferring from supination to sitting, standing, and walking, and other goal-oriented mobilization protocols. The frequency of intervention was once daily, twice daily, or three times daily. The duration of the intervention ranged from 20 to 60 min in the intervention group and from 0 to 0.2 h in the control group (in <xref ref-type="table" rid="T2">Table 2</xref>).</p>
<table-wrap position="float" id="T2">
<label>Table 2</label>
<caption><p>Details on study interventions and comparators.</p></caption> 
<table frame="box" rules="all">
<thead>
<tr style="background-color:#8f9496">
<th valign="top" align="left"><bold>Study</bold></th>
<th valign="top" align="left"><bold>Group</bold></th>
<th valign="top" align="left"><bold>Intervention description</bold></th>
<th valign="top" align="left"><bold>Time to first intervention Median (IQR) (days)</bold></th>
<th valign="top" align="left"><bold>Intervention frequency</bold></th>
<th valign="top" align="left"><bold>Intervention duration Mean (SD)/ Median (IQR)</bold></th>
</tr>
</thead>
<tbody>
<tr style="background-color:#dee1e1">
<td valign="top" align="left" colspan="6"><bold>Systematic early mobilization vs. Standard early mobilization</bold></td>
</tr> <tr>
<td valign="top" align="left">Dong et al. (<xref ref-type="bibr" rid="B31">31</xref>)</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">Heading up actively, transferring from the supine position to sitting position, sitting at the edge of the bed, sitting in chair, transferring from sitting to standing, ambulating bedside and changed every 2 h</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">Twice daily</td>
<td valign="top" align="left">According to the condition of patients</td>
</tr> <tr>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">Not described</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">N/A</td>
</tr> <tr>
<td valign="top" align="left">Schaller et al. (<xref ref-type="bibr" rid="B10">10</xref>)</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">Early, goal-directed mobilization algorithm: the goal for a specific day was set either to level 0 (no mobilization), level 1 (passive range of motion exercises in the bed), level 2 (sitting), level 3 (standing), or level 4 ambulation)</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">Once daily</td>
<td valign="top" align="left">Depending on the condition of patients</td>
</tr> <tr>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">Standard care except for early, goal directed mobilization</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">Once daily</td>
<td valign="top" align="left">N/A</td>
</tr> <tr>
<td valign="top" align="left">Eggmann et al. (<xref ref-type="bibr" rid="B32">32</xref>)</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">Motor-assisted bed-cycle, standard exercises for both upper and lower limbs exercises for both upper and lower limbs, in-bed exercise, sitting, standing and walking</td>
<td valign="top" align="left">2.0 (1.4&#x02013;2.8) after ICU admission</td>
<td valign="top" align="left">maximum 3 times daily, 7 days per week</td>
<td valign="top" align="left">25 min (19.5&#x02013;27)</td>
</tr> <tr>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">European standard Physiotherapy including early mobilization, respiratory therapy and passive or active exercises</td>
<td valign="top" align="left">2.0 (1.4&#x02013;2.8) after ICU admission</td>
<td valign="top" align="left">Once daily</td>
<td valign="top" align="left">18 min (14&#x02013;21)</td>
</tr> <tr>
<td valign="top" align="left">Dong et al. (<xref ref-type="bibr" rid="B30">30</xref>)</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">Rehabilitation therapy consisted of six levels: level 0, turning over; level 1&#x02013;2, sit up; level 3, sitting on the edge of bed; level 4, standing up or sitting in a chair; level 5, moved from the bed and walked</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">Tailored depending on the condition of patients</td>
</tr> <tr>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">Standard care</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">N/A</td>
</tr> <tr>
<td valign="top" align="left">Hodgson et al. (<xref ref-type="bibr" rid="B18">18</xref>)</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">Senior physiotherapists led the intervention and participated in interdisciplinary discussions and reviews of a safety checklist</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">Once daily</td>
<td valign="top" align="left">20.8 &#x000B1; 14.6 min</td>
</tr> <tr>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">The level of mobilization that was normally provided in each ICU</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">Once daily</td>
<td valign="top" align="left">8.8 &#x000B1; 9.0 min</td>
</tr> <tr style="background-color:#dee1e1">
<td valign="top" align="left" colspan="6"><bold>Systematic early mobilization vs. Late mobilization</bold></td>
</tr> <tr>
<td valign="top" align="left">Schweickert et al. (<xref ref-type="bibr" rid="B2">2</xref>)</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">Passive range of motion, active-assisted and active-independent exercises, bed mobility exercises, Sitting balance activities, transfer training, pre-gait exercises and walking</td>
<td valign="top" align="left">1.5 (1.0&#x02013;2.1) after intubation</td>
<td valign="top" align="left">Once daily</td>
<td valign="top" align="left">0.3 h (0.2&#x02013;0.5) per day during ventilation 0.2 h (0.1&#x02013;0.3) per day without ventilation</td>
</tr> <tr>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">standard care with physical and occupational therapy delivered as ordered by the primary care team</td>
<td valign="top" align="left">7.4 (6.0&#x02013;10.9) after intubation</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">0.0 h (0.0&#x02013;0.0) per day during ventilation 0.2 h (0.0&#x02013;0.4) per day without ventilation</td>
</tr> <tr>
<td valign="top" align="left">Morris et al. (<xref ref-type="bibr" rid="B33">33</xref>)</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">Passive range of motion, physical therapy and progressive resistance exercise</td>
<td valign="top" align="left">1 (0&#x02013;2) after ICU admission</td>
<td valign="top" align="left">3 times daily, 7 days a week</td>
<td valign="top" align="left">N/A</td>
</tr> <tr>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">Weekday physical therapy when ordered by the clinical team</td>
<td valign="top" align="left">7 (4&#x02013;10) after ICU admission</td>
<td valign="top" align="left">5 days a week</td>
<td valign="top" align="left">N/A</td>
</tr> <tr>
<td valign="top" align="left">Dong et al. (<xref ref-type="bibr" rid="B13">13</xref>)</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">head up, transferring from supination to sitting, sitting on the edge of bed, sitting in a chair, transferring from sitting to standing, and walking along a bed</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">Twice daily</td>
<td valign="top" align="left">N/A</td>
</tr> <tr>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">Received rehabilitation therapy with the help of family after leaving the ICU</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">N/A</td>
<td valign="top" align="left">N/A</td>
</tr> <tr>
<td valign="top" align="left">Hodgson et al. (<xref ref-type="bibr" rid="B4">4</xref>)</td>
<td valign="top" align="left">Intervention</td>
<td valign="top" align="left">Functional activities comprising walking, standing, balance exercises, sitting in or out of bed, sitting and rolling (the patient could receive assistance from staff or equipment but the patient actively participated in the exercise at the highest functional level)</td>
<td valign="top" align="left">3 (2&#x02013;4) after ICU admission</td>
<td valign="top" align="left">Once daily</td>
<td valign="top" align="left">About 30&#x02013;60 min depending on the condition of patients</td>
</tr>
<tr>
<td/>
<td valign="top" align="left">Comparator</td>
<td valign="top" align="left">Passive movements (the same mobilization equipment was available in both the control group and the intervention group)</td>
<td valign="top" align="left">4 (3&#x02013;5) after ICU admission</td>
<td valign="top" align="left">Once daily</td>
<td valign="top" align="left">About 5&#x02013;10 min per day</td>
</tr>
</tbody>
</table>
</table-wrap>
</sec>
<sec>
<title>3.3. Risk of bias assessment</title>
<p>The details of the risk of bias assessment are summarized in <xref ref-type="fig" rid="F2">Figure 2</xref>. Seven studies (78%) were at low risk of bias of the random sequence generation. A suitable method of allocation concealment was used in five studies (56%). Because the patients in the intervention group needs to rehabilitate, blinding of participants and personnel was not possible, and eight studies (89%) were at high risk of bias. Six studies (67%) reported blinding of the outcome assessment. Incomplete outcome data may exist in two studies (22%), and three studies (33%) could be reporting selective.</p>
<fig id="F2" position="float">
<label>Figure 2</label>
<caption><p>Risk of bias assessment for the included studies.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fmed-10-1202754-g0002.tif"/>
</fig>
</sec>
<sec>
<title>3.4. Mortality</title>
<p>As shown in <xref ref-type="fig" rid="F3">Figure 3</xref>, eight studies reported mortality at different time points. Among them, three studies (<xref ref-type="bibr" rid="B18">18</xref>, <xref ref-type="bibr" rid="B32">32</xref>, <xref ref-type="bibr" rid="B33">33</xref>) reported 180-day mortality that included 577 patients in the intervention group (the systematic EM group) and 571 patients in the comparator group (the late mobilization group and the standard EM group), and there was no significant difference in 180-day mortality between the two groups (RR 1.09, 95% CI 0.88&#x02013;1.35, <italic>I</italic><sup>2</sup> = 0%, test for overall effect: Z = 0.76, <italic>p</italic> = 0.45). As for hospital mortality, there were five studies included in this analysis with 520 patients (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B13">13</xref>, <xref ref-type="bibr" rid="B31">31</xref>), and no significant difference was found in mortality between the two groups (RR 1.10, 95% CI 0.69&#x02013;1.76, <italic>I</italic><sup>2</sup> = 0%, test for overall effect: Z = 0.39, <italic>p</italic> = 0.69). The results of subgroup analysis showed no difference in mortality between the systematic EM group and standard EM or the late mobilization group at any time points (RR 1.09, 95% CI 0.89&#x02013;1.33, <italic>I</italic><sup>2</sup> = 0%, test for overall effect: <italic>Z</italic> = 0.86, <italic>p</italic> = 0.39).</p>
<fig id="F3" position="float">
<label>Figure 3</label>
<caption><p>Forest plot for early mobilization on effect mortality in the included studies. Intervention group = systematic early mobilization group, Comparator = late mobilization or standard early mobilization.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fmed-10-1202754-g0003.tif"/>
</fig>
</sec>
<sec>
<title>3.5. ICU length of stay</title>
<p>Eight studies reported the relationship between EM and ICU LOS. In the subgroup analysis, there are four studies that adopted systematic EM and late mobilization (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B13">13</xref>, <xref ref-type="bibr" rid="B33">33</xref>), and no significant difference was found between these two groups (MD &#x02212;2.38, 95% CI &#x02212;6.37&#x02013;1.62, <italic>I</italic><sup>2</sup> = 93%, test for overall effect: Z = 1.17, <italic>p</italic> = 0.24). In addition, the other four studies (<xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B30">30</xref>&#x02013;<xref ref-type="bibr" rid="B32">32</xref>) had an impact on systemic EM and standard EM for LOS in ICU. Compared with the standard EM group, there was a statistically significant reduction of ICU LOS in the systematic EM group (MD &#x02212;2.10, 95% CI &#x02212;3.27&#x02013;&#x02212;0.94, <italic>I</italic><sup>2</sup> = 0%, test for overall effect: Z = 3.54, <italic>p</italic> &#x0003C; 0.001). A pooled analysis of these studies showed a significant mean difference and favored the systematic EM group (MD &#x02212;2.18, 95% CI &#x02212;4.22&#x02013;&#x02212;0.13, <italic>I</italic><sup>2</sup> = 85%, test for overall effect: Z = 2.08, <italic>p</italic> = 0.04, n = 1,015) (<xref ref-type="fig" rid="F4">Figure 4</xref>).</p>
<fig id="F4" position="float">
<label>Figure 4</label>
<caption><p>Forest plot for early mobilization effect on ICU length of stay in the included studies.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fmed-10-1202754-g0004.tif"/>
</fig>
</sec>
<sec>
<title>3.6. Duration of mechanical ventilation</title>
<p>Six studies analyzed 515 patients who reported the duration of MV. The pooled analysis of the data indicated a decreased trend in the duration of MV following systematic EM (MD &#x02212;2.27, 95% CI &#x02212;3.99&#x02013;&#x02212;0.56, <italic>I</italic><sup>2</sup> = 82%, test for overall effect: Z = 2.60, <italic>p</italic> = 0.009) (<xref ref-type="fig" rid="F4">Figure 4</xref>). In the subgroup analysis, there was a statistically significant mechanically ventilated duration in the systematic EM group, compared with the late mobilization group (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B13">13</xref>) and the standard EM group (<xref ref-type="bibr" rid="B30">30</xref>&#x02013;<xref ref-type="bibr" rid="B32">32</xref>) (MD &#x02212;3.38, 95% CI &#x02212;6.17&#x02013;&#x02212;0.59, <italic>I</italic><sup>2</sup> = 85%, test for overall effect: Z = 2.37, <italic>p</italic> = 0.02 and MD &#x02212;1.39, 95% CI &#x02212;2.50&#x02013;&#x02212;0.28, <italic>I</italic><sup>2</sup> = 20%, test for overall effect: Z = 2.44, <italic>p</italic> = 0.01, respectively) (<xref ref-type="fig" rid="F4">Figure 4</xref>).</p>
</sec>
<sec>
<title>3.7. Adverse events</title>
<p>A total of eight trials with 1,650 patients reported different adverse events among participants. These trials reported adverse events including decreased desaturation, agitation, dislodgement of arterial line or nasogastric tube, dyspnea, dizziness, cardiac arrhythmia, altered blood pressure, and cerebrovascular accident (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B18">18</xref>, <xref ref-type="bibr" rid="B30">30</xref>&#x02013;<xref ref-type="bibr" rid="B33">33</xref>). The adverse events were not significantly different between the systemic EM group and the late mobilization group (RR 1.35, 95% CI 0.05&#x02013;33.52, <italic>I</italic><sup>2</sup> = 86%, test for overall effect: Z = 0.18, <italic>p</italic> = 0.85) (<xref ref-type="bibr" rid="B2">2</xref>, <xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B33">33</xref>). However, there were more adverse events in the systemic EM group compared to the standard EM group (RR 1.99, 95% CI 1.25&#x02013;3.16, <italic>I</italic><sup>2</sup> = 0%, test for overall effect: Z = 2.89, <italic>p</italic> = 0.004) (<xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B18">18</xref>, <xref ref-type="bibr" rid="B30">30</xref>&#x02013;<xref ref-type="bibr" rid="B32">32</xref>) (<xref ref-type="fig" rid="F5">Figure 5</xref>).</p>
<fig id="F5" position="float">
<label>Figure 5</label>
<caption><p>Forest plot for early mobilization effect on adverse events in the included studies.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fmed-10-1202754-g0005.tif"/>
</fig></sec></sec>
<sec sec-type="discussion" id="s4">
<title>4. Discussion</title>
<p>This meta-analysis included 9 RCTs, and it was found that systematic EM had no effect on short- or long-term mortality in mechanically ventilated adult ICU patients, but it could reduce the LOS in ICU and the duration of MV. While systemic EM may increase the incidence of adverse events in patients compared with standard EM.</p>
<p>The meta-analysis found that EM in the ICU had no effects on 180 days mortality and hospital mortality. There have been many studies on the impact of EM on mortality in ICU patients. After comparing the effects of EM and late mobilization, standard EM or no mobilization, Dominik (<xref ref-type="bibr" rid="B23">23</xref>) argued that none of them had any effect on patients&#x00027; short-term mortality (hospital mortality) and long-term mortality (6-month mortality), which the current study findings support. A systematic review (<xref ref-type="bibr" rid="B34">34</xref>) about the impact of mobilization on the mortality of ICU patients demonstrated that mobilization had no positive effects on short- or long-term mortality. The results were consistent with the present study findings, but the current meta-analysis was the inclusion of a multicenter, high-quality, large-population RCTS study published in the New England Journal in October 2022 (<xref ref-type="bibr" rid="B18">18</xref>), which added strong evidence to the results.</p>
<p>This study showed that both ICU LOS and the duration of the mechanical ventilator were approximately reduced by 2 days in the EM group. The included four studies (<xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B30">30</xref>&#x02013;<xref ref-type="bibr" rid="B32">32</xref>) comparing the length of ICU stay between systematic EM and standard EM showed little heterogeneity and a significant difference between the two groups, suggesting systematic EM within 3 days of ICU admission can effectively reduce the length of ICU stay. Similar results have been found in other systematic reviews. Klem et al. (<xref ref-type="bibr" rid="B35">35</xref>) suggested that EM can shorten ICU stay by 1 day but has no effect on the total hospital LOS and also about the effects of systematic EM on the duration of the mechanical ventilator. Zhang et al. (<xref ref-type="bibr" rid="B36">36</xref>) reported the same positive results in a systematic review. Monsees et al. (<xref ref-type="bibr" rid="B37">37</xref>) also implied the same trend toward a reduction in the duration of mechanical ventilators with EM. It is thought that EM can reduce ICU-acquired weakness (<xref ref-type="bibr" rid="B38">38</xref>), which may associate with a prolonged duration of mechanical ventilator (<xref ref-type="bibr" rid="B39">39</xref>, <xref ref-type="bibr" rid="B40">40</xref>).</p>
<p>In terms of safety and adverse events, there were eight trials that reported adverse events. Hodgson (<xref ref-type="bibr" rid="B18">18</xref>) reported 34 patients with adverse events in the EM group and 15 patients with adverse events in the usual care group, suggesting that the incidence of adverse events in the EM group was higher than that in the usual care group (<italic>P</italic> = 0.005). While in the other studies, there was no difference in the incidence of adverse events between the intervention group and the comparator group. Although serious adverse events were very rare, they still occurred. For example, Schweickert (<xref ref-type="bibr" rid="B38">38</xref>) reported a case of desaturation of &#x0003C; 80%. Therefore, it is believed that the initiation of EM should be very cautious.</p>
<p>There are some limitations in this study. First, some of the included studies had small sample sizes. In three studies (<xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B30">30</xref>, <xref ref-type="bibr" rid="B31">31</xref>), there were &#x0003C; 100 total participants, which is more likely to overestimate the effects. Second, our conclusions may be limited by the poor quality and bias of some of the studies. The performance bias and detection bias in these two articles are high-risk, and selection bias and reporting bias are unclear (<xref ref-type="bibr" rid="B13">13</xref>, <xref ref-type="bibr" rid="B30">30</xref>). Third, the definition of EM is not clear in those included studies. Some studies suggest that it should be limited to 3 days (<xref ref-type="bibr" rid="B25">25</xref>, <xref ref-type="bibr" rid="B26">26</xref>), while others suggest that it should be limited to 7 days (<xref ref-type="bibr" rid="B23">23</xref>). Different definitions may lead to different subgroups, which may affect results. In addition, some other factors cannot be ignored, such as the mode and duration of mobilization treatment, which vary greatly between studies. The lack of detailed information may affect the accuracy of this study.</p></sec>
<sec sec-type="conclusions" id="s5">
<title>5. Conclusion</title>
<p>Although EM does not improve short- or long-term mortality in mechanically ventilated adult ICU patients, this systematic review found that systematic EM could reduce the ICU LOS and duration of MV, but it may increase the incidence of adverse events compared with standard EM, which suggest that EM should be initiated carefully. However, given the potential limitations of this study and the substantial heterogeneity among the included trials, the results of this study should be interpreted with caution. Further large-scale and well-conducted RCTs are needed to validate our current findings.</p></sec>
<sec sec-type="author-contributions" id="s6">
<title>Author contributions</title>
<p>XO: conceptualization and supervision. LiW: methodology and writing&#x02014;review and editing. LiW and YH: formal analysis. LiW, YH, XZ, YZ, and LuW: data curation. LiW and LuW: writing&#x02014;original draft preparation. All authors have read and agreed to the published version of the manuscript.</p></sec>
</body>
<back>


<sec sec-type="COI-statement" id="conf1">
<title>Conflict of interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec sec-type="disclaimer" id="s7">
<title>Publisher&#x00027;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
<sec sec-type="supplementary-material" id="s8">
<title>Supplementary material</title>
<p>The Supplementary Material for this article can be found online at: <ext-link ext-link-type="uri" xlink:href="https://www.frontiersin.org/articles/10.3389/fmed.2023.1202754/full#supplementary-material">https://www.frontiersin.org/articles/10.3389/fmed.2023.1202754/full#supplementary-material</ext-link></p>
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