Study selection
After removal of duplicates, 8706 studies were identified. Following title and abstract review 51 full texts remained, of which 10 met the inclusion criteria (Fig. 1). Four studies appeared to meet the inclusion criteria but were excluded at full-text review: two studies were excluded for not reporting a subset of their analysis for the patients using the AMS [32, 33]; one was excluded after confirming with the author that the device was not ambulatory at the time of the study [34], and another did not have a comparator group [35]. A total of 4433 patients were included in these studies.
Study Characteristics
Devices
A variety of devices were used in the studies included in this review: four studies used the VisiMobile (Sotera Visi Mobile, San Diego, California) [26, 36–38], with two studies also adding the HealthPatch (Vital Connect, Campbell, CA, USA) [37, 38]; two studies used Sensium Vitals (Sensium, Abingdon, United Kingdom) [29, 30]. The remaining four studies used different devices, including the Patient Status Engine (Isansys Lifecare Ltd.) [27], the Auricall monitoring system [39], the Avant-4100 (Nonin) [40] and the Monica Novii wireless patch system (General Electric Company, Milwaukee, WI) [41].
Included studies and outcomes
Table 1
Characteristics of the included studies. AMS: ambulatory monitoring system, BP: blood pressure, CEWS: centile-based early warning score, ESS: efficacy safety score, EWS: early warning score, HR: heart rate, NEWS: national early warning score, PSE: Patient Status Engine, RR: respiratory rate, SpO2: peripheral oxygen saturation, T: temperature. *Same patients. Weenk et al. 2020 added 30 controls. ** Both maternal and fetal heart rate
Source
|
Country
|
Population
|
Sample size
|
Interventions
|
Vital signs measured by AMS
|
Age (years)
|
Sex (% male)
|
Total
|
Control (EWS)
|
AMS
|
HR
|
RR
|
SpO2
|
BP
|
T
|
Control
|
AMS
|
Control
|
AMS
|
Meta-analysis
|
Skraastad et al. 2019
|
Norway
|
General surgery
|
195
|
Intermittent vital signs (NEWS)
|
PSE (NEWS) + ESS
|
x
|
x
|
x
|
x
|
x
|
62
|
61
|
63%
|
63%
|
Downey et al. 2020
|
UK
|
General surgery
|
135
|
Intermittent vital signs (NEWS)
|
SensiumVitals + NEWS
|
x
|
x
|
|
|
x
|
62
|
65
|
54%
|
52%
|
Downey et al. 2018
|
UK
|
General surgery
|
226
|
Intermittent vital signs (NEWS)
|
SensiumVitals + NEWS
|
x
|
x
|
|
|
x
|
63.7
|
65.2
|
45%
|
54%
|
Kisner et al. 2009
|
Switzerland
|
General surgery
|
357
|
Intermittent vital signs (Unknown)
|
Auricall
|
x
|
|
x
|
|
|
62.7
|
65
|
75%
|
75%
|
Weller et al. 2018
|
USA
|
Neurology and neurosurgery
|
1958
|
Intermittent vital signs (Unknown)
|
VisiMobile
|
x
|
x
|
x
|
x
|
x
|
59.3
|
60.5
|
58%
|
54%
|
Verrillo et al. 2018
|
USA
|
Orthopaedic, spinal and trauma general care
|
849
|
Intermittent vital signs (Unknown)
|
VisiMobile
|
x
|
x
|
x
|
x
|
x
|
51.4
|
54.5
|
58%
|
54%
|
Watkinson et al. 2020
|
UK
|
Gastro intestinal surgery
|
407
|
Intermittent vital signs (CEWS)
|
Avant-4100
|
x
|
|
x
|
|
|
63
|
63
|
56%
|
58%
|
Narrative
|
Weenk et al. 2019
|
Netherlands
|
Surgical and internal medicine ward
|
60*
|
Intermittent measurement (MEWS)
|
VisiMobile
|
x
|
x
|
x
|
x
|
x
|
N/A
|
63
|
N/A
|
60%
|
HealthPatch
|
x
|
x
|
|
|
x
|
N/A
|
56
|
N/A
|
73.3%
|
Weenk et al. 2020
|
Netherlands
|
Surgical and internal medicine ward
|
90*
|
Intermittent measurement (MEWS)
|
VisiMobile
|
x
|
x
|
x
|
x
|
x
|
62
|
63
|
67%
|
60%
|
HealthPatch
|
x
|
x
|
|
|
x
|
|
56
|
|
73.3%
|
Monson et al. 2020
|
USA
|
Labour and delivery ward
|
216
|
Standard external monitoring
|
Monica
Novii
|
x**
|
|
|
|
|
28.6
|
29.2
|
0%
|
0%
|
Of the ten studies identified, seven were included in the meta-analysis with a total of 4127 patients. These included two RCTs [27, 30], one cluster RCT [29], and four before-and-after observational studies [26, 36, 39, 40]. Three further studies (RCTs) were included in the narrative synthesis [37, 38, 41], including a total of 306 further patients. Details of the included studies are presented in Tables 1 and 2.
The majority of the included studies implemented the AMS in post-surgical patients. Four studies also reported the patient American Society of Anaesthesiologists (ASA) score for preoperative functional status [42], with a median ASA score of 2 (“Patient has mild systemic disease”) in three studies [29, 30, 43] and 3 (“Patient has severe systemic disease that is not incapacitating.”) in one [27].
Reviewers achieved a fair level of agreement (kappa: 0.348; 95% CI 0.285 to 0.482) for study inclusion. There were no major disagreements between reviewers regarding data extraction, study quality or bias assessments.
Table 2
Included studies primary outcomes and outcomes included in the meta-analysis.
Source
|
Design
|
Primary outcome
|
Deterioration detection outcomes
|
Clinical Outcomes
|
ICU transfer
|
RRT activation or cardiac arrest team call
|
All complications
|
Major complications
|
Mortality
|
Length of stay
|
Meta-analysis
|
Skraastad et al. 2019
|
RCT
|
Time to mobilisation
|
|
|
X
|
X
|
X
|
X
|
Downey et al. 2020
|
Pilot RCT
|
Progression criteria to full RCT
|
X
|
|
X
|
X
|
X
|
X
|
Downey et al. 2018
|
Cluster RCT
|
Time to antibiotics in patients with sepsis
|
X
|
|
X
|
X
|
X
|
X
|
Kisner et al. 2009
|
Before-after
|
Incidence of postoperative atrial fibrillation
|
|
|
X
|
|
|
|
Weller et al. 2018
|
Before-after
|
Rate of patient deterioration events
|
X
|
X
|
|
|
X
|
X
|
Verrillo et al. 2018
|
Before-after
|
Early deterioration detection
|
X
|
X
|
X
|
|
X
|
|
Watkinson et al. 2020
|
Before-after
|
Length of stay
|
X
|
X
|
|
|
X
|
X
|
Narrative
|
Weenk et al. 2019
|
RCT
|
Experiences of patients and care givers
|
|
|
|
|
|
|
Weenk et al. 2020
|
|
|
|
|
|
|
Monson et al. 2020
|
RCT
|
Amount of time with the interpretable fetal HR tracing during of labour
|
|
|
|
|
|
|
Studies not included in the meta-analysis were narratively explored (Tables 1 and 2). Two papers reported results from one RCT, comparing two devices (HealthPatch and VisiMobile) with nurse measurements [37, 38]. However, they have not included the third group (control) in the analysis and not assessed any clinical outcomes, mostly exploring factors related to deterioration detection, failing to provide sufficient data to include in the meta-analysis. In the first paper from this RCT, the authors report that both HealthPatch and VisiMobile modified early warning scores (MEWS) were higher than the nurse measured MEWS, mostly due to RR measurements differences [38]. In the second paper (the full RCT) the authors identified positive and negative effects as well as barriers and facilitators for the use of these devices, such as the impact of AMS in a shorter length of stay and prevention of ICU admissions, additionally, a total of 17 patients, 2 relatives and 17 healthcare professionals reported to be expecting earlier deterioration detection using these wearables [37].
Another RCT evaluated wireless external fetal electrocardiography versus standard external monitoring [41]. We were unable to include this study in the meta-analysis as (1) the primary outcome of the study was the percentage of interpretable fetal HR data, (2) the population of interest is very different from the remaining studies and (3) the clinical outcomes analysed also differed (eg. length of labour, fetal Apgar score, etc.). Considering this, their results demonstrated no differences in maternal or neonatal clinical outcomes between groups. However, results did suggest an increased acceptance by patients and staff, with satisfaction scores significantly higher when compared to the standard monitor [41].
Included studies registration
Details of the clinical trials search are shown in Appendix 6. Of the ten included studies in this review, only seven were registered (most retrospectively, as per Appendix 7). Within these, all primary outcomes stated in the registration were reported in the main paper, as well as most of the secondary outcomes.
Study quality and risk of bias
The overall quality of included studies was moderate with some bias to take into account, as per Figs. 2 and 3. For the included RCTs, using the ROB2, two were identified as at “low risk” of bias [30, 41] and a further three were assessed as raising “some concerns” [27, 37], including the cluster RCT [29]. The risk of bias, assessed by the ROBINS-I was “moderate” for all before-and-after studies [26, 36, 39, 40]. See Appendix 8 for further details. The results of the bias assessment did not influence inclusion in the meta-analyses.
Primary outcomes
In total, data from seven studies were included in the meta-analysis of primary outcomes related to deterioration detection, analysed separately according to the three reported deterioration outcomes – ICU transfers, rapid response or cardiac arrest activation, and complications.
ICU transfers
A total of five studies reported ICU transfers and were included in this meta-analysis (data from 3565 patients, 1898 in the AMS group) [26, 29, 30, 36, 40]. Pooling of data indicated that use of AMS did reduce ICU transfer (RR, 0.87; 95% CI 0.66 to 1.15), but not statistically significantly (p = 0.32) (Fig. 4).
Rapid response or cardiac arrest activation
For this outcome, two before-and-after studies reporting rapid response team activation and another study reporting cardiac arrest calls were included (with data from 3214 patients, 1698 in the AMS group, Fig. 5) [26, 36, 40]. Pooled data for this outcome indicated AMS reduced RRT or cardiac arrest calls (RR, 0.84; 95% CI 0.69 to 1.01) with a p-value near statistical significance (p = 0.07).
All clinical complications
A total of five studies reported data on complication outcomes classed by the Clavien-Dindo system as grade I or II(with data from 1752 patients, 837 in the AMS group, Fig. 6). indicating the AMS group had a reduced risk of complications (RR, 0.77; 95% CI 0.44 to 1.32) however without statistical significance (p = 0.34) and with high heterogeneity between studies (I2 = 93%).
For the major complications (Fig. 7), we included 3 studies (with data from 546 patients, 296 in the AMS group) indicating the AMS group had reduced risk of major complications (RR, 0.55; 95% CI 0.24 to 1.30) however, with no statistical significance (p = 0.17).
Other deterioration detection outcomes not included in the meta-analysis
A few of the included studies also explored other deterioration detection outcomes, but in insufficient numbers to allow a meta-analysis. One cluster RCT [29] and one RCT [30] from the same research group compared the time to antibiotic administration in case of sepsis in the AMS group against the control group, finding this statistically insignificant in both studies (656.0 (95% CI 431.7-820.3) vs 1012.8 (95% CI 425.0-1600.6) minutes [29] and 551 (95% CI 296–805) vs 527 (95% CI 199–856)) [30].
Secondary outcomes
The two secondary outcomes of in-hospital mortality and hospital length of stay were also meta-analysed.
In-hospital mortality
For the outcome of in-hospital mortality, we included six studies (with data from 3760 patients, 1994 in the AMS group, Fig. 8) [26, 27, 29, 30, 36, 40], with one study reporting no deaths in either group (no estimates to be analysed in the meta-analysis) [27]. Our results indicated the AMS group had a reduced risk of mortality (RR, 0.48; 95% CI 0.18 to 1.29) but this reduction was not statistically significant (p = 0.15).
Hospital length of stay
A total of five studies were included for the outcome of hospital LoS (with data from 2911 patients, 1994 in the AMS group, Fig. 9) indicating a non-significant reduction in hospital length of stay for patients monitored using AMS (MD, -0.09; 95% CI -0.43 to 0.44, p = 0.63).
Other clinical outcomes not included in the meta-analysis
Studies also included other clinical outcomes, for example, two studies explored 30-day hospital readmission rates and showed mixed results, with one showing lower readmission rates in the AMS group [29] and the other slightly higher [30] in comparison with standard care.
Skraastad and colleagues indicated reduced time to post-operative mobilisation in the AMS group, 10.1 (95% CI 8.1–12.2) against 14.2 (95% CI 12.0-16.3) in the control group [27]. They also compared the number of NEWS measurements in their RCT, with 8.2 (95% CI 47.4-9.0) in the AMS group versus 3.4 (95% CI 3.1–3.6) in the standard care group. Additionally, there was a higher mean in opioid dose given in the AMS group, 25.5 (95% CI 20.9–30.0) vs 15.2 (95% CI 11.1–19.3) in the control arm; and more supplementary oxygen was given to 57/96 in the AMS group against 32/99 in the control group [27], that the authors defend being a result of the increased monitoring in the AMS group, facilitating pain and oxygen management of those patients, and promoting earlier mobilisation [27]. This study also
Exploratory outcomes
Alerting systems (Central station and mobile devices for alerts)
Some information about the alerting system was available in nine out of the ten included studies [26, 27, 29, 30, 36, 38–40, 44]. Five studies reported their development in reducing the number of alarms per patient per day (APDs). One reported having started with 11.41 APDs and conducted iterations down to 2.01 APDs, reducing the non-actionable alarms and modifying their vital sign limits and thresholds to reduce the rate of false alarms [26]. The authors focused on monitoring optimisation, reviewing and modelling the alarm data every few days and discussing with clinical managers whether widening vital sign parameters would create a significant reduction in alarm rates while still being clinically acceptable and sensible to deterioration detection [26]. In Downey and colleagues’ first study there was an unacceptable number of alerts sent to the nursing staff. After adjustments in the vital sign thresholds, the false alerts were reduced by 90% (30). This was addressed in their second RCT where a clinical fellow was visiting the wards daily to check the rate of false alarms and adjust thresholds and/or delays of the alerts as per clinical need (18,48). Despite this, two patients withdrew from the study due to “too many false alerts” (18). In two other studies, the authors just discussed the intention was to improve the rate of true positives and reduce false negatives/false alarms [37, 38].
Most alerting thresholds were pre-set and individualised as required, alerted through the central station and/or nurse mobile/pager/PDA, with the majority using audio alerts (Table 4). In one study the authors used a single risk score calculated from all vital signs (VSI) and based on modelling from a previous patient dataset, creating an alert when the VSI score was above the threshold for more than 4 out of 5 minutes [40]. Alerting parameters from the included studies are explored in Table 4.
In one study’s final version of the alerting system, hypotension, bradycardia and hypoxemia were tolerated for shorter periods than tachycardia or hypertension, unless the tachycardia resulted in hypotension. Additionally, the majority of the alerts in this final iteration were due to SpO2 (0.97 APDs) [26]. Another study found that the most accurate vital sign parameter was systolic blood pressure, which had a positive predictive value (PPV) of 97%, followed by high respiratory rate (PPV of 85%) and low SpO2 (PPV of 76%), indicating high sensitivity and reliability and a low false alarm rate. [36]
Table 3
Vital sign thresholds summary table. BP: blood pressure, DBP: diastolic blood pressure, HR: heart rate, MAP: mean arterial pressure, PDA: personal digital assistant, PR: pulse rate, RR: respiratory rate, SBP: systolic blood pressure, SMS: short message service, SpO2: peripheral oxygen saturation, T: temperature, VSI: Visensia Safety Index.
|
Vital sign thresholds (delay before alert in seconds)
|
Alert method
|
Study
|
HR/PR
|
RR
|
SpO2
|
BP
|
MAP
|
T
|
|
High
|
Low
|
High
|
Low
|
Low
|
High SBP
|
Low DBP
|
Low
|
|
Weller et al. 2018
|
HR: 150 (15)
PR: 150 (60)
|
HR: 39 (15)
PR: 39 (60)
|
35 (120)
|
4 (120)
|
85 (90)
|
200 (240)
|
|
58 (60)
|
|
Sound
Central station + nurse phone
|
Kisner et al. 2009
|
Individualised (immediate)
|
|
|
Pre-set individualised (immediate)
|
|
|
|
|
Sound
Pager or SMS to doctor and nurse
|
Verrilo et al. 2018
|
Pre-set (5)
|
Pre-set (120)
|
Pre-set (60)
|
Pre-set (120)
|
|
|
Sound
Central monitor + nurse mobile
|
Downey et al. 2018
|
Pre-set, individualised if required (immediate)
|
Pre-set, individualised if required (immediate)
|
|
|
|
|
Pre-set, individualised if required (immediate)
|
Sound
Mobile device to nurse
|
Downey et al. 2020
|
Pre-set, individualised if required (immediate)
|
Pre-set, individualised if required (immediate)
|
|
|
|
|
Pre-set, individualised if required (immediate)
|
Sound
Mobile device to nurse
|
Weenk et al. 2019 & 2020
|
Individualised (immediate)
|
Individualised (immediate)
|
Individualised (immediate)
|
Individualised (immediate)
|
|
Individualised (immediate)
|
Sound
Nurse station
|
Skraastad et al. 2020
|
As per NEWS score
|
As per NEWS score
|
As per NEWS score
|
As per NEWS score
|
|
As per NEWS score
|
Visual only
Warnings at patient bedside
|
|
|
Alerting score thresholds
|
|
|
|
Score name
|
Vital signs included in score
|
Range
|
Threshold
|
Time to alert
|
|
|
|
|
|
Watkinson et al. 2020
|
VSI
|
All
|
0 to 5
|
> 3.0 for more than 4 out of 5 minutes
|
On the fifth minute
|
|
|
|
|
Sound
Bedside + central station + nurse PDA
|
Clinical trial registries (other potentially eligible studies to be included)
A total of sixteen registrations were identified in the search and screened for eligibility. Six were excluded and six registrations refer to the included studies. A further four registrations were deemed potentially eligible to be included in our review and meta-analysis (Table 3). A registered cluster RCT [45] aimed to develop a two-tiered monitoring system to improve the care of patients at risk of clinical deterioration in general hospital wards. This registered study also included a subset of patients using wireless devices [45]. However, although the main results are published [32], no data were reported on the impact of wireless devices on the subset population and we were unable to make contact with the Principal Investigator to clarify publication status and request this subset of the AMS group data. A further registration [46] before-and-after study was potentially eligible and although the main results are published [33] a subset of patients (278) used at least one cableless sensor, but the author confirmed there were no data available on outcomes for this sub-set of wirelessly monitored patients [33]. The other two registrations did not publish their results at the time of our systematic literature search. The Principal Investigator of one prospective, observational cohort study confirmed the study results have been submitted and is under peer review [47]. We were unable to contact the Principal Investigator to clarify the status of the other study [48].
Table 4
Studies with potential for inclusion.
Year registered
|
Registration ID
|
Date start recruitment
|
Recruitment status
|
Reason for non-publication
|
2011
|
NCT01280942 [45]
|
January 2011
|
Completed
|
Main results published but not sub-group analysis with the wireless device. [32]
|
2012
|
NCT01692847
[46]
|
October 2012
|
Completed
|
Main results published but not sub-group analysis with the cableless device. [33]
|
2015
|
NCT02427828 [48]
|
March 2013
|
Completed
|
Unknown
|
2017
|
NCT03179267 [47]
|
September 2017
|
Completed
|
Under peer review
|