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Continuous monitoring of patient vital signs may improve patient outcomes. Head-worn displays (HWDs) can provide hands-free access to continuous vital sign information of patients in critical and acute care contexts and thus may reduce instances of unrecognized patient deterioration.
The purpose of the study is to conduct a systematic review of the literature to evaluate clinical, surrogate, and process outcomes when clinicians use HWDs for continuous patient vital sign monitoring.
The review was registered with PROSPERO (CRD42019119875) and followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. A literature search was conducted for articles published between January 1995 and June 2020 using the following databases: PubMed, Embase, CINAHL, PsycINFO, and Web of Science. Overall, 2 reviewers independently screened titles and abstracts and then assessed the full text of the articles. Original research articles that evaluated the clinical, surrogate, or process outcomes of head-mounted displays for continuous vital sign monitoring in critical care or acute care contexts were included.
Of the 214 records obtained, 15 (7%) articles met the predefined criteria and were included in this review. Of the 15 studies, 7 (47%) took place in a clinical context, whereas the remainder took place in a simulation environment. In 100% (7/7) of the studies that evaluated gaze behavior, changes were found in gaze direction with HWDs. Change detection improvements were found in 67% (2/3) of the studies evaluating changes in the participants’ ability to detect changes in vital signs. Of the 10 studies assessing the ease of use of the HWD, most participants of 7 (70%) studies reported that the HWD was easy to use. In all 6 studies in which participants were asked if they would consider using the HWD in their practice, most participants responded positively, but they often suggested improvements on the HWD hardware or display design. Of the 7 studies conducted in clinical contexts, none reported any clinical outcomes.
Although there is limited and sometimes conflicting evidence about the benefits of HWDs from certain surrogate and process outcomes, evidence for clinical outcomes is lacking. Recommendations are to employ user-centered design when developing HWDs, perform longitudinal studies, and seek clinical outcomes.
PROSPERO International Prospective Register of Systematic Reviews CRD42019119875; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=119875
Early recognition of patient deterioration can improve patient outcomes [
There are two approaches to in-hospital vital sign monitoring: intermittent and continuous. Intermittent monitoring involves the measurement and recording of vital signs at regular time intervals (eg, 30 minutes). Some research suggests that some patient deterioration may not be detected because of the gap between observations [
One of the impediments to implement continuous vital sign monitoring is that it can increase the burden on health care workers if algorithms are not used to limit nonactionable or nuisance alarms [
Head-worn displays (HWDs) are a type of wearable device that projects information in front of one eye (monocular) or both eyes (binocular) over a background that is either transparent or opaque. HWDs have been trialed in health care contexts for a variety of purposes, such as visual instruction and augmented reality during surgery, videoconferencing between physicians and consultants, and image and video recording for educational purposes [
HWDs offer several potential benefits in health care contexts. They allow clinicians to maintain sterility while accessing task-relevant information, which is beneficial in the clinical context [
The purpose of this review is to examine the evidence for the effectiveness of HWDs for continuous patient vital sign monitoring in hospital or patient transport environments. Recent reviews have surveyed the broad range of uses of HWDs in surgery [
This systematic review was performed in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. The review was registered with the International Prospective Register of Systematic Reviews (CRD42019119875) before the search process started.
We developed the search terms with the assistance of a professional librarian at The University of Queensland. The search strategy used keywords related to the concepts of
The inclusion criteria were as follows: (1) peer-reviewed qualitative, quantitative, or mixed methods studies (excluding gray literature, editorials, systematic or other reviews, and meta-analyses); (2) real or simulated critical care or acute care clinical contexts; (3) fully trained clinician or clinical trainee participants; (4) HWDs used for vital sign monitoring (excluding images or videos without vital sign information); (5) studies with or without a comparator; and (6) predefined clinical, surrogate, or process outcomes. The list of outcomes was developed prospectively in collaboration with 2 practicing clinicians to focus on outcomes relevant to the clinical context and is provided in Table S3 in
A standardized form was developed for the structured collection of data from each article, including publication details, study methodology, HWD details, and study outcomes; full details of the data collected are presented in Table S5 in
The risk of bias assessment considers the extent to which the design of a study and methods used are likely to have prevented bias [
A total of 214 citations were retrieved through a structured search of the 5 databases. Two additional records were identified through other sources. After removing duplicates, 170 articles were screened. In total, 2 authors (FE and IS) independently screened the titles and abstracts of 170 records against the inclusion and exclusion criteria, and 43 articles met all criteria. The reviewers were in agreement for 97.6% (166/170) records, and discrepancies were resolved through discussion with a third author (PS). The initial 2 authors (FE and IS) independently reviewed the full text of these articles against the inclusion and exclusion criteria, and 28 articles were excluded. The reviewers were in agreement for 100% (43/43) of the articles. A total of 15 articles met the predefined criteria for inclusion. Note that one article described 2 separate studies [
PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) study flowchart.
Approximately half of the studies (7/15, 47%) used a volunteer or convenience participant sample [
Summary of the studies included.
Study | Study design | Participants (n); context | Comparison condition | Type of head-worn display | Format of data;sourcea |
Beuchat et al, 2005 [ |
Randomized controlled trial with crossover design | Cardiovascular surgeons (n=4); simulated operating room (open heart surgery) | Standard monitoring | Binocular; opacity unspecified; Sony Glasstron | Waveforms and numbers; mirror |
Block et al, 1995 [ |
Case series | Anesthesiologists (n=11); operating room (anesthesia) | None | Monocular optical see-through; Reflection Technology Private Eye | Numbers; redesign |
Drake-Brockman et al, 2016 [ |
Case series | Anesthesiologists—pediatric (n=40); operating room (anesthesia) | None | Monocular optical see-through; Google Glass | Numbers; redesign |
Iqbal et al, 2016 [ |
Crossover trial with fixed order of presentation | Urologists (n=37); simulated operating room (prostatectomy) | Standard monitoring | Monocular optical see-through; Google Glass | Waveforms and numbers; not stated |
Liebert et al, 2016 [ |
Randomized controlled trial with crossover design | Surgical residents (n=14); simulated operating room (thoracostomy, bronchoscopy) | Standard monitoring | Monocular optical see-through; Google Glass | Waveforms and numbers; mirror |
Liu et al, 2009 [ |
Randomized controlled trial with crossover design | Anesthesiologists (n=6); operating room (anesthesia) | Standard monitoring | Monocular optical see-through; Microvision Nomad | Waveforms and numbers; limited replica |
Liu et al, 2009 [ |
Crossover design with Latin square assignment to order | Anesthesiologists (n=12); simulated operating room (anesthesia) | Standard monitoring | Monocular optical see-through; Microvision Nomad | Waveforms and numbers; redesign |
Liu et al, 2009 [ |
Crossover design with alternating allocation to conditions | Anesthesiologists (n=12); simulated operating room (anesthesia) | Standard monitoring | Monocular optical see-through; Microvision Nomad | Waveforms and numbers; redesign |
Ormerod et al, 2002 [ |
Crossover trial with alternative allocation to condition | Anesthesiologists (sample not stated); simulated operating room (anesthesia) | Standard monitoring | Monocular optical see-through; Microvision Nomad | Waveforms and numbers; not stated |
Sanderson et al, 2008 [ |
Crossover trial with Latin square assignment to order | Anesthesiologists (n=16); simulated operating room (anesthesia) | Standard monitoring | Monocular optical see-through; Microvision Nomad | Numbers; redesign |
Schaer et al, 2015 [ |
Randomized controlled trial with crossover design | Medical residents (n=7); simulated surgical setting (cardiac surgery) | Standard monitoring | Monocular optical see-through; Google Glass | Waveforms and numbers; redesign |
Schlosser et al, 2019 [ |
Randomized controlled trial with crossover design | Anesthesiologists—supervising (n=6); operating suite (multiple patient anesthesia) | Standard monitoring | Monocular opaque; Vuzix M300 | Waveforms and numbers; redesign |
Via et al, 2002 [ |
Case series | Anesthesiologists (n=12); operating room (anesthesia) | None | Binocular optical see-through; Kaiser Electro-Optics | Waveforms and numbers; mirror |
Vorraber et al, 2014 [ |
Case study | Surgeons (n=2); operating room (percutaneous transluminal angioplasty) | None | Monocular optical see-through; Google Glass | Waveforms and numbers; mirror |
Yoshida et al, 2014 [ |
Case study | Urologists (n=2); operating room (transurethral resection of the prostate) | None | Binocular opaque; Sony HMZ-T2 | Waveforms and numbers; redesign |
aSource refers to whether the
bLiu et al’s clinical study outcomes were reported over 2 papers; treatment here integrates findings from both studies [
Of 15 studies, 12 (75%) displayed a combination of waveforms and numbers on the HWD [
For the 13 studies with quantitative measures, quality ratings [
Summary of the clinical, surrogate, and process outcomes considered in each study.
Study | Clinical outcomes | Surrogate outcome categoriesa | Process outcome categoriesa | Quality rating (%) | |
|
|
|
|
Quantitative measure | Qualitative measure |
Beuchat et al, 2005 [ |
N/Ab | + Decreased missed vital sign changes |
+ Changed patterns of gaze behavior |
58 | —c |
Block et al, 1995 [ |
N/Md | N/M | + Clinician opinions | 25 | — |
Drake-Brockman et al, 2016 [ |
N/M | N/M | + Clinician opinions | 83 | — |
Iqbal et al, 2016 [ |
N/A | + Reduced time to detect vital sign changes | = Changed time to do other tasks |
63 | — |
Liebert et al, 2016 [ |
N/A | = Earlier identification of deterioration | + Changed patterns of gaze behavior |
92 | — |
Liu et al, 2009 [ |
N/M | N/M | += Changed patterns of gaze behavior |
88 | — |
Liu et al, 2009 [ |
N/A | = Increased unexpected events detected |
+ Changed patterns of gaze behavior |
75 | — |
Liu et al, 2009 [ |
N/A | += Increased unexpected events detected |
+ Changed patterns of gaze behavior |
75 | — |
Ormerod et al, 2002 [ |
N/A | N/M | + Changed patterns of gaze behavior |
29 | — |
Sanderson et al, 2008 [ |
N/A | = Increased unexpected events detected |
+ Clinician opinions | 83 | — |
Schaer et al, 2015 [ |
N/A | N/M | + Clinician opinions | 71 | — |
Schlosser et al, 2019 [ |
N/M | + Increased alarms detected |
+− Clinician opinions | 92 | 75 |
Via et al, 2002 [ |
N/M | N/M | + Clinician opinions | 59 | — |
Vorraber et al, 2014 [ |
N/M | N/M | + Changed patterns of gaze behavior |
— | 30 |
Yoshida et al, 2014 [ |
N/M | N/M | + Clinician opinions | — | 39 |
a“+” represents the positive effect of head-worn display; “−” represents the negative effect of head-worn display; “=” represents no difference between head-worn display and other conditions. If a study used more than one measure for an outcome, multiple symbols are shown.
bN/A: not applicable.
cNot relevant to this study.
dN/M: not measured.
eLiu et al’s clinical study outcomes were reported over 2 papers; treatment here integrates findings from both studies [
We extracted data for 9 predetermined surrogate outcomes that were subsequently divided into 4 categories: (1) vital sign changes, (2) alarm detection, (3) unexpected event detection, and (4) situation awareness.
Of 15 studies, 3 (20%) examined the participants’ ability to detect vital sign changes in simulated surgical settings. Overall, 2 of the studies found that the average time to detect abnormal vital signs was significantly faster with an HWD than with standard monitoring. In the first study, Beuchat et al [
In the second study, Iqbal et al [
One study examined whether the use of an HWD increased the number of auditory alarms detected by clinicians or reduced the time taken for clinicians to detect alarms. Schlosser et al [
Of 15 studies, 3 (20%) examined the effect of HWDs on the detection of unexpected events and the time taken to respond to these events. For unexpected events occurring on the HWD, such as hypertension or gas embolism, 2 simulator studies found that participants using the HWD did not detect more unexpected events [
Liu et al [
Our intended criterion for including situation awareness outcomes was that a validated measure should be used; none of the studies met this criterion. However, one study described nonvalidated measures of situation awareness, specifically self-reported awareness, and are reported here for completeness. Schlosser et al [
We extracted data for 5 predetermined process outcomes that were divided into 4 categories: (1) gaze behavior, (2) time for other tasks, (3) information sharing, and (4) clinicians’ opinions of HWDs.
Of 15 studies, 7 (47%) examined the gaze behavior of clinicians using an HWD. Of 7 studies, 5 found that clinicians using an HWD spent more time looking at the patient or the procedural field and less time looking at the monitor than when the HWD was not used [
Overall, 2 studies examined the effect of using an HWD on the time spent on tasks. In one study, Ormerod et al [
None of the studies considered the effect of HWDs on how clinicians share information.
Of 15 studies, 14 (93%) examined some aspects of clinicians’ opinions of HWDs for vital sign monitoring [
In 6 studies, clinicians were asked whether wearing the HWD was comfortable. In 5 of these studies, most clinicians reported that the HWD was comfortable to wear or did not report any discomfort [
Finally, in all 6 studies where clinicians were asked whether they would use the device again, most clinicians said yes, although sometimes noting improvements needed to the device or to the information presented [
The purpose of this review was to evaluate the impact of HWDs displaying continuous vital sign monitoring on clinical, surrogate, and process outcomes in critical and acute care contexts. Our systematic review of the literature shows that HWDs have been evaluated for continuous vital sign monitoring in 15 studies, including 7 conducted with patients in clinical environments. Clearly, HWDs can be technically implemented for vital sign monitoring, but the evidence for any overall benefit is mixed. None of the 7 clinical studies measured clinical outcomes. Across all 15 studies, there was only limited evidence that HWDs displaying patient vital signs improve surrogate outcomes or process outcomes.
The strongest and most consistent evidence for the benefit of HWDs relates to gaze behavior. Several studies have shown that wearing an HWD tends to increase the time that clinicians spend looking toward the patient relative to the patient monitor or anesthesia machine [
There is also consistent evidence that clinicians using an HWD may take less time to detect abnormal vital signs and may also detect more vital sign changes than clinicians using standard monitoring. However, this evidence comes from a limited number of studies—2 with significant results [
Evidence for whether HWDs affect clinicians’ detection of unexpected events signaled on an HWD is mixed. In 2 studies, there was no difference between HWDs and standard monitoring for detecting unexpected events [
For other outcomes, the evidence is mixed. HWDs are sometimes associated with improvements in alarm detection and the time required to complete tasks, but sometimes not. This makes it difficult to provide definitive conclusions regarding the effects that HWDs have on these outcomes. Further research is needed to determine the factors that might moderate the effect of HWDs on these outcomes. For situation awareness, the fact that no study has collected objective measures of the 3 levels of situation awareness by Endsley [
For more definitive conclusions to be drawn about the impact of HWDs on vital sign monitoring, the focus and quality of the research need to be improved. The quality assessment ratings ranged from 25% to 92%, indicating that there is room for improvement in study design and methods. Given that there is no strong evidence that HWDs worsened performance on any outcome measures reported, it is worth investing in higher-fidelity studies to improve the evidence base.
The inconsistent results may be partly explained by the use of small-scale, short-term studies with a focus on surrogate and process outcomes. Longitudinal studies may allow clinicians to adjust to the novelty of using an HWD and may reveal whether the benefits of HWDs emerge over time. Large-scale randomized control trials have not yet emerged, but clinically based studies focusing on clinically relevant outcomes will help clinical leaders decide whether HWDs should be implemented on a large-scale basis.
In the literature reviewed, there was little apparent attention to user-centered design principles [
No study in this literature review reported a systematic analysis of user needs. A requirements analysis was reported in only one of the 15 studies (Vorraber et al [
An examination of the HWD interfaces used in the literature also supports the assertion that a user-centered design approach may be worthwhile in future research. Of the 13 studies that reported the layout of the HWD interface, 4 presented the data in the same format on the HWD as on the standard patient monitor [
Evaluations of the impact of HWDs would be improved if researchers include tests that allow evidence to accumulate for or against the key outcomes listed in this review. For example, relatively few studies have tested whether HWDs render participants more or less able to detect changes in patient vital signs or to notice unexpected events. If future studies were to deliberately augment evidence for or against key claims, clinical leaders would be able to make more confident decisions about the viability of HWDs.
The purpose of this systematic review was to evaluate the benefits or otherwise of HWDs for continuous vital sign monitoring, using a set of predefined outcome categories. The strengths of the review are its scope and the breadth of outcomes considered for each study, revealing the considerable heterogeneity of approaches and findings in the area, and indicating areas for further research.
This review has several limitations. First, the heterogeneous nature of the literature poses a challenge to interpretation. Our search terms may not have captured all relevant publications if different key terms are used across different clinical contexts. However, we tried to address this through an iterative process for developing search terms in collaboration with librarians and clinicians. Second, the quality of evidence ranged considerably across the included studies. Third, there may be evidence in other contexts that HWDs can improve or worsen performance that is relevant to continuous vital sign monitoring in acute and critical care contexts; however, finding such cases was outside the scope of the review. Finally, there are other ways to convey continuously captured vital signs to clinicians. For example, auditory, haptic, or multimodal displays may meet clinicians’ requirements for continuous patient monitoring. However, this was beyond the scope of this review.
Certain surrogate and process outcomes suggest that HWDs may assist continuous vital sign monitoring, but to date, there have been no evaluations of whether HWDs improve clinical outcomes. The most consistent evidence across the corpus of studies reviewed is that HWDs can improve clinicians’ detection of vital sign changes and reduce the time clinicians spend looking at the patient monitor. However, for other surrogate and process outcomes, the evidence is mixed. A user-centered design approach can produce designs and evaluations that are more focused on the desired outcomes. Further research is required to determine whether, in what contexts, and under what conditions HWDs can reliably support the early recognition of patient deterioration and potentially reduce patient harm.
Supplementary material including search terms, search strategy, a full list of outcome questions, study inclusion and exclusion criteria, data extraction categories, the full quality assessment for all included studies, and a summary table of the clinical, surrogate, and process outcomes assessed in each study.
head-worn display
Preferred Reporting Items for Systematic Reviews and Meta-analyses
The authors thank Dr Andrew Perry and Mr Stuart Keynes from SAAS MedSTAR for helpful conversations at the outset of this research, Miranda Newell, Librarian, from The University of Queensland Library for help with formulating the searches, and members of the Cognitive Engineering Research Group who gave feedback on an early version of the manuscript. This research was supported by Australian Research Council Discovery Project DP180103702.
None declared.