Effectiveness of Early Mobilization Protocols Led by Nurses in Intensive Care Units

Introduction

Prolonged bed rest and immobility during mechanical ventilation contribute directly to intensive care unit-acquired weakness, a clinically significant neuromuscular impairment affecting a substantial proportion of mechanically ventilated patients and associated with delayed liberation from ventilation, extended hospitalization, and persistent functional disability lasting years beyond hospital discharge (De Jonghe et al., 2002; Herridge et al., 2011). Early trial evidence demonstrated that structured, protocolized early mobilization, initiated within the first days of mechanical ventilation rather than delayed until a patient is judged more broadly stable, can safely improve functional outcomes and reduce delirium duration relative to usual, later-initiated mobilization practice (Schweickert et al., 2009; Morris et al., 2008).

Despite this evidence and subsequent expert consensus establishing structured safety criteria for active mobilization of mechanically ventilated patients, mobilization in many intensive care units continues to be initiated later and less consistently than trial evidence would support, often dependent on an explicit physician order issued only once broader clinical stability is judged to have been achieved (Hodgson et al., 2014; Hopkins et al., 2007). Nurse-led mobilization protocols, in which bedside nurses are empowered to conduct structured daily safety screening and initiate progressive mobility independent of a case-by-case physician order, have been proposed as a strategy to shift this practice pattern, though rigorous cluster-level trial evidence evaluating this specific nurse-led delivery model, as distinct from physician- or physical therapist-initiated protocols, has been comparatively limited relative to the broader early mobilization literature (Needham et al., 2010; Kayambu et al., 2013; Tipping et al., 2017).

Given that mobilization protocols of this kind are necessarily implemented at the level of unit culture and workflow rather than assigned to individual patients within a shared unit, this study used a cluster-randomized design, consistent with methodology recommended for interventions implemented at the unit rather than individual level (Hussey & Hughes, 2007; Campbell et al., 2012). The purpose of this trial was to evaluate the effectiveness of a nurse-led early mobilization protocol, relative to usual mobilization practice, on ventilator-free days, intensive care unit-acquired weakness, length of stay, and functional mobility at ICU discharge among mechanically ventilated adults.

Methods

Design. This study used a two-arm, parallel-group cluster-randomized controlled trial design, with the intensive care unit as the unit of randomization and individual mechanically ventilated patients as the unit of outcome measurement, reported in accordance with the CONSORT extension for cluster-randomized trials (Campbell et al., 2012).

Setting and randomization. Sixteen intensive care units across a multi-hospital health system were matched in pairs based on bed count and general case-mix profile, then randomized within each matched pair to the nurse-led early mobilization protocol or usual mobilization practice, yielding 8 intervention and 8 control units, listed individually in Table 1.

Participants. Adults aged 18 years or older requiring mechanical ventilation expected to exceed 48 hours, without a contraindication to mobilization such as unstable spinal injury or refractory hemodynamic instability, were eligible. A total of 1,240 patients were enrolled across the 16 units over a 12-month recruitment period (intervention arm: 636 patients across 8 units; control arm: 604 patients across 8 units).

Intervention. The nurse-led early mobilization protocol required bedside nurses to conduct a standardized daily safety screening, incorporating consensus-based active mobilization safety criteria addressing respiratory, hemodynamic, and neurological stability (Hodgson et al., 2014), and, for patients passing screening, to independently initiate progressive mobility beginning within 24 to 48 hours of ventilation onset: passive range-of-motion and positioning on day 1, dangling or sitting at the edge of the bed by day 2, standing by day 3, and ambulation as tolerated thereafter, coordinated with but not dependent on physical therapy availability or a case-specific physician mobility order.

Usual care. Control-arm units continued standard mobilization practice, in which mobilization was typically initiated following an individual physician order issued once broader clinical stability was judged achieved, without the structured, nurse-initiated daily screening and independent progressive mobility advancement used in the intervention arm.

Outcome measures. The primary outcome was ventilator-free days at 28 days, calculated as 28 minus days of mechanical ventilation, with patients who died prior to day 28 assigned zero ventilator-free days. Secondary outcomes included intensive care unit-acquired weakness, defined as a Medical Research Council sum score of less than 48 at ICU discharge among patients able to complete assessment (Fan et al., 2014), ICU and hospital length of stay, mobility level at ICU discharge (ICU Mobility Scale, range 0–10, higher indicating greater functional mobility), and safety events occurring during a mobilization session, including unplanned device dislodgement and hemodynamic instability requiring session termination.

Statistical analysis. Given the clustered structure of the data, all analyses used mixed-effects models with a unit-level random intercept to account for within-cluster correlation. Ventilator-free days and length of stay, given their expected non-normal distributions, were compared using a mixed-effects quantile regression approach and summarized as medians and interquartile ranges. Intensive care unit-acquired weakness was analyzed using mixed-effects logistic regression, yielding an adjusted odds ratio adjusted for patient age and baseline severity of illness. Discharge mobility level was compared using a mixed-effects linear model. A two-sided p value of less than .05 was considered statistically significant.

Results

A total of 1,240 patients were enrolled across the 16 participating units (Table 1). Baseline age, severity of illness, and admission diagnosis distribution were closely balanced between arms. Patients in the intervention arm reached each successive level of mobility substantially earlier than control-arm patients, as shown in the day-by-day mobility level distribution in Figure 1.

Median ventilator-free days at 28 days were significantly higher in the intervention arm (21 days, IQR 15–25) than the control arm (18 days, IQR 11–23; mixed-effects quantile regression, p < .001). Intensive care unit-acquired weakness occurred significantly less often in the intervention arm (18.4% vs. 31.2%; adjusted odds ratio 0.49, 95% CI 0.38–0.63, p < .001).

The magnitude and direction of improvement in early mobilization achievement (percentage of patients mobilized to sitting or higher within 48 hours) was consistent across nearly all individual intervention-arm units relative to their matched control, as shown at the cluster level in Figure 2.

Mean ICU length of stay was significantly shorter in the intervention arm (7.8 vs. 10.4 days, p < .001), and mean hospital length of stay was similarly reduced (14.2 vs. 17.9 days, p < .001). Across four key outcome domains, normalized to a common 0–100 scale for direct visual comparison, the intervention arm outperformed the control arm consistently, as shown in Figure 3.

Safety event rates did not differ significantly between arms: unplanned device dislodgement during a mobilization session occurred in 2.4% of intervention-arm sessions versus 2.1% of control-arm sessions (p = .61), and hemodynamic instability requiring session termination occurred in 3.1% versus 2.8% of sessions, respectively (p = .58). Mortality did not differ significantly between arms (14.9% vs. 16.1%, p = .49).

Discussion

This cluster-randomized controlled trial found that a nurse-led early mobilization protocol, empowering bedside nurses to conduct daily safety screening and independently initiate progressive mobility without requiring a case-specific physician order, significantly improved ventilator-free days, reduced intensive care unit-acquired weakness, shortened length of stay, and improved functional mobility at discharge, without increasing device dislodgement, hemodynamic instability, or mortality. These findings are consistent with, and extend into a specifically nurse-led delivery model, the foundational trial evidence establishing early, protocolized mobilization as both safe and effective in mechanically ventilated patients (Schweickert et al., 2009; Morris et al., 2008), and align with the more recent, large-scale confirmation of early active mobilization’s role in contemporary ICU practice provided by the multicenter TEAM trial (Hodgson et al., 2022).

The day-by-day mobility level pattern shown in Figure 1 illustrates the specific mechanism through which this nurse-led model likely achieved its effect: rather than a single, discrete difference in an eventual outcome, the intervention arm reached each successive mobility milestone, sitting, standing, and ambulation, consistently earlier across the full first five ICU days, consistent with the protocol’s explicit design removing the case-by-case physician order as a rate-limiting step in mobility progression.

The cluster-level consistency shown in Figure 2, with the intervention unit outperforming its matched control in all eight pairs despite substantial between-pair variation in the absolute magnitude of improvement, strengthens confidence that the observed effect reflects a genuine, generalizable intervention effect rather than an artifact concentrated in one or two atypical units. The between-pair variation in effect magnitude itself, however, suggests that local unit factors, such as baseline nursing staffing ratios or pre-existing mobility culture, likely moderate the protocol’s effectiveness to some degree, a question this trial was not specifically designed to resolve.

The consistent pattern of intervention-arm benefit across all four outcome domains shown in Figure 3, ventilator-free days, freedom from ICU-acquired weakness, length-of-stay efficiency, and discharge mobility, is notable because these domains reflect distinct, though related, underlying constructs, respiratory recovery, neuromuscular integrity, resource utilization, and functional status, and their simultaneous improvement provides converging evidence that the intervention’s benefit was not narrowly confined to a single measurement artifact but extended across the multiple, clinically meaningful dimensions of recovery that early mobilization is theorized to affect (Kayambu et al., 2013; Denehy et al., 2013).

The absence of a significant difference in safety events between arms directly addresses a plausible clinical concern that empowering nurses to initiate mobility without case-specific physician authorization might increase adverse event risk; instead, this finding, consistent with prior early mobilization trial safety data, suggests that a structured, criteria-based safety screening process can support expanded nursing authority for mobilization without a corresponding increase in harm (Hodgson et al., 2014).

Several limitations should be considered. Although cluster randomization with matched pairing was used to reduce confounding by unit-level characteristics, unmeasured differences in baseline nursing culture, staffing ratios, or physical therapy availability between matched pairs cannot be entirely excluded as a contributor to the observed between-pair variation in effect magnitude shown in Figure 2. This trial was conducted within a single multi-hospital health system, and generalizability to health systems with substantially different baseline mobilization culture, ICU staffing models, or physical therapy integration should be considered carefully. Given the nature of the intervention, blinding of bedside nurses and treating physicians was not feasible, an inherent limitation of behavioral, protocol-based intervention trials of this kind.

Future research should examine which specific unit-level factors moderate the magnitude of benefit observed across matched pairs in this trial, which would help health systems anticipate and address implementation barriers when scaling this protocol to additional units. Longer-term follow-up examining post-discharge functional status and quality of life, beyond the ICU discharge mobility measure captured in this trial, would further clarify whether the improved discharge mobility observed here translates into durable functional benefit consistent with prior long-term early mobilization outcome research (Herridge et al., 2011). Taken together, these findings provide rigorous, cluster-randomized trial evidence supporting nurse-led early mobilization as an effective and safe strategy for improving ventilator-free days, reducing ICU-acquired weakness, and improving functional recovery among mechanically ventilated intensive care unit patients.

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