Limb occlusion pressure-based individualized tourniquet pressure management in patients undergoing internal fixation for extremity fractures: a prospective comparative feasibility study

Abstract

Objective

This study aimed to evaluate the feasibility of limb occlusion pressure (LOP)-based individualized tourniquet pressure management and to quantify the reduction in applied tourniquet pressure compared with a traditional fixed-pressure protocol in patients undergoing internal fixation for extremity fractures.

Methods

A prospective comparative study was conducted at Civil Aviation Shanghai Hospital from January to September 2025. Patients undergoing internal fixation for extremity fractures were enrolled and allocated to either the LOP-based group (n = 171) or the traditional fixed-pressure group (n = 235) according to the attending surgical team and operative scheduling, without randomization. The LOP-based group received individualized tourniquet pressure based on preoperative LOP measurement plus a safety margin, while the control group received standardized pressures (40–50 kPa; 300–375 mmHg). The primary outcome was applied tourniquet inflation pressure. Secondary outcomes included demographic characteristics, extremity location, operative duration, and subgroup analyses stratified by extremity location, age, and sex; multivariable linear regression was performed to adjust for potential confounders.

Results

The LOP-based group demonstrated significantly lower mean tourniquet pressure compared with the traditional group (32.82 +/- 3.63 kPa [246 +/- 27 mmHg] versus 48.21 +/- 3.84 kPa [362 +/- 29 mmHg]; mean difference: 15.39 kPa; 95% CI: 14.66–16.12; P < 0.001), representing a 31.93% reduction; the difference remained significant after adjustment for extremity location, age, and sex (adjusted mean difference: 15.71 kPa; 95% CI: 15.36–16.06; P < 0.001). Baseline characteristics including age (46.09 +/- 15.20 versus 47.51 +/- 15.66 years; P = 0.361), sex distribution (P = 0.809), extremity location (P = 0.457), and operative duration (82.80 +/- 46.64 versus 80.55 +/- 43.50 min; P = 0.618) were comparable between groups. Within the LOP-based group, applied pressure was lower for upper than for lower extremity procedures (26.24 +/- 4.21 versus 34.16 +/- 1.30 kPa; P < 0.001), while exploratory analyses revealed no significant pressure variations across sex (male: 32.97 +/- 3.52 kPa; female: 32.53 +/- 3.85 kPa; P = 0.445) or age categories (< 40, 40–59, >=60 years; P = 0.807). All procedures achieved adequate intraoperative hemostasis without pressure escalation.

Conclusions

LOP-based individualized tourniquet pressure management was feasible and achieved a substantial reduction in applied tourniquet pressure while maintaining adequate intraoperative surgical field visualization in extremity fracture internal fixation. Applied pressure varied with extremity location but was independent of patient age and sex. Because patient-centered clinical outcomes were not assessed, these findings demonstrate the feasibility and pressure-reducing effect of LOP-based protocols rather than proven clinical superiority; randomized trials with clinical endpoints are warranted.

Introduction

Pneumatic tourniquets constitute an indispensable component of contemporary extremity surgery, providing a bloodless operative field that facilitates precise anatomical visualization and reduces intraoperative blood loss [1]. Since their introduction in modern orthopedic practice, tourniquets have become standard equipment in procedures ranging from fracture fixation to arthroplasty, with utilization rates exceeding 90% in extremity surgery [2, 3]. However, the application of excessive tourniquet pressure remains a significant concern, as supraphysiologic compression can precipitate a spectrum of complications including nerve palsy, muscle ischemia-reperfusion injury, postoperative pain exacerbation, and venous thromboembolism [4, 5].

Traditional tourniquet protocols typically employ standardized fixed pressures based on anatomical location-commonly 250–300 mmHg (33.3–40.0 kPa) for upper extremities and 300–350 mmHg (40.0-46.7 kPa) for lower extremities-without accounting for individual patient characteristics [6, 7]. This uniform approach, while ensuring adequate hemostasis across diverse patient populations, inevitably subjects many individuals to pressures substantially exceeding the minimum necessary for arterial occlusion. Contemporary evidence suggests that such excessive pressures correlate with increased postoperative pain, prolonged tourniquet site discomfort, and delayed nerve conduction recovery [4, 8, 9].

The concept of limb occlusion pressure (LOP) represents a paradigm shift toward individualized tourniquet management. LOP is defined as the minimum pressure required to completely occlude arterial blood flow in a specific limb, determined through real-time Doppler ultrasound or photoplethysmographic monitoring [10, 11]. By establishing the patient-specific occlusion threshold and adding a standardized safety margin, clinicians can achieve effective hemostasis while minimizing tissue compression beyond physiologic requirements. Recent randomized controlled trials in anterior cruciate ligament reconstruction and total knee arthroplasty have demonstrated that LOP-based protocols reduce applied pressure and postoperative pain without compromising surgical field quality [12–14].

Despite accumulating evidence supporting LOP-guided tourniquet application in elective orthopedic procedures, data specifically addressing extremity fracture surgery remain limited. Fracture patients present unique considerations including potential soft tissue swelling, variable limb circumference, and the necessity for adequate visualization in anatomically disrupted operative fields [15, 16]. Whether acute soft tissue edema affects the reliability of LOP measurement in the trauma setting has not been systematically studied. Furthermore, the relationship between LOP-determined pressures and patient demographic factors such as age, sex, and body habitus requires clarification to establish the generalizability of individualized protocols across diverse patient populations.

The present study aimed to evaluate the feasibility and pressure-reducing effect of LOP-based tourniquet pressure management in patients undergoing internal fixation for extremity fractures. We hypothesized that individualized pressure determination would achieve substantial pressure reduction compared with traditional fixed protocols while maintaining adequate surgical hemostasis. Secondary objectives included characterizing the distribution of LOP-based pressures and examining potential variations across extremity locations and demographic subgroups.

Materials and methods

Study design and setting

This prospective comparative study was conducted at our Hospital, from January to September 2025. The study protocol was reviewed and approved by the Medical Ethics Committee (Approval No.: 2025-01; Date: January 23, 2025). All participants provided written informed consent prior to enrollment. The study was designed and reported with reference to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines, applying the cohort-study checklist items appropriate to this non-randomized comparative design.

Participants

Consecutive patients scheduled for internal fixation of extremity fractures requiring tourniquet application were screened for eligibility. Inclusion criteria comprised: (1) age > = 18 years; (2) closed fractures of the upper or lower extremity amenable to internal fixation; (3) American Society of Anesthesiologists (ASA) physical status classification I-III; and (4) provision of informed consent. Exclusion criteria included: (1) peripheral vascular disease or arterial insufficiency; (2) previous tourniquet-related complications; (3) coagulopathy or therapeutic anticoagulation; (4) severe soft tissue injury precluding tourniquet application; (5) polytrauma requiring concurrent procedures; and (6) incomplete intraoperative tourniquet pressure documentation.

Intervention protocol

Patients were allocated to either the LOP-based observation group or the traditional fixed-pressure control group based on the attending surgical team and operative scheduling; no randomization was performed. All procedures were performed by fellowship-trained orthopedic trauma surgeons with standardized perioperative protocols.

LOP-based group (observation): Preoperative LOP determination was performed using a validated automated tourniquet system (Zimmer A.T.S. 4000) equipped with photoplethysmographic sensors. With the patient supine and the limb positioned at heart level, the tourniquet cuff was applied to the proximal thigh (lower extremity) or upper arm (upper extremity) according to the manufacturer specifications. The system automatically inflated the cuff incrementally while monitoring distal pulse signals, identifying the minimum pressure at which arterial flow cessation occurred. The operative tourniquet pressure was subsequently set at LOP plus a safety margin of 40–60 mmHg (5.3-8.0 kPa) for upper extremities and 60–80 mmHg (8.0-10.7 kPa) for lower extremities, consistent with current evidence-based recommendations [17–19].

Traditional group (Control): Tourniquet pressure was determined according to conventional institutional protocols, employing standardized pressures of 40 kPa (approximately 300 mmHg) for upper extremity procedures and 50 kPa (approximately 375 mmHg) for lower extremity procedures, irrespective of individual patient characteristics.

Outcome measures

The primary outcome was tourniquet inflation pressure (kPa) applied during surgery. Secondary outcomes included baseline demographic characteristics (age, sex), extremity location (upper versus lower, determined from the surgical procedure and diagnosis), operative parameters (surgical duration), and surgical adequacy assessment (adequate hemostasis defined as satisfactory visualization without surgeon-reported need for pressure adjustment). Tourniquet time was prespecified as a secondary outcome; however, cuff inflation and deflation times were not consistently documented in the operative records, precluding a reliable analysis of this variable.

Statistical analysis

Continuous variables were expressed as mean +/- standard deviation (SD) and compared using independent samples t-tests (Welch’s test where variances were unequal) following confirmation of normality through Shapiro-Wilk testing. Non-normally distributed variables were analyzed using Mann-Whitney U tests. Categorical variables were presented as frequencies and percentages, with group comparisons performed using chi-square tests or Fisher exact test as appropriate. Subgroup analyses examined pressure variations across extremity location, sex, and age categories (< 40, 40–59, >=60 years) using t-tests or one-way analysis of variance (ANOVA) as appropriate; these subgroup analyses were considered exploratory, and no adjustment for multiple comparisons was applied. Multivariable linear regression was used to estimate the between-group pressure difference adjusted for extremity location, age, and sex, and to examine determinants of applied pressure within the LOP-based group. Effect sizes were calculated using Cohen d for between-group comparisons and were interpreted in the context of the protocol-driven design. A two-tailed P value < 0.05 was considered statistically significant. All analyses were performed using Python 3.12 with SciPy (version 1.11) and Pandas (version 2.1) statistical packages.

Results

Patient characteristics

During the study period, 406 patients with complete tourniquet pressure documentation were analyzed, comprising 171 in the LOP-based group and 235 in the traditional group; screened patients lacking intraoperative pressure documentation were excluded. Baseline demographic and operative characteristics are summarized in Table 1. The groups were well-balanced with respect to age (LOP-based: 46.09 +/- 15.20 years; traditional: 47.51 +/- 15.66 years; P = 0.361), sex distribution (male: 65.50% versus 63.83%; P = 0.809), extremity location (upper extremity: 16.96% versus 20.43%; P = 0.457), and operative duration (82.80 +/- 46.64 versus 80.55 +/- 43.50 min; P = 0.618). No statistically significant differences were observed in baseline characteristics between groups; nevertheless, the non-randomized allocation precludes exclusion of residual confounding.

Table 1.

Baseline demographic and operative characteristics

Characteristic	LOP-based Group (n = 171)	Traditional Group (n = 235)	P value
Age, years	46.09 +/- 15.20	47.51 +/- 15.66	0.361
Sex, n (%)			0.809
Male	112 (65.50)	150 (63.83)
Female	59 (34.50)	85 (36.17)
Extremity location, n (%)			0.457
Upper extremity	29 (16.96)	48 (20.43)
Lower extremity	141 (82.46)	186 (79.15)
Pelvis	1 (0.58)	1 (0.43)
Operative duration, min	82.80 +/- 46.64	80.55 +/- 43.50	0.618

Values are presented as mean +/- SD or n (%). P values were calculated using independent samples t-test for continuous variables and chi-square test for categorical variables. The P value for extremity location compares the proportion of upper versus lower extremity procedures between groups. Abbreviations: LOP, limb occlusion pressure; SD, standard deviation

Primary outcome: tourniquet pressure comparison

The LOP-based group demonstrated substantially lower mean tourniquet pressure compared with the traditional group (32.82 +/- 3.63 kPa versus 48.21 +/- 3.84 kPa; mean difference: 15.39 kPa; 95% CI: 14.66–16.12 kPa; P < 0.001) (Table 2; Fig. 1). This represented a 31.93% reduction in applied tourniquet pressure. The between-group difference remained essentially unchanged after multivariable adjustment for extremity location, age, and sex (adjusted mean difference: 15.71 kPa; 95% CI: 15.36–16.06 kPa; P < 0.001). The standardized effect size was large (Cohen d = 4.10); however, because the two protocols were designed to apply different pressure levels (individualized versus fixed values), this effect size largely reflects the protocol-driven nature of the comparison and should not be interpreted as evidence of clinical benefit.

Table 2.

Comparison of tourniquet pressure between groups

Parameter	LOP-based Group (n = 171)	Traditional Group (n = 235)	P value
Mean pressure, kPa	32.82 +/- 3.63	48.21 +/- 3.84	< 0.001
Median pressure, kPa	34.00	50.00	-
Range, kPa	23.00–36.00	40.00–50.00	-
95% CI, kPa	32.27–33.37	47.72–48.71	-
Mean difference, kPa	15.39 (95% CI: 14.66–16.12)		< 0.001
Pressure reduction, %	31.93		-
Cohen d	4.10		-

Values are presented as mean +/- SD unless otherwise indicated. P values were calculated using independent samples t-test. Because the two protocols were designed to apply different pressure levels, the large effect size (Cohen d) largely reflects the protocol-driven comparison and should not be interpreted as evidence of clinical benefit. Conversion: 1 kPa = 7.5 mmHg. Abbreviations: CI, confidence interval; LOP, limb occlusion pressure

Fig. 1.

Comparison of tourniquet pressure between limb occlusion pressure (LOP)-based and traditional groups. Violin plots with embedded box plots demonstrate the distribution of tourniquet pressure values. Individual data points are overlaid (jittered). Diamond markers indicate group means. The LOP-based group exhibited significantly lower pressure compared with the traditional group (32.82 +/- 3.63 kPa versus 48.21 +/- 3.84 kPa; P < 0.001). ***P < 0.001. Conversion: 1 kPa = 7.5 mmHg

Notably, the pressure distributions exhibited distinctly different patterns between groups (Fig. 2). The LOP-based group demonstrated a continuous, approximately normal distribution ranging from 23 to 36 kPa, reflecting individualized pressure determination based on patient-specific LOP measurements. In contrast, the traditional group exhibited a bimodal distribution concentrated at two fixed values: 50 kPa (82.13% of patients) and 40 kPa (17.87% of patients), consistent with standardized protocol application based on anatomical location; the control-group pressure distribution therefore indirectly encodes extremity location.

Fig. 2.

Distribution of tourniquet pressure values. (A) LOP-based group demonstrating continuous, approximately normal distribution (range: 23–36 kPa) reflecting individualized pressure determination. (B) Traditional group exhibiting bimodal distribution concentrated at fixed protocol values (40 kPa: 17.87%; 50 kPa: 82.13%). Dashed vertical lines indicate group means

Subgroup analyses

Within the LOP-based group, subgroup analyses were performed across extremity location and demographic categories (Table 3; Fig. 3). Applied pressure differed markedly by extremity location: upper extremity procedures received significantly lower pressures than lower extremity procedures (26.24 +/- 4.21 kPa; n = 29 versus 34.16 +/- 1.30 kPa; n = 141; mean difference: 7.92 kPa; 95% CI: 6.38–9.47; P < 0.001), which accounts for the lower tail of the observed pressure range. In a multivariable model within the LOP-based group, lower extremity location was independently associated with higher applied pressure (+ 8.04 kPa; 95% CI: 7.20–8.87; P < 0.001), whereas age (P = 0.066) and sex (P = 0.446) were not. Mean tourniquet pressure did not differ significantly between male (32.97 +/- 3.52 kPa; n = 112) and female (32.53 +/- 3.85 kPa; n = 59) patients (t = 0.766; P = 0.445). Similarly, age-stratified analysis demonstrated comparable pressures across categories: <40 years (32.73 +/- 4.03 kPa; n = 64), 40–59 years (32.71 +/- 3.55 kPa; n = 68), and > = 60 years (33.15 +/- 3.11 kPa; n = 39; ANOVA F = 0.214; P = 0.807). These exploratory findings suggest that LOP-determined tourniquet pressure is driven principally by extremity location and individual physiological characteristics rather than by age or sex; however, these subgroup analyses were not powered for definitive inference and should be interpreted as hypothesis-generating.

Table 3.

Subgroup analysis of tourniquet pressure in the LOP-based group

Subgroup	n	Pressure, kPa	P value
Overall	171	32.82 +/- 3.63	-
Extremity location			< 0.001
Upper extremity	29	26.24 +/- 4.21
Lower extremity	141	34.16 +/- 1.30
Sex			0.445
Male	112	32.97 +/- 3.52
Female	59	32.53 +/- 3.85
Age category			0.807
<40 years	64	32.73 +/- 4.03
40–59 years	68	32.71 +/- 3.55
>=60 years	39	33.15 +/- 3.11

Values are presented as mean +/- SD. P values were calculated using Welch’s t-test for extremity location and sex comparisons and one-way ANOVA for age category comparison. Subgroup analyses are exploratory and were not adjusted for multiple comparisons. Abbreviations: ANOVA, analysis of variance; LOP, limb occlusion pressure.

Fig. 3.

Subgroup analysis of tourniquet pressure in the LOP-based group. Forest plot displaying mean pressure with 95% confidence intervals across demographic subgroups. The dashed vertical line represents the traditional group mean (48.21 kPa) for reference. No significant differences were observed across sex (P = 0.445) or age categories (P = 0.807); these exploratory analyses suggest that LOP-determined pressure does not vary systematically with demographic factors

Surgical adequacy

All procedures in both groups achieved satisfactory hemostasis with adequate operative field visualization. No cases required intraoperative tourniquet pressure adjustment due to inadequate hemostasis. Surgeon-reported operative field quality was comparable between groups, with no documented instances of compromised visibility attributable to the reduced pressures in the LOP-based group. Hemostatic adequacy was assessed qualitatively by the operating team without a formal grading scale, and objective measures such as estimated blood loss or transfusion requirements were not collected.

Discussion

This prospective comparative study demonstrates that LOP-based individualized tourniquet pressure management is feasible in extremity fracture surgery and achieves a substantial 31.93% reduction in applied pressure compared with traditional fixed protocols. Because the two groups were assigned to different pressure-setting rules, a lower applied pressure in the LOP-based group was expected by design; the large effect size (Cohen d = 4.10) therefore quantifies successful implementation of the individualized protocol rather than a treatment effect on a shared clinical endpoint. Importantly, the mean reduction of 15.39 kPa (approximately 115 mmHg) in applied pressure persisted after adjustment for extremity location, age, and sex (adjusted difference: 15.71 kPa), indicating that the finding is not explained by case-mix differences in extremity distribution.

Our findings align with and extend recent literature supporting LOP-guided tourniquet application across various orthopedic procedures. Aflatooni et al.¹² reported that individualized LOP yielded decreased postoperative pain and narcotic use compared with standard pressure during anterior cruciate ligament reconstruction. Yildirim et al.⁴ demonstrated through intraoperative neuromonitoring that lower tourniquet pressures resulted in less nerve conduction impairment and faster recovery following tourniquet deflation. The present study extends these observations to the trauma setting, confirming the feasibility of LOP-based protocols in fracture surgery where surgical complexity and hemostasis requirements may differ from elective procedures.

The continuous distribution of LOP-based pressures observed in our study, ranging from 23 to 36 kPa, reflects the substantial inter-individual variability in physiological occlusion thresholds that traditional fixed protocols fail to accommodate. Factors influencing LOP include limb circumference, cuff width and design, soft tissue composition, arterial compliance, and systemic blood pressure [11, 20, 21]. Consistent with this physiology, applied pressures in the LOP-based group were substantially lower for upper than for lower extremity procedures (26.24 versus 34.16 kPa), and extremity location was the dominant determinant of applied pressure in the adjusted analysis. In contrast, our exploratory subgroup analyses demonstrated that LOP-determined pressures did not vary significantly across age or sex categories, suggesting that individualized measurement captures physiological variation that is not predictable from demographic factors alone; age- or sex-specific adjustment algorithms therefore appear unnecessary, although this inference remains exploratory. Unlike simplified alternatives such as systolic blood pressure plus a fixed margin (e.g., SBP + 100 mmHg), which account for blood pressure but not for limb- and cuff-related factors, direct LOP measurement integrates all of these determinants. Because intraoperative blood pressure was not recorded in our dataset, we could not directly examine the correlation between systolic blood pressure and measured LOP; this physiological comparison merits dedicated study.

The contrast between the continuous distribution in the LOP-based group and the bimodal distribution in the traditional group (concentrated at 40 and 50 kPa) illustrates the inherent limitations of standardized protocols. While fixed pressures ensure adequate hemostasis across virtually all patients through application of supraphysiologic levels, they inevitably subject a substantial proportion of individuals to unnecessary tissue compression. Tan et al. [22] reported that personalized tourniquet pressure in extremity trauma surgery achieved significantly lower applied pressures than uniform protocols while maintaining adequate hemostasis, findings consistent with the present study.

From a mechanistic perspective, lower tourniquet pressures reduce tissue compression while maintaining arterial occlusion, thereby potentially attenuating ischemia-reperfusion injury severity [23, 24]. Wang et al. [25] identified prolonged tourniquet application as an independent risk factor for venous thrombosis following ankle fracture surgery in diabetic patients, emphasizing the clinical relevance of optimizing both pressure and duration. While our study focused on pressure reduction, the LOP-based approach may confer additional benefits through reduced tissue trauma and inflammatory response; however, this remains speculative because such outcomes were not directly measured, and it warrants investigation in future mechanistic studies.

Several practical considerations merit discussion regarding implementation of LOP-based protocols. First, the requirement for preoperative LOP measurement adds approximately 1–3 min to the preparation phase with automated systems, a modest investment that may yield substantial downstream benefits [26, 27]. Second, automated tourniquet systems capable of LOP determination are increasingly available and have been validated across multiple clinical contexts, including pediatric and foot and ankle surgery [14, 27]. Third, nursing education regarding LOP measurement technique and safety margin application is essential to ensure consistent protocol implementation, consistent with current guideline recommendations for individualized tourniquet pressure management [28]. Finally, trauma-specific factors deserve attention: soft tissue swelling, patient positioning, and the urgency of fracture surgery may complicate cuff placement and LOP measurement, and occlusion thresholds may evolve as edema changes during the perioperative period; clinicians should remain alert to these factors when applying LOP-based protocols in fracture patients.

This study has several limitations warranting acknowledgment. First, allocation was not randomized but was based on the attending surgical team and operative scheduling, introducing potential selection bias and team-related confounding; although baseline characteristics were balanced and multivariable adjustment yielded similar estimates, residual confounding by surgeon preference, case complexity, or fracture characteristics cannot be excluded. Second, patient-centered clinical outcomes-including postoperative pain, analgesic consumption, nerve function, skin and wound complications, venous thromboembolism, and functional recovery-were not systematically assessed; the study therefore demonstrates technical feasibility and pressure reduction rather than improved clinical outcomes, and no claim of clinical superiority is justified. Third, hemostatic adequacy was assessed qualitatively without a formal grading scale, and objective measures such as estimated blood loss or transfusion data were not collected. Fourth, tourniquet time, although prespecified as a secondary outcome, was not consistently documented and could not be analyzed; this is an important gap because pressure- and ischemia-related complications depend on both inflation pressure and duration. Fifth, physiological covariates known to influence LOP-including body mass index, limb circumference, and intraoperative blood pressure-were not recorded, precluding correlation and more comprehensive adjusted analyses. Sixth, only patients with complete tourniquet pressure documentation were analyzed, which may introduce documentation-related selection bias. Seventh, the single-center design and the predominance of lower extremity procedures may limit generalizability to other institutional contexts and to upper extremity surgery. Finally, the subgroup analyses were exploratory and were not adjusted for multiple comparisons.

Future research directions include randomized controlled trials comparing LOP-based versus traditional protocols with patient-centered outcomes-including pain scores, analgesic consumption, neurological assessment, wound complications, and functional recovery-as primary endpoints, together with systematic recording of tourniquet time and objective hemostatic measures. Studies examining the correlation between systolic blood pressure and measured LOP, and the influence of fracture-related soft tissue edema on occlusion thresholds, would further refine individualized protocols. Additionally, cost-effectiveness analyses incorporating equipment requirements, operative time, and complication-related costs would inform implementation decisions. Investigation of potential modifications to safety margin algorithms based on fracture characteristics, soft tissue conditions, or anticipated operative complexity may further optimize the individualized approach.

Conclusions

In patients undergoing internal fixation for extremity fractures, LOP-based individualized tourniquet pressure management was feasible and achieved a substantial 31.93% reduction in applied pressure compared with a traditional fixed-pressure protocol, with no documented pressure escalation for inadequate hemostasis. Applied pressure was determined principally by extremity location rather than by patient age or sex. Because patient-centered clinical outcomes were not measured, these findings establish the feasibility and pressure-reducing effect of the LOP-based approach rather than its clinical superiority. Randomized controlled trials incorporating clinical endpoints and tourniquet time are warranted to define the role of individualized tourniquet management in fracture surgery.

Author contributions

JY and PH contributed equally to this work. JY: Conceptualization, Methodology, Data Collection, Writing - Original Draft. PH: Data Collection, Formal Analysis, Writing - Review & Editing. LW: Supervision, Project Administration, Writing - Review & Editing. All authors read and approved the final manuscript.

Funding

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

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was reviewed and approved by the Medical Ethics Committee of Civil Aviation Shanghai Hospital (Approval No.: 2025-01; Approval Date: January 23, 2025). The committee determined that the study protocol conformed to ethical principles. Written informed consent was obtained from all participants prior to enrollment. The study was conducted in accordance with the Declaration of Helsinki.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.