A retrospective before-after study design was employed. Data were extracted from the electronic medical records and nursing procedure records of the emergency department. All eligible patients who underwent radial artery puncture for arterial blood gas analysis or invasive arterial blood pressure monitoring during the study periods were consecutively enrolled. Each patient was included only once in the analysis to ensure independence of observations. A total of 202 patients treated in January 2024 were enrolled as the pre-intervention group, and 650 patients treated between April and July 2024, following implementation of PDCA-based improvement measures, were assigned to the post-intervention group.

Inclusion criteria:1) age ≥ 18 years; 2) emergency patients requiring radial artery puncture for blood sampling or catheterization; 3) complete clinical and nursing records.

Exclusion criteria:1) severe coagulation dysfunction; 2) infection or trauma at the puncture site; 3) abnormal Allen test indicating inadequate collateral hand circulation; 4) pregnancy or lactation. Radial artery patency was assessed by palpation of the radial pulse and confirmation of arterial waveform on ultrasound prior to the procedure.

There were no statistically significant between-group differences in baseline characteristics, including age, sex, body mass index (BMI), diagnostic category, or puncture site (all P > 0.05), indicating that the two groups were comparable (Table 1).

The pre-intervention group underwent radial artery puncture using the traditional palpation method, performed by nurses based on individual experience without systematic standardized training. The post-intervention group received a combined quality improvement intervention based on the PDCA cycle framework, as described below.

2.2.1. Plan Phase

Current status investigation.All 202 radial artery puncture cases in the department

Table 1. Comparison of baseline characteristics between the two groups.

from January 2024 were reviewed. The first-attempt success rate was only 51.48% (104/202), the overall success rate was 73.44%, and the complication rate was 14.85%—considerably lower than levels reported in the literature for ultrasound-guided puncture [1].

Root cause analysis.Ninety-eight puncture failure cases from the pre-intervention period were consecutively documented and retrospectively analyzed across multiple dimensions, including nurse seniority, patient vascular condition, operating environment, and equipment preparation. The three leading causes of failure were technical issues (33.67%), poor vascular condition (32.65%), and inadequate arm fixation (12.24%). Using fishbone diagram analysis, contributing factors were categorized into four dimensions: personnel, equipment, environment, and patient.

Root cause verification.Identified causes were classified and statistically analyzed using a Pareto chart. According to the 80/20 rule, the top three root causes were identified: vessel displacement due to insufficient arm extension (28.57%), inaccurate localization (20.41%), and weak radial artery pulse in critically ill patients (20.41%). Together, these three factors accounted for 69.39% of failures and were designated as the primary targets of this quality improvement initiative.

Goal setting.Based on baseline values, evidence from the literature [1][4], and the actual conditions of the department, the following improvement goals were established: increase the first-attempt success rate from 51.48% to 74.77%, increase the overall success rate from 73.44% to 86.19%, and reduce the complication rate from 14.85% to 5.94%.

2.2.2. Do Phase

Standardized training.Led by the head nurse, a training team consisting of two senior nurses and one ultrasound physician developed a standardized operating procedure based on the Clinical Practice Standards for Adult Arterial Blood Gas Analysis (Second Edition), as interpreted by Jin et al. [11], adapted to departmental conditions. The training covered radial artery anatomy, indications and contraindications for puncture, the Allen test, equipment preparation, aseptic technique, and post-procedural care. Training combined theoretical lectures, simulation exercises, and bedside teaching, with a total duration of two weeks.

Anatomical knowledge combined with ultrasound-guided positioning training. Specialized training was conducted using the department’s existing ultrasound equipment. Training was not limited to procedural skills; it began with the anatomical course and surrounding structures of the radial artery, then progressed to ultrasound image recognition. In accordance with real-time B-mode ultrasound guidance techniques recommended by the Cochrane systematic review [1], training focused on the short-axis out-of-plane approach and dynamic needle tip positioning (DNTP) [12]-[14]. Nurses first practiced on simulation models, then advanced to bedside operations under supervision.

Senior nurse guidance system.The department established a rapid response mechanism for difficult punctures. When the first puncture attempt failed or high puncture difficulty was anticipated (e.g., in patients with shock and hypotension, agitation and poor cooperation, severe obesity with edema, or cardiopulmonary arrest), the on-duty nurse promptly called a senior nurse to the scene to avoid repeated unsuccessful attempts that would delay rescue. In emergency resuscitation, time is critical; repeated attempts not only increase vascular injury but also waste precious rescue time.

Patient psychological care.Before puncture, the performing nurse briefly explained the purpose, general process, and precautions to the patient to reduce anxiety. Clinically, we observed that greater patient anxiety was associated with a higher probability of radial artery spasm. A study by Deftereos et al. [15] also showed that moderate procedural sedation and analgesia can reduce the incidence of radial artery spasm from 8.3% to 2.6%.

Standardized operating procedure (SOP).A standardized operating procedure for radial artery puncture was developed, comprising five steps: 1) pre-procedural assessment—performing the Allen test to assess collateral hand circulation, palpating the radial artery pulse, and assessing the patient’s consciousness and cooperation level; 2) equipment and position preparation—preparing all required supplies, positioning the patient’s arm in abduction with the wrist dorsiflexed approximately 30˚ on a soft pillow, and performing standard skin disinfection; 3) localization—using ultrasound to identify the radial artery, observe its course and caliber, and mark the puncture point; 4) puncture procedure—using the short-axis out-of-plane approach with real-time ultrasound guidance and DNTP technique; and 5) post-procedural care—appropriate compression hemostasis and fixation.

Post-procedural follow-up.A post-puncture follow-up register was established. The responsible nurse inspected the puncture site at 2 hours and 24 hours after the procedure for hematoma, oozing, infection, upper limb numbness, and other abnormalities. Any abnormal findings were promptly addressed and documented for reporting.

2.2.3. Check Phase

Monthly quality monitoring.Each month, the quality control nurse compiled and analyzed indicators including the first-attempt success rate, overall success rate, and complication rate of radial artery puncture, and plotted trend charts to visually reflect the improvement effect.

Nurse competency assessment.Before and after the intervention, the same 18 participating nurses completed theoretical examinations (full score: 100 points) and practical assessments (full score: 100 points). Comprehensive scores were calculated as 40% theoretical score plus 60% practical score. Pre-post comparisons were performed using paired analysis.

Patient satisfaction survey.A self-designed questionnaire was used to evaluate patients’ subjective experience and satisfaction with the puncture procedure.

2.2.4. Act Phase

A monthly quality analysis meeting was held, at which problems identified during the month were collectively discussed. Effective measures were integrated into the standardized operating procedure and formalized as departmental policies. Unresolved issues were carried forward to the next PDCA cycle for further improvement. For example, during the early implementation phase, we found that some junior nurses had insufficient proficiency in ultrasound image recognition; accordingly, additional ultrasound image recognition workshops were added.

Outcome measures included: 1) first-attempt success rate, defined as the percentage of cases with successful puncture on the first needle insertion; 2) overall success rate, defined as the percentage of ultimately successful puncture cases among all cases; 3) mean number of puncture attempts; 4) complication rate, including hematoma, vasospasm, pseudoaneurysm, local infection, and upper limb numbness, among others; 5) procedure duration, including time to first successful puncture and total procedure time; and 6) nurse theoretical examination and practical assessment scores.

Data were analyzed using SPSS 26.0 statistical software (IBM Corp., Armonk, NY, USA). Normally distributed continuous variables are expressed as mean ± standard deviation ( x ¯ ± s ). Between-group comparisons of patient-level outcomes were performed using the independent-samples t-test. For nurse competency scores measured in the same 18 nurses before and after the intervention, paired-samples t-tests were used to account for the repeated-measures design. Categorical variables are expressed as numbers and percentages, and between-group comparisons were conducted using the chi-square (χ²) test. A two-tailed P-value < 0.05 was considered statistically significant.

No statistically significant between-group differences were found in age, sex, BMI, diagnostic category, or puncture site (all P > 0.05), confirming that the groups were comparable (Table 1).

From April to July 2024, the monthly first-attempt success rate increased progressively: 66.9% in April (107/160), 73.5% in May (119/162), 77.7% in June (129/166), and 84.6% in July (137/162). Among the total of 650 cases, 492 were successful on the first attempt, yielding an overall first-attempt success rate of 75.69%.

Following the intervention, both the first-attempt success rate and the overall success rate were higher than at baseline, and the mean number of puncture attempts was reduced. All differences were statistically significant (P < 0.001) (Table 2).

Table 2. Comparison of puncture outcomes between the two groups.

Thirty patients in the pre-intervention group developed complications, yielding a complication rate of 14.85%; these included 12 cases of hematoma, 8 of vasospasm, 3 of pseudoaneurysm, 4 of local infection, and 3 of upper limb numbness. In the post-intervention group, 36 patients developed complications, for a rate of 5.53% (36/650). All types of complications decreased, with the most pronounced reductions observed for hematoma (from 5.94% to 0.77%) and vasospasm (from 3.96% to 1.23%). The between-group difference in overall complication rate was statistically significant (χ² = 19.64, P < 0.001).

Following the intervention, the time to first successful puncture shortened from 4.8 ± 2.1 min to 3.2 ± 1.3 min, and total procedure duration decreased from 7.6 ± 3.5 min to 4.1 ± 1.8 min. Both differences were statistically significant (P < 0.001).

The theoretical, practical, and comprehensive scores of the 18 participating nurses all improved after the intervention as assessed by paired-samples t-tests (all P < 0.001). Theoretical scores increased from 72.3 ± 9.1 to 89.5 ± 5.4 points, practical scores from 65.8 ± 10.2 to 92.1 ± 3.8 points, and comprehensive scores from 67.1 ± 8.6 to 90.7 ± 4.2 points.

All three key indicators met and exceeded the preset target values (Table 3).

Table 3. Achievement of key quality improvement indicators.

Following implementation of the PDCA-based combined quality improvement intervention, the first-attempt success rate of radial artery puncture in critically ill emergency patients increased from 51.48% to 75.69%, and the overall success rate rose from 73.44% to 95.07%. All three core indicators met and exceeded the preset targets. The magnitude of improvement is consistent with findings of similar studies conducted in China and internationally [1][16], but the more complex clinical profiles of emergency patients and the limited time available for procedures make this improvement particularly notable in the emergency setting.

Monthly data showed that the first-attempt success rate rose gradually from 66.9% in April to 84.6% in July, demonstrating a progressive upward trend consistent with the advancement of training and the gradual improvement of nurses’ technical proficiency—reflecting the continuous improvement characteristic inherent in the PDCA cycle [7]-[10]. By July, the rate of increase had notably slowed and entered a plateau phase, suggesting that further improvement relying solely on the existing training model would be limited. The next quality improvement cycle may need to explore new technical approaches or targeted enhancement programs for high-difficulty cases.

The training model combining anatomical knowledge with ultrasound-guided positioning enabled nurses to correlate ultrasound images with the anatomical course and surrounding structures of the radial artery, establishing a three-dimensional understanding that improves image recognition and needle placement accuracy. Training focused on the short-axis out-of-plane approach and DNTP technique, consistent with recommendations from Cochrane evidence and clinical guidelines [1][11][16]. A recent randomized controlled trial by Mao et al. [14] also demonstrated that the DNTP technique may improve the first-attempt success rate in short-axis ultrasound-guided radial artery cannulation.

To address the root cause of “vessel displacement due to insufficient arm extension”, we specified wrist dorsiflexion positioning and arm fixation methods in the SOP. During puncture, the vessel remains relatively fixed, reducing needle placement deviations caused by vessel movement. An ultrasound study by Xu et al. [17] demonstrated that radial artery spasm and vessel displacement are important anatomical factors in puncture failure, and proper positioning and accurate vessel localization can effectively mitigate their impact.

The advantage of ultrasound guidance is especially pronounced in patients with shock, hypotension, and a non-palpable radial pulse. A review by He et al. [3] noted that patients with shock and hypotension represent a particularly challenging population for radial artery puncture, and ultrasound guidance can significantly improve the puncture success rate in critically ill patients. A randomized controlled trial by Mesa et al. [16] showed that the ultrasound-guided DNTP technique achieved a first-attempt success rate of 97.9%, significantly higher than the conventional long-axis in-plane approach (83.3%).

The complication rate decreased from 14.85% to 5.53%, with reductions observed across all complication types; the most pronounced decreases were for hematoma and vasospasm.

A reduced number of puncture attempts is the primary reason for the decrease in complications. Repeated punctures cause mechanical injury to the vascular wall, which is an important trigger for hematoma and vasospasm. The Cochrane systematic review showed that ultrasound guidance reduces the incidence of severe hematoma by 65% (relative risk = 0.35) [1]; Sandoval et al. [18] also noted in their review that the number of puncture attempts is an important risk factor for radial artery complications.

Implementation of the post-procedural follow-up system provided assurance for complication prevention and control. In their interpretation of the Clinical Practice Standards for Adult Arterial Blood Gas Analysis (Second Edition), Jin et al. [11] pointed out that after arterial blood sampling, the puncture site should be observed for complications such as bleeding and hematoma. The 2-hour and 24-hour follow-up mechanism established in this study is consistent with this standard and facilitates early detection and timely intervention for complications.

After two weeks of systematic training, the theoretical, practical, and comprehensive scores of the 18 participating nurses all improved significantly, with the largest increase observed in practical scores (from 65.8 ± 10.2 to 92.1 ± 3.8 points), as confirmed by paired-samples analysis. This indicates that standardized training and ultrasound technology teaching are effective. A notable outcome of this project was the establishment of a departmental puncture training system—new staff receive basic training, key staff receive advanced ultrasound training, and the senior nurse guidance mechanism ensures technical backup for difficult cases.

The senior nurse guidance system provides technical support for junior nurses, ensuring patient safety while promoting the professional growth of younger staff. Liu et al. [19] reported that standardized nursing coordination helps improve the success rate of ultrasound-guided radial artery puncture and reduces complications, which is consistent with our practical experience.

This study has several limitations. First, it was a single-center study with a limited sample size; therefore, the results should be extrapolated with caution. Second, the before-after study design cannot isolate the individual contributions of each component of the combined intervention—including ultrasound guidance, standardized training, the senior-nurse support system, and the PDCA management framework—from other temporal changes. Third, subgroup comparisons of different puncture techniques (long-axis in-plane versus short-axis out-of-plane) were not performed. Future studies could employ multicenter randomized designs and compare the clinical effectiveness of different ultrasound-guided techniques.