A disorder of consciousness (DOC) refers to a state of altered consciousness resulting from neural system dysfunction or injury that affects arousal and awareness (1). Following the acute coma phase, patients may transition to a prolonged DOC state, encompassing the unresponsive wakefulness state (UWS) and the minimally conscious state (MCS). Tracheostomy is commonly performed in patients with DOC (2), and it has been associated with improved survival rates following severe brain injury (3). However, long-term tracheostomy carries an elevated risk of complications, including the formation of granulation tissue, tracheal stenosis, tracheomalacia, tracheoesophageal fistula, and aspiration (4). Additionally, it is associated with prolonged hospital stays (5), increased infection rates (6), and escalating healthcare costs (7). The presence of tracheostomy may adversely affect the rehabilitation process (8, 9). Therefore, decannulation is a crucial objective during the post-acute stages of rehabilitation (10). Predictors for decannulation include effective cough (8, 11, 12), absence of severe dysphagia (8, 11, 12), Glasgow coma scale (GCS) ≥ 8 (8, 11), higher conscious state according to the Coma Recovery Scale-Revised (CRS-R) (13), younger age (11), and etiology of traumatic brain injury (11). Nevertheless, researchers lack consensus on the predictors for tracheostomy decannulation in patients with DOC (14). The early identification of DOC patients eligible for decannulation is an area that has been largely unexplored until now. To address this research gap, we conducted a study on a substantial cohort of patients with DOC to determine the factors that can predict safe decannulation.

The modified Evans blue dye test (MEBDT) has emerged as a standard clinical tool for evaluating patients with tracheostomy and suspected dysphagia due to its economic, simple, and readily available nature (15). However, the literature provides limited reports on the feasibility and safety of using MEBDT in DOC patients. Thus, a second objective of this study was to assess the feasibility and potential adverse effects of a novel MEBDT method in tracheostomized patients with DOC resulting from diverse etiologies.

A total of 149 DOC patients were consecutively recruited in this study; eight of them were lost at the 12-month follow-up after discharge. The remaining 141 patients were included in the analysis. The average age of the patients was 52.5 ± 16.7 years, and 42 (29.8%) of them were women. The median CRS-R score was 9, with 48.2% of patients having a GCS score of 8 or higher. The median mRS score was 5, and the median FOIS score was 1 at admission. The distribution of diagnoses among the patients was as follows: stroke in 76 cases (53.9%), traumatic brain injury (TBI) in 42 cases (29.8%), hypoxic–ischemic encephalopathy (HIE) in 12 cases (8.5%), and other etiologies in 11 cases (7.8%). Based on repetitive assessments of the CRS-R, the patients were initially classified as UWS in 20.6% of cases and MCS in 79.4% of cases. Among the patients, 73.8% tested positive in the modified Evans blue dye test. Table 1 provides a summary of the clinical and demographic characteristics of the study population.

During and after the modified blue dye test, a total of three patients (2.1%) experienced mild adverse effects. Each patient reported a single mild adverse effect, which included blood-tinged sputum, nausea, and dyspepsia. However, no patients experienced any major adverse effects such as fever or aspiration pneumonia following the MEBDT tests, as confirmed by radiological examinations including pulmonary CT or chest X-ray. The overall mortality rate in the study was 2.1%, with three patients experiencing adverse outcomes. One patient was diagnosed with cardiopulmonary arrest, while the other two patients were diagnosed with multiple organ failure.

The current literature lacks comprehensive information regarding decannulation in patients with prolonged tracheostomy (21). There is no standardized set of clinical parameters to predict the success of decannulation in patients with disorders of consciousness. The conscious state (8) and the improvement of DOC (14, 22) have been identified as crucial factors. However, some studies have reported successful decannulation in patients with a state of UWS (23–25). Interestingly, in these cases, decannulated UWS patients had lower mortality rates compared to those who remained tracheostomized (14). In our study, we observed successful decannulation in four UWS patients out of a total of 29 patients (4.7%). However, the majority of UWS patients did not undergo decannulation during the 12-month follow-up period. In our sample, no significant difference was found in the mortality rate between UWS patients who underwent tracheostomy decannulation and patients with UWS who remained tracheostomized. Two assessment scales for measuring conscious state were used in our study: GCS and CRS-R. The univariate analysis results indicated a strong association between assessments of consciousness (including GCS and CRS-R) and tracheostomy decannulation. However, in multivariate analysis, the conscious state (MCS vs. UWS) according to repetitive CRS-R was found to have a statistically significant relationship with decannulation, while the GCS (GCS ≤ 8 vs. GCS > 8) showed a weak association. This result is likely because the Coma Recovery Scale-Revised (CRS-R) is more sensitive in detecting signs of consciousness compared to the GCS (17). Some authors (18, 26) have reported no significant differences in GCS between the decannulated (D) and non-decannulated (ND) groups. However, there are divergent findings from other authors. They have suggested that a higher GCS is associated with a higher likelihood of decannulation (8, 12, 19, 27). In contrast to GCS, which has shown inconsistent results in different literature, CRS-R has demonstrated a high degree of consistency in predicting decannulation across the literature (13, 19). Therefore, CRS-R appears to be a better predictor of decannulation than GCS for patients with disorders of consciousness.

The previous study (8) suggested that the blue dye test (BDT) was a reliable predictor for decannulation in patients with acquired brain injury (ABI). In our study, a strong association between negative MEBDT results and decannulation was also demonstrated. Furthermore, in the multivariate analysis, the MEBDT results (negative vs. positive) showed a statistically significant relationship with decannulation. Therefore, based on these findings, a negative MEBDT result could be considered as a predictor for decannulation in DOC patients.

One of the objectives of this study was to assess the feasibility and safety of MEBDT in DOC patients. While the use of the blue dye test (BDT) is common in tracheostomized patients with various conditions such as pulmonary disease (28, 29), cardiovascular disease, and nervous system diseases (29, 30), limited research has specifically focused on its application in DOC patients. Previous studies, such as Enrichi’s study (8), employed the original Evans blue dye test method in patients with ABI, while others, such as Hakiki (19), did not specify the method of BDT used. In our clinical practice, we initially utilized Belafsky’s (31) method which involved administering 45 mL of ice chips to three DOC patients. However, we encountered difficulties with swallowing in these individuals. Consequently, we developed a modified approach using 1 mL of thin liquid with two drops of blue food coloring. Both patients in a vegetative state and those in a minimally conscious state exhibited dysfunction in the oral phase of swallowing (32). Recognizing an effective oral phase as a potential indicator of consciousness in DOC diagnosis (33), our modified MEBDT method facilitated swallowing in individuals with impaired consciousness. Importantly, our study demonstrated that the MEBDT was easy and safe to administer in unconscious subjects, thus providing valuable insights into its feasibility in the DOC population.

Retrospective, observational studies have limitations as they rely on data collected in the past and may not have controlled all possible confounding factors. Additionally, single-center studies may have limited generalizability to other populations or settings. Therefore, our findings should be interpreted with caution, and further studies with larger sample sizes and more rigorous study designs are needed to confirm our results.

In conclusion, our study suggests that a higher level of consciousness (MCS) and a negative modified Evans blue dye test (MEBDT) result may serve as potential predictors for successful decannulation in patients with prolonged disorders of consciousness (DOC). These findings highlight the importance of assessing conscious state and swallowing function in determining the feasibility of decannulation in this patient population. However, it is important to acknowledge the limitations of our study, including its retrospective nature and single-center design. Further research with larger, prospective studies is needed to validate these findings and establish more definitive conclusions regarding the predictors of decannulation in prolonged DOC patients.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

The studies involving human participants were reviewed and approved by Human Ethics Committee of Huashan Hospital Fudan University. The patients/participants provided their written informed consent to participate in this study.

RH introduced the blue dye test and designed this study. YC and GA imported the patient data and wrote the article. SF, TW, and LW were in charge of conducting BDT. CC, JW, and GL analyzed the data. All authors contributed to the article and approved the submitted version.

This study was supported in part by grants from the Innovation project of Shanghai Science and Technology on Yangtze River Delta Alliance (no. 20412420200), Shanghai Municipal Key Clinical Specialty (no. shslczdzk02702), and Guiding medical project of Shanghai Science and Technology Committee (Grant no. 19411968700).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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