Abstract
Objectives: To evaluate the clinical relevance of Integrated Pulmonary Index (IPI) monitoring during transbronchial needle aspiration (EBUS-TBNA) under sedation and determine whether it reduces hypoxic events compared to standard monitoring.
Methods: This prospective observational research was carried out at Dr. Lutfi Kirdar City Hospital, Istanbul, Turkey, between July 2022 and July 2023. A total of 50 patients, aged 18-80 years with American Society of Anesthesiologists scores of I-III, undergoing EBUS-TBNA with deep sedation for diagnostic purposes were included. The IPI values were measured at 6 time points: baseline, induction, 3, 5, 10 minutes, and at the end of the procedure. Patients were categorized based on whether their IPI scores were above 7 (group 1) or below 7 (group 2).
Results: A total of 43 patients completed the study. Group 1 had higher end-tidal carbon dioxide and respiratory rate at multiple time points, including induction and at 3, 5, and 10 minutes post-induction (p<0.05). Group 2 experienced a higher rate of apnea at these times (p<0.05). Those with lower IPI scores (namely, IPI=3 and IPI=4) showed significantly higher apnea rates, while those with higher scores (namely, IPI=7 and IPI=8) were less likely to have apneic episodes.
Conclusion: The IPI monitoring during EBUS-TBNA under sedation demonstrated improved detection of apnea episodes and enhanced respiratory safety compared to standard monitoring techniques. Additional research involving more varied populations is necessary to confirm these results.
Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is a minimally invasive bronchoscopic procedure widely used for assessing mediastinal lymph nodes and masses.1,2 However, there is no uniformity in the depth of sedation during EBUS-TBNA, leading to variability in sedation practices and medication choices across different medical centers.3,4 Current sedation guidelines for procedures such as bronchoscopy recommend the standard monitoring of vital signs like heart rate, blood pressure, and partial oxygen saturation (SpO2). Additionally, research has shown that incorporating capnography can help reduce hypoxic events (SpO2<90% for over 15 seconds) and severe hypoxia (SpO2<85%).5,6 Hence, global guidelines suggest that capnography might offer added safety during deep sedation.7
The Integrated Pulmonary Index® (IPI) is an algorithm that provides a combined assessment of 4 parameters: heart rate, respiratory rate, SpO2, and end-tidal carbon dioxide (EtCO2). This index offers a simplified, single-value interpretation of the patient’s respiratory status, facilitating continuous evaluation of ventilation and oxygenation during procedures.8 The IPI score ranges from 1-10, with scores above 7 indicating stable respiratory parameters and those below 7 signaling the need for closer monitoring.
This study aimed to assess the effectiveness of IPI monitoring in patients sedated for EBUS-TBNA and to explore its potential in minimizing hypoxic events compared to traditional monitoring methods.
Methods
This prospective observational research was carried out at Dr. Lutfi Kirdar City Hospital, Istanbul, Turkey, between July 2022 and July 2023. The study included 50 patients of both genders, aged 18-80 years, with the American Society of Anesthesiologists (ASA) scores of I-III, who underwent EBUS-TBNA procedures under diagnostic moderate-to-deep sedation. Patients with significant cardiopulmonary comorbidities (namely, uncontrolled hypertension, chest pain, and advanced heart failure), ASA scores of IV or more, and those younger than 18 or older than 80 years were excluded from the study. Patients who discontinued the procedure, refused sedation, or experienced device malfunction were also excluded.
This study was carried out in line with the principles of the Declaration of Helsinki. Approval was granted by the ethics committee of Dr. Lutfi Kirdar City Hospital, Istanbul, Turkey (June 30, 2022/No: 2022/514/228/22).
After a preoperative anesthesia assessment, values from the monitoring of respiratory rate, IPI, SpO2, heart rate, non-invasive blood pressure, and bispectral index (BIS) were collected. Values automatically recorded by the device were documented at the end of the procedure. Anesthesia induction was initiated with oxygen at 4 L/min, followed by administration of standard doses of anesthetic drugs to achieve moderate-to-deep sedation (midazolam 2 mg, propofol 1 mg/kg, and fentanyl 50 mcg). Intervention was carried out for hypoxic or severe hypoxic events, based on IPI values below 7 and SpO2 evaluation (verbal stimulation and chin lift maneuver). The IPI values were measured at 6 different times: pre-procedure baseline, induction, 3 min after induction, 5 min after induction, 10 min after induction, and at the end of the procedure. For each measurement, group 1 had IPI values above 7 (low risk) and group 2 had IPI values below 7 (high risk).
During the procedure, at baseline and every 5 min thereafter, systolic blood pressure, heart rate, SpO2, EtCO2, IPI, and BIS values were recorded. Additionally, hypoxic (SpO2<90% for >15 sec) and severe hypoxic events (SpO2<85%) occurring during the procedure were documented. Other complications, such as hypotension, bleeding, and aspiration, were also recorded. Sedation depth was assessed using the observer assessment of alertness/sedation scale (OAA/S) and maintained at OAA/S level 3. Anesthesia depth was monitored using BIS, with values maintained between 60-80. An additional propofol dose (0.25 mg/kg) was administered if BIS values exceeded 80. Non-invasive blood pressure, heart rate, SpO2, IPI, respiratory rate, EtCO2, BIS, and OAA/S values were recorded at baseline, one min after induction, 3 min after induction, 5 min after induction, and at the end of the procedure. A modified Aldrete score (MAS) was determined at a post-procedure evaluation, with patients having MAS>9 sent to the post-anesthesia care unit (PACU).
Statistical analysis
The data were analyzed using The Statistical Package for the Social Sciences for Windows, version 29.0 (IBM Corp., Armonk, NY, USA). Descriptive measures such as frequency, percentage, mean, and standard deviation (SD) were computed. Data normality was assessed through the Shapiro-Wilk test. For the group comparisons, Fisher’s exact test and Chi-square tests were employed for categorical variables, and independent sample t-tests and Mann-Whitney-U tests were used for continuous variables. A p-value of <0.05 was considered significant.
Results
A total of 50 EBUS-TBNA patients were included in the study. Four patients were excluded from the study due to intolerance to the procedure (severe hypotension, hypoxia, and more), and 3 patients were excluded due to malfunction of the IPI device during the procedure. Thus, the study concluded with 43 patients. A total of 15 (34.9%) patients were female, and 28 (65.1%) were male. The mean age was 57.30±14.22 years, and the mean weight was 74.05±7.21 kg. Approximately 44.2% of the patients were smokers, and for the smokers, the mean smoking duration was 26.13±13.77 years. The mean procedure time was 19.47±2.74 minutes.
For each of the 6 measurement times, the groups were recreated using the same criteria and compared (Table 1). Group 1 had significantly higher EtCO2 levels and respiratory rates than group 2 at baseline, induction, 3 min, 5 min, and 10 min (p<0.05). Mean arterial pressure (MAP) at induction was significantly elevated in group 1 (p=0.002). In contrast, the groups showed no meaningful differences at the other measured time points (p>0.05). Except for a significant increase in SpO2 in group 1 at 10 min (p=0.006), SpO2 was similar between the groups at all other times (p>0.05). The apnea rate was higher in group 2 at induction, 3 min, 5 min, and 10 min (p<0.05). There were no significant differences between groups in terms of the end-of-procedure EtCO2, MAP, respiratory rate, and SpO2 values (p>0.05). The need for additional anesthesia was higher in group 1 at 3 min (p=0.009), though no significant differences were noted at the other time points (p>0.05).
- Comparison of end-tidal carbon dioxide, respiratory rate, oxygen saturation, additional anesthetic requirement, and apnea rates between groups recorded at 6 different times.
The results of Fisher’s exact test (p<0.001) indicate a statistically significant association between IPI score and the presence of apnea. Individuals with lower IPI scores (namely, IPI=3 and IPI=4) had significantly higher rates of apnea, indicating a negative association between IPI and apnea, while those with higher IPI scores (namely, IPI=7 and IPI=8) were less likely to experience apnea (Figure 1).
- Relationship between Integrated Pulmonary Index (IPI) value and apnea.
Discussion
For all measurements obtained after induction, the EtCO2 values were significantly higher for patients with an IPI score of 7 or higher (group 1) than for those with an IPI score below 7 (group 2). Patients with lower IPI scores had significantly higher rates of apnea episodes compared to those with higher IPI scores.
In a large study involving 760 endoscopy patients across multiple medical centers, a significant decrease in desaturation and hypoxia was observed with the use of capnography (38.9% vs. 53.2%, p<0.001).5 Additionally, a 10-year meta-analysis by Saunders et al9 demonstrated an improvement from respiratory failure to apnea with the inclusion of capnography monitoring during procedural sedation and analgesia. Specifically, the use of capnography was associated with fewer cases of mild to moderate oxygen desaturation.9 In a study by Peveling-Oberhag et al,10 the use of capnography during sedation for percutaneous endoscopic gastrostomy (PEG) insertion was shown to detect the onset of mild and severe hypoxemia an average of 83-99 seconds earlier than standard monitoring. While this time frame may not be a concern for PEG patients, it represents a significant window for obtaining preventive measures for patients who experience rapid hypoxemia, such as pediatric patients or those undergoing EBUS-TBNA. The effect of capnography on respiratory safety has been demonstrated in various studies.11 Our study used IPI score, calculated using 4 parameters crucial in respiratory observation: EtCO2 measured with capnography, heart rate, SpO2, and respiratory rate, alongside capnography-measured EtCO2 to assess respiratory safety.
In a study carried out by Garah et al12 on pediatric patients undergoing endoscopic procedures under sedation, they observed that IPI was more effective than standard monitoring in capturing all apnea and hypoxia episodes. The EBUS-TBNA procedures, similar to pediatric procedures, require quick detection of respiratory compromise, as hypoxic events can rapidly affect respiration. Therefore, early detection of hypoxic events is beneficial in this group.
Kuroe et al13 used IPI to monitor elderly (≥75 years) or obese (body mass index of ≥28) patients in a PACU and at high risk of hypoventilation under general anesthesia. Their findings indicated that a low initial IPI score, along with fluctuations in IPI following admission to the PACU, was predictive of respiratory failure.13 While studies on the use of IPI monitoring in patients at risk of hypoventilation, such as elderly patients, pediatric patients, or obese patients, exist in the literature, studies on the use of IPI monitoring in procedures where hypoxemia is commonly encountered, such as EBUS-TBNA, are very limited.6,13,14 Hypoxemia during EBUS-TBNA is frequently encountered, even in patients without respiratory dysfunction before the procedure. The only study we found in the literature investigating the use of IPI in EBUS-TBNA patients is a retrospective study by Adıgüzel et al,15 where they examined the effects of inhalational and intravenous magnesium use on IPI score and propofol consumption in EBUS-TBNA patients. However, in that study, IPI was used for all patients instead of standard monitoring.
Study limitations
Although the sample size in our study was adequate, expanding the sample may increase the robustness of the findings and improve the statistical power of the analysis. Patients with ASA score I-III were included. This limitation may not reflect the results in patients with higher ASA scores or significant comorbidities. Given these limitations, although our study demonstrates the superiority of IPI monitoring in detecting apnoea episodes and improving respiratory safety, further research in more diverse populations and clinical settings is needed to confirm these findings.
In conclusion, in our study, we compared standard monitoring with IPI monitoring during sedation for EBUS-TBNA, which is known for its rapid effect on respiratory parameters. This study demonstrated the superiority of IPI monitoring over standard monitoring in detecting apnea episodes and ensuring respiratory safety. However, it is important to note that these findings are based on a specific patient population undergoing EBUS-TBNA and may not be generalisable to all patient groups. The IPI monitoring may facilitate early intervention by the physician carrying out and monitoring the procedure in situations where respiration is compromised, but further research is needed to evaluate its effectiveness in different populations.
Acknowledgment
The authors gratefully acknowledge CAN Translation and Editing Services for the English language editing.
Footnotes
Disclosure. Authors have no conflict of interests, and the work was not supported or funded by any drug company.
- Received July 24, 2024.
- Accepted October 17, 2024.
- Copyright: © Saudi Medical Journal
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