Silicone ventilation catheter for high-frequency jet ventilation in interventional pulmonology; a new approach

Abstract

Background/aim

This study evaluated the efficacy of high-frequency jet ventilation (HFJV) using a silicone catheter in patients undergoing rigid bronchoscopy (RB).

Materials and methods

Following necessary approval for a retrospective clinical and experimental study, the data of patients who underwent HFJV using a silicone catheter during RB under general anesthesia through interventional pulmonology (IP) between January 2024 and August 2024 were analyzed. Prior to the study, flow/thermography tests were conducted to assess the efficacy of the silicone catheter. Arterial blood gas (ABG) analysis before, during, and after anesthesia as well as patient hemodynamic and oxygen saturation (SpO₂) data recorded during the procedure were evaluated. Patients were observed for up to 24 h following the procedure. The procedure included the following steps: (1) HFJV application with Evone^® (Ventinova, Eindhoven, Netherlands) ventilator after intubation with an orotracheal silicone catheter; (2) HFJV termination and manual ventilation (MV) application in cases of hypoxia, hypercapnia, and hemodynamic instability; (3) flow-controlled ventilation (FCV) with a laryngeal mask or tracheal intubation in patients who cannot be managed with MV; and (4) close hemodynamic monitoring as well as ABG analysis during the procedure.

Result

A total of 25 patients were included in the study. The median duration of the procedure was 35 min. In 21 (84%) patients, the procedure was successfully performed with HFJV using a silicone ventilation catheter. In these successful cases, the hemodynamic parameters and ABG values remained within normal limits throughout the procedure. The median values of arterial oxygen partial pressure (PaO₂), arterial carbon dioxide partial pressure (PaCO₂), SpO₂, and pH were 210 mmHg, 41.6 mmHg, 99.4%, and 7.37, respectively, when considering the worst ABG values during the procedure. Hypoxia (SpO₂ < 90%) was detected in 4% (n = 1) of patients, while hypercarbia (PaCO₂ ≥ 50 mmHg) was observed in 16% (n = 4). The utilization of a Y-stent was necessary in one patient (4%). One patient (4%) experienced severe bleeding during the resection process, and one (4%) patient underwent orotracheal intubation. Postoperative pulmonary complications or adverse events were not observed in any patient.

Conclusion

The findings of the present study demonstrated that the utilization of silicone catheters in conjunction with HFJV is both safe and efficacious for IP and RB procedures. These results suggest that HFJV with a silicone catheter may be a viable option in RB procedures.

Clinical trial number

It cannot be applicable because it is a retrospective study.

Introduction

Interventional pulmonology (IP) with a rigid bronchoscope (RB) is a prevalent technique for the treatment of airway stenosis [1, 2]. Airway management during RB is one of the greatest challenges for anesthesiologists [3, 4]. Sharing the airway with pulmonologists, unpredictable bleeding during the procedure, and inadequate minute ventilation are common problems that anesthesiologists may encounter in the process [5].

A variety of ventilation strategies are employed during RB, including apneic oxygenation, spontaneous assisted or controlled ventilation, and high-frequency jet ventilation (HFJV) [6]. HFJV involves the application of a high-pressure gas source to an open airway in short bursts through a small-diameter catheter. Despite the proven efficacy of HFJV, complications —such as hypoxemia and hypercapnia— resulting from inadequate gas exchange and barotrauma caused by increased airway pressure may still occur [7].

In HFJV application with an RB, the methods integrated into RB or ventilation catheters (polyurethane, silicone etc.) or even standard aspiration catheters can be used [3]. The application of mechanical HFJV or the type of catheter used depends on the clinician’s choice. Irrespective of the method selected, one of the most significant challenges associated with HFJV is the accumulation of carbon dioxide (CO₂). In our clinical experience, we observed more limited CO₂ retention with silicone catheters than with polyurethane catheters in similar cases. The objective of our study was to test the hypothesis that silicone catheters provide more effective ventilation in HFJV.

Materials and methods

Study design

This retrospective, observational, and descriptive study was initiated following approval from the University of Health Sciences, Ankara Atatürk Sanatorium Training and Research Hospital (approval date: 03/10/2024; approval number: E-53610172-799-255681913). Informed consent was obtained from all patients prior to performing the bronchoscopy.

Catheter tests

Both flow and thermography tests were conducted to evaluate the comparative efficacy of silicone and polyurethane ventilation catheters utilized in routine practice for IP procedures. Tests were conducted on HFJV with the Evone^® (Ventinova, Eindhoven, Netherlands) device. Oscillatory flow and pressure pulses were recorded with the Certifier^® FA Plus (TSI Inc., Shoreview, USA) and a high-flow module. Temperature changes were recorded with the Optris PI400 thermal camera (Optris^® GmbH, Germany). Further, the silicone catheter was modified from a 14 Fr enteral nasogastric feeding catheter (Clinodevice^®, Turkiye). The polyurethane catheter was modified from a 14 Fr nasogastric catheter (Bıçakcılar^®, Turkiye). Both were modified to have a single inlet–outlet and a length of 100 cm. The results and principles of performing the flow and thermography tests are detailed in Supplementary Material 1.

A statistically significant difference was observed in the flow and pressure between the two catheters. The silicone catheter demonstrated a higher airflow with lower pressure (p < 0.001 and p < 0.001, respectively). The thermography test revealed that the polyurethane catheter exhibited cooling in an area with a radius of 124 px, while the silicone catheter demonstrated cooling in an area with a radius of 185 px (Fig. 1).

Fig. 1

Thermography test results

Following the completion of the aforementioned tests, it was determined that the silicone ventilation catheter provided more effective ventilation in HFJV applications than the polyurethane ventilation catheter. Consequently, the silicone ventilation catheter was put into routine use in our clinic.

Patients

The present study included patients aged 18 years and older with central airway stenosis (CAS) who underwent IP procedures utilizing HFJV with silicone catheters between January 2024 and August 2024. The following were the exclusion criteria: asthma or lung bullae, respiratory-transmitted diseases, severe cardiovascular and cerebrovascular disease, plan for stenting in the procedure, and the anticipation of a long processing time.

Anesthesia and ventilation management

In our tertiary center, where a multitude of intensive IP procedures are performed (with 221 procedures conducted between January 2024 and August 2024), a standard perioperative management protocol is employed. Prior to the induction of anesthesia, radial artery cannulation is performed under local anesthesia. Thereafter, standard monitoring and invasive arterial blood pressure are performed. Anesthesia induction is performed with 0.5 µg/kg–0.7 µg/kg remifentanil, 1 mg/kg–2 mg/kg propofol, and 0.7 mg/kg rocuronium, according to protocols established in previous studies and hemodynamic parameters [8, 9]. Following the induction of anesthesia, a silicone ventilation catheter is placed after a three-minute period during which the patient is ventilated via a mask and HFJV is initiated with a driving pressure (DP) of 0.3–0.5 bar. When conditions are optimal, an RB (Carl Reiner GmbH, Austria or Storz, Germany) is inserted orotracheally, lateral to the ventilation catheter. The ventilation catheter is positioned under direct bronchoscopy visualization, with the exact location depending on the lesion in question. The ventilation catheter is positioned in the main bronchus opposite the lesion, or distal to it if the lesion is in the trachea. Anesthesia is maintained according to protocols from previous studies, with propofol infusion at a rate of 6 mg/kg/hour, intravenous administration of 0.5 µg/kg/minute remifentanil and, if necessary, intravenous administration of 0.1 mg/kg rocuronium [4, 8].

The Evone^® ventilator is utilized for the purpose of ventilation. Figure 2 illustrates the device interface and the procedure implementation. A brief video illustration of the procedure is also available in supplementary material 2. The frequency is 80–120 per minute, the inspiratory–expiratory (I: E) ratio is 1:1, and the DP is 0.8–1.2 bar; these values are adjusted with oxygen saturation (SpO₂) and arterial carbon dioxide partial pressure (PaCO₂) during the procedure. Upon completion of the procedure, the HFJV DP is reduced to 0.3–0.4 bar through the administration of 2 mg/kg–4 mg/kg sugammadex. Once adequate spontaneous respiration is achieved, the RB is concluded, the ventilation catheter is removed, and patients are transferred to the postoperative surgical intensive care unit.

Fig. 2

Device interface and procedure implementation

In order to guarantee the safety of the patient, HFJV is terminated if any symptom (e.g., hypoxia, hypercapnia, hemodynamic disturbance) that is deemed unsafe for the patient is identified. As a rescue intervention, MV is initially employed. In the event that the patient’s clinical condition does not improve with this approach, tracheal intubation (utilizing either a Tri-tube^® (Ventinova, Eindhoven, Netherlands) or an appropriate-sized intubation tube) is performed, followed by the implementation of flow control ventilation (FCV) with the Evone^® ventilator device.

Variables and definitions

Demographic data for all participants were recorded. The laboratory parameters and thoracic computed tomography were obtained from the hospital information system. The patient’s hemodynamic data were obtained from the anesthesia follow-up form.

The arterial blood gas (ABG) values obtained before, during, and after the procedure were recorded. In cases where multiple ABG values were recorded during the procedure, the values with the most unfavorable outcomes were selected for analysis. The intra-procedural data were obtained from the IP reports via the hospital information system. Further, the post-procedure bedside chest radiography findings of the patients were recorded. To evaluate the safety of the ventilation mode, any adverse events observed during ventilation and in the initial 24-hour period following the procedure were also recorded.

Hypoxemia was defined as SpO₂ below 90% for at least one minute and/or any arterial oxygen partial pressure (PaO₂) measurement below 60 mmHg [8, 10, 11]. Hypercapnia was defined as an PaCO₂ above 50 mmHg [4, 10, 12]. Hemodynamic instability was defined in the following manner: blood pressure (BP) measurements above 140/90 mmHg and/or mean arterial pressure (MAP) above 110 mmHg throughout the procedure (hypertension), BP below 90/60 mmHg and/or MAP below 60 mmHg (hypotension), and heart rate above 100 beats per minute (bpm) (tachycardia). The persistence of these findings for at least one minute and/or the presence of cardiac arrhythmia while hemodynamic data were normal was considered hemodynamic instability [8]. Laryngeal/bronchospasm was clinically confirmed, while baro/volutrauma was radiologically defined by the presence of a pneumothorax identified through chest radiography.

Statistical analysis

The statistical analysis in this study was conducted using the IBM SPSS Statistics software, version 27.0 (Armonk, NY, USA). Descriptive statistics were expressed as frequencies (n), percentage (%), mean ± standard deviation (SD), or median (minimum value (min), maximum value (max)). Categorical and demographic data were presented as n and %. The data were shared on a patient basis. The distribution of the data obtained in the flow and thermography tests performed before the application was evaluated using the Shapiro–Wilk test. According to the distribution results of the numerical data, comparisons of paired groups were performed using the Student’s t-test or Mann–Whitney U-test.

Results

The data of 25 patients undergoing therapeutic bronchoscopy, for whom the HFJV and the catheter made of silicone material were used for ventilation management of the RB procedure, were analyzed. The median age of the patients was 66 years (min = 26 years, max = 79 years). Four female patients (16%) were included in the study. The median body mass index was 24.6 kg/m² (min = 18.3 kg/m², max = 38.7 kg/m²). The most prevalent comorbidity was hypertension, which was found in 44% of cases. Ten patients (40%) had a pathological diagnosis of cancer before the procedure. A total of 72% of patients (n = 18) exhibited an American Society of Anesthesiologists (ASA) score of 3 (Table 1).

Table 1 Detailed data of included patients

In the RB, 20 patients (80%) underwent mechanical resection, while 4 patients (16%) underwent cryoextraction. Further, three patients (12%) underwent dilatation; in two of them, dilatation alone was sufficient to ensure that the procedure was successful. Stenting was performed in one patient, despite this not being included in the preoperative plan. The median duration of the RB was 35 min (range: 20–105 min). The procedure and lesion data for each patient are presented in Table 1. Furthermore, Supplementary Material 3 includes the bronchoscopy images of all patients recorded during the procedure.

An analysis of the ventilation management of the patients during the procedure revealed that all procedures were performed with HFJV in 21 (84%) patients, while four (16%) patients required alternative ventilation modes (patients 3, 5, 19, and 23). In the initial patient for whom an alternative ventilation mode (patient 3) was required, it was determined that the ventilation catheter be removed and switched to MV due to the decision to implement a Y-stent during the procedure. In the second patient (patient 5), MV was applied because the ventilation catheter could not be advanced to the distal portion of the lesion, which was located in both the trachea and the right and left bronchi. In this patient, it was reported that the bleeding in the post-resection area increased due to the DP effect of HFJV during the procedure, which obstructed the field of view for the bronchoscopy. Further, the RB was prolonged in the third patient (patient 19). This was because although hemodynamic data and ABG values were stable during the procedure, HFJV had to be ceased due to the prolonged HFJV time and the switching of the MV. The final patient who required an alternative ventilation mode (patient 23) was reported to have low SpO₂ (84.8%). Additionally, the distal trachea and both bronchi were almost completely obstructed by the lesion prior to the procedure. During the procedure, there was a deterioration in the hemodynamic parameters and an increase in hypercarbia with MV and HFJV. Consequently, orotracheal intubation with a Tri-tube^® was performed, and FCV was applied.

The ABG values of the patients are presented in Table 2. The median values for PaO₂, PaCO₂, SpO₂, and pH were 210 mmHg, 41.6 mmHg, 99.4%, and 7.37, respectively, when considering the worst blood gas values during the procedure. Furthermore, supplementary material 4 provides a comprehensive account of the ABG values —both patient-based and ventilation management-based— for all patients. Figure 3 illustrates the patient-based ABG PaO₂ values, with one patient (patient 23) (4%) exhibiting a risky value during the procedure. The procedure was performed without incident in this patient, who was intubated orally, ventilated in FCV mode, and subjected to intermittent apnea periods. Figure 3 depicts the patient-based ABG PaCO₂ values; four patients (patients 3, 5, 12, and 23) (16%) exhibited values that were considered risky during the procedure. While the ventilation mode was modified in three of these patients, the PaCO₂ value was found to be decreased in one patient (patient 12) by increasing the frequency of HFJV and prolonging the expiration time. Figure 3 depicts patient-based ABG SpO₂ values. One patient (patient 23) exhibited risky values during the procedure, and the ventilation mode was modified for this patient during the procedure. Additionally, an apnea period was required due to the application of a Y-stent in patient 3, and no desaturation was observed except for that in the apnea period. In patient 23, orotracheal intubation was performed and the ABG values recovered after FCV application.

Table 2 Arterial blood gas value ranges of patients at different time periods

Fig. 3

Arterial oxygen partial pressure (PaO₂), arterial carbon dioxide partial pressure (PaCO₂) and oxygen saturation (SpO₂) values of patients at different time points. *The blood gas values shown in the figure are the worst values seen in a single patient-based measurement.** Hypoxic blood gas value was seen in a single patient (patient number 23) and the patient was promptly intubated with a Tri-tube^®(Ventinova, Eindhoven, Netherlands) and ventilated in flow-controlled ventilation mode and the patient procedure was performed without any problems

The preprocedure and postprocedure chest radiographs of the patients are presented in Supplementary Material 5. No postoperative pulmonary complications or adverse events were identified in any patient.

Discussion

In our institution, IP procedures are conducted with a 14 Fr silicone cannula advanced from the side of the RB. One crucial aspect of this technique is placing the catheter in the distal portion of the stenosis or in the other main bronchus that is not treated in lesions that involve the main bronchus. This may facilitate the expeditious completion of the procedure by minimizing the potential complications associated with ventilation management and the lesion in the airway. The mean procedure time in our study was 35 min, which is relatively brief. In conclusion, when intraoperative ABG and other hemodynamic parameters are evaluated, it is our recommendation that this new technique be used in patients with partial tracheal obstruction or CAS that involves only one main bronchus. It is also important to note that the use of a catheter outside of an RB should be avoided in patients for whom stent application is planned, as it can impede the subsequent placement of the stent. In our stented patient, the HFJV technique was terminated because this decision was made during the procedure.

The application of HFJV in the management of RB was first described by Sanders et al. in 1967 [13]. The majority of catheters referenced in the literature consist of plastic or polyurethane; however, there is no consensus on the optimum catheter type for HFJV [14, 15]. In fact, there are even studies that indicate that 14 F aspiration catheters can also be used for this purpose [16,17,18]. The integration of HFJV with low-frequency jet ventilation (LFJV), also termed the dual jet technique, is referred to as superimposed HFJV (SHFJV). This approach was first introduced by Aloy in 1990 [19]. SHFJV has been demonstrated to maintain adequate oxygenation and CO₂ elimination, thereby reducing related complications [3]. Moreover, there are publications that indicate that SHFJV is superior to conventional HFJV [4, 9]. Currently, both techniques are used in RB applications, and polyurethane ventilation catheters are used during application [20]. Wang et al. [4] compared conventional HFJV (TKR-300B^® HFJV, Jiangxi TELI Anesthesia & Respiration Equipment Co, China; polyurethane ventilation catheter) and SHFJV (Twinstream^® jet ventilator, Carl Reiner GmbH, Austria; polyurethane ventilation catheter) in 66 patients; they found hypercarbia (PaCO₂ ≥ 50 mmHg) in 58.1% (n = 18) of patients in the conventional HFJV group and 31% (n = 9) of patients in the SHFJV group. Fernandez et al. [8] reported hypercarbia (PaCO₂ > 45 mmHg) in 32.5% (n = 13) and hypoxia (SpO₂ < 90%) in 32.5% (n = 13) of patients in their prospective study of 40 patients who underwent HFJV (Ergojet^®-CVT ventilator, Temel, Spain; polyurethane ventilation catheter) in RB patients. Further, Li J et al. [9] conducted a study in which they used SHFJV (Twinstream^® jet ventilator, Carl Reiner GmbH, Austria; polyurethane ventilation catheter) during RB on patients with and without airway stenosis. Their findings revealed a significant increase in CO₂ levels in 30.9% of the group with stenosis and 17.23% of the group without stenosis. These results were based on a study that included 363 patients [9]. A synthesis of the three abovementioned studies reveals heterogeneously distributed outcomes, contingent upon the patient risk group and the procedures performed. In the present study, HFJV (Evone^® ventilator, Ventinova, Eindhoven, Netherlands; silicon ventilation catheter) was utilized in IP procedures, thereby resulting in the detection of hypoxia (SpO₂ < 90%) in 4% (n = 1) and hypercarbia (PaCO₂ ≥ 50 mmHg) in 16% (n = 4) of the patients when the worst ABG values were considered. While our study yielded favorable results in terms of ABG values when compared to the aforementioned studies, the heterogeneous nature of the patient populations in our study and other studies limits our ability to make a definitive evaluation. Furthermore, the experimental results of our study demonstrated that the utilization of silicone catheters in HFJV applications resulted in a higher flow rate, a lower pressure, and a larger gas distribution area. When considering the findings from both the clinical and experimental aspects of this study, it can be concluded that the silicone catheter may possess an optimal structure for HFJV. Nevertheless, the absence of a comparative group hinders the drawing of definitive conclusions.

The combination of the Evone^® device with HFJV and FCV in the treatment of CAS represents a relatively novel approach [21]. In clinical practice, the use of RB in interventions related to CAS and the highly dynamic nature of the process limit the applicability of these two methods [14, 22]. However, in our new technique, the application of HFJV through a catheter outside the RB provided a fast and comfortable intervention process for pulmonologists. Simultaneously, HFJV with the Evone^® device provided effective ventilation at lower DP (0.8–1.2 bar); moreover, in case of a possible distal obstruction, the technical feature of the device prevented complications that could arise by limiting ventilation. Furthermore, no complications were observed during the intraoperative or postoperative periods in our study.

The optimal intraoperative oxygenation strategy remains unclear in the extant literature, particularly in the context of IP procedures and HFJV, where a consensus remains elusive [23, 24]. A randomized trial was conducted to investigate the impact of intraoperative hyperoxemia on postoperative cognitive dysfunction when compared to normoxemia, yielding no statistically significant differences [25]. The literature suggests a minimum PaO₂ of 60 mmHg for RB procedures [8, 10, 11]. In our study, the limit value for intraoperative PaO₂ was accepted as < 60 mmHg. A significant amount of literature supports the use of mild hypocapnia (PaCO₂ = 24 mmHg) [26, 27] and permissive hypercapnia (maximum PaCO₂ 50 mmHg) [12, 28]. In IP procedures, a PaCO₂ value ≥ 50 mmHg is defined as hypercapnia [4]. In our study, the limit values for intraoperative PaCO₂ were established as < 25 mmHg and > 50 mmHg. With respect to SpO₂, the accepted range for low and intermediate targets is 94% and 95%, respectively [23]. However, these specific values are contingent on the surgical procedure and the clinical condition of the patient. Nonetheless, the target SpO₂ for the low group has been documented to be 88–92% [23]. In the context of RB, a value below 90% is widely regarded as the minimum threshold supported by the extant literature [8]. In light of the ABG values and postoperative adverse events observed in our study, it is noteworthy that the novel ventilation strategy employed in IP procedures is effective for managing intraoperative anesthesia. The patient population in our study comprised high-risk patients who necessitated invasive arterial and blood gas monitoring, as per the ASA criteria. However, it should be noted that instantaneous transcutaneous CO₂ (TcCO₂) and transcutaneous O₂ (TcO₂) measurement may be an option for the assessment of CO₂ and O₂ levels in appropriate patients. For this purpose, TcCO₂ and TcO₂ measurement may be considered as an alternative method in the lower-risk patient group undergoing IP. We believe that the implementation of more comprehensive experimental and clinical studies for this purpose will likely facilitate more precise findings.

This study has a few limitations. First, it was conducted at a single center with a relatively small number of cases. Second, the data were analyzed retrospectively. Third, it may not be possible to generalize the findings to the wider population, given that IP procedures are frequently performed in a tertiary care center. Fourth, we would like to point out that we did not perform TcCO₂ and TcO₂ measurement during patient follow-up. However, given the advanced ASA scores of the patient population and the high risk of the procedure, invasive arterial monitoring as well as regular blood gas monitoring, was performed in every patient. Finally, although there are flow and pressure experimental tests with proven devices, further detailed research on the limited CO₂ elevation in silicone tubes may be necessary. In addition, further research is required in the form of randomized controlled trials and experimental airflow imaging using two different material ventilation catheters and different JV devices.

Conclusion

In conclusion, the management of the airway in cases of CAS represents a significant challenge, emphasizing the importance of a dynamic perioperative approach. Although numerous techniques are employed for airway management, the utilization of a catheter in conjunction with an RB for HFJV for this purpose —which we present as a novel technique—minimizes the disruption to the process. Moreover, the results of both clinical and experimental studies, though based on a limited number of cases, have demonstrated that in HFJV with a silicone catheter —despite the high flow rate— the pressure was relatively low and the distribution of the flow was extensive. This may explain the limited CO₂ levels observed with the use of a silicone catheter. Further research, with larger prospective studies, is required in this regard.