Carbon dioxide elimination during high-frequency jet ventilation for rigid bronchoscopy

A quasi-experimental study of fresh oxygen flow on patients' oxygen reserve during mask-assisted ventilation under general anesthesia induction

Background

To compare the effect of different amounts of fresh oxygen flow on oxygen reserve in patients undergoing general anesthesia.

Methods

Seventy-two patients were enrolled in this quasi-experimental study. Patients were randomly divided into experimental groups with a fresh oxygen flow of 1 L/min, 2 L/min, 4 L/min, and 8 L/min (denoted as G1, G2, G3, and G4, respectively) for 2 min of mask-assisted ventilation. Safe apnea time (SAT) was the primary endpoint; SAT was defined as the time from the cessation of ventilation to the time the patient's pulse oxygen saturation (SpO2) decreased to 90%. Ventilation indicators such as end-tidal oxygen concentration (EtO2), end-tidal carbon dioxide partial pressure (EtCO2), SpO2, and carbon dioxide (CO2) elimination amount, during mask-assisted ventilation, were the secondary endpoints.

Results

The SAT of G1, G2, G3, and G4 were 305.1 ± 97.0 s, 315 ± 112.5 s, 381.3 ± 118.6 s, and 359 ± 104.4 s, respectively (p > 0.05). The EtO2 after 2 min of mask-assisted ventilation in groups G1, G2, G3, and G4 were 69.7 ± 8.8%, 75.2 ± 5.0%, 82.5 ± 3.3%, and 86.8 ± 1.5%, respectively (p < 0.05). Also, there was a moderate positive correlation between the fresh oxygen flow and EtO2 (correlation coefficient r = 0.52, 95% CI 0.31-0.67, p < 0.0001). The CO2 elimination in the G1 and G2 groups was greater than that in the G4 group (p < 0.05). There was no significant difference in other indicators among the groups (all p > 0.05).

Conclusion

The amount of fresh oxygen flow during mask-assisted ventilation was positively correlated with EtO2. Also, even though there was no significant difference, the patients' oxygen reserves increased with the increase in fresh oxygen flow.

Application and Technical Principles of Catheter High-Frequency Jet Ventilation

The aim of this publication is to analyze the topic of high-frequency jet ventilation (HFJV), namely catheter HFJV (C-HFJV), from a mathematical-physical as well as a clinical point of view. There are known issues with applying anesthesia and artificial lung ventilation (ALV) during surgical procedures in the upper airways, e.g., during bronchoscopy or tracheostomy. The principles, advantages, and disadvantages of HFJV are discussed in context with basic physical principles to clarify the proper use of this method. The basic technical principles of catheter construction, as well as its functional properties from a biophysical point of view, are introduced. Also, the placement of the catheter in the airways, the set-up of the HFJV ventilator, and the indications as well as the risks and contraindications of the use of C-HFJV are analyzed. This leads to the explanation of potentially optimal techniques for C-HFJV applications. In this article, we present the positive effects of C-HFJV even with complications such as bacterial or viral pneumonia, including COVID-19. In conclusion, we offer recommendations for clinical practice obtained from a literature review and from our rich clinical experience.

Hypercapnia in COPD Patients Undergoing Endobronchial Ultrasound under Local Anaesthesia and Analgosedation: A Prospective Controlled Study Using Continuous Transcutaneous Capnometry

BACKGROUND

Flexible bronchoscopy (FB) in analgosedation causes alveolar hypoventilation and hypercapnia, the more so if patients suffer from COPD. Nonetheless, neither is capnometry part of standard monitoring nor is there evidence on how long patients should be monitored after sedation.

OBJECTIVES

We investigated the impact of COPD on hypercapnia during FB with endobronchial ultrasound (EBUS) in sedation and how the periprocedural monitoring should be adapted.

METHODS

Two cohorts of consecutive patients - with advanced and without COPD - with the indication for FB with EBUS-guided transbronchial needle aspiration in analgosedation received continuous transcutaneous capnometry (ptcCO2) before, during, and for 60 min after the sedation with midazolam and alfentanil.

MAIN RESULTS

Forty-six patients with advanced COPD and 44 without COPD were included. The mean examination time was 26 ± 9 min. Patients with advanced COPD had a higher peak ptcCO2 (53.7 ± 7.1 vs. 46.8 ± 4.8 mm Hg, p < 0.001) and mean ptcCO2 (49.5 ± 6.8 vs. 44.0 ± 4.4 mm Hg, p < 0.001). Thirty-six percent of all patients reached the maximum hypercapnia after FB in the recovery room (8 ± 11 min). Patients with COPD needed more time to recover to normocapnia (22 ± 24 vs. 7 ± 11 min, p < 0.001). They needed a nasopharyngeal tube more often (28 vs. 11%, p < 0.001). All patients recovered from hypercapnia within 60 min after FB. No intermittent ventilation manoeuvres were needed.

CONCLUSION

A relevant proportion of patients reached their peak-pCO2 after the end of intervention. We recommend using capnometry at least for patients with known COPD. Flexible EBUS in analgosedation can be safely performed in patients with advanced COPD. For patients with advanced COPD, a postprocedural observation time of 60 min was sufficient.

Interventional Pulmonology

Bronchoscopy presents a unique challenge and need for collaboration between anesthesia providers and bronchoscopists. The approach to topical anesthesia, analgesia, and sedation must be customized based on complexity, duration, and setting. The bronchoscopy team must work together in each phase of the procedure to ensure patient safety and allow completion of a quality bronchoscopy. Airway access may change depending on the type of procedure planned and must be discussed before each case. Intraprocedural difficulties with ventilation, airway pressure, and sedation may arise that must be addressed together. This review highlights an approach to these common challenges.

Comparison of double-lung jet ventilation and one-lung ventilation for thoracotomy

BACKGROUND AND OBJECTIVE

Thoracic surgery requires immobilization of the operating area. Usually, this is achieved with one-lung ventilation (OLV), however this may still lead to some movement. High-frequency jet ventilation (HFJV) may be an alternative way of ventilation in thoracic surgery. The purpose of this study was to determine the effectiveness of HFJV as an alternative option to OLV for thoracic procedures.

METHODS

Sixty patients were randomized to receive either HFJV (n = 29) or OLV (n = 31) during the operation. During the course of the study 10 patients were excluded (4 patients in HFJV group and 6 patients in OLV group). The following haemodynamic and ventilatory parameters were recorded: heart rate, systolic and mean blood pressure, ventricular stroke volume, cardiac index, systemic vascular resistance, peak inspiratory pressure, oxygen saturation, PaO2 and PaCO2. Overall parameters were documented before the initiation of the chosen mode of ventilation every 15 min during the operation.

RESULTS

Patients in both groups showed comparable cardiovascular function. Mean values of peak inspiratory pressure were significantly higher in the OLV group. Oxygen saturation values were statistically higher in the HFJV group. PaCO2 values were similar in both during surgery, but were higher in the OLV group after awakening. Mean values of shunt fraction were lower in the HFJV group. Lower values of peak inspiratory pressure were therefore associated with higher partial pressure of carbon dioxide levels in the HFJV group. In the OLV group, 44% of patients experienced a postoperative sore throat. Operating conditions were comparable.

CONCLUSION

HFJV is safe option, comparable to OLV and offers some advantages for open-chest thoracic procedures.

High-frequency jet ventilation in interventional bronchoscopy: factors with predictive value on high-frequency jet ventilation complications

STUDY OBJECTIVE

To evaluate the incidence and impact on clinical outcome of complications observed during high-frequency jet ventilation (HFJV) at interventional bronchoscopy and to identify the perioperative factors that may be associated to an increased incidence of such complications.

DESIGN

Observational retrospective, study with an observational prospective validation of the statistically significant associations.

SETTING

University hospital.

PATIENTS

The retrospective study involved 276 patients who underwent an interventional rigid bronchoscopy during general anesthesia and HFJV. Forty consecutive patients were accrued for the prospective validation group. INTERVENTIONS/MEASUREMENTS: Information recorded included patient medical history and perioperative complications observed at HFJV-managed bronchoscopic procedures and their impact on clinical outcome until hospital discharge.

MAIN RESULTS

At least one complication was detected in 38% of retrospective patients and 55% of prospective patients. Most frequent complications were hypercapnia, hypoxemia, and hemodynamic instability, but just one case of barotrauma in the retrospective group. Despite the high incidence, these complications were transient and did not increase hospital stay, whereas technical failure to widen airway lumen was associated with an adverse prognosis. Several clinical parameters showed a significant association with complications in the univariate analysis. However, the multivariate analysis only evidenced two independent predictive factors: the ASA physical status scale and baseline oxygen saturation.

CONCLUSIONS

Classification in ASA physical status IV group and a baseline oxygen saturation of 95% or less independently predicted the development of complications during interventional rigid bronchoscopy with HFJV.

Superimposed high-frequency jet ventilation (SHFJV) for endoscopic laryngotracheal surgery in more than 1500 patients

BACKGROUND

Superimposed high-frequency jet ventilation (SHFJV), which does not require any tracheal tubes or catheters, was developed specifically for use in laryngotracheal surgery. SHFJV uses two jet streams with different frequencies simultaneously and is applied in the supraglottic space using a jet laryngoscope and jet ventilator.

METHODS

Between 1990 and 2004, SHFJV was studied in 1515 consecutive patients (including 158 children requiring laryngotracheal surgery) prospectively. Ventilation was performed with an air/oxygen mixture and anaesthesia was administered i.v.

RESULTS

Adequate oxygenation and ventilation was achieved in 1512 patients. Arterial blood gas analyses (BGA) were performed between 1990 and 1994; thereafter BGA was only performed in patients with high-grade stenosis of the larynx/trachea or high-risk patients [n=623, mean Pa(O(2)) 133.8 (39.4) mm Hg and mean Pa(CO(2)) 42.3 (10.1) mm Hg]. There were no significant changes in Pa(O(2)) or Pa(CO(2)) during the entire period of SHFJV. No complications secondary to the ventilation technique were observed; in particular, no barotrauma occurred. Three patients required tracheal intubation. SHFJV was also successfully used for laser surgery (n=312). It proved to be a safe mode of ventilation without any complications such as airway fire, major haemorrhage, or aspiration of debris.

CONCLUSION

SHFJV is an advanced ventilation mode playing a pivotal role in the (open) ventilatory support/ventilation of patients with laryngotracheal stenosis. It is particularly indicated in cases of severe stenosis and offers optimal conditions for laryngotracheal surgery, including laser surgery and stent implantation techniques.

Jet ventilation for laryngotracheal surgery in an ex-premature infant

A 4-month-old ex-premature infant with severe airway obstruction from subglottic cysts presented for surgical cyst removal. Laryngeal and tracheal surgical procedures in children may present difficulties for the anesthetist because the airway is shared with the surgeon. We report the use of high-frequency jet ventilation (HFJV) to maintain ventilation and provide adequate surgical access. Anesthesia was induced using sevoflurane in oxygen and was maintained with intravenous infusions of propofol 7.5 mg.kg(-1).h(-1) and remifentanil 0.4 microg.kg(-1).min(-1). The suction channel of the ENT laryngoscope was used to introduce an 8-FG ureteric drainage catheter into the larynx and this catheter was used to provide HFJV. Obstruction to expiratory flow was a major concern and was dependent on good positioning of the rigid laryngoscope. Complications such as barotrauma, pneumopericardium, CO2-retention, necrotizing tracheobronchitis, and gastric rupture dictate a fastidious technique.

Comparison of transcutaneous and endtidal CO2-monitoring for rigid bronchoscopy during high-frequency jet ventilation

OBJECTIVE

To compare endtidal and transcutaneous respiratory monitoring of high-frequency jet ventilation (HFJV) in rigid bronchoscopy. Both techniques provide a noninvasive measurement of pCO2.

METHODS

High-frequency jet ventilation was applied via a rigid bronchoscope. Driving pressure (DP) was initially adapted to ensure normal ventilation. It was then changed twice by +/- 30% from the initial value. Endtidal and transcutaneous data were compared with arterial blood gas monitoring (ABG).

RESULTS

Results were analyzed separately for the time just after changing the driving pressure (10 min) and the remaining time until the next change of the driving pressure (4 min). The first part was called the dynamic phase, and the second part the steady-state phase. Correlation coefficient between endtidal capnography and ABG was 0.96 for the steady state and 0.94 for the dynamic phase, respectively. Bland-Altman analysis revealed a bias of -0.21 kPa with limits of agreement (LOA) 1.63 kPa for the steady state and -0.25 kPa, 2.08 kPa for the dynamic phase, respectively. Correlation coefficient between transcutaneous monitoring and ABG for the steady state phase was 0.83, and was 0.72 for the dynamic phase. Bland-Altman analysis resulted in a bias of -0.89 kPa with LOA - 3.84 kPa during steady state and 0.92 kPa, 4.06 kPa for the dynamic phase, respectively.

CONCLUSION

Endtidal capnography offers accurate respiratory monitoring of HFJV. Transcutaneous monitoring showed a good correlation to ABG only during steady-state conditions. For the dynamic phase the accuracy was significantly lower. Thus, we cannot recommend transcutaneous respiratory monitoring for the specific indication of rigid bronchoscopy using HFJV.

[High frequency jet ventilation in paediatric anaesthesia]

High frequency jet ventilation (HFJV) is an alternative ventilatory mode during anaesthesia for laryngeal microsurgery. This procedure ensures good visualization of the operating field but is not without risk. Thus, its use in paediatric patients requires sound knowledge of respiratory physiology of children and infants. In children up to 8 years, the jet ventilator adjustments must take into account the lower pulmonary compliance and the higher airway resistance (time-constant). In order to avoid barotrauma, which is the main HFJV complication, the jet ventilator has to include a monitoring airway pressure system. The driving pressure and the frequency must be gradually increased while checking thoracic expansion. Total intravenous anaesthesia with profound muscular relaxation using a thin transglottic catheter is the most commonly used technique. Standard monitoring of anaesthesia does not preclude strict clinical supervision so as to detect any pulmonary distension. The air-oxygen mixture must be adjusted to provide the lowest FIO2 possible (< or = 30%) when using the CO2 laser. The main indications for the use of HFJV in paediatric laryngeal microsurgery are laryngomalcia, laryngeal papillomatosis and subglottic haemangioma. HFJV is a reliable and useful technique in airway paediatric surgery providing the operator has good knowledge of the physiological particularities in children.