High-Frequency Jet Ventilation Versus Spontaneous Respiration for Percutaneous Cryoablation of Lung Tumors: Comparison of Adverse Events and Procedural Efficiency.

BACKGROUND. High-frequency jet ventilation (HFJV) facilitates accurate probe placement in percutaneous ablation of lung tumors but may increase risk for adverse events, including systemic air embolism. OBJECTIVE. The purpose of this study was to compare major adverse events and procedural efficiency of percutaneous lung ablation with HFJV under general anesthesia to spontaneous respiration (SR) under moderate sedation. METHODS. This retrospective study included consecutive adults who underwent CT-guided percutaneous cryoablation of one or more lung tumors with HFJV or SR between January 1, 2017, and May 31, 2023. We compared major adverse events (Common Terminology Criteria for Adverse Events grade ≥ 3) within 30 days postprocedure and hospital length of stay (HLOS) of 2 days or more using logistic regression analysis. We compared procedure time, room time, CT guidance acquisition time, CT guidance radiation dose, total radiation dose, and pneumothorax using generalized estimating equations. RESULTS. Overall, 139 patients (85 women, 54 men; median age, 68 years) with 310 lung tumors (82% metastases) underwent 208 cryoablations (HFJV, n = 129; SR, n = 79). HFJV showed greater rates than SR for the treatment of multiple tumors per session (43% vs 19%, respectively; p = .02) and tumors in a nonperipheral location (48% vs 24%, p < .001). Major adverse event rate was 8% for HFJV and 5% for SR (p = .46). No systemic air embolism occurred. HLOS was 2 days or more in 17% of sessions and did not differ significantly between HFJV and SR (p = .64), including after adjusting for probe number per session, chronic obstructive pulmonary disease, and operator experience (p = .53). Ventilation modalities showed no significant difference in procedure time, CT guidance acquisition time, CT guidance radiation dose, or total radiation dose (all p > .05). Room time was longer for HFJV than SR (median, 154 vs 127 minutes, p < .001). For HFJV, the median anesthesia time was 136 minutes. Ventilation modalities did not differ in the frequencies of pneumothorax or pneumothorax requiring chest tube placement (both p > .05). CONCLUSION. HFJV appears to be as safe as SR but had longer room times. HFJV can be used in complex cases without significantly impacting HLOS of 2 days or more, procedure time, or radiation exposure. CLINICAL IMPACT. Selection of the ventilation modality during percutaneous lung ablation should be based on patient characteristics and anticipated procedural requirements as well as operator preference.

[Bacterial load of the surroundings during rigid diagnostic bronchoscopy under high frequency jet-ventilation]. / Mikrobielle Belastung der Umgebung während der Anwendung der Hochfrequenz-Jetventilation in der Bronchoskopie.

BACKGROUND: High-frequency jet ventilation (HFJV) is used in pneumological endoscopy for rigid, diagnostic, and therapeutic bronchoscopies. It is unclear to what extent the unobstructed flow of respiratory gas from the patient's lungs causes microbial contamination of the surrounding air. MATERIAL AND METHODS: After the start of the HFJV (15 min) in 16 rigid bronchoscopies, airborne pathogen measurements were taken directly at the distal endoscope outlet, at examiner height (40 cm above the endoscope outlet), at a 2 m distance from the endoscope in the room and at the supply air outlet of the examination room using an RCS air sampler. The number and type of pathogens isolated in the air samples were then determined, as well as germs in the bronchoalveolar lavage fluid (BALF) from the patient's lungs. RESULTS: An increased bacterial density (136 and 114 CFU/m3) was detected directly at the distal end of the endoscope and at examiner height at a distance of 40 cm, which decreased significantly with increasing distance from the bronchoscope (98 CFU/m3 at a distance of 2 m and 82 CFU/m3 at the supply air outlet). The most frequently detected bacteria were Staphylococcus spp., Micrococcus spp. and Bacillus spp. In the BALF, pathogens could only be cultivated in four of 16 samples, but the same pathogens were detected in the BALF and the ambient air. CONCLUSION: When performing a rigid bronchoscopy, in which patients are mechanically ventilated in a controlled manner using an open HFJV system, there is an increased pathogen load in the ambient air and therefore a potential risk for the examiner.

Evaluation of the impact of deep neuromuscular blockade on surgical conditions for laryngeal microsurgery with High Frequency Jet Ventilation. A comparison with no block during intravenous general anesthesia with topical lidocaine.

OBJECTIVE: Laryngeal transoral surgery classically requires a neuromuscular block (NMB) to facilitate tracheal intubation and to improve surgical conditions. However, the short duration of most procedures and the potential complications of residual NMB lead to consider a no block approach. The hypothesis that intravenous anesthesia (remifentanil and propofol infusions) without NMB but including glottis topical lidocaine anesthesia would allow clinically acceptable laryngeal exposure and good surgical conditions was tested in the specific context of procedures undergone with High Frequency Jet Ventilation (HFJV). STUDY DESIGN: A prospective randomized clinical comparison. METHODS: 66 consenting patients were planned to receive 0.6 mg·kg-1 rocuronium or saline at random. The outcome measurements included the time and conditions to complete suspended laryngoscopy, and the surgical conditions rated by the surgeon. Any vocal cord movement or coughing was recorded. Data were compared using a Wilcoxon rank-sum test for numerical variables and chi-square test for categorical ones. Treatment failure was defined as an impossible laryngoscopy or a grade 4 surgical field occurring at any time during surgery and was compared to its null theoretical value by a general z-test. An interim analysis after completion of 50% patients was performed using Pocock boundaries at 0.0294 significance levels. RESULTS: A significant failure rate occurred in the non paralysed group (27%, p < 0.001). No coughing and no vocal cords movement occurred in the NMB group. Poorer surgical conditions were obtained without NMB (p = 0.011). CONCLUSION: Inducing a deep NMB ensured improved conditions during direct laryngeal microsurgery with HFJV.

High frequency jet ventilation through mask contributes to oxygen therapy among patients undergoing bronchoscopic intervention under deep sedation.

BACKGROUND: High frequency jet ventilation (HFJV) is an open ventilating technique to maintain ventilation for emergency or difficult airway. However, whether jet ventilation or conventional oxygen therapy (COT) is more effective and safe in maintaining adequate oxygenation, is unclear among patients with airway stenosis during bronchoscopic intervention (BI) under deep sedation. METHODS: A prospective randomized cohort study was conducted to compare COT (high flow oxygen) with normal frequency jet ventilation (NFJV) and HFJV in oxygen supplementation during BI under deep sedation from March 2020 to August 2020. Patients receiving BI under deep sedation were randomly divided into 3 parallel groups of 50 patients each: the COT group (fractional inspired oxygen (FiO2) of 1.0, 12 L/min), the NFJV group (FiO2 of 1.0, driving pressure of 0.1 MPa, and respiratory rate (RR) 15 bpm) and the HFJV Group (FiO2 of 1.0, driving pressure of 0.1 MPa, and RR of 1200 bpm). Pulse oxygen saturation (SpO2), mean arterial blood pressure and heart rate were recorded during the whole procedure. Arterial blood gas was examined and recorded 15 min after the procedure was initiated. The procedure duration, dose of anesthetics, and adverse events during BI in the three groups were also recorded. RESULTS: A total of 161 patients were enrolled, with 11 patients excluded. The clinical characteristics were similar among the three groups. PaO2 of the COT and NFJV groups was significantly lower than that of the HFJV group (P < 0.001). PaO2 was significantly correlated with ventilation mode (P < 0.001), body mass index (BMI) (P = 0.019) and procedure duration (P = 0.001). Multiple linear regression showed that only BMI and procedure duration were independent influencing factors of arterial blood gas PaO2 (P = 0.040 and P = 0.002, respectively). The location of airway lesions and the severity of airway stenosis were not statistically correlated with PaCO2 and PaO2. CONCLUSIONS: HFJV could effectively and safely improve intra-operative PaO2 among patients with airway stenosis during BI in deep sedation, and it did not increase the intra-operative PaCO2 and the risk of hypercapnia. PaO2 was correlated with ventilation mode, BMI and procedure duration. Only BMI and procedure duration were independent influencing factors of arterial blood gas PaO2. PaCO2 was not correlated with any preoperative factor. TRIAL REGISTRATION: Chinese Clinical Trial Registry. Registration number, ChiCTR2000031110 , registered on March 22, 2020.

Stereotactic image-guided microwave ablation of hepatocellular carcinoma using a computer-assisted navigation system.

BACKGROUND & AIMS: Ablation plays an important role in the treatment of hepatocellular carcinoma. Because image-guided navigation technology has recently entered the clinical setting, we aimed to analyse its safety, therapeutic and procedural efficiency. METHODS: Retrospective analysis of patients treated with stereotactic image-guided microwave ablation (SMWA) between January 2015 and December 2017. Interventions were performed using computertomography-guidance with needle trajectory, ablation planning and automatic single-marker patient registration. Needle placement and ablation coverage was controlled by image fusion under general anaesthesia with jet-ventilation. RESULTS: In total 174 ablations were performed in 88 patients during 119 interventions. Mean age was 66 (46-84) years, 74 (84.1%) were men and 74% were Child Pugh Class A. Median tumour size was 16 (4-45) mm, 62.2% were BCLC A. Median lateral and longitudinal error of needle placement were 3.2 (0.2-14.1) and 1.6 (0-15.8) mm. Median one tumour (1-4) was ablated per session. One patient developed a Dindo IIIb (0.8%) complication, six minor complications. After re-ablation of 12 lesions, an efficacy rate of 96.3% was achieved. Local tumour progression was 6.3% (11/174). Close proximity to major vessels was significantly correlated with local tumour progression (P < .05). Median overall follow-up was 17.5 months after intervention and 24 months after initial diagnosis. BCLC stage, child class and previous treatment were significantly correlated with overall survival (P < .05). CONCLUSION: Stereotactic image-guided microwave ablation is a safe and efficient treatment for HCC offering a curative treatment approach in general and in particular for lesions not detectable on conventional imaging or untreatable because of difficult anatomic locations.

Electromagnetic navigation system combined with High-Frequency-Jet-Ventilation for CT-guided hepatic ablation of small US-Undetectable and difficult to access lesions.

Objectives: To report the feasibility and efficacy of percutaneous ablation of small hepatic malignant tumors that are invisible on ultrasound and inaccessible using in-plane CT guidance, using a combination of high-frequency jet-ventilation (HFJV) and electromagnetic (EM) needle tracking. Methods: This study reviewed 27 percutaneous ablations of small hepatic tumors (<2 cm) performed using EM navigation-based probe placement and HFJV. All lesions were invisible on ultrasound and difficult to reach on CT requiring a double-oblique approach. The primary outcome was technical efficacy, defined as complete lesion coverage, and evaluated on contrast enhanced MRI after 3 and 6 months. Needle placement accuracy, the number of control CT acquisitions, procedure time, complications and radiation doses were assessed. Results: Twenty-one patients with 27 treated lesions (14 hepatocellular carcinomas and 13 metastases) were included in this study. Mean tumor size was 12 ± 5.7 mm. Thirty-three percent of the lesions were located on the hepatic dome. Complete ablation was obtained in 100% at the 3- and 6-month MRI follow-up. The ablation probe was correctly placed on the first pass in 96%, with a mean path-to-tumor angle of 7 ± 4 degrees and a mean tip-to-tumor distance of 22 ± 19mm. A readjustment for additional overlapping application resulted in complete treatment in 4 patients. Needle placement took a mean 23 ± 12 min with mean radiation doses of 558 mGy*cm. No major complications were reported. Conclusion: Percutaneous liver ablation of lesions that cannot be seen on US and requiring out-of-plane CT access can be successfully and safely treated using electromagnetic-based navigation and jet-ventilation.

Supraglottic jet oxygenation and ventilation for obese patients under intravenous anesthesia during hysteroscopy: a randomized controlled clinical trial.

BACKGROUND: Supraglottic jet oxygenation and ventilation (SJOV) can effectively maintain adequate oxygenation in patients with respiratory depression, even in apnea patients. However, there have been no randomized controlled clinical trials of SJOV in obese patients. This study investigated the efficacy and safety of SJOV using WEI Nasal Jet tube (WNJ) for obese patients who underwent hysteroscopy under intravenous anesthesia without endotracheal intubation. METHODS: A single-center, prospective, randomized controlled study was conducted. The obese patients receiving hysteroscopy under intravenous anesthesia were randomly divided into three groups: Control group maintaining oxygen supply via face masks (100% oxygen, flow at 6 L/min), the WNJ Oxygen Group with WNJ (100% oxygen, flow: 6 L/min) and the WNJ SJOV Group with SJOV via WNJ [Jet ventilator working parameters:100% oxygen supply, driving pressure (DP) 0.1 MPa, respiratory rate; (RR): 15 bpm, I/E; ratio 1:1.5]. SpO2, PETCO2, BP, HR, ECG and BIS were continuously monitored during anesthesia. Two-Diameter Method was deployed to measure cross sectional area of the gastric antrum (CSA-GA) by ultrasound before and after SJOV in the WNJ SJOV Group. Episodes of SpO2 less than 95%, PETCO2 less than 10 mmHg, depth of WNJ placement and measured CSA-GA before and after jet ventilation in the WNJ SJOV Group during the operation were recorded. The other adverse events were collected as well. RESULTS: A total of 102 patients were enrolled, with two patients excluded. Demographic characteristics were similar among the three groups. Compared with the Control Group, the incidence of PETCO2 < 10 mmHg, SpO2 < 95% in the WNJ SJOV group dropped from 36 to 9% (P = 0.009),from 33 to 6% (P = 0.006) respectively,and the application rate of jaw-lift decreased from 33 to 3% (P = 0.001), and the total percentage of adverse events decreased from 36 to 12% (P = 0.004). Compared with the WNJ Oxygen Group, the use of SJOV via WNJ significantly decreased episodes of SpO2 < 95% from 27 to 6% (P = 0.023), PETCO2 < 10 mmHg from 33 to 9% (P = 0.017), respectively. Depth of WNJ placement was about 12.34 cm in WNJ SJOV Group. There was no significantly difference of CSA-GA before and after SJOV in the WNJ SJOV Group (P = 0.234). There were no obvious cases of nasal bleeding in all the three groups. CONCLUSIONS: SJOV can effectively and safely maintain adequate oxygenation in obese patients under intravenous anesthesia without intubation during hysteroscopy. This efficient oxygenation may be mainly attributed to supplies of high concentration oxygenation to the supraglottic area, and the high pressure jet pulse providing effective ventilation. Although the nasal airway tube supporting collapsed airway by WNJ also plays a role. SJOV doesn't seem to increase gastric distension and the risk of aspiration. SJOV can improve the safety of surgery by reducing the incidence of the intraoperative involuntary limbs swing, hip twist and cough. TRIAL REGISTRATION: Chinese Clinical Trial Registry. Registration number, ChiCTR1800017028, registered on July 9, 2018.

Assessment of changes of regional ventilation distribution in the lung tissue depending on the driving pressure applied during high frequency jet ventilation.

BACKGROUND: Electrical impedance tomography (EIT) is a tool to monitor regional ventilation distribution in patient's lungs under general anesthesia. The objective of this study was to assess the regional ventilation distribution using different driving pressures (DP) during high frequency jet ventilation (HFJV). METHODS: Prospective, observational, cross-over study. Patients undergoing rigid bronchoscopy were ventilated HFJV with DP 1.5 and 2.5 atm. Hemodynamic and ventilation parameters, as well as ventilation in different regions of the lungs in percentage of total ventilation, assessed by EIT, were recorded. RESULTS: Thirty-six patients scheduled for elective rigid bronchoscopy. The final analysis included thirty patients. There was no significant difference in systolic, diastolic and mean arterial blood pressure, heart rate, and peripheral saturation between the two groups. Peak inspiratory pressure, mean inspiratory pressure, tidal volume, and minute volume significantly increased in the second, compared to the first intervention group. Furthermore, there were no statistically significant differences between each time profiles in all ROI regions in EIT. CONCLUSIONS: In our study intraoperative EIT was an effective method of functional monitoring of the lungs during HFJV for rigid bronchoscopy procedure. Lower driving pressure was as effective in providing sufficient ventilation distribution through the lungs as the higher driving pressure but characterized by lower airway pressure. TRIAL REGISTRATION: The study was registered on ClinicalTrials.gov under no. NCT02997072 .

Stereotactic CT-Guided Percutaneous Microwave Ablation of Liver Tumors With the Use of High-Frequency Jet Ventilation: An Accuracy and Procedural Safety Study.

OBJECTIVE: The purpose of the present study is to evaluate the accuracy and safety of antenna placement performed with the use of a CT-guided stereotactic navigation system for percutaneous ablation of liver tumors and to assess the safety of high-frequency jet ventilation for target motion control. MATERIALS AND METHODS: Twenty consecutive patients with malignant liver lesions for which surgical resection was contraindicated or that were not readily visible on ultrasound or not accessible by ultrasound guidance were included in the study. Patients were treated with percutaneous microwave ablation performed using a CT-guided stereotactic navigation system. High-frequency jet ventilation was used to reduce liver motion during all interventions. The accuracy of antenna placement, the number of needle readjustments required, overall safety, and the radiation doses were assessed. RESULTS: Microwave ablation was completed for 20 patients (28 lesions). Performance data could be evaluated for 17 patients with 25 lesions (mean [± SD] lesion diameter, 14.9 ± 5.9 mm; mean lesion location depth, 87.5 ± 27.3 mm). The antennae were placed with a mean lateral error of 4.0 ± 2.5 mm, a depth error of 3.4 ± 3.2 mm, and a total error of 5.8 ± 3.2 mm in relation to the intended target. The median number of antenna readjustments required was zero (range, 0-1 adjustment). No major complications were related to either the procedure or the use of high-frequency jet ventilation. The mean total patient radiation dose was 957.5 ± 556.5 mGy × cm, but medical personnel were not exposed to irradiation. CONCLUSION: Percutaneous microwave ablation performed with CT-guided stereotactic navigation provides sufficient accuracy and requires almost no repositioning of the needle. Therefore, it is technically feasible and applicable for safe treatments.

Supraglottic jet oxygenation and ventilation enhances oxygenation during upper gastrointestinal endoscopy in patients sedated with propofol: a randomized multicentre clinical trial.

BACKGROUND: Hypoventilation is the main reason for hypoxia during upper gastrointestinal endoscopy procedures with sedation. The key to preventing hypoxia is to maintain normal ventilation during the procedure. We introduced supraglottic jet oxygenation and ventilation (SJOV) through a new Wei nasal jet tube (WNJ) to reduce the incidence of hypoxia in patients sedated with propofol during upper gastrointestinal endoscopy procedures. METHODS: In a multicentre, prospective randomized single-blinded study, 1781 outpatients undergoing routine upper gastrointestinal endoscopy who were sedated with propofol by an anaesthetist were randomized into the following three groups: the supplementary oxygen via nasal cannula group [nasal cannula oxygen: O 2 (2 litres min -1 ) was administered via a nasal cannula]; the supplementary oxygen via WNJ group [WNJ oxygen: O 2 (2 litres min -1 ) was administered through a WNJ]; and the SJOV via WNJ group (WNJ SJOV: SJOV was administered via WNJ) at three centres from March 2015 to July 2016. The primary outcome of interest was the incidence of hypoxia (peripheral oxygen saturation of 75-89%). Other adverse events were also recorded. RESULTS: Supraglottic jet oxygenation and ventilation decreased the incidence of hypoxia from 9 to 3% ( P <0.0001). No severe hypoxia occurred in the WNJ SJOV group, one instance occurred in the WNJ oxygen group, and two instances were observed in the nasal cannula oxygen supply control group. Supraglottic jet oxygenation and ventilation-related minor adverse events increased significantly within 1 min after the procedure but decreased 30 min later. CONCLUSIONS: The use of SJOV during upper gastrointestinal endoscopy for patients who are sedated with propofol reduces the incidence of hypoxia, with minor and tolerable adverse events. Supraglottic jet oxygenation and ventilation has a favourable risk-to-benefit ratio and may improve patient safety. CLINICAL TRIAL REGISTRATION: NCT02436018.

High frequency jet ventilation for motion management during ablation procedures, a narrative review.

BACKGROUND: High frequency jet ventilation (HFJV) is a method of ventilation that has gained renewed interest over the recent years as it can reduce organ movement to near static conditions, thus enhancing surgical precision in minimal invasive procedures, for example, ablation procedures for atrial fibrillation and solid organ tumours. The aim of this review was to create a summary of the current evidence concerning the clinical use of HFJV for ablative procedures. METHOD: PubMed was searched for the key words high frequency ventilation and ablation January 1990-December 2016. RESULT: The search initially identified 34 papers, 14 met the inclusion criteria. Articles in other languages than English (n = 1), comments regarding other articles (n = 4) and articles that did not include HFJV or ablative procedures (n = 15) were excluded. Two articles were added from references in papers included from the primary search. Sixteen studies were finally included in the review; four updates/reviews and 12 papers with results from studies of HFJV on humans, with a total of 889 patients; 498 patients ventilated with HFJV and 391 controls. There were no randomised studies. The overall scientific quality of the studies was low. CONCLUSION: There is a lack of well-designed studies evaluating HFJV during ablation procedures. The available information, while sparse, supports the effect of less tissue movement, resulting in better surgical precision and outcome; such as shorter procedural time, fewer shock waves (ESWL) and less recurrence of atrial fibrillation. Randomised controlled studies are needed in this promising area of research to prove its superiority to standard ventilation.

Transtracheal jet ventilation in the 'can't intubate can't oxygenate' emergency: a systematic review.

BACKGROUND: Transtracheal jet ventilation (TTJV) is recommended in several airway guidelines as a potentially life-saving procedure during the 'Can't Intubate Can't Oxygenate' (CICO) emergency. Some studies have questioned its effectiveness. METHODS: Our goal was to determine the complication rates of TTJV in the CICO emergency compared with the emergency setting where CICO is not described (non-CICO emergency) or elective surgical setting. Several databases of published and unpublished literature were searched systematically for studies describing TTJV in human subjects. Complications were categorized as device failure, barotrauma (including subcutaneous emphysema), and miscellaneous. Device failure was defined by the inability to place and/or use the TTJV device, not patient survival. RESULTS: Forty-four studies (428 procedures) met the inclusion criteria. Four studies included both emergency and elective procedures. Thirty studies described 132 emergency TTJV procedures; 90 were CICO emergencies. Eighteen studies described 296 elective TTJV procedures. Device failure occurred in 42% of CICO emergency vs 0% of non-CICO emergency (P<0.001) and 0.3% of elective procedures (P<0.001). Barotrauma occurred in 32% of CICO emergency vs 7% of non-CICO emergency (P<0.001) and 8% of elective procedures (P<0.001). The total number of procedures with any complication was 51% of CICO emergency vs 7% of non-CICO emergency (P<0.001) and 8% of elective procedures (P<0.001). Several reports described TTJV-related subcutaneous emphysema hampering subsequent attempts at surgical airway or tracheal intubation. CONCLUSIONS: TTJV is associated with a high risk of device failure and barotrauma in the CICO emergency. Guidelines and recommendations supporting the use of TTJV in CICO should be reconsidered.

[Sufficient high frequency jet ventilation during a period of 2.5 h - Airway management during resection of a tracheaesophageal fistula and tracheal resection]. / Kasuistik: Suffiziente High-Frequency-Jet-Ventilation über 2,5 h.

We present a 54 year old female patient who had undergone a Ross procedure in 2009, and in 2013 again a replacement of the aortic root and arch with bioprothetic material and homograft replacement of the pulmonalis walve. Postoperatively the patient had experienced a functional compromising tracheal stenosis and a persistent esophago-tracheal fistula. Endoscopic attempts to close the fistula were not successful, and the fistula was "bridged" with an endoscopically positioned tracheal stent.We report the anaesthesiological management during the open surgical repair of the esophago-tracheal fistula and resection of 2 tracheal rings with high frequency jet ventilation over a period of 2.5 h. The Patient was discharged from hospital on the 17. postoperative day.

Influence of Tracheal Obstruction on the Efficacy of Superimposed High-frequency Jet Ventilation and Single-frequency Jet Ventilation.

BACKGROUND: Both superimposed high-frequency jet ventilation (SHFJV) and single-frequency (high-frequency) jet ventilation (HFJV) have been used with success for airway surgery, but SHFJV has been found to provide higher lung volumes and better gas exchange than HFJV in unobstructed airways. The authors systematically compared the ventilation efficacy of SHFJV and HFJV at different ventilation frequencies in a model of tracheal obstruction and describe the frequency and obstruction dependence of SHFJV efficacy. METHODS: Ten anesthetized animals (weight 25 to 31.5 kg) were alternately ventilated with SHFJV and HFJV at a set of different fHF from 50 to 600 min. Obstruction was created by insertion of interchangeable stents with ID 2 to 8 mm into the trachea. Chest wall volume was measured using optoelectronic plethysmography, airway pressures were recorded, and blood gases were analyzed repeatedly. RESULTS: SHFJV provided greater than 1.6 times higher end-expiratory chest wall volume than HFJV, and tidal volume (VT) was always greater than 200 ml with SHFJV. Increase of fHF from 50 to 600 min during HFJV resulted in a more than 30-fold VT decrease from 112 ml (97 to 130 ml) to negligible values and resulted in severe hypoxia and hypercapnia. During SHFJV, stent ID reduction from 8 to 2 mm increased end-expiratory chest wall volume by up to 3 times from approximately 100 to 300 ml and decreased VT by up to 4.2 times from approximately 470 to 110 ml. Oxygenation and ventilation were acceptable for 4 mm ID or more, but hypercapnia occurred with the 2 mm stent. CONCLUSION: In this in vivo porcine model of variable severe tracheal stenosis, SHFJV effectively increased lung volumes and maintained gas exchange and may be advantageous in severe airway obstruction.

[Anesthesia in interventional pulmonology -- bronchoscopy and jet ventilation]. / Anästhesie in der interventionellen Pneumologie--Bronchoskopie und Jet-Ventilation.

Today interventional procedures are frequently used for diagnosis and treatment in patients with various pulmonary diseases. Besides bronchoscopy in local- or general anesthesia jet-ventilation is commonly applied via catheter or rigid bronchoscope. Anesthesiologists should have profound knowledge of high-frequency ventilation and possible complications when assisting during interventional procedures.

Flow dynamics using high-frequency jet ventilation in a model of bronchopleural fistula.

BACKGROUND: Positive pressure ventilation in patients with a bronchopleural fistula (BPF) is associated with variable, unpredictable gas leaks that can impair gas exchange. The optimum settings for high-frequency jet ventilation in this scenario are unclear. We investigated flow dynamics with BPFs of 2 and 10 mm, at various positions and with different jet ventilator settings in a bench-top model. METHODS: A 2 or 10 mm length fistula was created at proximal, middle, or distal sites in standard artificial ventilator 'test' lungs and cadaveric porcine lungs. The effects of alterations in frequency, applied pressure, and on entrained, expired, and leak volumes were determined using gauge and differential pressure sensors. RESULTS: Entrained, delivered, and leak volumes were affected markedly by ventilator settings, particularly frequency: leaks were much greater at frequencies <100 min(-1). The leak/expired volume ratio varied between 0% and 92%. Leak and entrained volumes increased progressively with more proximally situated fistulae, whereas the measured expired volume decreased. Leak volumes with a 2 mm fistula were approximately half that of a 10 mm fistula across all ventilator frequencies. All volumes increased with increased driving pressure. The optimum injection time varied depending on BPF position and the accepted compromise between leak and expired volumes. Entrained volume contributed up to 50% of the total tidal volume. CONCLUSIONS: These data suggest that gas leak will be minimized and ventilator volumes maintained during jet ventilation using frequencies >200 min(-1) and lower driving pressures, but confirmatory clinical studies are required. Values displayed by the jet ventilator are unreliable.

High-frequency jet ventilation shortened the duration of gas embolization during laparoscopic liver resection in a porcine model.

BACKGROUND: Positive pressure mechanical ventilation causes rhythmic changes in thoracic pressure and central blood flow. If entrainment occurs, it could be easier for carbon dioxide to enter through a wounded vein during laparoscopic liver lobe resection (LLR). High-frequency jet ventilation (HFJV) is a ventilating method that does not cause pronounced pressure or blood flow changes. This study aimed to investigate whether HFJV could influence the frequency, severity, or duration of gas embolism (GE) during LLR. METHODS: Twenty-four anaesthetized piglets underwent lobe resection and were randomly assigned to either normal frequency ventilation (NFV) or HFJV (n=12 per group). During resection, a standardized injury to the left hepatic vein was created to increase the risk of GE. Haemodynamic and respiratory variables were monitored. Online blood gas monitoring and transoesophageal echocardiography were used. GE occurrence and severity were graded as 0 (none), 1 (minor), or 2 (major), depending on the echocardiography results. RESULTS: GE duration was shorter in the HFJV group (P=0.008). However, no differences were found between the two groups in the frequency or severity of embolism. Incidence of Grade 2 embolism was less than that found in previous studies and physiological responses to embolism were variable. CONCLUSION: HFJV shortened the mean duration of GE during LLR and was a feasible ventilation method during the procedure. Individual physiological responses to GE were unpredictable.

Percutaneous transtracheal ventilation in an obstructed airway model in post-apnoeic sheep.

BACKGROUND: Temporizing oxygenation by percutaneous transtracheal ventilation (PTV) is a recommended emergency technique in 'can't intubate, can't oxygenate' (CICO) situations. Barotrauma risk increases if expiration is obstructed. The Ventrain(®) is a new PTV device that assists expiration. Our aim was to compare key physiological outcomes after PTV with the Ventrain and the Manujet(®) in a large animal obstructed airway model. METHODS: Five anaesthetized sheep had post-apnoea PTV performed for 15 min using the Ventrain or Manujet with the proximal airway completely or critically obstructed, yielding four ventilation protocols per sheep. After apnoeic desaturation ([Formula: see text]70%), a 4 s rescue breath was delivered. Subsequent 2 s breaths were delivered whenever the airway pressure fell <10 cm H2O. RESULTS: Both devices achieved rapid re-oxygenation. There were marked device differences (Ventrain vs Manujet) in peak airway pressures with rescue (16 vs 40 cm H2O) breaths, minute ventilation (4.7 vs 0.1 litre min(-1)), and end-protocol pH (7.34 vs 7.01). There was no clinical evidence of barotrauma in any sheep after any ventilation protocol. An equilibration phase prevented large subatmospheric intrathoracic pressure development with Ventrain ventilation. CONCLUSIONS: The Ventrain provided stable oxygenation and effective ventilation at low airway pressures during emergency PTV in critically obstructed airways. The Manujet provided effective temporizing oxygenation in this situation with hypoventilation necessary to minimize barotrauma risk. The nature and extent of airway obstruction may not be known in a CICO emergency but an understanding of device differences may help inform optimal ventilation device and method selection.

Time to adequate oxygenation following ventilation using the Enk oxygen flow modulator versus a jet ventilator via needle cricothyrotomy in rabbits.

INTRODUCTION: Limited information is available on the management of the 'cannot intubate, cannot ventilate' (CICV) situation in infants. We compared the time to achieve adequate oxygenation following rescue ventilation using the Enk oxygen flow modulator (OFM) with a jet ventilator in a simulated CICV situation using the rabbit as an infant respiratory model. METHODS: Following institutional ethics committee approval, needle cricothyrotomy was performed under direct vision in nine anesthetized rabbits following surgical exposure of the larynx. After ensuring adequate level of anesthesia and analgesia, and confirming proper positioning of the 18G cannula, apnea was induced by the administration of myorelaxant and the SpO2 was allowed to drop to 75% before initiating rescue ventilation via either the OFM or jet ventilator. RESULTS: Five rabbits were ventilated with the OFM and four with the jet ventilator. Ventilation was maintained with either device for 15 min. All rabbits were successfully rescued using either device. There was no statistical difference in the time required for SpO2 to return to 80%, 85%, 90%, and 95%. CONCLUSIONS: Both devices facilitated successful rescue ventilation through a needle cricothyrotomy.