External Jet Nebulization and Measured Ventilator Performance.

BACKGROUND: During invasive ventilation, external flow jet nebulization results in increases in displayed exhaled tidal volumes (VT). We hypothesized that the magnitude of the increase is inaccurate. An ASL 5000 simulator measured ventilatory parameters over a wide range of adult settings: actual VT, peak inspiratory pressure (PIP), and time to minimum pressure. METHODS: Ventilators with internal and external flow sensors were tested by using a variety of volume and pressure control modes (the target VT was 420 mL). Patient conditions (normal, COPD, ARDS) defined on the ASL 5000 were assessed at baseline and with 3.5 or 8 L/min of added external flow. Patient-triggering was assessed by reducing muscle effort to the level that resulted in backup ventilation and by changing ventilator sensitivity to the point of auto-triggering. RESULTS: Results are reported as percentage change from baseline after addition of 3.5 or 8 L/min external flow. For ventilators with internal flow sensors, changes in displayed exhaled VT ranged from 10% to 118%, however, when using volume control, actual increases in actual VT and PIP were only 4%-21% (P = .063, .031) and 6%-24% (P = .25, .031), respectively. Changes in actual VT correlated closely with changes in PIP (P < .001; R2 = 0.68). For pressure control, actual VT decreased by 3%-5% (P = .031) and 4%-9% (P = .031) with 3.5 and 8 L/min respectively, PIP was unchanged. With external flow sensors at the distal Y-piece junction, volume and pressure changes were statistically insignificant. The time to minimum pressure increased at most by 8% (P = .02) across all modes and ventilators. The effects on muscle pressure were minimal (∼1 cm H2O), and ventilator sensitivity effects were nearly undetectable. CONCLUSIONS: External flow jet nebulization resulted in much smaller changes in volume than indicated by the ventilator display. Statistically significant effects were confined primarily to machines with internal flow sensors. Differences approached the manufacturer-reported variation in ventilator baseline performance. During nebulizer therapy, effects on VT can be estimated at the bedside by monitoring PIP.

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.

The Impact of Tracheal Stenosis on Distal Airway Pressure with Jet Ventilation.

OBJECTIVE: This study investigates the effects of tracheal stenosis on distal airway pressure during low-frequency jet ventilation (LFJV) in tracheal stenosis resection procedures, focusing on variables like stenosis size, depth, scope type, and inlet pressure. METHODS: A 3D-printed human airway model was employed, featuring inserted tracheal stenoses of varied sizes and depths. Distal airway pressure was measured with 16 pressure transducers, and data were processed via MATLAB. The study varied stenosis size, depth, scope type, and inlet pressure during five sequential jet bursts under LFJV. RESULTS: Using a subglottiscope resulted in significantly reduced distal airway pressure compared to a laryngoscope. Interestingly, neither stenosis size nor depth significantly influenced distal airway pressure. However, increased distance between the scope and stenosis raised normalized pressure. A linear rise in normalized distal airway pressure was noted with increased inlet pressure, regardless of stenosis dimensions. CONCLUSION: In this model, scope type and inlet pressure were noted to be significant determinants of distal airway pressure, while stenosis size and depth were not. The distance between the scope and the stenosis did influence distal pressures. These findings may have clinical implications for managing airway pressures in patients undergoing LFJV, potentially reducing the risk of ventilator-induced lung injury. LEVEL OF EVIDENCE: NA (Basic Research) Laryngoscope, 134:2300-2305, 2024.

Recovery and safety with prolonged high-frequency jet ventilation for catheter ablation of atrial fibrillation: A hospital registry study from a New England healthcare network.

STUDY OBJECTIVE: To investigate post-procedural recovery as well as peri-procedural respiratory and hemodynamic safety parameters with prolonged use of high-frequency jet ventilation (HFJV) versus conventional ventilation in patients undergoing catheter ablation for atrial fibrillation. DESIGN: Hospital registry study. SETTING: Tertiary academic teaching hospital in New England. PATIENTS: 1822 patients aged 18 years and older undergoing catheter ablation between January 2013 and June 2020. INTERVENTIONS: HFJV versus conventional mechanical ventilation. MEASUREMENTS: The primary outcome was post-anesthesia care unit (PACU) length of stay. In secondary analyses we assessed the effect of HFJV on intra-procedural hypoxemia, defined as the occurrence of peripheral hemoglobin oxygen saturation (SpO2) <90%, post-procedural respiratory complications (PRC) as well as intra-procedural hypocarbia and hypotension. Multivariable negative binomial and logistic regression analyses, adjusted for patient and procedural characteristics, were applied. MAIN RESULTS: 1157 patients (63%) received HFJV for a median (interquartile range [IQR]) duration of 307 (253-360) minutes. The median (IQR) length of stay in the PACU was 244 (172-370) minutes in patients who underwent ablation with conventional mechanical ventilation and 226 (163-361) minutes in patients receiving HFJV. In adjusted analyses, patients undergoing HFJV had a longer PACU length of stay (adjusted absolute difference: 37.7 min; 95% confidence interval [CI] 9.7-65.8; p = 0.008). There was a higher risk of intra-procedural hypocarbia (adjusted odds ratio [ORadj] 5.90; 95%CI 2.63-13.23; p < 0.001) and hypotension (ORadj 1.88; 95%CI 1.31-2.72; p = 0.001) in patients undergoing HFJV. No association was found between the use of HFJV and intra-procedural hypoxemia or PRC (p = 0.51, and p = 0.97, respectively). CONCLUSION: After confounder adjustment, HFJV for catheter ablation procedures for treatment of atrial fibrillation was associated with a longer length of stay in the PACU. It was further associated with an increased risk of intra-procedural abnormalities including abnormal carbon dioxide homeostasis, as well as intra-procedural arterial hypotension.

Quantitative assessment of atelectasis formation under high frequency jet ventilation during liver tumour ablation-A computer tomography study.

BACKGROUND: High frequency jet ventilation (HFJV) can be used to minimise sub-diaphragmal organ displacements. Treated patients are in a supine position, under general anaesthesia and fully muscle relaxed. These are factors that are known to contribute to the formation of atelectasis. The HFJV-catheter is inserted freely inside the endotracheal tube and the system is therefore open to atmospheric pressure. AIM: The aim of this study was to assess the formation of atelectasis over time during HFJV in patients undergoing liver tumour ablation under general anaesthesia. METHOD: In this observational study twenty-five patients were studied. Repeated computed tomography (CT) scans were taken at the start of HFJV and every 15 minutes thereafter up until 45 minutes. From the CT images, four lung compartments were defined: hyperinflated, normoinflated, poorly inflated and atelectatic areas. The extension of each lung compartment was expressed as a percentage of the total lung area. RESULT: Atelectasis at 30 minutes, 7.9% (SD 3.5, p = 0.002) and at 45 minutes 8,1% (SD 5.2, p = 0.024), was significantly higher compared to baseline 5.6% (SD 2.5). The amount of normoinflated lung volumes were unchanged over the period studied. Only a few minor perioperative respiratory adverse events were noted. CONCLUSION: Atelectasis during HFJV in stereotactic liver tumour ablation increased over the first 45 minutes but tended to stabilise with no impact on normoinflated lung volume. Using HFJV during stereotactic liver ablation is safe regarding formation of atelectasis.

Safety of High-Frequency Jet Ventilation During Image-Guided Thermal Ablation Procedures.

RATIONALE AND OBJECTIVE: Percutaneous thermal ablative technique is a common radiological procedure for malignant lesions treatment. Controlled assisted ventilation during general anesthesia is the usual mode of ventilation, but high-frequency jet ventilation (HFJV) can be a helpful alternative for the operator. The objective was to evaluate the safety of HFJV during thermal ablation procedures. MATERIALS AND METHODS: This monocentric prospective analysis included adult patients undergoing percutaneous thermal ablation procedures for abdominal tumor performed under HFJV. Procedures with a transpulmonary path were excluded. The primary outcome was the incidence of respiratory complications. Secondary outcomes included gas exchange modifications (hypercapnia, hypoxemia, pulmonary atelectasis) and the incidence of barotrauma. RESULTS: Sixty patients were included during the study period. The mean duration time was 88 min. All procedures went according to the protocol and there was no respiratory complication. There was no barotrauma event. Three patients had an exhaled capnia above 45 mmHg at the end of the procedure which normalized within 10 min of conventional ventilation. CONCLUSION: HFJV during thermal ablation procedures is safe regarding gas exchange and barotrauma. This technique could be an interesting alternative to conventional ventilation during image-guided thermal ablation procedures. Clinical Trials database This study was registered in Clinical Trials database (NCT04209608).

In-Circuit High-Frequency Jet Ventilation for Radiological Tumor Ablation: A Case Series.

High-frequency jet ventilation (HFJV) can reduce organ movement that otherwise complicates percutaneous image-guided ablation (IGA) procedures. This study describes feasibility and safety of the technique in routine use. We describe our method for the use of HFJV and present 169 consecutive cases, including IGA of tumors of the lung, liver, kidney, and pancreas. Intended oncological treatment was delivered in all cases and HFJV used for the duration of treatment in all except one case. We describe the characteristics of patients, procedures, and adverse events. It is feasible to use HFJV as the routine standard of care for IGA.

Parameters of high-frequency jet ventilation using a mechanical lung model.

High frequency jet ventilationis a mechanical lung ventilation method which uses a relatively high flow usually through an open system. This work examined the effect of high-frequency jet ventilation on respiratory parameters of an intubated patient simulated using a high-frequency jet ventilator attached to a ventilation monitor for measurements of ventilation parameters. The series of experiments altered specific parameters each time (respiratory rate, inspiratory-expiratory (I:E) ratio, and inspiratory pressure), under different lung compliances. A reduction of minute ventilation was observed alongside a rise in respiratory rate, with low airway pressures over the entire range of lung compliances. In addition, an I:E ratio of 2:1 to 1:1; and the tidal and minute volumes were directly related to the inspiratory pressure over all compliance settings. To conclude, the respiratory mechanics in high-frequency jet ventilation are very different from those of conventional rate ventilation in a lung model. Further studies on patients and/or a biological model are needed to investigate pCO2 and end-tidal carbon-dioxide during high-frequency jet ventilation.

Low Pressure Low Frequency Jet Ventilation: Techniques, Safety and Complications.

OBJECTIVE: Manual jet ventilation is a specialized oxygenation and ventilation technique that is not available in all facilities due to lack of technical familiarity and fear of complications. The objective is to review our center's 15 year experience with low pressure low frequency jet ventilation (LPLFJV). METHODS: Retrospective review of procedures utilizing LPLFJV from 2005 to 2019 were performed collecting patient demographic, surgery type and complications. Fisher exact test, Chi square, and t-test were used to determine statistical significance. RESULTS: Four hundred fifty-seven patients underwent a total of 891 microlaryngeal surgeries-279 cases for voice disorders, 179 for lesions, and 433 for airway stenosis. The peak jet pressure for all cases did not exceed 20 psi and average peak pressure for the last 100 procedures in this case series was 14.9 ± 4.6 psi. The average lowest oxygen saturation for all cases was 95% ± 0.6%. Brief intubation was required in 154 cases (17%). Surgical duration was significantly longer for cases requiring intubation P < .001. The need for intubation was not associated with smoking or cardiopulmonary disease, but was strongly associated with body mass index (BMI). Intubation rates were 7% for normal weight (BMI < 25, N = 216), 13% for overweight (BMI 25-30, N = 282), 24% for obese (BMI 30-40, N = 342), and 37% for morbidly obese (BMI > 40, N = 52) patients. Three patients developed respiratory distress in the recovery unit and 2 patients required intubation. CONCLUSION: LPLFJV assisted by intermittent endotracheal intubation is an exceedingly safe and effective intraoperative oxygenation and ventilationmodality for a broad variety of laryngeal procedure.

Very low tidal volume, high-frequency ventilation in atrial fibrillation ablation: a systematic review.

BACKGROUND: Ventilation strategies in atrial fibrillation ablation affect procedure outcomes by influencing catheter stability. Studies have highlighted favorable atrial fibrillation (AF) ablation outcomes with the use of high-frequency jet ventilation (HFJV) which has been shown to improve lesion durability, energy delivery, and tissue contact. However, this mode of ventilation is not readily available. In this systematic review, we highlight the available data on the use of very low tidal volume, high-frequency ventilation using standard ventilators that aim to provide settings similar to HFJV during AF ablations. METHODS: Using a combination of search terms in databases and manual searches in bibliographies of identified articles, we reviewed all published data reported in the English language on the use of very low tidal volume with high-frequency ventilation during atrial fibrillation ablation. RESULTS: A total of 4 manuscripts were identified; 3 cohort studies and 1 case report. The utilization of standard ventilators with a high-frequency, very low tidal volume ventilation strategy appears to closely mimic the catheter stability benefits that HFJV ventilators provide. Across the 3 cohort identified studies, the use of this ventilation strategy was associated with improved catheter stability, tissue contact, and a decrease in radiofrequency time. No increased risk was identified compared to standard ventilation. CONCLUSION: With a purpose of limiting thoracic excursion and cardiac movement, limited and sparse studies have shown improved outcomes with a very low tidal volume, high-frequency ventilation strategy. Additional studies are needed to solidify this easily accessible and widely available mode of ventilation.

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.

Use of high frequency jet ventilation as a refinement for imaging macaques with respiratory disease.

Imaging is used in human medicine to diagnose disease and monitor treatment efficacy. Computed tomography (CT) positron emission tomography (PET) and magnetic resonance (MR) are applied to animal models of infectious diseases to increase data quality, enhance their relevance to the clinical situation, and to address ethical issues through reduction of numbers and refinement of study designs. The time required for collection of MR and PET-CT scans means that normal breathing produces motion artefacts that can render images unacceptable. We report, for the first time, the use of high frequency jet ventilation (HFJV) for respiratory management during imaging of macaques. HFJV enables continuous gaseous exchange, resulting in cessation of spontaneous breathing motion thus providing a motionless field without the potential stresses induced by repeated breath-hold strategies.

Jet Ventilation in the Pregnant Patient with Airway Stenosis: Surgical Safety and Outcomes.

OBJECTIVE: To review pregnancy outcomes and the safety of jet ventilation use in the gravid patient undergoing surgical airway intervention. METHODS: A multi-institutional retrospective review of medical records was performed to identify women who underwent low-frequency jet ventilation during pregnancy for surgical treatment of airway stenosis. Postoperative complications were noted, and patients were interviewed regarding pregnancy outcomes. RESULTS: Six women were included in this series. No immediate complications relating to anesthesia or surgical intervention were noted in five of the six women. One patient with a well-known history of uncontrolled seizures experienced seizure activity postoperatively. One patient returned to the operating room at a later date for debridement of tracheal crusts. Five mothers delivered via cesarean section and one via spontaneous vaginal delivery. The mean gestation age was 37.3 weeks. One of the six infants delivered prematurely and three were delivered at low birth weight. Three of the six infants required elevated care immediately post-delivery but, at present, all are in good health. CONCLUSION: Low-frequency jet ventilation and surgical management of airway stenosis should be recognized as a safe treatment option in the gravid patient. Surgical intervention should not be delayed in patients with severe symptoms, particularly given the potential risk associated with prolonged corticosteroid use. LEVEL OF EVIDENCE: 4.

Airway Surgery Communication Protocol: A Quality Initiative for Safe Performance of Jet Ventilation.

OBJECTIVES: To assess whether manual jet ventilation can safely be performed with variable anesthesia and operating room (OR) staff experience levels and communication skills. METHODS: Jet ventilation procedures for airway stenosis at a single institution over 35 months were retrospectively reviewed. OR and anesthesia staff were assigned scores based on experience level and communication skills. Data were analyzed for any association between the experience or communication skills of the staff and the successful use of jet ventilation, complication rate, or ultimate patient outcome, controlling for intraoperative variables and patient and airway complexity. A detailed preoperative surgeon-led communication protocol was followed in all cases. RESULTS: Seventy procedures in 46 patients were performed. Jet ventilation was successful in 69 of 70 cases. No relationship was found between staff experience or communication scores and the successful use of jet ventilation, complication rate, or ultimate patient outcome. The percentage of cases performed with a fully experienced team was low, at 7.1%. The experience level of the certified registered nurse anesthetist was significantly associated with likelihood of using an adequate paralytic dose upfront (P = 0.017), which in turn correlated with shorter anesthesia time by 19.7 minutes (P = 0.0131); however, neither affected complication rate nor ultimate patient outcome. The statements above remained true in cases of medically complex patients, difficult airways with high degrees of stenosis, and multiple shift changes. CONCLUSIONS: Manual jet ventilation can be performed safely even in settings of lower staff experience level or communication skills given a surgeon experienced in the technique and a strict communication protocol. LEVEL OF EVIDENCE: 4 Laryngoscope, 130:S1-S13, 2020.

[High frequency jet ventilator - a new approach in the management of anesthesia for pediatric cardiac Magnetic Resonance Imaging: case series]. / Ventilação a jato de alta frequência ­ uma nova abordagem no manejo da anestesia para ressonância magnética em cardiologia pediátrica: série de casos.

BACKGROUND AND OBJECTIVES: Cardiac Magnetic Resonance Imaging (MRI) is a technique used for evaluation of children with congenital heart diseases. General anesthesia ensures immobility, particularly in uncooperative patients. However, chest wall movements can limit good quality scans. Prolonged apnea may be necessary to decrease respiratory motion artefacts, potentially leading to hypoxemia and other adverse events. The use of a high frequency jet ventilator may be a solution avoiding chest wall movements. CASE REPORT: We report four cases of pediatric patients, ASA II, aged between 4 and 15 years-old, scheduled for cardiac MRI. General anesthesia was proposed and parental informed consent was obtained. After general anesthesia was induced, an uncuffed endotracheal tube was inserted. Then, a 7Fr×40 cm catheter was placed through the endotracheal tube. The proximal outlet of the catheter was attached through a connecting tube to a high frequency jet ventilator (Monsoon III®, Acutronic Medical Systems). Good quality MRI images were obtained. At the end of the procedures, we observed increased salivation and increased end-tidal CO2 (60-70 mmHg), in all patients. The patients were extubated after normocapnia was achieved and neuromuscular blockade reversed. Following appropriate recovery time, the four children were discharged home the same day. CONCLUSIONS: This case series demonstrates that the use of a high frequency jet ventilator for cardiac MRI was feasible, safe, providing good quality cardiac imaging and avoiding anesthesia personnel to be inside the hazardous environment of MRI room. Future studies are needed to confirm its safety and efficiency in pediatric patients.

High frequency jet ventilator ‒ a new approach in the management of anesthesia for pediatric cardiac Magnetic Resonance Imaging: case series / Ventilação a jato de alta frequência - uma nova abordagem no manejo da anestesia para ressonância magnética em cardiologia pediátrica: série de casos

Abstract Background and objectives: Cardiac Magnetic Resonance Imaging (MRI) is a technique used for evaluation of children with congenital heart diseases. General anesthesia ensures immobility, particularly in uncooperative patients. However, chest wall movements can limit good quality scans. Prolonged apnea may be necessary to decrease respiratory motion artefacts, potentially leading to hypoxemia and other adverse events. The use of a high frequency jet ventilator may be a solution avoiding chest wall movements. Case report: We report four cases of pediatric patients, ASA II, aged between 4 and 15 years-old, scheduled for cardiac MRI. General anesthesia was proposed and parental informed consent was obtained. After general anesthesia was induced, an uncuffed endotracheal tube was inserted. Then, a 7Fr × 40 cm catheter was placed through the endotracheal tube. The proximal outlet of the catheter was attached through a connecting tube to a high frequency jet ventilator (Monsoon III®, Acutronic Medical Systems). Good quality MRI images were obtained. At the end of the procedures, we observed increased salivation and increased end-tidal CO2 (60-70 mmHg), in all patients. The patients were extubated after normocapnia was achieved and neuromuscular blockade reversed. Following appropriate recovery time, the four children were discharged home the same day. Conclusions: This case series demonstrates that the use of a high frequency jet ventilator for cardiac MRI was feasible, safe, providing good quality cardiac imaging and avoiding anesthesia personnel to be inside the hazardous environment of MRI room. Future studies are needed to confirm its safety and efficiency in pediatric patients.

Resumo Justificativa e objetivos: A ressonância magnética (RM) cardíaca é uma técnica usada na avaliação de crianças com cardiopatias congênitas. A anestesia geral garante imobilidade, especialmente em pacientes não cooperadores, porém os movimentos da parede torácica podem limitar a boa qualidade dos exames. A apneia prolongada pode ser necessária para diminuir os artefatos do movimento respiratório, potencialmente levando à hipoxemia e outros eventos adversos. O uso de ventilação a jato de alta frequência pode ser uma solução para evitar os movimentos da parede torácica. Relato de caso: Relatamos quatro casos de pacientes pediátricos, ASA II, entre 4-15 anos, programados para ressonância magnética cardíaca. Uma anestesia geral foi proposta e assinaturas em termo de consentimento livre e esclarecido foram obtidas dos pais. Após a indução da anestesia geral, um tubo endotraqueal sem balonete foi inserido. Em seguida, um cateter de 7Fr × 40 cm foi inserido através do tubo endotraqueal. A saída proximal do cateter foi conectada, mediante um tubo conector, a um sistema de ventilação a jato de alta frequência (Monsoon III®, Acutronic Medical Systems). Imagens de ressonância magnética de boa qualidade foram obtidas. No fim dos procedimentos, observamos aumento tanto de salivação quanto de CO2 expirado (60-70 mmHg) em todos os pacientes. Os pacientes foram extubados após a obtenção de normocapnia e reversão do bloqueio neuromuscular. Após o tempo de recuperação apropriado, as quatro crianças receberam alta no mesmo dia. Conclusões: Esta série de casos demonstra que o uso de um sistema de ventilação a jato de alta frequência para ressonância magnética cardíaca é viável e seguro, além de fornecer imagens cardíacas de boa qualidade e evitar a presença da equipe de anestesia dentro do ambiente de risco da sala de ressonância magnética. Estudos futuros são necessários para confirmar sua segurança e eficiência em pacientes pediátricos.