Test the hypothesis that the center of ventilation, a measure of ventro-dorsal atelectasis, is posterior during supraglottic ventilation indicating better dependent-lung ventilation. Secondarily, we tested the hypothesis that supraglottic ventilation improves oxygenation and carbon dioxide elimination.

Supraglottic and subglottic jet ventilation are both used during laryngotracheal surgery. Supraglottic jet ventilation may better prevent atelectasis and provide superior ventilation.

Randomized, cross-over trial.

Operating rooms.

Patients having elective micro-laryngotracheal surgery.

Patients were sequentially ventilated for 5 min with one randomly selected type of jet ventilation before being switched to the alternative method.

Regional ventilation distribution was estimated using electrical impedance tomography, with arterial oxygenation and carbon dioxide partial pressures being simultaneously evaluated.

Thirty patients completed the study. There were no statistically significant or clinically meaningful differences in the center of ventilation with supraglottic and subglottic ventilation. However, ventilation with the supraglottic approach was about 4 % higher in the ventromedial lung region and about 4 % lower in the dorsal lung. Surprisingly, arterial blood oxygenation was considerably worse with supraglottic (173 [156, 199] mmHg) than subglottic ventilation (293 [244, 340] mmHg). Arterial carbon dioxide partial pressure was near 40 mmHg with each approach, although slightly lower with supraglottic jet ventilation.

The center of ventilation distribution, a measure of atelectasis, was similar with supraglottic and subglottic jet ventilation. Subglottic jet ventilation improved the dorsal-dependent lung region and provided superior arterial oxygenation. Both techniques effectively eliminated carbon dioxide, with the supraglottic approach demonstrating slightly superior efficacy.

Introduction: Superimposed high-frequency jet ventilation (SHFJV) is a new type of jet ventilation that simultaneously uses high- and low-frequency types of jet ventilation. We compared SHFJV with the conventional high-frequency jet ventilation (CHFJV) in interventional bronchoscopy in terms of safety and effectiveness. Methods: A multi-centre prospective random single-blind clinical trial was conducted by three interventional bronchoscopy centres. Patients who underwent diagnostic or therapeutic bronchoscopy under general anaesthesia were admitted and divided into two groups: SHFJV group (trial group) and CHFJV group (control group). PaO2 and PaCO2 were recorded before anaesthesia and during and after the procedure. SpO2 and etCO2 were recorded every 10 min throughout the procedure. Patients were observed until 24 h post-bronchoscopy. Results: Sixty patients were included in the study. Twenty-nine were in the trial group, and 31 were in the control group. Both groups had no significant differences in demographic data. In the control group, the PaO2 measured in the operation was higher than that in the trial group (p = 0.023). The values of etCO2 in the control group were more dispersed than those of the trial group. When the procedure time was over 90 minutes, the etCO2 in the control group significantly increased (p = 0.01), while the etCO2 in trial group remained stable (p = 0.594). There were more patients with PaCO2 ≥ 50 mmHg during the procedure in the control group than in the trial group (p = 0.042). Conclusion: SHFJV is effective and safe in interventional bronchoscopy. It may provide more effective and stabilised ventilation than CHFJV in cases with long procedure times.

Superimposed high-frequency jet ventilation (SHFJV) is suitable for respiratory motion reduction and essential for effective lung tumor ablation. Fluid filling of the target lung wing one-lung flooding (OLF) is necessary for therapeutic ultrasound applications. However, whether unilateral SHFJV allows adequate hemodynamics and gas exchange is unclear.

To compared SHFJV with pressure-controlled ventilation (PCV) during OLF by assessing hemodynamics and gas exchange in different animal positions.

SHFJV or PCV was used alternatingly to ventilate the non-flooded lungs of the 12 anesthetized pigs during OLF. The animal positions were changed from left lateral position to supine position (SP) to right lateral position (RLP) every 30 min. In each position, ventilation was maintained for 15 min in both modalities. Hemodynamic variables and arterial blood gas levels were repeatedly measured.

Unilateral SHFJV led to lower carbon dioxide removal than PCV without abnormally elevated carbon dioxide levels. SHFJV slightly decreased oxygenation in SP and RLP compared with PCV; the lowest values of PaO2 and PaO2/FiO2 ratio were found in SP [13.0; interquartile range (IQR): 12.6-5.6 and 32.5 (IQR: 31.5-38.9) kPa]. Conversely, during SHFJV, the shunt fraction was higher in all animal positions (highest in the RLP: 0.30).

In porcine model, unilateral SHFJV may provide adequate ventilation in different animal positions during OLF. Lower oxygenation and CO2 removal rates compared to PCV did not lead to hypoxia or hypercapnia. SHFJV can be safely used for lung tumor ablation to minimize ventilation-induced lung motion.

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.

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.

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.

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.

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.

We seek to use computed tomography (CT) to characterize regional lung parenchymal deformation during high-frequency and multi-frequency oscillatory ventilation. Periodic motion of thoracic structures results in artifacts of CT images obtained by standard reconstruction algorithms, especially for frequencies exceeding that of the X-ray source rotation. In this paper, we propose an acquisition and reconstruction technique for high-resolution imaging of the thorax during periodic motion. Our technique relies on phase-binning projections according to the frequency of subject motion relative to the scanner rotation, prior to volumetric reconstruction. The mathematical theory and limitations of the proposed technique are presented, and then validated in a simulated phantom as well as a living porcine subject during oscillatory ventilation. The 4-D image sequences obtained using this frequency-selective reconstruction technique yielded high-spatio-temporal resolution of the thorax during periodic motion. We conclude that the frequency-based selection of CT projections is ideal for characterizing dynamic deformations of thoracic structures that are ordinarily obscured by motion artifact using conventional reconstruction techniques.

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.

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.

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.

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.

Superimposed high-frequency jet ventilation (SHFJV) has proved to be safe and effective in clinical practice. However, it is unclear which frequency range optimizes ventilation and gas exchange. The aim of this study was to systematically compare high-frequency jet ventilation (HFJV) with HFJV by assessing chest wall volume variations (ΔEEV(CW)) and gas exchange in relation to variable high frequency.

SHFJV or HFJV were used alternatively to ventilate the lungs of 10 anaesthetized pigs (21-25 kg). The low-frequency component was kept at 16 min(-1) in SHFJV. In both modes, high frequencies ranging from 100 to 1000 min(-1) were applied in random order and ventilation was maintained for 5 min in all modalities. Chest wall volume variations were obtained using opto-electronic plethysmography. Airway pressures and arterial blood gases were measured repeatedly.

SHFJV increased ΔEEV(CW) compared with HFJV; the difference ranged from 43 to 68 ml. Tidal volume (V(T)) was always >240 ml during SHFJV whereas during HFJV ranged from 92 ml at the ventilation frequency of 100 min(-1) to negligible values at frequencies >300 min(-1). We observed similar patterns for Pa(O₂) and Pa(CO₂). SHFJV provided generally higher, frequency-independent oxygenation (Pa(O₂) at least 32.0 kPa) and CO₂ removal (Pa(CO₂) ∼5.5 kPa), whereas HFJV led to hypoxia and hypercarbia at higher rates (Pa(O₂) <10 kPa and Pa(CO₂)>10 kPa at f(HF)>300 min(-1)).

In a porcine model, SHFJV was more effective in increasing end-expiratory volume than single-frequency HFJV, but both modes may provide adequate ventilation in the absence of airway obstruction and respiratory disease, except for HFJV at frequencies ≥300 min(-1).

To determine the suitability of different superimposed high-frequency jet ventilation (SHFJV) application methods during tracheal bleeding.

To determine the effect of SHFJV on the aspiration of blood during tracheal bleeding.

A test lung was ventilated using SHFJV via a rigid endoscope, a jet laryngoscope and a 4-lumen jet catheter. Packed red blood cells (PRBCs) were injected into the artificial trachea caudally to the rigid endoscope and jet laryngoscope ventilation, and both caudally and cranially during ventilation via the 4-lumen jet catheter, and the migration of PRBCs during ventilation was studied using continuous video recording.

Migration of blood into the lower respiratory tract did not occur during SHFJV via the rigid endoscope and jet laryngoscope and via the 4-lumen jet catheter with the bleeding caudal to ventilation source. If the bleeding was cranial to the 4-lumen jet catheter ventilation, migration of blood into the lower respiratory tract was seen when reflux of blood reached the entrainment area. From this area, blood is transported within the jet stream into the lower respiratory tract.

SHFJV protects the lower respiratory tract from blood aspiration in case of tracheal bleeding. During SHFJV via the 4-lumen jet catheter, aspiration of blood only occurs if bleeding is localized cranial to the 4-lumen jet catheter ventilation. In case of heavy tracheal bleeding, the jet sources should be positioned cranial to the site of bleeding.

Multidetector ECG-gated CT angiography permits imaging of structures such as the coronary arteries and pulmonary veins with peripheral administration of contrast media. Respiratory motion artifact limits the applicability of this technique in critically ill patients due to an inability to cooperate with prolonged breath holds necessary for quality images. A case in which high-frequency jet ventilation via an uncuffed tracheostomy tube in an unmedicated patient permitted respiratory immobilization sufficient to acquire diagnostic images, is presented.