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The Veres Adapter

Clinical Experience with a New Device for Jet Ventilation via a Laryngeal Mask Airway During Flexible Bronchoscopy

Veres, Jan, MD*; Slavei, Krisztina, MD; Errhalt, Peter, MD*; Seyr, Michaela, MD; Ihra, Gerald, MD

doi: 10.1213/ANE.0b013e3182080407
Technology, Computing, and Simulation: Brief Report
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BACKGROUND: A new device was developed to deliver high-frequency jet ventilation via a laryngeal mask airway (LMA). We investigated its use during flexible fiberoptic bronchoscopy in anesthetized patients.

METHODS: Thirty adults were studied during interventional bronchoscopy. After facemask ventilation, the Veres adapter was connected to a size 4 or 5 LMA, and superimposed high-frequency jet ventilation was performed. Oxygen saturation, transcutaneous carbon dioxide, supraglottic airway pressure, and hemodynamic data were recorded and analyzed.

RESULTS: Procedures were performed under stable hemodynamic conditions. Short procedure times and fast recovery were observed. Mild hypercapnia was the most common minor adverse effect (n = 16). One patient developed a pneumothorax after peripheral biopsy, 1 patient had a stiff chest during bronchoscopy, resulting in high airway pressures, and 1 patient required continuous positive airway pressure mask ventilation in the postoperative care unit.

CONCLUSIONS: We report the clinical use of the Veres adapter in conjunction with an LMA to achieve rapid surgical access and adequate ventilation during flexible bronchoscopy. As an alternative to the use of an endotracheal tube, the new system may better maintain the airway during interventional and diagnostic bronchoscopy because of the larger diameter conduit.

Published ahead of print January 13, 2011

From the *Department of Pulmonology, Landesklinikum Krems, Krems an der Donau; Department of Anesthesiology, Intensive Care and Emergency Medicine, Landesklinikum Krems, Krems an der Donau; and Department of Anesthesiology, Intensive Care Medicine and Pain Therapy, Medical University Vienna, Vienna, Austria.

The authors declare no conflicts of interest.

Reprints will not be available from the authors.

Address correspondence to Gerald Ihra, MD, Department of Anesthesiology, Intensive Care Medicine and Pain Therapy, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria. Address e-mail to gerald.ihra@meduniwien.ac.at.

Accepted November 9, 2010

Published ahead of print January 13, 2011

High-frequency jet ventilation (HFJV) is an alternative technique to provide pulmonary gas exchange via small-bore cannulas or catheters.1 Its advantages became evident in endoscopic airway procedures.2,3 Jet gas may be administered when access to the patient's airway is restricted or when instruments limit the airway diameter. In clinical practice, fiberoptic bronchoscopes can be passed through the nasal pathway during spontaneous breathing or via an endotracheal tube in anesthetized patients. To avoid the use of muscle relaxants for short procedures, a laryngeal mask airway (LMA) has been successfully used as a conduit during flexible fiberoptic bronchoscopy.4 The LMA has proved to be an extremely valuable supraglottic airway device. It is easy to use and was shown to be superior to the facemask and the tracheal tube.5 In comparison to other routes, the lowest complication rates and shortest procedure times during bronchoscopy have been reported when using the LMA.6 The Veres adapter was developed to deliver HFJV via an LMA. Because supraglottic combined-frequency jet ventilation has been shown to be more effective than single-jet ventilation,7 the Veres has 2 integrated injectors. This study demonstrates its clinical use in anesthetized patients.

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METHODS

The Veres adapter consists of a T-shaped tube made of stainless steel (length 13.2 cm, internal diameter [ID] 15 mm) open at both ends (Carl Reiner Corp., Vienna, Austria). One end connected to the LMA and the flexible bronchoscope is introduced through the other end. Two integrated injectors (1.5 mm ID) superimpose HFJV.8 The injectors are welded to the jet adapter's wall in the proximal half of the tube to direct the jet stream along the central axis of the tube and avoid protrusion into the lumen. Two additional channels on the opposite side of the tube's wall serve to measure pressure and sample gases at the distal end of the device. Plugs to connect the device with the jet tubing and the monitoring lines of the ventilator are integrated on either side of the proximal tube's T-bar (Fig. 1). One plug serves to connect with the low-frequency (LF) and the high-frequency (HF) jet streams. The jet gas is directed into 2 separate injectors. The second plug is used to connect with pressure and gas monitoring via 2 separate lines from the ventilator (Fig. 2).

Figure 1

Figure 1

Figure 2

Figure 2

After we obtained approval from the local supervisory authority and obtained the patients' informed consent, 30 adults (age >18 years, weight <120 kg) admitted for intra- or transbronchial biopsy guided by endobronchial ultrasound, cryotherapy, bronchial lavage, hemostyptic therapy, resection or excision of tumors, or diagnostic bronchoscopy were studied. Pulmonary function analysis was performed before the intervention to determine lung volumes, flow rates, airway resistance, and arterial blood gas tensions (PaO2, PaCO2). Oral premedication consisted of 7.5 mg midazolam administered 1 hour before the endoscopic procedure. Anesthesia was administered using a 1 μg · kg−1 remifentanil bolus (maximum dose limit 100 μg), a 0.25 μg · kg−1 · min−1 infusion, a 2 mg · kg−1 propofol bolus, and a 50 to 70 μg · kg−1 · min−1 propofol infusion. Muscle relaxants were not given. After facemask ventilation, a size 4 or 5 LMA was inserted and its airtight seal was tested. The Veres adapter was connected to the proximal end of the LMA. With an additional flexible metal arm clamped to one side of the operating table, the Veres adapter was locked into position. HFJV was provided by a Twinstream® jet ventilator (Carl Reiner Corp.) as described previously.8 Two jet streams, one at LF and one at HF, were applied simultaneously via 2 separate injectors integrated into the adapter's wall (Fig. 3). LF and HF were set to 12 min−1 and 200 min−1, driving pressures at 0.7 to 1.5 bar according to lung and thoracic rigidity, and inspiratory to expiratory time ratios at 1:1 and 1:1.5. Fraction of inspired oxygen was set to 1.0. The electrocardiogram and noninvasive arterial blood pressure were recorded. The effects of ventilation were assessed by observation of chest movement, continuous monitoring of peripheral oxygen saturation (SpO2), and transcutaneous carbon dioxide tension (PtcCO2) (TCM 40; Radiometer Corp., Copenhagen, Denmark). Ventilation was considered adequate when PtcCO2 was kept within a range of ±10% of the baseline value determined before induction of anesthesia. To increase or decrease minute ventilation, the driving pressure of the LF jet stream was increased or decreased. Bronchoscopy was performed using flexible fiberscopes (Olympus BF 1T180, outside diameter 6 mm, or Olympus BF XP160F, outside diameter 5.5 mm, Olympus Corp., Tokyo, Japan). Lidocaine 1% solution was administered at a total dose of 300 mg in a volume of 30 mL to cover the surface of the trachea and bronchi for topical anesthesia. Excess solution was removed by suction via the endoscope. An additional 40-μg remifentanil bolus was given IV when systolic blood pressure increased 10% above baseline. At the end of the procedure, the administration of drugs was terminated and jet ventilation was continued until spontaneous ventilation resumed and the LMA was removed. Chest radiographs were obtained postoperatively in patients who underwent biopsy. Values are presented as means ± SD unless noted otherwise. The correlation between airway pressure and body mass index was calculated using Prism 5 (GraphPad®, La Jolla, CA).

Figure 3

Figure 3

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RESULTS

Patient Characteristics and Baseline Pulmonary Function

Thirty consecutive adults scheduled for diagnostic or therapeutic flexible fiberoptic bronchoscopy were studied. Patient characteristics are shown in Table 1. Indications for the procedure included bronchial carcinoma (57%), sarcoidosis (13%), and other lung diseases (30%).

Table 1

Table 1

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Jet Ventilation

The median duration of jet ventilation was 22 minutes (range 10–84 minutes). In 5 patients (17%), the duration of endoscopy exceeded 1 hour. PtcCO2 recorded after 10 minutes of jet ventilation was 45.3 ± 8.2 mm Hg. One patient presented with an SpO2 of 86% preoperatively, which increased instantly during HFJV to 95%. SpO2 was 97% ± 2% after 10 minutes of HFJV. Average driving pressures of the HF and LF jet streams were 1.03 ± 0.19 bar and 1.07 ± 0.16 bar, respectively. In 3 patients, the rate of the LF ventilation increased from 12 min−1 to a maximum of 20 min−1 to keep PtcCO2 values at baseline values. Figure 4 shows upper airway pressures. All patients remained hemodynamically stable (mean arterial blood pressure 77.8 ± 17.0 mm Hg). SpO2 decreased below 90% in 4 patients for a few minutes during bronchial lavage, and there was a deliberate reduction of fraction of inspired oxygen to 0.21. One patient developed a pneumothorax after peripheral biopsy. One patient had an increased peak airway pressure (28 cm H2O), and 1 patient required continuous positive airway pressure mask ventilation in the postoperative care unit to improve oxygenation.

Figure 4

Figure 4

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DISCUSSION

Our results demonstrate that the Veres adapter may be a valuable tool to deliver jet ventilation to patients undergoing interventional or diagnostic fiberoptic bronchoscopy. Access for flexible bronchoscopy can be by the LMA in anesthetized patients. Future studies are needed to determine whether procedure times are reduced and anesthesia recovery is faster with this new device. In contrast to conventional respirators, jet ventilators deliver gas when airways are partially obstructed by instruments. HFJV has been used in rigid and flexible bronchoscopy.3,9,10 Tidal volumes were injected via small-bore catheters placed in channels or via side ports of bronchoscopes. The use of an LMA improves access, especially when a high tracheal stenosis is treated.11,12 The combined use of HFJV with an LMA has also been reported.13 Although the Swivel adapter provided access for various instruments or jet lines, HFJV is delivered more effectively via the Veres integrated injectors. The Veres facilitates jet ventilation independent of the bronchoscope's position and can be used for simultaneous application of 2 jet streams, which is more effective than single-jet ventilation.7 The airway will be less compromised by the combined use of the Veres adapter and the LMA than with an endotracheal tube. The introduction of a bronchoscope with an external diameter of 6 mm will lead to a 56% reduction in the cross-sectional area of a conventional tracheal tube (ID 8 mm). It will lead to only a 16% reduction in the Veres adapter (ID 15 mm) and a 27% reduction in an LMA (ID 11.5 mm). Limitations of this combined technique include incorrect positioning of the LMA,14 the physical properties of HF ventilation,1,15 and the application of high-pressure gas.16 Gastric insufflation due to gas leakage into the esophagus and damage to laryngeal structures are well known but rare and minor complications associated with the use of the LMA. The risk of gas insufflation into the stomach under our study conditions would result from incomplete sealing of the airway with the LMA.

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ACKNOWLEDGMENTS

We thank the technicians at Carl Reiner Corp., Vienna, Austria, especially Dominik Lirsch, for the technical advice and assistance in the development and production of the Veres adapter.

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