Incendiary characteristics of a new laser-resistant endotracheal tube

The Effect of Laser-Resistant Endotracheal Tube Design on Airflow Dynamics: A Benchtop and Clinical Study

OBJECTIVE

Compare ventilation pressures of 2 endotracheal tube designs used in laser airway surgery in clinical practice and with a benchtop model to elucidate differences and understand the design elements that impact airflow dynamics.

METHODS

Ventilatory and aerodynamic characteristics of the laser resistant stainless-steel endotracheal tube (LRSS-ET) design and the laser resistant aluminum-wrapped silicone endotracheal tube (LRAS-ET) design were compared. Ventilatory parameters were collected for 32 patients undergoing laser-assisted airway surgery through retrospective chart review. An in vitro benchtop simulation measured average resistance and centerline turbulence intensity of both designs at various diameters and physiological frequencies.

RESULTS

Baseline patient characteristics did not differ between the 2 groups. Clinically, the median LRAS-ET peak inspiratory pressure (PIP; 21.00 cm H2O) was significantly decreased compared to LRSS-ET PIP (34.67 cm H2O). In benchtop simulation, the average PIP of the LRAS-ET was significantly lower at all sizes and frequencies. The LRSS-ET consistently demonstrated an increased resistance, although no patterns were observed in turbulence intensity data between both designs.

CONCLUSION

The benchtop model demonstrated increased resistance in the LRSS-ET compared to the LRAS-ET at all comparable sizes. This finding is supported by retrospective ventilatory pressures during laser airway surgery, which show significantly increased PIPs when comparing identically sized inner diameters. Given the equivocal turbulence intensity data, these differences in resistance and pressures are likely caused by wall roughness and intraluminal presence of tubing, not inlet or outlet geometries. The decreased PIPs of the LRAS-ET should assist in following lung protective ventilator management strategies and reduce risk of pulmonary injury and hemodynamic instability to the patient.

Nd-YAG laser ignition of silicone endobronchial stents

STUDY OBJECTIVES

To test the incendiary characteristics of various silicone endobronchial stents under the impact of the Nd-YAG laser.

DESIGN

In vitro study in the laser laboratory of a university-affiliated city hospital.

SETTING

The experiments were performed in a reaction chamber under controlled oxygen concentrations. The radiolucent and radiopaque Dumon silicone stent (Novatech; Aubagne, France) and the tracheal part of the Dynamic stent (Ruesch AG; Kernen, Germany) were tested. The Dumon stents were either clean, covered with a thin layer of blood, or mounted on fresh pig tracheal wall. The laser was aimed on them perpendicularly from distances of 1.0 cm and 0.5 cm.

INTERVENTIONS

Minimal oxygen concentration to allow ignition and impact time for power outputs (POs) between 10 W and 80 W were determined.

MEASUREMENTS AND RESULTS

The lowest oxygen concentration that allowed ignition of some stents was 40%. The clean radiolucent stent could not be ignited with up to 100% ambient oxygen concentration. Radiopacity, presence of blood, tracheal wall, and metal, as well as higher PO and shorter distance of the laser probe decreased impact time to ignition. The radiopaque blood-covered stent was most easily ignited. For this stent, at a PO of 40 W, impact time to ignition was 1.5 +/- 0.2 s, and at 30 W was 2.6 +/- 0.3 s.

CONCLUSIONS

At ambient oxygen concentrations > or = 40%, silicone stents can catch fire. Depending on the condition of the stent, the distance of the laser probe, and PO, ignition can occur after short impact times. To prevent stent ignition, oxygen concentration should be kept < 40%. When unusual circumstances require working with higher oxygen concentrations, pulse duration needs to be limited or stent removal might be considered before firing the laser.

Electrocautery-ignited endotracheal tube fire: case report

The risk of fire in the airway associated with laser surgery is well known, but there are reports of endotracheal tube fires ignited by electrocautery, particularly during pharyngeal surgery or tracheostomy or both. This uncommon complication has potentially devastating consequences. Surgeons undertaking these procedures should be aware of this complication and be familiar with measures to avoid them. We present a case report of an electrocautery-ignited endotracheal tube fire during an elective tracheostomy, which resulted in the patient's death.

The incendiary characteristics of the laryngeal and reinforced laryngeal mask airway to CO2 laser strike--a comparison with two polyvinyl chloride tracheal tubes

The incendiary characteristics of the laryngeal and reinforced laryngeal mask airway to the CO2 laser have been compared with two polyvinyl chloride tracheal tubes. Three different power densities (2.35, 4.7 and 9.8 x 10(3) watt/cm2) were used, with either oxygen or a 30% oxygen/70% nitrous oxide mixture flowing down the tube. The laryngeal mask airway (and reinforced model) was shown to be more resistant than the polyvinyl chloride tracheal tubes. The laryngeal mask tube could not be ignited at a power density of 2.25 x 10(3) watt/cm2 after five minutes, although penetration occurred in 20-30 seconds. A layer of silica ash built up at the impact site and protected the underlying tube. The laryngeal mask airway cuff was penetrated at 3 to 5 seconds. At this power density the polyvinyl chloride tube ignited in 2 to 8 seconds and the cuff was penetrated in 0.1 seconds. At the highest power density the tubes of all airways ignited within 0.2 seconds. The possibilities for improving the incendiary characteristics of the laryngeal mask airway are discussed.