Nd-YAG laser ignition of silicone endobronchial stents

Anesthesia for Advanced Bronchoscopic Procedures: State-of-the-Art Review

The bronchoscopic procedures have seen a remarkable increase in both numbers and complexity. Although many anesthesia providers have kept pace with the challenge, the practice is varied and frequently suboptimal. Shared airway during bronchoscopy poses unique challenges. The available reviews have tried to address this lacuna; however, these have frequently dealt with the technical aspects of bronchoscopy than anesthetic challenges. The present review provides evidence-based management insights into anesthesia for bronchoscopy-both flexible and rigid. A systematic approach toward pre-procedural evaluation and risk stratification is presented. The possible anatomical and physiological factors that can influence the outcomes are discussed. Pharmacological principles guiding sedation levels and appropriate selection of sedatives form the crux of safe anesthetic management. The newer and safer drugs that can have potential role in anesthesia for bronchoscopy in the near future are discussed. Ventilatory strategies during bronchoscopy for prevention of hypoxia and hypercarbia are emphasized.

Bronchoscopic management of malignant airway obstruction

Approximately one-third of patients with lung cancer will develop airway obstruction and many cancers lead to airway obstruction through meta stases. The treatment of malignant airway obstruction is often a multimodality approach and is usually performed for palliation of symptoms in advanced lung cancer. Removal of airway obstruction is associated with improvement in symptoms, quality of life, and lung function. Patient selection should exclude patients with short life expectancy, limited symptoms, and an inability to visualize beyond the obstruction. This review outlines both the immediate and delayed bronchoscopic effect options for the removal of airway obstruction and preservation of airway patency with endobronchial stenting.

Endobronchial therapy with a thulium fiber laser (1940 nm)

BACKGROUND

Nd:YAG laser (1064 nm) is standard in bronchology. The thulium fiber laser (1940 nm) has a nearly 1000-fold increased absorption in water, enabling precise tissue ablation with a small margin of coagulation, whereas 1064-nm laser light penetrates deeper into tissue with less controllable effects.

OBJECTIVES

To assess the safety, feasibility, and versatility of endobronchial thulium laser therapy in an observational cohort study.

METHODS

Endobronchial treatment with the thulium fiber laser was performed in a cohort study of 187 bronchoscopies on 132 consecutive patients with 135 endobronchial lesions amenable to laser resection.

RESULTS

The thulium fiber laser produced superficial, precise, and rapid tissue ablation. Eighty-one lesions were completely vaporized; 82 lesions were treated by deep tissue destruction by inserting the fiber into tissue followed by mechanical resection. Tumor bleeding was coagulated with rapid and sustained hemostasis (n = 28). Nitinol stents were removed after resection of severe granulation tissue overgrowth (n = 10). Intact stents were maintained after ablation of in-stent tissue (n = 47). In 11 cases, bleeding occurred during laser treatment (n = 11 of 187). Power settings between 5 and 20 W were found to be safe.

CONCLUSIONS

Endobronchial therapy with the thulium laser at 1940 nm seems to be safe, feasible, and highly versatile for treatment of airway stenosis and stent obstruction caused by tissue ingrowth. Further studies are warranted.

Airway fire injury during rigid bronchoscopy in a patient with a silicon stent -A case report-

Therapeutic bronchoscopy is widely employed as an effective first-line treatment for patients with central airway obstructions. Airway fires during rigid bronchoscopy are rare, but can have potentially devastating consequences. Pulmonologist and anesthesiologist undertaking this type of procedure should be aware of this serious problem and be familiar with measures to avoid this possibly fatal complication. We report the case of a 24-year-old patient with a silicone stent who experienced an electrocautery-induced airway fire during rigid bronchoscopy.

KTP laser and nitinol alloy stents: are they compatible?

BACKGROUND/OBJECTIVE

Nitinol alloy stents are in frequent use in recanalizing malignant airway stenoses. Potassium titanyl phosphate (KTP) is one of the lasers of choice in removal of obstructing airway lesions. There is a paucity of research regarding the safety of these advances working together.

STUDY DESIGN/MATERIALS AND METHODS

In vitro study involving direct contact application of KTP laser with nitinol alloy stents under microscope guidance in varying gaseous environments.

RESULTS

Stent damage can occur once power settings exceed one watt. Complete stent destruction occurs regardless of gaseous environment at a mere three watts of power.

CONCLUSIONS

Our results suggest that KTP laser is unsafe to use in the presence of a nitinol alloy stent, regardless of the gaseous environment.

In vitro study of the safety limits of bronchoscopic argon plasma coagulation in the presence of airway stents

OBJECTIVE AND BACKGROUND

The purpose of this study was to identify the safety limits of bronchoscopic argon plasma coagulation (APC) around indwelling airway stents.

METHODOLOGY

This is an experimental in vitro study simulating a patient-care environment. Uncovered and covered Nitinol (Ultraflex), uncovered and covered Wallstent and studded silicone stents were deployed in the tracheobronchial tree of a ventilated and oxygenated heart-lung block from an expired pig. APC was performed at power settings of 40 and 80 W using F(I)O(2) of 0.21, 0.40 and 1.00 and an argon gas-flow rate of 0.8 L/min through a flexible fiberoptic bronchoscope. The primary outcome was the time taken for the APC to cause stent damage. Stent damage was defined as discoloration, ignition or rupture.

RESULTS

Airway fires involving all five stents consistently occurred in the presence of 100% oxygen at powers of 40 W and 80 W. At lower F(I)O(2) (0.21 and 0.40) silicone stents were not damaged at 40 W and 80 W. Uncovered Ultraflex stents were undamaged using 40 W at either F(I)O(2) (0.21 and 0.40), but could be damaged using both F(I)O(2) levels when the power was increased to 80 W. Covered Ultraflex and both uncovered and covered Wallstents were damaged at both power settings (40 W and 80 W) and F(I)O(2) (0.21 and 0.40) levels, with a trend towards earlier damage using higher F(I)O(2) and power.

CONCLUSION

Working within the parameters identified in this study (power 40 W, F(I)O(2) 0.21, APC flow-rate 0.8 L/min), APC is a safe method for tissue devitalization and destruction and avoids the risk of airway stent ignition, especially if short bursts of APC are employed. The safety limits identified using an F(i)O(2) of 0.4, however, are also important because some patients undergoing resection may require oxygen therapy.

Advances in the management of endobronchial lung malignancies

The effective palliation of endobronchial malignancies often involves the use of multiple modalities including surgery, external beam radiation, chemotherapy, or a variety of interventional bronchoscopic techniques. The authors discuss in detail recent advances in interventional bronchoscopy that enhance local tumor control. An integrated and individualized approach to the use of these complementary modalities can provide rapid palliation and may improve survival in a subset of patients.

Anaesthesia and tracheobronchial stenting for central airway obstruction in adults

In the last decade, stents suitable for the management of tracheobronchial stenoses and obstruction have evolved from bulky prostheses requiring tracheal resection to small devices that are self-expanding and can be inserted using fibreoptic techniques. The experience base for this review is more than 100 patients between 1989 and 2001 who have been anaesthetized for stent insertion. Early cases required rigid bronchoscopy for the routine of insertion. Anaesthetic techniques have evolved from those that were designed and developed for laser surgery in the central airways. The advent of modern devices now extends the variety of anaesthetic management techniques that can be used. But the original one, based on the requirement for use of a rigid bronchoscope, is best for dealing with complications and extracting problem stents. The most frequent complication of the processes of stent insertion has been respiratory failure because of carbon dioxide retention, consequent on obstruction with secretions in the area of the carina. The nature of central airway problems suggests that anaesthesia induction, management and teaching should not be founded on the conventional model-base of upper airway obstruction.

Airflow through the auxiliary line of the laser fiber prevents ignition of intra-airway fire during endoscopic laser surgery

BACKGROUND AND OBJECTIVES

Ignition accidents during bronchoscopic laser irradiation have occasionally been reported, but the mechanisms responsible for the ignition accidents are not fully understood. We examined causative factors including ignition site, oxygen concentration, and role of airflow through the laser fiber.

STUDY DESIGN/MATERIALS AND METHODS

Porcine muscle tissue was placed in a bottle and irradiated by laser under various conditions. Also, a piece of porcine muscle was wedged in a main bronchus of the isolated porcine lungs and irradiated by laser in the same way.

RESULTS

Flashing occurred on the tissue exposed to the laser, and this flashing reached the ignition when the oxygen concentration was above 30%. Increasing airflow through the laser fiber prevented the ignition even at an oxygen concentration at 100%.

CONCLUSIONS

In laser irradiation, the tissue exposed to the laser can be the ignition site of fire. Increasing airflow through the laser fiber was an effective technique to prevent airway fire.

Nd-YAG laser damage to metal and silicone endobronchial stents: delineation of margins of safety using an in vitro experimental model

STUDY OBJECTIVE

To identify margins of safety within which bronchoscopic Nd-YAG laser resection can be performed without damaging indwelling tracheobronchial stents.

DESIGN

Experimental in vitro study simulating a patient-care environment.

METHODS

Uncovered and covered metal Wallstent (Schneider; Zurich, Switzerland) and Dumon (Bryan Corporation; Woburn, MA) silicone stents were deployed in the tracheobronchial tree of a ventilated and oxygenated (fraction of inspired oxygen, 40%) heart-lung block of a dead canine. Rigid bronchoscopic Nd-YAG (1,064 nm) laser procedures were performed in order to deliver laser energy using fiber-to-target distances of 10 mm and 20 mm, and noncontact, continuous-mode, 1-s pulses at power settings of 10 W, 30 W, and 40 W. The major outcome measure was laser-induced stent damage, defined as discoloration, ignition, or breakage. This was assessed using six power densities: 75 W/cm(2), 172 W/cm(2), 225 W/cm(2), 300 W/cm(2), 518 W/cm(2), and 690 W/cm(2).

RESULTS

The uncovered Wallstent and the silicone stent remained intact at power densities of 75 W/cm(2) (10 W, 20 mm) and 172 W/cm(2) (10 W, 10 mm), but were damaged at power densities > 225 W/cm(2) (30 W, 20 mm). The covered Wallstent was damaged at all power densities tested.

CONCLUSION

Uncovered Wallstent and silicone stents are not damaged when Nd-YAG laser energy is delivered using power densities < or = 72 W/cm(2) (10 W, 10 mm). Covered Wallstents, however, had a high likelihood of ignition at all power densities studied.