Pulmonary Medicine

Interventional Bronchoscopy: Argon Plasma Coagulation (APC)

General description of procedure, equipment, technique

Argon Plasma Coagulation (APC)

Initially defined in 1995 and subsequently described in European Respiratory Society (ERS) and American Thoracic Society (ATS) guidelines, interventional pulmonology is "the art and science of medicine as related to the performance of diagnostic and invasive therapeutic procedures that require additional training and expertise beyond that required in a standard pulmonary medicine training program." Clinical entities encompassed within the discipline include complex airway management, benign and malignant central airway obstruction, pleural diseases, and plumonary vascular procedures.

Diagnostic and therapeutic procedures pertaining to these areas include rigid bronchoscopy, transbronchial needle aspiration, autofluorescence bronchoscopy, endobronchial ultrasound, transthoracic needle aspiration and biopsy, laser bronchoscopy, endobronchial electrosurgery, argon-plasma coagulation, cryotherapy, airway stent insertion, balloon bronchoplasty and dilatation techniques, endobronchial radiation (brachytherapy), photodynamic therapy, percutaneous dilatational tracheotomy, transtracheal oxygen catheter insertion, medical thoracoscopy, and image-guided thoracic interventions. This presentation focuses on argon plasma coagulation (APC).

Argon plasma coagulation (APC) is an electrosurgical technique similar to laser or electrocautery. PC is used during bronchoscopic procedures to debulk malignant airway tumors, control hemoptysis, remove granulation tissue from stents or anastomoses, and treat a variety of benign disorders.

Indications and patient selection

The indications for APC are similar to those for laser therapy and electrocautery.

Contraindications

The contraindications for APC are similar to those for laser therapy and electrocautery.

Details of how the procedure is performed

Similar to electrocautery, a grounding pad is placed on the patient's back. Typical settings include a power of 30 Watts and an argon flow rate of 0.8 to 1 L/min. The argon flow rate determines the length of the flame. The probe tip is positioned several centimeters beyond the bronchoscope's tip to ensure that the bronchoscope will not be burned. The probe tip is placed within 1 cm of the target lesion; the electric current will not be conducted if the probe is farther than 1 cm from the target lesion.

As argon gas is expelled, a high-voltage electric current passing along the probe contacts the gas, ionizing it and conducting a monopolar current to the target lesion. The current is applied to the surface in one- to three-second bursts. The tissue effect is similar to that seen with electrocautery.

In the process of debulking an endobronchial lesion, eschar is first formed with the application of APC and then removed using a forceps or a cryotherapy probe. APC is then applied to the underlying fresh tissue. This process is repeated until the tumor is removed.

Interpretation of results

Not applicable

Performance characteristics of the procedure (applies only to diagnostic procedures)

Not applicable

Outcomes (applies only to therapeutic procedures)

In a prospective cohort study of 364 patients who underwent APC (482 procedures), a success rate of 67 percent was reported, where success was defined as hemostasis or full or partial airway recanalization. Rigid bronchoscopy was used in 90 percent of the interventions.

In a retrospective cohort study of sixty patients who underwent APC (seventy procedures), treatment was immediately successful in fifty-nine patients; treatment success was defined as resolution of hemoptysis or decreased airway obstruction. (All patients had either hemoptysis or airway obstruction.) Hemoptysis did not recur over a mean follow-up of ninety-seven days, and improvement in dyspnea persisted over a mean follow-up of fifty-three days. A similar study of forty-seven patients reported a success rate of 92 percent, which was maintained over a mean follow-up of 6.7 months. However, an average of more than three sessions per patient was required to achieve this result.

Alternative and/or additional procedures to consider

Alternative treatment modalities to APC include ND:YAG laser therapy, electrocautery, and cryotherapy.

Complications and their management

Complications of APC, while infrequent (less than 1% of procedures), include airway burn and airway perforation, which can cause pneumomediastinum, subcutaneous emphysema, and pneumothorax. Gas embolism has also been described in a case series, leading to three cases of cardiovascular collapse and one case of death. Such a complication reflects lack of experience by the operator. A burned bronchoscope has also been reported.

Similar to laser and electrocautery, limiting the inspired oxygen concentration, the d power (less than 40 watts), and the application time (less than five seconds) probably minimizes the risk of airway fire, as does keeping the probe tip several centimeters away from any combustible material.

What’s the evidence?

Colt, HG. "Bronchoscopic resection of wall stent-associated granulation tissue using argon plasma coagulation". J Bronchol. vol. 5. 1998. pp. 209.

Description of the use of APC in removal of granulation tissue arising from insertion of metal stents.

Crosta, C, Spaggiari, L, De Stefano, A. "Endoscopic argon plasma coagulation for palliative treatment of malignant airway obstructions: early results in 47 cases". Lung Cancer. vol. 33. 2001. pp. 75.

Early report on the use of APC in lung cancer palliation.

Grund, KE, Storek, D, Farin, G. "Endoscopic argon plasma coagulation (APC) first clinical experiences in flexible endoscopy". Endosc Surg Allied Technol. vol. 2. 1994. pp. 42.

Early description of the use of APC in conjunction with flexible endoscopy.

Morice, RC, Ece, T, Ece, F, Keus, L. "Endobronchial argon plasma coagulation for treatment of hemoptysis and neoplastic airway obstruction". Chest. vol. 119. 2001. pp. 781.

A classic paper addressing use of APC in lung cancer palliation.

Reddy, C, Majid, A, Michaud, G. "Gas embolism following bronchoscopic argon plasma coagulation: a case series". Chest. vol. 134. 2008. pp. 1066.

Report of a complication of use of APC.

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