Spray cryotherapy is effective for bronchoscopic, endoscopic and open ablation of thoracic tissues

Abstract

Objectives: Spray cryotherapy (SCT) delivers a liquid nitrogen spray via a catheter to produce cellular death. This study seeks to determine the histological changes after bronchoscopic, endoscopic and open SCT on tissues in the thoracic cavity.

Methods: Yorkshire pigs underwent flexible bronchoscopy, endoscopy and thoracotomy for SCT of the airway, oesophagus and other intrathoracic structures, respectively. Variations in the duration and number of spray cycles for the same dosimetry were compared.

Results: Bronchoscopic SCT of the airway resulted in cellular death up to the cartilage layer. Endoscopic SCT of the oesophagus led to cell death up to the adventitial layer. Tissue necrosis was severe in the lung, of full thickness in the pleura, but very superficial in the great vessels. The extracellular matrix (ECM) of treated tissues remained well-preserved. Having shorter but more cycles of SCT decreased the depth of the cellular necrosis. One pig developed ventricular fibrillation during the surgery and expired.

Conclusions: SCT causes reproducible tissue injury with the preserved ECM of most tissues within the thoracic cavity, making it enticing for ablation around vital structures like the great vessels with a decreased long-term risk. Further study is warranted to investigate the adverse events during SCT.

Figures

Figure 1:

Bronchoscopic SCT. A bronchoscopic view of liquid nitrogen being sprayed onto the airway.

Figure 2:

The effects of bronchoscopic SCT of the airway. (a) Normal mucosa and submucosa. (b) After bronchoscopic SCT, the epithelium was sloughed off and the cells were necrotic. (c) Normal cartilage. (d) After ablation, cell death extended to the cartilage as depicted by pyknotic nuclei in the chondrocytes. Scale bar represents 50 µm in (a) and (b), and 20 µm in (c) and (d). H&E stain.

Figure 3:

The depth of cell death with variations in the dosimetry. (a) In spite of maintaining the same total SCT time of 30 s, a longer duration of a spray cycle led to a greater depth of cell death in the airway and lung. (b) Despite the same total SCT time of 60 s, a longer duration of a spray cycle led to a greater depth of cell death in the oesophagus.

Figure 4:

The effects of endoscopic SCT of the oesophagus. (a) Normal mucosa. (b) After endoscopic SCT, there was necrosis throughout the epithelium and lamina propria with mild haemorrhage. Scale bar represents 100 µm. H&E stain.