1. Background

 

1.1 Lung Resection Surgery

Lung resection surgery is a method used to treat conditions such as lung cancer, pulmonary infections, and emphysema. During lung resection surgery, a surgeon removes all or part of a diseased or damaged lung. Two major types of lung resection surgery are wedge resection and lobectomy. In wedge resection, a small wedge-shaped portion containing the diseased cells along with some surrounding healthy tissue is removed. Lobectomy removes a whole lobe of lung and the connecting bronchus.

 

 

1.2 Endoscopic Stapler and Air Leak

To join together the lung tissue after a lung resection surgery, a surgical stapler is often used. When an endoscopic stapler is applied to lung or bronchial tissue, it places 4-6 staple lines from 6 mm to 45 mm long linearly and firmly along the stapler line. Then a built-in cutter slices the tissue down the middle of the staple line before the stapler is released.[2]

Due to the nature of the lung tissue and associated bronchi, the staple line cannot guarantee a perfect airtight seal. A less than perfect seal often causes problematic leaks that introduces air into the pleural space and causes infection after the surgery. Leaks often lead to prolonged postoperative hospital stays and severe problems like pneumonia, pneumothorax and bronchopleural fistula.[3]

 

 

1.3 VATS (Video-Assisted Thoracoscopic Surgery)

Traditional methods of lung resection involve performing a thoracotomy incision, which cuts through the frontal chest wall and exposes the chest cavity. Nowadays, the thoracotomy method is quickly being replaced by Video-Assisted Thoracoscopic Surgery (VATS), a minimally invasive procedure. During VATS, 3 to 4 incisions of 2 - 5 mm are made on the patient’s chest wall, as shown in Figure 2. A thoracoscope is placed through a 5-mm trocar, usually through the eighth intercostal space, to monitor the chest cavity.[4] Surgical equipment enters the chest cavity through the other incisions. VATS wedges take approximately 45 minutes and VATS lobectomies take up to 2 - 4 hours. Due to the limiting visual field of the thoracoscope, it is harder to detect a leak by visual observation.

 

 

1.4 Closure of air leaks

Leaks usually range from 0.1mm to 2 mm in diameter. Tiny air leaks that are detected during the surgery can be sealed with fibrin glue. As the size and amount of leaks increases, the surgeon may be forced to reseal and reinforce the staple line with materials like bovine pericardium. After the surgery, a chest tube connecting the patient’s chest cavity to a drainage system is applied. The system drains air and liquid out of the pleural cavity. Postoperative air leaks are observed as bubbles through this system. Sometimes these leaks stop spontaneously. Physicians like when this occurs since there is no noninvasive ways to close the leak. Majority of these air leaks stop after a few hours, but they can also take up to 3 days to close. Prolonged air leaks observed 4 - 10 days after the surgery are problematic. Patients are not sent back to the operation room unless severe problems like bronchopleural fistula develop.

 

2. Need for A Pulmonary Air Leak Detection System

Prolonged air leak (PAL) may introduce contaminated air to the sterile pleural cavity and lead to inflammation. Therefore, PAL causes severe problems including pneumothorax and broncopleural fistula, and has a death rated reported as high as 1 - 12%.[3] Patients with PAL are forced to prolong postoperative hospital stays and portable chest tube drainage. Most of the PALs are due to leaks on the staple line. As postoperative air leaks cannot be fixed with noninvasive procedures, it is desirable if the air leak is fixed in the operation room. Studies have shown that reinforcing the staple line with bovine pericardium and sealants reduces the risk of prolonged air leaks easily [6], yet reinforcing every point along the staple line would not be an efficient approach regarding time and cost. To accurately fix air leaks, the surgical teams need a safe and disposable device that can be easily applied to the surface of staple line, adhere to the tissue, immediately detect and report severity and location of the leak, be easily removed and leave no residue behind. Several methods have been developed to detect air leaks in patients with pneumothorax using imaging technologies. However, these methods are not applicable in a lung resection surgery. A novel device needs to be developed.