Novel air leak test using surfactant for lung surgery.

BACKGROUND: Prolonged air leak is the most common complication after pulmonary resection surgery. Water submersion test (WST) has been used to check for air leak. However, it is cumbersome under the circumstances of video-assisted thoracic surgery (VATS). This study aimed to devise a new air leak detection method that is suitable for the VATS.
METHODS: We decided to utilize the properties of the surfactants to overcome the disadvantages of WST. To find the optimal surfactant, ex-vivo porcine lung experiments were prepared with a custom-made large glass vessel mimicking a human thoracic cavity. A fresh lung was put inside the glass vessel and connected with the ventilator. We made a needle injury on the lung surface and dropped various kinds of liquid surfactants to create air bubbles during the lung ventilation. The appearances of bubbles were recorded through 5mm thoracoscope.
RESULTS: Considering the bubble forming ability, Pluronic F-127 solution (PF127), a well-known non-toxic and non-ionic colorless surfactant, was chosen as candidate substance. To find the optimal condition, various concentrations of PF127 (30%, 25%, 20%, 15%, 10%) were tested. Greater than 20% concentration of PF127 were not feasible due to its high viscosity; the bubbles kept increasing in size without popping and blocked the thoracoscopic vision. The 10% PF127 did not form any bubbles. On the contrary, the 15% PF127 formed bubbles that are 1-2 cm in size with dynamic movement allowing for clear visibility of the air leak point. We finally made a green colored 15% PF127 by mixing an indocyanine green to increase its visibility. All of the components in the solution are FDA approved and permissible to be used in the human body.
CONCLUSIONS: Our bubble solution can easily detect the air leak even in small quantities and is expected to be useful in VATS with limited vision. However, in order for its full-scale clinical use, its safety in the human body must be verified.