The carbon dioxide (CO2) laser emits light at a wavelength in the infra-red region (10,600) which is strongly absorbed by water and hence by soft tissue. It causes vaporisation of the tissues but its penetration is very shallow, in the region of 1mm. It can be used for highly localised tissue removal through vaporisation as well as a cutting tool. However, it has a poor coagulative effect compared to other lasers and it is not as haemostatic. It will seal blood vessels only up to 1mm in diameter. Since the laser energy is not deeply conducted to surrounding tissues it produces controlled tissue destruction with minimal surrounding oedema. However, the carbon dioxide laser beam cannot be transmitted through a flexible optic fibre and must be develivered via a cumbersome articulated mirror system. It is ideal for treating laryngeal lesions but has only limited application in the trachea.

The neodymium yttrium aluminum garnet (Nd:YAG) laser produces a wavelength of light in the 1064 infra-red region. It is less strongly absorbed by tissue than carbon dioxide laser beam and is only weakly absorbed by water. Thus, it has a better tissue penetration up to a depth of 5 mm. It is absorbed by pigments and is therefore good for coagulation. There is significant scattering of the beam in tissue so that a much larger volume is effected. It is good for cutting but it is difficult to vaporise tissue. The laser has a significant advantage in being able to be delivered by optical fibre.

The carbon dioxide laser is an excellent tool for the treatment of the pharygeal and subglottic lesions. However, the Nd: YAG is the preferred laser for most tracheobronchial applications. It can function below the larynx, offer excellent haemostasis, and can be delivered close to the lesion by flexible optical fibre.

The Nd: YAG laser can be used for the treatment of both malignant and benign lesions of the tracheobronchial tract. Its main application is for the palliation of airway obstruction resulting from malignant tracheobronchial tumours or from carcinoid tumours. It has also been used to treat haemoptysis resulting from a vascular endobronchial tumour. It is also used to treat persistent cough.