By placing an endotracheal tube in the oesophagus a patient loses their ability to exchange gases sufficiently. This error can happen at rates as high as 1/18, and will not cause long lasting medical complications if resolved within a few seconds. It is when this error goes unnoticed and there is a delay in diagnoses so that hypoxic and hypercapnic damage sets in. If correctly diagnosed, the tracheal tube can be moved from the oesophagus to the trachea; oxygen can be replenished in the body and carbon dioxide removed. Performing Diffuse reflectance of tracheal tissues with a broadband white light source reveals a characteristic in the reflected spectrum that is not present in oesophageal tissues. By utilising the spectral characteristic of OHb the goal is to be able to give clinicians real time feedback on whether the tracheal tube has been correctly placed into the trachea.