A novel connection device, and method for its use, for connecting a volume displacement detection device and a gas composition detection device in line with an intubation tube is disclosed. The connection device allows a user to combine two systems commonly employed by medical personnel to assess the location of an intubation tube placed into a patient. The two systems have alternate means of assessing the location of an intubation tube in a patient and therefore, when combined into a single unit via the connection device, improve the accuracy of placing a tube in a desired location while reducing or eliminating complications associated with misplacement. A kit comprising components that may be assembled to provide a device for assessing the proper placement of an intubation tube in a patient is also disclosed. The kit may be used in any environment, but is particularly well suited for emergency, pre-hospital settings requiring intubation where quick assembly of the components is essential.