Determination Of Location Of Bacterial Load In The Lungs

A method for determining the presence or absence and location of a bacterial load in the respiratory system of a subject comprising:

• a. administering to the subject, an effective amount of a 13C-isotopically-labeled compound that produces 13CO2 upon bacterial metabolism;
• b. collecting a plurality of samples of exhaled breath from the subject;
• i. at least one of said samples comprising breath from the upper respiratory tract of the subject;
• and
• ii. at least one of said samples comprising breath from the lower respiratory tract of the subject;
• c. conducting at least some of the samples to a sample chamber of a detection apparatus;
• d. evaluating the isotopic ratio of 13CO2 to 12CO2 present in each of the at least some samples;
• and
• e. relating the isotopic ratios thus ascertained to the location in the respiratory system from which said samples conducted to the sample chamber were collected.