Abstract: An apparatus for monitoring the respiration of a subject, the apparatus comprises means for detecting the concentration of each of oxygen, carbon dioxide and nitric oxide in an inspired and/or exhaled gaseous stream of a subject; and a display for displaying the concentration of each of oxygen, carbon dioxide and nitric oxide. A method for monitoring the respiration of a subject comprises analysing the composition of the inspired and/or exhaled gas of the subject and determining the concentration of carbon dioxide, oxygen and nitric oxide in the gas; and displaying the results of the analysis on a display to provide an indication of the respiratory state of the subject. A method of determining the extent of resuscitation of a patient comprises measuring the concentration of carbon dioxide, oxygen and nitric oxide in the inspired gas stream and/or exhaled gas stream of the subject.