Cardiopulmonary resuscitation being provided to a subject is monitored. An enhanced measurement of the effectiveness of the cardiopulmonary resuscitation received by the subject is determined by correlating chest compressions with changes in movement and/or composition of gas at or near the airway of the subject. For example one or more therapy parameters may be measured with an enhanced accuracy and/or precision and/or one or more therapy parameters not monitored in conventional cardiopulmonary resuscitation monitoring systems may be measured. Fig.1
