respiratory system measurement ventilation measurement 2011-09-21T11:16:38Z CMO:0000114 This is any measurable or observable characteristic related to the total volume of gas inspired or expired. Ventilation rate is expressed as the volume of gas entering or leaving the lungs in a given amount of time and can be calculated by multiplying the volume of gas, either inhaled or exhaled, during a breath (the tidal volume) by the breathing rate. clinical_measurement_ontology mshimoyama