How to Figure Ventilator Tubing Compliance

Without breathing, and the consequent inhalation of oxygen and exhalation of carbon dioxide, life would quickly cease. Medical facilities are often forced to assist this process through the use of ventilator tubes. It is crucial that the air pressure used during this process be correct. One of the factors in this is the compliance of the lungs themselves -- the elasticity of the lungs and their resistance to expansion. Lungs with higher compliance require lower pressures, while less complaint lungs need higher pressures. The process for calculating compliance is quite straightforward.

Instructions

• 1

  Check the gauges, digital display or screen on the ventilator to read the indicated intrapleural pressure and the volume when the patient breathes. Note the intrapleural pressure readings both before respiration and afterward. The volume should be constant, while the intrapleural pressure should change.

• 2

  Subtract the intrapleural pressure before respiration from the intrapleural pressure after respiration. This gives you the change in pleural pressure.

• 3

  Divide the change in pleural pressure number by the change in volume. The resulting number is the compliance. This concept is expressed by the formula ΔV/ΔP. For example, assume a patient inhales .4L of air, with an intrapleural pressure before respiration of -4 and after respiration of -10. The equation would be .4L/(-4 -(-10) = .066L, meaning the compliance is .066L.