ABSTRACT
The problem of how well the respiratory system functions is mainly approached through measurements of gas flow, gas pressure and gas composition and their derivatives.
Respiratory measurements are an important source of information in the lung function laboratory, where a suite of tests is available to test the various properties of a patient’s respiratory system. These measurements provide a single static picture of the patient’s condition, which is representative only if the properties of the respiratory system do not change (much) over time-i.e., if the condition is chronic. Respiratory measurements are also important in a critical care environment, where the patient’s condition, which is critical and may therefore change from moment to moment, must be monitored continuously. These tests have a different character. Whereas in the lung function laboratory we can often count on the patient’s cooperation, this is usually impossible in critically ill patients, who may have damaged lungs and who may be unconscious or otherwise unable to cooperate. For this reason the range of tests is less extensive, and also the reason that the tests must be performed (semi)-continuously.
