Plethysmography and the non-uniform lung--the measurement of the instantaneous energy-based airway resistance--a new concept.
The concept of work and energy is defined and the relation between airway resistance and the work required to move the air through the airways, in the case of spatially uniform lung pressure, is described. When the alveolar pressure is spatially non-uniform, the plethysmograph measures an average pressure (volume weighted). This measured average pressure is not zero at zero flow and consequently does not enable the simple determination of an airway resistance as in the case of the uniform lung. The measured mean alveolar pressure has the characteristics of a pressure measured across both a resistive pathway and an elastic membrane. This "elastic" component of the pressure can be simply subtracted (method of Mead and Whittenberger) and the consequently obtained airway resistance can be compared to that resistance which is directly based on the energy requirements. This procedure has been used in 59 individual representative modelled cases. On the whole, good agreement with the energy-based resistances has been obtained.
D000403:Airway Resistance; D006801:Humans; D008168:Lung / Q000503:physiopathology; D008170:Lung Compliance; D008171:Lung Diseases / Q000503:physiopathology*; D008433:Mathematics; D008953:Models, Anatomic; D010993:Plethysmography, Whole Body / Q000379:methods*; D012123:Pulmonary Ventilation