Variability of plethysmographic measurements of airways resistance in man.

Abstract

In a statistically planned study, two observers made measurements of airways conductance (Gaw) and lung volume (Vtg) on a group of 16 men on 8 days, using a body plethysmograph. It was found that despite large individual variations in the Gaw/Vtg relationships, Gaw could be standardized for Vtg changes by using the index specific conductance SGaw (Gaw/Vtg) which assumes that Gaw is directly proportional to Vtg. A small consistent significant difference in all the measurements was found between the observers but these did not vary significantly during the day between 8.30 AM and 4.30 PM, or during the week between Monday and Friday. The order in which the men were seen was unimportant and there was no significant training effect, i.e., any change in SGaw as the subjects became more experienced.