Interrupter airway and tissue resistance: errors caused by valve properties and respiratory system compliance

The interrupter technique is used to determine airway and tissue resistance . Their accuracy is influenced by the technical properties of the interrupt er device and the compliance of the respiratory system. We investigated the influence of valve characteristics and respiratory system compliance on th e accuracy of determining airway and tissue resistance by means of a comput er simulation. With decreasing compliance we found increasing errors in bot h airway and tissue resistance determination of up to 34 and 71%, respectiv ely. On this basis we developed a new occlusion valve, with special emphasi s on rapid closing time and tightness in the closed state to improve the ac curacy of resistance determination. The newly developed occlusion device gr eatly improves the accuracy of airway and tissue resistance determination. We conclude that respiratory system compliance is a limiting factor for the accuracy of the interrupter technique. To apply the interrupter technique in patients with extremely low respiratory system compliances, we need soph isticated technical devices.