Reassessment of the interruption technique for measuring flow resistance in humans

Abstract

We have previously produced evidence that, in patients with obstructive lung disease, compliance of extrathoracic airways is responsible for lack of mouth-to-alveolar pressure equilibration during respiratory efforts against a closed airway. The flow interruption method for measuring respiratory resistance (Rint) is potentially faced with the same problems. We reassessed the merits of the interruption technique by rendering the extrathoracic airways more rigid and by using a rapid shutter. We measured airway resistance (Raw) with whole body plethysmography during panting (at 2 Hz) and Rint during quiet breathing. Rint and Raw were expressed as specific airway (sGaw) and interruptive conductance (sGint), respectively. In nine healthy subjects (cheeks supported), sGint (0.140 +/- 0.050 s-1.cmH2O-1) was lower (P less than 0.02) than sGaw (0.182 +/- 0.043 s-1.cmH2O-1). By contrast, in 12 patients with severe obstructive lung disease (forced expiratory volume in 1 s/vital capacity = 41.0 +/- 19.8%), sGint (0.058 +/- 0.012 s-1.cmH2O-1) was higher (P less than 0.05) than sGaw (0.047 +/- 0.007 s-1.cmH2O-1), when the cheeks were supported. When the mouth floor was also supported, average values of sGaw (0.048 +/- 0.008 s-1.cmH2O-1) and sGint (0.049 +/- 0.014 s-1.cmH2O-1) became similar. In conclusion, we confirm previous findings in healthy subjects of higher values of Rint, with respect to Raw, probably because of differences in glottis opening between quiet breathing and panting. In airflow obstruction, supporting both the cheeks and the mouth floor decreased sGint, which became similar to sGaw.

A portable device based on the interrupter technique to measure bronchodilator response in schoolchildren

“…It is noninvasive, requires minimum patient co-operation and its brevity and the absence of an oscillating column of air suggests that it may be generally better tolerated by young patients than the FOT. Responses such as glottic narrowing are unlikely to occur, because measurements are virtually imperceptible and are made during quiet breathing Recently, the physiological basis and clinical utility of the interrupter technique has been re-evaluated, with some promising results [14][15][16], and theoretical analysis by BATES et al [17] has validated the technique. Although upper airway compliance may lead to an underestimation of airway resistance [18], this can be minimized by supporting the cheeks and floor of the mouth.…”

Analysis of Properties of a Lung Mechanical Model During Artificial Ventilation Using Measurement Station

“…According to the described algorithm [15], interrupter resistances R int for each breath were calculated. Fig.…”

“…The IT is successfully used during respiratory system mechanics diagnostics [15]. Main advantages of the IT algorithm are its small invasiveness, minimal requirements regarding patient cooperation and also low implementation cost.…”

“…2. Estimation of parameter R int during artificial ventilation can be considered as a single task of inverse problem solution [17,15].…”

Detection of flow limitation during tidal breathing by the interruptor technique

“…All subjects, provided with noseclip, were studied in sitting position, supporting cheeks and mouth floor with their hands, in order to keep the distensibility of the extrathoracic airways as low as possible [9]. About 30 interruptions were performed, one interruption per expiration, randomly distributed over the expiratory phase.…”