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Updated: Oct 7, 2026

Conducting Respiratory Oscillometry in an Outpatient Setting
Published on: April 8, 2022
Effect of imposed inflation time on respiratory frequency and hyperinflation in patients with chronic obstructive
1Division of Pulmonary and Critical Care Medicine, Edward Hines, Jr. Veterans Administration Hospital, 111N, 5th Avenue and Roosevelt Road, Hines, IL 60141, USA. flaghi@lumc.edu
Abstract:
Decreases in ventilator inflation time (TI,vent) can cause tachypnea, probably as a response to lung inflation. The response may differ in chronic obstructive pulmonary disease (COPD) because time-constant inhomogeneities could foster overdistention of some lung units during early inflation, causing neural inspiratory time to be shorter than in healthy subjects. We tested the hypothesis that a decrease in TI,vent causes tachypnea, prolongation of exhalation, and a decrease in intrinsic positive end-expiratory pressure (PEEP(i)). Ten patients with stable COPD received assist-control ventilation through a mouthpiece. Decreases in TI,vent, achieved through increases in flow from 30 to 90 L/min, increased frequency, from 16.1 +/- 1.0 (SE) to 20.8 +/- 1.5 breaths/min (p < 0.001), time for exhalation, from 2.1 +/- 0.2 to 2.3 +/- 0.2 s (p < 0.025), and decreased PEEP(i), from 7.0 +/- 1.3 to 6.4 +/- 1.1 cm H(2)O (p < 0.01). Decreases in TI,vent, achieved by decreasing inspiratory pause from 2 to 0 s, increased frequency, from 12.9 +/- 0.8 to 18.1 +/- 1.6 breaths/min (p < 0.001), time for exhalation, from 2.0 +/- 0.2 to 2.6 +/- 0.3 s (p < 0.001), and decreased PEEP(i), from 6.4 +/- 1.1 to 5.5 +/- 0.9 cm H(2)O (p < 0.01). In both experiments, decreases in TI,vent reduced inspiratory effort (p < 0.01). In conclusion, strategies to reduce TI,vent in patients with COPD caused tachypnea, yet prolonged the time for exhalation with consequent decrease in PEEP(i).
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