Inspiratory lung impedance in COPD: Effects of peep and immediate impact of lung volume reduction surgery

David W. Kaczka*, Edward P. Ingenito, Simon C. Body, Sabine E. Duffy, Steven J. Mentzer, Malcolm M. DeCamp, Kenneth R. Lutchen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Inspiratory lung impedance in COPD: effects of PEEP and immediate impact of lung volume reduction surgery. J Appl Physiol 90: 1833-1841, 2001. - Frequency-dependent characteristics of lung resistance (RL) and elastance (EL) are sensitive to different patterns of airway obstruction. We used an enhanced ventilator waveform (EVW) to measure inspiratory RL and EL spectra in ventilated patients during thoracic surgery. The EVW delivers an inspiratory flow waveform with enhanced spectral excitation from 0.156 to 8.1 Hz. Estimates of the coefficients in a trigonometric approximation of the EVW flow and transpulmonary pressure inspirations yielded inspiratory RL and EL spectra. We applied the EVW in a group with mild obstruction undergoing various thoracoscopic procedures (n = 6), and another group with severe chronic obstructive pulmonary disease undergoing lung volume reduction surgery (n = 8). Measurements were made at positive end-expiratory pressure (PEEP) of 0, 3, and 6 cmH2O. Inspiratory RL was similar in both groups despite marked differences in spirometry. The chronic obstructive pulmonary disease patients demonstrated a pronounced frequency-dependent increase in inspiratory EL consistent with severe heterogeneous peripheral airway obstruction. PEEP appears to have beneficial effects by reducing peripheral airway resistance. Lung volume reduction surgery resulted in increased inspiratory RL and EL at all frequencies and PEEPs, possibly due to loss of diseased lung tissue, pulmonary edema, increased mechanical heterogeneity, and/or an improvement in airway tethering.

Original languageEnglish (US)
Pages (from-to)1833-1841
Number of pages9
JournalJournal of applied physiology
Issue number5
StatePublished - 2001


  • Chronic obstructive pulmonary disease
  • Enhanced ventilator waveform
  • Inspiratory lung elastance
  • Inspiratory lung resistance
  • Positive end-expiratory pressure

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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