Contribution of Opening and Closing of Lung Units to Lung Hysteresis

Details

• Personal Author:
  Cheng WC ; DeLong DS ; Franz GN ; Frazer DG ; Petsonk, Edward L.
• Description:
  The recruitment and derecruitment of lung units is one explanation of the hysteresis observed in an excised lung during inflation and deflation. A simplified model has been proposed in which the recruitment-derecruitment process is a function of end-expiratory pressure (Frazer, D.G., K.C. Weber and G.N. Franz, Respir. Physiol. 61: 277-288, 1985). The object of this study was to test this model with three experimental procedures. During the first set of experiments, progressively larger pressure-volume (PL-VL) loops were recorded with end-expiratory pressure held at either -5 cmH(2)O, where all lung units are assumed to be closed, or +5 cmH(2)O, where all recruited lung units are assumed to be open. In the first case hysteresis is maximal, in the second, minimal. The difference in hysteresis is presumed to arise from the recruitment-derecruitment process. In the second set of experiments, excised lungs are slowly inflated and then deflated at a constant rate while constant-amplitude sinusoidal volume oscillations are superimposed. The end-expiratory pressure of the superimposed loops gradually rose as the lung was inflated and fell as the lung was deflated. Hysteresis was minimal when end-expiratory pressure was above 4+/-1 cmH(2)O even as peak-to-peak loop pressure greatly varied. This supports the notion of an end-expiratory pressure dependent mechanism of recruitment/derecruitment. During the third set of experiments lungs were inflated to either 50%, 75%, or 100% TLC. Volumes of air were then withdrawn and replaced so that the initial volume was restored in sinusoidal fashion as the amplitude of the volume excursions increased. For PL-VL loops with end-expiratory pressures between +4 and -2 cmH(2)O, pressure amplitudes rose and the hysteresis index (loop area/tidal volume) increased, regardless of the initial lung volume. These results are consistent with the previously described model of Frazer et al. (1985) which assumed that PL-VL curves can be divided into an 'opening' region, an 'open' region and a 'closing' region and that the demarcation of these regions depends on transpulmonary pressure, specifically end-expiratory pressure, and to a much lesser degree on lung volume. [Description provided by NIOSH]
• Subjects:
  Laboratories Lung Lung Diseases Occupational Health Respiratory Function Tests Respiratory System Respiratory Tract Diseases Safety
• Keywords:
  Author Keywords: Airways Closure Derecruitment Excised Lung Hysteresis Inflation Laboratory-animals Laboratory-testing Lung-disorders Lung-function Lung Inflation Lung Volume Mechanics Of Breathing Pulmonary-function Pulmonary-function-tests Pulmonary-system-disorders Recruitment Respiratory-function-tests Respiratory-gas-transport Respiratory-system-disorders

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• ISSN:
  0034-5687
• Document Type:
  Text
• Genre:
  Journal Article
• Place as Subject:
  OSHA Region 3 ; West Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DRDS - Division of Respiratory Disease Studies
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  205-215
• Volume:
  127
• Issue:
  2
• NIOSHTIC Number:
  nn:20034946
• Citation:
  Respir Physiol 1995 Dec; 102(2-3):205-215
• Contact Point Address:
  D.G. Frazer, Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, 944 Chestnut Ridge Road, Morgantown, WV26506, USA
• Federal Fiscal Year:
  1996
• Peer Reviewed:
  True
• Source Full Name:
  Respiration Physiology
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:73c711eed4ea664b05de5ac2dc2f21d60b6f195807edf8556fcddcea4f226588f747054570a3272e3f61a0312800cba05818f0487dd4062af9fe53255d03e43e
• Download URL:
  https://stacks.cdc.gov/view/cdc/186959/cdc_186959_DS1.pdf
• File Type:
  [PDF - 830.52 KB ]