Lung elastance and transpulmonary pressure can be determined without using oesophageal pressure measurements

Acta Anaesthesiol Scand. 2012 Jul;56(6):738-47. doi: 10.1111/j.1399-6576.2012.02696.x. Epub 2012 Apr 23.

Abstract

Introduction: The aim of the present study was to demonstrate that lung elastance and transpulmonary pressure can be determined without using oesophageal pressure measurements.

Methods: Studies were performed on 13 anesthetized and sacrificed ex vivo pigs. Tracheal and oesophageal pressures were measured and changes in end-expiratory lung volume (ΔEELV) determined by spirometry as the cumulative inspiratory-expiratory tidal volume difference. Studies were performed with different end-expiratory pressure steps [change in end-expiratory airway pressure (ΔPEEP)], body positions and with abdominal load.

Results: A PEEP increase results in a multi-breath build-up of end-expiratory lung volume. End-expiratory oesophageal pressure did not increase further after the first expiration, constituting half of the change in ΔEELV following a PEEP increase, even though end-expiratory volume continued to increase. This resulted in a successive left shift of the chest wall pressure-volume curve. Even at a PEEP of 12 cmH(2) O did the end-expiratory oesophageal (pleural) pressure remain negative.

Conclusions: A PEEP increase resulted in a less than expected increase in end-expiratory oesophageal pressure, indicating that the chest wall and abdomen gradually can accommodate changes in lung volume. The rib cage end-expiratory spring-out force stretches the diaphragm and prevents the lung from being compressed by abdominal pressure. The increase in transpulmonary pressure following a PEEP increase was closely related to the increase in PEEP, indicating that lung compliance can be calculated from the ratio of the change in end-expiratory lung volume and the change in PEEP, ΔEELV/ΔPEEP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abdomen / physiology
  • Airway Resistance
  • Anesthesia
  • Animals
  • Diaphragm / physiology
  • Elasticity
  • Electric Impedance
  • Esophagus / physiology*
  • Head-Down Tilt
  • Lung / anatomy & histology
  • Lung / physiology*
  • Lung Compliance / physiology
  • Lung Volume Measurements
  • Peak Expiratory Flow Rate
  • Positive-Pressure Respiration
  • Pressure
  • Spirometry
  • Swine
  • Thoracic Wall / anatomy & histology
  • Thoracic Wall / physiology
  • Tidal Volume / physiology
  • Tomography
  • Trachea / physiology