Series dead space volume assessed as the mean value of a distribution function

  • Gunther Wolff
  • Josef X. Brunner
Article

Abstract

Series dead space (VdS) is assumed to be represented by that volume exhaled until alveolar gas is observed. Phase II of the single breath CO2-diagram contains the (flow, concentration and sequence weighted) distribution off all stationary interfaces (SI) expired before phase III. We describe a new method to estimate the mean value of VdS based on the differentiation of phase II. This approximation of VdS is called the ‘Pre Interface Expirate’ (PIE) and is compared in this study with the integrative approach of Langley. Tidal volume (Vt) and PEEP were varied from 71 to 123% and from 0 to 6 cmH2O respectively.

The estimation of VdS by differentiation of phase II (PIE) shows excellent reproducibility and depends only on phase II — not on phase III and IV as does VdS-Langley. PIE does not depend on Vt and PEEP per se but reflects the distension of convective airways due to elevated end-inspiratory airway pressure.

Our results confirm the predictions of Paiva's model calculations in that the size of VdS is determined by the distension of airways rather than by the altered position of the SI.

Keywords

Pre-Interface-Expirate PIE Stationary Interface single breath CO2 diagram 

References

  1. 1.
    Cumming G, Horsfield K, Preston SB: Diffusion equilibrium of the lungs examined by nodal analysis. Respir Physiol 12: 329–345, 1971.PubMedCrossRefGoogle Scholar
  2. 2.
    Paiva M: Computation of the boundary conditions for diffusion in the human lung. Comput Biomed Res 5: 585–595, 1972.PubMedCrossRefGoogle Scholar
  3. 3.
    Horsfield K, Cumming G: Functional consequences of airway morphology. J Appl Physiol 24 (3): 384–390, 1968.PubMedGoogle Scholar
  4. 4.
    Olsson SG, Fletcher R, Jonson B, Nordstroem L, Prakash O: Clinical studies of gas exchange during ventilatory support — a method using the Siemens-Elema CO2 analyzer. Br J Anaesth 52: 491–498, 1980.PubMedCrossRefGoogle Scholar
  5. 5.
    Langley F, Even P, Duroux P, Nocolas RL, Cumming G: Ventilatory consequences of unilateral pulmonary artery occlusion. Les Colloques de l'Institut National de la Sante et de la Recherche Medicale 51: 209–214, 1975.Google Scholar
  6. 6.
    Fletcher R, Jonson B, Cumming G, Brew J: The concept of deadspace with special reference to the single breath test for carbon dioxide. Br J Anaesth 53: 77–94, 1981.PubMedCrossRefGoogle Scholar
  7. 7.
    Fletcher R, Jonson B: Deadspace and the single breath test for carbon dioxide during anaesthesia and artificial ventilation. Br J Anaesth 56: 109–119, 1984.PubMedCrossRefGoogle Scholar
  8. 8.
    Brunner J, Wolff G: Reliable estimation of series dead space in ventilated patients. Clin Physiol: in press, 1984.Google Scholar
  9. 9.
    Brunner J, Langenstein H, Wolff G: Direct accurate gas flow measurement in the patient: Compensation for unavoidable error. Med Prog Technol 9: 233–238, 1983.PubMedGoogle Scholar
  10. 10.
    Brunner J, Wolff G, Langenstein H, Cumming G: Reliable detection of inspiration and expiration by computer. J. Appl Physiol: in press, 1984.Google Scholar
  11. 11.
    Paiva M: Model analysis of inert gas mixing in the lung. Bull Europ Physiopath Resp 18: 189–201, 1982.Google Scholar

Copyright information

© Martinus Nijhoff Publishers 1984

Authors and Affiliations

  • Gunther Wolff
    • 1
  • Josef X. Brunner
    • 1
  1. 1.Section for Clinical Physiology, Division for Cardio-Thoracic SurgeryUniversity of BaselSwitzerland

Personalised recommendations