Pulmonary pressure-flow relationships in the fetal lamb during in utero ventilation

D. L. Reid, Kent Thornburg

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Pressure-flow relationships in the ventilated lung have not been previously determined in undelivered fetal sheep. Therefore we studied 11 late-gestation chronically prepared fetal sheep during positive-pressure ventilation with different gas mixtures to determine the roles of mechanical distension and blood gas tensions on pressure-flow relationships in the lung. Ventilation with 3% O2-7% CO2 produced a substantial fall in pulmonary vascular resistance even though arterial blood gases were not changed. Increases in pulmonary arterial PO2 during ventilation were associated with falls in pulmonary vascular resistance beyond that measured during mechanical distension. Decreases in pulmonary arterial PCO2 and associated increases in pH were also associated with falls in pulmonary vascular resistance. Pulmonary blood flow ceased at a pulmonary arterial pressure that exceeded left atrial pressure, indicating that left atrial pressure does not represent the true downstream component of driving pressure through the pulmonary vascular bed. The slope of the driving pressure-flow relationship in the normal mature fetal lamb was therefore different from the ratio of pulmonary arterial pressure to pulmonary arterial flow. We conclude that mechanical ventilation, increased PO2 and decreased PCO2, and/or increased pH has an important influence on the fall in pulmonary vascular resistance elicited by positive pressure in utero ventilation of the fetal lamb and that the downstream driving pressure for pulmonary blood flow exceeds left atrial pressure.

Original languageEnglish (US)
Pages (from-to)1630-1636
Number of pages7
JournalJournal of Applied Physiology
Volume69
Issue number5
StatePublished - 1990
Externally publishedYes

Fingerprint

Ventilation
Pressure
Lung
Vascular Resistance
Atrial Pressure
Gases
Sheep
Arterial Pressure
Positive-Pressure Respiration
Artificial Respiration
Blood Vessels
Blood Pressure
Pregnancy

Keywords

  • birth
  • fetus
  • pulmonary blood flow
  • pulmonary vascular resistance

ASJC Scopus subject areas

  • Endocrinology
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Pulmonary pressure-flow relationships in the fetal lamb during in utero ventilation. / Reid, D. L.; Thornburg, Kent.

In: Journal of Applied Physiology, Vol. 69, No. 5, 1990, p. 1630-1636.

Research output: Contribution to journalArticle

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