Pulmonary hydraulic impedance responses to hypoxia and hypercapnia in newborn pigs.
Publication/Presentation Date
7-1-1994
Abstract
The purpose of this study was to determine the cumulative effects of brief intervals of hypoxia and hypercapnia on the pulsatile characteristics of the pulmonary arterial circulation of 48-h-old compared with 2-wk-old open-chest Yorkshire pigs while using two different anesthetic regimens: 1) azaperone and ketamine (4 and 12 mg/kg im, respectively) and 2) thiopental sodium (25 mg/kg i.v.). Animals 48 h old were randomly allocated to undergo mild hypoxia (inspired O2 fraction = 0.15), severe hypoxia (inspired O2 fraction = 0.05), or hypercapnia (inspired CO2 fraction = 0.20), whereas animals 2 wk old underwent severe hypoxia or hypercapnia. With use of Fourier analysis, characteristic impedance (Zo), mean input impedance (Zm), impedance moduli, and phase angles were determined. In 48-h-old pigs anesthetized with azaperone-ketamine, neither mild nor severe hypoxia altered Zo, Zm, or pulmonary vascular resistance (PVR), whereas hypercapnia increased Zo by 22% (P < 0.001), which persisted despite a return to normocapnia. In 48-h-old animals anesthetized with thiopental, baseline control Zo and Zm were lower than those in same-age pigs anesthetized with azaperone-ketamine. In thiopental-anesthetized 48-h-old pigs, both severe hypoxia and hypercapnia increased Zm and PVR but Zo was unaltered. In 2-wk-old pigs anesthetized with thiopental, severe hypoxia but not hypercapnia elevated Zm and PVR, whereas Zo was not changed with either stress. Results indicate age- and anesthetic-dependent responses of Zo, Zm, and PVR to severe hypoxia and hypercapnia. The persistent elevation in Zo caused by hypercapnia indicates a prolonged decrease in arterial compliance or a reduction in effective proximal pulmonary arterial radius.
Volume
77
Issue
1
First Page
386
Last Page
396
ISSN
8750-7587
Published In/Presented At
Domkowski, P. W., Cockerham, J. T., Crescenzo, D. G., Kot, P. A., Dyer, K. L., Wang, Y., Messier, R. H., Jr, Analouei, A. R., Wallace, R. B., & Hopkins, R. A. (1994). Pulmonary hydraulic impedance responses to hypoxia and hypercapnia in newborn pigs. Journal of applied physiology (Bethesda, Md. : 1985), 77(1), 386–396. https://doi.org/10.1152/jappl.1994.77.1.386
Disciplines
Medicine and Health Sciences
PubMedID
7961261
Department(s)
Department of Surgery
Document Type
Article