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Methods Inf Med 2004; 43(03): 296-301
DOI: 10.1055/s-0038-1633871
Original Article
Schattauer GmbH

Comparison of Closed-loop and Open-loop Models in the Assessment of Cardiopulmonary and Baroreflex Gains

R. Takalo
1   Division of Nuclear Medicine, Dept. of Clinical Chemistry, Oulu University Hospital, Oulu, Finland
,
J. P. Saul
2   The Children’s Heart Program of South Carolina, Medical University of South Carolina, Charleston, SC, USA
,
I. Korhonen
3   VTT Information Technology, Tampere, Finland
› Author Affiliations
Further Information

Publication History

Publication Date:
05 February 2018 (online)

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Summary

Objectives: Both open- and closed-loop models of beat-to-beat cardiovascular control have been suggested. We tested whether the modelling yields different results with real data while assessing cardiopulmonary and baroreflex gains.

Methods: Two autoregressive models are described to resolve causal relationships between systolic blood pressure (SBP), RR-interval (RRI) and instantaneous lung volume (ILV): a closed-loop model which takes into account both the RRI changes induced by changes in SBP and the SBP changes mediated by changes in RRI, and an open-loop model which does not have a link from RRI to SBP. The performance of the models was compared in 14 healthy men in supine and standing positions under control conditions and under conditions of β-sympathetic and parasympathetic pharmacological blockades. Transfer function gains were computed from ILV to RRI (cardiopulmonary gain) and from SBP to RRI (baroreflex gain). The measurements were done under controlled random-interval breathing.

Results: The gains identified by the open-loop model tended to be higher than those from the closed-loop model, but the differences did not reach statistical significance. Importantly, the two models discriminated the changes in transfer gains between different interventions equally well.

Conclusions: Because the interactions between SBP and RRI occur physiologically in a closed-loop condition, the closed-loop model provides a theoretical advantage over the open-loop model. However, in practise, it seems to be little reason to select one over the other due to methodological errors when estimating cardiopulmonary or baroreflex transfer gains.

Keywords

Multivariate - modelling - baroreceptors - blood pressure - heart rate
 

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