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Official Journal of the Italian Society of Thoracic Endoscopy
Indexed/Abstracted in: EMBASE, Scopus
Online ISSN 1827-1723
Rubini A., Bortoletto E., Castelli G., Fasano F., Favero E., Tosatto V., Vettore E.
Section of Physiology, Department of Human Anatomy and Physiology, University of Padua, Padua, Italy
AIM: Positive end-expiratory pressure (PEEP) is a widely used therapeutical intervention increasing the adequacy of gas exchange during both artificial and spontaneous ventilation. However, the effects of PEEP on heart rate (HR) are not clearly understood, and conflicting results have been reported regarding this subject. According to the literature, sympathetic and parasympathetic mechanisms may be involved, but the effects of b1 receptors blockade have never been directly tested before.
METHODS: In order to study the possible effect of increased lung volume, we measured HR by electrocardiogram in 10 positive-pressure ventilated, anesthetized, trachetomized rats at three values of end-expiratory pressure (0, 5, 10 cm H2O). Measurements were obtained in control conditions, and compared with results observed after i.p. atropine or metoprolol.
RESULTS: A statistically significant decrease of HR with PEEP was detected both in control and metoprolol-treated rats. This effect was abolished by atropine, which also exhibited a paradoxical effect, i.e., caused a decrease of HR at any PEEP value. As CONCLUSIONS. Increasing lung volume by PEEP decreases HR in a dose-related fashion by a parasympathetic-mediated, atropine-sensitive mechanism, most likely the activation of volume-sensitive lung stretch receptors. ‚1 receptors blockade has no effect on HR-PEEP relationship, indicating that sympathetic-mediated mechanisms are not involved.