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Vena Cava Responsiveness to Controlled Isovolumetric Respiratory Efforts
Author(s) -
Folino Anna,
Benzo Marco,
Pasquero Paolo,
Laguzzi Andrea,
Mesin Luca,
Messere Alessandro,
Porta Massimo,
Roatta Silvestro
Publication year - 2017
Publication title -
journal of ultrasound in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 91
eISSN - 1550-9613
pISSN - 0278-4297
DOI - 10.1002/jum.14235
Subject(s) - medicine , isovolumetric contraction , vena cava , respiratory system , cardiology , intensive care medicine , blood pressure , diastole
Objectives Respirophasic variation of inferior vena cava (IVC) size is affected by large variability with spontaneous breathing. This study aims at characterizing the dependence of IVC size on controlled changes in intrathoracic pressure. Methods Ten healthy subjects, in supine position, performed controlled isovolumetric respiratory efforts at functional residual capacity, attaining positive (5, 10, and 15 mmHg) and negative (−5, −10, and −15 mmHg) alveolar pressure levels. The isovolumetric constraint implies that equivalent changes are exhibited by alveolar and intrathoracic pressures during respiratory tasks. Results The IVC cross‐sectional area equal to 2.88 ± 0.43 cm 2 at baseline (alveolar pressure = 0 mmHg) was progressively decreased by both expiratory and inspiratory efforts of increasing strength, with diaphragmatic efforts producing larger effects than thoracic ones: −55 ± 15% decrease, at +15 mmHg of alveolar pressure ( P < .01), −80 ± 33 ± 12% at −15 mmHg diaphragmatic ( P < .01), −33 ± 12% at −15 mmHg thoracic. Significant IVC changes in size ( P < .01) and pulsatility ( P < .05), along with non significant reduction in the response to respiratory efforts, were also observed during the first 30 minutes of supine rest, detecting an increase in vascular filling, and taking place after switching from the standing to the supine position. Conclusions This study quantified the dependence of the IVC cross‐sectional area on controlled intrathoracic pressure changes and evidenced the stronger influence of diaphragmatic over thoracic activity. Individual variability in thoracic/diaphragmatic respiratory pattern should be considered in the interpretation of the respirophasic modulations of IVC size.