The haemodynamic response to incremental increases in negative intrathoracic pressure in healthy humans
New Findings What is the central question of this study? The haemodynamic response to incremental increases in negative intrathoracic pressure (nITP) during spontaneous breathing and the mechanisms of cardiac impairment at these levels of nITP remain unclear. What is the main finding and its importa...
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Veröffentlicht in: | Experimental physiology 2018-04, Vol.103 (4), p.581-589 |
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Sprache: | eng |
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Zusammenfassung: | New Findings
What is the central question of this study?
The haemodynamic response to incremental increases in negative intrathoracic pressure (nITP) during spontaneous breathing and the mechanisms of cardiac impairment at these levels of nITP remain unclear.
What is the main finding and its importance?
nITP of −20 cmH2O or greater reduces stroke volume in healthy, spontaneously breathing supine humans due to direct ventricular interaction and increased left ventricular afterload.
Negative intrathoracic pressure (nITP) generally augments venous return and left ventricular (LV) stroke volume (LVSV), though large increases in nITP, commonly seen in respiratory disease, attenuate LVSV. Despite this consistent finding, the degree of nITP required to reduce LVSV and the contributions of series and direct ventricular interaction (DVI) in mediating this response remain unclear. We hypothesized that nITP ≤−15 cmH2O would augment LVSV, while nITP ≥−20 cmH2O would reduce LVSV via DVI and increased afterload. Twenty‐three healthy subjects were randomly given inspiratory loads during spontaneous breathing to generate −5, −10, −15, −20 and −25 cmH2O. LV volumes, LV geometry, inferior vena cava collapsibility (cIVC) and LV end‐systolic meridional wall‐stress (LVESMWS) were assessed in the supine position using tri‐plane echocardiography. LVSV remained unchanged up to −15 cmH2O, but was significantly reduced at nITP ≥−20 cmH2O (−12 ± 8% and −15 ± 11% at −20 and −25 cmH2O, respectively, P |
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ISSN: | 0958-0670 1469-445X |
DOI: | 10.1113/EP086654 |