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Head-down Tilt (head-down + tilt)

Distribution by Scientific Domains

Medical Sciences	75%

Selected Abstracts

Effects of alcohol and smoking during pregnancy on infant autonomic control

DEVELOPMENTAL PSYCHOBIOLOGY, Issue 3 2009
William P. Fifer
Abstract Prenatal exposure to smoking and alcohol increases the risk for Sudden Infant Death Syndrome (SIDS). Physiological changes associated with these exposures are not well studied. Full-term infants were tested within the first 3 days of life. We hypothesized that maternal alcohol consumption and/or smoking during pregnancy would alter autonomic nervous system function. Newborns whose mothers smoked during pregnancy had lower beat-to-beat heart rate variability in quiet sleep. Infants whose mothers consumed alcohol had lower global heart rate variability, but only in active sleep. Unexposed infants demonstrated increases in heart rate with head-up tilt and decreases in heart rate with head-down tilt, but smoking and alcohol-exposed infants showed no significant responses. These results indicate that autonomic function is altered by prenatal exposure to alcohol and smoking. Such markers may provide early identification of infants at greatest risk for SIDS. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 51: 234,242, 2009 [source]

Relationship between stroke volume, cardiac output and filling of the heart during tilt

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 10 2009
M. BUNDGAARD-NIELSEN
Background: Cardiac function curves are widely accepted to apply to humans but are not established for the entire range of filling of the heart that can be elicited during head-up (HUT) and head-down tilt (HDT), taken to represent minimal and maximal physiological filling of the heart, respectively. With the supine resting position as a reference, we assessed stroke volume (SV), cardiac output (CO) and filling of the heart during graded tilt to evaluate whether SV and CO are maintained during an assumed maximal physiological filling of the heart elicited by 90° HDT in healthy resting humans. Methods: In 26 subjects, central blood volume was manipulated with graded tilt from 60° HUT to 90° HDT. We measured SV, CO (Finometer®) and cardiac filling by echocardiography of the left ventricular end-diastolic volume (LVEDV; n=12). Results: From supine rest to 60° HUT, SV and CO decreased 23 ml [confidence intervals (CI): 16,30; P<0.001; 23%] and 0.9 l/min (0.4,1.4; P<0.0001; 14%), respectively, but neither SV nor CO changed during HDT up to 70°. However, during 90° HDT, SV decreased 12 ml (CI: 6,19; P<0.0001; 12%), with an increase of 21 ml (9,33; P=0.002; 16%) in LVEDV because HR increased 3 bpm and CO decreased 0.5 l/min (ns). Conclusion: This study confirmed that SV and CO are maximal in resting, supine, healthy humans and decrease during HUT. However, 90° HDT was associated with increased LVEDV and induced a reduction in SV. [source]

Stroke volume of the heart and thoracic fluid content during head-up and head-down tilt in humans

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2005
J. J. Van Lieshout
Background:, The stroke volume (SV) of the heart depends on the diastolic volume but, for the intact organism, central pressures are applied widely to express the filling of the heart. Methods:, This study evaluates the interdependence of SV and thoracic electrical admittance of thoracic fluid content (TA) vs. the central venous (CVP), mean pulmonary artery (MPAP) and pulmonary artery wedge (PAWP) pressures during head-up (HUT) and head-down (HDT) tilt in nine healthy humans. Results:, From the supine position to 20° HDT, SV [112 ± 18 ml; mean ± standard deviation (SD)], TA (30.8 ± 7.1 mS) and CVP (3.6 ± 0.9 mmHg) did not change significantly, whereas MPAP (from 13.9 ± 2.7 to 16.1 ± 2.5 mmHg) and PAWP (from 8.8 ± 3.4 to 11.3 ± 2.5 mmHg; P < 0.05) increased. Conversely, during 70° HUT, SV (to 65 ± 24 ml) decreased, together with CVP (to 0.9 ± 1.4 mmHg; P < 0.001), MPAP (to 9.3 ± 3.8 mmHg; P < 0.01), PAWP (to 0.7 ± 3.3 mmHg; P < 0.001) and TA (to 26.7 ± 6.8 mS; P < 0.01). However, from 20 to 50 min of HUT, SV decreased further (to 48 ± 21 ml; P < 0.001), whereas the central pressures did not change significantly. Conclusions:, During both HUT and HDT, SV of the heart changed with the thoracic fluid content rather than with the central vascular pressures. These findings confirm that the function of the heart relates to its volume rather than to its so-called filling pressures. [source]

Cerebral oxygenation monitor during head-up and -down tilt using near-infrared spatially resolved spectroscopy,

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 4 2003
Koichi Kurihara
Summary Reflectance near-infrared spectroscopy (NIRS) has become a suitable and easily manageable method to monitor cerebral oxygenation changes in presyncopal and syncopal symptoms caused by postural changing or standing. A new clinical tissue oxygenation monitor has been recently developed which measures absolute tissue haemoglobin saturation (Tissue Oxygenation Index, TOI) utilizing spatially resolved spectroscopy (SRS). The present study examined the effects of postural changes on cerebral oxygenation as reflected in SRS-NIRS findings. Cerebral oxyhaemoglobin (O2Hb), deoxyhaemoglobin (HHb), and the TOI were recorded from both sides of the forehead in five healthy male subjects (age range, 28,40 years) during 90° head-up tilt (HUT) and ,6° head-down tilt (HDT). Three series of measurements were carried out on separate days. O2Hb was decreased during HUT. TOI was significantly lower in HUT than in the supine position (SUP). There was no significant change in TOI during HDT. A significant session effect was observed in the left forehead TOI during SUP, but not in the right. SRS-NIRS measurements confirmed sub-clinical alterations of cortical oxygenation during HUT. NIRS data from the left side of the forehead, which may vary with cognitive or emotional activation, were more variable than those from the right side. [source]