Physiological measurement
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Physiological measurement · Apr 2012
Stroke volume obtained by electrical interrogation of the brachial artery: transbrachial electrical bioimpedance velocimetry.
The goal of this study is to measure left ventricular stroke volume (SV) from the brachial artery (BA) using electrical bioimpedance. Doppler-derived SV was used for comparison. Twenty-nine healthy adults were recruited for study. ⋯ To assess the contribution of blood resistivity variations to ΔZ(t), BA diameters were measured at end-diastole and peak systolic expansion. Results indicate that since the BA demonstrates parabolic, laminar flow, with minimal diameter changes, blood resistivity variations are likely responsible for the derived impedance changes. Bland-Altman analysis shows that SV is obtainable by TBEV from healthy humans at rest.
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Physiological measurement · Apr 2012
Impact of gender on snore-based obstructive sleep apnea screening.
Obstructive sleep apnea syndrome (OSA) is a serious widespread disease in which upper airways (UA) are collapsed during sleep. OSA has marked male predominance in prevalence. Although women are less vulnerable to OSA, under-diagnosed OSA in women may associate with serious consequences. ⋯ The results were K-fold cross-validated. Gender-dependent modeling resulted in an increase of around 7% in sensitivity and 6% in specificity at the decision threshold AHI = 15 against a gender-neutral model. These results established the importance of adopting gender-specific models for the snore-based OSA screening technique.
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Physiological measurement · Apr 2012
Impact of intra-abdominal pressure on retrohepatic vena cava shape and flow in mechanically ventilated pigs.
Conflicting results have been found regarding correlations between right atrial pressure (RAP) and inferior vena cava (IVC) diameter in mechanically ventilated patients. This finding could be related to an increase in intra-abdominal pressure (IAP). This study was designed to clarify whether variations in IVC flow rate caused by positive pressure ventilation are associated with changes in the retrohepatic IVC cross-section (ΔIVC) during major changes in volume status and IAP. ⋯ The majority of animals with an IVC area of less than 0.65 cm(2) showed evidence of IAP greater than RAP values. Negative RAP-IAP pressure gradients were found to occur with an IVC area of less than 0.65 cm(2), suggesting that IVC dimensions determined using standard ultrasound techniques may indicate the direction of the RAP-IAP gradient. The clinical relevance of the present findings is that volume status should not be estimated from retrohepatic IVC dimensions in cases of high IAP.