Physiological measurement
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Physiological measurement · Aug 2006
The effect of applied sensor contact force on pulse transit time.
Pulse transit time (PTT) is usually determined as the time interval between the peak of the electrocardiogram (ECG) R wave and a characteristic point of the peripheral pulse measured by photoplethysmography. However, it was found that the photoplethysmogram (PPG) is affected by the contact force between the photoplethysmographic sensor and the measurement site, i.e. finger. Therefore, we hypothesized that the PTT may be altered by the applied sensor contact force. ⋯ With further increase in the contact force, they kept at an almost constant level. Such a changing trend was not found in PTT3. The results of this study suggest that the applied sensor contact force should be carefully controlled in PTT measurement to avoid diminishing its value as a diagnostic tool.
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Physiological measurement · Aug 2006
Broadband diffuse optical spectroscopy measurement of hemoglobin concentration during hypovolemia in rabbits.
Serial blood draws for the assessment of trauma patients' hemoglobin (sHgb) and hematocrit (sHct) is standard practice. A device that would allow for continuous real-time, non-invasive monitoring of hemoglobin and tissue perfusion would potentially improve recognition, monitoring and resuscitation of blood loss. We developed a device utilizing diffuse optical spectroscopy (DOS) technology that simultaneously measures tissue scattering and near-infrared (NIR) absorption to obtain non-invasive measurements of oxy- (Hb-O(2)), deoxyhemoglobin (Hb-R) concentrations and tissue hemoglobin concentration (THC) in an animal model of hypovolemic shock induced by successive blood withdrawals. ⋯ S(T)O(2) and [Hb-O(2)] followed similar trends with hemorrhage, while [Hb-R] remained relatively constant. These measurements may be limited to some extent by the inability to distinguish between hemoglobin and myoglobin contributions to DOS signals in tissue at this time. Broadband DOS provides a potential platform for reliable non-invasive measurements of tissue oxygenated and deoxygenated hemoglobin and may accurately reflect the degree of systemic hypovolemia and compromised tissue perfusion.