Cerebral Perfusion Monitoring Using Near-Infrared Spectroscopy During Head-Up Tilt Table Test in Patients With Orthostatic Intolerance

Figures

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  Figure 1. Typical hemodynamic response of a healthy control (HC) during a head-up tilt table test (HUT) examination. The hemodynamic response for the HUT can be partitioned into three distinct sections: dynamic tilt phase (supine to tilt up), static tilt phase (remain tilted at 70°), and post tilt phase (tilted down back to supine position). The gray bar marks the approximate mechanical tilting time (approximately 20 s, depending on weight).

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  Figure 2. Channel correlation density map for (A) HC, (B) normal OI (NOI) and (C) abnormal OI (AOI) subjects. A line was drawn connecting channel pairs whose average correlation coefficient was greater than or equal to 0.8.

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  Figure 3. Representative recordings of blood pressure (BP)/heart rate (HR; top) and near-infrared spectroscopy (NIRS; bottom) responses for (A) HC, (B) NOI patient and (C–F) AOI patient with: (C) vasovagal syncope (VS), (D) postural orthostatic tachycardia syndrome (POTS), (E) orthostatic hypotension (OH) and (F) orthostatic hypertension (OHT). Starting points of dynamic tilt phase and post tilt phase are shown as black lines. BP is represented as a high low (systolic/diastolic) chart in blue and the HR is represented as the magenta line. The NIRS response is shown as HbO—red, Hb —blue, HbT—green.

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  Figure 4. Comparison of hemodynamic response (HbO—red; Hb—blue; HbT—green) during the dynamic tilt to the static tilt phase (left) and the end of static tilt to the post tilt phase (right) for (A) HC and (B) NOI. The gray bar marks the approximate mechanical tilting time (approximately 20 s, depending on weight). Statistically significant difference (p-value < 0.05) between NOI patients and HC is denoted with a square colored to match the respective hemodynamic response. The appearance of a bar implies a long time interval of statistically significant points.

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  Figure 5. (A) HC compared to various tilt table diagnoses: (B) VS, (C) POTS, (D) OH and (E) OHT for dynamic tilt to static tilt phase (left) and the end of static tilt to post tilt phase (right). The gray bar marks the approximate mechanical tilting time (approximately 20 s, depending on weight). Statistically significant difference (p < 0.05) between tilt table diagnoses and HC is denoted with a dot for the respective hemodynamic response (HbO—red; Hb—blue; HbT—green).

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  Figure 6. Example of 3rd order polynomial fitting for the HbT signal of (A) HC and (B) OI patient. The inflection point of the fitting line is denoted by the arrow. The inflection point during the HUT static period of the HUT is representative of the return to cerebral homeostasis.

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  Figure 7. Inflection point occurrence of HbT changes as the number of seconds after tilt up (with standard error bars) for HC, NOI, and AOI (VS, POTS, OH, OHT). A statistical significant difference (p-value < 0.05) between HC and patient group is denoted by an asterisk (*).