Various monitoring techniques by combined application of transcranial Doppler (TCD), near infrared spectroscopy (NIRS), and head-up tilt test (HUTT) were used to assess changes in cerebral blood flow(CBF), heart rate(HR), blood pressure(BP), cerebral tissue oxygenation(CO₂Hb), and cerebral autoregulation(CA) in POTS patients, in order to screen for the best predictive diagnostic tools for presyncope.

Patients with symptoms of OI for more than 3 months suspected of POTS were selected, and TCD, NIRS, HUTT,CA were performed simultaneously to monitor the trajectory of CBF, HR, BP, CO₂Hb and CA, and to statistically measure the sensitivity and specificity of each monitoring tool for diagnosing POTS, and to establish a diagnosis model for best predicting of presyncope.

HR of POTS patients changed from a compensatory increase before syncope to a transient decrease with syncope, and the time of HR reaching standard appeared 4.7 minutes before syncope.TCD shows a shift from a diastolic bow-dorsal elevation spectrum to a presyncopal “spike wave” spectrum, which can specifically predict syncope as early as 1 minute before syncope; no changes of gain, phase and coho were seen during HUTT. CO₂Hb showed cyclic fluctuations during HUTT, with no specific indicators, but CO₂Hb could decline as early as 2.5 minutes before syncope. 

Multimodal monitoring technology can dynamically monitor the trajectory of CBF in POTS patients by multiple indicators, and NIRS provides an earlier warning of syncope than HUTT, an examination technique that can reduce falls and syncope.