Experimental Configuration
The Valsalva test setup integrates an ADInstruments Human NIBP System with a PowerLab 26T and a Bridge Amp to record continuous, beat-to-beat arterial pressure, ECG (via the built in Bio Amp) and mouth pressure. The mouth pressure assembly consists of a syringe and a 3-way tap connected to a mechanical dial manometer and a differential pressure transducer, the latter of which interfaces with a Bridge Amp connected to the PowerLab 26T through an I²C cable. Throughout the procedure, the subject wears a nose clip to ensure all respiratory effort is captured.
Test Procedure
Following the recording of a baseline period in LabChart, the subject inhales deeply and then exhales forcefully into the mouthpiece. This pressure is transmitted through the 3-way valve, providing both a physical reading on the mechanical dial and a digital signal via the transducer for real-time display in LabChart. Guided by these visual cues, the subject aims to maintain a constant airway pressure of approximately 40 mmHg for a duration of 15 seconds, immediately followed by a release of strain and a return to normal breathing.
Data Analysis and Autonomic Assessment
LabChart is used to monitor heart rate and blood pressure fluctuations across the four phases of the Valsalva maneuver:
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Phase I: The initial mechanical increase in blood pressure.
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Phase II: A drop in pressure followed by compensatory tachycardia during the strain.
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Phase III: A brief pressure dip upon the release of exhalation.
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Phase IV: A blood pressure overshoot that induces reflex bradycardia.
These metrics are used to determine the Valsalva Ratio—calculated as the peak heart rate during strain divided by the minimum heart rate during the recovery phase—to provide a detailed assessment of baroreflex function and autonomic nervous system health.
Fig 1 Shows Setup for Valsalva Fig 2 shows Demonstration Using PowerLab