Definition and Overview
The Valsalva maneuver is a movement that increases intrathoracic pressure by covering the mouth or nose and performing forced exhalation. Since its description by Italian anatomist Antonio Maria Valsalva (1666-1723), it has been widely used in clinical medicine and physiological research.
The Valsalva maneuver test is a standard autonomic function test that simultaneously evaluates sympathetic and parasympathetic nerve functions by analyzing the pattern of changes in heart rate and blood pressure that occur during this movement. It is recommended as a standard item for evaluating autonomic function by the American Academy of Neurology (AAN) and the American Diabetes Association (ADA).
physiological principles
The Valsalva maneuver consists of four steps.
Phase I: As soon as forced exhalation begins, the aorta is compressed due to an increase in intrathoracic pressure, causing a temporary increase in blood pressure. Heart rate decreases reflexively.
Phase II: Venous return decreases as intrathoracic pressure continues to rise. As cardiac output decreases, blood pressure gradually falls. To compensate for this, the sympathetic nerves are activated, the heart rate increases, and peripheral blood vessels constrict. Phase 2 is subdivided into early (IIa) and late (IIb). As sympathetic nerve activity increases in IIb, blood pressure begins to recover.
Phase III: Immediately after forced expiration ends, intrathoracic pressure suddenly decreases and venous blood flows into the lungs, resulting in a temporary drop in blood pressure.
Phase IV: Blood pressure overshoots due to normalization of venous return and vasoconstriction effects. As a baroreceptor response to this increase in blood pressure, the parasympathetic nerves are activated and the heart rate decreases.
Valsalva Ratio
Valsalva ratio (VR) is the maximum heart rate during the exercise divided by the minimum heart rate after the exercise.
VR = maximum heart rate during manipulation / minimum heart rate after manipulation
VR is a representative indicator of parasympathetic nerve function, and normal values vary depending on age. In general, VR ≥ 1.50 is the normal range in young adults, and the lower normal limit decreases with age. Anything below 1.20 is considered an abnormal finding.
According to research, VR shows an inverse correlation with the duration of diabetes and the level of glycated hemoglobin, so the worse the blood sugar control, the lower the VR.
Blood pressure response analysis
Assess sympathetic nerve function through blood pressure response patterns.
Normal response: In phase 2, blood pressure is partially restored to baseline level by sympathetic nerve activity (IIb blood pressure recovery), and in phase 4, blood pressure overshoot occurs.
Adrenergic failure pattern: In phase 2, blood pressure does not return to baseline and continues to fall (loss of recovery in IIb blood pressure), and there is no excessive increase in blood pressure in phase 4. This pattern is observed in pure autonomic failure, multiple system atrophy, and diabetic autonomic neuropathy.
Inspection Procedure
To prepare for the test, it is recommended to perform the test after resting for at least 30 minutes, and to fast for at least 2 hours and quit smoking before the test. Connect a continuous blood pressure measuring device (Finometer or Portapres) to the electrocardiogram. When performing the maneuver, maintain a pressure of 40 mmHg for 15 seconds using a sheet or mouthpiece. Perform at least twice to check reproducibility.
It is contraindicated in situations where a severe increase in intra-abdominal pressure may be a problem (recent surgery, eye disease, suspected increase in intracranial pressure).
clinical application
The Valsalva test plays a key role in the diagnosis and severity assessment of diabetic cardiac autonomic neuropathy. Among the five standard autonomic function tests recommended by the ADA guidelines, the Valsalva maneuver is a representative test that simultaneously evaluates VR (parasympathetic nerve) and blood pressure response (sympathetic nerve).
It is also useful in evaluating POTS (orthostatic tachycardia syndrome). Abnormalities in the sympathetic response pattern during the Valsalva maneuver are observed in some POTS patients. It is also used to differentiate autonomic nerve involvement in multiple system atrophy and Parkinson's disease.