During a recent American Heart Association (AHA) Advanced Cardiovascular Life Support (ACLS) course, one of the ED nurses stated that he instructs patients to blow into a 10-mL syringe as a vagal maneuver to terminate supraventricular tachycardia (SVT). Can you explain this modified Valsalva maneuver?-D.I., N.Y.

Denise Drummond Hayes, MSN, RN, CRNP, responds: A modified Valsalva maneuver, which involves performing a Valsalva maneuver with postural modifications, has been shown to be more effective than the standard Valsalva maneuver for restoring sinus rhythm in patients with SVT. Although various physical maneuvers can increase vagal tone, only a few of them, including the Valsalva maneuver, are used clinically for diagnostic or therapeutic purposes in patients with clinically stable, regular rhythm, narrow complex tachycardia with a pulse.1 The local release of acetylcholine in the heart caused by parasympathetic (vagal) stimulation slows the rate of impulse formation in the sinoatrial node, and slows conduction velocity and lengthens the refractory period in the atrioventricular node. Gradual slowing of the tachycardia may result, followed by termination of the dysrhythmia.2

Nurses commonly position the patient in a semi-Fowlers or supine position and instruct the patient to perform the Valsalva maneuver by exhaling forcefully against a closed glottis after a normal inspiratory effort. The nurse typically instructs the patient to "breathe in, hold your breath, and bear down hard like you are having a bowel movement." The nurse then assesses for signs that the patient is adequately performing the maneuver, including neck vein distension, increased abdominal wall muscle tone, and a flushed face.2 The nurse also closely monitors the patient's vital signs and cardiac rate and rhythm. The patient should maintain the strain for 10 to 15 seconds and then resume normal breathing.2

A modified Valsalva maneuver involves a strain of 40 mm Hg pressure for 15 seconds with the patient in the semirecumbent position, followed by supine repositioning with 15 seconds of passive leg raise at a 45-degree angle. Instructing the patient to blow into a 10-mL syringe hard enough to move the plunger generates a strain of approximately 40 mm Hg.

This technique has been shown to be better for converting SVT into normal sinus rhythm. Researchers in the Postural Modification to the Standard Valsalva Manoeuvre for Emergency Treatment of Supraventricular Tachycardias (REVERT) randomized controlled study found that more than 40% of patients were converted to sinus rhythm with the postural modification to the standard Valsalva maneuver, compared with 17% with a standard Valsalva maneuver.3 The REVERT researchers suggest that many patients could avoid drug therapy or even seeking healthcare for SVT if they are taught this technique.

Although generally well tolerated, the Valsalva maneuver has several important contraindications, including aortic stenosis, recent myocardial infarction, glaucoma, and retinopathy.3 Potential complications of performing a Valsalva maneuver include rupture of the round window membrane of the ear.2 Assess patients for contraindications before initiating any Valsalva maneuver and assess for complications afterward.

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