The 10 mL syringe is useful in generating the recommended standard of 40 mmHg intrathoracic pressure for the Valsalva manoeuvre.

OBJECTIVE: The Valsalva manoeuvre (VM) continues to be first-line management for haemodynamically stable supraventricular tachycardia in the acute setting. 40 mmHg of intrathoracic pressure is seen as an essential component of the VM. Anecdotally, blowing into a 10 mL syringe to move the plunger is one method of pressure generation; however, to date its effectiveness has not been tested. The objective of the present study was to assess if blowing into a syringe sufficient to move the plunger could produce the required 40 mmHg of pressure.
METHODS: A two-part experimental study tested the pressure required to move the plunger, and sustain that movement for 15 s, in a Terumo syringe. Part one tested a range of syringe sizes. Part two, a repeated measures study, tested the syringe to ascertain if a pressure reduction occurred after repeated use. A sphygmomanometer was attached to the syringe via a 10 cm length of tubing with another length of tubing attached to the sphygmomanometer enabling an investigator to blow into the syringe.
RESULTS: In part one, the 10 mL syringe was the only size noted to provide the required 40 mmHg pressure to move the plunger. In part two, the mean for each of the three tests per syringe varied between 37.0 mmHg (95% CI 34.2-39.8) and 40.2 mmHg (95% CI 37.5-43.0). There was no statistically significant fall noted over three uses of the same syringe.
CONCLUSION: The present study has demonstrated that blowing into a 10 mL Terumo syringe, to move the plunger, generated 40 mmHg intrathoracic pressure, thereby meeting the recommended intrathoracic pressure for optimum VM performance.