RT Journal Article SR Electronic T1 Valsalva manoeuvre using a syringe: physics and implications JF Emergency Medicine Journal JO Emerg Med J FD BMJ Publishing Group Ltd and the British Association for Accident & Emergency Medicine SP 831 OP 831 DO 10.1136/emermed-2016-206318 VO 33 IS 11 A1 Leszek Pstras YR 2016 UL http://emj.bmj.com/content/33/11/831.abstract AB