RT Journal Article SR Electronic T1 Tension pneumothorax: a difficult diagnosis JF Emergency Medicine Journal JO Emerg Med J FD BMJ Publishing Group Ltd and the British Association for Accident & Emergency Medicine SP 319 OP 320 DO 10.1136/emj.18.4.319 VO 18 IS 4 A1 B L Watts A1 M A Howell YR 2001 UL http://emj.bmj.com/content/18/4/319.abstract AB