At. Rheineckleyssius et Cj. Kalkman, INFLUENCE OF PULSE OXIMETER LOWER ALARM LIMIT ON THE INCIDENCE OF HYPOXEMIA IN THE RECOVERY ROOM, British Journal of Anaesthesia, 79(4), 1997, pp. 460-464
In a prospective, randomized study, we have investigated the effects o
f two arbitrary pulse oximeter lower alarm limit (LAL) settings (90%=g
roup 90, n=320 and 85%=group 85, n=327) on the incidence of hypoxaemia
in the recovery room. in group 90, we calculated the theoretical effe
ct of elimination of transient episodes of low pulse oximeter oxyhaemo
globin saturation (Sp(O2)) by introducing a time delay between the ons
et of the alarm condition and triggering of the alarm. When only hypox
aemic episodes lasting more than 1 min were included, Sp(O2) less than
or equal to 90% occurred in 11% of patients in group 90 and in 20% in
group 85 (relative risk (RW) 1.84, confidence interval (CI) 1.26-2.69
; P<0.01). Hypoxaemia less than or equal to 85% occurred in 2% of pati
ents in group 90 and in 6% in group 85 (RR 3.10, CI 1.32-7.28; P<0.01)
. In group 90, 1007 alarms (33% false) occurred, whereas in group 85,
395 alarms (28% false) occurred. Introducing a theoretical delay of 15
s in group 90 between crossing the alarm threshold and triggering the
alarm would have reduced the number of alarms by 60%. The results of
the study suggest that decreasing the alarm limit in an attempt to red
uce frequent false alarms may lead to an increase in more relevant epi
sodes of hypoxaemia and setting the LBL at 85% cannot be recommended r
outinely. Introducing a 15 s delay in group 90 would reduce the number
of alarms by the same amount as changing the LAL from 90% to 85%.