Abstract 125

Background: PT can be life threatening and brain damaging. Using trend tcPCO2 we have noted that clinical diagnosis is often several hours after the probable occurrence of air leak.

Hypothesis: the slope of the trend tcPCO2 will give early warning of PT allowing more timely intervention.

Subjects: Over 4 years 1203 infants were admitted for NNIC and 42 were identified to have a PT after admission to our tertiary referral unit.

Measurements: TcPCO2 and tcPO2 are measured at 1 Herz to a computerised monitoring system in all babies receiving NNIC. The time of PT was identified by the time of rise in tcPCO2 and fall in tcPO2 prior to the first X ray showing the air leak. The slope of the tcPCO2 was calculated over 5, 10, 15 mins and compared to the reference centiles from 853 low risk infants without PT.

Results: The 90th centiles of the normal slopes of tcPCO2 (kPa/min) were: over 5 mins = 0.06, over 10 mins = 0.045, over 15 mins= 0.037. The number of PT with slopes greater than the 90th centiles= 24/36 at 5, 23/36 at 10, and 18/35 at 15 mins (note denominator less than n=42 because of probe changes) and a total of 29 of the 42 cases would have been identified within 15 mins.

Conclusions: The slope of tcPCO2 trend can identify onset of pneumothorax in a significant proportion of cases giving extra warning for orderly intervention.