An 8yo boy has longstanding asthma. He has admitted with a severe episode and is tired and
drowsy. He has not improved on oxygen, inhaled B2 agonist and IV hydrocortisone. CXR shows
bilateral hyperinflation. He is too breathless to use a peakflow meter and is O2 sat <90%. What
is the single most appropriate inv?
c. CT chest
d. Pulse oximetry
To find out if PaCo2 is normal or decreased, normally it should be increased, if not that signifies respiratory muscle fatigue and inability to hyperventilate > rapid transfer to ICU.