Which clinical signs and symptoms predict hypoxemia in acute childhood asthma?

OBJECTIVE: To find the clinical signs that are the best predictors of hypoxemia (SpO2 =92%) in acute asthma in children.
METHODS: Color of skin, dyspnea (by single breath counting), alertness, respiratory rate, presence of audible wheeze, wheezing on auscultation, accessory muscle use, nasal flaring, pulse rate, systolic and diastolic blood pressure, pulsus paradoxus and oxygen saturation at room air (by pulse oximetry) were recorded at the time of presentation and one hour after presentation after completion of 3 doses of nebulized salbutamol and budesonide.
RESULTS: Hypoxemia (SpO2 92% pounds sterling) was seen in 45% children at presentation and 14(28.6%) after one hour. The clinical signs that correlated significantly with hypoxemia at both time points were dyspnea assessed by single breath count (OR 3.3, 95% CI 0.9-12.9), accessory muscle use score > or = 3 (OR 3.0, 95% CI 0.9-15.4) and pulsus paradoxus> 10 (OR 3.0, 95% CI 0.7-13.6). In a multiple logistic regression model accessory muscle score > or = 3 and pulsus paradoxus> 10 were identified as independent predictors of hypoxemia (sensitivity 64.3%, specificity 91%).
CONCLUSION: Physical assessment in a child with acute exacerbation of asthma should at least include accessory muscle use and pulsus paradoxus, since these predict hypoxemia the best.