Oxygen saturation/minute heart rate index: Simple lung function test for children.

BACKGROUND: The severity of airway obstruction can be accurately determined on spirometry in children with asthma. Other assessments may include peak expiratory flow and pulse oximetry. In the present study, we evaluated the validity and reliability of oxygen saturation/minute heart rate (SpO2 /MHR) index in the prediction of degree of severe airway obstruction in children with asthma.

METHODS: This was a retrospective study of children aged 7-17 followed for asthma at Mersin Women and Children's Hospital. The study compared SpO2 /MHR ratio with forced expiratory volume in 1 s (FEV1 ) measured on spirometry, an important indicator of small airway obstruction. A total of 296 patients were included in the study, and classified either as having normal FEV1 (FEV1 > 80% of predicted, n = 178) or severely reduced FEV1 (FEV1 < 60% of predicted, n = 118). Positive and negative predictive values (PPV and NPV), sensitivity and specificity of SpO2 /MHR index in predicting low FEV1 were calculated on receiver operating characteristics analysis.

RESULTS: An SpO2 /MHR ratio cut-off <0.90 was associated with a PPV of 83.14%, NPV of 71.77%, sensitivity of 80.34% and specificity of 75.42% in predicting low FEV1 .

CONCLUSIONS: SpO2 /MHR ratio appears to be a highly useful index to assess airway obstruction in older children with asthma. Thus, it can be used as a marker of airway obstruction severity when spirometry is not available.