BACKGROUND: The diagnosis of asthma is difficult to establish using spirometry in children below 5 years old. Tidal breathing analysis (TBA) can provide useful information about lung function in infants and young children, as it is effort-independent. 

OBJECTIVES: To determine if baseline and post-bronchodilator ratios of the time and volume until peak expiratory flow to the total expiratory time and volume, (tPEF/tE and V PEF/V E) can distinguish asthmatics from normal children.

METHODS: This is a cross-sectional study wherein 146 children ages 6 months to 5 years old completed TBA before and 15 minutes after administration of 250?g of salbutamol via nebulization. Children 3 years old and below who did not cooperate were given sedation with oral diphenhydramine (1mg/kg/dose). The tPEF/tE and VPEF/VE were compared between the controls and asthmatics.

RESULTS: In children below 2 years old, the baseline tPEF/tE of asthmatics and non-asthmatics were 29.6  ± 13.8and 22.0 ± 6.6. The area under the curve (AUC) was 0.649 attPEF/tEof 32.250, with a sensitivity and specificity of 50% and 97%. The baseline VPEF/VE of asthmatics and non-asthmatics were 32.7 ±12.4 and 26.0 ± 4.9.AUC was 0.661 at VPEF/VEof34.500, with a sensitivity and specificity of 50% and 97%.In subjects 2 to 5 years old, the baseline tPEF/tE of asthmatics and non-asthmatics were 35.3 ± 14.7 and 35.0 ± 13.1. The baseline VPEF/VE were 37.0 ± 12.3 and 36.7 ± 10.7. After salbutamol nebulization, the tPEF/tE of asthmatics and non-asthmatics in all ages were 30.9±13.7 and 27.9± 10.8. The VPEF/VE were 34.1± 11.4 and 30.9± 9.0.

CONCLUSION: Baseline tPEF/tE and VPEF/VE can distinguish asthmatics from non-asthmatics in children below 2 years old. However, baseline tPEF/tE and VPEF/VE in children 2 to 5 years old and post-bronchodilator tPEF/tE and VPEF/VE in all ages could not distinguish asthmatics from non-asthmatics after nebulization with 250?g of salbutamol.