Pulmonary function of normal toddlers from 1 to 3 years old in Guangzhou area

Objective To explore the development of pulmonary function of normal toddlers between 1 and 3 years old.Methods Totally 120 normal toddlers were divided into 2 groups according to their age , i.e. , 1-2 years old , -3 years old. Pediatric pulmonary function laboratory type 2600 (Sensor Medics Corporation, USA ) was used to detect tidal flow volume curve, which can partially replace the maximum expiratory flow volume curve. Parameters showing small airway function were the ratio of the volume to reach peak tidal expiratory flow to total expiratory volume, the ratio of tidal expiratory flow at 25% remaining expiration to peak expiratory flow, and ratio of inspiratory time to total respiratory time. Parameters showing large airway function were the ratio of mid-tidal expiratory flow to mid-tidal inspiratory flow. Passive expiratory flow volume technique was used to examine respiratory system static compliance and total airway resistance. Open nitrogen washout method was used to measure functional residual volume.Results No significant difference was found between male and female toddlers (P0.05). Between the two groups, the difference of respiratory rate was not significant(27 vs 26,t=1.512,P0.01). The values of tidal volumes in the -3 years group were notably higher than in the 1-2 years group (0.123 vs 0.091,t=8.587,P0.01), but the values of tidal volumes per kilogram body weight were not significantly different (0.009 1 vs 0.008 6,t=1.959,P0.01). The peak tidal expiratory flow in the elder group was similarly distinctly higher than that in the other group. The measured tidal breathing flow volume loops were both displayed uncharacteristic ellipse. The ratioes of inspiratory time to total respiratory time, the volume to reach peak tidal expiratory flow to total expiratory volume, tidal expiratory flow at 25% remaining expiration to peak expiratory flow and mid-tidal expiratory flow to mid-tidal inspiratory flow were not significantly different between two groups ( P0.05). But the ratio of peak tidal flow to tidal volume (1.095 vs 1.257, t=2.098,P0.05)and the respiratory system resistances (2.071 vs 2.697,t=3.761,P0.01)were evidently lower in the elder group than in the younger.The respiratory system compliances (0.352 vs 0.254,t=4.297,P0.01)and functional residual capacities (0.271 vs 0.211,t=8.468,P0.01)were significantly higher in the elder group than that in the younger, but the values per kilogram body weight were not significantly different ( P0.01). It was shown that the values of tidal volume, peak tidal expiratory flow, respiratory system static compliance, residual volume were significantly different (P0.01), between two groups. The values of each parameter mentioned above were increased with age, and were positively correlated with body weight (r=0.457,0.849,0.572,0.319).Conclusions Tidal breathing flow volume loop could show functions of small and large airways and partially replace the maximum expiratory flow loop.The parameters were stable in toddlers and could be used as reasonable index to evaluate the pulmonary function changes in pulmonary diseases. The ventilatory function, residual volume, respiratory system static compliance and peak tidal flow were increased with the age, which coincides with the rule of development of toddlers.