Prospective controlled trial of the pulmonary function between 1 to 2 years old and elder than 2 years old toddlers with pneumonia caused by M.pneumoniae

Objective To observe the alteration of pulmonary function in toddlers with pneumonia caused by M.pneumoniae(MP).Methods We detected the concentration of serum specific antibody against MP(IgM) with the agglutination test to support the diagnosis of MP infection,and a titer of 1∶160 or greater was considered as positive. The reagents were purchased from the Fujitsu Corporation of Japan.The pulmonary function of 77 hospitalized toddlers with pneumonia caused by MP who fulfilled the exclusion criteria was tested respectively during acute phase and compared with the 120 healthy toddlers . There were three exclusion criteria.One was cough lasting more than 2 weeks upon hospitalization,another was multiple infections, and the other was the children who combined with asthma . In these two groups,younger than 2 years old toddlers were compared with elder than 2 years old ones.Pediatric pulmonary function laboratory type 2600 (Sensor Medics Corporation,USA) was used to detect tidal flow volume curve,which could partially replace the maximum expiratory flow volume curve.Parameters showing small airway function were ratio of the volume to reach peak tidal expiratory flow to total expiratory volume(%V-PF),ratio of tidal expiratory flow at 25% remaining expiration to peak expiratory flow(25/PF),and ratio of inspiratory time to total respiratory time(Ti/Tt).Parameter showing large airway function was ratio of mid-tidal expiratory flow to mid-tidal inspiratory flow(ME/MI).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 In the toddlers from 1 to 2 years of age,during the acute phase of pneumonia caused by MP,the respiratory rate (RR) and peak tidal expiratory flow (PTEF) were significantly increased,Ti/Tt,%V-PF,25/PF,ME/MI,functional residual capacity per kilogram (FRC/kg) and respiratory system compliance per kilogram (Crs/kg) were significantly decreased comparing with those normal toddlers.In the toddlers from 2 to 3 years of age,PTEF was significantly increased,Ti/Tt,%V-PF and 25/PF were significantly decreased,but there was no significant difference in Crs/kg and FRC/kg.During acute phase,the tidal breathing flow-volume (TBFV) loops both displayed a concave expiratory curve.And the results of the pulmonary function testing in 1-3 years old toddlers with pneumonia caused by MP were coincided with their clinical manifestations.The younger group was more severe than the elder group,and the difference was significant (P0.05) . In the younger group,more patients (51.2%) had productive cough than in the elder group(26.5%).More patients had moist rales in lungs and spot-patchy shadows in chest X-ray in the younger ( in order,44.2% , 83.7%) than the elder (23.5%,41.2%).The clinical signs of fever and wheezing/dyspnea were similar in these two groups.Conclusions Higher resistance in small and large airway and higher RR,lower FRC/kg and Crs/kg could be seen in the toddlers from 1 to 2 years of age with pneumonia caused by MP.And only the resistance in small airway was higher in the toddlers from 2 to 3 years of age.Pulmonary function test was a valuable way for surveillance of the alteration during acute phase in toddlers with pneumonia caused by MP.