The Roles Of Tidal Breath Flow-volume Loop In Monitoring Lung Function Of Preterm Infants With Bronchopulmonary Dysplasia

Objective: To investigate the roles of tidal breath flow-volume loop(TBFVL)in monitoring lung function of preterm infants with differentdegrees’ bronchopulmonary dysplasia (BPD).Methods: One hundred and eighty-eight healthy term infants (termgroup)and113preterm infants (no-BPD preterm group) with no-BPD andheart&lung disease-free in Shenzhen children’ hospital from Jan2011toOct2012were erolled in the study as control,106BPD infants as theobservation group which was divided into mile, moderate and severe groupaccording to the definition of BPD.Lung function was tested inpostmenstrual age (PMA)44weeks and retested in PMA76weeks. Theparameters of lung function test included TBFVL, functional residualcapacity (FRC) and lung clearance index (LCI).Results:(1)The shape of TBFVL showed that in BPD groups: in PMA44weeks, the expiratory descending branch descended sharply, in mildBPD it was slightly gradient than in no-BPD group, while in moderate andsevere groups it depressed to volume axis. In severe BPD group the peak expiratory flow (TPEF) was marked higher than the peak inspiratory flow(TPIF).In PMA76weeks, the expiratory descending branch in mild BPDgroup descended slowly, while in moderate BPD group descended sharply,in severe BPD depressed to volume axis.TPEF in severe BPD group wasstill obviously higher.(2) The value of parameters:In PMA44weeks, RR、TPIF in moderateand severe BPD groups 【(56.79±8.91)、(58.11±10.12)times/min，(60.91±20.54)、(75.30±14.43)ml/s】 were higher than no-BPD group【(49.91±12.78)times/min、(52.39±20.12)ml/s】, P<0.05，TPIF in severeBPD group was higher than in mild BPD group, P<0.05, RR、TPIF in mildBPD group 【(52.97±12.59)times/min、(55.27±21.61)ml/s】 had nostatistical significant differences with no-BPD group, P>0.05.Tpef/Te inmoderate and severe BPD groups【(20.36%±9.15%)、(18.07%±5.28%) vs(28.79%±9.06%)】were lower than no-BPD group, P<0.01, Tpef/Te insevere BPD group was lower than mild BPD group (24.29%±12.80%),P<0.05, there was no statistical significant differences between mild BPDgroup and no-BPD group, P>0.05. TPEF in severe BPD group【(85.33±11.48)ml/s】was higher than no-BPD group and mild BPD group【(58.55±23.09)、(56.03±24.93) ml/s】,P<0.05. For TV, there was nostatistical significant differences between each group【(24.80±9.14)、(23.37±8.78)、(22.17±8.67) and (22.05±3.36)ml, P>0.05】.FRCin moderate and severe BPD groupwere lower than no-BPD group【(15.37±3.14)、(15.06±3.85) vs (19.96±5.04) ml/kg】, P<0.01,there was no statistical significant differences between mild BPD group【(17.74±5.47)ml/kg】and no-BPD group, P>0.05.Only in moderate BPDgroup,LCI was higher than in no-BPD group【(9.93±3.34) vs(8.36±2.78)】, P<0.05.In PMA76weeks, Tpef/Te in mild、moderate andsevere BPD group【s20.80%±3.03%、18.07%±2.98%、16.73±2.50%】wereall lower than no-BPD group (36.06%±5.06%)， P<0.05； LCI【(9.42±1.61)、(10.33±1.72)、(10.89±1.88)】were all higher than no-BPDgroup(7.98±1.61),P<0.05;except mild BPD group,FRC in both moderateand severe BPD group【s(19.26±2.16)、(19.19±2.15)ml/kg】were all lowerthan no-BPD group【(21.72±3.12)ml/kg, P<0.05】;TV in both mild andmoderate BPD groups 【(71.40±6.32)、(70.14±8.60)ml】were lower thanno-BPD group【(75.79±5.64)ml,P<0.05】,TPEF in severe BPD group wasstill higher than no-BPD group【(162.90±16.50) vs (133.70±21.62)ml/s，P<0.05】,RR and TPIF had no statistical significant difference in groups(P>0.05).(3) Comparison of different parameters between PMA44weeks andPMA76weeks: In each group, RR in PMA76weeks was lower than RRin PMA44weeks【no-BPD group:(36.06±5.06) vs (49.91±12.78)times/min, mild BPD:(36.50±6.79) vs (52.97±12.59)times/min, moderate BPD:(37.05±5.70) vs (56.79±8.91)times/min, severa BPD:(38.61±6.17) vs(58.11±10.12)times/min】,TPIF、TPEF、FRC in PMA76weeks were higher than in PMA44weeks in each group【respectively, no-BPD group:(133.70±21.62) vs (52.39±20.12)ml/s,(141.08±24.79) vs (58.55±23.09)ml/s and (21.72±3.12) vs (19.96±5.04)ml/kg; mild BPD:(129.33±17.25)vs (55.27±21.61)ml/s,(147.02±22.28) vs (56.03±24.93)ml/s and(21.14±2.82) vs (17.74±5.47)ml/kg; moderate BPD:(126.52±19.73) vs(60.91±20.54)ml/s,(149.87±22.24) vs (69.59±33.17)ml/s,(19.26±2.16) vs(15.37±3.14)ml/kg; moderate BPD:(124.53±20.62) vs (75.30±14.43)ml/s,(162.90±16.50) vs (85.33±11.48)ml/s and (19.19±2.15) vs (15.06±3.85)ml/kg】,P<0.05; except severe BPD group 【(16.73%±2.50%) vs(18.07%±5.28%)】; for each group,Tpef/Te in PMA76weeks wererespectively lower than in PMA44weeks【no-BPD group:(23.17%±4.32%) vs (28.79%±9.06%), mild BPD:(20.80%±3.03%) vs (24.29%±12.80%), moderate BPD:(18.07%±2.98%) vs (20.36%±9.15%)】,P<0.05;for LCI,there was no statistical significant difference betweenPMA44weeks and PMA76weeks in each group【(7.98±1.61) vs(8.36±2.78)、(9.42±1.61) vs (9.01±3.22)、(10.33±1.88) vs (9.93±3.34) and(10.89±1.88) vs (10.31±2.85), respectively, P>0.05】.(4) Analysis of correlationships between the degree of BPD andparameters: In PMA44weeks, RR、Tpef/Te、TPEF、TPIF、TEF75、FRChad significant correlationships with degree of BPD (all P<0.05),TV、LCIhad no significant correlationship with degree of BPD(all P>0.05)。InPMA76weeks,Tpef/Te、 TEF75、 FRC、 LCI had significant correlationships with degree of BPD(all P<0.05),while RR、TV、TPIF、TPEF had no significant correlationship with degree of BPD (all P>0.05)。Conclusion: TBFVL can directly reflect the characteristic of BPD ofdifferent degree.TBFVL combined with FRC and LCI can reflect theseverity of big and small airway construction and the lung development inBPD infants systematicly and comprehensively, and should be used inclinical for lung function follow-up.