avaliar as alteraes da mecnica respiratria e do volume corrente ( vc ) em 
 lactentes sibilantes em ventilao espontnea aps a realizao da tcnica de 
 expirao lenta e prolongada ( elpr ) . foram includos no estudo lactentes com histria de sibilncia recorrente e sem 
 exacerbaes nos 15 dias anteriores . para a avaliao da funo pulmonar , os 
 lactentes foram sedados e posicionados em decbito dorsal com mscara facial 
 acoplada a um pneumotacgrafo . as variveis da respirao corrente - vc e fr - e 
 da mecnica respiratria - complacncia do sistema respiratrio ( csr ) , resistncia 
 ( rsr ) e constante de tempo ( psr ) - foram mensuradas antes e aps a realizao de 
 trs sequncias consecutivas de elpr . foram avaliados 18 lactentes , com mdia de idade de 32  11 semanas . houve um 
 aumento significante no vc aps elpr ( 79,3  15,6 ml vs. 85,7  17,2 ml ; p = 
 0,009 ) , assim como uma reduo na fr ( 40,6  6,9 ciclos / min vs. 38,8  0,9 
 ciclos / min ; p = 0,042 ) . entretanto , no houve alteraes significantes nos valores 
 da mecnica respiratria ( csr : 11,0  3,1 ml / cmh2o vs. 11,3  2,7 
 ml / cmh2o ; rsr : 29,9  6,2 cmh2o  ml s ; e psr : 0,32  0,11 s vs. 0,34  0,12 s ; p > 0,05 para 
 todos ) . essa tcnica de fisioterapia respiratria  capaz de induzir alteraes 
 significativas no vc e na fr de lactentes com sibilncia recorrente , mesmo na 
 ausncia de exacerbaes . a manuteno das variveis da mecnica respiratria 
 indica que a tcnica  segura para ser aplicada nesse grupo de pacientes . estudos 
 com lactentes sintomticos so necessrios para quantificar os efeitos funcionais 
 da tcnica . the prolonged , slow expiratory ( pse ) maneuver is a respiratory therapy technique applied 
 in infants with airway obstruction and accumulation of secretion . the 
 benefits of different physiotherapy techniques have been described , 


  and 
 the same occurs with the pse maneuver . during the use of this technique , it was possible 
 to quantify the expiratory reserve volume mobilized , the induction of sighs and 
 maintenance of peak expiratory flow was confirmed and a decreased respiratory distress 
 was observed after application . 




  the evaluation of passive respiratory mechanics - respiratory system compliance ( crs ) , 
 resistance ( rrs ) and its time constant ( prs ) - has been used in studies of various 
 segments in infants , because in addition to obtaining reproducible measurements , it 
 assists in longitudinal monitoring of lung function and evaluation of therapeutic 
 interventions . crs and rrs can also help confirm the benefits of 
 respiratory physiotherapy due to altered pulmonary flow and lung volume after the 
 elimination of secretion . several studies on respiratory therapy in 
 patients under mechanical ventilation in icu used the evaluation of crs and 
 rrs . evaluation of airway resistance can also help detect bronchospasm induced by 
 respiratory therapy techniques . the application of chest vibration and " tapotement " 
 ( percussive tapping ) in individuals with lung disease and hypersecretion resulted in no 
 alteration in lung function , proving that this technique is safe and can be applied in 
 subjects with bronchial hyperreactivity . evaluation of tidal volume ( vt ) is one of the oldest and most simple 
 techniques to measure lung function in infants . vt has been 
 studied as an outcome for evaluating the efficacy of unconventional techniques of 
 respiratory therapy . the results so far , however , are controversial , with reports of 
 increased vt in some studies , and of maintenance in 
 others . the evaluation of respiratory mechanics and vt in infants breathing 
 spontaneously is not routinely measured in the clinical practice . these functional 
 variables , however , can be studied in specialized laboratories , and we believe that 
 these consist of objective outcomes and important factors in evaluating the 
 effectiveness of respiratory therapy . the objective of this study was to evaluate 
 changes in respiratory mechanics and vt in wheezing infants in spontaneous 
 ventilation after the application of pse maneuver . we conducted a cross - sectional study evaluation wheezing infants referred for pulmonary 
 function evaluation in the infant pulmonary function laboratory at the allergy , clinical 
 immunology , and rheumatology section of the department of pediatrics , federal university 
 of sao paulo , in so paulo , brazil . we included infants ( between 4 and 24 months of age ) with a history of recurrent 
 wheezing ( at least three episodes ) , without acute respiratory disease manifested in the 
 preceding 15 days . absence of acute respiratory disease was inferred from the absence of 
 corresponding clinical symptoms ( such as cough , wheezing and difficulty in breathing ) 
 and from the lack of consistent findings in the physical examination . we excluded those 
 with upper airway obstruction , preterm infants ( less than 37 weeks of gestational age ) , 
 infants with gastroesophageal reflux disease , infants who underwent thoracic and/or 
 abdominal surgery or who have been diagnosed with heart disease or neuropathy . to perform the pulmonary function test chloral hydrate was administered ( 60 - 80 mg / kg ) , according to the laboratory 
 routine and existing standardization . the infants were monitored using 
 a pulse oximeter ( dx 2405 ; dixtal biomedica , manaus , brazil ) and spo2 and hr 
 were evaluated . the infants were in the supine position with subtle cervical spine 
 extension , using a small pad in the scapular region , without lateralization of the head . a face mask connected to a pneumotachograph ( hans rudolph , kansas city , mo , usa ) was 
 attached to the infants ' face . in technical phase , the pse maneuver was performed with the infant in the supine 
 position , with the hypothenar region of one of the therapist 's hands positioned on the 
 chest , precisely below the suprasternal notch , and the hypothenar region of the other 
 hand placed on the abdomen above the umbilicus . at the end of the expiratory phase , the 
 compression of both hands was made , the hand on the chest being moved in craniocaudal 
 direction and the hand on the abdomen and hand in the caudocranial direction . the next 
 three or four inhalations subsequent to compression were restricted and squeezing motion 
 in the expiratory phase was continued in accordance with the technical 
 description . there were three sequences of pse maneuver ( named a , b 
 and c ) in a continuous period of 120 s ( figure 1 ) . the interval between the sequences was 30 s. the technique was always performed by the 
 same evaluator , trained and qualified to do so . the pse maneuver was performed during 
 the evaluation of vt , so the flow - volume curve was recorded constantly , 
 allowing measurement of the vt and its derivations - rr , pef and the ratio 
 between the time to reach the pef ( tme ) and expiratory time ( te ) . figure 1representation of the acceptability criteria of the expiratory curve 
 obtained in the evaluation of passive mechanics of the respiratory system by 
 the technique of single occlusion . in a , flow - volume curve : segment ad - 
 extrapolation for calculation of the time constant of the respiratory system ; 
 segment bc - linear portion of the curve  60% of the total , meaning the 
 relaxation of respiratory muscles during expiration . in b , crs , rrs and prs were the analyzed variables of respiratory mechanics using the airway 
 occlusion technique , according to existing recommendations . for these 
 measurements , the respiratory system is considered a one - compartment and linear model . the complete relaxation of the respiratory muscles in infants , necessary for the 
 evaluation of the passive respiratory mechanics , is achieved by inducing the 
 hering - breuer reflex , triggered by the rapid airway obstruction ( 1 s ) at the end of 
 normal inhalation . the presence of the linear segment of at least 60% of the expiratory 
 loop was inspected visually , as well as the lack of muscular activity by the plateau in 
 the pressure - time curve with a standard deviation < 0.1 at 100 ms ( figure 1 ) . at least three 
 acceptable maneuvers were performed as recommended , 


  and the average value 
 was recorded . different variables can be obtained from the analysis of vt , such as 
 inspiratory time , te , total respiratory time , pef , tme , rr and the tme / te ratio . for 
 this group of patients , the evaluation was restricted to vt , rr , pef and the 
 tme / te ratio , as these are variables that can be influenced by respiratory therapy 
 techniques . the tme / te ratio is one of the most studied variables in vt , as 
 it may reflect airway obstruction . the first phase ( pre - technique ) consisted of 
 measuring the vt and its derivations ( rr , pef and tme / te ratio ) for 60 s. 
 after the evaluation of the vt , the measurement of respiratory mechanics was 
 carried out . the second phase ( technique phase ) consisted of applying the pse maneuver 
 in three sequences of compression ( a , b and c ) for a period of 120 s. the technique was 
 performed during the measurement of vt ( figure 
 2 ) . the third phase ( post - technique ) consisted of the revaluation of the 
 vt for 60 s immediately after the application of the pse maneuver , 
 followed by the evaluation of the respiratory mechanics . figure 2representation of three sequences ( a , b , and c ) of the technique 
 prolonged , slow expiratory ( pse ) maneuver . all continuous variables analyzed presented normal distribution and were evaluated using 
 the shapiro - wilk test and therefore are presented as mean and standard deviation . the 
 mean of the 60 s of evaluation of the vt and the three measurements of 
 respiratory mechanics were used for pre - and post - technique comparison . we used the 
 student t test for dependent samples for the analysis of the tidal breathing 
 ( vt and rr ) and respiratory mechanics ( crs , rrs and prs ) variables between 
 the pre and post technique phases . the program used for the analysis was the statistical package for the social 
 sciences , version 14.0 ( spss inc . , of the 22 infants who started the protocol , 4 did not complete the study : one by 
 coughing during the examination and 3 by technical difficulties ( early awakening and 
 insufficient sedation ) . the mean age of the infants who completed the study was 32.2  
 11.4 weeks . variablesresultsage , weeks32.2  11.4height , cm68.0  4.3weight , kg 8.3  1.0number of wheezing attacks4.8  1.9sex male / female , n / n9/9avalues expressed as mean  sd , except where otherwise 
 indicated 
  values expressed as mean  sd , except where otherwise 
 indicated during the protocol , no infant showed signs of respiratory distress or expiratory 
 grunting . the spo2 remained over 93% throughout the tests , and hr remained 
 between 110 and 150 bpm in all infants evaluated . when comparing the pre and post technique phases , we observed a statistically 
 significant mean increase in vt ( p = 0.009 , figure 3 ) and vt corrected by height ( p = 0.01 , table 2 ) . a reduction was observed in rr from 40.6 
  6.9 breaths / min to 38.8  5.9 breaths / min after the technique ( p = 0.04 , table 2 ) . we 
 also observed a significant increase in the tme / te ratio ( p = 0.007 ) . there was no 
 significant change in the mean value of pef when compared to the pre and post - technique 
 phases ( table 2 ) . regarding respiratory mechanics , there was no statistically 
 significant changes in crs , rrs and prs ( table 2 ) . figure 3graphical representation of the variation in tidal volume before 
 ( pre - technique ) and after ( posttechnique ) applying the slow and progressive 
 expiration . table 2variables derived from tidal breathing and respiratory mechanics observed 
 in the pre - and posttechnique protocol . variablesphasesppre - techniquepost - techniquepef , ml / s140.5  19.2143.5  20.60.3vt , ml79.3  15.685.7  17.20.009vt , % previsto111.6  18.7120.1  17.70.013vt , ml / cm1.16  0.201.21 0 . 6.938.8  5.90.04crs , ml / cmh2o11.0  3.111.3  2.70.4rrs , cmh2o  ml s 
 29.9  6.230.8  7.10.4prs , s0.32  0.110.34  0.120.3vt : tidal volumetme : time to reach pefte : expiratory timecrs : respiratory system compliancerrs : respiratory system resistanceprs : time constant of the respiratory systemavalues expressed as mean  sd . : respiratory system compliance : respiratory system resistance : time constant of the respiratory system values expressed as mean  sd . the pse maneuver is a respiratory therapy technique described to promote bronchial 
 clearance in infants . the scientific arguments that prove the 
 effectiveness of the pse maneuver were based , for a long time , on the evaluation of 
 indirect variables , such as hr and spo2 . only recently 
 has the variation in expiratory reserve volume during pse maneuver been described more 
 objectively using the evaluation of pulmonary function variables . 


  however , 
 there are still questions about variations in vt and passive respiratory 
 mechanics immediately after the application of the pse maneuver in subjects breathing 
 spontaneously . after having studied the variations in volume and respiratory wheezing in 
 infants breathing spontaneously , we observed a significant increase in vt and 
 maintenance of the variables crs and rrs and after application of the pse maneuver . one possible explanation for the increase in vt is the reduction of airway 
 obstruction . it has been described that the reduction in the tme / te ratio is an indirect 
 form to determine airway obstruction . thus , we infer that there was a 
 decrease in bronchial obstruction in the patients studied by the increase in the tme / te 
 ratio ( > 0.30 ) after the pse maneuver . this reduction in the obstructive process is 
 due to the thoracoabdominal compression performed during the pse maneuvers , where the 
 aim is to prolong the expiratory phase and eliminate the trapped air . if this process is 
 successful , the reduction of the expiratory reserve volume is expected , and it is able 
 to allow an increase in vt . in addition to finding an increase in the tme / te 
 ratio , our group has previously described that the pse maneuver contributes in removing 
 over 50% of the expiratory reserve volume , 


  confirming the results of the 
 decrease in obstruction . another factor that would justify the increase in vt in the infants studied 
 here is the induction of sighs , characterized as breaths in which there is an increase 
 greater than 100% in vt . recently , we have shown that the pse maneuver favors 
 the induction of sighs , 


  and that it is already known that sighs act by 
 recruiting alveoli and increasing the vt . it is important to 
 point out that the variation observed in our study in the values of vt , 
 albeit small , is probably clinically relevant . the instability of the rib cage , 
 routinely observed in infants , makes those more susceptible to lung volume reduction , 
 and maneuvers that increase vt become clinically relevant . we observed an increase of nearly 10% in vt after applying three sequences of 
 the pse maneuver . in the clinical practice , however , physical therapists , when using the 
 pse maneuver technique , perform a greater number of maneuvers , basing the number of 
 repetitions on the improvement in pulmonary auscultation . 


  thus , it is 
 unlikely that the actual increase of vt determined by the pse maneuver 
 technique in the daily practice be much more expressive than the one found in our 
 study . rrs in our study was maintained after the application of the pse maneuver , in 
 disagreement with studies in patients on mechanical ventilation . this 
 finding can be explained by evaluating patients breathing spontaneously , without 
 hypersecretion and therefore without change in the rrs at the beginning of the 
 protocol . it is described that 
 techniques with intense mechanical vibrations in the chest , such as " tapotement " 
 ( percussive tapping ) and vibration , can aggravate bronchospasm , evidenced by the 
 reduction in fev1 and pef . there is no description of the 
 unconventional techniques of physiotherapy favoring bronchospasm , due to the fact that 
 these techniques cause no abrupt mechanical vibrations in the chest . in our study , we 
 observed no change in either rrs or pef , confirming that pse maneuver did not induce 
 bronchospasm in this group of wheezing infants , and we consider it a safe technique to 
 perform even in individuals prone to bronchospasm . a group of authors , when evaluating 
 unconventional techniques of respiratory therapy similar to that applied in this study , 
 observed no significant changes in pef . the maintenance of the values of crs in this study can be justified due to fact that the 
 initial values were within normal limits , 




  and to the lack of pulmonary 
 hypersecretion . authors who observed that variation in respiratory function after 
 physical therapy in mechanically ventilated patients described the secretion clearance 
 as the main reason . our study was limited by the fact that patients are not in exacerbation or presented 
 hypersecretion . individuals with hypersecretion were not selected , due to the fact that , 
 in addition to the interference of this condition in the variables analyzed , the 
 secretion could also compromise the safety of the infant , since the sedation associated 
 with hypersecretion aggravates airway obstruction in patients breathing spontaneously . the short application time of pse maneuver ( three sequences ) and functional revaluation 
 soon after its completion are other limitations to our study . this , however , could 
 hardly be altered due to the short time of sedation induced by chloral hydrate . even 
 with a small evaluation time , we observed significant changes in vt and we 
 can speculate that the performance of a greater number of sequences of the pse maneuver 
 could increase the differences found . we conclude that the application of pse maneuver 
 in wheezing infants is able to induce changes in pulmonary function with increased 
 vt and reduced rr . the maintenance of the airway resistance values demonstrates that 
 the pse maneuver technique is safe for application in infants with propensity to 
 bronchospasm .
objective : to evaluate changes in respiratory mechanics and tidal volume ( vt ) in 
 wheezing infants in spontaneous ventilation after performing the technique known 
 as the prolonged , slow expiratory ( pse ) maneuver . 
 methods : we included infants with a history of recurrent wheezing and who had had no 
 exacerbations in the previous 15 days . for the assessment of the pulmonary 
 function , the infants were sedated and placed in the supine position , and a face 
 mask was used and connected to a pneumotachograph . the variables of tidal 
 breathing ( vt and rr ) as well as those of respiratory 
 mechanics - respiratory system compliance ( crs ) , respiratory system resistance 
 ( rrs ) , and the respiratory system time constant ( prs)-were measured before and 
 after three consecutive pse maneuvers . results : we evaluated 18 infants . 
 the mean age was 32  11 weeks . 
 after pse , there was a 
 significant increase in vt ( 79.3  15.6 ml vs. 85.7  17.2 ml ; p = 
 0.009 ) and a significant decrease in rr ( 40.6  6.9 breaths / min vs. 38.8  0,9 
 breaths / min ; p = 0.042 ) . 
 however , no significant differences were found in the 
 variables of respiratory mechanics ( crs : 11.0  3.1 ml / cmh2o vs. 11.3  
 2.7 ml / cmh2o ; rrs : 29.9  6.2 cmh2o  ml1 
 s1 vs. 30.8  7.1 cmh2o  ml1  
 s1 ; and prs : 0.32  0.11 s vs. 0.34 0.12 s ; p > 0.05 for all ) . 
 conclusions : this respiratory therapy technique is able to induce significant changes in 
 vt and rr in infants with recurrent wheezing , even in the absence of 
 exacerbations . the fact that the variables related to respiratory mechanics 
 remained unchanged indicates that the technique is safe to apply in this group of 
 patients 
 . studies involving symptomatic infants are needed in order to quantify 
 the functional effects of the technique .