they are also 
 known as " ambu " , which is the trademark of a resuscitator and the term used as a 
 synonym for mr by professionals in brazil and other countries . 




 
being used in icus in order optimize oxygenation and facilitate the 
 removal of secretion in patients on invasive mechanical ventilation , mrs are also 
 used for intra - hospital transport and as a source of temporary ventilation in 
 intubated and nonintubated patients . 




 
on the basis of their inflation mechanism , mrs can be classified as 
 self - inflating or flow - inflating , 




  the former being the most commonly used type in icus in brazil .
self - inflating mrs , which is the type of mr evaluated in the present study , consist 
 of a compressible self - inflating bag , an inflating valve , and an 
 inspiratory / expiratory valve ( patient valve ; figure 
 1 ) . 




 
when the bag is compressed by the operator , the patient valve occludes 
 the expiratory port and allows the air within the bag to flow to the patient ; when 
 the pressure within the bag ceases , the patient valve returns to its normal 
 position , occluding the communication of the bag with the patient and allowing the 
 air coming from the patient to be exhaled through the expiratory port .
a drop in 
 pressure within the bag during exhalation causes the inflating valve to open , 
 allowing the air to enter the bag . 




 
additional components of this type of mr include 




  a device for enriching the oxygen mixture , a positive end - expiratory 
 pressure ( peep ) valve , and a pressure - limiting valve ( plv ) , the use of which in 
 adult patients is not in accordance with the american society for testing and 
 materials ( astm ) criteria . 


 

figure a 
 illustrates all of the components of the resuscitator , and figure b 
 illustrates only the patient connection port , highlighting the 
 positioning of the patient valve during inhalation and exhalation .
a : 
 connection port of the oxygen reservoir with an inflation valve ; b : 
 inflating bag ; c : patient valve ; d : pressure - limiting valve ( acts only 
 during inhalation ) ; e : expiratory port ; and f : patient connection 
 port . 
  in the literature , there are studies evaluating the performance and safety of mrs 
 available in other countries in accordance with international technical 
 standards . 




 
the objective of the present study was to evaluate the 
 characteristics and performance of some of the self - inflating mrs for use in adult 
 patients that are available in the brazilian market , in accordance with 
 international standards .
the present study was approved by the research ethics committee of the university of 
 so paulo school of medicine hospital das clnicas and was carried 
 out in the experimental mechanical ventilation laboratory of the department of 
 pulmonology of the same institution in 2006 .
moriya , so 
 paulo ; oxigel , so paulo ; protec equipamentos mdico - hospitalares , so paulo ; rwr 
 equipamentos hospitalares , so bernardo do campo ; and unitec ind . e com
, so paulo ) , two were manufactured in denmark 
 ( ambu silicone resuscitator and ambuspur ; ambu a / s , 
 ballerup , denmark ) , and one was manufactured in the usa ( hudson rci(r ) 
 lifesaver ; hudson rci , durham , nc , usa ) .
all of the models are still being 
 marketed , and the updates of the mrs since the present study was carried out to this 
 writing are described in table 1 . 
 table 1 characteristics of the manual resuscitators for adults as described 
 by the manufacturers.nd : no data .
note : from 2006 to this writing , devices 1 , 2 , 3 , 4 , and 
 7 did not change significantly . in device 5 , the current patient 
 connection port is a swivel . in device 6 ,
the color of the silicone 
 was changed from blue to transparent . in device 8
, the capacity of 
 the bag was increased from 1,000 to 1,500 ml . 
 
note : from 2006 to this writing , devices 1 , 2 , 3 , 4 , and 
 7 did not change significantly . in device 5 , the current patient 
 connection port is a swivel . in device 6 , the color of the silicone 
 was changed from blue to transparent . in device 8 , the capacity of 
 the bag was increased from 1,000 to 1,500 ml . since there are no brazilian standards defining the characteristics for the 
 manufacture and marketing of mrs , the present evaluation used the astm criteria , 
 designation f920 - 93 , 


  which are equivalent to the international organization for 
 standardization 8382 criteria , 


  used in other countries . using a respiratory system simulator ,
the 
 following criteria were evaluated : resistance imposed by the patient valve during 
 the inspiratory and expiratory phases ; functioning of the plv ; and tidal volume 
 ( vt ) delivered by the mr . in accordance with the astm criteria , the 
 following specifications should be met : a drop < 5 cmh2o in 
 inspiratory and expiratory pressure in the presence of a flow of 50 l / min , leading 
 to resistance < 6 cmh2o .
l . s ; the use of 
 a plv is not mandatory for mrs for adults , but , if this valve is available , it 
 should be possible to close it ; a vt  600 ml should be delivered to 
 adult patients ( weight  40 kg ) , with resistance of 20 cmh2o . 

s and compliance of 0.02 l / cmh2o , using 
 the one - handed technique ( maximum hand size , 185 mm ) .
the measurement system consisted of a plastic tube to which pressure and flow sensors 
 were connected ( figure 2 ) .
the signals from 
 the sensors were amplified and stored on a computer for subsequent analysis with the 
 labview software ( national instruments , tx , usa ) .
the signal 
 sampling frequency was 200 hz . 
 figure 2schematic representation of the experimental system . 1 : proximal or 
 distal flow sensor ; 2 : pressure sensor ; 3 : resistor ; and 4 : alveolar 
 pressure sensor . 
  in order to measure inspiratory and expiratory resistance , a mechanical ventilator 
 ( bear 5
; bear medical systems , riverside , ca , usa ) was connected to 
 one end of the plastic tube with the sensors ( figure 
 2 ) .
the ventilator was set to the controlled volume mode , with a constant 
 inspiratory flow of 60 l / min and a peep of zero cmh2o . in the evaluation 
 of expiratory resistance
, the patient connection port of the mr was attached to the 
 other end of the plastic tube , and the air from the ventilator left through the 
 expiratory port into room air ( figure 2 ) . in 
 the evaluation of inspiratory resistance ,
the mr was disassembled and only the 
 proximal portion of the set , without the bag , was used ( figure 2 ) .
the part of the mr that is connected to the bag was 
 attached to the other end of the plastic tube , and the air left through the patient 
 connection port to the environment .
the 
 ambu silicone resuscitator was not tested because it could not be 
 disassembled .
the two resistances were calculated as the difference between the 
 proximal and distal pressure to the valve ( distal pressure was not measured , because 
 it was equal to zero , since the system was open to the environment ) , divided by the 
 measured flow .
for the testing of vt , the mrs were connected to the plastic tube with the 
 sensors , and this tube was connected to a tracheal cannula of 8.5 mm in diameter 
 ( rusch , montevideo , uruguay ) , the distal portion of which , with the cuff inflated , 
 was fitted into another plastic tube that was connected to a respiratory system 
 simulator ( ttl 2600 ; michigan instruments , grands 
 rapids , mi , usa ; figure 2 ) .
the simulator 
 allowed the compliance of the bellows to be set with springs ; resistance was set 
 with nonlinear resistors .
four volunteer icu physiotherapists in the city of so paulo ( two males and two 
 females ) operated the mrs .
the size of the dominant hand ( from the wrist to the tip 
 of the middle finger ) was 200 mm for male1 , 188 mm for male 2 , 175 mm for female 1 , 
 and 160 mm for female 2 .
the physiotherapists were instructed to inflate the model 
 as if they were ventilating a patient , first using the one - handed technique and then 
 using the two - handed technique , with the eight mrs , which were tested in a random 
 sequence , under two conditions of resistance and compliance : 1 ) " astm " 
 condition - compliance of 0.02 l / cmh2o and resistance of 20 
 cmh2o .
l . s , in accordance with the astm 
 criteria ; 


  and 2 ) " normal " condition - compliance of 0.05 l / cmh2o and 
 resistance of 5 cmh2o .
s , simulating a 
 patient without lung disease . in order to calculate vt ,
three respiratory cycles were analyzed , all of 
 which were randomly selected among the recorded cycles ( a minimum of 10 per test 
 condition ) . since each volunteer ( totaling four ) handled eight mrs , using the 
 one - handed and two - handed techniques , in two distinct clinical settings ( astm 
 condition and normal condition ) , 128 tests were performed .
of the eight mrs , five were equipped with a plv and were submitted to this test .
the 
 ventilator , connected to one end of the measurement system ( with a flow sensor and a 
 pressure sensor ) , was set to the controlled volume mode , with an inspiratory flow of 
 20 l / min , a vt of 1,800 ml , and a peep of zero cmh2o .
a part 
 of the mr was connected to the other end , as were another ( distal ) flow sensor and 
 the simulator , in sequence ( figure 2 ) .
we determined the 
 pressure at which the plv opened and allowed air leaks ( a time point that could be 
 identified when the flow in the distal sensor decreased in relation to that in the 
 proximal sensor ) , this pressure being referred to as " opening pressure " , and 
 determined the pressure at which all air sent by the ventilator passed only through 
 the plv ( a time point at which the distal flow was equal to zero ) , this pressure 
 being referred to as " maximal pressure " .
the functioning of the valve was considered 
 appropriate if the opening pressure was within the pressure interval suggested by 
 the manufacturers , in general , values greater than 35 - 40 cmh2o ( table 1 ) . for each mr
, only one inspiratory and expiratory resistance value was shown , because 
 the variation between the cycles was negligible .
the vt values were expressed as mean and 
 standard deviation and were evaluated by multivariate analysis using a mixed linear 
 regression model for each of the four conditions studied : vt generated 
 with the one - handed technique under the astm and normal conditions ; and 
 vt generated with the two - handed technique under the same two 
 conditions .
post 
 hoc tests with sidak correction were used for comparisons of the vt 
 values among the physiotherapists and among the mrs . for this analysis
, we used the 
 statistical package for the social sciences , version 17 for windows ( spss inc .
the most common type of patient valve was a diaphragm , and the most common 
 bag material was silicone .
the capacity of the bag of each mr varied ( 1,000 - 2,500 
 ml ) .
the three imported mrs did not have a plv , which was a feature of the five 
 brazilian - made mrs , and , in the mr manufactured by rwr , the plv could be closed 
 without there being any leaks .
another difference observed between the imported and 
 the brazilian - made mrs was that the patient connection port was fixed in the five 
 brazilian - made mrs , whereas , in the imported ones , this connection port was a " 360 
 swivel " . 

table 2 describes the results of the tests 
 evaluating the resistances of the patient valve during inhalation and exhalation , as 
 well as the functioning of the plv . only in the protec rm
did expiratory resistance 
 exceeded the limit set by the astm criteria ( < 6 cmh2o . 

s. in the other mrs tested , the resistances met 
 those criteria , the highest inspiratory resistance being found in the oxigel mr 
 ( 5.69 cmh2o .
l . s. the plv , a feature of 
 five of the mrs , opened at low pressures ( < 17 cmh2o ) , and the maximal 
 pressure was 32.0 - 55.9 cmh2o . 

table 2 inspiratory and expiratory resistance of the patient valve and 
 evaluation of the pressure - limiting valve . 
 
the mean delivered vt values , by mr ( table 3 ) and by physiotherapist ( table 
 e1 , available online at http://www.jornaldepneumologia.com.br/detalhe_artigo.asp?id=2212 ) , 
 varied . in the situations evaluated ( handling of the eight mrs , with the use of the 
 one - handed and two - handed techniques , in two distinct clinical settings - astm 
 condition and normal condition ) ,
there were significant differences ( p < 0.001 ) 
 among the mrs and among the physiotherapists .
all of the mrs , whenever the 
 one - handed technique was used under the astm condition , delivered a lower 
 vt than that recommended by the astm (  600 ml ) . only the two models 
 of mr manufactured by ambu a / s delivered a vt  600 ml when the 
 one - handed technique was used , but only during the simulation of the normal clinical 
 condition .
even when the two - handed technique was used , the mrs manufactured by 
 oxigel and rwr did not deliver the minimal vt under the astm clinical 
 condition , whereas the mrs manufactured by protec and unitec , regardless of the 
 clinical setting simulated , delivered a vt < 600 ml . 

table 3 tidal volume ( vt ) generated under the normal condition and under the 
 american society of testing materials ( astm ) condition.aavalues expressed as mean  sd , on the basis of 3 measurements , in 
 ml.bcompliance = 0.02 l / cmh2o ; and resistance = 20 
 cmh2o .
l . s 
 ccompliance = 0.05 l / cmh2o ; and resistance = 5 cmh2o . 

s. p < 0.05 in relation to the 
 resuscitators that did not have a valve*ambu**ambu s ; and***hudson / rci 
  values expressed as mean  sd , on the basis of 3 measurements , in 
 ml .
l . s 
  compliance = 0.05 l / cmh2o ; and resistance = 5 cmh2o . 

s. p < 0.05 in relation to the 
 resuscitators that did not have a valve in addition , when we observe the results reported in table 3 , we can see that the vt values generated under the 
 normal clinical condition were , in general , higher than were those generated under 
 the astm condition , which simulates a pulmonary condition with lower compliance and 
 higher resistance , and that most of the vt values obtained with the mrs 
 that did not have a plv were higher than were those obtained with the mrs that had a 
 plv .
the main findings of the present study can be summarized as follows : 1 ) the 
 ( inspiratory and expiratory ) resistances of the patient valve met the astm criteria 
 in all but one of the mrs tested ; 2 ) the eight rms evaluated did not deliver the 
 minimal vt under conditions standardized by those same criteria 
 ( vt  600 ml , with the use of the one - handed technique , under the 
 astm clinical condition ) ; 3 ) the use of the two - handed technique did not solve the 
 problem in four mrs ( vt remained < 600 ml ) ; and 4 ) the plv present in 
 the brazilian - made mrs usually led to the delivery of a lower vt than 
 that delivered by the mrs that did not have a plv . in brazil , there have been few published studies evaluating mrs for adult patients , 
 commonly used in icus in the country . 






 
although those studies investigated important characteristics , such as 
 the oxygen fraction delivered by mrs with and without an oxygen reservoir , the 
 present study evaluated other equally important properties that had not yet been 
 reported in the national literature .
regarding the evaluation of resistance of the patient valve during inhalation and 
 exhalation , all of the mrs tested were within the specifications of the astm , except 
 for the protec mr , in which expiratory resistance was 7.91 cmh2o . 

s. this result is not surprising , given that 
 international studies had described mrs in which the resistances of the patient 
 valve were higher than recommended . 




 
it is of note that higher expiratory pressure translates to longer 
 exhalation , which can cause air trapping ( auto - peep ) and risk of 
 barotrauma , 


  especially when the mr is handled at a high respiratory rate and a high 
 vt . for the evaluation of the vt generated with the one - handed and two - handed 
 techniques , we selected male and female volunteers , because it is known that the 
 vt obtained varies with the gender of the operator ( vt is 
 lower for female operators ) . 


 
mean vt varied greatly among the mrs tested , a finding that 
 had been reported in other studies . 


 
we observed that some brazilian - made mrs delivered a low vt 
 even with the use of the two - handed technique , which generates a higher 
 vt than does the one - handed technique . 






 
other authors had reported , even in normal compliance simulations , 
 vt values lower than 600 ml . 


  however , in the study by mazzolini et al . , 


  which evaluated 16 disposable mrs manufactured abroad , only three mrs 
 did not deliver the minimal vt recommended by the astm (  600ml ) .
one 
 factor that seems to have led to increased vt values was the size of the 
 hands of one of the physiotherapists ( 200 mm , a larger size than that recommended by 
 the criteria , male 1 , table e1 , available 
 online at http://www.jornaldepneumologia.com.br/detalhe_artigo.asp?id=2212 ) . 

this association between delivered vt and hand size has been described by 
 other authors . 








 
factors that could lead to low volumes are the size 


  and the material of the bag of the resuscitator tested . 


  the volume of air in the bag is not totally delivered to the patient 
 when the bag is compressed , and , in general , the volume of the bag should be twice 
 the volume to be delivered . 


  a bag made of a material that is not very compliant ( such as polyvinyl ) 
 can lead to a lower vt . 


  in our study , the mr that delivered the lowest vt ( unitec ) 
 had the bag with the lowest volume , and , in addition , this bag was made of 
 polyvinyl .
it is of note that vt was generally lower from the 
 brazilian - made mrs than from the imported ones , except for the mr manufactured by 
 rwr , which generated a higher vt , probably because the capacity of the 
 bag was 2,500 ml .
one could question whether the low vt values found for some of the mrs 
 tested resulted from fatigue of the volunteers .
however , the study by hess et 
 al . , 


  which evaluated the effect of fatigue caused by ventilation with a mr 
 for 30 min under low compliance ( 20 ml / cmh2o ) , found no reduction in 
 vt after 30 minutes for the 14 volunteers evaluated . considering 
 that , in our study , total test time for each of the mrs was approximately one 
 minute , which would total eight minutes for each of the four situations evaluated 
 ( two impedance values with the use of the one - handed and two - handed techniques ) , and 
 that there was a rest break between each measurement , it seems unlikely that the 
 occurrence of fatigue would have influenced the results .
as expected , the vt obtained in the simulation of a " normal " patient was 
 higher than that found in the tests using the compliance and resistance settings 
 established by the astm criteria , which simulated a patient with decreased 
 compliance and increased resistance , which are proven to lead to a lower 
 vt . 


 
the presence of a plv in the brazilian - made mrs possibly impaired their performance . 

all of the brazilian - made mrs had a plv , and in only one of them could the valve be 
 closed .
the valves of all of them initially opened at low pressures , the values of 
 which were below the specified value , causing leaks during inflation , which can 
 partially explain the lower vt obtained with the rms that had a plv .
this 
 result can be considered a severe fault , because it can prevent appropriate 
 ventilation in patients with decreased lung compliance or with increased airway 
 resistance , such as those with pulmonary edema and those with asthma attacks , 
 respectively . according to some authors
, the presence of plv does not bring additional safety to 
 adult patients , 


  given that the risk of barotrauma is not associated only with high peak 
 pressures during inhalation . 


 
in fact , the astm criteria 


  dispense with the use of a pressure - regulating device for mrs for 
 adults and determine that , if this valve is present , it should be possible to lock 
 it and its closing mechanism should be quite evident to the operator . 




  even in mrs for neonatal / pediatric patients , for which the presence of 
 this valve is recommended in order to limit pressure to values below 40  5 
 cmh2o , 




  malfunctioning of the plv can also impair ventilation . 


 
we consider limitations of our study the fact that all tests were performed using 
 only one unit of each mr ( however , all mrs were brand - new ) ; that resistance of the 
 patient valve was tested at a flow of 60 l / min , rather than of 50 l / min ( value 
 recommended by the astm ) , which can hinder the comparison with other studies ; and 
 that , since the present study was carried out in 2006 , some mr models underwent 
 changes ( table 1 ) , which might have altered 
 their performances .
this should be probably true for the mr manufactured by unitec , 
 in which the capacity of the bag was significantly increased ( table 1 ) . despite the limitations of this study
, we believe that important deficiencies of the 
 mrs manufactured in brazil are reported , especially those regarding the functioning 
 of the plv ( most could not be locked and opened early ) , deficiencies that , in some 
 clinical conditions , can impair ventilation in critically ill patients .
our results 
 indicate that , in order to deliver an appropriate vt , it is necessary 
 that both hands be used to compress the mr bag and that , when allowed by the mr , the 
 plv be kept closed .
we believe that the results obtained in the present study can 
 aid in performing future tests and in improving the brazilian - made mrs .
  avaliar o desempenho de reanimadores manuais ( rms ) utilizados no brasil 
 conforme critrios definidos por uma norma internacional .
  utilizando um simulador do sistema respiratrio , oito rms manuais ( cinco 
 produzidos no brasil e trs importados ) foram avaliados em relao a 
 resistncia inspiratria e expiratria da vlvula para o paciente ; 
 funcionamento da vlvula limitadora de presso ; e volume corrente 
 ( vt ) gerado por quatro fisioterapeutas voluntrios , 
 utilizando uma ou duas mos . para a realizao e anlise dos testes , foram 
 utilizados critrios sugeridos pela norma da american society for 
 testing and materials ( astm ) f920 - 93 .
, presente em cinco rms , abriu em baixas presses ( < 17 
 cmh2o ) , e a presso mxima variou de 32,0 - 55,9 
 cmh2o .
os valores mdios de vt utilizando uma mo 
 foram inferiores ao sugerido pela astm ( 600 ml ) .
o vt mdio , nas 
 situaes estudadas , foi geralmente menor nos rms nacionais com vlvula 
 limitadora de presso .
as resistncias impostas pela vlvula do paciente esto de acordo com os 
 critrios da astm , com exceo de um rm . as vlvulas limitadoras de presso 
 dos rms nacionais geralmente abrem em baixas presses , determinando o 
 fornecimento de um menor vt nas situaes estudadas , 
 principalmente com o uso de uma mo , o que sugere que a ventilao deva ser 
 feita com as duas mos e a vlvula limitadora de presso deva ser fechada 
 sempre que possvel .
so tambm conhecidos como ressuscitadores manuais ou " ambu " que  uma marca 
 registrada de reanimador e denominao utilizada como sinnimo de rm por 
 profissionais no brasil e em outros pases . 




 
os rms so utilizados em utis para otimizar a oxigenao e 
 facilitar a remoo de secreo em pacientes em ventilao mecnica invasiva , 
 para transporte intra - hospitalar , e como forma de ventilao temporria em 
 pacientes intubados ou no . 




 
os rms podem ser classificados , de acordo com sua forma de 
 enchimento , em autoinflveis ou inflveis por fluxo , 




  sendo que o primeiro  o tipo mais utilizado nas utis 
 brasileiras .
o rm autoinflvel , que  o tipo que foi avaliado no presente estudo ,  composto 
 de um balo compressvel e autoinflvel , uma vlvula para o reenchimento do 
 balo e uma vlvula inspiratria / expiratria ( vlvula do paciente ; figura 1 ) . 




 
quando o balo  comprimido pelo operador , a vlvula do paciente 
 oclui a porta expiratria e permite a passagem do ar no interior do balo para o 
 paciente ; quando cessa a presso no interior do balo a vlvula retorna a sua 
 posio normal , ocluindo a comunicao do balo com o paciente e permitindo a 
 exalao do ar que vem do paciente pela porta expiratria . a queda de presso no 
 interior do balo durante a expirao determina a abertura da vlvula de 
 reenchimento , permitindo a entrada de ar para o balo . 




 
componentes adicionais desse tipo de rm incluem 




  um dispositivo para enriquecer a mistura de oxignio , uma vlvula 
 de positive end - expiratory pressure ( peep , presso expiratria 
 final positiva ) e uma vlvula limitadora de presso ( vlp ) cujo uso , para 
 pacientes adultos , no  recomendado pela american society for testing 
 and materials ( astm ) . 


 

a figura a 
 ilustra todos os componentes do reanimador , e a figura b ilustra 
 apenas o conector do paciente , com destaque do posicionamento da 
 vlvula do paciente durante a inspirao e expirao .
a : conexo 
 para o reservatrio de oxignio com vlvula de reenchimento ; b : 
 bolsa inflvel ; c : vlvula do paciente ; d : vlvula limitadora de 
 presso ( atua somente na inspirao ) ; e : porta exalatria ; e f : 
 conexo para o paciente . 
 
na literatura , encontram - se estudos que avaliaram o desempenho e a segurana de 
 rms disponveis em outros pases de acordo com quesitos exigidos por normas 
 tcnicas internacionais . 




  a realizao de estudos comparativos permite identificar problemas 
 e aperfeioar esses dispositivos .
nosso objetivo , no presente estudo , foi 
 avaliar as caractersticas e o desempenho de alguns dos rms autoinflveis , para 
 uso em pacientes adultos , disponveis no mercado nacional , seguindo alguns 
 quesitos estabelecidos por uma norma internacional .
o estudo foi aprovado pelo comit de tica em pesquisa do hospital das clnicas 
 da faculdade de medicina da universidade de so paulo e realizado no laboratrio 
 experimental de ventilao mecnica da disciplina de pneumologia da mesma 
 instituio em 2006 .
moriya , so 
 paulo ; oxigel , so paulo ; protec equipamentos mdico - hospitalares , so paulo ; 
 rwr equipamentos hospitalares , so bernardo do campo ; e unitec ind . e com . de 
 aparelhos hospitalares ltda . , so paulo ) , dois na dinamarca ( ambu 
 silicone resuscitator e ambuspur ; ambu a / s , ballerup , dinamarca ) 
 e um nos eua ( hudson rcilifesaver ; hudson rci , durham , nc , eua ) . 
 os rms testados foram emprestados pelos fabricantes ou representantes nacionais . 

todos os modelos ainda so comercializados , e as atualizaes realizadas nos 
 equipamentos desde a realizao do presente estudo at a sua redao esto 
 descritas na tabela 1 . 

tabela 1 caractersticas dos reanimadores manuais para adultos descritas 
 pelos fabricantes.nd : informao no disponvel .
do ano de 2006 at o momento 
 da redao do presente estudo , os aparelhos 1 , 2 , 3 , 4 e 7 no 
 sofreram alteraes significativas .
no aparelho 5 , a conexo 
 atual para o paciente  do tipo swivel .
no aparelho 8 , a 
 capacidade do balo aumentou de 1.000 para 1.500 ml . 
 
nd : informao no disponvel . obs . : do ano de 2006 at o momento 
 da redao do presente estudo , os aparelhos 1 , 2 , 3 , 4 e 7 no 
 sofreram alteraes significativas .
no aparelho 5 , a conexo 
 atual para o paciente  do tipo swivel .
no aparelho 8 , a 
 capacidade do balo aumentou de 1.000 para 1.500 ml .
como no existe uma norma brasileira definindo as caractersticas para fabricao 
 e comercializao de rms , para a presente avaliao , foram usados critrios da 
 astm , designation f920 - 93 , 


  equivalente aos da international organization for 
 standardization 8382 , 


  utilizada em outros pases .
os seguintes critrios foram avaliados : 
 a resistncia imposta pela vlvula do paciente durante as fases inspiratria e 
 expiratria ; o funcionamento da vlvula limitadora de presso ( vlp ) ; e volume 
 corrente ( vt ) entregue pelo rm em um simulador do sistema 
 respiratrio .
de acordo com os critrios da astm , os itens avaliados devem 
 obedecer as seguintes especificaes : queda de presso inspiratria e 
 expiratria < 5 cmh2o na presena de um fluxo de 50 l / min , 
 determinando uma resistncia < 6 cmh2o .
s ; a utilizao de vlp no  obrigatria para rm adulto , mas , 
 se disponvel , deve poder ser fechada ; oferta de vt  600 ml para 
 pacientes adultos ( peso  40 kg ) com resistncia de 20 cmh2o . 

s e complacncia de 0,02 l / cmh2o 
 com o operador usando somente uma mo ( tamanho mximo da mo de 185 mm ) .
o sistema de medidas foi constitudo por um tubo plstico onde foram adaptados os 
 sensores de presso e de fluxo ( figura 2 ) . 

os sensores tiveram seus sinais amplificados e armazenados em um microcomputador 
 para posterior anlise em um aplicativo desenvolvido no 
 software labview ( national instruments , tx , 
 eua ) .
a frequncia de amostragem do sinal foi de 200 hz . 
 figura 2 representao esquemtica do sistema experimental . 1 : sensor de 
 fluxo proximal ou distal ; 2 : sensor de presso ; 3 : resistncia ; e 4 : 
 sensor de presso alveolar . 
 
para as medidas da resistncia inspiratria e expiratria , foi conectado um 
 ventilador mecnico ( bear 5 ; bear medical systems , riverside , ca , 
 eua ) a uma das extremidades do tubo plstico com os sensores ( figura 2 ) .
o ventilador foi ajustado em modo 
 volume controlado , fluxo inspiratrio constante de 60 l / min e peep de zero 
 cmh2o .
para a resistncia expiratria , o conector do paciente do 
 rm foi adaptado  outra extremidade do tubo plstico , e o ar do ventilador saia 
 pela porta expiratria para o ar ambiente ( figura 
 2 ) .
na avaliao da resistncia inspiratria , o rm foi desmontado e 
 apenas a poro proximal do conjunto , sem o balo , foi utilizada ( figura 2 ) .
a parte do rm que se conecta ao 
 balo foi adaptada  outra extremidade do tubo plstico , e o ar saia pelo 
 conector do paciente para o ar ambiente .
no foi feito o teste com o rm modelo ambu silicone resuscitator 
 porque o aparelho no pde ser desmontado . as duas resistncias foram calculadas 

pela diferena entre a presso proximal e distal  vlvula ( a presso distal no 
 foi medida , pois era igual a zero , j que o sistema estava aberto para o ar 
 ambiente ) , dividida pelo fluxo medido .
para o teste do vt , os rms foram conectados a um tubo plstico com os 
 sensores , e esse tubo a uma cnula traqueal de dimetro 8,5 mm ( rusch , 
 montevidu , uruguai ) , cuja poro distal , com o balonete insuflado , era adaptada 
 no interior de outro tubo plstico que se conectava a um simulador do sistema 
 respiratrio ( ttl 2600 ; michigan instruments , grands 
 rapids , mi , eua ; figura 2 ) .
o simulador 
 permitia o ajuste da complacncia dos foles atravs de molas ; para o ajuste da 
 resistncia , foram utilizados resistores no lineares .
quatro voluntrios , fisioterapeutas de uti da cidade de so paulo , sendo dois 
 homens e duas mulheres , operaram os rms .
o tamanho da mo dominante ( do punho 
 at a ponta do terceiro dedo ) desses profissionais era de 200 mm para o homem 1 , 
 188 mm para o homem 2 , 175 mm para a mulher 1 e 160 mm para mulher 2 .
os 
 fisioterapeutas foram orientados a insuflar o modelo como se estivessem 
 ventilando um paciente , primeiro com uma e depois com as duas mos , com os oito 
 rms , que foram avaliados em sequncia aleatria , em duas situaes de 
 resistncia e complacncia : 1 ) condio " astm " - complacncia de 0,02 
 l / cmh2o e resistncia de 20 cmh2o .
s , de acordo com a norma da astm ; 


  e 2 ) condio " normal " - complacncia de 0,05 l / cmh2o e 
 resistncia de 5 cmh2o .
para o clculo do vt , foram analisados trs ciclos respiratrios , 
 aleatoriamente escolhidos , entre os ciclos gravados ( mnimo de 10 por condio 
 teste ) .
como cada voluntrio ( total de quatro ) manipulou oito rms , com uma e com 
 duas mos , e em dois cenrios clnicos distintos ( condio astm e normal ) , foram 
 realizadas 128 condies teste .
dos oito rms , cinco estavam equipados com vlp e foram submetidos a esse teste .
o 
 ventilador , conectado em uma das extremidades do sistema de medidas ( com sensor 
 de fluxo e presso ) , foi ajustado no modo volume controlado , com fluxo 
 inspiratrio constante de 20 l / min , vt de 1.800 ml e peep de zero 
 cmh2o .
na outra extremidade , foi conectada uma parte do rm e , na 
 sequncia , outro sensor de fluxo ( distal ) e o simulador ( figura 2 ) .
foi avaliada a presso na qual a vlp se abria e permitia o vazamento 
 de ar ( momento que podia ser identificado quando o fluxo no sensor distal caia 
 em relao ao proximal ) , a qual foi denominada " presso de abertura " e em qual 
 valor de presso todo ar enviado pelo ventilador passava apenas pela vlp 
 ( momento no qual o fluxo distal era igual  zero ) , que foi denominada " presso 
 mxima " .
o funcionamento da vlvula foi considerado adequado se a presso de 
 abertura ocorresse no intervalo de presso sugerido pelos fabricantes , em geral , 
 valores maiores do que 35 - 40 cmh2o ( tabela 1 ) .
para cada rm , somente um valor de resistncia inspiratria e expiratria foi 
 mostrado , pois a variao era desprezvel entre os ciclos .
os valores de vt foram mostrados 
 como mdia e desvio - padro e avaliados atravs de uma anlise multivariada de 
 regresso linear mista ( mixed model ) para cada uma das quatro 
 condies estudadas : vt com uma
mo nas condies astm e normal e 
 vt com duas mos nas mesmas duas condies .
foi realizada uma anlise post hoc 
 com correo de sidak para a comparao dos valores de vt entre os 
 fisioterapeutas e entre os rms .
para essa anlise , foi usado o pacote 
 estatstico statistical package for the social sciences , verso 
 17 para windows ( spss inc . ,
em relao ao tipo da vlvula do paciente , 
 predominou o tipo diafragma e , em relao ao material do balo , o silicone .
a 
 capacidade do balo de cada rm era varivel ( 1.000 - 2.500 ml ) .
os trs rms 
 importados no dispunham de vlp , presente nos cinco equipamentos nacionais , 
 sendo que , no da marca rwr , a vlp podia ser fechada sem que ocorresse vazamento . 

outra diferena observada entre os rms importados e nacionais foi o fato de que 
 o conector do paciente era fixo nos cinco reanimadores brasileiros , enquanto , 
 nos importados , esse era do tipo " swivel 360 " .
na tabela 2 , esto descritos os 
 resultados dos testes que avaliaram as resistncias da vlvula do paciente , 
 durante a inspirao e expirao , e o funcionamento da vlp .
apenas a resistncia 
 expiratria do rm da marca protec excedeu o limite estabelecido pelos critrios 
 da astm ( < 6 cmh2o .
s. as demais 
 resistncias dos rms testados estavam de acordo com as normas , sendo o maior 
 valor de resistncia inspiratria encontrado no rm da oxigel ( 5,69 
 cmh2o .
s. a presso da abertura 
 da vlp ( presente em cinco dos rms ) foi baixa ( < 17 cmh2o ) , e o 
 valor de sua presso mxima variou de 32,0 - 55,9 cmh2o . 

tabela 2 resistncias inspiratria e expiratria da vlvula para o 
 paciente e avaliao da vlvula limitadora de presso . 
 
o valor mdio de vt ofertado pelos rms ( tabela 3 ) e pelos fisioterapeutas ( tabela e1 , disponvel no site do jornal brasileiro de 
 pneumologia , http://www.jornaldepneumologia.com.br/detalhe_artigo.asp?id=2212http://www.jornaldepneumologia.com.br/detalhe_artigo.asp?id=2212 ) 
 foi varivel . nas situaes avaliadas ( manipulao dos oito rms , com uma e duas 
 mos , e em dois cenrios clnicos distintos , condio astm e normal ) , houve 
 diferenas significantes ( p < 0,001 ) tanto entre os rms , quanto entre os 
 fisioterapeutas . todos os rms , sempre que manipulados com uma mo , ofertaram um 
 vt inferior ao valor preconizado pela norma americana (  600 ml , 
 na condio astm ) .
apenas os dois modelos do fabricante ambu a / s ofertaram 
 vt  600 ml , utilizando somente uma mo ; porm , somente durante a 
 simulao da condio clnica normal .
mesmo manipulando o rm com as duas mos , 
 os rms dos fabricantes oxigel e rwr , na condio clnica astm , no ofertaram o 
 vt mnimo , enquanto que os dos fabricantes protec e unitec , 
 independentemente do cenrio clnico simulado , ofertaram vt < 600 
 ml . 
 tabela 3 volume corrente ( vt ) na situao normal e de acordo com os 
 critrios da american society of testing materials ( astm).aavalores expressos em mdia  dp , a partir de 3 medidas , em mlbcomplacncia = 0,02 l / cmh2o ; e resistncia = 20 
 cmh2o .
l . s 
 ccomplacncia = 0,05 l / cmh2o ; e resistncia = 5 
 cmh2o .
s. p < 
 0,05 em relao aos equipamentos sem vlvula*ambu**ambu s ; e***hudson / rci 
  valores expressos em mdia  dp , a partir de 3 medidas , em ml complacncia = 0,02 l / cmh2o ; e resistncia = 20 
 cmh2o .
l . s 
  complacncia = 0,05 l / cmh2o ; e resistncia = 5 
 cmh2o .
s. p < 
 0,05 em relao aos equipamentos sem vlvula ainda , observando os resultados expressos na tabela 3 ,  possvel verificar que os valores de vt na 
 situao clnica normal foram , no geral , maiores do que na condio astm , que 
 simula uma condio pulmonar com menor complacncia e maior resistncia , e que a 
 maioria dos vt obtidos com os rms sem vlp foram superiores em relao 
 aos obtidos com os rms com vlp .
os principais resultados do presente estudo podem ser resumidos nos seguintes 
 itens : 1 ) as resistncias ( inspiratria e expiratria ) da vlvula do paciente 
 obedeceram aos padres estabelecidos pela norma americana , com exceo de um rm ; 
 2 ) os oito rms avaliados no ofertaram o vt mnimo em condies 
 padronizadas pela mesma norma ( vt  600 ml , com uma mo , na condio 
 clnica astm ) ; 3 ) manipular o rm com as duas mos no resolveu o problema em 
 quatro rms ( o vt permaneceu < 600 ml ) ; e 4 ) a vlp presente nos rms 
 nacionais determinou , no geral , o fornecimento de um vt menor em 
 relao aos rms sem vlp .
no brasil , existem poucos estudos publicados avaliando rms para pacientes 
 adultos , comumente utilizados em utis brasileiras . 






 
embora esses estudos tenham investigado caractersticas 
 importantes , como , por exemplo , a frao de oxignio ofertada pelos rms com e 
 sem o reservatrio de oxignio , o presente estudo avaliou outras propriedades 
 igualmente importantes que ainda no haviam sido relatadas na literatura 
 nacional .
em relao  avaliao da resistncia da vlvula do paciente na inspirao e na 
 expirao , todos os rms testados estavam dentro das especificaes da astm , com 
 exceo do rm do fabricante protec , que apresentou resistncia expiratria de 
 7,91 cmh2o .
s. esse resultado no 
 surpreende , uma vez que outros estudos internacionais j haviam descrito 
 equipamentos com resistncias da vlvula do paciente superiores ao 
 recomendado . 




 
 importante ressaltar que quanto maior a resistncia expiratria , 
 mais prolongada se torna a expirao , o que pode provocar aprisionamento de ar 
 ( auto - peep ) e risco de barotrauma , 


  principalmente quando o rm  manipulado com alta frequncia 
 respiratria e alto vt .
para o teste do vt com uma e duas mos , foram escolhidos voluntrios 
 de ambos os sexos , pois se sabe que o vt obtido varia com o sexo do 
 operador ( vt menor nos operadores do sexo feminino ) . 


 
houve grande variabilidade entre as mdias dos vt dentre 
 os rms testados , o que j havia sido observado em outros estudos . 


 
observamos que alguns rms nacionais ofertaram um vt 
 baixo mesmo com uso das duas mos , que determina maior vt do que o 
 uso de somente uma mo . 






 
outros autores j haviam relatado , mesmo em simulaes com 
 complacncia normal , valores de vt menores do que 600 ml . 


 
, 


  que avaliou 16 rms descartveis fabricados no exterior , apenas trs 
 rms no ofertaram o vt mnimo preconizado pela astm (  600 ml ) .
possivelmente , vrios fatores influenciaram os resultados referentes ao 
 vt . um fator que parece ter determinado valores elevados de 
 vt foi o tamanho das mos de um dos fisioterapeutas ( 200 mm , 
 medida superior  recomendada pelas normas , homem 1 , tabela e1 , disponvel no site do jornal brasileiro de 
 pneumologia , http://www.jornaldepneumologia.com.br/detalhe_artigo.asp?id=2212 ) . 
 essa associao entre o vt entregue e o tamanho das mos j foi 
 descrita por outros autores . 








 
fatores que poderiam determinar volumes baixos so o 
 tamanho 


  e o material do balo do reanimador testado . 


  o volume de ar no balo no  totalmente insuflado para o paciente 
 quando ele  comprimido , sendo que , genericamente ,
o volume do balo deve ser 
 duas vezes maior que o volume que se quer insuflar . 


 
um balo de material pouco complacente ( como o polivinil ) pode 
 determinar um vt menor . 


 
no nosso estudo , o rm que ofertou os menores vt ( unitec ) 
 tinha o balo com o menor volume e que era , ainda , constitudo de polivinil .
 
 importante ressaltar que o vt dos rms nacionais foi , no geral , menor 
 do que o dos importados , com exceo do rm do fabricante rwr , que apresentou 
 vt maiores , provavelmente porque a capacidade do balo era de 
 2.500 ml .
poderia ser questionado se o baixo vt encontrado para alguns rms 
 ocorreu devido  fadiga dos voluntrios .
no entanto , no estudo de hess et 
 al . , 


  que avaliou o efeito da fadiga determinada por uma ventilao com 
 rm por um perodo de 30 minutos em uma situao de baixa complacncia ( 20 
 ml / cmh2o ) , no foi observada uma reduo do vt aps 30 
 minutos para os 14 voluntrios avaliados .
considerando que , em nosso estudo , o 
 tempo total de teste para cada um dos rm foi de cerca de um minuto , o que 
 determinaria um total de oito minutos para cada uma das quatro situaes 
 avaliadas ( duas situaes de impedncia com uma ou com duas mos ) e que ainda 
 havia um perodo de descanso entre cada medida , parece pouco provvel que a 
 ocorrncia de fadiga tenha influenciado os resultados .
como esperado , o vt obtido na simulao de um paciente " normal " foi 
 superior ao encontrado nos testes com os ajustes de complacncia e resistncia 
 padronizados pela norma americana , que simulavam um paciente com baixa 
 complacncia e alta resistncia , que comprovadamente determinam um menor 
 vt . 


 
todos rms brasileiros tinham a vlp e , em somente um deles , a vlvula podia ser 
 fechada .
a abertura inicial das vlvulas de todos os dispositivos ocorreu em 
 presses reduzidas , com valores abaixo do especificado , determinando vazamento 
 durante a insuflao , o que pode explicar , em parte , o menor vt 
 obtido com os rms com vlp .
esse resultado pode ser considerado uma falha grave , 
 pois pode impedir a adequada ventilao de pacientes com complacncia pulmonar 
 baixa ou com resistncia de vias areas elevada , como , por exemplo , no caso de 
 pacientes com edema pulmonar e crise asmtica , respectivamente .
segundo alguns autores , a presena da vlp no traz segurana adicional para o 
 paciente adulto , 


  j que o risco de barotrauma no est associado somente s presses 
 de pico elevadas durante a inspirao . 


 
inclusive a norma americana 


  dispensa o uso do dispositivo regulador de presso para os rms para 
 adultos e , se presente , determina que a vlvula possa ser travada e que o seu 
 modo de fechamento deva ser bem evidente para o operador . 




 
mesmo no caso dos rms para pacientes da faixa neonatal / peditrica , 
 para os quais  recomendada a presena da vlvula para limitar a presso em 
 valores inferiores a 40  5 cmh2o , 




  o funcionamento inadequado da vlp tambm pode comprometer a 
 ventilao . 


 
so consideradas limitaes do nosso estudo a realizao de todos os testes com 
 apenas uma unidade de cada rm ( porm , todos os rms eram novos , sem uso prvio ) ; 
 o teste da resistncia da vlvula do paciente foi realizado com fluxo de 60 
 l / min , em vez de 50 l / min , valor esse preconizado pela astm , o que pode 
 dificultar a comparao com outros estudos ; e , como o presente estudo foi 
 realizado em 2006 , alguns modelos de rm sofreram alteraes ( tabela 1 ) , o que pode ter modificado seus 
 desempenhos .
tal fato provavelmente deve ser verdadeiro para o rm do fabricante 
 unitec , que teve a capacidade do balo aumentada significativamente ( tabela 1 ) .  
apesar das limitaes do estudo , acreditamos que so apontadas deficincias 
 importantes dos rms fabricados no brasil , principalmente referentes ao 
 funcionamento da vlp ( a maioria no pde ser travada e apresentou abertura 
 precoce ) , que , em algumas situaes clnicas , podem comprometer a ventilao de 
 pacientes crticos .
os resultados apresentados indicam a necessidade de que , 
 para se ofertar um vt adequado , as duas mos devem comprimir o rm e 
 que , quando o rm permitir , a vlp deve ser mantida fechada
. acreditamos que os 
 resultados obtidos no presente estudo podero auxiliar na realizao de futuros 
 testes e no aprimoramento dos rms nacionais .
 objective : to evaluate the performance of manual resuscitators ( mrs ) used in brazil in 
 accordance with international standards . 
 methods : using a respiratory system simulator , four volunteer physiotherapists 
 employed eight mrs ( five produced in brazil and three produced abroad ) , 
 which were tested for inspiratory and expiratory resistance of the patient 
 valve ; functioning of the pressure - limiting valve ; and tidal volume 
 ( vt ) generated when the one - handed and two - handed techniques 
 were used . 
 the tests were performed and analyzed in accordance with the 
 american society for testing and materials ( astm ) f920 - 93 criteria . 
 results : expiratory resistance was greater than 6 cmh2o . 
 l1 . 
 
 s1 in only one mr . the pressure - limiting valve , a feature of 
 five of the mrs , opened at low pressures ( < 17 cmh2o ) , and the 
 maximal pressure was 32.0 - 55.9 cmh2o . 
 mean vt varied 
 greatly among the mrs tested . 
 the mean vt values generated with 
 the one - handed technique were lower than the 600 ml recommended by the astm . 
 in the situations 
 studied , mean vt was generally lower from the 
 brazilian - made mrs that had a pressure - limiting valve . 
 conclusions : the resistances imposed by the patient valve met the astm criteria in all 
 but one of the mrs tested . 
 the pressure - limiting valves of the 
 brazilian - made mrs usually opened at low pressures , providing lower 
 vt values in the situations studied , especially when the 
 one - handed technique was used , suggesting that both hands should be used and 
 that the pressure - limiting valve should be closed whenever possible . 
Introduction
Methods
Results
Discussion
OBJETIVO:
MTODOS:
RESULTADOS:
CONCLUSES: 
Introduo
Mtodos
Resultados
Discusso