Mechanical ventilation in acute respiratory failure: recruitment and high positive end-expiratory pressure are necessary.
OBJECTIVE
To review as best the critical care clinicians can recruit the acute respiratory distress syndrome (ARDS) lungs and keep the lungs opened, assuring homogeneous ventilation, and to present the experimental and clinical results of these mechanical ventilation strategies, along with possible improvements in patient outcome based on selected published medical literature from 1972 to 2004 (highlighting the period from June 2003 to June 2004 and recent results of the authors' group research).


RESULTS
In the experimental setting, repeated derecruitments accentuate lung injury during mechanical ventilation, whereas open lung concept strategies can attenuate lung injury. In the clinical setting, recruitment maneuvers improve short-term oxygenation in ARDS patients. A recent prospective clinical trial showed that low versus intermediate positive end-expiratory pressure (PEEP) levels (8 vs 13 cm H2O) associated with low tidal ventilation had the same effect on ARDS patient survival. Nevertheless, both conventional and electrical impedance thoracic tomography studies indicate that stepwise PEEP recruitment maneuvers increase lung volume and the recruitment percentage of lung tissue, and higher levels of PEEP (18-26 cm H2O) are necessary to keep the ARDS lungs opened and assure a more homogeneous low tidal ventilation.


CONCLUSIONS
Stepwise PEEP recruitment maneuvers can open collapsed ARDS lungs. Higher levels of PEEP are necessary to maintain the lungs open and assure homogenous ventilation in ARDS. In the near future, thoracic CT associated with high-performance monitoring of regional ventilation (electrical impedance tomography) may be used at the bedside to determine the optimal mechanical ventilation of ARDS patients.
Barbas
Carmen Sílvia Valente
CS
Division of Pulmonary and Critical Care, University of São Paulo, São Paulo, Brazil; and Intensive Care Unit, Albert Einstein Hospital, São Paulo, Brazil. cbarbas@attglobal.net
de Matos
Gustavo Faissol Janot
GF
Pincelli
Mariangela Pimentel
MP
da Rosa Borges
Eduardo
E
Antunes
Telma
T
de Barros
Juliana Monteiro
JM
Okamoto
Valdelis
V
Borges
João Batista
JB
Amato
Marcelo Brito Passos
MB
de Carvalho
Carlos Roberto Ribeiro
CR
D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology; D008176:Lung Volume Measurements; D011175:Positive-Pressure Respiration / Q000379:methods*; D011187:Posture; D013902:Radiography, Thoracic; D012128:Respiratory Distress Syndrome / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D015656:Respiratory Mechanics; D016896:Treatment Outcome