Aspiration of dead space allows isocapnic low tidal volume ventilation in acute lung injury. Relationships to gas exchange and mechanics.
OBJECTIVE
In acute lung injury (ALI) mechanical ventilation damages lungs. We hypothesised that aspiration and replacement of dead space during expiration (ASPIDS) allows normocapnic ventilation at higher end-expiratory pressure (PEEP) and reduced tidal volume (V(T)), peak and plateau pressures (Paw(peak), Paw(plat)), thus avoiding lung damage.


METHODS
University Hospital.


METHODS
Seven consecutive sedated and paralysed ALI patients were studied.


METHODS
Single breath test for CO(2) and multiple elastic pressure volume (Pel/V) curves recorded from different end-expiratory pressures guided ventilatory setting at ASPIDS. ASPIDS was studied at respiratory rate (RR) of 14 min(-1) and then 20 min(-1) with minute ventilation maintaining stable CO(2) elimination.


RESULTS
Alveolar and airway dead spaces were 24.3% and 31.3% of V(T), respectively. Multiple Pel/V curves showed a shift towards lower volume at decreasing PEEP, thus indicating that patients required a higher PEEP. At ASPIDS, PEEP was increased from 8.9 cmH(2)O to 12.6 cmH(2)O and VT reduced from 11 ml/kg to 8.9 ml/kg at RR 14 min(-1) and to 6.9 ml/kg at RR 20 min(-1). A significant decrease in Paw(peak) (36.7 vs 32 at RR 14 min(-1) and 28.7 at RR 20 min(-1)) and Paw(plat) (29.9 vs 27.3 at RR 14 min-1 and 24.1 at RR 20 min-1) were observed. PaCO(2) remained stable. No intrinsic PEEP developed. No side effects were noticed.


CONCLUSIONS
ASPIDS allowed the use of higher PEEP at lower V(T) and inflation pressure and constant PaCO(2). Multiple Pel/V curves gave insight into the tendency of lungs to collapse.
De Robertis
E
E
Department of Anaesthesia and Intensive Care, University Federico II, Napoli, Italy.
Servillo
G
G
Tufano
R
R
Jonson
B
B
D000368:Aged; D001784:Blood Gas Analysis; D001794:Blood Pressure; D001944:Breath Tests; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D008170:Lung Compliance; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D011659:Pulmonary Gas Exchange; D012126:Respiratory Dead Space; D012128:Respiratory Distress Syndrome / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D015656:Respiratory Mechanics; D012720:Severity of Illness Index; D013396:Suction / Q000295:instrumentation / Q000379:methods*; D013990:Tidal Volume
D002245:Carbon Dioxide