Evaluation of adaptive support ventilation in paralysed patients and in a physical lung model.
OBJECTIVE
Evaluation of the respiratory pattern selected by the Adaptive Support Ventilation (ASV) in ventilated patients with acute, chronic respiratory failure and normal lungs and in a physical lung model.


METHODS
We tested ASV both on patients and in a physical lung model, with a normal level of minute ventilation and with minute ventilation increased by 30%. In each patient, respiratory pattern, mechanics and blood gases were recorded.


METHODS
General ICU of a University Hospital.


RESULTS
In patients with normal lungs, mean values+/-SD were: tidal volume (Vt) 558.1+/-142.4 mL, respiratory rate (RR) 12.6+/-1.3b/min and inspiratory time/total time ratio (Ti/Ttot) 42.4+/-4.1%; in COPD, mean values+/-SD were: Vt 724+/-171 mL, RR 9.2+/-2.7b/min and Ti/Ttot 26.6+/-10.5%; in restrictive ones, mean values+/-SD were: Vt 550.2+/-77.0 mL, RR 15.8+/-2.6b/min, Ti/Ttot 47.5+/-2.5%. In the lung model, at a normal setting, mean values+/-SD were: Vt 523+/-18.5 mL, RR 14+/-0.0b/min, Ti/Ttot 44.0%, in COPD, mean values+/-SD were: Vt 678+/-0.0 mL, RR 9+/-0.0b/min, Ti/Ttot 20+/-0.7%, in restrictive one, mean values+/-SD were: Vt 513+/-12.8 mL, RR 15+/-0.0b/min, Ti/Ttot 48+/-1.5%. In model hyperventilation conditions in a normal setting a Vt of 582+/-16.6 mL, RR 16+/-0.0b/min, Ti/Ttot 48+/-0.0% were selected, in the obstructive setting Vt 883+/-0.0 mL, RR 9+/-0.0b/min, Ti/Ttot 20+/-0.0% and in a restrictive one Vt 545+/-8.4 mL, RR 18+/-0.0b/min, Ti/Ttot 50-0.0%.


CONCLUSIONS
In normal patients ASV selected a ventilatory pattern close to the physiological one, in COPD almost a high expiratory time pattern and in restrictive ones a reduced tidal volume pattern. In the model the selection was similar. In the hyperventilation test, ASV chose a balanced increase in both Vt and RR.
1st Anesthesia and Reanimation Service, IRCCS Policlinico San Matteo di Pavia, Pavia, Italy. mirkobelliato@smatteo.pv.it
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D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006985:Hyperventilation / Q000503:physiopathology; D007320:Inspiratory Capacity / Q000502:physiology; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D008991:Monitoring, Physiologic; D010100:Oxygen / Q000097:blood; D010243:Paralysis / Q000503:physiopathology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000628:therapy; D012016:Reference Values; D012119:Respiration; D012121:Respiration, Artificial / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy
D002245:Carbon Dioxide; D010100:Oxygen