Effect of different cycling-off criteria and positive end-expiratory pressure during pressure support ventilation in patients with chronic obstructive pulmonary disease.
OBJECTIVE
During pressure support ventilation, ventilator inspiration ends when inspiratory flow drops to a given percentage of the peak inspiratory flow cycling-off criteria. This study evaluated the effect of two different cycling-off criteria on breathing pattern, respiratory effort, and gas exchange in patients with chronic obstructive pulmonary disease.


METHODS
Clinical study.


METHODS
Thirteen mechanically ventilated patients with acute exacerbation of chronic obstructive pulmonary disease primarily due to pneumonia (PaO2/FIO2 291 +/- 114 mm Hg, PaCO2 53 +/- 19 mm Hg).


METHODS
Two cycling-off criteria (5% and 40% of the peak inspiratory flow) at two levels of pressure support (5 and 15 cm H2O) with and without the application of an external positive end-expiratory pressure (6 and 0 cm H2O) were applied. Measurement Patient-ventilator time delay of cycling-off was computed as the difference between the end of inspiratory flow and the lowest value of inspiratory esophageal pressure. Inspiratory effort was estimated by computing the work of breathing, the pressure time product partitioned into the total pressure time product, and the pressure time product due to the dynamic intrinsic positive end-expiratory pressure.


RESULTS
At 5 and 15 cm H2O of pressure support ventilation, the cycling-off criteria 40% significantly reduced the patient-ventilator time delay of cycling-off from 0.40 +/- 0.20 secs to 0.29 +/- 0.16 secs and from 0.93 +/- 0.50 secs to 0.52 +/- 0.25 secs, respectively; the dynamic intrinsic positive end-expiratory pressure from 3.9 +/- 1.8 cm H2O to 3.1 +/- 2.1 cm H2O and from 2.4 +/- 2.0 cm H2O to 1.7 +/- 1.4 cm H2O, respectively; and the pressure time product due to the dynamic intrinsic positive end-expiratory pressure. At 5 cm H2O of pressure support, the cycling-off criteria 40% significantly reduced the tidal volume and the inspiratory effort. The modification of cycling-off criteria did not affect the gas exchange.


CONCLUSIONS
The modification of cycling-off criteria may have a beneficial effect on reducing the dynamic hyperinflation and inspiratory effort in chronic obstructive pulmonary disease patients, especially at low levels of pressure support.
Chiumello
Davide
D
Dipartimento di Anestesia e Rianimazione, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico-Ospedale Maggiore Policlinico, Mangiagalli, Regina Elena, Milan, Italy. chiumello@libero.it
Polli
Federico
F
Tallarini
Federica
F
Chierichetti
Monica
M
Motta
Giuliana
G
Azzari
Serena
S
Colombo
Riccardo
R
Rech
Roberto
R
Pelosi
Paolo
P
Raimondi
Ferdinando
F
Gattinoni
Luciano
L
D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D011175:Positive-Pressure Respiration / Q000379:methods*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000628:therapy*; D012119:Respiration