Extending inspiratory time in acute respiratory distress syndrome.
OBJECTIVE
To assess the short-term effects of extending inspiratory time by lengthening end-inspiratory pause (EIP) without inducing a clinically significant increase in intrinsic positive end-expiratory pressure (PEEPi) in patients with acute respiratory distress syndrome (ARDS).


METHODS
Controlled, randomized, crossover study.


METHODS
Two medical intensive care units of university hospitals.


METHODS
Sixteen patients with early (< or =48 hrs) ARDS.


METHODS
We applied two durations of EIP (0.2 secs and extended) each for 1 hr while keeping all the following ventilatory parameters constant: FIO2, total PEEP (PEEPtot = applied PEEP + PEEPi), tidal volume, inspiratory flow, and respiratory rate. The duration of extended EIP was titrated to avoid an increase of PEEPi of > or =1 cm H2O.


RESULTS
Despite an increase in mean airway pressure (20.6 +/- 2.3 vs. 17.6 +/- 2.1 cm H2O, p < .01), extended EIP did not significantly improve PaO2 (93 +/- 21 vs. 86 +/-16 torr [12.40 +/- 2.80 vs. 11.46 +/- 2.13 kPa] with 0.2 secs EIP, NS). However, although the difference in PaO2 between the two EIP durations was <20 torr (<2.66 kPa) in 14 patients, two patients exhibited a >40 torr (>5.33 kPa) increase in PaO2 with extended EIP. Extended EIP decreased PaCO2 (62 +/- 13 vs. 67 +/- 13 torr [8.26 +/- 1.73 vs. 8.93 +/- 1.73 kPa] with 0.2 secs EIP, p < .01), which resulted in a higher pH (7.22 +/- 0.10 vs. 7.19 +/- 0.09 with 0.2 secs EIP, p < .01) and contributed to a slight increase in arterial hemoglobin saturation (94 +/- 3 vs. 93 +/- 3% with 0.2 EIP, p < .01). No significant difference in hemodynamics was observed.


CONCLUSIONS
In patients with ARDS, extending EIP without inducing a clinically significant increase in PEEPi does not consistently improve arterial oxygenation but enhances CO2 elimination.
Mercat
A
A
Service de Réamination Médicale, Hopitaux de Bicêtre et Boucicaut, France.
Diehl
J L
JL
Michard
F
F
Anguel
N
N
Teboul
J L
JL
Labrousse
J
J
Richard
C
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018592:Cross-Over Studies; D006439:Hemodynamics; D006801:Humans; D008875:Middle Aged; D018467:Positive-Pressure Respiration, Intrinsic; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000628:therapy*; D015656:Respiratory Mechanics; D018709:Statistics, Nonparametric