title: Inverse ratio ventilation (I/E = 2/1) in acute respiratory distress syndrome: a six-hour controlled study.
abstract: To assess the cardiorespiratory effects of a prolonged application of inverse ratio ventilation (IRV), we compared IRV (I/E = 2) with conventional ventilation (CV) (I/E = 0.5), applied for 6 h each in a randomized order, with constant tidal volume (VT) and total positive end-expiratory pressure (PEEP(tot)) in eight patients with acute respiratory distress syndrome (ARDS). After 1 h, IRV resulted in a lower peak inspiratory pressure (PIP) (28.2 +/- 1.5 versus 35.6 +/- 1.7 cm H2O, p < 0.05), an unchanged plateau pressure, and a higher mean airway pressure (MAP) (17.8 +/- 0.8 versus 15.6 +/- 0.5 cm H2O, p < 0.05) than CV. No significant difference in Pa(O2) and shunt fraction (QS/QT) was observed (83 +/- 7 mm Hg and 40 +/- 4% in CV versus 92 +/- 14 mm Hg and 35 +/- 3% in IRV, respectively). The Pa(CO2) was lower in IRV (48 +/- 3 versus 55 +/- 5 mm Hg, p < 0.05). Cardiac index (CI) and oxygen delivery (D(O2)) were lower in IRV (3.7 +/- 0.4 L/min/m2 and 500 +/- 61 ml/min/m2 versus 4.6 +/- 0.5 L/min/m2 and 617 +/- 80 ml/min/m2, respectively, p = 0.05 for both). Regardless of the considered parameter, no significant difference was observed between results after 1, 2, 4, and 6 h in each mode. We conclude that IRV at a ratio that results in a significant intrinsic PEEP does not improve Pa(O2), enhances CO2 elimination, decreases cardiac output (CO), and does not exert any time-dependent effect.
authors.affiliation: Service de Reanimation Medicale, Hopital de Bicetre, Faculte de Medecine Paris-Sud, France.
authors.forename: A
authors.initials: A
authors.lastname: Mercat
authors.forename: M
authors.initials: M
authors.lastname: Titiriga
authors.forename: N
authors.initials: N
authors.lastname: Anguel
authors.forename: C
authors.initials: C
authors.lastname: Richard
authors.forename: J L
authors.initials: JL
authors.lastname: Teboul
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure; D002302:Cardiac Output; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000503:physiopathology; D012121:Respiration, Artificial / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000503:physiopathology / Q000628:therapy*; D013990:Tidal Volume; D013997:Time Factors
chemical_list: D010100:Oxygen