Impact of acute hypercapnia and augmented positive end-expiratory pressure on right ventricle function in severe acute respiratory distress syndrome.
OBJECTIVE
To evaluate the effects of acute hypercapnia induced by positive end-expiratory pressure (PEEP) variations at constant plateau pressure (P (plat)) in patients with severe acute respiratory distress syndrome (ARDS) on right ventricular (RV) function.


METHODS
Prospective observational study in two academic intensive care units enrolling 11 adults with severe ARDS (PaO(2)/FiO(2) <150 mmHg at PEEP >5 cmH(2)O). We compared three ventilatory strategies, each used for 1 h, with P (plat) at 22 (20-25) cmH(2)O: low PEEP (5.4 cmH(2)O) or high PEEP (11.0 cmH(2)O) with compensation of the tidal volume reduction by either a high respiratory rate (high PEEP/high rate) or instrumental dead space decrease (high PEEP/low rate). We assessed RV function (transesophageal echocardiography), alveolar dead space (expired CO(2)), and alveolar recruitment (pressure-volume curves).


RESULTS
Compared to low PEEP, PaO(2)/FiO(2) ratio and alveolar recruitment were increased with high PEEP. Alveolar dead space remained unchanged. Both high-PEEP strategies induced higher PaCO(2) levels [71 (60-94) and 75 (53-84), vs. 52 (43-68) mmHg] and lower pH values [7.17 (7.12-7.23) and 7.20 (7.16-7.25) vs. 7.30 (7.24-7.35)], as well as RV dilatation, LV deformation and a significant decrease in cardiac index. The decrease in stroke index tended to be negatively correlated to the increase in alveolar recruitment with high PEEP.


CONCLUSIONS
Acidosis and hypercapnia induced by tidal volume reduction and increase in PEEP at constant P (plat) were associated with impaired RV function and hemodynamics despite positive effects on oxygenation and alveolar recruitment ( ClinicalTrials.gov #NCT00236262).
Mekontso Dessap
Armand
A
Medical Intensive Care Unit, Assistance Publique-Hôpitaux de Paris, Henri Mondor-Albert Chenevier Teaching Hospital, Créteil, France. armand.dessap@hmn.aphp.fr
Charron
Cyril
C
Devaquet
Jérôme
J
Aboab
Jérôme
J
Jardin
François
F
Brochard
Laurent
L
Vieillard-Baron
Antoine
A
D000142:Acidosis, Respiratory / Q000209:etiology; D000208:Acute Disease; D000368:Aged; D000704:Analysis of Variance; D003422:Critical Care / Q000379:methods; D017548:Echocardiography, Transesophageal; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000175:diagnosis / Q000209:etiology*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000379:methods; D011446:Prospective Studies; D012126:Respiratory Dead Space; D012128:Respiratory Distress Syndrome / Q000150:complications / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D056152:Respiratory Rate; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D013990:Tidal Volume; D018497:Ventricular Dysfunction, Right / Q000175:diagnosis / Q000209:etiology*