[Pulmonary mechanics, oxygenation index, and alveolar ventilation in patients with two controlled ventilatory modes. A comparative crossover study].
OBJECTIVE
To compare in a crossover study pulmonary mechanics, oxigenation index (PaO(2)/FiO(2)), and partial pressure of CO(2) in arterial blood (PaCO(2)) in patients with mechanical ventilation in two controlled ventilatory modes.


METHODS
Intensive care unit of a university affiliated hospital.


METHODS
Prospective crossover clinical trial.


METHODS
A total 114 consecutive patients were admitted to the intensive care unit (ICU) under controlled mechanical ventilation with SaO(2) >90% and FiO(2) <0.5 and assigned by random allocation to either volume control (VC) and constant inspiratory flow (square flow curve) (group I) or pressure control mode (PC) (group II). Both groups were ventilated with tidal volume (Vt) of 7 ml/kg, respiratory rate (RR) 14/min, inspiratory-expiratory ratio 1:2 (I:E), PEEP 5 cm H(2)O, and FiO(2) 0.4. After 15 min of mechanical ventilation, pulmonary mechanics, oxygenation index (OI), and PaCO(2) were measured and registered, and ventilatory mode was switched to PC mode in group I and to VC in group II, maintaining the same ventilator settings. Pulmonary mechanics, OI, and PaCO(2) were again registered after 15 min of ventilation.


RESULTS
Peak inspiratory pressure (PIP) was higher in VC than in PC (31.5 vs 26 cm H(2)O), which resulted in a significant increase in transpulmonary pressure amplitude difference (DP) (25 vs 19 cm H(2)O). Mean airway pressure (MAP) and OI were lower in VC than in PC (11.5 vs 12 cm H(2)O, and 198.5 vs 215, respectively). Dynamic compliance (DynC) was lower in VC than in PC (20 vs 26 ml/cm H(2)O), p < 0.05 for all values. At constant ventilator settings in the same patient, PC and not VC ventilation decreases PIP (which results in smaller transpulmonary pressure amplitude difference), increases MAP, and DynC and improves the oxygenation index.
Castañón-González
Jorge A
JA
Unidad de Cuidados Intensivos y Medicina Crítica, Hospital de Especialidades "Dr. Bernardo Sepúlveda Gutiérrez," Centro Médico Nacional Siglo XXI, IMSS, México, D.F. México. jorgec@prodigy.net.mx
León-Gutiérrez
Marco Antonio
MA
Gallegos-Pérez
Humberto
H
Pech-Quijano
Jorge
J
Martínez-Gutíerrez
Miguel
M
Olvera-Chávez
Alfredo
A
D000328:Adult; D000368:Aged; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011446:Prospective Studies; D011650:Pulmonary Alveoli / Q000502:physiology*; D012121:Respiration, Artificial / Q000379:methods*; D015656:Respiratory Mechanics