Positive end-expiratory pressure and variable ventilation in lung-healthy rats under general anesthesia.
OBJECTIVE
Variable ventilation (VV) seems to improve respiratory function in acute lung injury and may be combined with positive end-expiratory pressure (PEEP) in order to protect the lungs even in healthy subjects. We hypothesized that VV in combination with moderate levels of PEEP reduce the deterioration of pulmonary function related to general anesthesia. Hence, we aimed at evaluating the alveolar stability and lung protection of the combination of VV at different PEEP levels.


METHODS
Randomized experimental study.


METHODS
Animal research facility.


METHODS
Forty-nine male Wistar rats (200-270 g).


METHODS
Animals were ventilated during 2 hours with protective low tidal volume (VT) in volume control ventilation (VCV) or VV and PEEP adjusted at the level of minimum respiratory system elastance (Ers), obtained during a decremental PEEP trial subsequent to a recruitment maneuver, and 2 cmH2O above or below of this level.


RESULTS
Ers, gas exchange and hemodynamic variables were measured. Cytokines were determined in lung homogenate and plasma samples and left lung was used for histologic analysis and diffuse alveolar damage scoring. A progressive time-dependent increase in Ers was observed independent on ventilatory mode or PEEP level. Despite of that, the rate of increase of Ers and lung tissue IL-1 beta concentration were significantly lower in VV than in VCV at the level of the PEEP of minimum Ers. A significant increase in lung tissue cytokines (IL-6, IL-1 beta, CINC-1 and TNF-alpha) as well as a ventral to dorsal and cranial to caudal reduction in aeration was observed in all ventilated rats with no significant differences among groups.


CONCLUSIONS
VV combined with PEEP adjusted at the level of the PEEP of minimal Ers seemed to better prevent anesthesia-induced atelectasis and might improve lung protection throughout general anesthesia.
Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Luciana M
LM
Camilo
Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Mariana B
MB
Ávila
Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Luis Felipe S
LF
Cruz
Laboratory of Pulmonary Engineering, Biomedical Engineering Program, Alberto Luis Coimbra Institute of Post-Graduation and Research in Engineering, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Gabriel C M
GC
Ribeiro
Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Medicine, Technische Universität Dresden, Germany.
Peter M
PM
Spieth
Department of Anesthesiology and Intensive Care Medicine, University of Leipzig, Leipzig, Germany.
Andreas A
AA
Reske
Cardio-Pulmonary Department, Pulmonary Division, Hospital das Clínicas, Universidade de São Paulo, São Paulo, Brazil.
Marcelo
M
Amato
Laboratory of Pulmonary Engineering, Biomedical Engineering Program, Alberto Luis Coimbra Institute of Post-Graduation and Research in Engineering, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Antonio
A
Giannella-Neto
Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Walter A
WA
Zin
Laboratory of Respiration Physiology, Carlos Chagas Filho Institute of Biophysics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Laboratory of Pulmonary Engineering, Biomedical Engineering Program, Alberto Luis Coimbra Institute of Post-Graduation and Research in Engineering, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Alysson R
AR
Carvalho
D000768:Anesthesia, General; D000818:Animals; D006439:Hemodynamics; D008297:Male; D011175:Positive-Pressure Respiration; D011650:Pulmonary Alveoli / Q000502:physiology*; D001261:Pulmonary Atelectasis / Q000517:prevention & control*; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar