[The protective effects and mechanism of hypercapnia on acute lung injury].
OBJECTIVE
To explore the protective effects of hypercapnia on acute lung injury (ALI) and the possible mechanisms.


METHODS
Twenty-four healthy New Zealand white rabbits were involved in this study, and randomly divided to three groups, a control group, a therapeutic group, and a prophylactic group (n=8, each). Lipopolysaccharide (1 mg/kg) was injected intravenously to establish the ALI model. Blood gas analysis and artery pressure were monitored. IL-8 and TNF-alpha in the serum and bronchoalveolar lavage fluid (BALF), wet weight/dry weigh (W/D), index of quantitative assessment of histological lung injury (IQA), myeloperoxidase (MPO) and malondialdehyde (MDA) activity in the lung tissue were measured. Apoptosis index of neutrophils were determined.


RESULTS
(1) The mean artery pressure, heart rate, PaCO2, and PaO2/FiO2 changed in the ALI model of the therapeutic group and the prophylactic group [(79+/-6) mm Hg (1 mm Hg=0.133 kPa), (180+/-10)/min, (99+/-13) mm Hg, 250+/-26, (80+/-9) mm Hg, (181+/-12)/min, (95+/-11) mm Hg, 241+/-56, respectively]. In the control group, they were (66+/-10) mm Hg, (139+/-13)/min, (31+/-4) mm Hg, 182+/-35, respectively. The differences were significant compared with the control group (t=4.05, 26.32, 5.36, 28.15, 12.54, 11.07, 16.13, 12.36, P<0.05, 0.01). (2) The levels of W/D, MPO, and MDA in the therapeutic group and the prophylactic group were 1.98+/-0.28, 1.87+/-0.30, (6.1+/-1.6) U/g, (5.8+/-1.5) U/g, (20+/-5) mg/L, (19+/-4) mg/L; while in the control group, they were [2.43+/-0.26, (9.0+/-1.3) U/g, (36+/-8) mg/L] respectively. The difference was significant (t=11.07, 24.46, 2.35, 9.63, 12.34, 25.32, P<0.05, 0.01). (3) The levels of IL-8 and TNF-alpha in the serum and BALF and the apoptosis index in the three groups were (50+/-8) ng/ml, (103+/-49) ng/ml, (94+/-16) ng/ml, (44+/-9) ng/ml, (38+/-9)%, (56+/-5)%, (49+/-7) ng/ml, (96+/-50) ng/ml, (91+/-14) ng/ml, (39+/-6) ng/ml, (39+/-10)%, (55+/-10)%, (91+/-43) ng/ml, (177+/-60) ng/ml, (162+/-15) ng/ml, (67+/-7) ng/ml, (19+/-7)%, (43+/-7)%, respectively. The difference was significant among the three groups (t=7.12, 5.55, 7.30, 3.93, 13.08, 8.00, P<0.05, 0.01 respectively). (4) The apoptosis index of neutrophils was negatively correlated with the levels of IL-8 in the serum and BALF (r=-0.73, -0.72, -0.52, -0.64, -0.73, -0.56, all P<0.05), and the levels of TNF-alpha in the serum and BALF (r=-0.57, -0.78, -0.69, -0.75, -0.82, -0.84, all P<0.05).


CONCLUSIONS
Hypercapnia does not affect hemodynamics and has protective effects on ALI.
Li
Qi-hao
QH
Department of Respiratory Medicine, The 2nd Affiliated Hospital, Kunming Medical College, Kunming, Yunnan 650101, China.
Dong
Zhao-xing
ZX
Zhang
Tao
T
Chai
Yan-ling
YL
Zhong
Hong
H
Wang
Ying
Y
Lei
Wen
W
Hai
Bing
B
Li
Zhen-kun
ZK
Wu
Wen-juan
WJ
Rao
Ming-qing
MQ
D055371:Acute Lung Injury / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology*; D000818:Animals; D017209:Apoptosis; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D004195:Disease Models, Animal; D005260:Female; D006439:Hemodynamics; D006935:Hypercapnia / Q000097:blood / Q000378:metabolism / Q000503:physiopathology*; D016209:Interleukin-8 / Q000097:blood; D008070:Lipopolysaccharides; D008168:Lung / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D011817:Rabbits; D011897:Random Allocation; D012129:Respiratory Function Tests; D013990:Tidal Volume
D016209:Interleukin-8; D008070:Lipopolysaccharides; D008315:Malondialdehyde; D009195:Peroxidase