Effects of overinflation on procollagen type III expression in experimental acute lung injury.
BACKGROUND
In acute lung injury (ALI), elevation of procollagen type III (PC III) occurs early and has an adverse impact on outcome. We examined whether different high-inflation strategies of mechanical ventilation (MV) in oleic acid (OA) ALI alter regional expression of PC III.


METHODS
We designed an experimental, randomized, and controlled protocol in which rats were allocated to two control groups (no injury, recruited [alveolar recruitment maneuver after tracheotomy without MV; n = 4 rats] and control [n = 5 rats]) or four injured groups (one exposed to OA only [n = 10 rats] and three OA-injured and ventilated). The three OA-injured groups were ventilated for 1 hour according to the following strategies: LVHP-S (low volume-high positive end-expiratory pressure [PEEP], supine; n = 10 rats, tidal volume [VT] = 8 ml/kg, PEEP = 12 cm H2O), HVLP-S (high volume-low PEEP, supine; n = 10 rats, VT = 20 ml/kg, PEEP = 5 cm H2O), and HVLP-P (high volume-low PEEP, prone; n = 10 rats). Northern blot analysis for PC III and interleukin-1-beta (IL-1beta) and polymorphonuclear infiltration index (PMI) counting were performed in nondependent and dependent regions. Regional differences between groups were assessed by two-way analysis of variance after logarithmic transformation and post hoc tests.


RESULTS
A significant interaction for group and region effects was observed for PC III (p = 0.012) with higher expression in the nondependent region for HVLP-S and LVHP-S, intermediate for OA and HVLP-P, and lower for control (group effect, p < 0.00001, partial eta2 = 0.767; region effect, p = 0.0007, partial eta2 = 0.091). We found high expression of IL-1beta (group effect, p < 0.00001, partial eta2 = 0.944) in the OA, HVLP-S, and HVLP-P groups without regional differences (p = 0.16). PMI behaved similarly (group effect, p < 0.00001, partial eta2 = 0.832).


CONCLUSIONS
PC III expression is higher in nondependent regions and in ventilatory strategies that caused overdistension. This response was partially attenuated by prone positioning.
de Carvalho
Maria-Eudóxia Pilotto
ME
Intensive Care Unit, Centro de Tratamento e Pesquisa, Hospital do Câncer, Fundação Antônio Prudente, São Paulo, Brazil. michel@estadao.com.br
Dolhnikoff
Marisa
M
Meireles
Sibele Inácio
SI
Reis
Luiz Fernando Lima
LF
Martins
Milton Arruda
MA
Deheinzelin
Daniel
D
D000818:Animals; D024061:Collagen Type III / Q000096:biosynthesis* / Q000235:genetics; D004195:Disease Models, Animal; D053583:Interleukin-1beta / Q000096:biosynthesis / Q000235:genetics; D019301:Oleic Acid; D011175:Positive-Pressure Respiration / Q000009:adverse effects* / Q000379:methods; D012333:RNA, Messenger / Q000096:biosynthesis; D011897:Random Allocation; D051381:Rats; D012128:Respiratory Distress Syndrome / Q000139:chemically induced / Q000378:metabolism* / Q000628:therapy; D014158:Transcription, Genetic
D024061:Collagen Type III; D053583:Interleukin-1beta; D012333:RNA, Messenger; D019301:Oleic Acid