title: Influence of hyperoxia and mechanical ventilation in lung inflammation and diaphragm function in aged versus adult rats.
abstract: Although assist ventilation with FIO2 0.21 is the preferable mode of ventilation in the intensive care unit, sometimes controlled ventilation with hyperoxia is needed. But the impact of this setting has not been extensively studied in elderly subjects. We hypothesized that a high fraction of inspired oxygen (FiO(2)) and controlled mechanical ventilation (CMV) is associated with greater deleterious effects in old compared to adult subjects. Adult and old rats were submitted to CMV with low tidal volume (6 ml/kg) and FiO(2) 1 during 3 or 6 h. Arterial blood gas samples were measured at 0, 60 and 180 min (four groups: old and adult rats, 3 or 6 h of CMV), and additionally at 360 min (two groups: old and adult rats, 6 h of CMV). Furthermore, total protein content (TPC) and tumor necrosis factor-alpha (TNF-α) in bronchoalveolar lavage were assessed; lung tissue was used for malondialdehyde and histological analyses, and the diaphragm for measurement of contractile function. Arterial blood gas analysis showed an initial (60 min) greater PaO(2) in elderly versus adult animals; after that time, elderly animals had lowers pH and PaO(2), and greater PaCO(2). After 3 h of CMV, TPC and TNF-α levels were higher in the old compared with the adult group (P < 0.05). After 6 h of MV, malondialdehyde was significantly higher in elderly compared with the adult animals (P < 0.05). Histological analysis showed leukocyte infiltration and edema, greater in old animals. In diaphragm, twitch contraction with caffeine significantly declined after 6 h of CMV only for the elderly group. These data support the hypothesis that relatively short-term CMV with low tidal volume and hyperoxia has greatest impact in elderly rats, decreasing diaphragmatic contractile function and increasing lung inflammation.
authors.affiliation: Centro de Estudo, Diagnóstico e Investigação de Hipertermia Maligna (CEDHIMA), Disciplina de Anestesiologia, Dor e Terapia Intensiva, Universidade Federal de São Paulo, Rua Napoleão de Barros, 715, 5 andar, CEP 04024-002, São Paulo, SP, Brazil.
authors.forename: P V
authors.initials: PV
authors.lastname: Andrade
authors.forename: J M
authors.initials: JM
authors.lastname: dos Santos
authors.forename: H C A
authors.initials: HC
authors.lastname: Silva
authors.forename: D D
authors.initials: DD
authors.lastname: Wilbert
authors.forename: S S
authors.initials: SS
authors.lastname: Cavassani
authors.forename: I S
authors.initials: IS
authors.lastname: Oliveira-Júnior
mesh_terms: D000367:Age Factors; D000818:Animals; D001784:Blood Gas Analysis; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D003964:Diaphragm / Q000503:physiopathology*; D004195:Disease Models, Animal; D018496:Hyperoxia / Q000097:blood / Q000150:complications* / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D018836:Inflammation Mediators / Q000378:metabolism; D008168:Lung / Q000276:immunology / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D009119:Muscle Contraction; D053717:Pneumonia, Ventilator-Associated / Q000097:blood / Q000209:etiology* / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D012121:Respiration, Artificial / Q000009:adverse effects*; D012307:Risk Factors; D013990:Tidal Volume; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D018836:Inflammation Mediators; D014409:Tumor Necrosis Factor-alpha; D008315:Malondialdehyde