Efeitos da hiperóxia sobre a oxigenação cerebral pré-frontal durante o exercício progressivo em pacientes com doença pulmonar obstrutiva crônica moderada à grave
Data
2012-02-29
Autores
Oliveira, Mayron Faria 
Orientadores
Neder, José Alberto
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
As variações (∆) na oxigenação cerebral (COx) durante o exercício são moduladas pelo fluxo sanguíneo cerebral e pelo conteúdo arterial de O2 (CaO2), porém, não se sabe ainda como a ∆COx poderia (i) ser modificada durante o exercício em pacientes com doença pulmonar obstrutiva crônica (DPOC) não hipoxêmica e (ii)
qual a sua resposta à hiperóxia (HiOX, FiO2 = 0,4). Vinte pacientes do sexo masculino, não hipercápnicos, portadores de DPOC (VEF1 = 47,2 ± 11,5 % predito)
e nove indivíduos saudáveis, realizaram teste de exercício sob HiOX e normóxia (NOX). A ∆COx foi mensurada pela espectroscopia de raios quasi infravermelhos (alterações na HbO2) e o débito cardíaco (QT) por impedância cardíaca. Reduções significativas na SpO2 foram encontradas em 8/20 pacientes (pico SpO2 = 86 ± 2%
vs. 96 ± 2% nos grupos Dessaturador e Não-Dessaturador, respectivamente). Em NOX, ∆COx foi menor no grupo Dessaturador versus Não-Dessaturador e Controle. Em contrapartida, a pressão arterial média (PAM) foi maior no grupo Dessaturador (p<0,05). Incrementos na SpO2 com HiOX foi significativamente maior no grupo Dessaturador (86 ± 2% vs. 99 ± 1 %). Interessantemente, incrementos significantes na ∆COx, foram observadas somente neste grupo (0,52 ± 0,20 vs. 2,09 ± 0,42; p<0,01). Não foi observado diferença significativa do efeito da HiOX no QT nos grupos controle e DPOC (Não-Dessaturador e Dessaturador). Entretanto, a PAM apresentou queda no grupo Dessaturador (p<0,05). Concluiu-se que a ∆COx está comprometida em pacientes com DPOC que dessaturaram durante exercício progressivo, mesmo que não elegíveis para oxigenioterapia crônica domiciliar. A suplementação de O2 (FiO2 = 0,40) foi capaz de corrigir essas anormalidades, as quais parecem estar relacionadas diretamente ao incremento do CaO2.
Background: The rate of change (∆) in cerebral oxygenation (COx) during exercise is critically influenced by cerebral blood flow and arterial O2 content (CaO2). It is currently unclear whether ∆COx would (i) be impaired during exercise in patients with crhonic obstructive pulmonary disease (COPD) who are not overtly hypoxaemic and (ii) improve with hyperoxia (FiO2 = 0.40) in this patients. Methods: Twenty non-hypercapnic males with COPD (FEV1 = 47.2 ± 11.5 % predicted) and nine controls underwent incremental exercise tests under hyperoxia (HiOX) and normoxia (NOX). ∆COx was determined by near infrared spectroscopy (fold-changes in O2Hb) and cardiac output (QT) by impedance cardiography. Results: A significant drop in SpO2 was found in 8/20 patients (peak SpO2 = 86% ± 2% vs. 96 ± 2 % for “desaturators” [DESAT] and “non-desaturators” [NONDESAT], respectively). In NOX, ∆COx was lower in DESAT versus NONDESAT and controls; in contrast, mean arterial pressure (MAP) was higher in the former group (p<0.05), Increases in SpO2 with HiOX were particulary pronounced in DESAT (86% ± 2 vs 99 ± 1 %); interestingly, a significant improvement in ∆COx was found only in this group (0.57± 0.20 to 2.09 ± 0.42; p<0.05). There was no significant effect of HiOX on QT in control and COPD groups; MAP, however, decreased in DESAT (p<0.05). Conclusions: ∆COx was impaired in patients with COPD who desaturated during progressive exercise even if they are not entitled to long-term O2 therapy. O2 supplementation (FiO2 = 0.40) is able to correct for these abnormalities, an effect that was related to enhaced CaO2 rather than improved cerebral haemodinamics.
Background: The rate of change (∆) in cerebral oxygenation (COx) during exercise is critically influenced by cerebral blood flow and arterial O2 content (CaO2). It is currently unclear whether ∆COx would (i) be impaired during exercise in patients with crhonic obstructive pulmonary disease (COPD) who are not overtly hypoxaemic and (ii) improve with hyperoxia (FiO2 = 0.40) in this patients. Methods: Twenty non-hypercapnic males with COPD (FEV1 = 47.2 ± 11.5 % predicted) and nine controls underwent incremental exercise tests under hyperoxia (HiOX) and normoxia (NOX). ∆COx was determined by near infrared spectroscopy (fold-changes in O2Hb) and cardiac output (QT) by impedance cardiography. Results: A significant drop in SpO2 was found in 8/20 patients (peak SpO2 = 86% ± 2% vs. 96 ± 2 % for “desaturators” [DESAT] and “non-desaturators” [NONDESAT], respectively). In NOX, ∆COx was lower in DESAT versus NONDESAT and controls; in contrast, mean arterial pressure (MAP) was higher in the former group (p<0.05), Increases in SpO2 with HiOX were particulary pronounced in DESAT (86% ± 2 vs 99 ± 1 %); interestingly, a significant improvement in ∆COx was found only in this group (0.57± 0.20 to 2.09 ± 0.42; p<0.05). There was no significant effect of HiOX on QT in control and COPD groups; MAP, however, decreased in DESAT (p<0.05). Conclusions: ∆COx was impaired in patients with COPD who desaturated during progressive exercise even if they are not entitled to long-term O2 therapy. O2 supplementation (FiO2 = 0.40) is able to correct for these abnormalities, an effect that was related to enhaced CaO2 rather than improved cerebral haemodinamics.
Descrição
Citação
OLIVEIRA, Mayron Faria. Efeitos da hiperóxia sobre a oxigenação cerebral pré-frontal durante o exercício progressivo em pacientes com doença pulmonar obstrutiva crônica moderada à grave. Dissertação (Mestrado em Ciências) - Escola Paulista de Medicina, Universidade Federal de São Paulo (UNIFESP), São Paulo, 2011.