Navegando por Palavras-chave "Hiperóxia"

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    Contribuição tônica do quimiorreflexo carotídeo para o controle vagal cardíaco no repouso, ortostatismo e durante a recuperação após o exercício em pacientes com hipertensão arterial pulmonar
    (Universidade Federal de São Paulo (UNIFESP), 2018-11-28) Ribeiro, Marcelle de Paula [UNIFESP]; Silva, Bruno Moreira [UNIFESP]; http://lattes.cnpq.br/6680100353729718; http://lattes.cnpq.br/7001582128466985; Universidade Federal de São Paulo (UNIFESP)
    Pulmonary Arterial Hypertension (PAH) is a rapidly progressive disease with multiple etiologies and an extremely poor prognosis. Patients with PAH present marked autonomic dysfunction, characterized by increase in sympathetic activity and reduction in vagal activity to cardiovascular system. The augmented peripheral chemoreflex responsiveness seems to play a role on autonomic dysfunction in PAH. However, remains unclear the tonic contribution of the peripheral chemoreflex to cardiac vagal control in PAH. We hypothesized that the carotid chemoreflex would impair the cardiac vagal control at rest and during orthostatic challenge in patients with PAH and this impairment would be increased during post-exercise recovery, since evidences have shown that the peripheral chemoreflex might be sensitized by different substances released during exercise. To test these hypothesis, 20 patients with established PAH and 13 age and sex matched healthy controls (CON) took part of the study. Both groups underwent to peripheral chemoreflex sensitivity evaluation through transient hypoxic inhalation. Afterwards, they were randomly exposed to 1) hyperoxia (carotid chemoreflex inhibition, 100% O2), or 2) normoxia (control session, 21% O2); during cardiac vagal modulation assessment (baroreflex sensitivity [BRS]; heart rate variability [HRV]; heart rate recovery [HRR]). Data are shown as mean ± SD and comparisons between gases and groups were acquired using the Mixed Linear Model (p ≤ 0.05). The PAH showed peripheral chemoreflex sensitivity to hypoxia compared to CON (P=0.01). During rest, hyperoxia increased vagal indexes of HRV and BRS in both PAH and CON groups, and this increase was similar among groups, indicating that the carotid chemoreflex tonically modulates the cardiac vagal control in healthy subjects and patients with PAH. During orthostatic challenge, hyperoxia increased BRS in both groups and this effect was greater in PAH, indicating that the carotid chemoreflex is sensitized in PAH and contributes to impaired BRS during orthostatic challenge in this group. During post-exercise recovery, hyperoxia increased HRR and HRV in both groups and this effect was greater in PAH, indicating that the carotid chemoreflex is sensitized in PAH and contributes to impaired post-exercise vagal reactivation in this group. Taking together, the results suggest that the carotid chemoreflex tonically modulate the cardiac vagal control in healthy humans and contributes to cardiac vagal dysfunction during orthostatism and during post-exercise recovery in patients with PAH.
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    Efeito da hiperóxia na oxigenação muscular periférica no início do exercício dinâmico de alta intensidade em pacientes não-hipoxêmicos ou levemente hipoxêmicos com Doença Pulmonar Obstrutiva Crônica (DPOC)
    (Universidade Federal de São Paulo (UNIFESP), 2009-10-28) Siqueira, Ana Cristina Barroso de [UNIFESP]; Neder, José Alberto [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    There is convincing evidence that impaired microvascular O2 delivery (Q LO2mv) to the peripheral muscles limits the rate of increase in pulmonary O2 uptake ( O2p) at the onset of supra-gas exchange threshold exercise in patients with chronic obstructive pulmonary disease (COPD). It is currently unclear, however, whether O2 supplementation could actually improve Q LO2mv thereby accelerating O2p kinetics in patients who are not overtly hypoxemic (PaO2 > 60 mmHg). We therefore investigated the effects of hyperoxia (HiOX= 50% O2) and normoxia (NOX) on the kinetics of O2p and fractional O2 extraction in the vastus lateralis ( [deoxy- Hb+Mb] by near-infrared spectroscopy) in 11 non- or mildly-hypoxemic patients. HiOX increased exercise tolerance compared to NOX (P<0.05). At the on-exercise transient, however, HiOX was associated with faster [deoxy-Hb+Mb] kinetics (= 4.8 } 2.4 s vs. 6.7 } 3.0 s; P<0.05) and a response govershoot h in 7/11 patients suggesting impaired Q LO2mv. Subsequently, however, [deoxy-Hb+Mb] decreased to lower steady-state values compared to NOX in 9/11 patients (P<0.05). As a likely consequence of these opposite effects of HiOX on Q LO2mv (i.e., early impairment followed by later improvement), O2p kinetics were accelerated in 6 but slowed in 5 patients. Interestingly, patients in whom HiOX accelerated O2p kinetics showed consistently-larger reductions in gsteady-state h ..[deoxy-Hb+Mb] compared to their counterparts (HiOX . NOX= -23.4 (-55.5 to -5.8) ƒÊM/cm vs. -0.62 (-22.6 to 10.7) ƒÊM/cm; p<0.05). In conclusion, HiOX can transitorily impair the convective flow of O2 to the working peripheral muscles at the onset of heavy intensity exercise in patients with COPD who are not overtly hypoxemic. This effect, however, might be (over)compensated by a subsequent increase in local O2 availability in selected patients. These data seem to provide a mechanistic explanation for the heterogeneous effects of HiOX on O2p kinetics in this patient sub-population.
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    Efeitos agudos da inalacao da mistura helio-hiperoxia, comparativamente a hiperoxia, nas respostas cardiorrespiratorias, durante o exercicio incremental em pacientes hipoxemicos com doenca pulmonar obstrutiva cronica
    (Universidade Federal de São Paulo (UNIFESP), 2011) Nunes, Marcos Eduardo Boquembuzo [UNIFESP]
    O uso da mistura helio (He)-oxigenio 21% (heliox) resulta em melhora da capacidade de exercicio, com reducao da hiperinsuflacao dinamica durante o exercicio incremental em pacientes nao hipoxemicos com DPOC. A combinacao do He com fracoes mais elevadas de oxigenio (FiO2 entre 28 e 40%)pode promover potencializacao adicional nesta populacao, em relacao a misturas unicamente hiperoxicas. Contudo, nao ha estudos previos que tenham especificamente avaliado os efeitos do heliox em pacientes hipoxemicos com DPOC submetidos ao teste de exercicio incremental. Portanto, o objetivo deste estudo foi avaliar os efeitos agudos da inalacao da mistura HeHox (60%He:40%O2), comparativamente a Hox (60%N2:40%O2) na capacidade de exercicio, assim como nas respostas metabolicas, ventilatorias e cardiovasculares, em pacientes estaveis com DPOC hipoxemica. Atraves de um estudo duplo-cego, cruzado e controlado foram aleatorizados 24 pacientes do sexo masculino, alocados para realizar dois testes com carga progressiva em cicloergometro com as misturas propostas pelo estudo. Antes de cada teste, os pacientes realizaram provas espirometricas inalando as misturas gasosas distintas e durante os testes realizavam medidas seriadas de capacidade inspiratoria (CI) para estimativa do grau de hiperinsuflacao pulmonar dinamica e as variaveis cardiovasculares centrais (coletadas em 13 dos 24 pacientes da amostra) foram obtidas atraves da cardiografia por bioimpedancia transtoracica Alem disso, foi realizada uma analise dividindo a amostra em pacientes normocapnicos (n=14) e hipercapnicos (n=10). As variaveis cardiorrespiratorias foram avaliadas durante a isocarga (30 watts) e no pico do exercicio. Quando comparada a mistura HeHox, em relacao a Hox, observamos: (i) maior capacidade de exercicio (54 ± 26 vs. 48 ± 23 W; p<0,0001); (ii) maiores valores da CI (1,53 ±0,28 vs. 1,46 ± 0,34 L; p<0,01) e menores valores do Volume Expiratorio Final (5,57 ± 1,12 vs. 5,65 ± 1,13 L; p<0,008), no pico dos testes incrementais. Em relacao aos dados cardiovasculares foi verificado: maiores valores de Debito Cardiaco (9,62 ± 1,36 vs 8,71 ± 1,96 L/min; p<0,03) e Volume Sistolico (92,26 ± 8,97 vs 84,22 ± 12,78 mL; p<0,02). Na analise dos grupos classificados pelos niveis de PaCO2, os pacientes hipercapnicos alcancaram menores valores de carga maxima no pico dos testes incrementais em ambas as intervencoes, no entanto, tais diferencas nao foram significantes. A regressao linear multipla estabeleceu que o ganho adicional na capacidade de exercicio promovida pela mistura de baixa densidade sobre a mistura hiperoxica, relacionou-se com (r2= 0,61) maiores valores absolutos de massa magra (p<0,0001). Em resumo, a inalacao da mistura HeHox em pacientes com DPOC hipoxemica submetidos ao teste de exercicio incremental, comparada a mistura Hox, levou a um aumento adicional na capacidade de exercicio associada a reducao dos volumes pulmonares operantes, tanto nos pacientes hipercapnicos como normocapnicos. Alem disso, a mistura de baixa densidade promoveu uma melhora adicional nas respostas cardiocirculatorias ao exercicio, o que foi particularmente evidente nos pacientes com menor hiperinsuflacao ao repouso. A presenca de adequada massa muscular periferica foi importante para permitir um ganho na capacidade maxima de exercicio quando a mistura HeHox melhorou o desempenho ventilatorio neste grupo de pacientes