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Avaliação da hiperémia reativa pós-oclusiva por videocapilaroscopia
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Resumo(s)
Sabe-se que a disfunção microvascular precede a doença cardiovascular em vários anos,
pelo que a sua deteção atempada permite a adoção de importantes estratégias preventivas.
Pode ser facilmente avaliada a nível experimental através da oclusão transitória de uma
artéria de um membro e da quantificação da hiperémia reativa pós-oclusiva (PORH)
subsequente. A microcirculação cutânea é considerada suficientemente representativa da
função microvascular global, com a vantagem óbvia de ser avaliada por várias tecnologias
não invasivas, incluindo a videocapilaroscopia da prega ungueal (NVC). A NVC é um
instrumento valioso para detetar anomalias microvasculares presentes nas doenças do tecido
conjuntivo, mas também pode detetar alterações morfológicas precoces na hipertensão e na
obesidade. No entanto, o seu potencial para avaliar condições hemodinâmicas tem sido pouco
explorado. O nosso objetivo foi avaliar a PORH em indivíduos jovens saudáveis caucasianos
com a NVC, utilizando a fotopletismografia (PPG) como técnica de referência. Catorze
voluntários saudáveis (21,0 ± 1,2 anos) participaram neste estudo após terem dado o seu
consentimento informado. Os voluntários foram submetidos a uma oclusão padrão num
membro superior aleatorizado, enquanto na posição sentada, da seguinte forma: 5 minutos
de repouso com ambos os braços ao nível do coração (baseline), 3 minutos de oclusão a 200
mmHg com uma manga de pressão (provocação) e 5 minutos de recuperação (recuperação).
Os capilares da prega ungueal do quarto dedo foram continuamente visualizados com um
microscópio digital USB de baixo custo. Cada gravação de vídeo NVC foi decomposta nos
seus frames, de onde se calculou o índice de viabilidade tecidual (TiVi). Como expectável,
durante a oclusão a perfusão cutânea diminuiu significativamente com ambas as técnicas em
ambos os membros, e aumentou significativamente após a libertação da manga. Apesar da
semelhança entre os seus perfis, as alterações de perfusão detetadas com o índice TiVi
ocorreram significativamente mais tarde que as detetadas no sinal de PPG, sugerindo uma
menor sensibilidade quantitativa. Estes resultados sugerem que a perfusão cutânea pode ser
facilmente avaliada com microscópios digitais USB de baixo custo, embora sejam necessários
mais estudos para comparar o seu desempenho com o de outras tecnologias óticas.
Microvascular dysfunction is known to precede cardiovascular disease by several years, so its early detection allows important preventive strategies to be adopted. It can be easily assessed experimentally by transiently occluding a limb artery and quantifying the subsequent post occlusive reactive hyperaemia (PORH). Cutaneous microcirculation is considered sufficiently representative of overall microvascular function, with the obvious advantage of being assessed by various non-invasive technologies, including nailfold videocapillaroscopy (NVC). NVC is a valuable tool for detecting microvascular abnormalities present in connective tissue diseases, but it can also detect early morphological changes in hypertension and obesity. However, its potential for assessing haemodynamic conditions has been little explored. Our aim was to assess PORH in healthy young caucasian individuals with NVC, using photoplethysmography (PPG) as the reference technique. Fourteen healthy volunteers (21.0 ± 1.2 years) took part in this study after giving their informed consent. The volunteers underwent a standard occlusion on a randomised upper limb, while in the sitting position, as follows: 5 minutes of rest with both arms at heart level (baseline), 3 minutes of occlusion at 200 mmHg with a pressure cuff (provocation) and 5 minutes of recovery (recovery). The capillaries in the nail fold of the fourth finger were continuously visualised with a low-cost USB digital microscope. Each NVC video recording was broken down into its frames, from which the tissue viability index (TiVi) was calculated. As expected, during occlusion skin perfusion decreased significantly with both techniques in both limbs, and increased significantly after sleeve release. Despite the similarity between their profiles, the perfusion changes detected with the TiVi index occurred significantly later than those detected in the PPG signal, suggesting a lower quantitative sensitivity. These results suggest that skin perfusion can be easily assessed with low-cost USB digital microscopes, although more studies are needed to compare their performance with that of other optical technologies.
Microvascular dysfunction is known to precede cardiovascular disease by several years, so its early detection allows important preventive strategies to be adopted. It can be easily assessed experimentally by transiently occluding a limb artery and quantifying the subsequent post occlusive reactive hyperaemia (PORH). Cutaneous microcirculation is considered sufficiently representative of overall microvascular function, with the obvious advantage of being assessed by various non-invasive technologies, including nailfold videocapillaroscopy (NVC). NVC is a valuable tool for detecting microvascular abnormalities present in connective tissue diseases, but it can also detect early morphological changes in hypertension and obesity. However, its potential for assessing haemodynamic conditions has been little explored. Our aim was to assess PORH in healthy young caucasian individuals with NVC, using photoplethysmography (PPG) as the reference technique. Fourteen healthy volunteers (21.0 ± 1.2 years) took part in this study after giving their informed consent. The volunteers underwent a standard occlusion on a randomised upper limb, while in the sitting position, as follows: 5 minutes of rest with both arms at heart level (baseline), 3 minutes of occlusion at 200 mmHg with a pressure cuff (provocation) and 5 minutes of recovery (recovery). The capillaries in the nail fold of the fourth finger were continuously visualised with a low-cost USB digital microscope. Each NVC video recording was broken down into its frames, from which the tissue viability index (TiVi) was calculated. As expected, during occlusion skin perfusion decreased significantly with both techniques in both limbs, and increased significantly after sleeve release. Despite the similarity between their profiles, the perfusion changes detected with the TiVi index occurred significantly later than those detected in the PPG signal, suggesting a lower quantitative sensitivity. These results suggest that skin perfusion can be easily assessed with low-cost USB digital microscopes, although more studies are needed to compare their performance with that of other optical technologies.
Descrição
Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, 2024, Universidade de Lisboa, Faculdade de Farmácia.
Palavras-chave
Microcirculação Hiperémia reativa pós-oclusiva Videocapilaroscopia da prega ungueal Microscópio digital USB Fotopletismografia Mestrado Integrado - 2024