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Purpose: To evaluate whether a subtraction CT angiography (sCTA) perfusion score may have prognostic value in patients with COVID-19 pneumonia. Method: This prospective cohort study included adult patients with RT-PCR-confirmed SARS-CoV-2 infection admitted to the ED and a sCTA performed within 24 h of admission between June and September 2020. Perfusion abnormalities (PA) in areas of apparently spared lung parenchyma on conventional CT images were assessed with sCTA perfusion score. Airspace disease extension was assessed with CT severity scores, which were then correlated with clinical outcomes (admission to ICU, requirement of IMV, and death). Inter-rater reliability (IRR) was assessed using Cohen's Kappa. Independent predictors of adverse outcomes were evaluated by multivariable logistic regression analyses using the Hosmer and Lemeshow's test. Results: 191 patients were included: 112 males (58%), median age of 60.8 years (SD ± 16.0). The IRR was very high (median Kappa statistic: 0.95). No association was found between perfusion CT scores and D-dimer levels (Kendall's Tau-B coefficient = 0.08, p = 0.16) or between PaO2/FiO2 ratios and D-dimer levels (Kendall's Tau-B coefficient = -0.10, p = 0.07). Multivariate analyses adjusting for parenchymal disease extension, vascular beaded appearance, pulmonary embolism, sex, and age showed that severe PA remained a significant predictor for ICU admission (AOR: 6.25, 95% CI 2.10-18.7, p = 0.001). The overall diagnostic capacity of this model was adequate (ROC AUC: 0.83; 95% CI 0.77-0.89). Conclusions: The assessment of pulmonary perfusion abnormalities in areas of apparently spared lung parenchyma on conventional CT images via sCTA perfusion scoring has prognostic value in COVID-19 pneumonia.

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BACKGROUND: Veno-venous extracorporeal membrane oxygenation (ECMO) provides blood oxygenation and carbon dioxide removal in acute respiratory distress syndrome. However, during ECMO support, the native lungs still play an important role in gas exchange, functioning as a second oxygenator in series with ECMO. The hypoxic vasoconstriction mechanism diverts regional blood flow within the lungs away from regions with low oxygen levels, optimizing ventilation/perfusion matching. ECMO support has the potential to reduce this adaptive pulmonary response and worsen the ventilation/perfusion mismatch by raising venous oxygen partial pressure. Thus, the objective of this study was to evaluate the effect of ECMO on regional pulmonary perfusion and pulmonary hemodynamics during unilateral ventilation and posterior lung collapse. METHODS: Five Agroceres pigs were instrumented, monitored and submitted to ECMO. We used the Electrical Impedance Tomography (EIT) to evaluate lung ventilation and perfusion in all protocol steps. Effects of ECMO support on pulmonary hemodynamics and perfusion involving two different scenarios of ventilation/perfusion mismatch: (1) right-lung selective intubation inducing collapse of the normal left lung and (2) dorsal lung collapse after repeated lung lavage. Data including hemodynamics, respiratory, lung perfusion/ventilation, and laboratory data over time were analyzed with a mixed generalized model using the subjects as a random factor. RESULTS: The initiation of ECMO support provided a significant reduction in Mean Pulmonary Artery Pressure (PAPm) in both situations of ventilation/perfusion mismatch. However, distribution of lung perfusion did not change with the use of ECMO support. CONCLUSIONS: We found that the use of ECMO support with consequent increase in venous oxygen pressure induced a significant drop in PAPm with no detectable effect on regional lung perfusion in different scenarios of ventilation/perfusion mismatch.

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BACKGROUND: SARS-CoV-2 seems to affect the regulation of pulmonary perfusion. Hypoperfusion in areas of well-aerated lung parenchyma results in a ventilation-perfusion mismatch that can be characterized using subtraction computed tomography angiography (sCTA). This study aims to evaluate the efficacy of oral sildenafil in treating COVID-19 inpatients showing perfusion abnormalities in sCTA. METHODS: Triple-blinded, randomized, placebo-controlled trial was conducted in Chile in a tertiary-care hospital able to provide on-site sCTA scans and ventilatory support when needed between August 2020 and March 2021. In total, 82 eligible adults were admitted to the ED with RT-PCR-confirmed or highly probable SARS-COV-2 infection and sCTA performed within 24 h of admission showing perfusion abnormalities in areas of well-aerated lung parenchyma; 42 were excluded and 40 participants were enrolled and randomized (1:1 ratio) once hospitalized. The active intervention group received sildenafil (25 mg orally three times a day for seven days), and the control group received identical placebo capsules in the same way. Primary outcomes were differences in oxygenation parameters measured daily during follow-up (PaO2/FiO2 ratio and A-a gradient). Secondary outcomes included admission to the ICU, requirement of non-invasive ventilation, invasive mechanical ventilation (IMV), and mortality rates. Analysis was performed on an intention-to-treat basis. RESULTS: Totally, 40 participants were enrolled (20 in the placebo group and 20 in the sildenafil group); 33 [82.5%] were male; and median age was 57 [IQR 41-68] years. No significant differences in mean PaO2/FiO2 ratios and A-a gradients were found between groups (repeated-measures ANOVA p = 0.67 and p = 0.69). IMV was required in 4 patients who received placebo and none in the sildenafil arm (logrank p = 0.04). Patients in the sildenafil arm showed a significantly shorter median length of hospital stay than the placebo group (9 IQR 7-12 days vs. 12 IQR 9-21 days, p = 0.04). CONCLUSIONS: No statistically significant differences were found in the oxygenation parameters. Sildenafil treatment could have a potential therapeutic role regarding the need for IMV in COVID-19 patients with specific perfusion patterns in sCTA. A large-scale study is needed to confirm these results. TRIAL REGISTRATION: Sildenafil for treating patients with COVID-19 and perfusion mismatch: a pilot randomized trial, NCT04489446, Registered 28 July 2020, https://clinicaltrials.gov/ct2/show/NCT04489446 .

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Las alteraciones de la relación entre la ventilación y el flujo sanguíneo (V/Q) en diversas regiones del pulmón alteran el aporte de oxígeno (O2) y remoción del dióxido de carbono (CO2) al organismo. Fisiológicamente existen diferencias regionales en la relación V/Q. Determinadas patologías pueden alterar esta relación, produciendo tres escenarios distintos: Cortocircuito (Shunt), Alteración V/Q y aumento del espacio muerto. Para evaluar estos escenarios y realizar una aproximación diagnostica son de utilidad el estudio de los gases arteriales y venosos, la diferencia alveolo arterial y la respuesta al suministrar O2

Alterations in the ventilation perfusion relationship (V/Q) in various lung regions alter the supply of oxygen (O2) and the removal of carbon dioxide (CO2) in the body. Physiologically, there are regional differences in the V/Q ratio. Certain pathologies can alter this relationship, producing three different scenarios: Shunt, V/Q mismach and dead space increased. To evaluate these scenarios and carry out a diagnostic approach, it is useful to study arterial and venous gasometry, the alveolar arterial difference and the response to oxygen supplying.

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BACKGROUND: Subtraction CT angiography (sCTA) is a technique used to evaluate pulmonary perfusion based on iodine distribution maps. The aim of this study is to assess lung perfusion changes with sCTA seen in patients with COVID-19 pneumonia and correlate them with clinical outcomes. MATERIAL AND METHODS: A prospective cohort study was carried out with 45 RT-PCR-confirmed COVID-19 patients that required hospitalization at three different hospitals, between April and May 2020. In all cases, a basic clinical and demographic profile was obtained. Lung perfusion was assessed using sCTA. Evaluated imaging features included: Pattern predominance of injured lung parenchyma in both lungs (ground-glass opacities, consolidation and mixed pattern) and anatomical extension; predominant type of perfusion abnormality (increased perfusion or hypoperfusion), perfusion abnormality distribution (focal or diffuse), extension of perfusion abnormalities (mild, moderate and severe involvement); presence of vascular dilatation and vascular tortuosity. All participants were followed-up until hospital discharge searching for the development of any of the study endpoints. These endpoints included intensive-care unit (ICU) admission, initiation of invasive mechanical ventilation (IMV) and death. RESULTS: Forty-one patients (55.2 ± 16.5 years, 22 men) with RT-PCR-confirmed SARS-CoV-2 infection and an interpretable iodine map were included. Patients with perfusion anomalies on sCTA in morphologically normal lung parenchyma showed lower Pa/Fi values (294 ± 111.3 vs. 397 ± 37.7, p = 0.035), and higher D-dimer levels (1156 ± 1018 vs. 378 ± 60.2, p < 0.01). The main common patterns seen in lung CT scans were ground-glass opacities, mixed pattern with predominant ground-glass opacities and mixed pattern with predominant consolidation in 56.1%, 24.4% and 19.5% respectively. Perfusion abnormalities were common (36 patients, 87.8%), mainly hypoperfusion in areas of apparently healthy lung. Patients with severe hypoperfusion in areas of apparently healthy lung parenchyma had an increased probability of being admitted to ICU and to initiate IMV (HR of 11.9 (95% CI 1.55-91.9) and HR 7.8 (95% CI 1.05-61.1), respectively). CONCLUSION: Perfusion abnormalities evidenced in iodine maps obtained by sCTA are associated with increased admission to ICU and initiation of IMV in COVID-19 patients.

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This paper is about the Guideline for Ventilation / Perfusion Scintigraphy. It has been developed by the Brazilian Society of Nuclear Medicine to be a best practices guide used in Nuclear Medicine. Its function is to be an educational tool to help the Nuclear Medicine Services in Brazil to guarantee a quality care to the patients

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The accurate diagnosis of pulmonary thromboembolism is essential to reducing the morbidity and mortality associated with the disease. The diagnosis of pulmonary thromboembolism is challenging because of the nonspecific nature of the clinical profile and the risk factors. Imaging methods provide the definitive diagnosis. Currently, the imaging method most commonly used in the evaluation of pulmonary thromboembolism is computed tomography. The recent development of dual-energy computed tomography has provided a promising tool for the evaluation of pulmonary perfusion through iodine mapping. In this article, we will review the importance of diagnosing pulmonary thromboembolism, as well as the imaging methods employed, primarily dual-energy computed tomography.

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Abstract The accurate diagnosis of pulmonary thromboembolism is essential to reducing the morbidity and mortality associated with the disease. The diagnosis of pulmonary thromboembolism is challenging because of the nonspecific nature of the clinical profile and the risk factors. Imaging methods provide the definitive diagnosis. Currently, the imaging method most commonly used in the evaluation of pulmonary thromboembolism is computed tomography. The recent development of dual-energy computed tomography has provided a promising tool for the evaluation of pulmonary perfusion through iodine mapping. In this article, we will review the importance of diagnosing pulmonary thromboembolism, as well as the imaging methods employed, primarily dual-energy computed tomography.

Resumo A acurácia no diagnóstico de tromboembolismo pulmonar é essencial para reduzir a morbimortalidade causada por esta enfermidade. Devido ao quadro clínico e fatores de risco inespecíficos, o diagnóstico de tromboembolismo pulmonar torna-se um desafio. Os métodos de imagem fornecem o diagnóstico definitivo, sendo a tomografia computadorizada o método mais utilizado atualmente. Nos últimos anos, houve o desenvolvimento da tomografia computadorizada com dupla energia e essa ferramenta tem se mostrado promissora para avaliação da perfusão pulmonar por meio do mapa de iodo. Neste artigo é feita revisão acerca da importância do diagnóstico de tromboembolismo pulmonar, bem como os métodos de imagem disponíveis, com ênfase na tomografia computadorizada com dupla energia.

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INTRODUÇÃO E OBJETIVOS: A Circulação extracorpórea (CEC) é associada a ativação leucocitária, resposta inflamatória e disfunção pulmonar. Objetivou-se avaliar os efeitos da filtragem leucocitária sobre a resposta inflamatória e a função pulmonar em indivíduos submetidos à revascularização do miocárdio (RM) com CEC. MÉTODO: Após aprovação pelo Comitê de Ética Institucional e obtenção do consentimento informado dos indivíduos, foi realizado estudo prospectivo randomizado, para comparar indivíduos adultos submetidos à RM com CEC, utilizando-se filtragem leucocitária (n=09) ou filtro standard (n=11) durante a CEC. Tomografia computadorizada (CT) de tórax, espirometria, análise da oxigenação e hemograma foram realizados antes da cirurgia. A anestesia foi induzida por via venosa com etomidato (0,3 mg.kg-1), sufentanil (0,3 ug.kg-1), pancurônio (0,08 mg.kg-1) e mantida com isoflurano (0,5 - 1,0 CAM) e sufentanil (0,5 ug.kg-1.h-1). A ventilação mecânica utilizou volume corrente de 8 mL.kg-1, com FiO2 de 0,6 e PEEP de 5 cm H2O, exceto durante a CEC. No grupo Filtragem, durante a CEC, foi inserido um filtro de leucócitos na linha arterial do circuito (LG-6, Pall Biomedical Products) e, no grupo Controle, foi utilizado o filtro Standard. Contagem leucocitária foi realizada após a indução, aos 5, 25 e 50 min de CEC, ao final da cirurgia, com 12 e 24 h PO. Dados hemodinâmicos, PaO2/FiO2, fração de Shunt, interleucinas, elastase e mieloperoxidase foram colhidos antes e após a CEC, no final da cirurgia, com 6,12 e 24 h PO. Trinta minutos depois da indução, e trinta após a CEC, três amostras sequenciais de ar exalado foram colhidas para análise de óxido nítrico (NO), por quimiluminescência. Espirometria e CT de tórax foram realizadas no primeiro dia pós-operatório. Os dados foram analisados por meio de ANOVA de duplo fator para medidas repetidas. RESULTADOS: O tempo de CEC foi similar entre os grupos controle e filtragem (86,78 ± 19,58 versus 104,64 ± 27,76 min, p=0,161)...

BACKGROUND AND OBJECTIVE: The Cardiopulmonary bypass (CPB) is related to leukocyte activation, inflammatory response and lung dysfunction. The aim of this study was to evaluate the effects of CPB-leukocyte filtration on the inflammatory response and lung function after coronary artery bypass grafting (CABG). METHODS: After approval by the institutional ethics committee and informed consent, a prospective randomized study was performed to compare CABG-patients undergoing CPB-leukocyte filtration (n=9) or standard CPB (n=11). Espirometry, chest computed tomography (CT), oxygenation analysis and leukocyte count were performed before surgery. Anesthesia induction was performed intravenously with etomidate (0,3 mg.kg-1), sufentanil (0,3 ug.kg-1), pancuronium bromide (0,08 mg.kg-1) e sustained with isoflurano (0,5 - 1,0 CAM) and sufentanil (0,5 ug.kg-1.h-1). The tidal volume used during mechanical ventilation was 8 mL.kg-1, the FiO2 0.6 and PEEP 5 cm H2O, except during CPB. In Filtered group, during CPB, was inserted a leukocyte filter in the arterial line of CPB circuit (LG-6, Pall Biomedical Products) and, in Control group, the Standard arterial line filter was utilized. Hemodynamic data, PaO2/FiO2, shunt fraction, interleukins, elastase and myeloperoxidase were evaluated before and after CPB, at the end of surgery, and 6, 12 and 24 h PO. Thirty minutes after induction, and Thirty after CPB, three sequential exhaled air samples were collected to perform analysis of nitric oxide (NO), by chemiluminescence technique. Espirometry and chest CT were performed on first PO. Data were analyzed using two-factor ANOVA for repeated measurements. RESULTS: Length of CPB was similar in the filtered and control groups (86.78 ± 19.58 versus 104.64 ± 27.76 min, p = 0.161). The filtered group showed lower neutrophil counts than the control group up to 50 minutes of CPB (3384 ± 2025 versus 6478 ± 3582 U/mm-3, p = 0.036), lower shunt fraction up to 6 hours after surgery (10 ± 2%)...

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O presente estudo teve por objetivo investigar a estabilidade do ponto ótimo cardiorrespiratório (POC) em dois testes cardiopulmonares de exercício máximos (TCPEs), realizados em cicloergômetro de membros inferiores. Para tanto, foram analisados retrospectivamente os dados de 1334 indivíduos avaliados por no mínimo duas vezes entre 1995 e 2013, sendo identificados, a partir de rígidos critérios de inclusão, 222 pacientes (159 homens) com a idade de 55±11,6 anos. Logo, foram verificados os dados do POC obtidos a partir da análise da ventilação e do consumo de oxigênio em cada minuto do TCPE, o VO2 máximo, e as curvas de eficiência do consumo de oxigênio (OUES) e do equivalente ventilatório de dióxido de carbono (VE/VCO2 slope), sendo a estabilidade avaliada pelos coeficientes de correlação intraclasse. A mediana do intervalo de tempo entre os dois TCPEs foi de 1,6 anos. Os valores de cada uma das variáveis obtidas nos dois TCPEs apresentaram altas e significativas associações (p <0,01), sendo: VO2max ri = 0,93 (IC95% = 0,91 a 0,94); POC ri = 0,87; (IC95% = 0,82 a 0,90); OUES ri = 0,90 (IC95% = 0,87 a 0,93) e VE/VCO2 slope ri = 0,74 (IC95% = 0,67 a 0,80). Concluímos que, em condições controladas, o POC é um índice ventilatório bastante estável em TCPEs realizadas em indivíduos adultos, com níveis de estabilidade similar ou superior de outras variáveis ou índices consagrados na literatura, corroborando, dessa forma, seu potencial de utilização em pesquisas fisiológicas e na prática clínica.

The present study aimed to assess the stability of the cardiorespiratory optimum point (COP) in two maximum cardiopulmonary exercise testing (CPET), performed in a lower limbs cycling ergometer. Therefore, we retrospectively analyzed data from 1334 subjects that were evaluated by at least twice between 1995 and 2013, and identified after rigid inclusion criteria, 222 subjects (159 men) aged 55 ± 11.6 years. COP results were obtained from the ventilation and oxygen consumption data averaged at each minute during CPET as well as maximum oxygen uptake, efficiency curves of oxygen consumption (OUES) and ventilatory equivalent for carbon dioxide (VE/VCO2 slope), and their stability assessed by intraclass correlation coefficients. The median time interval between two CPETs was 1.6 years. The values of the variables obtained in the two CPETs showed high and significant associations (p <0.01), being: VO2max ri = 0.93 (CI95% = 0.91 a 0.94); COP ri = 0.87; (CI95% = 0.82 a 0.90); OUES ri = 0.90 (CI95% = 0.87 a 0.93) and VE/VCO2 slope ri = 0.74 (CI95% = 0.67 a 0.80). We conclude that, under controlled conditions, COP is a very stable ventilatory index in CPET performed in adults, with stability levels similar or higher than other variables well-established in the literature, confirming thus its potential for use in physiological research and clinical practice.

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FUNDAMENTO: No Teste Cardiopulmonar de Exercício (TCPE) máximo são analisadas diversas variáveis ventilatórias, incluindo o equivalente ventilatório de oxigênio (VE/VO2). O valor mínimo do VE/VO2 reflete a melhor integração entre os sistemas respiratório e cardiovascular, podendo ser denominado Ponto Ótimo Cardiorrespiratório (POC). OBJETIVO: Determinar o comportamento do POC em função do gênero e da idade em adultos saudáveis e verificar a associação com outras variáveis do TCPE. MÉTODOS: De 2.237 indivíduos, foram selecionados 624 (62% homens e 48 ± 12 anos de idade), não atletas, saudáveis, submetidos ao TCPE máximo. O POC ou VE/VO2 mínimo foi obtido a partir da análise da ventilação e do consumo de oxigênio em cada minuto do TCPE. Foi verificada a relação entre idade e POC para os dois gêneros, assim como as associações com: VO2máx, VO2 no limiar anaeróbico (VO2LA), eficiência da inclinação de consumo de oxigênio (OUES) e com VE máxima. Comparou-se ainda a intensidade do esforço (MET) no POC, LA e VO2máx. RESULTADOS: O POC aumenta com a idade, sendo 23,2 ± 4,48 e 25,0 ± 5,14, respectivamente, em homens e mulheres (p < 0,001). Há associações moderadas e inversas com VO2máx (r = -0,47; p < 0,001), com VO2LA (r = -0,42; p < 0,001) e com o OUES (r = -0,34; p < 0,001). O POC ocorreu, em média, a (44% do VO2máx) e antes do LA (67% do VO2máx) (p < 0,001). CONCLUSÃO: POC, uma variável submáxima, aumenta com a idade e é discretamente mais alto em mulheres. Sendo modestamente associado a outras medidas ventilatórias, parece haver uma contribuição independente na interpretação da resposta cardiorrespiratória ao TCPE.

BACKGROUND: At the maximal Cardiopulmonary Exercise Testing (CPET), several ventilatory variables are analyzed, including the ventilatory equivalent for oxygen (VE/VO2). The minimum VE/VO2 value reflects the best integration between the respiratory and cardiovascular systems and may be called "Cardiorespiratory Optimal Point (COP)". OBJECTIVE: To determine the behavior of the COP according to gender and age in healthy adults and verify its association with other CPET variables. METHODS: Of 2,237 individuals, 624 were selected (62% men and 48 ± 12 years), non- athletes, healthy, who were submitted to maximal CPET. COP or minimum VE/VO2 was obtained from the analysis of ventilation and oxygen consumption in every minute of CPET. We investigated the association between age and COP for both genders, as well as associations with: VO2max, VO2 at anaerobic threshold (VO2AT), oxygen uptake efficiency slope (OUES) and with maximum VE. We also compared the intensity of exertion (MET) at the COP, AT and VO2max. RESULTS: COP increases with age, being 23.2 ± 4.48 and 25.0 ± 5.14, respectively, in men and women = (p < 0.001). There are moderate and inverse associations with VO2max (r = -0.47; p < 0.001), with VO2AT (r = -0.42; p < 0.001) and with OUES (r = -0.34; p < 0.001). COP occurred, on average, at 44% do VO2max and before AT (67% of VO2max) (p < 0.001). CONCLUSION: COP, a submaximal variable, increases with age and is slightly higher in women. Being modestly associated with other ventilation measures, there seems to be an independent contribution to the interpretation of the cardiorespiratory response to CPET.

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Aging generates four important changes in the structure and function of the respiratory system. There is a reduction in the elastic recoil of the lung causing "senile emphysema", a condition characterized by reduction in the alveolar surface area without alveolar destruction, which is associated with hyperinflation, increased lung compliance and reduction in alveolar-capillary diffusing capacity. There is a decrease in the compliance of the chest watt, due to calcification of its articulations, dorsal kyphosis and "barrel chest". There is a decrease in the strength of respiratory muscles which correlates with cardiac Index, nutritional status and hyperinflation, and there is a reduction in the ventilatory response to hypoxia and hypercapnia as well as in the perception of increased airway resistance. The increased static lung compliance combined with the decreased chest watt compliance leads to an increase in the functional residual capacity with aging. On the other hand, the loss of alveolar and airways elastic recoil combined with the reduction in the strength of the expiratory muscles, leads to an increase in residual volume and decreased maximal expiratory airflow rates and vital capacity. Despite these changes, the respiratory system maintains an adequate gas exchange at rest and during exercise during the whole life span, showing a normal PaCO2 and a slight decline in PaO2 (-0,3 mmHg per year) which is attenuated to become almost undetectable over the age of 70.

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