Resumo Fundamento O exame físico permite a avaliação prognóstica de pacientes com insuficiência cardíaca (IC) descompensada, porém não é suficientemente confiável e depende da experiência clínica do profissional. Considerando as respostas hemodinâmicas a situações do tipo “luta ou fuga” tais como a admissão no serviço de emergência, foi proposto o índice hemodinâmico agudo (IHA), calculado a partir da frequência cardíaca e pressão de pulso. Objetivo avaliar a capacidade prognóstica intra-hospitalar do IHA na IC descompensada. Métodos estudo prospectivo, multicêntrico e observacional baseado no registro BREATHE, incluindo dados de hospitais públicos e privados no Brasil. Foram utilizadas análises ROC (Receiver Operating Characteristic), de estatística c e de regressão multivariada, assim como o critério de informação de Akaike, para testar a capacidade prognóstica do IHA. O valor-p < 0,05 foi considerado estatisticamente significativo. Resultados Foram analisados dados de 463 pacientes com IC com fração de ejeção reduzida a partir do registro BREATHE. A mortalidade intra-hospitalar foi de 9%. A mediana do IHA foi considerada o valor de corte (4 mmHg⋅bpm). Um baixo IHA (≤ 4 mmHg⋅bpm) foi encontrado em 80% dos pacientes falecidos. O risco de mortalidade intra-hospitalar em pacientes com baixo IHA foi 2,5 vezes maior que aquele para pacientes com IHA > 4 mmHg⋅bpm. O IHA foi capaz de predizer independentemente a mortalidade intra-hospitalar na IC aguda descompensada [sensibilidade: 0,786; especificidade: 0,429; AUC (área sob a curva): 0,607 (0,540-0,674), p = 0,010] mesmo depois dos ajustes para comorbidades e uso de medicamentos [razão de chances (RC): 0,061 (0,007-0,114), p = 0,025]. Conclusões O IHA é capaz de predizer independentemente a mortalidade intra-hospitalar na IC aguda descompensada. Esse índice simples e realizado à beira do leito pode se mostrar útil em serviços de emergência. (Arq Bras Cardiol. 2021; 116(1):77-86)

Abstract Background The physical examination enables prognostic evaluation of patients with decompensated heart failure (HF), but lacks reliability and relies on the professional’s clinical experience. Considering hemodynamic responses to “fight or flight” situations, such as the moment of admission to the emergency room, we proposed the calculation of the acute hemodynamic index (AHI) from values of heart rate and pulse pressure. Objective To evaluate the in-hospital prognostic ability of AHI in decompensated HF. Methods A prospective, multicenter, registry-based observational study including data from the BREATHE registry, with information from public and private hospitals in Brazil. The prognostic ability of the AHI was tested by receiver-operating characteristic (ROC) analyses, C-statistics, Akaike’s information criteria, and multivariate regression analyses. p-values < 0.05 were considered statistically significant. Results We analyzed data from 463 patients with heart failure with low ejection fraction. In-hospital mortality was 9%. The median AHI value was used as cut-off (4 mmHg⋅bpm). A low AHI (≤ 4 mmHg⋅bpm) was found in 80% of deceased patients. The risk of in-hospital mortality in patients with low AHI was 2.5 times that in patients with AHI > 4 mmHg⋅bpm. AHI independently predicted in-hospital mortality in acute decompensated HF (sensitivity: 0.786; specificity: 0.429; AUC: 0.607 [0.540–0.674]; p = 0.010) even after adjusting for comorbidities and medication use [OR: 0.061 (0.007–0.114); p = 0.025). Conclusions The AHI independently predicts in-hospital mortality in acute decompensated HF. This simple bed-side index could be useful in an emergency setting. (Arq Bras Cardiol. 2021; 116(1):77-86)

ABSTRACT The Darcy-Weisbach equation is the most recommended equation for determining the pressure loss in pressurized pipes because of its wide applicability. However, one of the largest obstacles to implementing this equation is the friction factor (f) calculation. This factor can be precisely determined using the Colebrook equation, which is implicit. Thus, the objective of this study was to compare six explicit equations for calculating the Darcy-Weisbach friction factor with the implicit Colebrook equation based on the relative error. Based on the results, the equations of Vatankhah and Offor & Alabi were the most highly recommended. These six explicit formulas showed a mean relative error of less than ± 1% compared to the Colebrook equation, except for the Swamee and Jain equation, for which the laminar regime generated a mean relative error of 1.83%.

OBJECTIVE: This study aimed to compare respiratory responses, focusing on the time-domain variability of ventilatory components during progressive cardiopulmonary exercise tests performed on cycle or arm ergometers. METHODS: The cardiopulmonary exercise tests were conducted on twelve healthy volunteers on either a cycle ergometer or an arm ergometer following a ramp protocol. The time-domain variabilities (the standard deviations and root mean squares of the successive differences) of the minute ventilation, tidal volume and respiratory rate were calculated and normalized to the number of breaths. RESULTS: There were no significant differences in the timing of breathing throughout the exercise when the cycle and arm ergometer measurements were compared. However, the arm exercise time-domain variabilities for the minute ventilation, tidal volume and respiratory rate were significantly greater than the equivalent values obtained during leg exercise. CONCLUSION: Although the type of exercise does not influence the timing of breathing when dynamic arm and leg exercises are compared, it does influence time-domain ventilatory variability of young, healthy individuals. The mechanisms that influence ventilatory variability during exercise remain to be studied.

INTRODUCTION: There are no available data addressing the potential clinical risks of open-water swimming competitions. OBJECTIVE: Address the risks of hypothermia and hypoglycemia during a 10-km open-water swimming competition in order to alert physicians to the potential dangers of this recently-introduced Olympic event. METHODS: This was an observational cross-sectional study, conducted during a 10-km open-water event (water temperature 21ºC). The highest ranked elite open-water swimmers in Brazil (7 men, 5 women; ages 21±7 years old) were submitted to anthropometrical measurements on the day before competition. All but one athlete took maltodextrine ad libitum during the competition. Core temperature and capillary glycemia data were obtained before and immediately after the race. RESULTS: Most athletes (83%) finished the race with mild to moderate hypothermia (core temperature <35ºC). The body temperature drop was more pronounced in female athletes (4.2±0.7ºC vs. male: 2.7±0.8ºC; p=0.040). When data from the athlete who did not take maltodextrine was excluded, capillary glycemia increased among athletes (pre 86.6±8.9 mg/dL; post 105.5±26.9 mg/dL; p=0.014). Time to complete the race was inversely related to pre- competition body temperature in men (r=-0.802; p=0.030), while it was inversely correlated with the change in capillary glycemia in women (r=-0.898; p=0.038). CONCLUSION: Hypothermia may occur during open-water swimming events even in elite athletes competing in relatively warm water. Thus, core temperature must be a chief concern of any physician during an open-water swim event. Capillary glycemia may have positive effects on performance. Further studies that include more athletes in a controlled setting are warranted.