Relação da eficiência ventilatória e da função pulmonar de repouso com a capacidade funcional de indivíduos com insuficiência cardíaca

Abstract

The injury of cardiac function, characterized by reduced cardiac output, is considered an important determinant of exercise intolerance, ventilatory inefficiency and dyspnea in patients with heart failure (HF). The gold standard tool to evaluate the functional state and ventilatory damage in patients with HF is the cardiopulmonary exercise test (CPET). The functional state is also evaluated by ergometric test, submaximal effort tests or estimated by questionnaires, especially when is impossible to apply the CPET. However, the evaluation of ventilatory damage is not frequently achieved if the CPET is not available. To identify possible instruments that may contribute to this evaluation, the purposes of this study were: 1) to identify the association of ventilatory variables from CPET with maximal functional capacity to select the best suggestive variables of relation with exercise capacity, 2) to evaluate the relation between variables gotten by different methods of functional capacity (maximal and submaximal), estimated performance and ventilatory capacity (pulmonary function, including the inspiratory muscular strength, and efficiency during exercise) in patients with HF, and compare to healthy subjects and 3) from previous objective, identify other instruments and measures that present good relation with ventilatory variables from gold standard method. Twenty eight patients with HF classes I to III of New York Heart Association (heart failure group - GHF) and 28 healthy subjects (control group - GC), age 44.93±9.69 and 40.18±10.78 years, respectively, did a CPET in an electronic treadmill with ramp protocol (maximal test) and a six minute walk test (submaximal test). In a pilot study, 15 of these participants (8 GHF e 7 GC) were also submitted to a spirometry test, a digital manovacuometry and answered the Duke Activity Status Index questionnaire. Comparing the groups, the Students t-test or Mann Whitney test were used. Correlations of Pearson or Spearman were performed. Significant level was set at p<0.05. The Ethics Committee of Research of UFMG (Appear CAAE14833213.3.0000.5149) approved this study. Statistics differences in values of maximal and submaximal functional capacity, ventilatory efficiency indices, cardiac function and maximal inspiratory pressure were observed between GIC and GC (p<0.001). As expected, worse indices of maximal and submaximal functional capacity and ventilatory efficiency were observed in GIC subjects (p<0.001). Correlations between maximal functional capacity and oxygen uptake efficiency slope (VE/VCO2) (r=-0.48; p=0.009), oxygen uptake efficiency slope (OUES) (r=0.83; p<0.0001), oxygen pulse (VO2/FC) (r=0.60; p=0.001) and end-tidal carbon dioxide partial pressure (PETCO2) (r=0.42; p=0.026) were found in patients with HF. Correlations between submaximal functional capacity and VE/VCO2 (r=-0.48; p=0.010), OUES (r=0.46; p=0.015) and PETCO2 (r=0.43; p=0.022) were also observed in this group of patients. Smaller values of maximal inspiratory pressure (MIP) were observed in GIC (p<0.0001). Although there was no statistic significance (p=0.067), smaller values of pulmonary function were also observed in GIC. Correlations between spirometric variables (forced vital capacity - FVC and forced expiratory volume in 1 second - FEV1) and the maximal capacity (r=0.76; p=0.029 and r=0.83; p=0.010, respectively); MIP and submaximal capacity (r=0.87; p=0.005); VE/VCO2 and PETCO2 with estimated performance (r=-0.95; p<0.0001 and r=0.90; p=0.002, respectively) were observed in subjects with HF. A high magnitude correlation between the variables FVC, FEV1 and MIP with VE/VCO2 (r=-0.71; p=0.047; r=-0.71; p=0.047 and r=-0.74; p=0.035, respectively), and between FEV1 and OUES (r=0.74; p=0.036) were found in the GIC subgroup. In the subgroup of healthy subjects, good relation of spirometric variables (FVC and FEV1) with OUES (r=0.89; p=0.007 and r=0.87; p=0.011, respectively) and VO2/FC (r=0.96; p=0.001 and r=0.76; p=0.047, respectivamente respectively) was observed. No association was observed between PETCO2 index and rest ventilatory variables. Together, these data suggest that the association of submaximal capacity, estimated performance and pulmonary function (including the inspiratory muscular strength) is a possibility to optimize the screen, diagnosis and treatment of ventilatory damage in patients with HF, mainly when the cardiopulmonary exercise test is not available.