Cinemática ventilatória e padrão respiratório durante exercício com limiar de carga inspiratória em indivíduos com insuficiência cardíaca

Abstract

Introduction: Inspiratory muscle training through exercise with inspiratory threshold loading is used in rehabilitation of patients with heart failure (HF). Although studies have reported this exercise associated with diaphragmatic breathing (DB), it is necessary to identify whether this association is advantageous in regard to ventilation. Objectives: To characterize chest wall kinematics and breathing pattern of patients with HF, to evaluate ventilatory responses during inspiratory exercise with or without association of DB and to compare them with healthy subjects. Methods: There were included patients with systolic HF (HF group HFG, left ventricular ejection fraction - LVEF 45%, functional classes I, II or III by New York Heart Association, aged 30-59 years) and subjects without heart diseases (healthy controls HC) matched by age. Chest wall kinematics and breathing pattern variables were obtained by optoelectronic plethysmography (BTS bioengineering, Milan, Italy) in the conditions of quite breathing (QB), inspiratory exercise (IE) and inspiratory exercise associated with diaphragmatic breathing (IE+DB). Inspiratory load was set in 30% of maximal inspiratory pressure (MIP) measured for each participant. Mixed factorial ANOVA split-plot design for repeated measures was used to compare variables within each group and unpaired student T test compared variables between groups. Statistical differences with a p value <.05 were considered significant. Results: Thirteen patients in HFG (LVFE: 33.46±9.36%; age 50.54±7.63 years) and 13 in HC (age 45.69±6.79 years) were evaluated. HFG showed lower values of forced vital capacity (FVC 3.43±0.80 vs 4.21±0.66 L; p=0.012), forced expiratory volume in one second (FEV1 - 2.70±0.63 vs 3.36±0.52 L; p=0.008) and MIP 65.77±28.13 vs 109.62±16.13 cmH2O; p<0.0001). During QB was found lower rib cage contribution - VRC% and higher abdomen contribution -VAB% in HFG than in HC (p=0.028). Same results were found during IE (p=0.006). Association of DB produced chest wall changes only in HC, with increase of VAB% (p=0.008) and decrease of VRC% (p<0.0001). Both groups showed increases in tidal volume (VT) and inspiratory time (Ti) during exercise conditions in relation to QB (p<0.05), whereas duty cycle (Ti/Ttot) was higher in HFG during IE (p=0.042). Conclusion: Patients with HF present lower rib cage motion than healthy controls during quiet breathing. Inspiratory exercise does not change chest wall kinematics in these patients, independently of the association with DB. This can be related to lung restrictions and accessory inspiratory muscle weakness, which impaired the movement of rib cage