Study of blood flow velocity and respiratory variability in different parts of left heart by ultrasonography

Abstract

Objective To investigate the correlation between blood flow velocity and respiratory variability in different parts of left heart of patients with sepsis via measuring the flow velocity of the E-wave of mitral valve (MV), peak flow velocity of left ventricular outflow tract (LVOT), and respiratory variability (ΔVpeak) by ultrasonography. Methods Totally 81 patients with sepsis hospitalized in ICU were chosen consecutively from March 2017 to October 2017. Each patient’s flow velocity of the E-wave of mitral valve and peak flow velocity of LVOT was inspected, by apical four-chamber view and apical five-chamber view respectively, to calculate the respiratory variability. Results (1) Of the 81 patients with sepsis, 33 patients (40.7%) had complete control of mechanical ventilation (no spontaneous breathing trigger), and 48 patients (59.3%) had spontaneous breathing and incomplete control of mechanical ventilation (partial spontaneous breathing trigger). (2) There was no significant difference in the mean values of flow velocity of the E-wave of mitral valve and peak flow velocity of LVOT in patients with sepsis. Whereas the flow velocity of the E-wave of mitral valve (0.15±0.05) was greater than the peak flow velocity of LVOT (0.12±0.04) with statistical significance (P<0.01). In sepsis patients with complete control of mechanical ventilation (no spontaneous breathing trigger), respiratory variability in the flow velocity of the E-wave of mitral valve (0.17±0.06) was significantly greater than the peak flow velocity of LVOT (0.11±0.03), P<0.01, whereas in sepsis patients with incomplete control of mechanical ventilation (partial spontaneous breathing trigger), there was no statistically significant difference between the respiratory variability in flow velocity of the E-wave of mitral valve (0.14±0.04) and in the peak flow velocity of LVOT (0.13±0.03), P=0.102. (3) The respiratory variability in flow velocity of the E-wave of mitral valve was correlated with the peak flow velocity of LVOT (r=0.670, P<0.01). The flow velocity of the E-wave of mitral valve was all correlated with the peak flow velocity of LVOT in both sepsis patients with complete control of mechanical ventilation (no spontaneous breathing trigger) (r=0.894, P<0.01), and sepsis patients with incomplete control of mechanical ventilation (partial spontaneous breathing trigger) (r=0.774, P<0.01), respectively. Conclusions The respiratory variability in flow velocity of the E-wave of mitral valve was correlated with that in the peak flow velocity of LVOT, which may provide a new indicator in evaluating the fluid responsiveness of patients with sepsis. Key words: Ultrasonography; Mitral valve; Left ventricular outflow tract; Respiratory variability; Fluid responsiveness