[Ultrasound study for quantitative assessment of diaphragm dysfunction in patients with sepsis]

Objective: To systematically assess diaphragm dysfunction in patients with sepsis. Based on previous findings that diaphragm excursion and diaphragm thickening fraction (DTF) significantly decrease in septic patients, this study further analyzed the diaphragm contraction velocity and excursion-time index (E-T index) in relation to diaphragm contraction time. Methods: A total of 59 patients with pneumonia-induced sepsis from Shengjing Hospital of China Medical University were recruited (sepsis group). Healthy individuals undergoing routine health check-ups during the same period were recruited as the control group, matched for age and sex (1∶1). General baseline data were collected, and bedside ultrasound was used to measure diaphragm thickness, DTF, diaphragm excursion, inspiratory time, diaphragm E-T index, and per-minute E-T index (calculated as the quiet breathing diaphragm E-T index multiplied by the respiratory rate). Correlation analyses were performed between diaphragm ultrasound indicators and the Sequential Organ Failure Assessment (SOFA) score. SPSS 21.0 was used for statistical analysis. Results: (1) There was no statistically significant difference in diaphragm thickness between the sepsis group and the control group (end of quiet expiratory: (2.06±0.35)mm vs. (1.96±0.37)mm, t=-1.516, P>0.05; end of maximum inspiratory: 3.18(2.86, 3.61)mm vs. 3.04(2.73, 3.27)mm, Z=-1.688, P>0.05), while DTF was significantly lower in the sepsis group compared to the control group (0.49±0.17 vs. 0.65±0.17, t=5.360, P<0.05). (2) In both quiet breathing and deep breathing states, diaphragm excursion was lower in the sepsis group than in the control group (quiet breathing: t=-4.187, P<0.05; deep breathing: t=-11.720, P<0.05), and inspiratory time was shorter in the sepsis group (quiet breathing: t=-7.410, P<0.05; deep breathing: t=-6.348, P<0.05). (3) In the quiet breathing state, the diaphragm contraction velocity in the sepsis group was faster than in the control group (Z=2.330, P<0.05), while in the deep breathing state, the diaphragm contraction velocity in the sepsis group was lower than in the control group (Z=-3.383, P<0.05). (4) In the quiet breathing state, the diaphragm E-T index was lower in the sepsis group than in the control group (Z=-5.762, P<0.05); however, the per-minute E-T index compensated to normal by increasing the respiratory rate. In the deep breathing state, the diaphragm E-T index, which had the highest correlation with the SOFA score (r=-0.882, P<0.05), was lower in the sepsis group than in the control group (Z=-7.974, P<0.05). Conclusions: Bedside ultrasound can systematically quantify diaphragm contraction dysfunction in patients with sepsis. In the quiet breathing state, septic patients exhibit a pattern of shallow and rapid breathing, allowing the body to compensate for oxygen demand. In the deep breathing state, the intrinsic contraction efficiency and functional capacity of the diaphragm in septic patients decreases and the diaphragm is unable to meet the body's oxygen requirements due to decompensation.