The evaluation of diaphragmatic morphology and function in septic patients by bedside ultrasound

Objective To evaluate the changes of the diaphragmatic morphology and function in septic patients by bedside ultrasound. Methods A cross-sectional study was conducted in the Department of Pulmonary and Critical Care Medicine, Shengjing Hospital of China Medical University over a 6-month period from September 2018 to February 2019. Thirty-one septic patients who were diagnosed within the past 7 days with Sequential Organ Failure Assessment (SOFA) scores less than or equal to 5 points were enrolled in the septic group. Thirty-eight healthy subjects who underwent regular physical examinations during the same period were enrolled randomly in the control group. All subjects′ clinical data, diaphragmatic morphology parameters (thickness at the end of quiet expiration, thickness at the end of deep inspiration) and function parameters (thickening fraction, quiet breath excursion and deep breath excursion) measured with bedside ultrasound were compared. The comparison of continuous variables was performed by using the Student t-test or Mann-Whitney U test. Chi-square test was performed for categorical variables. A value of P less than 0.05 was considered statistically significant. Results (1) There was no statistical difference in gender, age, body mass index, underlying diseases and mean arterial pressure between the septic group and the control group (all P>0.05). (2) Diaphragmatic morphology parameters: There was no statistical difference between the septic group and the control group in the thickness at the end of quiet expiration [septic group: 0.21 (0.18-0.23) cm; control group: 0.19(0.16-0.20) cm, Z=-1.739, P=0.082] or in the thickness at the end of deep inspiration [septic group: (0.27±0.84) cm; control group: (0.29±0.77) cm, t=1.344, P=0.183]. (3) Diaphragmatic function parameters: The thickening fraction in the septic group was significantly less than that in the control group [septic group: 24% (16%-56%); control group:61% (37%-82%), Z=-3.076, P=0.002]. The quiet breath excursion in the septic group was significantly less than that in the control group [septic group: (1.25±0.38) cm; control group: (1.65±0.82) cm, t=2.687, P=0.009]. The deep breath excursion in the septic group was also significantly less than that in the control group [septic group: 2.79 (1.80-4.16)cm; control group:3.77(2.92-5.05)cm, Z=-2.231, P=0.026]. Conclusion In septic (SOFA scores≤5 points) patients, diaphragmatic dysfunction occurred without significant morphology change in the first 7 days. Diaphragmatic dysfunction occurred before atrophy. Bedside ultrasound is a useful clinical tool in diaphragmatic morphology and function evaluation. Key words: Sepsis; Bedside ultrasound; Diaphragm