| Objective:To study the two-dimensional speckle-tracking applied to analyze the peak diaphragmatic contraction strain under different inspiratory loads in normal subjects and explore the application of the two-dimensional speckle-tracking in assessing diaphragmatic contractile function.The clinical feasibility and validity of the speckle-tracking for the analysis of diaphragmatic contractile function is further evaluated by analyzing the peak bilateral diaphragmatic contraction strain in patients with supratentorial ischemic stroke with hemiparesis and comparing the diaphragmatic strain values on the hemiplegic sides with the non-hemiplegic sides.Materials and methods:1.For the normal subjectsFifty-two healthy volunteers were submitted to a longitudinal strain study using two-dimensional ultrasound speckle-tracking with linear array transducer at states of quiet breathing(QB),60%maximal inspiratory capacity(60%IC),and 80%maximal inspiratory capacity(80%IC).Diaphragmatic excursion(DE)and thickness fraction(TF)also were measured during QB and maximal IC by phased array transducer and linear array transducer respectively.We compared the longitudinal strain values of the bilateral hemidiaphragms at the three breathing states and analyzed their correlation with gender,age,DE and TF.10 subjects were randomly selected to perform intra-and interobserver agreement tests.2.For hemiplegic stroke patientsTwenty-five supratentorial ischemic stroke patients with hemiparesis were recruited for the study.Peak diaphragmatic strain,DE and TF were measured and compared between the hemiplegic side and the healthy side during QB and forced breathing(FB)within 72 hours of stroke onset,and clinical data such as muscle strength on the hemiplegic side and the National Institute of Health stroke scale(NIHSS)were collected,The correlation between the strain values of the diaphragm on the hemiplegic side and the relevant clinical data was analyzed.Results:1.Results of diaphragm function in normal subjectsThe median diaphragmatic strain value during QB and 60%IC is-14.5(7.3)%and-45.5(12.8)%respectively.The mean diaphragmatic strain during 80%IC is-62.0±13.2%.Diaphragmatic strain has significant differences at the three states(χ2(2)=195.504,P<0.001),and the pairwise comparison also suggested that the differences are statistically significant(all P<0.001).Longitudinal strain at 80%IC was moderately correlated with TF at maximal IC(R=-0.683,P<0.001),and weakly correlated with DE at maximal IC(R=0.336,P=0.004).Intra-and inter-operator reliability(P<0.001)was good for speckle-tracking.2.Results of diaphragm function in hemiplegic stroke patientsSignificant differences in the strain values of QB(P=0.001)and FB(P<0.001)were observed between hemiplegic sides and normal sides.Diaphragm strain values were no significant differences between the left-hemiplegic sides and right-hemiplegic sides during QB and FB(all P>0.05).There were no significant differences about TF and DE between hemiplegic sides and normal sides in the QB(P>0.05),while the hemiplegic sides had significantly lower TF and DE than the normal sides under the FB(P<0.05).Conclusion:1.The ultrasound two-dimensional speckle-tracking helps to assess bilateral diaphragmatic contractile function under different inspiratory loads and compensates for the inadequacy of conventional two-dimensional ultrasound measurements(diaphragmatic excursion and thickness fraction).Moreover,diaphragmatic strain values were also correlated with conventional ultrasound diaphragmatic measurements.2.Diaphragmatic strain values were significantly lower on the hemiplegic side than on the healthy side in patients with episodic ischemic stroke during quiet breathing and forced breathing.The ultrasound two-dimensional speckle-tracking is more effective in assessing diaphragmatic dysfunction in stroke patients. |
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