DISCUSSION
Recently, point-of-care LUS has been used with growing interest in emergency settings. In a review, ultrasound was defined as the “visual stethoscope” of the 21st century ²⁰. Diaphragm ultrasound is also easy to learn and perform, and the assessments take a short time. It seems that DUS can be easily carried out while performing LUS in the emergency department. Diaphragm ultrasound provides objective, measurable parameters to the clinician, as clinical evaluation or treatment strategies are mostly performed based on subjective clinical findings and thus reflect individual variability. For this reason, in a crowded emergency setting, DUS helps the clinician obtain more objective, reliable, and measurable data. To our knowledge, this is the first study evaluating diaphragm parameters with ultrasound in previously healthy children with pneumonia.
To date, most of the studies about DUS have been performed in adults ¹⁵, ²¹²⁴. There are few such studies in children, and in those studies, diaphragmatic dysfunction was evaluated mostly in intensive care units. Diaphragm parameters were obtained to predict diaphragmatic fatigue after cardiac surgery or successful weaning from mechanic ventilation ²⁵²⁷. Diaphragm thickness and TF were found to be important predictors of extubation success from mechanic ventilators; TF of <17% was associated with weaning failure. In a few studies, normal values of diaphragm parameters in healthy infants/children were also evaluated ²⁸,²⁹. None of these studies evaluated all of the parameters that we used to assess diaphragm function. There is one study about previously healthy infants with bronchiolitis aged 1–12 months, evaluating ultrasonographic examinations of the diaphragm to predict the severity of respiratory distress and outcomes ³⁰. To our knowledge, this is the first study measuring ES with DUS in addition to these parameters.
El-Halaby et al. ²⁸ evaluated the measurements of diaphragmatic excursion and thickness in healthy infants and children. They divided patients into 4 groups according to age and obtained measurements. Correlating our findings with theirs, both diaphragmatic excursion and thickness values were lower than those of even the youngest age group, suggesting that pneumonia causes diaphragmatic dysfunction. Moreover, TF values were associated with the severity of the pneumonia, indicating that diaphragm contractility decreases as the disease severity progresses. Inspiratory slope and ES values were also correlated with PRESS scores, suggesting that inspiratory and expiratory efforts were increased in cases of severe pneumonia. Length of stay in the hospital was correlated with IS and ES as a practical predictor for outcome. Buonsenso et al. ³⁰ found that severe bronchiolitis patients had lower TF than in moderate or mild cases, but there was no statistically significant difference. Thickening fraction was found to have a correlation with SpO2 at first evaluation in bronchiolitis patients. Diaphragm excursion was lower in patients with moderate eco scores than in those with mild or normal scores, but there was no statistically significant difference between mild and normal eco scores. They concluded that IS measurements were higher in patients who required respiratory support for bronchiolitis, consistent with our study. Additionally, we found that IS and ES values were both associated with the need for respiratory support, signaling that higher inspiratory and expiratory efforts would predict worsening outcomes. In our study, it was shown that there were significant positive correlations between both IS and ES and respiratory rate, while they had negative correlations with SpO2 levels evaluated at the time of admission to the emergency department. Furthermore, TF values were negatively correlated with respiratory rate. Interestingly, there was no difference between PRESS groups according to diaphragm excursion measurements. This discrepancy may be due to the different pathological features of the two diseases, namely bronchiolitis and pneumonia, respectively.
Our study has some limitations. First, the number of patients was not high enough to establish groups according to age and weight and compare the DUS parameters between them according to severity scores. Nevertheless, diaphragmatic excursion and thickness measurements were lower than those of the youngest healthy age group recorded in another study (30), suggesting that pneumonia does cause diaphragmatic dysfunction. Second, we did not obtain DUS results after recovery, so differences in measurements in the healthy and sick periods were not evaluated.
In conclusion, DUS may be a promising and useful tool to assess diaphragmatic dysfunction in patients diagnosed with pneumonia. Diaphragm parameters, especially TF, IS, and ES, may provide objective and reliable information to predict the severity of the illness, the need for respiratory support, and outcomes. Nevertheless, studies with larger case series are required to reveal the benefits of diaphragm ultrasound in children with different diagnoses.