Aim To determine the inspiratory muscle recruitment pattern in healthy children during inspiration, and effect of posture.
Method Surface EMG from scalene (sEMGsc), parasternal intercostal (sEMGpara), and diaphragm (sEMGdi) muscle were recorded in healthy children inspiring over 5 seconds from functional residual capacity (FRC) to total lung capacity (TLC), sitting then supine. sEMGsc, sEMGpara, and sEMGdi were determined at 11 time points across inspiration denoted as 0% and 100% of TLC. The respiratory muscle EMG were normalised to the maximal EMG (EMG%Max) achieved.
Results Ten healthy children were included (mean age 9.89 years, SD 1.70; 6 boys). When sitting, scalene muscle activity started prior to inspiration, and commenced significantly earlier than parasternal muscle (p = 0.0047). The diaphragm EMG activity peaked first at mean 4.05 s (0.61) after onset of inspiration, followed by the parasternal (4.33s (0.82)) then the scalene muscle (4.53s (0.81)). The relative contribution of scalene, parasternal, and diaphragm muscle to lung volume varied. (figure) When supine, the TLC was significantly lower than when sitting (1.60L (0.3) vs 1.80L (0.42), p=0.01). Scalene had a higher activation profile in supine posture although not statistically significant.
Conclusion Healthy children’s neural respiratory drive had a curvilinear relationship with lung volume during dynamic inspiration.