Diaphragmatic electromyography in infants: an overview of possible clinical applications

Preterm infants often experience breathing instability and a hampered lung function. Therefore, these infants receive cardiorespiratory monitoring and respiratory support. However, the current respiratory monitoring technique may be unreliable for especially obstructive apnea detection and classification and it does not provide insight in breathing effort. The latter makes the selection of the adequate mode and level of respiratory support difficult. Electromyography of the diaphragm (dEMG) has the potential of monitoring heart rate (HR) and respiratory rate (RR), and it provides additional information on breathing effort. This review summarizes the available evidence on the clinical potential of dEMG to provide cardiorespiratory monitoring, to synchronize patient-ventilator interaction, and to optimize the mode and level of respiratory support in the individual newborn infant. We also try to identify gaps in knowledge and future developments needed to ensure widespread implementation in clinical practice. IMPACT: Preterm infants require cardiorespiratory monitoring and respiratory support due to breathing instability and a hampered lung function. The current respiratory monitoring technique may provide unreliable measurements and does not provide insight in breathing effort, which makes the selection of the optimal respiratory support settings difficult. Measuring diaphragm activity could improve cardiorespiratory monitoring by providing insight in breathing effort and could potentially have an important role in individualizing respiratory support in newborn infants.

Doxapram Treatment and Diaphragmatic Activity in Preterm Infants

BACKGROUND

Doxapram is a treatment option for severe apnea of prematurity (AOP). However, the effect of doxapram on the diaphragm, the main respiratory muscle, is not known.

OBJECTIVES

To investigate the effect of doxapram on diaphragmatic activity measured with transcutaneous electromyography of the diaphragm (dEMG).

METHODS

A pilot study was conducted in a tertiary neonatal intensive care unit. Diaphragmatic activity was measured from 30 min before up to 3 h after the start of doxapram treatment. dEMG parameters were compared to baseline (5 min before doxapram treatment) and at 15, 60, 120 and 180 min after the start of doxapram infusion.

RESULTS

Eleven preterm infants were included with a mean gestational age of 25.5 ± 1.2 weeks and birth weight of 831 ± 129 g. The amplitudedEMG, peakdEMG and tonicdEMG values did not change in the 3 h after the start of doxapram infusion compared to baseline. Clinically, the number of apnea episodes in the 24 h after doxapram treatment decreased significantly.

CONCLUSION

Doxapram infusion does not alter diaphragmatic activity measured with transcutaneous dEMG in preterm infants with AOP, indicating that its working mechanism is primarily on respiratory drive and not on respiratory muscle activity.

Classifying Apnea of Prematurity by Transcutaneous Electromyography of the Diaphragm

BACKGROUND

Treatment of apnea is highly dependent on the type of apnea. Chest impedance (CI) has inaccuracies in monitoring respiration, which compromises accurate apnea classification. Electrical activity of the diaphragm measured by transcutaneous electromyography (EMG) is feasible in preterm infants and might improve the accuracy of apnea classification.

OBJECTIVES

To compare the accuracy of apnea classification based on diaphragmatic EMG (dEMG) and CI tracings in preterm infants.

METHODS

Fifteen cases of central apnea, 5 of obstructive apnea, and 10 of mixed apnea were selected from recordings containing synchronized continuous tracings of respiratory inductive plethysmography (RIP), airway flow, heart rate (HR), oxygen saturation (SpO2), and breathing activity measured by dEMG and CI. Twenty-two assessors (neonatologists, pediatricians-in-training, and nurses) classified each apnea twice; once based on dEMG, HR, and SpO2 tracings, and once based on CI, HR, and SpO2. The assessors were blinded to the type of respiratory tracing (dEMG or CI) and to the RIP and flow tracings.

RESULTS

In total 1,320 assessments were performed, and in 71.1% the apnea was classified correctly. Subgroup analysis based on respiratory tracing showed that 74.8% of the dEMG tracings were classified correctly compared to 67.3% of the CI tracings (p < 0.001). This improved apnea classification based on dEMG was present for central (86.7 vs. 80.3%, p < 0.02) and obstructive (56.4 vs. 32.7%, p < 0.001) apnea. The improved apnea classification based on dEMG tracing was independent of the type of assessor.

CONCLUSION

Transcutaneous dEMG improves the accuracy of apnea classification when compared to CI in preterm infants, making this technique a promising candidate for future monitoring systems.

Breath detection by transcutaneous electromyography of the diaphragm and the Graseby capsule in preterm infants

OBJECTIVE

To compare triggering, breath detection and delay time of the Graseby capsule (GC) and transcutaneous electromyography of the diaphragm (dEMG) in spontaneous breathing preterm infants.

METHODS

In this observational study, a 30 minutes respiration measurement was conducted by respiratory inductance plethysmography (RIP), the GC, and dEMG in stable preterm infants. Triggering was investigated with an in vitro set-up using the Infant Flow^® SiPAP^TM system. The possibility to optimize breath detection was tested by developing new algorithms with the abdominal RIP band (RIP_AB ) as gold standard. In a subset of breaths, the delay time was calculated between the inspiratory onset in the RIP_AB signal and in the GC and dEMG signal.

RESULTS

Fifteen preterm infants with a mean gestational age of 28 ± 2 weeks and a mean birth weight of 1086 ± 317 g were included. In total, 14 773 breaths were analyzed. Based on the GC and dEMG signal, the Infant Flow^® SiPAP™ system, respectively, triggered 67.8% and 62.6% of the breaths. Breath detection was improved to 99.9% for the GC and 113.4% for dEMG in new algorithms. In 1492 stable breaths, the median delay time of inspiratory onset detection was +154 ms (IQR +118 to +164) in the GC and -50 ms (IQR -90 to -22) in the dEMG signal.

CONCLUSION

Breath detection using the GC can be improved by optimizing the algorithm. Transcutaneous dEMG provides similar breath detection but with the advantage of detecting the onset of inspiration earlier than the GC.

Electrical activity of the diaphragm during nCPAP and high flow nasal cannula

OBJECTIVE

To determine if the electrical activity of the diaphragm, as measure of neural respiratory drive and breathing effort, changes over time in preterm infants transitioned from nasal continuous positive airway pressure (nCPAP) to high flow nasal cannula (HFNC).

DESIGN

Prospective observational study.

SETTING

Neonatal intensive care unit.

PATIENTS

Stable preterm infants transitioned from nCPAP to HFNC using a 1:1 pressure to flow ratio.

INTERVENTIONS

The electrical activity of the diaphragm was measured by transcutaneous electromyography (dEMG) from 30 min before until 3 hours after the transition.

MAIN OUTCOME MEASURES

At eight time points after the transition to HFNC, diaphragmatic activity was compared with the baseline on nCPAP. Percentage change in amplitude_dEMG, peak_dEMG and tonic_dEMG were calculated. Furthermore, changes in respiratory rate, heart rate and fraction of inspired oxygen (FiO₂) were analysed.

RESULTS

Thirty-two preterm infants (mean gestational age: 28.1±2.2 weeks, mean birth weight: 1118±368 g) were included. Compared with nCPAP, the electrical activity of the diaphragm did not change during the first 3 hours on HFNC (median (IQR) change in amplitude_dEMG at t=180 min: 2.81% (-21.51-14.10)). The respiratory rate, heart rate and FiO₂ remained stable during the 3-hour measurement.

CONCLUSIONS

Neural respiratory drive and breathing effort assessed by electrical activity of the diaphragm is similar in the first 3 hours after transitioning stable preterm infants from nCPAP to HFNC with a 1:1 pressure-to-flow ratio.

Diaphragmatic activity during weaning from respiratory support in preterm infants

OBJECTIVE

To determine if weaning from nasal continuous positive airway pressure (nCPAP) to lesser supportive low flow nasal cannula (LFNC) results in a change in electrical activity of the diaphragm in preterm infants.

DESIGN

Prospective observational study.

SETTING

Neonatal intensive care unit.

PATIENTS

Stable preterm infants weaned from nCPAP to LFNC (1 L/min).

MAIN OUTCOME MEASURES

Change in diaphragmatic activity, expressed as amplitude, peak and tonic activity, measured by transcutaneous electromyography (dEMG) from 30 min before (baseline) until 180 min after weaning. Subgroup analysis was performed based on success or failure of the weaning attempt.

RESULTS

Fifty-nine preterm infants (gestational age: 29.0±2.4 weeks, birth weight: 1210±443 g) accounting for 74 weaning attempts were included. A significant increase in dEMG amplitude (median, IQR: 21.3%, 3.6-41.4), peak (22.1%, 8.7-40.5) and tonic activity (14.3%, -1.9-38.1) was seen directly after weaning. This effect slowly decreased over time. Infants failing the weaning attempt tended to have a higher diaphragmatic activity than those successfully weaned.

CONCLUSIONS

Weaning from nCPAP to LFNC leads to an increase in diaphragmatic activity measured by dEMG and is most prominent in preterm infants failing the weaning attempt. dEMG monitoring might be a useful parameter to guide weaning from respiratory support in preterm infants.

Transcutaneous electromyography of the diaphragm: A cardio-respiratory monitor for preterm infants

INTRODUCTION

Chest impedance (CI) is the current standard for cardio-respiratory monitoring in preterm infants but fails to provide direct and quantitative information on diaphragmatic activity. Transcutaneous electromyography (dEMG) is able to measure diaphragmatic activity, but its feasibility and repeatability to monitor respiratory rate (RR) and heart rate (HR) in preterm infants needs to be established.

METHODS

RR and HR were measured simultaneously by dEMG and CI for 1-hour on day 1, 3, and 7 of life in 31 preterm infants (gestational age 29.6 ± 1.8 weeks; birth weight 1380 ± 350 g) on non-invasive respiratory support. Six fixed 1-minute time intervals were selected from each 1-hour recording and both RR and HR were calculated using all intervals or only those with stable dEMG and CI recordings.

RESULTS

dEMG was well tolerated and signal quality was good. Both RR and HR measured by dEMG and CI were significantly correlated (RR: r = 0.85, HR: r = 0.98) and showed good agreement by the Bland-Altman plot (mean difference (limits of agreement): RR: -2.3 (-17.3 to 12.7) breaths/min and HR: -0.3 (-5.3 to 4.7) beats/min. When analyzing only stable recordings, the correlation (r = 0.92) and agreement (-1.8 (-12.3 to 8.7) breaths/min) for RR improved. Subgroup analyses for postnatal age, gestational age, and mode of support showed similar results suggesting good repeatability of dEMG.

CONCLUSION

This study shows that monitoring RR and HR with transcutaneous dEMG is feasible and repeatable in preterm infants.

The Effect of Caffeine on Diaphragmatic Activity and Tidal Volume in Preterm Infants

OBJECTIVE

To determine the effect of caffeine on diaphragmatic activity, tidal volume (Vt), and end-expiratory lung volume (EELV) in preterm infants.

STUDY DESIGN

Using transcutaneous electromyography of the diaphragm (dEMG), we measured diaphragmatic activity from 30 minutes before (baseline) to 3 hours after administration of an intravenous caffeine-base loading dose in 30 spontaneously breathing preterm infants (mean gestational age, 29.1 ± 1.3 weeks), most of whom were on noninvasive respiratory support. Diaphragmatic activity was expressed as the percentage change in dEMG amplitude, area under the curve, respiratory rate, and inspiratory and expiratory times. Using respiratory inductive plethysmography, we measured changes in Vt and EELV from baseline. These outcome variables were calculated at 8 fixed time points after caffeine administration (5, 15, 30, 60, 90, 120, 150, and 180 minutes) and compared with baseline.

RESULTS

Caffeine administration resulted in rapid (within 5 minutes) increases in dEMG amplitude (median, 43%; IQR, 24%-63%; P < .001) and area under the curve (median, 28%; IQR, 14%-48%; P < .001). Vt also increased by a median of 30% (IQR, 7%-48%), and this change was significantly correlated with the change in dEMG amplitude (r = 0.67; P < .001). These effects were relatively stable until 120 minutes after caffeine administration. Caffeine did not consistently impact EELV, respiratory rate, or inspiratory and expiratory times.

CONCLUSION

Caffeine treatment results in a rapid and sustained increase in diaphragmatic activity and Vt in preterm infants.

Diagnosis of Hemidiaphragmatic Paresis in a Preterm Infant with Transcutaneous Electromyography: A Case Report

Transcutaneous electromyography of the diaphragm (dEMG) is a noninvasive and easy applicable tool to measure the electrical activity of the diaphragm. dEMG monitoring has recently been introduced in the neonatal intensive care unit as a novel cardiorespiratory monitor providing direct information on diaphragmatic breathing activity. We report a preterm infant with suspected paresis of the right diaphragm measured with transcutaneous dEMG, which showed a clear reduction in the electrical activity of the right-sided diaphragm. In conclusion, dEMG provides valuable information on regional diaphragmatic activity, which can assist the clinician in diagnosing hemidiaphragmatic paresis.