Gerard J. Hutten

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.

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

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.

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 amplitudedEMG, peakdEMG and tonicdEMG 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 amplitudedEMG 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.

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.

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.

The Effect of Minimally Invasive Surfactant Therapy on Diaphragmatic Activity

Background: Minimally invasive surfactant therapy (MIST) is increasingly used to treat preterm infants with respiratory distress syndrome (RDS). However, the effect of MIST on breathing effort is poorly studied. Objectives: To describe the effect of MIST on neural breathing effort assessed with transcutaneous electromyography of the diaphragm (dEMG) in preterm infants with RDS. Methods: Preterm infants with a gestational age < 37 weeks treated with MIST for RDS were included. dEMG measurements were done from 15 min before to 1 h after MIST. The percentage change in dEMG activity after MIST and the clinical response were analyzed. Results: Twenty preterm infants (mean gestational age 29.3 [SD 2.1] weeks; mean birth weight 1,230 [SD 391] g) were included. Seventeen infants did complete the 1-h measurement. Eleven (65%) infants had a decrease in their peakdEMG activity (median change –11.8% [IQR –26.8 to 5.8, p = 0.08]) 1 h after MIST. TonicdEMG activity decreased in 12 (71%) infants, with a median reduction of 6.3% (IQR –29.2 to 9.0, p = 0.07). FiO2 showed a rapid decrease following MIST (before, 0.47 [IQR 0.38–0.84]; 1 h after, 0.25 [IQR 0.21–0.30], p < 0.001). Conclusion: In addition to improved oxygenation, MIST results in a decrease in neural breathing effort measured by dEMG activity in the majority of preterm infants with RDS.

Patient-ventilator asynchrony in preterm infants on nasal intermittent positive pressure ventilation

Objective To describe the incidence of patient-ventilator asynchrony and different types of asynchrony in preterm infants treated with non-synchronised nasal intermittent positive pressure ventilation (nIPPV). Design An observational study was conducted including preterm infants born with a gestational age (GA) less than 32 weeks treated with non-synchronised nIPPV. During 1 hour, spontaneous breathing was measured with transcutaneous electromyography of the diaphragm simultaneous with ventilator inflations. An asynchrony index (AI), a percentage of asynchronous breaths, was calculated and the incidence of different types of inspiratory and expiratory asynchrony were reported. Results Twenty-one preterm infants with a mean GA of 26.0±1.2 weeks were included in the study. The mean inspiratory AI was 68.3%±4.7% and the mean expiratory AI was 67.1%±7.3%. Out of 5044 comparisons of spontaneous inspirations and mechanical inflations, 45.3% of the mechanical inflations occurred late, 23.3% of the mechanical inflations were early and 31.4% of the mechanical inflation were synchronous. 40.3% of 5127 expiratory comparisons showed an early termination of ventilator inflations, 26.7% of the mechanical inflations terminated late and 33.0% mechanical inflations terminated in synchrony with a spontaneous expiration. In addition, 1380 spontaneous breaths were unsupported and 611 extra mechanical inflations were delivered. Conclusion Non-synchronised nIPPV results in high patient-ventilator asynchrony in preterm infants during both the inspiratory and expiratory phase of the breathing cycle. New synchronisation techniques are urgently needed and should address both inspiratory and expiratory asynchrony.

High versus standard dose caffeine for apnoea: a systematic review

Background Placebo-controlled trials have shown that caffeine is highly effective in treating apnoea of prematurity and reduces the risk of bronchopulmonary dysplasia (BPD) and neurodevelopmental impairment (NDI). Objective To identify, appraise and summarise studies investigating the modulating effect of different caffeine dosages. Methods A systematic review identified all randomised controlled trials (RCTs) comparing a high versus a standard caffeine treatment regimen in infants with a gestational age <32 weeks, by searching the main electronic databases and abstracts of the Pediatric Academic Societies. Studies comparing caffeine to placebo or theophylline only were excluded. Primary outcomes were BPD and mortality at 36 weeks postmenstrual age. Secondary key-outcome was neurodevelopmental outcome at 12 and 24 months corrected age. Meta-analysis was performed using RevMan 5.3. Results Six RCTs including 620 infants were identified. Meta-analysis showed a significant decrease in BPD, the combined outcome BPD or mortality, and failure to extubate in infants allocated to a higher caffeine dose. No differences were found in mortality alone and NDI. The quality of the outcome measures were deemed low to very low according to the Grading of Recommendations Assessment, Development and Evaluation guidelines. Conclusions Although this review suggests that administering a higher dose of caffeine might enhance its beneficial effect on death or BPD, firm recommendations on the optimal caffeine dose cannot be given due to the low level of evidence. A large RCT is urgently needed to confirm or refute these findings and determine the optimal dose of caffeine.

O-218 The Effect Of Caffeine On Diaphragmatic Activity In Preterm Infants

Background Preterm infants born with a GA <32 weeks are at high risk of developing central apnea of prematurity (AOP). Treatment with caffeine reduces central AOP by stimulating the breathing centre. Animal studies suggest that caffeine improves contractility of the diaphragm. We have determined the effect of caffeine on diaphragmatic activity in preterm infants. Methods Spontaneously breathing preterm infants <32 weeks treated with an intravenous loading dose (10 mg/kg) of caffeine base for central AOP were eligible for the study. Diaphragmatic activity was continuously measured by transcutaneous electromyography (dEMG) starting 30-min before (baseline) until 1-hour after caffeine administration. Diaphragmatic inspiratory activity per breath, expressed as the relative amplitude change of dEMG (logEMGAR), area under the curve (AUC), respiratory rate (RR), as well as tidal volume (Vt ) measured by respiratory inductive plethysmography, were calculated at 4 fixed time points after caffeine administration (5,15,30 and 60-min) using the average of all breaths in a 30-sec recording and compared to baseline. Results 30 preterm infants (mean GA 29.1 ± 1.3 wk; birth weight 1237 ± 370 g) were included. 5-min after caffeine administration, diaphragmatic activity significantly increased (median, IQR) compared to baseline; logEMGAR (0.13, 0.09–0.17), corresponding with an amplitude increase of 35% (22–49%). AUC (19%, 11–34%) and Vt (30%, 7–48) also increased significantly. Caffeine did not impact RR. The increased activity was observed at all subsequent time points. Conclusions This is the first study showing that caffeine treatment, besides stimulating respiratory drive, results in a rapid (within 5-min) and sustained increase in diaphragmatic contractility in preterm infants.