Monitoring Diaphragm Electrical Activity and the Detection of Congenital Central Hypoventilation Syndrome in a Newborn

Home , Sleep apnea

PERINATAL/NEONATAL CASE PRESENTATION Monitoring diaphragm electrical activity and the detection of congenital central hypoventilation syndrome in a newborn

T Szczapa1, J Beck2, M Migdal3 and J Gadzinowski1

A full-term newborn infant is described with recurrent episodes of oxygen desaturation and apnea on the day of birth. The apnea did not improve with continuous positive airway pressure (CPAP) and intermittent nasal ventilation, therefore intubation and mechanical ventilation were required. A preliminary diagnosis of congenital central hypoventilation syndrome (CCHS) was made with the use of simultaneous measurements of end-tidal CO2 (EtCO2) and a diaphragm electrical activity waveform that was detected using microsensors placed on the infant’s feeding tube. It was observed that during deep sleep, the diaphragm electrical activity waveform was close to 0 mV (central apnea) and EtCO2 levels rose accordingly (central hypoventilation). Genetic testing subsequently revealed a Phox2b mutation, establishing the diagnosis of CCHS. Simultaneously measuring diaphragm electrical activity and EtCO2 is feasible and may be a valuable bedside diagnostic tool in cases of suspected CCHS before the diagnosis is conﬁrmed with genetic testing.

Journal of Perinatology (2013) 33, 905–907; doi:10.1038/jp.2013.89 Keywords: congenital central hypoventilation syndrome; newborn; diaphragm electrical activity; central apnea; mechanical ventilation; Phox2b mutation

INTRODUCTION Linda, CA, USA). Nasal continuous positive airway pressure (CPAP) Congenital central hypoventilation syndrome (CCHS) is a rare and intermittent nasal ventilation was insufficient to maintain a disorder defined by impaired automatic control of breathing. normal clinical- and pulmonary laboratory state. Hence, the baby Patients typically present with alveolar hypoventilation primarily required intubation and mechanical ventilation with synchronized while asleep.1 Sensitivity to hypercapnia and hypoxia is decreased, intermittent mandatory ventilation (SIMV) combined with pressure and ventilatory support is required in affected individuals. First support (PS) mode (Servo-I ventilator, Maquet, Solna, Sweden). symptoms are usually observed in the neonatal period. The At 19 days after birth, the infant was extubated but required paired-like homeobox 2B gene (Phox2b) was found to be the non-invasive respiratory support (BiPhasic mode of the Infant Flow disease-defining gene for CCHS.1 Today, the control of breathing SiPAP device) while asleep for reoccurring apnea. From birth, can be routinely and clinically monitored in infants requiring apneic episodes were observed whenever the baby went to sleep. mechanical ventilation, via measurements of the diaphragm While awake, the baby was breathing regularly without any clinical electrical activity (EAdi).2,3 Miniaturized microsensors mounted signs of increased work of breathing. No metabolic disorders were on a naso/orogastric feeding tube detect the spontaneous diagnosed in this patient. Cerebral anomalies and congenital heart breathing activity, and impose no additional invasiveness to defects were ruled out by ultrasound studies. The baby revealed infants being fed enterally while on mechanical ventilation. The no pathological findings on ophthalmic and neurological exam- EAdi waveform provides information about the neural respiratory inations. Electroencephalography recording was normal. effort,2 and in its absence, it is an indicator of central apnea. The older sister of this patient suffers from cerebral palsy. The child requires home mechanical ventilation using a tracheostomy, because apnea always occurs when she goes to sleep, a clinical CASE characteristic shared by this index case. Based on these findings in A 4560-g female baby was born at 38 weeks of gestation by the patient and the older sibling, a disorder involving the central Cesarean section. The course of pregnancy was uneventful, but regulation of breathing was suspected. the decision regarding the mode of delivery was taken because of In order to assess the neural respiratory drive and respiratory postnatal complications in a prior sibling who has cerebral palsy of control, the electrical activity of the diaphragm (EAdi) was unclear origin. The newborn in this case report was breathing measured. This was achieved by a commercially available sensor spontaneously after birth, but presented with apnea in the third placed in the esophagus (NAVA catheter, Maquet Critical Care) at minute of life. Cord blood gases were normal (pH ¼ 7.37, the level of the gastro-esophageal junction (Figure 1).4 The sensor base excess ¼ –0.3). Because of recurrent episodes of desaturation also has the capability of feeding, similar to a standard naso- and apnea associated with respiratory acidosis and hypercapnia gastric feeding tube, and therefore, imposes no additional (with PaCO2 reaching 90 mm Hg), the infant was treated with non- invasiveness. End-tidal CO2 (EtCO2) was simultaneously invasive ventilatory support (Infant Flow SiPAP, Carefusion, Yorba measured (CO2 Analyzer Module, Maquet Critical Care). During

1Department of Neonatology, Poznan University of Medical Sciences, Poznan, Poland; 2Keenan Research Centre, Li Ka Shing Knowledge Institute, St Michael’s Hospital, Toronto, Ontario, Canada and 3Pediatric Intensive Care Unit, Children’s Memorial Health Institute, Warsaw, Poland. Correspondence: Dr T Szczapa, Department of Neonatology, Poznan University of Medical Sciences, ul. Polna 33, Poznan 60-535, Poland. E-mail: [email protected] Received 13 May 2013; accepted 19 June 2013 Diaphragm electrical activity and congenital central hypoventilation Szczapa et al. 906 or nasal CPAP alone is utilized. Thus, some ventilatory assistance is mandated during the diagnostic testing. Upon return of more consistent and elevated EAdi values and breathing, the EtCO2 returned to normal values after B20 min. Based on those findings, a preliminary diagnosis of CCHS was made. To confirm the diagnosis, a blood sample was sent to Embryology and Genetics Department of L’hoˆpital Necker-Enfants Malades in Paris, France. Phox2b direct sequencing showed a heterozygous variation of the stop codon leading to an extension of the Phox2b protein (c.945A4T, p.X315CextX41). This genetic mutation confirmed a diagnosis of CCHS for this patient. Genetic testing of the older sister identified the same mutation.

DISCUSSION This is the first occurrence of CCHS in siblings with an identified Phox2b mutation in Poland. The diagnosis of CCHS in the index case was based on standard criteria: hypoventilation episodes Figure 1. NAVA catheter (Maquet Critical Care). 1—connection to the module used for electrical activity of the diaphragm (EAdi) during sleep, early age of onset, and absence of primary neuromuscular, lung, cardiac, metabolic disease or any brainstem measurements, 2—microsensors, 3—nutrition feed and 4—scale in 1 cm from the tip. pathology. The infant had persistent apnea when falling asleep and thus fulfilled the definition of CCHS. Central hypoventilation was confirmed by monitoring diaphragmatic electrical activity in combination with EtCO2 measurements. Similar findings were recently reported.5 The EAdi is a signal that is representative of central respiratory drive.4 In its absence, it is an indication of central apnea2, assuming the catheter with the sensors is adequately positioned, and this was confirmed in the index case with the use of the built-in catheter positioning window. During central apnea, diaphragmatic activity signal was not detected in our patient during non-aroused sleep. The described methodology allows the distinction between central and obstructive apneas as obstructive pathophysiology always demonstrates diaphragmatic contractions.6 Occasional EAdi signals were observed during the apnea period in the index case (Figure 2). This monitoring disparity may be caused by changes in the state of consciousness of the infant (that is, deep sleep versus brief arousal events), although sporadic artifacts cannot be excluded. Early diagnosis is crucial because CCHS that goes unrecognized in early infancy may result in sudden unexpected deaths or life- Figure 2. Simultaneous presentation of electrical activity of the threatening episodes of apnea. Survivors often manifest different diaphragm (EAdi; bottom panel) and end-tidal CO2 (EtCO2) (top 7,8 panel) during a 3-hour recording while the infant was breathing on types of cerebral injury, and hence an early diagnosis and synchronized intermittent mandatory ventilation (SIMV; see text for treatment is needed to prevent these complications. The method ventilator settings). Episodes of sleep hypoventilation are high- of simultaneously measuring electrical activity of the diaphragm lighted by the shadowed regions. During central apnea, the EAdi and EtCO2 presented here allows a tentative diagnosis of CCHS values drop to zero, and are indicated by solid black symbols. Note when genetic testing is not readily available. the clear and sustained increase in EtCO levels during periods of 2 Based on this case report, synchronized EAdi and EtCO2 central apnea. monitoring is achievable and provides a valuable diagnostic tool in cases of suspected CCHS before the results of genetic tests return to the clinician. This method should facilitate the diagnosis the period of simultaneous EtCO2 and EAdi monitoring (Figure 2), of this rare disease. the following SIMV settings were used (SIMV þ PSV mode): ventilator rate ¼ 30 per minute, PIP ¼ 18 cm H2O, PEEP ¼ 5cm H O, PS level 10 cm H O, and FiO 21%. 2 ¼ 2 2 ¼ CONFLICT OF INTEREST We observed that if the infant went into deep sleep (assessed by a physician using the Brazelton’s Neonatal Behavioral Assess- Dr Beck has made inventions related to neural control of mechanical ventilation that are patented. The license for these patents belongs to Maquet Critical Care. Future ment Scale definition), the following events occurred: (a) the commercial uses of this technology may provide financial benefit to Dr Beck through EtCO2 concentration levels increased (maximum observed value royalties. Dr Beck owns 50% of Neurovent Research Inc (NVR). NVR is a research and was 70 mm Hg) despite assisted ventilation at the same time and development company that builds the equipment and catheters for research studies. (b) the EAdi signal was extremely low (if not absent) indicating NVR has a consulting agreement with Maquet Critical Care. The other authors declare central apnea. The simultaneous recordings of central respiratory no conflict of interest. drive (EAdi) during different states of consciousness and development of hypercapnia (EtCO2) are presented in Figure 2. During sleep depicted by the gray shadowed bars, EAdi decreased with REFERENCES more frequent ‘zero values’, and concurrently EtCO2 increased and 1 Weese-Mayer DE, Berry-Kravis EM, Ceccherini I, Keens TG, Loghmanee DA, remained elevated during deep sleep and persistent apnea. Life- Trang H. ATS Congenital Central Hypoventilation Syndrome Subcommittee. An threatening desaturation and hypercarbia occur if no intervention official ATS clinical policy statement: Congenital central hypoventilation syndrome:

Journal of Perinatology (2013), 905 – 907 & 2013 Nature America, Inc. Diaphragm electrical activity and congenital central hypoventilation Szczapa et al. 907 genetic basis, diagnosis, and management. Am J Respir Crit Care Med 2010; 181(6): 5 Rahmani A, Rehman NU, Chedid F. Neurally adjusted ventilatory assist (NAVA) 626–644. mode as an adjunct diagnostic tool in congenital central hypoventilation syn- 2 Beck J, Reilly M, Grasselli G, Qui H, Slutsky AS, Dunn MS, Sinderby CA. Characteri- drome. J Coll Physicians Surg Pak 2013; 23: 154–156. zation of neural breathing pattern in spontaneously breathing preterm infants. 6 Luo YM, Tang J, Jolley C, Steier J, Zhong NS, Moxham J, Polkey MI. Distinguishing Pediatr Res 2011; 70: 607–613. obstructive from central sleep apnea events: diaphragm electromyogram and 3 Stein H, Alosh H, Ethington P, White DB. Prospective crossover comparison esophageal pressure compared. Chest 2009; 135: 1133–1141. between NAVA and pressure control ventilation in premature neonates 7 Kumar R, Macey PM, Woo MA, Harper RM. Rostral brain axonal injury in congenital less than 1500 grams. J Perinatol 2013; 33: 452–456. central hypoventilation syndrome. J Neurosci Res 2010; 88: 2146–2154. 4 Sinderby C, Beck J, Spahija J, Weinberg J, Grassino A. Voluntary activation of the 8 Macey PM, Moiyadi AS, Kumar R, Woo MA, Harper RM. Decreased cortical thickness human diaphragm in health and disease. J Appl Physiol 1998; 85: 2146–2158. in central hypoventilation syndrome. Cereb Cortex 2012; 22: 1728–1737.

& 2013 Nature America, Inc. Journal of Perinatology (2013), 905 – 907