An unusual cause of diaphragm pacer failure in congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome is a rare genetic disorder affecting ventilatory response to hypercapnia and/or hypoxemia. We describe a case of diaphragm pacing (DP) failure in a 38-year-old woman with congenital central hypoventilation syndrome who used DP as ventilatory support only during sleep for 24 years. Diagnostic evaluation began with examination of external DP equipment, but adjustment did not elicit adequate diaphragm contractions. Clinical evaluation and transtelephonic monitoring showed absent function of the right pacer and diminished function of the left pacer. The patient had surgical exploration of her internal DP components. The operation revealed that the right pacer receiver had significant circumferential calcium accumulation. After replacement of the receivers in subcutaneous pockets closer to the skin surface, robust diaphragm contractions bilaterally occurred with stimulation. This case suggests DP failure can result from development of calcification and increased distance from the skin surface to the receivers due to weight gain. CITATION: Kwon A, Lodge M, McComb JG, et al. An unusual cause of diaphragm pacer failure in congenital central hypoventilation syndrome. J Clin Sleep Med. 2022;18(3):949-952.

Images: Polysomnographic artifacts in a child with congenital central hypoventilation syndrome.

NONE: Diaphragm pacing (DP), a modality of ventilatory support in children with congenital central hypoventilation syndrome, generates respiration using the patient's own diaphragm as the respiratory pump. We report a 14-year-old boy with congenital central hypoventilation syndrome who uses DP with an uncapped tracheostomy during sleep. Polysomnography to titrate DP settings identified artifacts occurring in regular intervals coinciding with the onset of inspiration during all sleep stages in several channels including legs, snore, and electrocardiogram. Clinicians interpreting polysomnograms performed during DP should become familiar with the multichannel artifacts due to DP impulses. We also identified that our patient was hyperventilated on home DP settings that led to adjustment of DP settings during the polysomnogram to achieve optimal oxygenation and ventilation. Our case also highlights the utility of polysomnography to ensure optimal gas exchange during sleep in children with congenital central hypoventilation syndrome using DP.

Airway obstruction in congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome (CCHS) is the failure of the autonomic system to control adequate ventilation while asleep with preserved ventilatory response while awake. We report a case of a patient with CCHS who presented with intrathoracic and extrathoracic airway obstruction after tracheostomy tube decannulation and phrenic nerve pacer placement. Nocturnal polysomnography (NPSG) revealed hypoxia, hypercapnia and obstructive sleep apnoea, which required bilevel positive airway pressure titration. Airway endoscopy demonstrated tracheomalacia and paretic true vocal cords in the paramedian position during diaphragmatic pacing. Laryngeal electromyography demonstrated muscular electrical impulses that correlated with diaphragmatic pacer settings. Thus, we surmise that the patient's upper and lower airway obstruction was secondary to diaphragmatic pacer activity. Thorough airway evaluation, including NPSG and endoscopy, may help identify the side effects of diaphragmatic pacing, such as airway obstruction, in patients with CCHS.

Reversal of pulmonary hypertension after diaphragm pacing in an adult patient with congenital central hypoventilation syndrome.

INTRODUCTION: Patients with the congenital central hypoventilation syndrome (CCHS) suffer from life-threatening hypoventilation when asleep, making them dependent on mechanical ventilation (MV) at night or during naps. State-of-art respiratory management consists of intermittent positive-pressure ventilation via a tracheotomy or mask. In some patients hypoventilation is permanent, in which case ventilatory support must be extended to the waking hours. Diaphragm pacing can prove useful in such situations. 
 METHODS AND RESULTS: This report describes the case of a 26-year-old woman with CCHS in whom failure to achieve adequate MV led to life-threatening pulmonary hypertension (PH), with a systolic pulmonary artery pressure (PAP) of 80 mmHg and right ventricular hypertrophy, despite optimization of all possible measures and despite extensive therapeutic education efforts. Diaphragm pacing using laparoscopically implanted intradiaphragmatic phrenic nerve stimulation electrodes corrected alveolar hypoventilation and lastingly reversed PH (systolic PAP below 40 mmHg after 2 months, sustained after 2 years). Diaphragm pacing induced shoulder pain, however, involving the chronic use of analgesics. The pacing had to be stopped for tolerance reasons after two years, leading to PH worsening and the need for diurnal MV. 
 CONCLUSIONS: Diaphragm pacing appears likely effective to restore alveolar ventilation and reverse PH in adult CCHS patients.

An official ATS clinical policy statement: Congenital central hypoventilation syndrome: genetic basis, diagnosis, and management.

BACKGROUND: Congenital central hypoventilation syndrome (CCHS) is characterized by alveolar hypoventilation and autonomic dysregulation. PURPOSE: (1) To demonstrate the importance of PHOX2B testing in diagnosing and treating patients with CCHS, (2) to summarize recent advances in understanding how mutations in the PHOX2B gene lead to the CCHS phenotype, and (3) to provide an update on recommendations for diagnosis and treatment of patients with CCHS. METHODS: Committee members were invited on the basis of their expertise in CCHS and asked to review the current state of the science by independently completing literature searches. Consensus on recommendations was reached by agreement among members of the Committee. RESULTS: A review of pertinent literature allowed for the development of a document that summarizes recent advances in understanding CCHS and expert interpretation of the evidence for management of affected patients. CONCLUSIONS: A PHOX2B mutation is required to confirm the diagnosis of CCHS. Knowledge of the specific PHOX2B mutation aids in anticipating the CCHS phenotype severity. Parents of patients with CCHS should be tested for PHOX2B mutations. Maintaining a high index of suspicion in cases of unexplained alveolar hypoventilation will likely identify a higher incidence of milder cases of CCHS. Recommended management options aimed toward maximizing safety and optimizing neurocognitive outcome include: (1) biannual then annual in-hospital comprehensive evaluation with (i) physiologic studies during awake and asleep states to assess ventilatory needs during varying levels of activity and concentration, in all stages of sleep, with spontaneous breathing, and with artificial ventilation, and to assess ventilatory responsiveness to physiologic challenges while awake and asleep, (ii) 72-hour Holter monitoring, (iii) echocardiogram, (iv) evaluation of ANS dysregulation across all organ systems affected by the ANS, and (v) formal neurocognitive assessment; (2) barium enema or manometry and/or full thickness rectal biopsy for patients with a history of constipation; and (3) imaging for neural crest tumors in individuals at greatest risk based on PHOX2B mutation.

Ondine's curse with accompanying trigeminal and glossopharyngeal neuralgia secondary to medullary telangiectasia.

BACKGROUND: Central hypoventilation syndrome ("Ondine's Curse") is an infrequent disorder that can lead to serious acute or chronic health consequences. This syndrome, especially in adults, is rare, and even less frequent in the absence of clear pathogenic lesions on MRI. In addition, we are not aware of any previously reported cases with associated cranial nerve neuralgias. METHODS: We describe a patient with baseline trigeminal and glossopharyngeal neuralgia, admitted with episodes of severe hypoventilatory failure of central origin, consistent with "Ondine's Curse". After evaluation, she was found to have a medullary capillary telangiectasia, thought to be the causative lesion, and which could explain her complete neurologic and hypoventilatory syndrome. The patient was treated with placement of a diaphragmatic pacing system, which has been effective thus far. RESULTS: This case illustrates the need for investigation of centrally mediated apnea, especially when co-occurring cranial nerve neuralgia is present and cardiopulmonary evaluation is negative. It provides an example of capillary telangiectasia as the causative lesion, one that to our knowledge has not been reported before. CONCLUSIONS: Placement of a diaphragmatic pacing system was warranted and became lifesaving as the patient was deemed to be severely incapacitated by chronic ventilatory insufficiency.

Detection of hypoventilation during thoracoscopy: combined cutaneous carbon dioxide tension and oximetry monitoring with a new digital sensor.

BACKGROUND: Changes in Paco(2) have not been described during thoracoscopy under sedation-assisted local anesthesia. We hypothesized that hypoventilation might occur secondary to administration of sedatives and decreased ventilation in one lung. AIM: Prospectively measure cutaneous carbon dioxide tension (Pcco(2)) in addition to pulse oximetric saturation (Spo(2)) using a new combined digital sensor to examine the occurrence of hypoventilation during thoracoscopy under sedation-assisted local anesthesia. SETTING: University hospital. METHODS: Following validation studies, Pcco(2) was prospectively measured in 16 consecutive patients undergoing thoracoscopy under sedation-assisted local anesthesia using a combined digital earlobe sensor measuring Spo(2) (percentage) and Pcco(2) (millimeters of mercury). All patients received supplemental oxygen. Routine BP monitoring and Spo(2) was continued. Patients received IV hydrocodone, 5 mg, and intermittent boluses or IV midazolam and pethidine. RESULTS: Mean baseline Pcco(2) measurement was 39.1 +/- 7.2 mm Hg (+/- SD) [range, 27.5 to 50.5 mm Hg], and peak measurement during the procedure was 52.3 +/- 10.3 mm Hg (range, 37.2 to 77 mm Hg) [p < 0.001]. Median and mean changes in Pcco(2) measurement from baseline were 13.0 mm Hg and 13.2 +/- 5.3 mm Hg (range, 5.5 to 27.8 mm Hg), respectively. Mean fall in Spo(2) during the procedure was 4.6 +/- 3.2% (range, 1 to 14%). CONCLUSIONS: Thoracoscopy performed under sedation-assisted local anesthesia is associated with significant hypoventilation. Combined measurement of Spo(2) and Pcco(2) during thoracoscopy is a novel approach in the monitoring of ventilation, enhancing patient safety, and might allow to guide the administration of sedation in a better way.