Assessment of phrenic nerve pacers in a patient with Congenital Central Hypoventilation SyndromeTo the Editor:A 13-year-old patient with Congenital Central Hypoventilation Syndrome (CCHS) was transported to the emergency department following an unwitnessed syncopal event with associated cyanosis. She opened her eyes within a few minutes, her mental status returned to normal, and her oxygen saturation increased back to above 95%. Her parents reported she’s had two or three similar events over the past few months. She was born at 38-week gestation with recurrent central apnea noted immediately after birth. Genetic tests revealed that she was heterozygous for a 36 base pair duplication from nucleotide 729 to 764 of the PHOX2B gene (c 729_764dup36), which encodes an additional 12 alanine residues in the polyalanine tract of the PHOX2B protein (p.Ala244_Ala255dup12). With confirmation of a diagnosis of CCHS1, a tracheotomy was performed, and she was discharged home on positive pressure ventilation. By the end of her first year of life, she was able to be weaned to just mechanical ventilation when sleepy or asleep. At 5 years of age, bilateral phrenic nerve pacers were implanted, and she was successfully decannulated and transitioned from positive to negative pressure ventilation (Avery Diaphragm Pacing System, Avery Biomedical Devices, Inc, Commack, NY. At 7 years of age, she was diagnosed with absence epilepsy and placed on levetiracetam with resolution of her seizures. At 8 years of age, prolonged sinus pauses of up to 6 seconds were documented by an implantable loop recorder, and a cardiac pacemaker was implanted.Vital signs and physical examination in the ED were unremarkable, and neuro, cardiology, and pulmonary consults were obtained. There were no signs of infection; chest x-ray and electroencephalogram were unremarkable. Her cardiac pacemaker was interrogated, and there was no evidence that her cardiac pacemaker had been activated before, during, or after her syncopal episode. A 12-lead electrocardiogram (EKG) was obtained (figure 1). This EKG suggests her phrenic nerve pacemakers are functioning normally, with a set rate of 17 breaths per minute. Approximately every 3.5 seconds, 27 electrical pulses over 1.32 seconds are noted, particularly well seen on leads II, III, aVR, aVL, aVF, and V3-V6. Iron deficiency was noted, and it was subsequently confirmed that she suffered from menorrhagia. Her syncopal episode was judged most likely vasovagal in origin, exacerbated by iron deficiency anemia. Realizing the noteworthy aspects of the case, informed consent was obtained from the patient and her family to publish this case report. This case report is exempt from IRB approval by the New York Medical College Institutional Review Board as per the policy in their manual, “If case reports are not identifiable, there is no need…to contact or to submit any documents to the IRB”.Following the seminal work of Glenn WL, et al 2, diaphragmatic pacing has been utilized in patients with spinal cord injuries or patients with amyotrophic lateral sclerosis3. Some patients with CCHS are being transitioned to ventilation with phrenic nerve pacers, thus permitting tracheostomy closure4.Syncope is not uncommon in patients with congenital central hypoventilation syndrome. Patients with CCHS are at risk for life-threatening cardiac arrhythmia and may sometimes require cardiac pacemakers. Patients being ventilated with phrenic nerve pacers without a tracheostomy, are also at risk for obstructive sleep apnea. Patients with CCHS are prone to fainting, and tilt-table testing confirms they are prone to greater orthostatic decreases in blood pressure than healthy control patients.The artefact due to phrenic nerve pacer discharge in figure 1 has been previously demonstrated in the literature. In 1987, Auerbach and Dobelle reported trans telephonic monitoring of patients with implanted neurostimulators, including a similar figure to ours, using 2 EKG leads5. A similar figure was published in a case report of a patient who developed ventricular tachycardia and cardiac arrest during diaphragmatic pacing, and on polysomnography in a patient with CCHS.In conclusion, a routine EKG may be an easy and quick way to determine if phrenic nerve pacers are functioning properly. Both the frequency and amplitude of phrenic nerve stimulation can be estimated on an EKG.

Introduction: A major focus in CF care aims to increase weight gain. Rates of overweight and obese people with CF have gradually increased over the past decade. Obesity could be a risk for restriction of lung volumes and airway obstruction as well as increase rates of pulmonary exacerbations in people with CF. Methods: Patients 6 years of age and older were categorized into weight categories based on the CDC definitions. A retrospective chart review was conducted to obtain lung function testing and other outcomes. Results: 107 patients with a median age of 20.6 years were included in this analysis. 8.4%, 64%, 18% and 10% of patients were underweight, normal/healthy weight, overweight and obese respectively. FEV1 and FVC (% predicted) did not differ between patients with weights in the normal range vs. patients in the overweight/obese categories. Linear regression analysis showed a direct correlation between BMI and FEV1 that continued as BMI entered overweight and obese categories in both pediatric and adult patients. Overweight/obese patients did not have increased rates of pulmonary exacerbations compared to those in the normal/healthy weight category. Conclusion: As CF therapies continue to improve, an increasing number of people with CF are exceeding the CDC’s normal weight range. Gaining weight past the normal range does not appear to negatively impact pulmonary health of people with CF. If this trend of increased weight gain continues, it remains to be seen if it will eventually negatively affect lung health.