Diaphragm pacing with a quadripolar phrenic nerve electrode: an international study.

We sought to determine the international experience with the quadripolar diaphragm pacer system and to test two hypotheses: the incidence of pacer complications would be (1) increased among pediatric as compared to adult patients; and (2) highest among active pediatric patients with idiopathic congenital central hypoventilation syndrome (CCHS). Data were collected via a questionnaire coupled with the Atrotech Registry data for a total of 64 patients (35 children and 29 adults) from 14 countries. Thoracic implantation of electrodes and bilateral pacer use each occurred in 94% of all subjects. Tetraplegic (vs pediatric CCHS) patients were more typically paced 24 hours/day (P = 0.001). Pacing duration averaged 2.0 +/- 1.0 years among children and 2.2 +/- 1.1 years among adults. Infections occurred among 2.9% of surgical procedures, all in pediatric CCHS patients (vs pediatric tetraplegic patients, P = 0.01). The incidence of mechanical trauma was 3.8%, without significant differences among patient groups. The incidence of presumed electrode and receiver failure were 3.1% and 5.9%, respectively, with internal component failure greater among pediatric CCHS than pediatric tetraplegic patients (P < 0.01). Intermittent or absent function of 0-4 electrode combinations occurred among 19% of all patients, with increased frequency among pediatric CCHS than pediatric tetraplegic patients (P < 0.03). Complication-free successful pacing occurred in 60% of pediatric and 52% of adult patients. In all, 94% of the pediatric and 86% of the adult patients paced successfully after the necessary intervention. Although pacer complications were not increased among pediatric as compared to adult patients, the incidence of complications was highest among the active pediatric patients with CCHS. Longitudinal study of these patients will provide invaluable information for modification and improvement of the quadripolar system.

Prolonged cardiorespiratory monitoring of children more than twelve months of age: characterization of events and approach to discontinuation.

We assessed children referred to our apnea program who were > or = 12 months of age, beyond the at-risk period for sudden infant death syndrome (SIDS), but for whom home cardiorespiratory monitoring had continued. Our objectives were to (1) determine reasons for initiation and continuation of monitoring, (2) apply documented monitoring of transthoracic impedance, electrocardiographic signals, and, in a subset of patients, pulse oximetry, to determine the types of cardiorespiratory events that these children experienced, and (3) describe how documented monitoring was applied for eventual discontinuation of monitoring. Among 45 patients (median age, 22 months), 263 disks were collected, representing 2982 monitor days. Indications for initiation of monitoring included an apparent life-threatening event in 51.1% of patients, apnea of prematurity in 35.5%, history of SIDS or apparent life-threatening event in a relative in 9%, and intrauterine drug exposure in 4.4%. Continuation of monitoring had been based on continued alarms and, in 31% of patients, documented apnea, bradycardia, or hemoglobin desaturation. In 40 of 45 patients, 2292 episodes of apnea (17.5% of all events) were recorded (range, 16 to 31 seconds). Five patients had 223 episodes of bradycardia (1.7% of all events). Of all 13,075 recorded events, 76.8% resulted in audible alarms, but only 3.9% of these alarms were for apnea and 2.2% were for bradycardia. Of 19 patients studied with pulse oximetry, 18 had 663 episodes of hemoglobin desaturation <90%. All children were thriving at the time of referral. Discontinuation of monitoring was based on a child's ability to resume breathing spontaneously or on normalization of heart rate or hemoglobin saturation before the audible alarm sounded, for a minimum of 2 to 3 months. By extension of the audible apnea alarm to 25 or 30 seconds, lowering of the cutoff point for bradycardia alarm, or lowering of the cutoff point for the oximetry alarm, a recommendation to discontinue monitoring could be made for 41 patients. Of these, no child had a recurrence of cardiorespiratory events or died of SIDS. Documented monitoring proved to be a useful clinical tool for investigation of the clinical and physiologic importance of these cardiorespiratory events in children beyond the at-risk period for SIDS; recommendations about discontinuation of monitoring could be made knowledgeably and safely.

Polysomnography in obese children with a history of sleep-associated breathing disorders.

We hypothesized that obese children with a history of breathing difficulty during sleep would demonstrate (1) evidence of complete and partial obstructive sleep apnea (OSA) with hypercarbia and/or hypoxemia; and (2) correlation between symptoms, degree of obesity, adenoid and tonsil size, and polysomnography (PSG) results. We evaluated 32 obese children [% ideal body weight (IBW), 196 +/- 45%] with a sleep history questionnaire, airway radiographs, electrocardiograms (ECG), and PSG. By history, we found snoring (100%), difficulty breathing (59%), sweating (44%), restlessness (53%), arousals (41%), apnea (50%), worsening with upper respiratory infection (URI) (81%), hypersomnolence (59%), and mouth breathing (59%). We found adenoid and/or tonsil enlargement on 75% of airway x-ray pictures. ECGs were abnormal in 5 patients. Among all patients, mean sleep study oxyhemoglobin saturation (SaO2) was 85 +/- 16% and mean end-tidal CO2 (PetCO2) was 51 +/- 7 torr; 84% had paradoxical inward movement of the chest on inspiration, 59% had OSA, and 66% had partial OSA. In those with > or = 200% IBW and adenotonsillar enlargement, elevated PetCO2 and the presence of hypoxemia (SaO2 < 90%) for > or = 5% of the total sleep time (TST) were correlated, unlike in patients of similar weight but without adenotonsillar enlargement. Individuals symptoms did not correlate with the severity of PSG abnormalities. By discriminant analysis, using three variables (IBW, presence of adenotonsillar tissue, and presence of > or = 5 symptoms), we could predict PSG abnormalities with up to 81% reliability. Our findings indicate that in obese children, particularly those with %IBW > or = 200 and adenotonsillar hypertrophy, with sleep-disordered breathing evaluation by polysomnography should be considered.

Congenital central hypoventilation syndrome: diagnosis, management, and long-term outcome in thirty-two children.

The diagnosis, management, and long-term outcome of 32 patients with congenital central hypoventilation syndrome are summarized. Sleep hypoventilation was severe in all cases, resulting in an alveolar carbon dioxide pressure (mean +/- SEM) of 62 +/- 2.5 mm Hg and a hemoglobin saturation of 65% +/- 3.3% without ventilatory or arousal response. Awake hypoventilation on initial assessment was present in 12 of the 32 patients, resulting in an alveolar carbon dioxide pressure of 58 +/- 2.2 mm Hg and a hemoglobin saturation of 59% +/- 7%. Associated conditions included pulmonary hypertension or cor pulmonale or both (78%), heart block and sick sinus syndrome requiring a cardiac pacemaker (two patients), mild atrophy by cranial imaging evidence (40%), seizures (72%), normal brain-stem auditory evoked responses in all but one patient tested, ganglioneuroblastomas (one patient), Hirschsprung disease (16%), and ophthalmologic abnormalities (60%). Growth was deficient in 44% of patients; hypotonia or major motor delay or both were apparent in all. Twenty-two patients are living; 12 of them require continuous ventilatory support and 10 breathe spontaneously while awake and require ventilatory support while asleep. Ten patients have died. Autopsy performed in six cases indicated diffuse central nervous system astrocytosis, gliosis, and atrophy but no primary brain-stem abnormality. Although these data support a diffuse central nervous system process, the specific cause and the mode of inheritance remain unclear. With early diagnosis and careful ventilatory management, the sequelae of hypoxia and morbidity should be minimized and long-term outcome improved.