Ictal Central Apnea Is Predictive of Mesial Temporal Seizure Onset: An Intracranial Investigation.

OBJECTIVE: Ictal central apnea (ICA) is a semiological sign of focal epilepsy, associated with temporal and frontal lobe seizures. In this study, using qualitative and quantitative approaches, we aimed to assess the localizational value of ICA. We also aimed to compare ICA clinical utility in relation to other seizure semiological features of focal epilepsy. METHODS: We analyzed seizures in patients with medically refractory focal epilepsy undergoing intracranial stereotactic electroencephalographic (SEEG) evaluations with simultaneous multimodal cardiorespiratory monitoring. A total of 179 seizures in 72 patients with reliable artifact-free respiratory signal were analyzed. RESULTS: ICA was seen in 55 of 179 (30.7%) seizures. Presence of ICA predicted a mesial temporal seizure onset compared to those without ICA (odds ratio = 3.8, 95% confidence interval = 1.3-11.6, p = 0.01). ICA specificity was 0.82. ICA onset was correlated with increased high-frequency broadband gamma (60-150Hz) activity in specific mesial or basal temporal regions, including amygdala, hippocampus, and fusiform and lingual gyri. Based on our results, ICA has an almost 4-fold greater association with mesial temporal seizure onset zones compared to those without ICA and is highly specific for mesial temporal seizure onset zones. As evidence of symptomatogenic areas, onset-synchronous increase in high gamma activity in mesial or basal temporal structures was seen in early onset ICA, likely representing anatomical substrates for ICA generation. INTERPRETATION: ICA recognition may help anatomoelectroclinical localization of clinical seizure onset to specific mesial and basal temporal brain regions, and the inclusion of these regions in SEEG evaluations may help accurately pinpoint seizure onset zones for resection. ANN NEUROL 2024;95:998-1008.

Effect of lateral position on rostral fluid shift and relationship to severity of Cheyne-Stokes respiration in heart failure patients.

PURPOSE: Lateral sleep position has a significant beneficial effect on the severity of Cheyne-Stokes respiration with central sleep apnea (CSR-CSA) in patients with heart failure (HF). We hypothesized that a reduction in rostral fluid shift from the legs in this position compared with the supine position may contribute to this effect. METHODS: In patients with CSR-CSA and an apnea-hypopnea index (AHI) ≥ 15/h (by standard polysomnography), uncalibrated leg fluid volume was measured in the supine, left lateral decubitus, and right lateral decubitus positions (in-laboratory assessment). The correlation between postural changes in fluid volume and corresponding changes in AHI was evaluated. Since there was no difference in both leg fluid volume and AHI between the right and left positions, measurements in these two conditions were combined into a single lateral position. RESULTS: In 18 patients with CSR-CSA, leg fluid volume increased by 2.7 ± 3.1% (p = 0.002) in the lateral position compared to the supine position, while AHI decreased by 46 ± 20% (p < 0.0001) with the same postural change. The correlation between postural changes in AHI and leg fluid volume was 0.22 (p = 0.42). Changes in leg fluid volume were a slow phenomenon, whereas changes in CSR-CSA severity were almost synchronous with changes in posture. CONCLUSION: Lateral position causes a reduction in rostral fluid shift compared to the supine position, but this change does not correlate with the corresponding change in CSR-CSA severity. The two changes occur on different time scales. These findings question the role of postural changes in rostral fluid shift as a determinant of corresponding changes in CSR-CSA severity.

Cerebral Autoregulation during Orthostatic Challenge in Congenital Central Hypoventilation Syndrome.

Rationale: Congenital central hypoventilation syndrome (CCHS) is a rare autonomic disorder with altered regulation of breathing, heart rate (HR), and blood pressure (BP). Aberrant cerebral oxygenation in response to hypercapnia/hypoxia in CCHS raises the concern that altered cerebral autoregulation may contribute to CCHS-related, variably impaired neurodevelopment. Objectives: To evaluate cerebral autoregulation in response to orthostatic challenge in CCHS cases versus controls. Methods: CCHS and age- and sex-matched control subjects were studied with head-up tilt (HUT) testing to induce orthostatic stress. Fifty CCHS and 100 control HUT recordings were included. HR, BP, and cerebral oxygen saturation (regional oxygen saturation) were continuously monitored. The cerebral oximetry index (COx), a real-time measure of cerebral autoregulation based on these measures, was calculated. Measurements and Main Results: HUT resulted in a greater mean BP decrease from baseline in CCHS versus controls (11% vs. 6%; P < 0.05) and a diminished increase in HR in CCHS versus controls (11% vs. 18%; P < 0.01) in the 5 minutes after tilt-up. Despite a similar COx at baseline, orthostatic provocation within 5 minutes of tilt-up caused a 50% greater increase in COx (P < 0.01) and a 29% increase in minutes of impaired autoregulation (P < 0.02) in CCHS versus controls (4.0 vs. 3.1 min). Conclusions: Cerebral autoregulatory mechanisms appear to be intact in CCHS, but the greater hypotension observed in CCHS consequent to orthostatic provocation is associated with greater values of COx/impaired autoregulation when BP is below the lower limits of autoregulation. Effects of repeated orthostatic challenges in everyday living in CCHS necessitate further study to determine their influence on neurodevelopmental disease burden.

Endotyping Sleep Apnea One Breath at a Time: An Automated Approach for Separating Obstructive from Central Sleep-disordered Breathing.

Rationale: Determining whether an individual has obstructive or central sleep apnea is fundamental to selecting the appropriate treatment. Objectives: Here we derive an automated breath-by-breath probability of obstruction, as a surrogate of gold-standard upper airway resistance, using hallmarks of upper airway obstruction visible on clinical sleep studies. Methods: From five nocturnal polysomnography signals (airflow, thoracic and abdominal effort, oxygen saturation, and snore), nine features were extracted and weighted to derive the breath-by-breath probability of obstruction (Pobs). A development and initial test set of 29 subjects (development = 6, test = 23) (New York, NY) and a second test set of 39 subjects (Solingen, Germany), both with esophageal manometry, were used to develop Pobs and validate it against gold-standard upper airway resistance. A separate dataset of 114 subjects with 2 consecutive nocturnal polysomnographies (New York, NY) without esophageal manometry was used to assess the night-to-night variability of Pobs. Measurements and Main Results: A total of 1,962,229 breaths were analyzed. On a breath-by-breath level, Pobs was strongly correlated with normalized upper airway resistance in both test sets (set 1: cubic adjusted [adj.] R2 = 0.87, P < 0.001, area under the receiver operating characteristic curve = 0.74; set 2: cubic adj. R2 = 0.83, P < 0.001, area under the receiver operating characteristic curve = 0.7). On a subject level, median Pobs was associated with the median normalized upper airway resistance (set 1: linear adj. R2 = 0.59, P < 0.001; set 2: linear adj. R2 = 0.45, P < 0.001). Median Pobs exhibited low night-to-night variability [intraclass correlation(2, 1) = 0.93]. Conclusions: Using nearly 2 million breaths from 182 subjects, we show that breath-by-breath probability of obstruction can reliably predict the overall burden of obstructed breaths in individual subjects and can aid in determining the type of sleep apnea.

Obstructive Apneas in a Mouse Model of Congenital Central Hypoventilation Syndrome.

Rationale: Congenital central hypoventilation syndrome (CCHS) is characterized by life-threatening sleep hypoventilation and is caused by PHOX2B gene mutations, most frequently the PHOX2B27Ala/+ mutation, with patients requiring lifelong ventilatory support. It is unclear whether obstructive apneas are part of the syndrome. Objectives: To determine if Phox2b27Ala/+ mice, which present the main symptoms of CCHS and die within hours after birth, also express obstructive apneas, and to investigate potential underlying mechanisms. Methods: Apneas were classified as central, obstructive, or mixed by using a novel system combining pneumotachography and laser detection of abdominal movement immediately after birth. Several respiratory nuclei involved in airway patency were examined by immunohistochemistry and electrophysiology in brainstem-spinal cord preparations. Measurements and Main Results: The median (interquartile range) of obstructive apnea frequency was 2.3 (1.5-3.3)/min in Phox2b27Ala/+ pups versus 0.6 (0.4-1.0)/min in wild types (P < 0.0001). Obstructive apnea duration was 2.7 seconds (2.3-3.9) in Phox2b27Ala/+ pups versus 1.7 seconds (1.1-1.9) in wild types (P < 0.0001). Central and mixed apneas presented similar significant differences. In Phox2b27Ala/+ preparations, the hypoglossal nucleus had fewer (P < 0.05) and smaller (P < 0.01) neurons, compared with wild-type preparations. Importantly, coordination of phrenic and hypoglossal motor activities was disrupted, as evidenced by the longer and variable delay of hypoglossal activity with respect to phrenic activity onset (P < 0.001). Conclusions: The Phox2b27Ala/+ mutation predisposed pups not only to hypoventilation and central apneas, but also to obstructive and mixed apneas, likely because of hypoglossal dysgenesis. These results thus demand attention toward obstructive events in infants with CCHS.

Obstructive sleep apneas naturally occur in mice during REM sleep and are highly prevalent in a mouse model of Down syndrome.

STUDY OBJECTIVES: The use of mouse models in sleep apnea study is limited by the belief that central (CSA) but not obstructive sleep apneas (OSA) occur in rodents. We aimed to develop a protocol to investigate the presence of OSAs in wild-type mice and, then, to apply it to a validated model of Down syndrome (Ts65Dn), a human pathology characterized by a high incidence of OSAs. METHODS: In a pilot study, nine C57BL/6J wild-type mice were implanted with electrodes for electroencephalography (EEG), neck electromyography (nEMG), and diaphragmatic activity (DIA), and then placed in a whole-body-plethysmographic (WBP) chamber for 8 h during the rest (light) phase to simultaneously record sleep and breathing activity. CSA and OSA were discriminated on the basis of WBP and DIA signals recorded simultaneously. The same protocol was then applied to 12 Ts65Dn mice and 14 euploid controls. RESULTS: OSAs represented about half of the apneic events recorded during rapid-eye-movement-sleep (REMS) in each experimental group, while the majority of CSAs were found during non-rapid eye movement sleep. Compared with euploid controls, Ts65Dn mice had a similar total occurrence rate of apneic events during sleep, but a significantly higher occurrence rate of OSAs during REMS, and a significantly lower occurrence rate of CSAs during NREMS. CONCLUSIONS: Mice physiologically exhibit both CSAs and OSAs. The latter appear almost exclusively during REMS, and are highly prevalent in Ts65Dn. Mice may, thus, represent a useful model to accelerate the understanding of the pathophysiology and genetics of sleep-disordered breathing and to help the development of new therapies.

Spontaneous and apnea arousals from sleep in preterm infants.

BACKGROUND: The significance of arousal in apnea termination in preterm infants is not known. METHODS: We investigated the appearance of arousals from sleep with polysomnography for 21 preterm infants at a median age of 36 gestational weeks. RESULTS: The polysomnographic appearance of sleep was fragmented by frequent arousals. The number of spontaneous arousals unrelated to apneas was 18 per hour in sleep; higher in rapid eye movement (REM) sleep than in non-REM sleep (p < 0.001). Eighty-two percent of arousals were regarded as spontaneous, and 18% were related to apneas. In turn, arousal followed 5% of all apneas; 30% of mixed, 2% of central, and 20% of long apneas defined as apnea of prematurity. Apneas without an arousal led to lower oxygen saturation levels than those followed by an arousal (p < 0.001). Mixed apneas with an arousal had stronger breathing effort and a higher number of breaths compared with apneas without an arousal (p < 0.05). CONCLUSIONS: In preterm infants, frequent spontaneous arousals or arousal-type phenomena make the polysomnographic appearance of sleep fragmented. However, even long apneas or hypoxia commonly fail to elicit arousals or any sign of sleep interruption. Our findings suggest that arousal appears not to be the main mechanism for apnea termination in preterm infants. IMPACT: Polysomnographic appearance of sleep in preterm infants is fragmented by arousals. Contrary to older children and adults, arousal to apnea is uncommon in preterm infants. Even long mixed apneas with desaturation mostly fail to elicit an arousal response. In preterm infants, apnea termination appears not to depend on an arousal. Low arousability is suggested to be caused by a low ventilation response to hypoxia.

Chronic Opioid Use and Central Sleep Apnea, Where Are We Now and Where To Go? A State of the Art Review.

Opioids are commonly used for pain management, perioperative procedures, and addiction treatment. There is a current opioid epidemic in North America that is paralleled by a marked increase in related deaths. Since 2000, chronic opioid users have been recognized to have significant central sleep apnea (CSA). After heart failure-related Cheyne-Stokes breathing (CSB), opioid-induced CSA is now the second most commonly seen CSA. It occurs in around 24% of chronic opioid users, typically after opioids have been used for more than 2 months, and usually corresponds in magnitude to opioid dose/plasma concentration. Opioid-induced CSA events often mix with episodes of ataxic breathing. The pathophysiology of opioid-induced CSA is based on dysfunction in respiratory rhythm generation and ventilatory chemoreflexes. Opioids have a paradoxical effect on different brain regions, which result in irregular respiratory rhythm. Regarding ventilatory chemoreflexes, chronic opioid use induces hypoxia that appears to stimulate an augmented hypoxic ventilatory response (high loop gain) and cause a narrow CO2 reserve, a combination that promotes respiratory instability. To date, no direct evidence has shown any major clinical consequence from CSA in chronic opioid users. A line of evidence suggested increased morbidity and mortality in overall chronic opioid users. CSA in chronic opioid users is likely to be a compensatory mechanism to avoid opioid injury and is potentially beneficial. The current treatments of CSA in chronic opioid users mainly focus on continuous positive airway pressure (CPAP) and adaptive servo-ventilation (ASV) or adding oxygen. ASV is more effective in reducing CSA events than CPAP. However, a recent ASV trial suggested an increased all-cause and cardiovascular mortality with the removal of CSA/CSB in cardiac failure patients. A major reason could be counteracting of a compensatory mechanism. No similar trial has been conducted for chronic opioid-related CSA. Future studies should focus on (1) investigating the phenotypes and genotypes of opioid-induced CSA that may have different clinical outcomes; (2) determining if CSA in chronic opioid users is beneficial or detrimental; and (3) assessing clinical consequences on different treatment options on opioid-induced CSA.

Effects of central apneas on sympathovagal balance and hemodynamics at night: impact of underlying systolic heart failure.

BACKGROUND: Increased sympathetic drive is the key determinant of systolic heart failure progression, being associated with worse functional status, arrhythmias, and increased mortality. Central sleep apnea is highly prevalent in systolic heart failure, and its effects on sympathovagal balance (SVB) and hemodynamics might depend on relative phase duration and background pathophysiology. OBJECTIVE: This study compared the effects of central apneas in patients with and without systolic heart failure on SVB and hemodynamics during sleep. METHODS: During polysomnography, measures of SVB (heart rate and diastolic blood pressure variability) were non-invasively recorded and analyzed along with baroreceptor reflex sensitivity and hemodynamic parameters (stroke volume index, cardiac index, total peripheral resistance index). Data analysis focused on stable non-rapid eye movement N2 sleep, comparing normal breathing with central sleep apnea in subjects with and without systolic heart failure. RESULTS: Ten patients were enrolled per group. In heart failure patients, central apneas had neutral effects on SVB (all p > 0.05 for the high, low, and very low frequency components of heart rate and diastolic blood pressure variability). Patients without heart failure showed an increase in very low and low frequency components of diastolic blood pressure variability in response to central apneas (63 ± 18 vs. 39 ± 9%; p = 0.001, 43 ± 12 vs. 31 ± 15%; p = 0.002). In all patients, central apneas had neutral hemodynamic effects when analyzed over a period of 10 min, but had significant acute hemodynamic effects. CONCLUSION: Effects of central apneas on SVB during sleep depend on underlying systolic heart failure, with neutral effects in heart failure and increased sympathetic drive in idiopathic central apneas.

Sleep disordered breathing (SDB) in neonates and implications for its long-term impact.

Sleep-disordered breathing (SDB) is a significant cause of morbidity in neonates and young infants. SDB occurs more commonly in preterm infants and in neonates with underlying syndromes. Recent evidence shows that infants with obstructive sleep apnoea (OSA) or SDB have greater health care resource utilization, including longer hospital stay. Management of SDB includes non-invasive ventilation or surgical interventions tailored to the patient. Screening high risk newborns should allow for early diagnosis and timely therapeutic intervention for this population. However, the thresholds for diagnosing SDB and for guiding and implementing treatment in neonates remain unclear. A collective effort is required to standardize the practice worldwide. This article will discuss neonatal sleep physiology and characteristics of neonatal sleep, with an emphasis on the epidemiology and diagnosis of SDB in neonates and its implications for long term outcomes.

Assessing ventilatory control stability in children with and without an elevated central apnoea index.

BACKGROUND AND OBJECTIVE: Frequent central apnoeas are sometimes observed in healthy children; however; the pathophysiology of an elevated central apnoea index (CAI) is poorly understood. A raised CAI may indicate underlying ventilatory control instability (i.e. elevated loop gain, LG) or a depressed ventilatory drive. This pilot study aimed to compare LG in otherwise healthy children with an elevated CAI to healthy controls. METHODS: Polysomnographic recordings from children (age > 6 months) without obstructive sleep apnoea and with a CAI > 5 events/h (n = 13) were compared with age and gender-matched controls with a CAI < 5 events/h (n = 13). Spontaneous sighs were identified during non-rapid eye movement (NREM) sleep, and breath-breath measurements of ventilation were derived from the nasal pressure signal. A standard model of ventilatory control (gain, time constant and delay) was used to calculate LG by transforming ventilatory fluctuations seen in response to a sigh into a ventilatory-drive signal that best matches observed ventilation. RESULTS: The high CAI group had an elevated LG (median = 0.36 (interquartile range, IQR = 0.35-0.53) vs 0.28 (0.23-0.36); P ≤ 0.01). There was no difference in either the time constant (P = 0.63) or delay (P = 0.29) between groups. Elevated LG observed in the high CAI group remained after accounting for degree of hypoxia (average oxygen saturation (SpO2 ) during each analysable window) experienced (0.40 (0.30-0.53) vs 0.25 (0.23-0.37); P = 0.04). CONCLUSION: An elevated CAI in otherwise healthy children is associated with a raised LG compared to matched controls with a low CAI, irrespective of level of hypoxia. This relative ventilatory instability helps explain the high CAI and may ultimately be able to help guide diagnosis and management in patients with high CAI.

Association of serious adverse events with Cheyne-Stokes respiration characteristics in patients with systolic heart failure and central sleep apnoea: A SERVE-Heart Failure substudy analysis.

BACKGROUND AND OBJECTIVE: Increases in Cheyne-Stokes respiration (CSR) cycle length (CL), lung-to-periphery circulation time (LPCT) and time to peak flow (TTPF) may reflect impaired cardiac function. This retrospective analysis used an automatic algorithm to evaluate baseline CSR-related features and then determined whether these could be used to identify patients with systolic heart failure (HF) who experienced serious adverse events in the Treatment of Sleep-Disordered Breathing with Predominant Central Sleep Apnea by Adaptive Servo Ventilation in Patients with Heart Failure (SERVE-HF) substudy. METHODS: A total of 280 patients had overnight diagnostic polysomnography data available; an automated algorithm was applied to quantify CSR-related features. RESULTS: Median baseline CL, LPCT and TTPF were similar in the control (n = 152) and adaptive servo-ventilation (ASV, n = 156) groups. In both groups, CSR-related features were significantly longer in patients who did (n = 129) versus did not (n = 140) experience a primary endpoint event (all-cause death, life-saving cardiovascular intervention or unplanned hospitalization for worsening HF): CL, 61.1 versus 55.1 s (P = 0.002); LPCT, 36.5 versus 31.5 s (P < 0.001); TTPF, 15.20 versus 13.35 s (P < 0.001), respectively. This finding was independent of treatment allocation. CONCLUSION: Patients with systolic HF and central sleep apnoea who experienced serious adverse events had longer CSR CL, LPCT and TTPF. Future studies should examine an independent role for CSR-related features to enable risk stratification in systolic HF.

Distinguishing Obstructive Versus Central Apneas in Infrared Video of Sleep Using Deep Learning: Validation Study.

BACKGROUND: Sleep apnea is a respiratory disorder characterized by an intermittent reduction (hypopnea) or cessation (apnea) of breathing during sleep. Depending on the presence of a breathing effort, sleep apnea is divided into obstructive sleep apnea (OSA) and central sleep apnea (CSA) based on the different pathologies involved. If the majority of apneas in a person are obstructive, they will be diagnosed as OSA or otherwise as CSA. In addition, as it is challenging and highly controversial to divide hypopneas into central or obstructive, the decision about sleep apnea type (OSA vs CSA) is made based on apneas only. Choosing the appropriate treatment relies on distinguishing between obstructive apnea (OA) and central apnea (CA). OBJECTIVE: The objective of this study was to develop a noncontact method to distinguish between OAs and CAs. METHODS: Five different computer vision-based algorithms were used to process infrared (IR) video data to track and analyze body movements to differentiate different types of apnea (OA vs CA). In the first two methods, supervised classifiers were trained to process optical flow information. In the remaining three methods, a convolutional neural network (CNN) was designed to extract distinctive features from optical flow and to distinguish OA from CA. RESULTS: Overnight sleeping data of 42 participants (mean age 53, SD 15 years; mean BMI 30, SD 7 kg/m2; 27 men and 15 women; mean number of OA 16, SD 30; mean number of CA 3, SD 7; mean apnea-hypopnea index 27, SD 31 events/hour; mean sleep duration 5 hours, SD 1 hour) were collected for this study. The test and train data were recorded in two separate laboratory rooms. The best-performing model (3D-CNN) obtained 95% accuracy and an F1 score of 89% in differentiating OA vs CA. CONCLUSIONS: In this study, the first vision-based method was developed that differentiates apnea types (OA vs CA). The developed algorithm tracks and analyses chest and abdominal movements captured via an IR video camera. Unlike previously developed approaches, this method does not require any attachment to a user that could potentially alter the sleeping condition.

Diving responses elicited by nasopharyngeal irrigation mimic seizure-associated central apneic episodes in a rat model.

The spread of epileptic seizure activity to brainstem respiratory and autonomic regions can elicit episodes of obstructive apnea and of central apnea with significant oxygen desaturation and bradycardia. Previously, we argued that central apneic events were not consequences of respiratory or autonomic activity failure, but rather an active brainstem behavior equivalent to the diving response resulting from seizure spread. To test the similarities of spontaneous seizure-associated central apneic episodes to evoked diving responses, we used nasopharyngeal irrigation with either cold water or mist for 10 or 60 s to elicit the diving response in urethane-anesthetized animals with or without kainic acid-induced seizure activity. Diving responses included larger cardiovascular changes during mist stimuli than during water stimuli. Apneic responses lasted longer than 10 s in response to 10 s stimuli or about 40 s in response to 60 s stimuli, and outlasted bradycardia. Repeated 10 s mist applications led to an uncoupling of the apneic episodes (which always occurred) from the bradycardia (which became less pronounced with repetition). These uncoupled events matched the features of observed spontaneous seizure-associated central apneic episodes. The duration of spontaneous central apneic episodes correlated with their frequency, i.e. longer events occurred when there were more events. Based on our ability to replicate the properties of seizure-associated central apneic events with evoked diving responses during seizure activity, we conclude that seizure-associated central apnea and the diving response share a common neural basis and may reflect an attempt by brainstem networks to protect core physiology during seizure activity.

How to implant a phrenic nerve stimulator for treatment of central sleep apnea?

BACKGROUND: Central sleep apnea (CSA) is a breathing disorder caused by the intermittent absence of central respiratory drive. Transvenous phrenic nerve stimulation is a new therapeutic option, recently approved by the FDA , for the treatment of CSA. OBJECTIVE: To describe the technique used to implant the transvenous phrenic nerve stimulation system (the remede System, Respicardia, Inc). METHODS: The remede System is placed in the pectoral region, typically on the right side. A single stimulation lead is placed in either the left pericardiophrenic vein (PPV) or the right brachiocephalic vein (RBC). A sensing lead is placed into the azygous vein to detect respiration. RESULTS: In the remede System Pivotal trial, 147 of 151 (97%) patients were successfully implanted with the system. Sixty-two percent of stimulation leads were placed in the PPV and 35% in the RBC. Mean procedure time was 2.7 ± 0.8 hours and 94% of patients were free from implant-related serious adverse events through 6 months. CONCLUSION: In patients with CSA, transvenous phrenic nerve stimulation is an effective and safe therapy with an implant procedure similar to that of cardiac implantable electronic devices.

Brainstem activity, apnea, and death during seizures induced by intrahippocampal kainic acid in anaesthetized rats.

OBJECTIVE: To investigate how prolonged seizure activity affects cardiorespiratory function and activity of pre-Bötzinger complex, leading to sudden death. METHODS: Urethane-anesthetized female Long-Evans rats were implanted with nasal thermocouple; venous and arterial cannulae; and electrodes for electrocardiography (ECG) and hippocampal, cortical, and brainstem recording. Kainic acid injection into the ventral hippocampus induced status epilepticus. RESULTS: Seizures caused hypertension, tachycardia, and tachypnea punctuated by recurrent transient apneas. Salivation increased considerably: in 11 of 12 rats, liquid with alkaline pH consistent with saliva was expelled from the mouth. Most transient apneas were obstructive: nasal airflow ceased, while, in 83%, efforts to breathe persisted as continued rhythmic activity of respiratory pre-Bötzinger neurons, inspiratory electromyography (EMG), and excursions of the chest wall and abdomen. Blood pressure oscillated in time with respiratory efforts. This pattern also occurred in a minority of cases (16%) of incomplete apnea, but not in rare cases (1%) of transient central apneas. During transient obstructive apneas, the frequency of all inspiratory efforts decreased abruptly by ~30%, suggesting a resetting of the central respiratory rhythm generator. Twenty-two of thirty-one rats died, due either to obstructive apnea (12) or central apnea following progressive slowing of respiration (10). Most rats dying of central apnea had experienced several transient obstructive apneas. Negative DC field potential shifts of the brainstem followed the final breath, consistent with previous reports on spreading depolarization in mouse models. Timing suggests that the DC shift is a consequence rather than cause of respiratory collapse. Cardiac activity continued for tens of seconds. SIGNIFICANCE: Seizure activity in forebrain induces pronounced autonomic activation and disrupts activity in medullary respiratory centers, resulting in death from either obstructive or central apnea. These results directly inform mechanisms of death in status epilepticus, and indirectly provide clues to mechanisms of sudden unexpected death in epilepsy (SUDEP).

The association of serotonin reuptake inhibitors and benzodiazepines with ictal central apnea.

OBJECTIVE: Ictal (ICA) and postconvulsive central apnea (PCCA) have been implicated in sudden unexpected death in epilepsy (SUDEP) pathomechanisms. Previous studies suggest that serotonin reuptake inhibitors (SRIs) and benzodiazepines (BZDs) may influence breathing. The aim of this study was to investigate if chronic use of these drugs alters central apnea occurrence in patients with epilepsy. METHODS: Patients with epilepsy admitted to epilepsy monitoring units (EMUs) in nine centers participating in a SUDEP study were consented. Polygraphic physiological parameters were analyzed, including video-electroencephalography (VEEG), thoracoabdominal excursions, and pulse oximetry. Outpatient medication details were collected. Patients and seizures were divided into SRI, BZD, and control (no SRI or BZD) groups. Ictal central apnea and PCCA, hypoxemia, and electroclinical features were assessed for each group. RESULTS: Four hundred and seventy-six seizures were analyzed (204 patients). The relative risk (RR) for ICA in the SRI group was half that of the control group (p = 0.02). In the BZD group, ICA duration was significantly shorter than in the control group (p = 0.02), as was postictal generalized EEG suppression (PGES) duration (p = 0.021). Both SRI and BZD groups were associated with smaller seizure-associated oxygen desaturation (p = 0.009; p ≪ 0.001). Neither presence nor duration of PCCA was significantly associated with SRI or BZD (p ≫ 0.05). CONCLUSIONS: Seizures in patients taking SRIs have lower occurrence of ICA, and patients on chronic treatment with BZDs have shorter ICA and PGES durations. Preventing or shortening ICA duration by using SRIs and/or BZD in patients with epilepsy may play a possible role in SUDEP risk reduction.

Diagnosis, management and pathophysiology of central sleep apnea in children.

Central sleep apnea (CSA) is thought to occur in about 1-5% of healthy children. CSA occurs more commonly in children with underlying disease and the presence of CSA may influence the course of their disease. CSA can be classified based on the presence or absence of hypercapnia as well as the underlying condition it is associated with. The management of CSA needs to be tailored to the patient and may include medication, non-invasive ventilation, and surgical intervention. Screening children at high risk will allow for earlier diagnosis and timely therapeutic interventions for this population. The review will highlight the pathophysiology, prevalence and diagnosis of CSA in children. An algorithm for the management of CSA in healthy children and children with underlying co-morbidities will be outlined.

Airway Obstruction during Sleep due to Diaphragm Pacing Precludes Decannulation in Young Children with CCHS.

Children with congenital central hypoventilation syndrome (CCHS) have a PHOX2B mutation-induced control of breathing deficit necessitating artificial ventilation as life support. A subset of CCHS families seek phrenic nerve-diaphragm pacing (DP) during sleep with the goal of tracheal decannulation. Published data regarding DP during sleep as life support in the decannulated child with CCHS and related airway dynamics in young children are limited. We report a series of 3 children, ages 3.3-4.3 years, who underwent decannulation. Sleep endoscopy performed during DP revealed varied (oropharynx, supraglottic, glottic, etc.) levels of complete airway obstruction despite modification of pacer settings. Real-time analysis of end tidal CO2 and SpO2 confirmed inadequate gas exchange. Because the families declined re-tracheostomy, all 3 patients rely on noninvasive mask ventilation as a means of life support while asleep. These results emphasize the need for extreme caution in proceeding with tracheal decannulation in young children with CCHS who expect to use DP during sleep as life support. Parents and patients should anticipate that they will depend on noninvasive mask ventilation (rather than DP) during sleep after undergoing decannulation. This information may improve management and guide expectations regarding potential decannulation in young paced children with CCHS.

More than Heart Failure: Central Sleep Apnea and Sleep-Related Hypoventilation.

Central sleep apnea (CSA) comprises a variety of breathing patterns and clinical entities. They can be classified into 2 categories based on the partial pressure of carbon dioxide in the arterial blood. Nonhypercapnic CSA is usually characterized by a periodic breathing pattern, while hypercapnic CSA is based on hypoventilation. The latter CSA form is associated with central nervous, neuromuscular, and rib cage disorders as well as obesity and certain medication or substance intake. In contrast, nonhypercapnic CSA is typically accompanied by an overshoot of the ventilation and often associated with heart failure, cerebrovascular diseases, and stay in high altitude. CSA and hypoventilation syndromes are often considered separately, but pathophysiological aspects frequently overlap. An integrative approach helps to recognize underlying pathophysiological mechanisms and to choose adequate therapeutic strategies. Research in the last decades improved our insights; nevertheless, diagnostic tools are not always appropriately chosen to perform comprehensive sleep studies. This supports misinterpretation and misclassification of sleep disordered breathing. The purpose of this article is to highlight unresolved problems, raise awareness for different pathophysiological components and to discuss the evidence for targeted therapeutic strategies.