Diagnosis and Management of Acute Respiratory Failure

Acute hypoxemic respiratory failure is defined by Pao2 less than 60 mm Hg or SaO2 less than 88% and may result from V/Q mismatch, shunt, hypoventilation, diffusion limitation, or low inspired oxygen tension. Acute hypercapnic respiratory failure is defined by Paco2 ≥ 45 mm Hg and pH less than 7.35 and may result from alveolar hypoventilation, increased fraction of dead space, or increased production of carbon dioxide. Early diagnostic maneuvers, such as measurement of SpO2 and arterial blood gas, can differentiate the type of respiratory failure and guide next steps in evaluation and management.

Images: Atypical presentation of congenital central hypoventilation syndrome in an infant with central and obstructive sleep apnea

Congenital central hypoventilation syndrome (CCHS), a rare disease caused by paired-like homeobox 2B variants, affects control of breathing. We report on a 21-month-old boy with CCHS caused by a novel nonpolyalanine repeat mutation, neuroblastoma, severe obstructive and central sleep apnea, and sleep-related hypoxemia without hypoventilation. At 10 months, due to persistent central sleep apnea during serial polysomnography, bilevel positive airway pressure therapy was initiated despite the absence of hypoventilation. Nonpolyalanine repeat mutations are associated with severe phenotypes requiring continuous assisted ventilation, Hirschsprung's disease, and neural crest tumors; however, our patient had a relatively milder respiratory phenotype requiring sleep-only assisted ventilation without tracheostomy. Although alveolar hypoventilation is the hallmark of CCHS, our patient lacked hypoventilation. Bilevel positive airway pressure could be considered in some infants with CCHS requiring sleep-only assisted ventilation for tracheostomy avoidance. Our case demonstrates the expanding phenotypic spectrum in CCHS and the importance of formulating an individualized care plan.

CITATION

Fain ME, Raghunandan S, Pencheva B, Leu RM, Kasi AS. Images: atypical presentation of congenital central hypoventilation syndrome in an infant with central and obstructive sleep apnea. J Clin Sleep Med. 2024;20(3):478-481.

Characteristics and outcomes in children with congenital central hypoventilation syndrome on long-term mechanical ventilation in the Netherlands

Congenital central hypoventilation syndrome (CCHS) is a rare condition characterized by central hypoventilation, leading to the majority of patients being dependent on ventilatory support during sleep. This condition is often accompanied by various associated symptoms, due to a PHOX2B gene variant involved in neuronal crest cell migration. This study is the first to review the characteristics and outcomes in children with CCHS on long-term mechanical ventilation in the Netherlands. We performed a retrospective study of all CCHS patients treated in the 4 Centers of Home Mechanical Ventilation of the University Medical Centers in the Netherlands from 2000 till 2022 by collecting information from the electronic medical records, documented during follow-up. We included 31 patients, out of which 27 exhibited a known genetic profile associated with CCHS, while no PHOX2B variant was identified in the remaining patients. Among the 27 patients with known genetic profiles, 10 patients had a non-polyalanine repeat expansion mutation (NPARM), followed by 20/27, 20/25, and 20/26 polyalanine repeat expansion mutations (PARMs) in descending order. The most common presentation involved respiratory failure or apneas during the neonatal period with an inability to wean off ventilation. The majority of patients required ventilatory support during sleep, with four patients experiencing life-threatening events related to this dependency. Daily use of ventilatory support varied among different genetic profiles. All genotypes reported comorbidities, with Hirschsprung's disease and cardiac arrhythmias being the most reported comorbidities. Notably, Hirschprung's disease was exclusively observed in patients with a 20/27 PHOX2B variant.

CONCLUSION

Our study results suggest that in our cohort, the genotype is not easily associated to the phenotype in CCHS. Consistent with these findings and international literature, we recommend a thorough annual evaluation for all patients with CCHS to ensure optimal management and follow-up.

WHAT IS KNOWN

• The majority of CCHS patients are dependent on ventilatory support. • Variants in the PHOX2B gene are responsible for the characteristics of CCHS.

WHAT IS NEW

• This study provides insight into the clinical course and long-term outcomes of CCHS patients in the Netherlands. • In CCHS, the genotype is not easily associated with the phenotype, requiring a thorough life-long follow-up for all patients.

Later Onset Congenital Central Hypoventilation Syndrome

Congenital central hypoventilation syndrome (CCHS) is a rare disorder of the autonomic nervous system involving multiple organ systems, with the hallmark symptom of respiratory failure due to aberrant central control of breathing resulting in hypoxemia and hypercapnia. Later onset CCHS (LOCCHS) is defined as the diagnosis of CCHS in children older than 1 month. Molecular genetic testing for PHOX2B variants has led not only to increased diagnosis of neonates with CCHS but also the increased identification of older children, adolescents, and adults with LOCCHS who may have a milder clinical presentation of this multisystem disease.

Effect of Facemask in Congenital Central Hypoventilation Syndrome

INTRODUCTION

Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder with a mutation in the PHOX2B gene. Patients need ventilatory support by noninvasive ventilation or tracheostomy to treat alveolar hypoventilation. Patients with CCHS have a defect in chemosensitivity signal integration. Recently, due to the COVID-19 pandemic, the entire world has had to get used to wearing medical masks (MM).

OBJECTIVES

The aim of the study was to evaluate the effect of an MM on gas exchange and to determine the role of central and peripheral chemoresponsiveness on the partial pressure of transcutaneous carbon dioxide (PtcCO2) in patients with CCHS wearing an MM.

METHODS

This study was based on the analysis of recordings obtained without and with an MM during hospitalization and was conducted to assess the impact of MM on PtcCO2 and SpO2 recordings with the SenTec Digital Monitor and their relationships with peripheral CO2 chemosensitivity obtained during tidal breathing measurement and with the hypercapnic hyperoxic ventilatory response.

RESULTS

Sixteen patients were included (13 boys) and were 10.2 (7.5; 18.5) years old. The use of an MM had a negative impact on gas exchange in patients with CCHS. The median PtcCO2 increased significantly. Peripheral chemosensitivity correlated with MM-induced PtcCO2 changes (R = -0.72, p = 0.005), but central chemosensitivity (the hypercapnic ventilator response slope) did not (R = -0.22, p = 0.510).

CONCLUSION

The use of an MM had a negative impact on gas exchange in patients with CCHS.

Indications and evidence for domiciliary noninvasive ventilation

INTRODUCTION

Home noninvasive ventilation (HNIV) has expanded globally, with a greater evidence base for its use. HNIV improves multiple patient related outcomes in patients with chronic hypercapnic respiratory failure. Obesity hypoventilation syndrome (OHS) is rapidly taking over as the primary indication for HNIV and COPD patients who overlap with obstructive sleep apnea hypoventilation syndromes (OSAHS) and are increasingly recognized but add to the complexity of HNIV prescribing. Optimal settings vary for differing diseases, with higher inspiratory pressures often required in those with OHS and COPD, yet which settings translate into greatest patient benefit remains unknown.

AREAS COVERED

We cover the evidence base underpinning the common indications for HNIV in COPD, OHS, neuromuscular disease (NMD), and chest wall disease (CWD) and highlight common HNIV modes used.

EXPERT OPINION

Active screening for nocturnal hypoventilation in OHS and COPD may be important to guide earlier ventilation. Further research on which HNIV modalities best improve patient related outcomes and the right time for initiation in different patient phenotypes is rapidly needed. Worldwide, clinical research trials should aim to bridge the gap by reporting on patient-related outcomes and cost effectiveness in real-world populations to best understand the true benefit of HNIV amongst heterogenous patient populations.

Sleep in pediatric neuromuscular disorders

Sleep disordered breathing (SDB) is prevalent among children with neuromuscular disorders (NMD). The combination of respiratory muscle weakness, altered drive, and chest wall distortion due to scoliosis make sleep a stressful state in this population. Symptomatology can range from absent to snoring, nocturnal awakenings, morning headaches, and excessive daytime sleepiness. Sequelae of untreated SDB includes cardiovascular effects, metabolic derangements, and neurocognitive concerns which can be compounded by those innate to the NMD. The clinician should have a low threshold for obtaining polysomnography and recognize the nuances of individual disorders due to disproportionately impacted muscle groups such as hypoventilation in ambulating patients from diaphragm weakness. Non-invasive or invasive ventilation are the mainstay of treatment. In this review we explore the diagnosis and treatment of SDB in children with various NMD.

[Two children with late-onset congenital central hypoventilation syndrome]

Two children with late-onset congenital central hypoventilation syndrome were reported, one of whom was male and had no abnormal manifestations after birth, respiratory failure occurs at the age of 1 year and 6 months. After being hospitalized, he was treated with oxygen inhalation and non-invasive ventilation, but carbon dioxide retention could not be corrected. After one month of tracheal intubation, he was failure to wean from ventilator, so tracheostomy was performed. He needs a ventilator to help breath while sleeping, and can breath autonomously during the day without ventilator. The other case was a female, with no abnormalities after birth. At the age of 11 months, she developed respiratory failure. During sleep, the child needs non-invasive assisted ventilation through a nasal mask, and during the day, she breathed autonomously.Two patients were followed up forever 2 years and their growth and development were normal.

Congenital central hypoventilation syndrome without hypoventilation: is it congenital central hypoventilation syndrome?

Congenital central hypoventilation syndrome (CCHS) is a rare condition caused by pathogenic variants of the PHOX2B gene. There have been case reports describing variable phenotypes and mutations of the PHOX2B gene, not commonly tested for, that may challenge the classic definition of CCHS. We report on 3 family members with a rare heterozygous deletion encompassing the entire PHOX2B gene with variable phenotypes, including sleep-disordered breathing and autonomic nervous system involvement, but an unexpected lack of alveolar hypoventilation, which is usually a defining feature of CCHS. Our cases highlight the dilemmas in making a diagnosis of CCHS and emphasize the need for expanded genetic testing, including for PHOX2B gene deletion. More patients with variable phenotypes of CCHS may be identified through comprehensive genetic testing and warrant surveillance as they are still at risk for high-risk complications of CCHS.

CITATION

Wo LL, Itani R, Keens TG, Marachelian A, Ji J, Perez IA. Congenital central hypoventilation syndrome without hypoventilation: is it congenital central hypoventilation syndrome? J Clin Sleep Med. 2023;19(6):1161-1164.

Rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation (ROHHAD): a collaborative review of the current understanding

PURPOSE

To provide an overview of the discovery, presentation, and management of Rapid-onset Obesity with Hypothalamic dysfunction, Hypoventilation, and Autonomic Dysregulation (ROHHAD). To discuss a search for causative etiology spanning multiple disciplines and continents.

METHODS

The literature (1965-2022) on the diagnosis, management, pathophysiology, and potential etiology of ROHHAD was methodically reviewed. The experience of several academic centers with expertise in ROHHAD is presented, along with a detailed discussion of scientific discovery in the search for a cause.

RESULTS

ROHHAD is an ultra-rare syndrome with fewer than 200 known cases. Although variations occur, the acronym ROHHAD is intended to alert physicians to the usual sequence or unfolding of the phenotypic presentation, including the full phenotype. Nearly 60 years after its first description, more is known about the pathophysiology of ROHHAD, but the etiology remains enigmatic. The search for a genetic mutation common to patients with ROHHAD has not, to date, demonstrated a disease-defining gene. Similarly, a search for the autoimmune basis of ROHHAD has not resulted in a definitive answer. This review summarizes current knowledge and potential future directions.

CONCLUSION

ROHHAD is a poorly understood, complex, and potentially devastating disorder. The search for its cause intertwines with the search for causes of obesity and autonomic dysregulation. The care for the patient with ROHHAD necessitates collaborative international efforts to advance our knowledge and, thereby, treatment, to decrease the disease burden and eventually to stop, and/or reverse the unfolding of the phenotype.

Permissive hypoventilation equally effective to maintain oxygenation as positive pressure ventilation after porcine class III hemorrhage and whole blood resuscitation

BACKGROUND

Prehospital anesthesia may lead to circulatory collapse after severe hemorrhage. It is possible that permissive hypoventilation, refraining from tracheal intubation and accepting spontaneous ventilation, decreases this risk, but it is not known if oxygen delivery can be maintained. We investigated the feasibility of permissive hypoventilation after class III hemorrhage and whole blood resuscitation in three prehospital phases: 15 min on-scene, 30 min whole blood resuscitation, and 45 min after.

STUDY DESIGN AND METHODS

19 crossbred swine, mean weight 58.5 kg, were anesthetized with ketamine/midazolam and hemorrhaged to a mean (SD) 1298 (220) mL (33%) and randomized to permissive hypoventilation (n = 9) or positive pressure ventilation with FiO2 21% (n = 10).

RESULTS

In permissive hypoventilation versus positive pressure ventilation, indexed oxygen delivery (DO2 I) decreased to mean (SD) 4.73 (1.06) versus 3.70 (1.13) mL min-1  kg-1 after hemorrhage and increased to 8.62 (2.09) versus 6.70 (1.56) mL min-1  kg-1 at completion of resuscitation. DO2 I, indexed oxygen consumption (VO2 I), and arterial saturation (SaO2 ) did not differ. Permissive hypoventilation increased the respiratory rate and increased pCO2 . Positive pressure ventilation did not deteriorate circulation. Cardiac index (CI), systolic arterial pressure (SAP), hemoglobin (Hb), and heart rate did not differ.

DISCUSSION

Permissive hypoventilation and positive pressure ventilation were equally effective to maintain oxygen delivery in all phases. A respiratory rate of 40 was feasible, showing no signs of respiratory fatigue for 90 min, indicating that whole blood resuscitation may be prioritized in select patients with severe hemorrhage and spontaneous breathing.

Gavage approach to oxygen supplementation with oxygen therapeutic Ox66™ in a hypoventilation rodent model of respiratory distress

Acute respiratory distress syndrome (ARDS) features pulmonary dysfunction capable of causing life-threatening hypoxaemia. Ventilation and hyperoxic therapies force oxygen through dysfunctional alveoli but risk exacerbating damage. Ox66™ is an ingestible, solid-state oxygen product designed for oxygen supplementation. Eighteen anaesthetized, ventilated rats were subjected to a 40% reduction in tidal volume to produce a hypoventilatory simulation of the hypoxia in ARDS (HV-ARDS). After 60 min, animals were randomized to receive either normal saline (Saline; volume control) or Ox66^™ gavage. Cardiovascular function and blood oximetry/chemistry were measured alongside interstitial oxygenation (P_ISFO₂) of the peripheral spinotrapezius muscle. HV-ARDS reduced mean arterial pressure by ∼20% and P_ISFO₂ by ∼35% for both groups. Ox66^™ gavage treatment at 60 min improved P_ISFO₂ over Saline (p < .0001), restoring baseline values, however, the effect was temporary. A second bolus at 120 min repeated the OX66^™ P_ISFO₂ response, which remained elevated over Saline (p < .01) until study end and was supported by systemic parameters of lactate, P_aO₂, SO₂, and base deficit. Saline remained hypotensive, whereas Ox66^™ became normotensive. Vasoconstriction was observed in the Saline, but not Ox66^™ group. Supplemental oxygenation through Ox66^™ gavage increased peripheral tissue oxygenation, warranting further study for disorders featuring dysfunction of pulmonary perfusion like ARDS.

Singultus, paper-bag ventilation, and hypercapnia

Sir Louis Francis Knuthsen (1869-1957), the physician who painstakingly listed almost all treatments known for obstinate hiccough, ascribes the holding of breath method to Philip Henry Pye-Smith, FRS (1840-1914), consultant at Guy's Hospital in London. In fact, the strategy is much older and was mentioned by greats such as Francis Bacon (1561-1626), Aristoteles (384-322 BC), and Eryximachus (late-fifth century bce). Hypoventilation to reduce central nervous system excitability was used in antiquity as evidenced by Cyriacus' treatment of Artemia, the daughter of Emperor Diocletian (≈ 244-311). She was suffering from (among others) seizures that Cyriacus was apparently controlling by tightening a scarf around her neck, as depicted by Mathias Grünewald (1460-1528) on a wing of the so-called Heller Altar now on display at the Historical Museum, Frankfurt, Germany. In modern times, around 1920, inducing hypercapnia by CO₂ inhalation as therapy for hiccups was suggested and tried by a number of anesthetists, such as Americans Russel Firth Sheldon (1885-1960) and Brian Collins Sword (1889-1956) in Boston; Briton Christopher Langton Hewer (1896-1986) at St. Bartholomew's Hospital in London; Austrian Karl Doppler (1887-1947) in Vienna; and the German/Polish Arthur Dzialoszynski (1893-1977) in Berlin. Although various authors assign the scientific primate to any of them, the first mention of carbon dioxide inhalation as treatment of singultus in the scientific literature is of French origin and was made by Paris pharmacist Henri Bocquillon-Limousin (1856-1917) in his 1892 Formulaire des médicaments nouveaux et des médications nouvelles.

[Diaphragm pacemaker: alternative for long-term ventilatory support; 5 years later]

Currently, more than 3000 patients in the Netherlands receive long-term ventilatory support. In the majority of patients, long-term ventilatory support leads to increased survival without any complications. Diaphragm pacing with an external pacemaker (diaphragm pacing system, DPS) seems an attractive alternative for long-term ventilatory support by mask or tracheostomy. Scientific research has since shown that DPS is effective in patients with high cervical paraplegia. In addition, patients with congenital central hypoventilation syndrome are also eligible for DPS. Patients with diaphragm paralysis are a new group of patients who may be eligible for DPS. Two European studies have shown that DPS should not be used in patients with amyotrophic lateral sclerosis. In our experience, patients are no longer completely dependent on a ventilator or may even be able to discontinue using one if the procedure was successful. In the Netherlands, as far as we know, the technique is only used at the University Medical Center Groningen.

Evaluating the evidence: is phrenic nerve stimulation a safe and effective tool for decreasing ventilator dependence in patients with high cervical spinal cord injuries and central hypoventilation?

INTRODUCTION

Case reports, case series and case control studies have looked at the use of phrenic nerve stimulators in the setting of high spinal cord injuries and central hypoventilation syndromes dating back to the 1980s. We evaluated the evidence related to this topic by performing a systematic review of the published literature.

METHODS

Search terms "phrenic nerve stimulation," "phrenic nerve and spinal cord injury," and "phrenic nerve and central hypoventilation" were entered into standard search engines in a systematic fashion. Articles were reviewed by two study authors and graded independently for class of evidence according to published guidelines. The published evidence was reviewed, and the overall body of evidence was evaluated using the grading of recommendations, assesment, development and evaluations (GRADE) criteria Balshem et al. (J Clin Epidemiol 64:401-406, 2011).

RESULTS

Our initial search yielded 420 articles. There were no class I, II, or III studies. There were 18 relevant class IV articles. There were no discrepancies among article ratings (i.e., kappa = 1). A meta-analysis could not be performed due to the low quality of the available evidence. The overall quality of the body of evidence was evaluated using GRADE criteria and fell within the "very poor" category.

CONCLUSION

The quality of the published literature for phrenic nerve stimulation is poor. Our review of the literature suggests that phrenic nerve stimulation is a safe and effective option for decreasing ventilator dependence in high spinal cord injuries and central hypoventilation; however, we are left with critical questions that provide crucial directions for future studies.

Long-standing meningomyelocele can be a predictor of difficult airway and postoperative hypoventilation: challenge to the anaesthesiologist

A 15-year-old female patient presented with severe pain in the abdomen and obstructive uropathy. She underwent Yang-Monti ileovesicostomy under general anaesthesia. She is a known case of long-standing meningomyelocele (MMC) and presented with its potential complications such as difficult airway and restrictive lung disease. We describe the successful anaesthetic management of a case of anticipated difficult airway and postoperative hypoventilation as a sequel of kyphosis due to MMC. Her airway was secured with fibre optic-guided intubation in a semirecumbent position. Postoperative hypoventilation, hypercarbia and respiratory acidosis were managed conservatively, followed by staged weaning in the intensive care unit. Obstruction of the catheterisable continent channel of the neurogenic bladder itself may present with uropathy and urosepsis, which were also taken care of preoperatively.

[Congenital central hypoventilation syndrome diagnosed in a two-year-old girl]

Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder characterized by inadequate response to hypoxia and hypercapnia and life-threatening alveolar hypoventilation most pronounced during sleep. It is associated with other disorders of neural crest origin and of autonomic dysfunction. Usually the diagnosis is made in the neonatal period. We describe a case where a two-year-old girl had respiratory failure during the first week of her life and CCHS was suspected, but followed by spontaneous recovery and a two-year period without symptoms.

The use of equine surfactant and positive pressure ventilation to treat a premature alpaca cria with severe hypoventilation and hypercapnia

A 5-hour-old, premature alpaca cria was presented with failure to nurse, weakness, hypoglycemia, hypercapnia, and respiratory distress. The cria was treated with 3 doses of fresh, crude equine surfactant, positive pressure ventilation, and supplemental intranasal oxygen. Recovery to discharge was uneventful, and the cria regained apparently normal respiratory function. Three years after hospital discharge, the alpaca was a healthy adult.

Thoracoscopic placement of phrenic nerve pacers for diaphragm pacing in congenital central hypoventilation syndrome

PURPOSE

Congenital central hypoventilation syndrome (CCHS), or Ondine's curse, is a rare disorder affecting central respiratory drive. Patients with this disorder fail to ventilate adequately and require lifelong ventilatory support. Diaphragm pacing is a form of ventilatory support which can improve mobility and/or remove the tracheostomy from CCHS patients. Little is known about complications and long-term outcomes of this procedure.

METHODS

A single-center retrospective review was performed of CCHS patients undergoing placement of phrenic nerve electrodes for diaphragm pacing between 2000 and 2012. Data abstracted from the medical record included operation duration, ventilation method, number of trocars required, and postoperative and pacing outcomes.

RESULTS

Charts of eighteen patients were reviewed. Mean surgical time was 3.3±0.7 hours. In all cases except one, three trocars were utilized for each hemithorax, with no conversions to open procedures. Five patients (27.8%) experienced postoperative complications. The mean ICU stay was 4.3±0.5 days, and the mean hospital stay is 5.7±0.3days. Eleven patients (61.1%) achieved their daily goal pacing times within the follow-up period.

CONCLUSIONS

Thoracoscopic placement of phrenic nerve electrodes for diaphragmatic pacing is a safe and effective treatment modality for CCHS. Observed complications were temporary, and the majority of patients were able to achieve pacing goals.

Nocturnal mechanical ventilation for chronic hypoventilation in patients with neuromuscular and chest wall disorders

BACKGROUND

Chronic alveolar hypoventilation is a common complication of many neuromuscular and chest wall disorders. Long-term nocturnal mechanical ventilation is commonly used to treat it. This is a 2014 update of a review first published in 2000 and previously updated in 2007.

OBJECTIVES

To examine the effects on mortality of nocturnal mechanical ventilation in people with neuromuscular or chest wall disorders. Subsidiary endpoints were to examine the effects of respiratory assistance on improvement of chronic hypoventilation, sleep quality, hospital admissions and quality of life.

SEARCH METHODS

We searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE and EMBASE on 10 June 2014. We contacted authors of identified trials and other experts in the field.

SELECTION CRITERIA

We searched for quasi-randomised or randomised controlled trials of participants of all ages with neuromuscular or chest wall disorder-related stable chronic hypoventilation of all degrees of severity, receiving any type and any mode of long-term nocturnal mechanical ventilation. The primary outcome measure was one-year mortality and secondary outcomes were unplanned hospital admission, short-term and long-term reversal of hypoventilation-related clinical symptoms and daytime hypercapnia, improvement of lung function and sleep breathing disorders.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodology to select studies, extract data and assess the risk of bias in included studies.

MAIN RESULTS

The 10 eligible trials included a total of 173 participants. Roughly half of the trials were at low risk of selection, attrition or reporting bias, and almost all were at high risk of performance and detection bias. Four trials reported mortality data in the long term. The pooled risk ratio (RR) of dying was 0.62 (95% confidence interval (CI) 0.42 to 0.91, P value = 0.01) in favour of nocturnal mechanical ventilation compared to spontaneous breathing. There was considerable and significant heterogeneity between the trials, possibly related to differences between the study populations. Information on unplanned hospitalisation was available from two studies. The corresponding pooled RR was 0.25 (95% CI 0.08 to 0.82, P value = 0.02) in favour of nocturnal mechanical ventilation. For most of the outcome measures there was no significant long-term difference between nocturnal mechanical ventilation and no ventilation. Most of the secondary outcomes were not assessed in the eligible trials. Three out of the 10 trials, accounting for 39 participants, two with a cross-over design and one with two parallel groups, compared volume- and pressure-cycled non-invasive mechanical ventilation in the short term. From the only trial (16 participants) on parallel groups, there was no difference in mortality (one death in each arm) between volume- and pressure-cycled mechanical ventilation. Data from the two cross-over trials suggested that compared with pressure-cycled ventilation, volume-cycled ventilation was associated with less sleep time spent with an arterial oxygen saturation below 90% (mean difference (MD) 6.83 minutes, 95% CI 4.68 to 8.98, P value = 0.00001) and a lower apnoea-hypopnoea (per sleep hour) index (MD -0.65, 95% CI -0.84 to -0.46, P value = 0.00001). We found no study that compared invasive and non-invasive mechanical ventilation or intermittent positive pressure versus negative pressure ventilation.

AUTHORS' CONCLUSIONS

Current evidence about the therapeutic benefit of mechanical ventilation is of very low quality, but is consistent, suggesting alleviation of the symptoms of chronic hypoventilation in the short term. In four small studies, survival was prolonged and unplanned hospitalisation was reduced, mainly in participants with motor neuron diseases. With the exception of motor neuron disease and Duchenne muscular dystrophy, for which the natural history supports the survival benefit of mechanical ventilation against no ventilation, further larger randomised trials should assess the long-term benefit of different types and modes of nocturnal mechanical ventilation on quality of life, morbidity and mortality, and its cost-benefit ratio in neuromuscular and chest wall diseases.

Evaluation of the impact of implementing the emergency medical services traumatic brain injury guidelines in Arizona: the Excellence in Prehospital Injury Care (EPIC) study methodology

Traumatic brain injury (TBI) exacts a great toll on society. Fortunately, there is growing evidence that the management of TBI in the early minutes after injury may significantly reduce morbidity and mortality. In response, evidence-based prehospital and in-hospital TBI treatment guidelines have been established by authoritative bodies. However, no large studies have yet evaluated the effectiveness of implementing these guidelines in the prehospital setting. This article describes the background, design, implementation, emergency medical services (EMS) treatment protocols, and statistical analysis of a prospective, controlled (before/after), statewide study designed to evaluate the effect of implementing the EMS TBI guidelines-the Excellence in Prehospital Injury Care (EPIC) study (NIH/NINDS R01NS071049, "EPIC"; and 3R01NS071049-S1, "EPIC4Kids"). The specific aim of the study is to test the hypothesis that statewide implementation of the international adult and pediatric EMS TBI guidelines will significantly reduce mortality and improve nonmortality outcomes in patients with moderate or severe TBI. Furthermore, it will specifically evaluate the effect of guideline implementation on outcomes in the subgroup of patients who are intubated in the field. Over the course of the entire study (~9 years), it is estimated that approximately 25,000 patients will be enrolled.

[Congenital central hypoventilation syndrome: paradigm shifts and future prospects]

Congenital central hypoventilation syndrome (CCHS) is characterized by a failure of the automatic control of breathing during sleep, and is caused by the dominant PHOX2B mutation. PHOX2B encodes a highly conserved homeobox transcription factor with two short polyalanine tracts. More than 90% of patients carry polyalanine expansion mutations (PARM) in the polyalanine tract of 20 residues and less than 10% of the patients have missense, nonsense, or frameshift mutations(non-PARM). Approximately 25% of the patients with PARM inherited the mutation from asymptomatic parents with somatic mosaicism or few affected parents. Molecular analysis can provide the definite diagnosis and clinically useful information. Model mouse experiments and MRI study of the patients will contribute to understanding the pathogenesis and development of new treatment strategy.

[Non-invasive mechanical ventilation in a child with central hypoventilation syndrome: one year follow-up]

OBJECTIVE

To investigate clinical features and therapeutic methods of late-onset central hypoventilation syndrome.

METHOD

A nine-year old boy was trachea-intubated and mechanically ventilated because of pneumonia, respiratory and heart failure and pulmonary hypertension. It was found that hard to extubate the patient as he was breathing normally while awake but had shallow breathing, oxygen desaturation and CO2 retention when falling asleep. Nocturnal polysomnography together with transcutaneous CO2 supported the diagnosis of central hypoventilation. The final diagnosis was late-onset congenital central hypoventilation syndrome as the patient gained weight rapidly since 3 years of age and the brain magnetic resonance imaging (MRI) and genetic screening were unremarkable.

RESULT

The patient was treated with bi-level positive air pressure ventilation via nasal mask which showed good oxygen saturation and CO2 dropped down. The follow up study done one year later showed normal brain MRI, relief of pulmonary hypertension and better CO2 level in both awaken and sleeping status.

CONCLUSION

The late-onset congenital central hypoventilation syndrome in this case had onset of symptoms at 2 years of age, he had normal breathing while he was awake but had oxygen desaturation and CO2 retention during sleep, therefore, respiratory support is required in severe cases. Mechanical ventilation via tracheotomy and non-invasive ventilation via mask are the major choice.

Diaphragm pacers as a treatment for congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome is a rare syndrome present from birth, and is defined as the failure of automatic control of breathing. All patients with congenital central hypoventilation syndrome require life-long ventilatory support during sleep, although approximately a third of patients require ventilatory support 24 h per day. Diaphragm pacers offer a modality of ventilatory support that affords congenital central hypoventilation syndrome patients with maximal mobility for full-time ventilatory patients, and they may allow for a more normal lifestyle in the appropriate patient. They may permit tracheostomy decannulation in those requiring only support during sleep. Diaphragm pacing entails surgical placement of an electrode onto the phrenic nerve, connected to a subcutaneous receiver. There is an external battery-operated transmitter and antenna placed on the skin over the receiver. The transmitter emits energy, similar to radio transmission, which is converted into an electrical current by the receiver. This stimulates the phrenic nerve resulting in a diaphragmatic contraction. Settings on the transmitter include respiratory rate and electrical voltage, and are adjusted to give enough tidal volume to allow for adequate oxygenation and ventilation. Therefore, diaphragm pacing is an attractive alternative mode of mechanically assisted ventilation for many patients with congenital central hypoventilation syndrome.

[Congenital central hypoventilation syndrome, report of three cases]

OBJECTIVE

To evaluate clinical characteristics and PHOX2B gene mutations in congenital central hypoventilation syndrome (CCHS) and to facilitate the early diagnosis and management of CCHS and reduce the misdiagnosis.

METHOD

Clinical data of 3 infants with CCHS who had recurrent respiratory failure episodes and dependent on mechanical ventilation support in 3 from March 2008 to April 2012 were analyzed, and blood gas analysis was performed respectively in the awaken and sleeping status. Gene sequencing was used for detection of PHOX2B gene mutation.

RESULT

All the three patients had adequate ventilation during awaken time, but they presented with abnormal frequency and shallow breathing associated with alveolar hypoventilation after falling asleep. Blood gas analysis showed hypercapnia and CO2 partial pressure was consistently over 60 mm Hg (1 mm Hg = 0.133 kPa) after falling asleep, which is in accordance with the clinical features of CCHS. The PHOX2B gene sequencing showed that 6 GCN repeats were inserted at exon3 of PHOX2B in case 1, at same position, 5 GCN repeats were inserted in case 2 and 3.

CONCLUSION

Normal ventilation in awaken status while shallow slow breathing accompanied with hypercapnia in sleep are the main clinical characteristics of CCHS, which requires mechanical ventilation. Acquired mutation in exon 3 of PHOX2B gene encoding repeated GCN sequence seems to be the molecular etiology of these three patients.

Management of pulmonary complications in neuromuscular disease

Restrictive lung disease occurs commonly in patients with neuromuscular disease. The earliest sign of respiratory compromise in the patient with neuromuscular disease is nocturnal hypoventilation, which progresses over time to include daytime hypoventilation and eventually the need for full-time mechanical ventilation. Pulmonary function testing should be done during regular follow-up visits to identify the need for assistive respiratory equipment and initiate early noninvasive ventilation. Initiation of noninvasive ventilation can improve quality of life and prolong survival in patients with neuromuscular disease.

A new device for the care of Congenital Central Hypoventilation Syndrome patients during sleep

Congenital Central Hypoventilation Syndrome (CCHS) is a genetic disease that causes an autonomous nervous system dysregulation. Patients are unable to have a correct ventilation, especially during sleep, facing risk of death. Therefore, most of them are mechanically ventilated during night and their blood oxygenation is monitored, while a supervisor keeps watch over them. If low oxygen levels are detected by the pulse-oximeter, an alarm fires; the supervisor deals with the situation and, if there is neither a technical problem nor a false alarm, wakes the subject, as CCHS patients usually recover from hypoxia when roused from sleep. During a single night multiple alarms may occur, causing fractioned sleep for the subject and a lasting state of anxiety for supervisors.

[Possibilities of bi-level positive pressure ventilation in chronic hypoventilation]

During the last decade, noninvasive bi-level positive pressure ventilation has enabled respiratory support in inpatient wards and at home. In many cases, a bi-level airway pressure ventilator can be used to avoid artificial airway and respirator therapy, and may shorten hospital stay and save costs. The treatment alleviates the patient's dyspnea and fatigue, whereby the quality of life improves, and in certain situations also the life span increases. The implementation of bi-level positive pressure ventilation by the physician requires knowledge of the basics of respiratory physiology and familiarization with the bi-level airway pressure ventilator.

Average volume-assured pressure support in a 16-year-old girl with congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) is an uncommon disorder characterized by the absence of adequate autonomic control of respiration, which results in alveolar hypoventilation and decreased sensitivity to hypercarbia and hypoxemia, especially during sleep. Patients with CCHS need lifelong ventilatory support. The treatment options for CCHS include intermittent positive pressure ventilation administered via tracheostomy, noninvasive positive pressure ventilation, negative-pressure ventilation by body chamber or cuirass, and phrenic nerve pacing. However, it may be necessary to alter the mode of ventilation according to age, psychosocial reasons, complications of therapy, and emergence of new modes of ventilation. We present a case of a 16-year-old girl with CCHS who was mechanically ventilated via tracheostomy for 16 years and was successfully transitioned to a new modality of noninvasive ventilation (average volume-assured pressure support [AVAPS]) that automatically adjusts the pressure support level in order to provide a consistent tidal volume.

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.

A case of late-onset central hypoventilation syndrome with hypothalamic dysfunction: through a new phenotype

Congenital central hypoventilation syndrome (CCHS) is a rare disorder with uncertain nosology that usually presents early in life. The syndrome is characterized by ventilatory response impairment to carbon dioxide and may result in respiratory failure at birth. Recent reports have identified a similar clinical presentation beyond infancy called late-onset central hypoventilation syndrome (LO-CHS) as a disease continuum of CCHS with similar and overlapping pathophysiology. However, some have proposed that the syndrome accompanied by hypothalamic dysfunction (HD) be classified as a distinct clinical entity, LO-CHS/HD. To the best of our knowledge, the case reported herein is the oldest case of LO-CHS/HD in childhood, at 13 years old. He suffered from recurrent pulmonary edema, acute convulsive seizures, hypersomnia, hyperphagia, obesity, impaired glucose tolerance test, and hypercapnia, diagnosed as LO-CHS/HD, and was successfully treated with nasal bi-level positive airway pressure.

Nocturnal hypoventilation - identifying & treating syndromes

Nocturnal hypoventilation is a common feature of disorders affecting the function of the diaphragm or central respiratory drive mechanisms. The ensuing change in gas exchange is initially confined to rapid eye movement (REM) sleep, but over time buffering of the raised carbon dioxide produces a secondary depression of respiratory drive that will further reduce ventilation not only during sleep but eventually during wakefulness as well. Failure to identify and treat nocturnal hypoventilation results in impairments in daytime function, quality of life and premature mortality. While some simple daytime tests of respiratory function can identify at risk individuals, these cannot predict the nature or severity of any sleep disordered breathing present. Nocturnal monitoring of gas exchange with or without full polysomnography is the only way to comprehensively assess this disorder, especially in the early stages of its evolution. Non invasive ventilation used during sleep is the most appropriate approach to reverse the consequences of nocturnal hypoventilation, although continuous positive airway pressure (CPAP) may be effective in those individuals where a significant degree of upper airway obstruction is present. When appropriately selected patients use therapy on a regular basis, significant improvements in quality of life, exercise capacity and survival can be achieved, irrespective of the underlying disease process.

Phrenic nerve stimulation for diaphragmatic pacing in a patient with high cervical spinal cord injury

BACKGROUND

Phrenic nerve stimulation is a therapeutic option for patients with central hypoventilation syndrome due to brain stem and high cervical spinal cord dysfunction.

CASE REPORT

A 28-year-old woman with high cervical spinal cord injury at the level of C2 had chronic central hypoventilation syndrome, requiring long-term use of a home ventilator Preoperative end tidal CO2 and tidal volume during spontaneous breathing indicated hypoventilation syndrome. Bilateral phrenic nerve stimulation for diaphragmatic pacing was performed with spinal cord stimulators used for chronic pain. The end tidal CO2 pressure (ETCO2), tidal volume, and spontaneous breathing time have improved up to 29 months of postoperative follow-up period.

CONCLUSION

Phrenic nerve stimulation for diaphragmatic pacing can reduce all-time requirement of ventilatory support in patients with high cervical spinal cord injury.

Central hypoventilation with PHOX2B expansion mutation presenting in adulthood

Congenital central hypoventilation syndrome most commonly presents in neonates with sleep related hypoventilation; late onset cases have occurred up to the age of 10 years. It is associated with mutations in the PHOX2B gene, encoding a transcription factor involved in autonomic nervous system development. The case history is described of an adult who presented with chronic respiratory failure due to PHOX2B mutation-associated central hypoventilation and an impaired response to hypercapnia.

Nocturnal mechanical ventilation for chronic hypoventilation in patients with neuromuscular and chest wall disorders

BACKGROUND

Chronic alveolar hypoventilation is a common complication of many neuromuscular and chest wall disorders. Long-term nocturnal mechanical ventilation is increasingly used to treat it.

OBJECTIVES

To examine the efficacy of nocturnal mechanical ventilation in relieving hypoventilation related symptoms and in prolonging survival in people with neuromuscular or chest wall disorders.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Trials Register, MEDLINE (from January 1966 to June 2006), and EMBASE (from January 1980 to June 2006) for randomised trials and contacted authors of trials and other experts in the field.

SELECTION CRITERIA

We searched for quasi-randomised or randomised controlled trials of participants with neuromuscular or chest wall disorder-related stable chronic hypoventilation of all ages and all degrees of severity, receiving any type and any mode of nocturnal mechanical ventilation. The primary outcome measure was short-term and long-term reversal of hypoventilation related clinical symptoms and secondary outcomes were unplanned hospital admission, one year mortality, short-term and long-term reversal of daytime hypercapnia, improvement of lung function and sleep breathing disorders.

DATA COLLECTION AND ANALYSIS

We identified eight randomised trials.

MAIN RESULTS

The eight eligible trials included a total of 144 participants. The relative risk of 'no improvement of hypoventilation related clinical symptoms' in the short-term following nocturnal mechanical ventilation was available in only one trial with 10 participants and was not significant, 0.09 (95% confidence interval (CI) 0.01 to 1.31). The relative risk of 'no reversal of daytime hypercapnia' in the short-term following nocturnal ventilation was significant and favoured treatment, 0.37 (95% CI 0.20 to 0.65). The weighted mean difference of nocturnal mean oxygen saturation was 5.45% (95% CI 1.47 to 9.44) more improvement in participants treated with nocturnal mechanical ventilation. For most of the outcome measures there was no significant long-term difference between nocturnal mechanical ventilation and no ventilation. However, the estimated risk of death based on three studies was reduced following nocturnal ventilation, 0.62 (95% CI 0.42 to 0.91). There was considerable and significant heterogeneity between the trials possibly related to differences between the study populations. Most of the secondary outcomes were not assessed in the eligible trials. Data from two crossover trials suggested no evidence for a difference in reversal of daytime hypercapnia and sleep study parameters between volume-cycled and pressure-cycled ventilation. No data could be summarised for the comparisons between invasive and non-invasive mechanical ventilation or between intermittent positive pressure and negative pressure ventilation.

AUTHORS' CONCLUSIONS

Current evidence about the therapeutic benefit of mechanical ventilation is weak, but consistent, suggesting alleviation of the symptoms of chronic hypoventilation in the short-term. In three small studies survival was prolonged mainly in participants with motor neuron diseases. With the exception of motor neuron disease, further larger randomised trials are needed to confirm long-term beneficial effects of nocturnal mechanical ventilation on quality of life, morbidity and mortality, to assess its cost-benefit ratio in neuromuscular and chest wall diseases and to compare the different types and modes of ventilation.

Anesthetic implications of undiagnosed late onset central hypoventilation syndrome in a child: from elective tonsillectomy to tracheostomy

Late onset central hypoventilation syndrome is a neurological disorder that can present with postoperative respiratory complications and delayed emergence in children after anesthesia. We present a child who had unanticipated respiratory complications following an elective tonsillectomy who eventually required a tracheostomy and long-term ventilatory support.

Chronic respiratory failure in patients with neuromuscular diseases: diagnosis and treatment

Neuromuscular diseases affect alveolar air exchange and therefore cause chronic respiratory failure. The onset of respiratory failure can be acute, as in traumas, or progressive (slow or rapid), as in amyotrophic lateral sclerosis, muscular dystrophies, diseases of the myoneural junction, etc. Respiratory muscle impairment also affects cough efficiency and, according to the current knowledge regarding the type of treatment available in Brazil to these patients, it can be said that the high rates of morbidity and mortality in these individuals are more often related to the fact that they cough inefficiently rather than to the fact that they ventilate poorly. In this review, with the objective of presenting the options of devices available to support and substitute for natural ventilation in patients with neuromuscular diseases, we have compiled a brief history of the evolution of orthopedic braces and prostheses used to aid respiration since the end of the 19th century. In addition, we highlight the elements that are fundamental to the diagnosis of alveolar hypoventilation and of failure of the protective cough mechanism: taking of a clinical history; determination of peak cough flow; measurement of maximal inspiratory and expiratory pressures; spirometry in two positions (sitting and supine); pulse oximetry; capnography; and polysomnography. Furthermore, the threshold values available in the literature for the use of nocturnal ventilatory support and for the extension of this support through the daytime period are presented. Moreover, the maneuvers used to increase cough efficiency, as well as the proper timing of their introduction, are discussed.

Diaphragm pacing with a spinal cord stimulator: current state and future directions

Diaphragm pacing with electrical stimulation of the phrenic nerve is an established treatment for central hypoventilation syndrome. The device, however, is not readily available. We tested the same spinal cord stimulator we use for pain control in phrenic nerve stimulation. We implanted a spinal cord stimulator (Itrel 3 or X-trel, Medtronic, MN) in 6 patients with chronic hypoventilation because of brainstem or high cervical cord dysfunction. The stimulation electrode was placed along the right phrenic nerve in the neck, and the device was implanted in the anterior chest. We used the cyclic mode, and set the parameters at I second ramp up, 2 seconds on, 3 seconds off. The pulse width and the frequency were set at 150 microseconds and 21 Hz, respectively. The amplitude of the output was adjusted to obtain sufficient tidal volume and to maintain PaCO2 at around 40 mm Hg. During a follow-up period up to four years, stable and sufficient ventilation was observed in all patients without any complications. Although further long follow-up is necessary, diaphragm pacing with the spinal cord stimulator is feasible and effective for the treatment of the central hypoventilation syndrome.

Sleep-related hypoventilation/hypoxemic syndromes

The latest edition of The International Classification of Sleep Disorders: Diagnostic and Coding Manual subsumes a broad range of disorders under the heading "Sleep Related Hypoventilation/Hypoxemic Syndromes." Some are quite common, such as COPD with worsening gas exchange during sleep; while some are exceedingly rare, such as congenital central hypoventilation syndrome. All share the attribute of abnormal gas exchange that worsens, or may only be present, during sleep. The sleep state, the sleeping posture, and the circadian rhythm driving sleep all may affect respiration by altering control of breathing and/or pulmonary mechanics. These changes are largely inconsequential in the normal individual but interact with respiratory, neurologic, or neuromuscular disease to manifest as the sleep-related hypoventilation/hypoxemic syndromes. In addition to optimal treatment of the underlying disorder (when known and when possible), treatment usually involves nocturnal ventilatory support that is now most commonly provided by noninvasive positive pressure ventilation.

Negative pressure ventilation via diaphragmatic pacing: a potential gateway for treating systemic dysfunctions

Programmed diaphragmatic pacing using implanted neuromodulators represents an emerging method for providing pulmonary support using negative pressure ventilation. The implantable, rechargeable, programmable and miniaturized nature of diaphragmatic pacers may obviate many of the management issues associated with noninvasive positive pressure ventilation devices. Closed loop systems may facilitate the implementation of diaphragmatic pacing for the treatment of many indications. They may allow for wider adoption of ventilatory support in central sleep apnea and improve quality of life in diseases of chronic hypoventilation, such as amyotrophic lateral sclerosis. In addition, it might alleviate subclinical hypoventilation--a condition that may affect a significant proportion of the aging population. Diaphragmatic pacing could also reduce sympathetic bias, which may contribute to a wide range of diseases associated with autonomic dysfunction.