Marcus Povitz

Diagnosis of muscle diseases presenting with early respiratory failure.

Here we describe a clinical approach and differential diagnosis for chronic muscle diseases which include early respiratory failure as a prominent feature in their presentation (i.e. respiratory failure whilst still ambulant). These patients typically present to neurology or respiratory medicine out-patient clinics and a distinct differential diagnosis of neuromuscular aetiologies should be considered. Amyotrophic lateral sclerosis and myasthenia gravis are the important non-muscle diseases to consider, but once these have been excluded there remains a challenging differential diagnosis of muscle conditions, which will be the focus of this review. The key points in the diagnosis of these disorders are being aware of relevant symptoms, which are initially caused by nocturnal hypoventilation or diaphragmatic weakness; and identifying other features which direct further investigation. Important muscle diseases to identify, because their diagnosis has disease-specific management implications, include adult-onset Pompe disease, inflammatory myopathy, and sporadic adult-onset nemaline myopathy. Cases which are due to metabolic myopathy or muscular dystrophy are important to diagnose because of their implications for genetic counselling. Myopathy from sarcoidosis and colchicine each has a single reported case with this presentation, but should be considered because they are treatable. Disorders which have recently had their genetic aetiologies identified include hereditary myopathy with early respiratory failure (due to TTN mutations), the FHL1-related syndromes, and myofibrillar myopathy due to BAG3 mutation. Recently described syndromes include oculopharyngodistal muscular dystrophy that awaits genetic characterisation.

Prevalence of Sleep-disordered Breathing in Obese Patients with Chronic Hypoxemia. A Cross-Sectional Study

RATIONALE Hypoxemia in obese patients is likely to be associated with a high prevalence of sleep-disordered breathing. Supplemental oxygen is commonly used to treat chronic hypoxemia but carries some risk in obese individuals due to unrecognized comorbid obstructive sleep apnea (OSA) and obesity hypoventilation syndrome (OHS). OBJECTIVES The first step in the estimation of this risk is to determine the prevalence of OSA and OHS in obese individuals with chronic, awake hypoxemia. METHODS A single-center retrospective cohort study was performed to assess the prevalence and severity of OSA and OHS among obese individuals with hypoxemia. One hundred eighty-four individuals underwent arterial blood gas testing and polysomnography. One hundred fifty-eight of these individuals also had spirometry. MEASUREMENTS AND MAIN RESULTS The prevalence of OSA was 80%, and the prevalence of OHS was 51%. Chronic obstructive pulmonary disease (COPD) was confirmed by spirometry in 49% of the cohort, and OSA was found in 69% of those individuals. The severity of hypoxemia in this cohort was not statistically related to COPD, OSA, or OHS. CONCLUSIONS OSA and OHS are highly prevalent in obese patients with chronic awake hypoxemia, and OSA frequently coexists with COPD. Evaluation of chronic, awake hypoxemia solely based on arterial blood gas measurements and pulmonary function testing is not sufficient to identify OSA and OHS. Further diagnostic sleep testing should be performed to identify those who could benefit from alternative therapies and to avoid potential harm from treatment with supplemental oxygen alone.

Diagnosis and treatment of obstructive sleep apnea in adults

KEY POINTS Obstructive sleep apnea (OSA) is characterized by recurring episodes of cessation (apnea) or reduction (hypopnea) in airflow during sleep caused by obstruction of the upper airway. In recent population-based studies, the estimated prevalence of moderate to severe sleep-disordered

Treatment of Sleep Disordered Breathing Liberates Obese Hypoxemic Patients from Oxygen

Background Obese hypoxemic patients have a high prevalence of sleep disordered breathing (SDB). It is unclear to what extent treatment of SDB can improve daytime hypoxemia. Methods We performed a retrospective cohort study of obese hypoxemic individuals, all of whom underwent polysomnography, arterial blood gas analysis, and subsequent initiation of positive airway pressure (PAP) therapy for SDB. Patients were followed for one year for change in partial pressure of arterial oxygen and the need for supplemental oxygen. Results One hundred and seventeen patients were treated with nocturnal PAP and had follow-up available. Adherence to PAP was satisfactory in 60%, and was associated with a significant improvement in daytime hypoxemia and hypercapnea; 56% of these patients were able to discontinue supplemental oxygen. Adherence to PAP therapy and the baseline severity of OSA predicted improvement in hypoxemia, but only adherence to PAP therapy predicted liberation from supplemental oxygen. Conclusions The identification and treatment of SDB in obese hypoxemic patients improves daytime hypoxemia. It is important to identify SDB in these patients, since supplemental oxygen can frequently be discontinued following treatment with PAP therapy.

Healthcare Use in Individuals with Obesity and Chronic Hypoxemia Treated for Sleep Disordered Breathing.

STUDY OBJECTIVES To determine if treatment of obstructive sleep apnea (OSA) and obesity hypoventilation syndrome (OHS) among patients with chronic hypoxemia is associated with reduced healthcare utilization. METHODS We performed a retrospective cohort study of 129 obese, hypoxemic patients who underwent polysomnography and were prescribed positive airway pressure (PAP) therapy. During a 2-year follow-up period we examined the associations between adherence to PAP therapy and rates of hospitalization, emergency room (ER) visits, and outpatient visits. RESULTS Severe OSA and OHS were common, as were hypertension, cardiovascular, and pulmonary disease. Forty-nine percent of patients were adherent with PAP therapy. Compared to patients who were not adherent to PAP therapy, adherent patients had significantly lower rates of all-cause hospitalization (incident rate ratio [IRR]:0.55, 95% CI 0.33, 0.93) after adjustment for age, sex and hospitalisation rates prior to treatment. Adjustment for additional comorbidities attenuated this association (IRR: 0.61, 95% CI 0.35, 1.06). Adherence with PAP therapy was associated with lower odds of frequent hospitalization (odds ratio 0.23, 95% CI 0.07, 0.73). There were no significant differences in the rates of ER or outpatient visits between adherent and non-adherent patients. CONCLUSIONS Adherence with PAP treatment in patients with chronic hypoxemia and chronic medical disorders is associated with reduced rates of hospitalization, which has significant benefit both for patients and the healthcare system.

Home Mechanical Ventilation: A 12-Year Population-Based Retrospective Cohort Study

BACKGROUND: Increasing numbers of individuals are being initiated on home mechanical ventilation, including noninvasive (bi-level) and invasive mechanical ventilation delivered via tracheostomy due to chronic respiratory failure to enable symptom management and promote quality of life. Given the high care needs of these individuals, a better understanding of the indications for home mechanical ventilation, and health-care utilization is needed. METHODS: We performed a retrospective cohort study using provincial health administrative data from Ontario, Canada (population ∼13,000,000). Home mechanical ventilation users were characterized using health administrative data to determine the indications for home mechanical ventilation, the need for acute care at the time of ventilation approval, and their health service use and mortality rates following approval. RESULTS: The annual incidence of home mechanical ventilation approval rose from 1.8/100,000 in 2000 to 5.0/100,000 in 2012, or an annual increase of approximately 0.3/100,000 persons/y. The leading indications were neuromuscular disease, thoracic restriction, and COPD. The indication for the remainder could not be determined due to limitations of the administrative databases. Of the 4,670 individuals, 23.0% commenced home mechanical ventilation following an acute care hospitalization. Among individuals who survived at least 1 y, fewer required hospitalization in the year that followed home mechanical ventilation approval (29.9% vs 39.8%) as compared with the year prior. CONCLUSIONS: Utilization of home mechanical ventilation is increasing in Ontario, Canada, and further study is needed to clarify the factors contributing to this and to further optimize utilization of health-care resources.

Profile of CPAP treated patients in Ontario, Canada, 2006–2013: a population-based cohort study

RATIONALE Many studies have demonstrated the benefits of treating obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP). However, both recognition of OSA and acceptance of treatment are suboptimal. Current data on CPAP initiation at a population level is lacking. OBJECTIVES The objectives were to determine the rate of CPAP initiations in Ontario, Canada (population ∼13,000,000), and to profile these individuals over time. METHODS We conducted a population based cohort study between 2006 and 2013. All adults who initiated CPAP for OSA were included. Patient characteristics, comorbidities and health care utilization at the time of CPAP initiation were derived from provincial health administrative data. Changes in patient characteristics over time were assessed. RESULTS Over eight years, 216,514 individuals initiated CPAP therapy in comparison to 802,188 individuals who underwent diagnostic polysomnography (PSG) during that time. The rate of new CPAP initiations increased from 18.6/10,000 in 2006 to 28.7/10,000 in 2008 and then plateaued with an annual increase of less than 1/10,000 from 2008 to 2013. More women and middle aged (50+) individuals initiated CPAP as did more low income Ontarians. Comorbidities were common and the frequency of congestive heart failure, chronic kidney disease, and cancer increased during the study period. CONCLUSIONS Over an eight year period CPAP initiation appears to have plateaued in spite of increasing PSG testing; however, those receiving treatment with CPAP are increasingly complex and a greater proportion are women.

Addressing challenges with current therapies for obstructive sleep apnea

We read with interest the responses to our recent review of the diagnosis and treatment of obstructive sleep apnea (OSA).[1][1] We agree that challenges with current therapies for OSA necessitate the study of newer and personalized treatments to improve clinical outcomes, treatment adherence and

Patterns of Non-Invasive Ventilation in Amyotrophic Lateral Sclerosis

BACKGROUND Non-invasive ventilation (NIV) improves quality of life and survival in patients with amyotrophic lateral sclerosis (ALS) and respiratory symptoms. Little is known about the patterns of NIV use over time and the impact of NIV on end-of-life decision-making in ALS. OBJECTIVE This study assessed the pattern of NIV use over the course of the disease and the timing of end-of-life discussions in people living with ALS. METHOD A retrospective single-center cohort study was performed at London Health Sciences Centre. Daily NIV duration of use was evaluated at 3-month intervals. The timing of diagnosis, NIV initiation, discussions relating to do-not-attempt-resuscitation (DNAR) and death were examined. RESULTS In total, 48 patients were included in the analysis. Duration of NIV use increased over time, and tolerance to NIV was observed to be better than expected in patients with bulbar-onset ALS. There was a high degree of variability in the timing of end-of-life discussions in patients with ALS (356±451 days from diagnosis). In this cohort, there was a strong association between the timing of discussions regarding code status and establishment of a DNAR order (r2=0.93). CONCLUSION This retrospective cohort study suggests that the use of NIV in ALS increases over time and that there remains a great deal of variability in the timing of end-of-life discussions in people living with ALS. Future prospective studies exploring the use NIV over the disease trajectory and how NIV affects end-of-life decision-making in people with ALS are needed.

Testing and treatment for obstructive sleep apnea in Canada: funding models must change

[See related article at [www.cmaj.ca/lookup/doi/10.1503/cmaj.170296][2]][2] KEY POINTS The Public Health Agency of Canada has estimated that a quarter of adult Canadians are at risk for obstructive sleep apnea (OSA).[1][2] Despite a large potential disease burden, insufficient public funding for