Association between low sniff nasal-inspiratory pressure (SNIP) and sleep disordered breathing in amyotrophic lateral sclerosis: Preliminary results

Respiratory Management of Patients With Neuromuscular Weakness: An American College of Chest Physicians Clinical Practice Guideline and Expert Panel Report

BACKGROUND

Respiratory failure is a significant concern in neuromuscular diseases (NMDs). This CHEST guideline examines the literature on the respiratory management of patients with NMD to provide evidence-based recommendations.

STUDY DESIGN AND METHODS

An expert panel conducted a systematic review addressing the respiratory management of NMD and applied the Grading of Recommendations, Assessment, Development, and Evaluations approach for assessing the certainty of the evidence and formulating and grading recommendations. A modified Delphi technique was used to reach a consensus on the recommendations.

RESULTS

Based on 128 studies, the panel generated 15 graded recommendations, one good practice statement, and one consensus-based statement.

INTERPRETATION

Evidence of best practices for respiratory management in NMD is limited and is based primarily on observational data in amyotrophic lateral sclerosis. The panel found that pulmonary function testing every 6 months may be beneficial and may be used to initiate noninvasive ventilation (NIV) when clinically indicated. An individualized approach to NIV settings may benefit patients with chronic respiratory failure and sleep-disordered breathing related to NMD. When resources allow, polysomnography or overnight oximetry can help to guide the initiation of NIV. The panel provided guidelines for mouthpiece ventilation, transition to home mechanical ventilation, salivary secretion management, and airway clearance therapies. The guideline panel emphasizes that NMD pathologic characteristics represent a diverse group of disorders with differing rates of decline in lung function. The clinician's role is to add evaluation at the bedside to shared decision-making with patients and families, including respect for patient preferences and treatment goals, considerations of quality of life, and appropriate use of available resources in decision-making.

Home-monitoring of vital capacity in people with a motor neuron disease

Background

Home-monitoring of spirometry has the potential to improve care for patients with a motor neuron disease (MND) by enabling early detection of respiratory dysfunction and reducing travel burden. Our aim was to evaluate the validity and feasibility of home-monitoring vital capacity (VC) in patients with MND.

Methods

We included 33 patients with amyotrophic lateral sclerosis, progressive muscular atrophy or primary lateral sclerosis who completed a 12-week home-monitoring protocol, consisting of 4-weekly unsupervised home assessments of VC and a functional rating scale. At baseline, during a home visit, patients/caregivers were trained in performing a VC test, and the investigator performed a supervised VC test, which was repeated at final follow-up during a second home visit. Validity of the unsupervised VC tests was evaluated by the differences between supervised and unsupervised VC tests, and through Bland–Altman 95% limits-of-agreement. Feasibility was assessed by means of a survey of user-experiences.

Results

The 95% limits-of-agreement were [− 14.3; 11.7] %predicted VC, and 88% of unsupervised VC tests fell within 10%predicted of supervised VC. 88% of patients experienced VC testing as easy and not burdensome, however, 15% patients did not think their VC test was performed as well as in the clinic. 94% of patients would like home-monitoring of VC in MND care.

Discussion

Unsupervised VC testing at home, with prior face-to-face training, is a valid and time-efficient method for the remote monitoring of respiratory function, and well-accepted by patients with MND and their caregivers.

Motor neuron, peripheral nerve, and neuromuscular junction disorders

In amyotrophic lateral sclerosis (ALS), Guillain-Barré syndrome (GBS), and neuromuscular junction disorders, three mechanisms may lead, singly or together, to respiratory emergencies and increase the disease burden and mortality: (i) reduced strength of diaphragm and accessory muscles; (ii) oropharyngeal dysfunction with possible aspiration of saliva/bronchial secretions/drink/food; and (iii) inefficient cough due to weakness of abdominal muscles. Breathing deficits may occur at onset or more often along the chronic course of the disease. Symptoms and signs are dyspnea on minor exertion, orthopnea, nocturnal awakenings, excessive daytime sleepiness, fatigue, morning headache, poor concentration, and difficulty in clearing bronchial secretions. The "20/30/40 rule" has been proposed to early identify GBS patients at risk for respiratory failure. The mechanical in-exsufflator is a device that assists ALS patients in clearing bronchial secretions. Noninvasive ventilation is a safe and helpful support, especially in ALS, but has some contraindications. Myasthenic crisis is a clinical challenge and is associated with substantial morbidity including prolonged mechanical ventilation and 5%-12% mortality. Emergency room physicians and consultant pulmonologists and neurologists must know such respiratory risks, be able to recognize early signs, and treat properly.

Sleep‐based therapy: A new treatment for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a worldwide problem with no effective treatment. Patients usually die of respiratory failure. The basic pathological process of ALS is the degeneration and necrosis of motor neurons. Neuroglial cell dysfunction is considered closely related to the development of ALS. Sleep plays an important role in repairing the nervous system, and sleep disorders can worsen ALS. Herein, we review the pathogenesis of ALS and the neuroprotective mechanism of sleep‐based therapy. Sleep‐based therapy could be a potential strategy to treat ALS.

Reduction of Sniff Nasal Inspiratory Pressure (SNIP) as an Early Indicator of the Need of Enteral Nutrition in Patients with Amyotrophic Lateral Sclerosis

Percutaneous endoscopic gastrostomy (PEG) is the standard procedure for feeding severely dysphagic patients with amyotrophic lateral sclerosis (ALS). It is associated with prolonged survival and improvement in quality of life. Nasal inspiratory pressure during a sniff (SNIP) is a respiratory test used extensively in ALS for the assessment of inspiratory muscle strength. In this study, we aimed to investigate the role of SNIP at baseline to predict PEG placement in ALS. Data from a clinical incident cohort of 179 ALS cases attending the multidisciplinary ALS unit of the University of Bari between April 2006 and December 2012 were retrospectively analysed. At baseline, patients underwent detailed neurological, nutritional and respiratory assessments, including measurements of SNIP and forced vital capacity (FVC). Patients were therefore followed up approximately every three to six months until they were able to attend the centre. The censoring date for the survival analysis was 15 April 2014, with PEG placement as the main outcome. Cox proportional hazard regression models were used to examine the association between SNIP and PEG placement, adjusted for possible confounders. During the follow-up period, 75 participants (42%) received PEG implant. PEG placement was more frequent (57% vs. 31%; p = 0.001) and earlier (after 11.6 ± 14.0 months from the first visit, vs. 23.3 ± 15.5 months; p < 0.0001) in the group of patients with baseline SNIP ≤ 40 cm H₂O. Baseline SNIP was a predictor of PEG placement even after correction for multiple potential confounders (HR 0.98; 95% CI: 0.96–0.99; p = 0.02). To conclude, the present study showed that SNIP at baseline is an early indicator of disease progression and therefore of the need for enteral nutrition in ALS.

Measuring vital capacity in amyotrophic lateral sclerosis: Effects of interfaces and reproducibility

BACKGROUND

Deterioration of vital capacity (VC) in amyotrophic lateral sclerosis (ALS) signifies disease progression and indicates need for non-invasive ventilation. Weak facial muscles consequent to ALS, with resulting poor mouth seal, may interfere with the accuracy of VC measurements.

OBJECTIVES

To determine whether different interfaces affect VC measurements in ALS patients and whether the interface yielding the largest VC produces an even higher VC when re-measured after one week (learning effect). To explore the relationship between optimal interface VC and sniff nasal pressure (SNIP), a measurement of global inspiratory muscle strength.

METHODS

Thirty-five patients (17 bulbar and 18 spinal ALS) were studied. Three interfaces (rigid-cylindrical, flanged, oronasal mask) were tested. One week after the first visit, VC was recorded using the optimal interface. SNIP recordings were also obtained.

RESULTS

In the bulbar ALS group, median (interquartile range) VC with the flanged mouthpiece was 8.4% (3.9-15.5) larger than with the cylindrical mouthpiece (p < 0.001). VC values with oronasal mask were intermediate to VC with the other two interfaces. In spinal ALS, flanged mouthpiece VC was 4.6% (2.3-7.5) larger than with oronasal mask (p < 0.0006). The latter was 4.5% (0.6-5.2) smaller than with the cylindrical mouthpiece (p = 0.002). In both groups, VC during the second visit was greater than during the first visit (p < 0.025). SNIPs were logarithmically related to VC values recorded with the flanged mouthpiece.

CONCLUSION

A flanged mouthpiece yields the largest values of VC in patients with bulbar and spinal ALS.

The importance of maintaining the same order of performance of lung function and SNIP tests in patients with amyotrophic lateral sclerosis

Objective: Sniff nasal inspiratory pressure (SNIP), a useful tool for the assessment of diaphragm function in patients with Amyotrophic Lateral Sclerosis (ALS), is usually performed together with lung function tests. The aim of this study was to evaluate whether SNIP results are influenced by the order of performance of the tests. Methods: 103 consecutive patients (65% males, 80% spinal onset) were recruited. The highest value of up to 10 sniffs, was recorded before (SNIPT0) and after (SNIPT1) the assessment of lung function, peak cough (PCF), and peak expiratory flow (PEF). Results: Mean and median values were respectively 31.10 and 26.00 cm H₂O for SNIPT0 and 28.93 and 25.00 cm H₂O for SNIPT1 (p < 0.001). The median value of (SNIPT1 - SNIPT0)/SNIPT0% was -7.10. Patients showing post lung function SNIP values above the median were included in Group 1 (51%), the others in group 2 (49%). Group 2 showed more severe baseline ventilatory restriction and reduction in PCF than Group 1. Positive direct relationships were found between SNIPT0 and SNIPT1 (coefficient β = 0.95, p < 0.001), and forced vital capacity and forced expiratory volume at one second. Conclusions: 50/103(49%) patients with ALS show a significant reduction in SNIP when assessed shortly after the performance of lung function tests. These patients suffer from more severe ventilatory restriction than patients not showing the reduction. Our findings suggest standardizing the order of respiratory tests during the follow up in order to avoid to misestimate the real strength of inspiratory muscles.

Sleep and Sleep Disruption in Amyotrophic Lateral Sclerosis

PURPOSE OF REVIEW

In amyotrophic lateral sclerosis (ALS), sleep disruption is frequently present and substantially adds to disease burden. This review aims to summarize current knowledge on causes, pathophysiology, and treatment of sleep disturbances in ALS.

RECENT FINDINGS

Motor neuron degeneration and muscle weakness may lead to muscle cramps, pain, spasticity, immobilization, restless legs, sleep-disordered breathing, and difficulties to clear secretions. Furthermore, existential fears and depression may promote insomnia. Sleep-disordered breathing, and nocturnal hypoventilation in particular, requires ventilatory support which meaningfully prolongs survival and improves health-related quality of life albeit respiratory failure is inevitable. Early indication for non-invasive ventilation can be achieved by inclusion of capnometry in diagnostic sleep studies. Sleep disruption is extremely common in ALS and may arise from different etiologies. The absence of causative therapeutic options for ALS underlines the importance of symptomatic and palliative treatment strategies that acknowledge sleep-related complaints.

Sleep disturbances in patients with amyotrophic lateral sclerosis: current perspectives

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease inevitably leading to generalized muscle weakness and premature death. Sleep disturbances are extremely common in patients with ALS and substantially add to the burden of disease for both patients and caregivers. Disruption of sleep can be caused by physical symptoms, such as muscle cramps, pain, reduced mobility, spasticity, mucus retention, and restless legs syndrome. In addition, depression and anxiety may lead to significant insomnia. In a small subset of patients, rapid eye movement (REM) sleep behavioral disorder may be present, reflecting neurodegeneration of central nervous system pathways which are involved in REM sleep regulation. With regard to overall prognosis, sleep-disordered breathing (SDB) and nocturnal hypoventilation (NH) are of utmost importance, particularly because NH precedes respiratory failure. Timely mechanical ventilation is one of the most significant therapeutic measures to prolong life span in ALS, and transcutaneous capnometry is superior to pulse oxymetry to detect NH early. In addition, it has been shown that in patients on home ventilatory support, survival time depends on whether normocapnia, normoxia, and elimination of apneic events during sleep can be reliably achieved. Several studies have investigated sleep patterns and clinical determinants of sleep disruption in ALS, but exact prevalence numbers are unknown. Thus, constant awareness for sleep-related symptoms is appropriate. Since no curative treatment can be offered to affected patients, sleep complaints should be thoroughly investigated in order to identify any treatable etiology and improve or stabilize quality of life as much as possible. The use of hypnotics should be confined to palliation during the terminal phase and refractory insomnia in earlier stages of the disease, taking into account that most compounds potentially aggravate SDB.

Non-invasive ventilation in amyotrophic lateral sclerosis

Non-invasive ventilation (NIV) has become an important cornerstone of symptomatic treatment in amyotrophic lateral sclerosis (ALS), improving survival and quality of life. In this review, we summarize the most important recent developments and insights, including evidence of efficacy, indication criteria and time of initiation, ventilation parameters and adaptation strategies, treatment of complicating factors, transition from NIV to invasive ventilation, termination of NIV and end-of-life management. Recent publications have questioned former conventions and guideline recommendations, especially with regard to timing and prognostic factors; therefore, a fresh look and re-evaluation of current evidence is needed.

Long-Term Ventilation in Neuromuscular Patients: Review of Concerns, Beliefs, and Ethical Dilemmas

BACKGROUND

Noninvasive mechanical ventilation (NIV) is an effective treatment in patients with neuromuscular diseases (NMD) to improve symptoms, quality of life, and survival.

SUMMARY

NIV should be used early in the course of respiratory muscle involvement in NMD patients and its requirements may increase over time. Therefore, training on technical equipment at home and advice on problem solving are warranted. Remote monitoring of ventilator parameters using built-in ventilator software is recommended. Telemedicine may be helpful in reducing hospital admissions. Anticipatory planning and palliative care should be carried out to lessen the burden of care, to maintain or withdraw from NIV, and to guarantee the most respectful management in the last days of NMD patients' life. Key Message: Long-term NIV is effective but challenging in NMD patients. Efforts should be made by health care providers in arranging a planned transition to home and end-of-life discussions for ventilator-assisted individuals and their families.

Sleep disordered breathing in motor neurone disease

Motor neurone disease (MND) is a neurodegenerative disease defined by axonal loss and gliosis of upper and lower motor neurones in the motor cortex, lower brainstem nuclei and ventral horn of the spinal cord. MND is currently incurable and has a poor prognosis, with death typically occurring 3 to 5 years after disease onset. The disease is characterised by rapidly progressive weakness leading to paralysis, fasciculations, bulbar symptoms (including dysarthria and dysphagia) and respiratory compromise. Respiratory complications arise as a result of weakness of upper airway (pharyngeal and laryngeal) muscles and respiratory muscles (diaphragm, intercostal and accessory muscles) leading to respiratory failure. Due to early involvement of respiratory muscles in MND, sleep disordered breathing (SDB) occurs at a higher frequency than compared to the general population. SDB usually precedes daytime respiratory symptoms and chronic respiratory failure. It significantly impacts upon patients' quality of life and survival and its presence may predict prognosis. Managing SDB in MND with non-invasive ventilation (NIV) improves quality of life and survival. Early identification and management of SDB in MND patients is therefore crucial. This update will review assessments of respiratory muscle function, types of SDB and the effects of NIV in patients with MND.

Percutaneous endoscopic gastrostomy under conscious sedation in patients with amyotrophic lateral sclerosis is safe: an observational study

OBJECTIVES

Amyotrophic lateral sclerosis (ALS) is a progressive neuromuscular disease that causes muscle weakness with respiratory and swallowing dysfunction, eventually leading to death. Permanent enteral feeding is indicated in almost all patients. A percutaneous endoscopic gastrostomy (PEG) tube is considered the first choice, usually performed under conscious sedation (intravenous midazolam). Guidelines are very cautious with respect to sedation in ALS because of the risk for respiratory complications. In our tertiary referral hospital, conscious sedation has been used for many years.Our aim was to review 30-day complications in PEG performed under conscious sedation in ALS patients (without noninvasive positive pressure ventilation during the procedure).

PATIENTS AND METHODS

A retrospective review, including all ALS patients undergoing PEG under conscious sedation from October 2009 to April 2016, was performed.

RESULTS

Analysis included 45 (44% men) patients receiving intravenous midazolam sedation (mean dose 5 mg) during PEG placement, age 36-91 years (mean: 68.7 years). Forced vital capacity (FVC) was 24-116% (mean 68%), of which mild to moderate dysfunction (FVC 50-69%) was present in 42.2% of patients and (very) severe dysfunction (FVC <50%) in 8.8%. No respiratory complications (e.g. aspiration pneumonia) were observed. Other complications, for example, infection, bleeding and peritonitis occurred in, respectively, 8.9, 2.2 and 0%. Mean survival after PEG placement was 13.4 months (range: 1-45 months).

CONCLUSION

Conscious sedation during PEG insertion in ALS patients did not lead to respiratory complications or to an increase in other complications. Our data indicate that conscious sedation can be used safely in ALS patients with mild to moderate pulmonary dysfunction.

The predictive value of respiratory function tests for non-invasive ventilation in amyotrophic lateral sclerosis

Background

Non-invasive ventilation (NIV) improves survival and quality of life in amyotrophic lateral sclerosis (ALS) patients. The timing of referral to a home ventilation service (HVS), which is in part based on respiratory function tests, has shown room for improvement. It is currently unknown which respiratory function test predicts an appropriate timing of the initiation of NIV.

Methods

We analysed, retrospectively, serial data of five respiratory function tests: forced vital capacity (FVC), peak cough flow (PCF), maximum inspiratory and expiratory pressure (MIP and MEP) and sniff nasal inspiratory pressure (SNIP) in patients with ALS. Patients who had had at least one assessment of respiratory function and one visit at the HVS, were included. Our aim was to detect the test with the highest predictive value for the need for elective NIV in the following 3 months. We analysed time curves, currently used cut-off values for referral, and respiratory function test results between ‘NIV indication’ and ‘no-NIV indication’ patients.

Results

One hundred ten patients with ALS were included of whom 87 received an NIV indication; 11.5% had one assessment before receiving an NIV indication, 88.5% had two or more assessments. The NIV indication was based on complaints of hypoventilation and/or proven (nocturnal) hypercapnia. The five respiratory function tests showed a descending trend during disease progression, where SNIP showed the greatest decline within the latest 3 months before NIV indication (mean = −22%). PCF at the time of referral to the HVS significantly discriminated between the groups ‘NIV-indication’ and ‘no NIV-indication yet’ patients at the first HVS visit: 259 (±92) vs. 348 (±137) L/min, p = 0.019. PCF and SNIP showed the best predictive characteristics in terms of sensitivity.

Conclusion

SNIP showed the greatest decline prior to NIV indication and PCF significantly differentiated ‘NIV-indication’ from ‘no NIV-indication yet’ patients with ALS. Currently used cut-off values might be adjusted and other respiratory function tests such as SNIP and PCF may become part of routine care in patients with ALS in order to avoid non-timely initiation of (non-invasive) ventilation.

The Prognostic Role of Obstructive Sleep Apnea at the Onset of Amyotrophic Lateral Sclerosis

BACKGROUND/OBJECTIVE

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the progressive loss of central and peripheral motor neurons. Some studies have found discordant data in the presence of sleep apnea in ALS patients. An obstructive component also occurs with upper airways hypotonia and muscle weakness that may result in an excessive reduction of airway lumen, leading to obstructive sleep apnea (OSA). The aim of this study was to assess the role of obstructive apneic events at disease onset in the ALS prognosis.

METHODS

A longitudinal retrospective study was conducted on 42 clinically diagnosed ALS patients. The study population was divided into 2 groups according to their obstructive apnea/hypopnea index (AHIo): group 1 consisted of 20 patients with an AHIo ≥5 and group 2 consisted of 22 patients with an AHIo <5. Both groups were compared with regard to demographic, polygraphic, and respiratory function parameters as well as ALS characteristics (bulbar onset, time between onset and first check-up, time between diagnosis and first check-up, time between first check-up and death or tracheostomy).

RESULTS

The mean survival in ALS patients with an AHIo ≥5 was significantly shorter than in ALS without OSA (p = 0.0237). The sniff nasal inspiratory pressure test was significantly correlated with AHIo, time of oxyhemoglobin saturation below 90% and the oxyhemoglobin desaturation index (p < 0.0001).

CONCLUSIONS

Our study highlights the importance of an early diagnosis of OSA in ALS patients, allowing the identification of ALS patients with an OSA phenotype (AHIo ≥5), who are characterized by a worse prognosis.

Progression from respiratory dysfunction to failure in late-onset Pompe disease

To identify determinants of respiratory disease progression in late-onset Pompe disease (LOPD), we studied relationships between pulmonary function, respiratory muscle strength, gas exchange, and respiratory control. Longitudinal evaluation of 22 LOPD patients (mean age 38 years) was performed at 6-month intervals for 6-24 months. Measurements included vital capacity (VC), maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), tidal volume (VT), dead space (VD), and ventilatory response to CO2. Although reduction in VC correlated with MIP and MEP (p < 0.0001), some patients had normal VC despite reduced MIP and MEP (5 [23%] and 9 [41%] patients, respectively). Daytime hypercapnia was associated with reduced VC (<60% predicted) and MIP (<40% predicted). Moreover, chronic hypercapnia was associated with elevated VD/VT (≥0.44) due to falling VT (≈300 ml), compatible with reduced efficiency of CO2 clearance. The presence of hypercapnia and/or ventilatory support was associated with reduced ventilatory responsiveness to CO2 (≤0.7 l/min/mmHg). We conclude that daytime hypercapnia, an indicator of chronic respiratory failure, is tightly linked to the degree of respiratory muscle weakness and severity of pulmonary dysfunction in LOPD patients. Reductions in CO2 clearance efficiency and ventilatory responsiveness may contribute to the development of chronic daytime hypercapnia.

Ultrasound for assessment of diaphragm in ALS

OBJECTIVE

To evaluate the correlation between diaphragm thickness assessed by ultrasound (US) with respiratory function tests and the diaphragm motor responses, in patients with amyotrophic lateral sclerosis (ALS).

METHODS

42 consecutive ALS patients were studied (11 with bulbar-onset), excluding patients with marked orofacial paresis. Investigation included: revised ALS functional rating scale (ALSFRS-R), forced vital capacity (FVC), maximal voluntary ventilation (MVV), maximal inspiratory (MIP) and expiratory (MEP) pressures, nasal inspiratory pressure during sniff (SNIP); peak-to-peak amplitude of the diaphragmatic motor response to phrenic nerve stimulation (Diaphragm-CMAP), diaphragmatic thickness measured by ultrasound during maximal inspiration and during maximal expiration. Patients were analysed in bulbar or spinal subgroups. Correlations and multiple linear regression models were studied.

RESULTS

The mean age at disease onset was 58.4 ± 11.1 years and with a mean disease duration of 17.8 ± 13.6 months. Ultrasound studies of diaphragm thickness in full inspiration correlated with diaphragm CMAP in the whole population and in spinal-onset patients; and were similar in the two groups. Multiple linear modelling showed that FVC, SNIP and MVV were dependent on the change of thickness (p=0.001, 0.001 and 0.020, respectively) and that MIP and MEP were related to diaphragm CMAP p=0.003 and p=0.025, respectively).

CONCLUSION

Diaphragm thickness correlates with Diaphragm-CMAP, except in bulbar-onset patients. Respiratory tests are dependent on both diaphragm thickness and Diaphragm-CMAP.

SIGNIFICANCE

US thickness of the diaphragm correlates with the number of functional motor units as assessed by the phrenic nerve motor amplitude.

Sniff nasal inspiratory pressure as a prognostic factor of tracheostomy or death in amyotrophic lateral sclerosis

Forced vital capacity (FVC) shows limitations in detecting respiratory failure in the early phase of amyotrophic lateral sclerosis (ALS). In fact, mild-to-moderate respiratory muscle weakness may be present even when FVC is normal, and ALS patients with bulbar involvement might not be able to perform correctly the spirometry test. Sniff nasal inspiratory pressure (SNIP) is correlated with transdiaphragmatic strength. We evaluated SNIP at baseline as a prognostic factor of tracheostomy or death in patients with ALS. In a multidisciplinary tertiary care center for motorneuron disease, we enrolled 100 patients with ALS diagnosed with El Escorial criteria in the period between January 2006 and December 2010. Main outcome measures were tracheostomy or death. RECursive Partitioning and AMalgamation (RECPAM) analysis was also used to identify subgroups at different risks for the tracheostomy or death. Twenty-nine patients with ALS reached the outcome (12 died and 17 had tracheostomy). Using a multivariate model SNIP correctly classified the risk of the composite event within 1 year of follow-up with a continuous Net Reclassification Improvement cNRI of 0.58 (p = 0.03). Sex, Amyotrophic Lateral Sclerosis Functional Rating Scale revisited, site of onset, and FVC did not improve the classification of prognostic classes. SNIP ≤18 cmH2O identified the RECPAM class with the highest risk (Class 1, hazard ratio = 9.85, 95 % confidence interval: 2.67-36.29, p < 0.001). SNIP measured at baseline identified patients with ALS with initial respiratory failure. Finally, using only ALS patients with spinal onset of the disease, our findings were mostly overlapping with those reported in the models including the whole sample. At baseline, SNIP appeared to be the best predictor of death or tracheostomy within 1 year of follow-up. The measurement of SNIP in the early phase of the disease may contribute to identify patients with high risk of mortality or intubation. SNIP may also provide an additional tool for baseline stratification of patients with ALS in clinical trials.

Respiratory insufficiency with preserved diaphragmatic function in amyotrophic lateral sclerosis

OBJECTIVE

We performed a longitudinal study to elucidate the correlation between respiratory insufficiency and respiratory biomarkers, including diaphragmatic compound muscle action potential (DCMAP), at the initiation of noninvasive ventilation (NIV) in patients with amyotrophic lateral sclerosis (ALS).

METHODS

The patients were assessed at least every six months. Additional assessments were performed at the start of respiratory therapy when the patients met the criteria for the initiation of NIV. Each assessment consisted of a full neurological examination, a phrenic nerve conduction study, respiratory function tests, and nocturnal pulsed oximetry.

PATIENTS

We enrolled 43 patients with either definite or probable ALS as defined by the revised El Escorial criteria.

RESULTS

The patients were divided into two groups according to the timing of the initiation of respiratory therapy. Seventeen patients (group A) met the criteria for NIV initiation when their DCMAP remained normal. Twenty-six patients (group B) met the criteria when their DCMAP decreased below normal limits. Although respiratory function parameters were significantly worse in group B compared with group A at NIV initiation, more than 80% of the patients in both groups developed nocturnal desaturation during sleep.

CONCLUSION

DCMAP is not always a reliable indicator for determining the optimal timing for NIV initiation during the progression of respiratory insufficiency in ALS. Physicians should be aware of the risk of respiratory insufficiency during sleep in patients with ALS.

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.

Sleep–wake problems in patients with amyotrophic lateral sclerosis: implications for patient management

SUMMARY Sleep–wake problems are frequent, although unrecognized, complications of amyotrophic lateral sclerosis (ALS). Sleep disorders such as insomnia, sleep-disordered breathing and restless legs syndrome have all been reported in patients with ALS, despite the limited number of studies and the small populations investigated so far. Sleep disturbances gradually worsen with disease progression, suggesting a relationship between the severity of disease and the neurodegenerative process. However, poor sleep can also be a consequence of several disturbances such as anxiety, depression, pain, choking, sialorrhea, fasciculations, cramps, nocturia and the inability to get comfortable and move freely in bed. Sleep disorders may have many reflections on patients with ALS, including excessive daytime somnolence, fatigue, impaired cognition, reduced quality of life and survival. This article reviews the recent literature on sleep–wake problems in patients with ALS, focusing on the implications for patient management.