Update and perspectives on noninvasive respiratory muscle aids. Part 1: The inspiratory aids

Childhood spinal muscular atrophy

Spinal muscular atrophy (SMA) is caused by biallelic mutations in the SMN1 (survival motor neuron 1) gene on chromosome 5q13.2, which leads to a progressive degeneration of alpha motor neurons in the spinal cord and in motor nerve nuclei in the caudal brainstem. It is characterized by progressive proximally accentuated muscle weakness with loss of already acquired motor skills, areflexia and, depending on the phenotype, varying degrees of weakness of the respiratory and bulbar muscles. Over the past decade, disease-modifying therapies have become available based on splicing modulation of the SMN2 with SMN1 gene replacement, which if initiated significantly modifies the natural course of the disease. Newborn screening for SMA has been implemented in an increasing number of centers; however, available evidence for these new treatments is often limited to a small spectrum of patients concerning age and disease stage.

Congenital myopathies

The congenital myopathies are inherited muscle disorders characterized clinically by hypotonia and weakness, usually from birth, with a static or slowly progressive clinical course. Historically, the congenital myopathies have been classified according to major morphological features seen on muscle biopsy as nemaline myopathy, central core disease, centronuclear or myotubular myopathy, and congenital fiber type disproportion. However, in the past two decades, the genetic basis of these different forms of congenital myopathy has been further elucidated with the result being improved correlation with histological and genetic characteristics. However, these notions have been challenged for three reasons. First, many of the congenital myopathies can be caused by mutations in more than one gene that suggests an impact of genetic heterogeneity. Second, mutations in the same gene can cause different muscle pathologies. Third, the same genetic mutation may lead to different pathological features in members of the same family or in the same individual at different ages. This chapter provides a clinical overview of the congenital myopathies and a clinically useful guide to its genetic basis recognizing the increasing reliance of exome, subexome, and genome sequencing studies as first-line analysis in many patients.

Continuous noninvasive ventilatory support outcomes for patients with neuromuscular disease: a multicenter data collaboration

BACKGROUND

Typically, patients with progressive neuromuscular disorders (NMDs) develop acute respiratory failure (ARF), are intubated, and when failing spontaneous breathing trials (SBTs) undergo a tracheotomy and receive tracheostomy mechanical ventilation (TMV). However, increasing numbers of patients use nasal noninvasive ventilation (NIV), initially for sleep and this is extended to continuous dependence (CNVS). This can be used as a strategy to assist in successful extubation . We retrospectively reviewed 19 centers offering CNVS and mechanical insufflation-exsufflation (MI-E) as an alternative to TMV.

METHODS

Centers with publications or presentations concerning CNVS outcomes data were pooled for amyotrophic lateral sclerosis (ALS), Duchenne muscular dystrophy (DMD), and spinal muscular atrophy type 1 (SMA1). Progression to CNVS dependence without hospitalization, duration of dependence, and extubations and decannulations to CNVS were recorded. Prolongation of life was defined by duration of CNVS dependence without ventilator free breathing ability (VFBA).

RESULTS

There were 1623 part time (<23 h/day) NVS users with ALS, DMD, and SMA1 from 19 centers in 16 countries of whom 761 (47%) were CNVS dependent for 2218 patient-years. This included: 335 ALS patients for a mean 1.2 ± 1.0 (range to 8) years each; 385 DMD patients for 5.4 ± 1.6 (range to 29) years; and 41 SMA1 patients for 5.9 ± 1.8 (range to 20) years. Thirty-five DMD and ALS TMV users were decannulated to CNVS and MI-E. At data collection 494 (65%) patients were CNVS dependent but 110 (74 of whom with bulbar ALS), had undergone tracheotomies.

CONCLUSIONS

ALS, DMD, and SMA1 patients can become CNVS dependent without requiring hospitalization but CNVS cannot be used indefinitely for many patients with advanced upper motor neuron diseases.

Respiratory Complications of Pediatric Neuromuscular Diseases

Respiration is an event of oxygen consumption and carbon dioxide production. Respiratory failure is common in pediatric neuromuscular diseases and the main cause of morbidity and mortality. It is a consequence of lung failure, ventilatory pump failure, or their combination. Lung failure often is due to chronic aspiration either from above or from below. It may lead to end-stage lung disease. Ventilatory pump failure is caused by increased respiratory load and progressive respiratory muscles weakness. This article reviews the normal function of the respiratory pump, general pathophysiology issues, abnormalities in the more common neuromuscular conditions and noninvasive interventions.

Noninvasive ventilatory support in morbid obesity

BACKGROUND

In the conventional management of the morbidly obese that normalizes the apnea-hypopnea index (AHI), CO2 levels often remain elevated.

METHODS

A retrospective review of morbidly obese patients using volume preset settings up to 1800ml to positive inspiratory pressures (PIPs) of 25-55cm H2O, or pressure control at 25-50cm H2O pressure via noninvasive interfaces up to continuously (CNVS).

RESULTS

Twenty-six patients, mean 55.6±14.8 years of age, weight 108-229kg, mean BMI 56.1 (35.5-77)kg/m², mean AHI 69.0±24.9, depended on up to CNVS for 3 weeks to up to 66 years. There were eleven extubations and seven decannulations to CNVS despite failure to pass spontaneous breathing trials. Thirteen were CNVS dependent for 92.2 patient-years with little to no ventilator free breathing ability (VFBA). Six used NVS from 10 to 23h a day, and others only for sleep. Fifteen patients with cough peak flows (CPF) less than 270L/m had access to mechanical insufflation-exsufflation (MIE) in the peri-extubation/decannulation period and long-term. The daytime end-tidal (Et)CO2 of 14 who were placed on sleep NVS without extubation or decannulation to it decreased from mean EtCO2 61.0±9.3-38.5±3.6mm Hg and AHI normalized to 2.2. Blood gas levels were normal while using NVS/CNVS. Pre-intubation PaCO2 levels, when measured, were as high as 183mm Hg before extubation to CNVS.

CONCLUSIONS

Ventilator unweanable morbidly obese patients can be safely extubated/decannulated and maintained indefinitely using up to CNVS rather than resort to tracheotomies.

ERS statement on respiratory muscle testing at rest and during exercise

Assessing respiratory mechanics and muscle function is critical for both clinical practice and research purposes. Several methodological developments over the past two decades have enhanced our understanding of respiratory muscle function and responses to interventions across the spectrum of health and disease. They are especially useful in diagnosing, phenotyping and assessing treatment efficacy in patients with respiratory symptoms and neuromuscular diseases. Considerable research has been undertaken over the past 17 years, since the publication of the previous American Thoracic Society (ATS)/European Respiratory Society (ERS) statement on respiratory muscle testing in 2002. Key advances have been made in the field of mechanics of breathing, respiratory muscle neurophysiology (electromyography, electroencephalography and transcranial magnetic stimulation) and on respiratory muscle imaging (ultrasound, optoelectronic plethysmography and structured light plethysmography). Accordingly, this ERS task force reviewed the field of respiratory muscle testing in health and disease, with particular reference to data obtained since the previous ATS/ERS statement. It summarises the most recent scientific and methodological developments regarding respiratory mechanics and respiratory muscle assessment by addressing the validity, precision, reproducibility, prognostic value and responsiveness to interventions of various methods. A particular emphasis is placed on assessment during exercise, which is a useful condition to stress the respiratory system.

Mouthpiece ventilation and complementary techniques in patients with neuromuscular disease: A brief clinical review and update

Noninvasive ventilatory support (NVS) is sometimes reported as suboptimal in patients with neuromuscular disease (NMD). The reasons for this include inadequate ventilator settings and/or lack of interface tolerance. NVS has been used for many years in patients with NMD disorders as a viable alternative to continuous ventilatory support via a tracheostomy tube. The mouthpiece ventilation (MPV) is a ventilatory mode that is used as daytime ventilatory support in combination with other ventilatory modalities and interfaces for nocturnal NVS. However, there is still a poor understanding of this method's benefits compared with other modalities. This review aims to highlight the indications and advantages along with the disadvantages of MPV.

Independent cough flow augmentation by glossopharyngeal breathing plus table thrust in muscular dystrophy

OBJECTIVE

The purpose of the present study was to compare the unassisted cough peak flow (CPF) of patients affected by muscular dystrophy with CPF augmented by various techniques, including maximal depth glossopharyngeal breathing (GPB) combined with a subsequent self-induced thoracic or abdominal thrust.

DESIGN

All of the motorized wheelchair-dependent patients with muscular dystrophy who had previously mastered GPB were trained at home to increase their cough efficacy. This training involved maneuvering their wheelchair against the edge of a specially built table to autonomously produce a thoracic and/or abdominal thrust timed to the opening of the glottis for an independently assisted cough. Both unassisted and variously assisted CPFs were compared.

RESULTS

The 18 patients (17 men/1 woman) with muscular dystrophy, aged 21.1 ± 5.4 yrs, achieved variously assisted CPFs that were significantly higher than the spontaneous CPF (P < 0.001), with assisted CPFs but not unassisted CPFs that significantly exceeded a reported efficacious cough threshold value of 160 liters/min (P < 0.001). Moreover, increases in the CPFs by personal assistance including air stacking by manual resuscitator and thoracoabdominal thrust (326.4 ± 79.5 liters/min) or by GPB and thoracoabdominal thrust (326.4 ± 87.5 liters/min) were not significantly different (P = 0.07) from the CPFs independently attained by GPB plus independently maneuvering a wheelchair for a table thrust (310.3 ± 74.7 liters/min).

CONCLUSIONS

The independently assisted (GPB plus table thrust) CPF was comparable to the CPFs that required personal assistance for air stacking and abdominal thrusts. Therefore, for patients with muscular dystrophy, this physical medicine technique and cough-assisted techniques that require personal intervention are strongly recommended.

Laryngeal response patterns to mechanical insufflation-exsufflation in healthy subjects

OBJECTIVE

Mechanical insufflation-exsufflation (MI-E) is used to assist cough in patients with neuromuscular diseases. Clinically, application may be challenging in some patient groups, possibly related to laryngeal dysfunction. Before launching a study in patients, the authors investigated laryngeal responses to MI-E in healthy individuals.

DESIGN

Twenty healthy volunteers, aged 21-29 yrs, were studied with video-recorded flexible transnasal fiber-optic laryngoscopy while performing MI-E using the Cough Assist (Respironics, United States) according to a standardized protocol applying pressures of ±20 to ±50 cm H2O.

RESULTS

An initial abduction of the vocal folds was observed in all subjects, both during the insufflation and exsufflation phases. Nineteen of the 20 subjects adequately coordinated glottic closure when instructed to cough. When instructed simply to exhale during exsufflation, the glottis stayed open in a majority. Subsequent to an initial abduction during exsufflation and cough, various obstructive laryngeal movements were observed in some subjects, such as narrowing of the vocal folds, retroflexion of the epiglottis, hypopharyngeal constriction, and backward movement of the base of the tongue.

CONCLUSIONS

The larynx can be studied with transnasal laryngoscopy during MI-E in healthy individuals. Laryngeal responses to MI-E vary, and laryngoscopy may offer valuable clinical information when applying MI-E in patients with bulbar muscle weakness.

Noninvasive respiratory management and diaphragm and electrophrenic pacing in neuromuscular disease and spinal cord injury

The purpose of this monograph is to describe noninvasive management of respiratory muscle weakness/paralysis for patients with neuromuscular disease (NMD) and spinal cord injury (SCI). Noninvasive ventilation (NIV) assists and supports inspiratory muscles, whereas mechanically assisted coughing (MAC) simulates an effective cough. Long-term outcomes will be reviewed as well as the use of NIV, MAC, and electrophrenic pacing (EPP) and diaphragm pacing (DP) to facilitate extubation and decannulation. Although EPP and DP can facilitate decannulation and maintain alveolar ventilation for high-level SCI patients when they cannot use NIV because of lack of access to oral interfaces, there is no evidence that they have any place in the management of NMD.

Trends in outcome and hospitalization charges of adult patients admitted with botulism in the United States

BACKGROUND

To assess the impact of new therapeutic strategies on outcomes and hospitalization charges among adult patients with botulism in the United States.

METHODS

We determined in-hospital outcomes and charges for patients with botulism hospitalized in 1993-1994 and compared them with those observed among patients hospitalized in 2006-2007. Mortality, length of stay, and hospitalization charges were calculated. Age, sex, race, ethnicity, and discharge status were also reported.

RESULTS

There were 66 and 132 admissions of adult patients with botulism in 1993-1994 and 2006-2007, respectively. Men predominance was observed in 2006-2007 compared to women predominance during the 1993-1994 time period. There was no significant difference in the average length of stay and in-hospital mortality rate between the two groups studied. However, in the 2006-2007 group, there was a significant increase in the mean hospitalization charges (USD 126,092 ± 120,535 vs. USD 83,623 ± 82,084; p = 0.0107) and in the proportion of patients requiring mechanical ventilation when compared to 1993-1994 (34 vs. 13.6%; p < 0.0001).

CONCLUSION

Botulism continues to be an infrequent cause of hospitalization, with a significant increase in the average hospitalization charges in 2006-2007 when compared to 1993-1994, despite a nonsignificant change in the mortality rate and average length of hospitalization.

Resolution of tracheostomy complications by decanulation and conversion to noninvasive management for a patient with high-level tetraplegia

OBJECTIVES

To report conversion from tracheostomy (TIV) to noninvasive intermittent positive pressure ventilation (NIV) for a continuously ventilator-dependent patient with high-level spinal cord injury (SCI) with no measurable vital capacity (VC = 0 mL) to resolve tracheostomy-associated complications.

METHODS

A case report of a 38-year-old female in a chronic care facility in Japan with a 10-year history of ventilator-dependent tetraplegia (C1 ASIA-A) presented for increasing difficulty vocalizing. She had been using a fenestrated cuffed tracheostomy tube to produce speech with the cuff deflated. Speech was increasingly hypophonic, because of tracheostoma enlargement, tube migration, and tracheal granulation.

RESULTS

The NIV was provided via nasal and oral interfaces, the ostomy was surgically closed, and vocalization resumed. Airway secretions were expulsed using manually assisted coughing. The patient returned to the community.

CONCLUSION

Conversion to NIV should be considered for ventilator-dependent patients with SCI who have adequate bulbar-innervated muscle function to permit effective speech and assisted coughing.

The use of mechanical ventilation is appropriate in children with genetically proven spinal muscular atrophy type 1: the motion for

The purpose of this paper is to report prolongation of survival for Werdnig-Hoffman's disease (spinal muscular atrophy type 1, SMA 1) by use of non-invasive respiratory muscle aids compared with tracheostomy, and to present reasons for offering this as an option to the parents of these children. Ninety per cent of typical untreated SMA 1 patients die before 12 months of age and 100% by 24 months of age. Tracheostomy can prolong survival to over 20 years of age in some cases, but patients with tubes do not develop the ability to speak and lose all ability to breathe from the point of the tracheotomy. In contrast, the majority of non-invasively managed SMA 1 patients develop the ability to communicate verbally and maintain some autonomous breathing ability. Clinicians' treatment paradigms associate ventilatory support with invasive tubes and do not recognise aiding respiratory muscles. Clinicians also significantly underestimate the care providers' view of the patient's quality of life. As a result, they rarely offer non-invasive means to prolong life. In conclusion, both non-invasive aids and tracheostomy can prolong survival for SMA 1 patients, and it should be left up to the family to decide which, if either, they would like to use.

Effect of spinal cord injury on the respiratory system: basic research and current clinical treatment options

Spinal cord injury (SCI) often leads to an impairment of the respiratory system. The more rostral the level of injury, the more likely the injury will affect ventilation. In fact, respiratory insufficiency is the number one cause of mortality and morbidity after SCI. This review highlights the progress that has been made in basic and clinical research, while noting the gaps in our knowledge. Basic research has focused on a hemisection injury model to examine methods aimed at improving respiratory function after SCI, but contusion injury models have also been used. Increasing synaptic plasticity, strengthening spared axonal pathways, and the disinhibition of phrenic motor neurons all result in the activation of a latent respiratory motor pathway that restores function to a previously paralyzed hemidiaphragm in animal models. Human clinical studies have revealed that respiratory function is negatively impacted by SCI. Respiratory muscle training regimens may improve inspiratory function after SCI, but more thorough and carefully designed studies are needed to adequately address this issue. Phrenic nerve and diaphragm pacing are options available to wean patients from standard mechanical ventilation. The techniques aimed at improving respiratory function in humans with SCI have both pros and cons, but having more options available to the clinician allows for more individualized treatment, resulting in better patient care. Despite significant progress in both basic and clinical research, there is still a significant gap in our understanding of the effect of SCI on the respiratory system.

Noninvasive Ventilatory Assistance During Exercise for Patients with Kyphoscoliosis

The goal was to determine whether noninvasive ventilatory assistance (NIV) could facilitate exercise performance and benefit physiologic parameters for eight hypercapnic kyphoscoliosis patients using a cycloergometer for 6-min periods at a constant power (20 W). The exercise protocols were performed in random order while breathing unaided (spontaneous breathing test or SBT) and also while receiving NIV (NIV test or NIVT). The NIV was pressure support (15 cm H2O) plus positive end expiratory pressure (PEEP) (4 cm H2O) via a nasal mask. Of the compared parameters, heart rate was not significantly different, but acidosis (pH = 7.32 +/- 0.04 vs. 7.36 +/- 0.04), hypoxia (PaO2 = 61.5 +/- 15.9 vs. 69.5 +/- 15.7 mm Hg), and hypercapnia (PaCO2 = 54.3 +/- 7.6 vs. 47.1 +/- 7.1 mm Hg) were significantly greater for the SBT than for the NIVT (P < 0.05). The hypercapnia and hypoxia for the NIVT were not significantly greater than preexercise resting levels. Dyspnea and perceived effort were significantly greater for the SBT (P < 0.05). In conclusion, NIV can improve clinical and physiologic response to exercise.

Effects of glossopharyngeal pistoning for lung insufflation on vital capacity in healthy women

OBJECTIVES

To determine whether healthy women could be trained to perform glossopharyngeal pistoning (GP) to insufflate the lungs to volumes exceeding maximum inspiratory capacity (IC), whether such insufflation caused discomfort, and the immediate and long-term effects on vital capacity (VC).

DESIGN

A randomized controlled trial. Twenty-six healthy women were randomly assigned to a training group (TG, n = 17) or to a control group (CG, n = 9). The TG performed 15-30 deep inspiratory efforts supplemented by GP to lung volumes exceeding IC, three times per week for 6 wks. Pulmonary function and chest expansion were measured before and after the 6-wk period. The TG was retested again 12 wks after the end of the training period.

RESULTS

One of 17 women had difficulty performing GP and was excluded. Temporary symptoms (while performing GP) were reported in 44% of subjects in the TG. After 6 wks of training, subjects in the TG had significantly increased their VC (P < 0.001). VC did not change in the CG. The increase in vital capacity of the TG was still evident after 12 wks without performing GP. Chest expansion increased significantly with GP.

CONCLUSION

The women in the TG were able to perform the technique, and it did not cause major discomfort. VC increased significantly in the TG, and the increase was still present after 12 wks without GP.

Effect of spinal cord injury on the respiratory system: basic research and current clinical treatment options

Spinal cord injury (SCI) often leads to an impairment of the respiratory system. The more rostral the level of injury, the more likely the injury will affect ventilation. In fact, respiratory insufficiency is the number one cause of mortality and morbidity after SCI. This review highlights the progress that has been made in basic and clinical research, while noting the gaps in our knowledge. Basic research has focused on a hemisection injury model to examine methods aimed at improving respiratory function after SCI, but contusion injury models have also been used. Increasing synaptic plasticity, strengthening spared axonal pathways, and the disinhibition of phrenic motor neurons all result in the activation of a latent respiratory motor pathway that restores function to a previously paralyzed hemidiaphragm in animal models. Human clinical studies have revealed that respiratory function is negatively impacted by SCI. Respiratory muscle training regimens may improve inspiratory function after SCI, but more thorough and carefully designed studies are needed to adequately address this issue. Phrenic nerve and diaphragm pacing are options available to wean patients from standard mechanical ventilation. The techniques aimed at improving respiratory function in humans with SCI have both pros and cons, but having more options available to the clinician allows for more individualized treatment, resulting in better patient care. Despite significant progress in both basic and clinical research, there is still a significant gap in our understanding of the effect of SCI on the respiratory system.

Expiratory Flow Maneuvers in Patients with Neuromuscular Diseases

OBJECTIVES

To compare cough peak flows (CPF), peak expiratory flows (PEF), and potentially confounding flows obtained by lip and tongue propulsion (dart flows, DF) for normal subjects and for patients with neuromuscular disease/restrictive pulmonary syndrome and to correlate them with vital capacity and maximum insufflation capacity.

DESIGN

A cross-sectional analytic study of 125 stable patients and 52 normal subjects in which CPF, PEF, and DF were measured by peak flow meter and vital capacity and maximum insufflation capacity by spirometer.

RESULTS

In normal subjects and in patients, the DF significantly exceeded PEF and CPF (P < or = 0.001). For normal subjects, PEF and CPF were not significantly different. For patients with neuromuscular disease/restrictive pulmonary syndrome, the CPF significantly exceeded PEF (P < 0.05). No normal subjects but 14 patients had DF lower than CPF. Thirteen of these 14 had the ability to air stack (maximum insufflation capacity greater than vital capacity), indicating greater compromise of mouth and lip than of glottic muscles. For 14 of 88 patients, maximum insufflation capacity values did not exceed vital capacity, mostly because of inability to close the glottis (inability to air stack). Nonetheless, for 11 of these 14 patients, the DF were within a standard deviation of the whole patient group; thus, bulbar-innervated muscle dysfunction was not uniform. CPF and PEF correlated with vital capacity (r = 0.85 and 0.86, respectively), and with maximum insufflation capacity (r = 0.76 and 0.72, respectively).

CONCLUSIONS

Measurements of CPF, PEF, and DF are useful for assessing bulbar-innervated, inspiratory, and expiratory muscle function. Care must be taken to not confuse them.

Oximetry and indications for tracheotomy for amyotrophic lateral sclerosis

STUDY OBJECTIVE

To explore the use of oximetry as a guide for using respiratory aids and tracheotomy in the treatment of patients with amyotrophic lateral sclerosis (ALS).

SETTING

A retrospective review of all ALS patients presenting to a neuromuscular disease clinic since 1996.

METHODS

Patients who were symptomatic for nocturnal hypoventilation were prescribed noninvasive ventilation (NIV). Patients with assisted cough peak flows of < 300 L/min were prescribed oximeters and access to mechanically assisted coughing (MAC) to prevent or reverse decreases in baseline pulse oximetric saturation (Spo(2)) levels of < 95%. The number of decreases in baseline Spo(2) that could be normalized by any combination of NIV and MAC and the duration of normalization were recorded. When the baseline was not or could not be normalized, the time to acute respiratory failure and tracheotomy or death were recorded.

RESULTS

Twenty-five patients became dependent on NIV, including 13 patients who received NIV continuously for a mean (+/- SD) period of 19.7 +/- 16.9 months, without desaturation (group 1). For another 76 patients, the daytime baseline Spo(2) level decreased to < 95% 78 times. For 41 patients, the baseline level was corrected by NIV/MAC (group 2) for a mean duration of 11.1 +/- 8.7 months before desaturation reoccurred for 27 patients. Of the latter patients, 11 underwent tracheotomy, 14 died in < 2 months, and 2 had their condition again corrected by the addition of MAC therapy. For 35 patients, the desaturation was not or could not be normalized (group 3). Thirty-three of these 35 patients required tracheotomy or died within 2 months. The only significant difference between groups 1 and 2 and group 3 was significantly poorer glottic function in the patients in group 3.

CONCLUSION

Tracheotomy or death is highly likely within 2 months of a decrease in baseline Spo(2) that cannot be corrected by NIV or MAC. The long-term use of NIV and MAC, and the avoidance of tracheotomy is dependent on glottic function rather than on inspiratory or expiratory muscle failure.

Effect of lung mechanics on mechanically assisted flows and volumes

OBJECTIVE

To correlate the air flows generated by mechanical insufflation-exsufflation as a function of pressure delivery in a lung model at two pulmonary compliance and three airway resistance settings.

DESIGN

With each combination of pulmonary compliances of 25 and 50 ml/cm H2O and airway resistances of 6, 11, and 17 cm H2O/liter/sec, ten cycles of mechanical insufflation-exsufflation were applied using pressure deliveries of 40 to -40, 50 to -50, 60 to -60, and 70 to -70 cm H2O. The resulting peak exsufflation flows and volumes were recorded.

RESULTS

In a multivariate analysis, the pulmonary compliance, airway resistance, and pressure delivery were all found to significantly affect exsufflation flows and volumes such that a decreased pulmonary compliance or an increased airway resistance produced a decrease in exsufflation flow and volume, whereas an increased pressure delivery produced greater exsufflation flow and volume.

CONCLUSION

Although mechanical insufflation-exsufflation pressures of 40 to -40 cm H2O are generally adequate for most patients with normal lung compliance and airway resistance, higher settings are often required when compliance decreases, by obesity or scoliosis, and possibly when airway resistance is increased.

Aspects pratiques et techniques de la ventilation non invasive

INTRODUCTION

Noninvasive ventilation refers to the delivery of positive pressure ventilation via a mask or "interface" rather than via an invasive conduit. Until recently, equipment for noninvasive ventilation was frequently custom-made to meet the needs of an individual patient. During the past 15 years, there have been significant advances in the equipment available for noninvasive ventilation.

STATE OF THE ART

Interfaces that have been designed specifically for noninvasive ventilation are now commercially available from several manufacturers. Commonly used interfaces include nasal and full face masks, and mouthpieces. The main characteristics, and potential advantages and disadvantages of each interface are described. Portable volume-limited or pressure-limited ventilators are available for home noninvasive ventilation. As with critical care ventilators, home mechanical ventilators are capable of delivering a variety of modes of ventilation. Furthermore, they are lightweight and economical. Technical aspects of ventilator circuits are also discussed here and some practical considerations about selection and maintenance of materials are proposed.

CONCLUSIONS

Although major technical advances have been made, optimal delivery of noninvasive ventilation requires knowledge of, and experience with, the application of the equipment used.

Efficacy of Glossopharyngeal Breathing for a Ventilator-Dependent, High-Level Tetraplegic Patient After Cervical Cord Tumor Resection and Tracheotomy

This case study was undertaken to describe the use and limitations of glossopharyngeal breathing (GPB) by a ventilator-dependent, tracheotomized patient after cervical tumor resection. A 6-yr, 8-mo-old, tracheotomized, ventilator-dependent boy, after cervical tumor resection, learned GPB on his own and used it for ventilator-free breathing. Over the next 16 yrs, his GPB efficacy improved to the point that, with a vital capacity of 670 ml, his GPB maximum single-breath capacity increased to 3300 ml. This was limited by the fact that at 2.9 l of lung volume, air began to leak around the tracheostomy tube walls and out of the stoma. Still, GPB permitted up to 12 hrs/day of ventilator-free breathing. Measurements of assisted peak cough flow and GPB lung insufflations exceeding vital capacity are the main measures that demonstrate adequate tube fit to permit effective GPB in the presence of an indwelling tracheostomy tube.

Successful pregnancies for ventilator users

This case series describes full-term pregnancies despite no autonomous ability to breathe due to poliomyelitis or ventilatory insufficiency due to severe kyphoscoliosis. Three women with postpoliomyelitis who were continuously dependent on noninvasive intermittent positive pressure ventilation and one woman who developed ventilatory insufficiency due to severe kyphoscoliosis became pregnant and delivered healthy, full-term babies. They had vital capacities of 240, 250, 280 (5% of normal), and 880 ml (14% of normal), respectively, when becoming pregnant. The up to continuous use of noninvasive intermittent positive pressure ventilation can permit the natural completion of pregnancies of women with little or no ability to breathe unaided.

Mechanical insufflation-exsufflation: pressure, volume, and flow relationships and the adequacy of the manufacturer's guidelines

OBJECTIVE

Pulmonary complications of neuromuscular disease can be averted by increasing peak cough flows with the use of a forced exsufflation device. The purpose of this study was to examine the pressure, volume, and flow relationships for a range of settings generated by this device, and compare them with clinically efficacious values and the manufacturer's guidelines.

METHODS

The In-exsufflator was connected to a standard lung model. The resulting forced deflation volumes, flows, and pressures were averaged over 10 cycles at each setting.

RESULTS

The set insufflation pressures significantly correlated with the generated insufflation pressures and volumes and the exsufflation volumes and flows. Increasing set insufflation time significantly increased generated insufflation pressures, flows, and volumes and exsufflation volumes. Increasing set exsufflation time did not significantly increase generated exsufflation flows. At set pressures of 40 to -40 cm H2O, insufflation time of 3 sec, and exsufflation time of 2 sec, the exsufflation flow was 4.09 l/sec. A plateau insufflation volume of 3.8 l was reached after 4.9 sec of insufflation.

CONCLUSIONS

In-exsufflator performance was very consistent. Its clinical effectiveness can be explained by its generation of exsufflation flows >2.7 l/sec. Increasing insufflation times more than exsufflation times is more important for optimal function. Current manufacturer use guidelines may not yield optimal exsufflation flows.

Amyotrophic lateral sclerosis: prolongation of life by noninvasive respiratory AIDS

STUDY OBJECTIVE

To describe prolongation of survival in patients with amyotrophic lateral sclerosis (ALS) by continuous noninvasive intermittent positive-pressure ventilation (NPPV) and mechanically assisted coughing (MAC) using oximetry as feedback.

SETTING

A retrospective review of ALS patients visiting one center from 1990 to 2000.

DESIGN

Patients were trained in mouthpiece and nasal NPPV when symptomatic for hypoventilation, and trained in MAC with oximetry feedback when assisted peak cough flow (PCF) levels decreased to < 270 L/min. Survival was considered to be prolonged when full-time NPPV was required with limited ventilator-free breathing tolerance.

RESULTS

Of 101 patients who met the criteria for access to NPPV and MAC, 15 have not yet used them, and 11 patients with severe bulbar muscle dysfunction died without ever successfully using them. Three patients used NPPV full-time, and oximetry and MAC episodically, but did not yet require ongoing NPPV. Eighteen used NPPV part-time for a mean (+/- SD) duration of 3.8 +/- 4.1 months. Nineteen others underwent tracheotomy after 4.7 +/- 4.5 months of receiving part-time NPPV. Sixteen patients used part-time NPPV for 17.5 +/- 13.0 months (maximum, 25 months), then full-time NPPV for 14.1 +/- 12.6 months (maximum, 40 months) before undergoing tracheotomy. Nineteen patients used part-time and full-time NPPV for 25.2 +/- 19.8 months (maximum, 114 months) and 17.5 +/- 13.3 months (maximum, 87 months), respectively, without undergoing tracheotomy. Ten of these NPPV users died once bulbar dysfunction became severe.

CONCLUSION

We conclude that up to continuous use of NPPV, along with MAC when needed, can permit prolonged survival and delay the need for tracheotomy for a significant minority of ALS patients by > 1 year.

Prevention of pulmonary morbidity for patients with neuromuscular disease

STUDY OBJECTIVE

To evaluate the effects of a respiratory muscle aid protocol on hospitalization rates for respiratory complications of neuromuscular disease.

DESIGN

A retrospective cohort study.

METHODS

A home protocol was developed in which oxyhemoglobin desaturation was prevented or reversed by the use of noninvasive intermittent positive-pressure ventilation and manually and mechanically assisted coughing as needed. The patients who had more than one episode of respiratory failure before having access to the protocol were considered to have had preprotocol periods (group 1). Other patients were given access to the protocol when their assisted peak cough flows decreased to < 270 L/min before any episodes of respiratory distress (group 2). The number of hospitalizations and days hospitalized were compared longitudinally for preprotocol and protocol access periods (group 1). In addition, avoided hospitalizations were identified as "episodes" of need for continuous ventilatory support and desaturations reversed by assisted coughing that were managed at home. Data were segregated by access to protocol and by extent of baseline ventilator use.

RESULTS

Of the 47 group 1 patients with preprotocol periods who have subsequently had episodes, 10 had episodes before requiring ongoing ventilator use. They had 1.06 +/- 0.84 preprotocol hospitalizations per year per patient and 20.76 +/- 36.01 hospitalization days per year per patient over 3.42 +/- 3.36 years per patient vs 0.03 +/- 0.11 hospitalizations per year per patient and 0.06 +/- 0.20 hospitalization days per year per patient with protocol use over 1.94 +/- 0.74 years per patient. Of these 47 group 1 patients, 33 eventually required part-time ventilatory aid and, using the protocol as needed, had 0.08 +/- 0.17 hospitalizations per year per patient and 1.43 +/- 3.71 hospitalization days per year per patient over 3.91 +/- 3.50 years per patient, as opposed to 1.40 +/- 1.96 hospitalizations per year per patient and 20.14 +/- 41.15 hospitalization days per year per patient preprotocol and preventilator use over 5.89 +/- 6.89 years per patient. Twelve patients in group 1 eventually required continuous noninvasive ventilation and, using the protocol as needed, had 0.07 +/- 0.14 hospitalizations per year per patient and 0.39 +/- 0.73 hospitalization days per year per patient over 5.35 +/- 5.10 years per patient by comparison with 0.97 +/- 0.74 hospitalizations per year per patient and 10.39 +/- 8.66 hospitalization days per year per patient over 2.18 +/- 1.91 years per patient preprotocol and preventilator use. For the 94 patients overall when having access to the protocol, 1.02 +/- 0.99 hospitalizations per year per patient were avoided by 14 patients before requiring ongoing ventilator use over 4.82 +/- 1.61 years, 0.99 +/- 1.12 hospitalizations per year per patient were avoided by 73 part-time ventilator users over 3.21 +/- 3.15 years, and 0.80 +/- 0.85 hospitalizations per year per patient were avoided by 31 full-time ventilator users over 4.78 +/- 4.88 years. All preprotocol and protocol rate comparisons were statistically significant at p < 0.004.

CONCLUSION

Patients have significantly fewer hospitalizations per year and days per year when using the protocol as needed than without the protocol. The use of inspiratory and expiratory aids can significantly decrease hospitalization rates for respiratory complications of neuromuscular disease.

Evaluation and rehabilitation of patients with adult motor neuron disease

Adult motor neuron disease (amyotrophic lateral sclerosis [ALS]) is a neurodegenerative disorder characterized by loss of motor neurons in the cortex, brain stem, and spinal cord, manifested by upper and lower motor neuron signs and symptoms affecting bulbar, limb, and respiratory musculature. Clinically, the disease course is characterized by progressive weakness, atrophy, spasticity, dysarthria, dysphagia, and respiratory compromise, ultimately resulting in death or mechanical ventilation in the vast majority of patients. Patterns of presentation and pathological features of the disease, along with clinical and electrophysiologic criteria for diagnosis, are discussed in this review. Since 8% to 22% of patients survive more than 10 years without ventilator use, meticulous medical and rehabilitation management is extremely important to ensure optimal health and quality of life in these patients. Major issues in the care of individuals with ALS include weakness and spasticity, impairments in activities of daily living and mobility, communication deficits and dysphagia in those with bulbar involvement, respiratory compromise, fatigue and sleep disorders, pain, and psychosocial distress. Research in ALS changes rapidly, but is currently focused on potential etiologic factors such as glutamate excitotoxicity, role of oxidative stress, autoimmunity to calcium channels, and cytoskeletal abnormalities, as well as related treatment initiatives including glutamate modulators, neurotrophic factors, antioxidants, antiapoptotic factors, and gene therapy. Recently, mutations in the gene encoding Cu/Zn superoxide dismutase were identified in a subset of familial ALS patients. Riluzole, a glutamate antagonist and Na-channel blocker, became the only drug currently approved for treatment of ALS after studies showed a small positive effect on survival. Until a definitive treatment or cure for ALS is found, the multifaceted rehabilitation team approach remains the best hope for improving health and survival in this devastating illness.

Cardioprotection for Duchenne's muscular dystrophy

PURPOSE

To explore the use of neuroendocrine monitoring for more timely diagnosis of dilated cardiomyopathy (DCM) in Duchenne's muscular dystrophy (DMD) and to determine the effects of angiotensin-converting enzyme inhibitors (ACEI) and beta-blockers on neuroendocrine levels, left ventricular diastolic diameter (LVDd), ejection fraction, and mortality rate on DMD.

METHODS

Eighty-five patients with DMD underwent yearly cardiac monitoring including neuroendocrine screening. Eleven patients had symptoms of DCM develop once plasma neuroendocrine levels increased. At this point the patients received ACEI for 9 to 62 months (35.8 +/- 18.4 months) and beta-blockers for 7 to 60 months (31.6 +/- 20.1 months).

RESULTS

The combination of ACEI and beta-blockers relieved symptoms and signs of heart failure in all 11 patients and significantly reduced atrial natriuretic protein (ANP) levels from 197.5 +/- 152.1 pg/mL to 25.5 +/- 16.2 pg/mL ( P <.002) at 15.5 +/- 8.2 months, brain natriuretic protein from 523.8 +/- 434.8 pg/mL to 59.3 +/- 24. 2 pg/mL ( P <.05) at 12.2 +/- 3.1 months (data complete for 5 patients), norepinephrine levels from 1114 +/- 689 pg/mL to 360 +/- 257 pg/mL at 20.5 +/- 9.6 months for 11 patients (P =.001), and LVDd from 65.9 +/- 9.2 mm to 63.3 +/- 6.3 mm (P =.15) at 15.0 +/- 7.4 months for 10 patients, including 3 for whom the LVDd increased by 2 to 6 mm. The combination increased left ventricular ejection fraction (LVEF) from 25.1% +/- 9.2% to 36.5% +/- 5.8% (P <.001) at 17.1 +/- 11.0 months for 10 patients. For 9 of the patients ANP levels remained lower throughout the 36.8 +/- 20.1 month course of the follow-up. Two patients had sudden severe re-elevations of ANP levels just before death from congestive heart failure after 44 and 23 months of therapy, respectively.

CONCLUSION

Neuroendocrine level monitoring can assist in the diagnosis of DCM in patients with DMD. Combination therapy with ACEI and beta-blockers can significantly decrease neuroendocrine activation and LVDd and reverse symptoms and signs of congestive heart failure for patients with DMD.