INTRODUCTION — Patients with neuromuscular or chest wall disease, or ventilatory pump failure for any reason, can develop severe hypercapnia, difficulty clearing airway secretions with ventilation-perfusion mismatching, and ultimately acute on chronic respiratory failure. Noninvasive ventilatory assistance is usually first needed at night but with progressive muscle dysfunction, patients can become dependent on continuous full ventilator setting noninvasive ventilatory support (CNVS) and require the use of mechanical insufflation-exsufflation (MIE) to expulse airway secretions during intercurrent respiratory tract infections, and for those with severe dysphagia and aspiration, multiple times per day. Indeed, virtually all patients with neuromuscular disorders (NMDs) caused by myopathic or lower motor neuron lesions can be managed noninvasively indefinitely whereas patients with upper motor neuron lesions, such as many of those with bulbar amyotrophic lateral sclerosis (ALS), develop stridor and spastic upper airway collapse that can render MIE ineffective [1] and necessitate tracheotomy for continued survival [2,3].
The use of CNVS will be reviewed here. Nocturnal ventilatory assistance/support, the types of ventilators, and the role of tracheostomy are discussed separately (see "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation"). In addition, intubated patients and those dependent on up to continuous tracheostomy mechanical ventilation (CTMV) can be extubated [4] or decannulated to CNVS and MIE [5].
INDICATIONS — Symptomatic respiratory muscle dysfunction, often with alveolar hypoventilation is the primary indication for ongoing nocturnal ventilatory assistance. Typical symptoms include fatigue, exertional dyspnea, reduced appetite, inattention, and impaired concentration and memory. Initially, hypoventilation occurs during rapid eye movement (REM) sleep and is manifest by oxyhemoglobin desaturation and hypercapnia. Hypoventilation subsequently extends throughout sleep and eventually into daytime hours [3,6]. (See "The effect of sleep in patients with neuromuscular and chest wall disorders".)
However, infants with paradoxical breathing, whether hypercapnic or not and irrespective of any apnea-hypopnea indices, require sleep nasal noninvasive ventilatory support (NVS) to reverse their paradoxical breathing and ease the symptoms of frequent arousals with flushing, perspiration, and tachypnea and to avoid pectus and other chest wall deformities and to promote lung growth [7].
Symptoms (eg, dyspnea, somnolence, fatigue) and blood gas derangements related to chronic hypoventilation are typically relieved by nocturnal noninvasive positive pressure ventilatory assistance/support. While the effect of limiting the application of NVS to nocturnal-only does not result in markedly prolonged survival [8], clinicians who understand how to accommodate the patient's eventual need for up to continuous NVS (CNVS) report decades of prolonged survival for patients with ventilatory pump failure. As the need for ventilatory support extends into daytime hours and is ultimately needed continuously, the properly equipped and informed patient can use it indefinitely as an alternative to tracheostomy ventilation (picture 1).
TYPES — The respiratory muscles can be aided by manually or mechanically applying forces to the body or delivering intermittent pressure to the airway. Some devices assist inspiratory muscles, whereas others facilitate coughing, predominantly by assisting expiratory muscles. Specific types of useful devices include the following [9,10]:
●Devices that apply intermittent pressure changes directly to the airway (eg, mouthpiece and nasal noninvasive ventilatory support [NVS])
●Body ventilators (eg, intermittent abdominal pressure ventilator [IAPV] and chest shell ventilator) that apply positive or negative pressures to the body.
●Manual and mechanical exsufflation techniques that apply forces directly to the body to mechanically displace respiratory muscles to increase cough flows (see 'Cough assistance' below)
The most useful of the daytime inspiratory aids are mouthpiece and nasal NVS and the IAPV [11,12]. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Patient selection and alternative modes of ventilatory support".)
Mouthpiece NVS — A convenient method of daytime ventilatory support involves the delivery of volume preset ventilation via a 15 mm angled mouthpiece, a 22 mm mouthpiece, or via a wide plastic straw kept adjacent to the mouth for easy access to supplement tidal volumes as needed. Active ventilator circuits on portable ventilators that can be volume preset so that users can retain several consecutively delivered volumes for active lung volume recruitment (LVR) using assist/control mode NVS without expiratory positive airway pressure. Intermittent mouthpiece NVS has been used in conjunction with nocturnal nasal or lip cover phalange NVS for up to 33 years of continuous noninvasive ventilatory support (CNVS) for patients with Duchenne muscular dystrophy (picture 2), 66 years for post-polio patients, 26 years for patients with Werdnig-Hoffmann disease (spinal muscular atrophy type 1), and 38 years for high level spinal cord tetraplegia, as well as for other conditions [13-16].
In one report, 108 patients with Duchenne muscular dystrophy required CNVS including daytime mouthpiece NVS and nocturnal nasal/oronasal NVS for a mean of nine years and up to 29 years. Mouthpiece NVS maintained normal alveolar ventilation for many patients with as little as 0 mL of slow vital capacity (VC) [16].
Mouthpiece NVS has also been used nocturnally since 1954 with or without a lip cover phalange and straps to retain the mouthpiece. Interface designs that deliver air via both the mouth and nose can provide closed systems of CNVS with minimal strap/skin pressure (picture 3).
Nasal NVS — Nasal NVS is used during daytime hours if neck rotation or lip strength is not adequate for the patient to grab a mouthpiece (picture 4). During periods of nasal congestion, oronasal interface NVS must usually be used. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation".)
Intermittent abdominal pressure ventilation — Intermittent abdominal pressure ventilation is provided by pneumatic intermittent abdominal pressure ventilators (IAPVs) that consist of a wide belt or girdle with an inflatable sac inside it. The sac is cyclically inflated by air delivered from a portable positive pressure ventilator. Sac inflation compresses the abdomen, and the resulting movement of the abdominal contents elevates the diaphragm forcing expiration to a volume below the functional residual capacity. With sac deflation, the diaphragm returns to its resting position and air enters the patient's upper airway. The IAPV is only effective when the patient is in the sitting position, or at least, over 30 degrees from the horizontal. The patient can add to IAPV-provided volumes with spontaneous tidal volumes or by glossopharyngeal breathing (GPB). (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Patient selection and alternative modes of ventilatory support", section on 'Abdominal respirators'.)
COUGH ASSISTANCE — The ability to generate sufficient expiratory flow for effective coughing is the most important factor permitting use of CNVS indefinitely as an alternative to tracheostomy ventilation [16]. There are both manual and mechanical methods to create effective cough flows.
An effective cough involves a deep inspiration or assisted insufflation, followed by the creation of sufficient thoracoabdominal pressure to generate an explosive decompression and high expiratory flows. Aiding expiratory muscles is required to optimize cough peak flow rates [17].
For patients with VCs less than 1.5 liters, air stacking or a deep insufflation (active lung volume recruitment [LVR]) should precede cough. A manual resuscitator (eg, Ambu bag) or ventilator can be used to deliver preset volumes of air consecutively for air stacking [17,18]. Volumes are delivered to approach a maximum lung insufflation capacity, that is, until the glottis can hold no additional air. Volume cycling ventilation permits the stacking of air volumes to increase cough peak flows and are, therefore, preferred for assisted ventilation over pressure-cycling which does not permit air stacking [17].
Manually assisted cough — A forceful manual thrust to the abdomen directed posterior and cephalad manually assists coughing but may not be sufficiently effective in the presence of severe scoliosis or severely impaired bulbar-innervated muscles.
It should also be used cautiously following meals due to the risk of aspiration and the thrusts avoided following abdominal trauma.
Mechanical insufflation-exsufflation — The most effective method for generating effective cough flows for clearing airway debris is the use of mechanical insufflation-exsufflation (MIE). This can be used in combination with the manual thrusts, however, when used via the upper airways MIE at positive and negative pressures of 50 to 60 cm H2O to insufflate then exsufflate the lungs concomitant thrusts usually do not further increase the exsufflation flows (MIE-EF). Following insufflation, the exsufflation occurs in 0.02 seconds to generate approximately 10 L per second of MIE-EF. The goal is to fully inflate then fully empty the lungs in four to six seconds to clear airway debris while avoiding both hypo- and hyperventilation.
The MIE can also be used for passive LVR for patients unable to air stack such as whenever glottis strength is inadequate to hold consecutively delivered air volumes. Thus, MIE can also be used for LVR as well as to increase cough flows to clear airway mucus [3]. When mucus plugs cause oxyhemoglobin desaturation, clearance of the secretions by MIE can increase VC and oxyhemoglobin saturation (SpO2). In one study, a 55 percent increase in VC was noted following MIE in congested patients with neuromuscular conditions [19]. In another study, MIE improved VC by 15 to 50 percent and normalized pulse SpO2 in patients with neuromuscular disease who were in acute respiratory failure [20]. When MIE is applied through translaryngeal or tracheostomy tubes it must be used at 60 to 70 cm H2O pressure because of the pressure drop off across the narrow gauge tubes. Its use via invasive tubes can eliminate the need for deep airway suctioning over which it is greatly preferred by patients and can return ambient air oxyhemoglobin saturation to normal in preparation for successful extubation or decannulation [3,5,21]. No serious complications have been reported to result from the use of MIE [10,22].
Glossopharyngeal breathing — Both inspiratory and, indirectly, expiratory muscle activity can be assisted by glossopharyngeal breathing (GPB) [23]. GPB is described in detail elsewhere.
GPB can generate volumes for coughing that approach the deep lung volumes achieved by air stacking (2 to 3 L over vital capacity), depending on the number of "gulps" taken and their efficiency. Many patients have no ventilator free breathing ability other than by GPB which many CNVS dependent patients can use all day long entirely off of ventilator use. It can also provide security in the event of sudden ventilator failure. We have had CNVS dependent patients with 0 mL of VC awaken from sleep using GPB to discover that their ventilators were no longer functioning.
PATIENT SELECTION — Patients with the diagnoses listed in the table (table 1) are often candidates for the use of noninvasive ventilatory support/continuous noninvasive ventilatory support (NVS/CNVS) and mechanical insufflation-exsufflation (MIE). Ventilatory support either in the acute setting or on a long-term basis can usually be managed by up to CNVS as an alternative to endotracheal intubation or tracheostomy if the following criteria are met:
●The patient is mentally competent, cooperative, and not using heavy sedation or opiates.
●CNVS and MIE can return ambient air oxygen (O2) saturation over 94 percent. Supplemental oxygen depresses ventilatory drive increasing hypercapnia and rendering the pulse oximeter useless for monitoring decreases in alveolar ventilation and increases in secretions, both of which cause the SpO2 to decrease below 95 percent. Supplemental O2 is both unnecessary in the absence of severe intrinsic lung disease and potentially harmful [24].
●There is sufficient upper airway patency for MIE to be effective in expulsing airway secretions, that is, MIE-EF over approximately 150 to 200 L/minute [25]. This is invariably the case, except for upper motor neuron (UMN) bulbar muscle impairment.
●There is no significant risk of substance abuse or uncontrollable seizures.
PRACTICAL ASPECTS — Patients with neuromuscular and chest wall disease usually tolerate alveolar hypoventilation until acute respiratory distress is provoked by an otherwise benign upper respiratory tract infection, or possibly by an elective surgical procedure requiring general anesthesia. Ventilator-free breathing may or may not be possible during or following the acute episode.
To avoid the need for intubation, patients with ventilatory pump failure and diminished vital capacity (VC) should be trained in NVS and mechanical insufflation-exsufflation (MIE) before any such episode occurs, and should use them sufficiently aggressively, NVS continuously and MIE up to every 15 to 30 minutes, around-the-clock if necessary, to maintain oxyhemoglobin saturation (SpO2) over 94 percent until it remains normal without MIE or possibly CNVS. Thus, home monitoring of patients requiring daytime NVS and MIE should include monitoring of pulse oxyhemoglobin saturation during intercurrent respiratory tract infections.
●Pulse oxyhemoglobin saturation – Ambient air SpO2 monitoring is useful to gauge the extent of diurnal or nocturnal hypoventilation and the extent of airway congestion. An oximeter that can average data hourly during nocturnal monitoring is useful to quantitate the efficacy of continuous NVS (CNVS) during sleep [3,11].
Patient monitoring also should include regular clinic evaluations of the following:
●VC – VC is measured in sitting and supine positions and with thoracolumbar bracing on and off (if applicable).
●The maximum insufflation capacity – The maximum insufflation capacity (MIC) represents the maximum quantity of air that the patient can hold with a closed glottis by air stacking of consecutively delivered air volumes, or by glossopharyngeal breathing. The greater the MIC, the greater the cough peak flow rates and the potential to increase voice volume and maintain pulmonary compliance (by decreasing microatelectasis and providing a greater range of motion to the lungs and chest wall articulations).
●Capnography and transcutaneous carbon dioxide (CO2) monitoring is useful for demonstrating diurnal and nocturnal hypercapnia. Daytime hypercapnia (>44 mmHg) can signal severe sleep hypercapnia and oxyhemoglobin desaturation below 95 percent.
●Cough peak flow rates – Cough peak flow rates, both unassisted and assisted by air stacking to deep lung insufflation followed by abdominal thrust, are measured using a peak flow meter (eg, Assess peak flow meter) or any digital spirometer that measures expiratory flow. Effective rates range from 300 to 1200 L/minute [26].
Preventing pneumonia — The risk of developing pneumonia during an upper respiratory tract infection is inversely related to cough peak flow rates and the ability to use manually assisted coughing and MIE.
●Patients are at increased risk for developing pneumonia during an upper respiratory tract infection when cough peak flow rates are below 300 L/minute and pneumonia appears to be inevitable, when even manually assisted coughing rates are below 160 L/minute unless using MIE effectively. (See 'Mechanical insufflation-exsufflation' above.)
●If the VC is relatively preserved, typically 2 L or more, a low cough peak flow rate is indicative of severe bulbar muscle dysfunction or airway obstruction from another etiology. Although manually assisted coughing and MIE can be helpful, significant benefit is often precluded by inability to maintain upper airway patency in order to achieve the expiratory flows (MIE-EF) necessary to eliminate airway secretions. This happens almost exclusively in bulbar amyotrophic lateral sclerosis (ALS) and patients with other upper motor neuron and central nervous system diseases.
●If the VC is below 40 percent of predicted and assisted cough peak flow rates are below 300 L/minute, the patient is at risk for pneumonia and respiratory failure when VC and cough flows decrease further during upper respiratory tract infections. This can usually be prevented by an effective protocol of CNVS and MIE [16,27].
Protocol — At our institution, patients obtain an oximeter and have rapid access to MIE when their maximum assisted cough peak flows are below 270 to 300 L/minute. Symptomatic patients with diminished VC use NVS for sleep and increase use through the day when they are ill. A volume-cycling ventilator is used for ventilatory assistance because of the need to air stack for manually assisted coughing, to increase voice volume and maintain lung compliance [3,27].
The patient is instructed to maintain peripheral oxygen saturation (SpO2) always greater than 94 percent without the aid of supplemental oxygen in the home. The patient is also told that a SpO2 below 95 percent can result from three possible causes: hypoventilation, bronchial mucus plugging, or intrinsic lung disease. The last of these is usually from atelectasis or pneumonia which mainly results from ineffective airway mucus clearance.
When NVS is used, oxyhemoglobin desaturation is usually due to mucus plugging, not hypoventilation. The SpO2 returns to baseline as the airway mucus is eliminated by some combination of assisted coughing and MIE. Properly equipped and instructed patients with MIE very infrequently develop pneumonia or require hospitalization for respiratory management. As an example, our center has 15 adult patients with spinal muscular atrophy type 1 (Werdnig-Hoffman disease) who have been CNVS-dependent without tracheostomy tubes since infancy, but none have been hospitalized and intubated in over 10 years, and when younger and intubated with little or no spontaneous breathing ability, were always extubated to CNVS and MIE (picture 4). As the infections resolve, patients usually wean back to their pre-morbid NVS regimen. In contrast, such patients who undergo tracheotomy typically remain continuously ventilator-dependent indefinitely (CTMV).
Gradually, as long-term NVS users become symptomatic from alveolar hypoventilation despite nocturnal use of NVS they extend NVS use into daytime hours and eventually progress to CNVS. The extent of daytime use can be guided by a protocol of oximetry feedback. The patient is provided with a 15 mm angled mouthpiece for convenient daytime ventilatory support. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation".)
Tracheostomy to noninvasive ventilation — Patients with ventilatory pump failure (VPF) who have a tracheostomy for mechanical ventilation are candidates for tube decannulation to up to CNVS if they meet the criteria in the table (table 2). Specifically, patients should have sufficiently intact bulbar musculature to protect their airways to maintain SpO2 at 95 percent or higher in ambient air with or without ventilator use. This includes patients with spinal cord injury, previous poliomyelitis, spinal muscular atrophy, and most myopathies including Duchenne muscular dystrophy. Even individuals with non-bulbar ALS who undergo tracheostomy during an episode of acute respiratory failure have improved quality of life with decannulation and transition to NVS/CNVS and MIE.
The following are key steps in the transition from tracheostomy to noninvasive aids:
●Before decannulation, CNVS should be used via mouthpieces and nasal interfaces for at least one week with the tube capped or a tracheostomy button placed. Various nasal interfaces should be tried to optimize seal and comfort (picture 5 and picture 6 and picture 7). Note that when used with an active ventilator circuit, one with an exhalation valve, the exhalation ports of these interfaces must be covered or capped.
●NVS may be required continuously (CNVS) but must be used without any supplemental oxygen yet with oxygen saturation over 94 percent during waking hours.
●Once criteria are met, the tracheostomy tube is removed [5,16,27,28]. A temporary tracheostomy button, or sometimes, use of a cuffless fenestrated tube can be placed in the tracheostomy site to permit the patient to continue to practice NVS without letting the ostomy close and without the partial airway obstruction that would be caused by practicing NVS with the continued presence of a tracheostomy tube. If the patient is an outpatient and using tracheostomy mechanical ventilation, whether part-time or continuously, they should use NVS for at least one week before the button or cuffless fenestrated tracheostomy tube is permanently removed and a pressure dressing is placed over the ostomy. If an inpatient, then the tube can be left out and the dressing placed and conversion to NVS done in the hospital itself. A tracheostomy button or at times use of a cuffless fenestrated tube allows the patient to practice NVS as needed before permanent ostomy closure.
●Regular clearance of airway secretions by manual assisted coughing and MIE via a mouthpiece or oronasal mask continues after decannulation of the trachea and is critical for any oxygen desaturations below 95 percent to return oxygen saturation to normal.
●If a tracheostomy button is used, it is useful to document oxygen saturation and carbon dioxide levels during sleep using capnography or transcutaneous carbon dioxide monitoring. Once adequate nocturnal SpO2 is documented, the button can be removed and the tracheostomy site allowed to close [5]. An airtight dressing is applied over the site until it is closed [5]. At our center, we no longer use tracheostomy buttons because with a comfortable interface CNVS has always been successful for patients with ventilatory pump failure.
Extubation to CNVS — Patients are extubated to CNVS to wean rather than weaned to be extubated. When a patient receiving mechanical ventilation via translaryngeal tube is unable to be weaned from ventilatory support, endotracheal tube removal and transition to CNVS and MIE permit extubation without resort to tracheotomy [4]. Upon extubation the patient inexperienced in NVS first uses nasal CNVS but is then transitioned to mouthpiece and/or nasal NVS by which they can take fewer and fewer mouthpiece ventilations as tolerated to wean themselves. Patients usually wean back to their pre-intubation NVS regimen, often to nocturnal-only NVS provided that their VC exceeds 250 mL. Patients with lower VCs usually continue to require ongoing CNVS. No weaning schedule is imposed on the patient, and the anxiety inherent in the "standard" weaning approaches is avoided. Patients know that they can take assisted breaths anytime they feel the need, and can use feedback from pulse oximetry to guide ventilator use [3,4,29-31]. (See "Initial weaning strategy in mechanically ventilated adults".)
In one study, 155 of 157 intubated patients who refused tracheostomy and who failed spontaneous breathing trials both before and after extubation were extubated to full ventilator setting CNVS and MIE [4]. Ninety-three who had failed extubations were transferred to our center specifically for extubation to CNVS. All "unweanable" patients, even with no measurable cough flows, were successfully extubated to CNVS. Approximately 80 percent of first extubation attempts were successful, but all were ultimately successful on second or third attempts.
Deflation of the cuff — Cuff deflation is used to allow patients to talk while mechanically ventilated through a tracheostomy tube, to practice NVS for decannulation, and to prevent complications from cuff pressure on the trachea. When deflating a cuff, the ventilator insufflation volume should be increased, often to 1500 mL or more, to compensate for air leakage through the upper airway. In general, the delivered volumes are increased until they generate the same positive inspiratory pressures that were generated by the smaller delivered volumes before cuff deflation. The patient is encouraged to learn to control and use the insufflation "leak" of air across the vocal cords for speech. The leak also carries airway debris up to the mouth.
If the leak is inadequate for speech, a cuffless tube can be used or the tracheostomy tube downsized. Cuff removal, however, prevents optimal MIE for elimination of airway secretions. In contrast, a wider gauge tube should be placed if there is too much leakage for effective alveolar ventilation, as indicated by decreases in SpO2. In general, patients who can speak with deflated cuffs are strong candidates to have their tracheostomy tubes removed in favor of NVS.
INDICATIONS FOR TRACHEOSTOMY — No extent of inspiratory or expiratory muscle failure or ventilator dependence is in itself an indication for tracheotomy. The only indication for tracheostomy for patients with ventilatory pump failure is inability to cooperate with NVS or to prevent the aspiration of airway secretions that cause a drop in the peripheral oxygen saturation (SpO2) below 95 percent despite NVS and MIE. Generally speaking, this only occurs for patients with advanced upper motor neuron (UMN) bulbar amyotrophic lateral sclerosis such that mechanical insufflation-exsufflation flows (MIE-EF) decrease to little more than 100 L/minute [1]. Since many patients with no measurable vital capacity (VC) depend on CNVS indefinitely, tracheotomy is not necessary for long-term ventilatory support. However, if airway secretions cause chronic congestion that MIE cannot reverse, whether or not the patient requires ventilatory assistance/support, a tracheostomy tube can become necessary for survival. While it is important to review with the patients their goals and preferences for ongoing medical care and ventilatory support, and discuss these issues with the patient and family over a period of time, it should be understood that with over 2000 patients using NVS/CNVS, with 109 of our patients among the 335 CNVS dependent ALS patients of 10 other NVS centers, none of these patients have ever volitionally ceased using CNVS to die and few with respiratory symptoms have failed to tolerate nasal NVS when initially offered to them [32]. Also, no matter how vehemently patients reject tracheotomy as a future possibility, when intubated and facing death many if not most change their minds. When patients are told that if intubated they can probably be extubated to CNVS and MIE without resort to tracheotomy, they usually accept intubation.
CNVS dependent patients who require intubation for acute respiratory failure can usually be extubated back to CNVS once their lung disease has cleared [4,29]. Avoidance of tracheostomy eliminates the risk of glottic and subglottic stenosis and other serious and potentially fatal complications of tracheostomy [33]. Long-term tracheostomy tube cuff inflation is also associated with the following problems:
●Increased risk of trachiectasis and tracheal perforation
●Prevention of effective verbalization
●Impaired elevation of the larynx and esophageal dysfunction during swallowing
●Increased risk of aspiration [29,34].
PITFALLS — The term "NIV" for noninvasive ventilation has come to be synonymous with continuous positive airway pressure (CPAP) and low spans of bi-level PAP. While the former is useless as a respiratory muscle aid, bi-level PAP assists lung ventilation as a function of the drive pressure (span) being used. In order to avoid endotracheal intubation, patients with severe respiratory muscle dysfunction often need to use full ventilator setting volume or pressure preset ventilatory support (CNVS) which can be provided by delivering bi-level at spans over 15 cm H2O or by intermittent positive pressure ventilation without expiratory PAP or positive end-expiratory pressure (PEEP). Since the expiratory PAP is counterproductive for administering ventilatory assistance [35], intermittent positive pressure ventilation without expiratory positive airway pressure (EPAP) or PEEP, whether volume or pressure preset, is preferred for these patients. Full-setting CNVS normalizes alveolar ventilation, more fully rests inspiratory muscles, optimizes lung volume recruitment, and augments cough flows. A publication demonstrated for bulbar ALS that any EPAP at all is counterproductive [35]. In fact, bulbar ALS patients on pressure support of 12 cm H2O with no PEEP/EPA had less ventilator autocycling, central sleep apneas, and glottis closure than patients on 5 cm H2O.
Frequently, patients who are able to walk (ie, myotonic dystrophy or kyphoscoliosis) do not use noninvasive ventilatory support (NVS) sufficiently during daytime hours to normalize alveolar ventilation. These patients have repeated respiratory complications until they spend most of their time in wheelchairs from which they can more conveniently use mouthpiece NVS and CNVS.
The clinician is often tempted to prescribe oxygen therapy. However, if arterial blood gases can be normalized by NVS and MIE, then oxygen therapy is not needed and can be hazardous. When oxygen supplementation is used along with NVS, it decreases the efficiency of nocturnal NVS, increases the risk of pulmonary complications, and exacerbates hypercapnia [24]. Domiciliary supplemental oxygen should not be used for patients with ventilatory pump failure except for those with advanced ALS and UMN bulbar impairment who need, but refuse, tracheotomy for secretion management and ventilation.
OTHER CONSIDERATIONS — Many of the same general interventions and cautions for patients with primary lung disease are also applicable to patients with ventilatory pump failure. Patients are cautioned to avoid extremes of temperature, humidity, fatigue, crowded areas, or exposure to respiratory tract pathogens, sedatives, supplemental oxygen, and opiates. Patients should be advised to receive influenza and pneumococcal vaccines. They should also be instructed about using NVS/CNVS and MIE in the event of an upper respiratory tract infection or post-op for general anesthesia. Diaphragm pacing is ineffective and often harmful for patients with all neuromuscular diseases including amyotrophic lateral sclerosis [36,37].
Nutrition — Heavy meals should be avoided and obesity prevented or managed. General weight charts are not applicable to these patients. However, a specific weight chart has been developed for patients with Duchenne muscular dystrophy (DMD) [38]. A useful equation for estimating caloric need for DMD patients up to 20 years of age is [39]:
Daily energy intake (Kcal) = 2000 – [Age (years) × 50]
As bulbar muscles weaken, these patients must often limit oral intake to high calorie, thick liquids. While some patients with neuromuscular disease eventually require indwelling gastrostomy tubes for enteral nutrition, this can be greatly delayed by NVS. As a patient’s vital capacity (VC) decreases, the patient develops tachypnea to 40 to 50 breaths per minute and the patient has only approximately one second to swallow, rendering swallowing unsafe, thereby reducing their appetite; this phenomenon is exacerbated by hypercapnia that is frequently present. By administering mouthpiece NVS at 1000 to 1500 mL volume, normal minute ventilation can be provided by only grabbing the mouthpiece four or five times a minute, giving patients 10 to 15 seconds to swallow their food [40]. By using NVS during meals only 15 percent of patients with DMD ever require gastrostomy tubes whereas close to 100 percent using TMV have them placed. These tubes, though, when needed, should only be placed under local anesthesia [41].
Physical therapy — Although most patients with ventilatory pump failure who require pulmonary interventions are wheelchair dependent, some who require up to 24 hour ventilatory support can walk. Indeed, some can only walk if using CNVS [42]. Musculotendinous releases and physical and occupational therapy are useful to maintain their orthopedic status and function. In addition, preventing back deformity can permit the use of the intermittent abdominal pressure ventilator and prevent the untoward effects of back deformity on cardiopulmonary and physical functioning [43].
There is no evidence that skeletal muscle exercise improves pulmonary function or prognosis in patients with neuromuscular disease [44]. Activities of daily living can be greatly facilitated by use of a wheelchair, adaptive equipment, and energy conservation. There are a multitude of orthoses including robotic manipulators and other assistive devices for helping the patient with dressing, grooming, personal hygiene, transfers, wheelchair mobility, and possibly ambulation. Environmental control systems can permit the severely disabled individual to have access to the telephone and all electrical appliances. Robot arms [44], including the JACO, specifically assist with feeding and other upper limb activities of daily living from motorized wheelchairs and are operated using motorized wheelchair controls so anyone who can operate a motorized wheelchair can operate the robot arm. Commercial robot arms are programmable, lightweight, and easy to mount on the wheelchair and manipulate.
For many patients, an efficient bowel and bladder management program greatly facilitates the activities of daily living. Constipation, associated with increased gastrointestinal transit time, is common. High fluid intake should be encouraged.
●The most useful single technique for facilitating a bowel movements is using a lift so that the patient's hips are flexed and the buttocks are in a dependent position over a commode. This can decrease post-suppository evacuation waiting time from hours to minutes.
●A condom catheter drainage system can permit patients to urinate without the need for personal assistance or interruption of the activities of daily living.
●Use of mattresses that slowly rotate patients from side to side during sleep can decrease arousals and eliminate the need for assisted turning.
SUMMARY AND RECOMMENDATIONS
●In patients with ventilatory pump failure, respiratory insufficiency is manifest by symptomatic alveolar hypoventilation, difficulty clearing airway secretions, and ventilation-perfusion mismatching and is initially treated by nocturnal noninvasive ventilatory support (NVS). (See 'Introduction' above.)
●When alveolar hypoventilation extends into the daytime hours, use of NVS extends into daytime hours and eventually becomes continuous (CNVS). Criteria for dependence on CNVS rather than tracheostomy ventilation is discussed. (See 'Indications' above and 'Patient selection' above.)
●The most practical daytime NVS interface is a mouthpiece for NVS. Mouthpiece NVS delivers positive pressure via a 15 mL angled mouthpiece that is kept adjacent to the mouth for easy access that can augment breaths by volumes of over 1 liter of which the patient takes as much as they want. (See 'Types' above.)
●In patients who have neck rotation or lip strength that is inadequate for grabbing a mouthpiece, nasal NVS or the intermittent abdominal pressure ventilator (IAPV) can be used during daytime hours. (See 'Types' above.)
●The ability to generate sufficient expiratory flow for effective coughing is the most important factor permitting the definitive use of NVS. When neuromuscular disease causes an ineffective cough, insufflation to increase lung recoil combined with exsufflation and, at times, abdominal thrusts can make cough flows more effective as can the use of mechanical insufflation-exsufflation.
●Home monitoring of oxygen saturation (SpO2) is needed to assure adequacy of cough and ventilation, especially during upper respiratory infections. (See 'Practical aspects' above.)
●Many patients with neuromuscular or chest wall disease who undergo tracheostomy for mechanical ventilation during a respiratory tract infection, are candidates for NVS and removal of the tracheostomy tube, if the criteria in the table (table 2) are fulfilled. (See 'Tracheostomy to noninvasive ventilation' above.)
●Since even with unmeasurable vital capacity patients do not need tracheostomy tubes, the only true indication for tracheostomy for patients with ventilatory pump failure is the decrease in MIE exsufflation flows to approximately 100 L/minute. This indicates inadequate upper airway patency for MIE to effectively expel airway secretions to prevent a decrease in baseline peripheral oxygen saturation below 95 percent. These patients generally have stridor and hyperactive deep tendon reflexes. (See 'Indications for tracheostomy' above.)
