All people reach a physiological peak at age 19. Muscle strength and endurance peak around this time or soon afterwards. After this we lose 1 to 3% of our strength per year. People, such as those post-poliomyelitis or spinal cord injury or with neuromuscular diseases such as Duchenne muscular dystrophy, spinal muscular atrophy, amyotrophic lateral sclerosis or others conditions, peak with less strength and have difficulties at an earlier age than the rest of us. The difficulties encountered from muscular weakness are in day-to-day functioning and in breathing and coughing due to weakness of inspiratory and expiratory (respiratory) muscles. Even in "normal" elderly people in nursing care facilities complications related to respiratory muscle weakness are a leading cause of suffering and death (Article 65 of Bibliography).
People with generalized weakness can have difficulty functioning that can be abetted with the use of assistive equipment and training (see Further Information). These conditions can also be a threat to survival when breathing, coughing, throat, and heart muscles are very weakened.
Fortunately, today, much can be done to avoid suffering and death from these causes. Typically, muscular conditions as opposed to neurological conditions do not affect the heart muscle. However, all people with myopathies like Duchenne muscular dystrophy should be evaluated for heart muscle weakness regularly. This is particularly true today because we have new medications and medical approaches to improving heart function (see Article 135 of Bibliography).
Typically people with weak breathing and coughing muscles are all right until a simple cold causes the production of airway secretions that the person is too weak to cough out. Bacteria multiple in the secretions and the person develops pneumonia and respiratory distress. He or she is taken to a local hospital where oxygen is given and when breathing is suppressed by the delivered oxygen, a tube is placed through the nose or mouth into the lungs to evacuate the secretions and provide breathing support. While receiving support through the invasive tube, breathing on one's own may be delayed or thought to be impossible. The patient is then told that a tracheostomy tube is needed. This is a tube that is passed through the neck and into the airway. Typically, the hospitalization during which a person undergoes tracheostomy following pneumonia is 72 days. In reality, virtually no one who can speak needs or should ever receive a tracheostomy tube and those who have them should consider having them removed, whether needing to use a ventilator or not. After tube removal the great majority of ventilator users can wean off of supported ventilation whereas this rarely happens when one has a tracheostomy tube (see Article 76 of the Bibliography).
Unfortunately, people are left to develop pneumonia after pneumonia, have hospitalization after hospitalization, and develop breathing difficulties and they are not offered the respiratory muscle aids that can prevent these problems. All that is typically done is that patients are given oxygen that only makes the problem worse and told that they must undergo tracheostomy to survive. Yet, all people with experience using tracheostomy tubes and noninvasive inspiratory and expiratory muscle aids greatly prefer the latter (Article 15 of the Bibliography).
Inspiratory and expiratory muscle aids are devices and techniques that involve the manual or mechanical application of forces to the body or intermittent pressure changes to the airway to assist inspiratory or expiratory muscle function. The most important inspiratory aid is to receive air under pressure when one inhales (intermittent positive pressure ventilation or IPPV). The most important expiratory aid is to have a negative pressure (vacuum) applied to the airway via the nose and mouth when one coughs along with a manual thrust to the belly to further increase cough flows.
No one should receive supplemental oxygen, bronchodilators, or other medications as an alternative to normalizing blood oxygen levels by normalizing lung ventilation. Using oxygen rather than assisted ventilation results in worsening of carbon dioxide retention and inevitably results in respiratory failure.
Lungs become stiff if not expanded regularly. The vital capacity is the deepest breath that one can blow into a device that measures it (spirometer). If the vital capacity is 500 ml but the predicted capacity is 5000 ml then without assistance one can only expand about 10% of one's lungs and the rest closes down and for children does not grow properly. Use of incentive spirometry or deep breathing is useless because they do not expand the lungs more than about 10%. Mobilization of the lungs to prevent chest wall contractures and lung restriction can only be achieved by providing regular deep volumes of air (insufflations) or overnight deep breaths (IPPV).
A person's maximum insufflation capacity (MIC) is determined by giving the person the largest volume of air that he or she can hold with the throat closed. This is usually done by teaching the person to stack volumes of air consecutively delivered from a manual resuscitator. The person holds the stacked air with the (throat) closed glottis until no more air can be held. Patients who learn glossopharyngeal (frog) breathing can often air stack to the MIC without mechanical assistance.
The primary objectives in using air stacking or in providing maximum insufflations as lung and chest wall range-of-motion are to: increase the MIC, to maximize cough flows, to maintain or improve lung elasticity, to prevent or eliminate atelectasis, and to master noninvasive ventilation (noninvasive IPPV). The ability to air stack means that one can use noninvasive ventilation and assisted coughing to prevent pneumonia, respiratory failure, or ever need to undergo tracheostomy. Air stacking can also increase voice volume, facilitate eating, and promote lung growth in children.
Since anyone who can air stack is also able to use noninvasive IPPV, if such a patient is intubated for respiratory failure, he or she can be extubated directly to continuous noninvasive IPPV whether or not able to breathe independently (see Further Information).
IPPV can be noninvasively delivered via mouthpieces, nasal, and oral-nasal interfaces for nocturnal ventilatory assistance (see Further Information). Many people with no ability to breathe on their own and no upper limb function keep simple Respironics (Murrysville, PA) 15 mm or 22 mm angled mouthpieces near their mouths and grab them between their teeth as needed to receive mouthpiece IPPV during daytime hours. Mouthpiece IPPV is the most important method of daytime ventilatory support. Some people keep the mouthpiece between their teeth all day. Most prefer to have the mouthpiece held near the mouth. A metal clamp attached to a wheelchair can be used for this purpose or the mouthpiece can be fixed onto motorized wheelchair controls, most often, sip and puff, chin, or tongue controls.
The ventilator is set for much greater than normal tidal volumes, often from 1000 to 2000 ml. The person grabs the mouthpiece with his mouth and supplements or substitutes for inadequate breath volumes. The person varies the volume of air taken from ventilator cycle to ventilator cycle and breath to breath to vary speech volume and cough flows as well as to air stack to fully expand the lungs.
To use mouthpiece IPPV effectively and conveniently, adequate neck rotation and oral motor function are necessary to grab the mouthpiece and receive IPPV without insufflation leakage. Since the low pressure alarms of volume-cycled ventilators can often not be turned off, to prevent their sounding during routine daytime IPPV when not every delivered volume is received by the patient, a flexed mouthpiece for IPPV or an in-line regenerative humidifier can be used. These create 2 or 3 cm H2O back pressure which is adequate to prevent the low pressure alarm from sounding.
The lipseal can provide an essentially closed system of noninvasive ventilatory support when using mouthpiece IPPV during sleep. Lipseal IPPV is delivered during sleep with little loss of air out of the mouth and with virtually no risk of the mouthpiece falling out of the mouth. Orthodontic bite plates and custom fabricated acrylic lipseals can also increase comfort and effectiveness. Typically high ventilator insufflation volumes of 1000 to 2000 ml compensate for air leakage out of the nose during sleep.
Because people prefer to use mouthpiece IPPV or the intermittent abdominal pressure ventilator for daytime use (see Further Information), nasal IPPV (or the noninvasive delivery of IPPV via a nasal interface ("CPAP mask") is most practical only for nocturnal use. Daytime nasal IPPV is indicated for those who cannot grab or retain a mouthpiece because of oral muscle weakness, inadequate jaw opening, or insufficient neck movement. Twenty-four hour nasal IPPV can, nevertheless, be a viable and desirable alternative to tracheostomy even for some people with severe lip and mouth muscle weakness.
Most people prefer to use IPPV via a nasal rather than oral interface during sleep. Whether using nocturnal nasal or lipseal IPPV in a regimen of 24 hour noninvasive IPPV, and despite the maintenance of normal daytime alveolar ventilation, about 3% of people with no ability to breathe on their own have episodes of excessive air loss during sleep. These often result in arousals with shortness of breath. The person may also complain of recurrence of morning headaches, fatigue, and perhaps nightmares and anxiety. The nasal ventilation user should usually be switched to lipseal IPPV and lipseal IPPV users can have their systems "closed" by having their nostrils clipped or plugged with cotton kept in by covering the nostrils by a Band-Aid during sleep. Another practical solution is to set the ventilator's low pressure alarm at a level that, by its sounding, stimulates the sleeper sufficiently to shorten periods of air leaking during sleep. Commonly, a low pressure alarm setting of 10 to 20 cm H2O pressure is used for this purpose and the user develops sleep reflexes to prevent prolonged air leakage.
There are now numerous commercially available nasal interfaces (CPAP masks). These include the Monark and gel masks from Respironics Inc., Murrysville, CO, the ResCare Inc. (San Diego) Sullivan mask, the SleepNet (Manchester, N.H.) Phantom™ and IQ™ Nasal Masks, and Mallincrodt interfaces (Pleasanton, CA). Each interface design applies pressure differently to the paranasal area. One cannot predict which model will be most effective and preferred by any particular user. Skin pressure and insufflation leakage into the eyes are common complaints with several of these generic models. Such difficulties resulted in the fabrication of interfaces that mold themselves to facial tissues and of other custom molded interface designs (see Further Information). People must be offered trials using various nasal interfaces and are encouraged to choose between them. Interface use is evaluated for comfort and seal around the nose. No one should be offered and expected to use only one nasal interface anymore. Alternating IPPV interfaces nightly alternates skin pressure sites, minimizes discomfort, and is to be encouraged.
People whose blood carbon dioxide levels increasing during the day causing their blood oxygen levels to decrease below 95% need to use noninvasive IPPV, usually mouthpiece IPPV, for periods of time during daytime hours. Failure to maintain normal lung ventilation during daytime hours will result in inadequate nocturnal benefit from the use of noninvasive IPPV. For patients not wishing to switch to lipseal IPPV for nocturnal aid despite excessive air leakage out of the mouth, a chinstrap or plugged lipseal can be used to decrease mouth leakage. In the presence of nasal congestion people either use decongestants to permit nasal IPPV or they switch to mouthpiece and lipseal IPPV, or on rare occasions, temporary use of a body ventilator like a portable iron lung. Most often the person continues nasal IPPV using decongestants.
Because of the need for air stacking, people over 5 years old whose MICs exceed their vital capacities need to use volume cycled portable ventilators rather than pressure cycled machines like BiPAP because the latter cannot provide optimally deep breaths or permit users to stack breaths.
In summary, noninvasive IPPV can be used for up to full-time ventilatory support for the great majority of people with no ability to breathe on their own provided that they have mouth muscle function sufficient for speaking.
Illness and death in people with generalized weakness is almost always due to respiratory difficulty that occurs because of a weak cough. Breathing (inspiratory), expiratory, and throat (bulbar) muscles are needed for effective coughing. The latter are predominantly the abdominal muscles. Clearing airway secretions can be a continual problem but it most often occurs during chest infections and following general anesthesia for surgery for any reason.
Peak cough flows (PCF) most exceed 160 liters per minute to be effective for coughing up airway debris. PCF are increased by manually assisted coughing. If the vital capacity is less than 1.5 liters, insufflating or air stacking to the MIC becomes crucial to optimize cough flows. Once the person is insufflated to the MIC, an abdominal thrust is timed to the cough to increase the flow. Techniques of manually assisted coughing involve different hand and arm placements for thrusts (see Further Information). A belly thrust with one hand while applying counterpressure to the chest with the other arm and hand further increases assisted PCF for 20% of people.
Manually assisted coughing requires a cooperative patient, good coordination between the patient and care giver, and adequate physical effort and often frequent application by the care giver. It is usually ineffective in the presence of significant back deformity.
Abdominal compressions should not be used for one and one-half hours following a meal, however, chest compressions can be used to augment PCF. When inadequate, the most effective alternative for generating optimal PCF and clearing airway secretions is the use of MI-E.
The inability to generate over 160 liters per minute of assisted PCF despite having a vital capacity or MIC greater than 1 liter usually indicates fixed upper airway obstruction or severe throat muscle weakness and airway collapse during coughing attempts. Vocal cord adhesions or paralysis may have resulted from a previous translaryngeal intubation or tracheostomy. Some lesions, especially the presence of obstructing granulation tissue, can be corrected surgically.
Mechanical Cough Assist devices (J. H. Emerson Co., Cambridge, MA) deliver deep insufflations followed immediately by deep exsufflations. The insufflation and exsufflation pressures and delivery times are independently adjustable. Except after a meal, an abdominal thrust is applied in conjunction with the exsufflation. MI-E can be provided via an oral-nasal interface, a simple mouthpiece, or via an invasive airway tube like a tracheostomy tube. When delivered via the latter, the cuff, when present, should be inflated.
The Cough-Assist™ can be manually or automatically cycled. Manual cycling facilitates care giver-user coordination of inspiration and expiration with insufflation and exsufflation, but it requires hands to deliver an abdominal thrust, to hold the mask on the patient, and to cycle the machine. One treatment consists of about five cycles of MI-E followed by a short period of normal breathing or ventilator use to avoid hyperventilation. Insufflation and exsufflation pressures are almost always from +35 to +60 cm H2O to -35 to -60 cm H2O. Most patients use 35 to 45 cm H2O pressures insufflations and exsufflations. In experimental models, +40 to -40 cm H2O pressures have been shown to provide maximum forced deflation volumes and flows (see Further Information). Multiple treatments are given in one sitting until no further secretions are expulsed and any secretion or mucus induced oxygen desaturations are reversed. Use can be required as frequently as every few minutes around the clock during chest colds. Although no medications are usually required for effective MI-E in people with weak muscles, liquefaction of sputum using heated aerosol treatments may facilitate exsufflation when secretions are inspissated.
Dr. Bach's Articles: ©2000-2004, John R. Bach, MD, used by permission.
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