Protocol for Management of SMA Children at the University Hospital Center for Ventilator Management Alternatives
By: Dr. John Bach
Professor of Physical Medicine and Rehabilitation, Vice Chairman of the Department of Physical Medicine and Rehabilitation; Professor of Neurosciences, Dept. of Neurosciences; and Co-Director of the Jerry Lewis MDA Clinic, UMDNJ-New Jersey Medical School, Newark, NJ.
The commitment of parents to the long-term care of any child with spinal muscular atrophy is a personal choice that carries with it enormous consequences. Any parent must have the right to make that choice. To do so, however, one should be thoroughly informed about all possible options. I will attempt to briefly explain these options.
If it is decided to "let nature take its course" and not intervene with ventilatory aids or translaryngeal intubation to effectively remove airway secretions, then, when the oxyhemoglobin saturation (SaO2) read off an oximeter is less than 95%, it is appropriate to administer oxygen to the child. It must be understood, that the oxygen is very much like putting a bounded on a cancer. The "cancer" here is the hypercapnia from lung underventilation and, especially, the airway secretions that are building up in the lung's airways and causing the SaO2 to decline. The oxygen may make the child more comfortable until he or she dies. Oxygen administration is of NO benefit to anyone whose SaO2 is normal and it is often unnecessarily used in this manner.
A second option is to prevent lung underventilation and effectively clear airway secretions when present, with the use of noninvasive respiratory aids. At University Hospital in Newark, we use a treatment management protocol that permits us to avoid resort to tracheostomy for people with any type of spinal muscular atrophy, at any age. Inspiratory muscle aids involves the use of nasal or mouth piece intermittent positive pressure ventilation (IPPV). Expiratory muscle aids involves the use of manually and mechanically assisted coughing to create the cough flows required to eliminate airway secretions. In the absence of supplemental oxygen, pulse oximetry is used as a guide to relieve both alveolar hypoventilation and airway mucus plugging. Therefore, oximetry is used as feedback to use respiratory aids sufficiently to maintain normal SaO2 to prevent or reverse hypoventilation and mucus plugging.
We advise the following to emergency room physicians evaluating children with SMA in respiratory distress and we practice the following at University Hospital:
1. institute continuous pulse oximetry
2. rule out pneumonia by chest x-ray
3. once pneumonia is ruled out, discontinue any supplemental oxygen the patient may be receiving unless you will intubate the patient
4. if the SaO2 is less than 94% or the patient is short of breath, assist breathing using a manual resuscitator or portable ventilator to deliver IPPV via a mouth piece or nasal interface.
The patient may require continuous use of noninvasive IPPV to maintain normal alveolar ventilation and to provide deep insufflations (air stacking) for subsequent assisted coughing. If the SaO2 does not return to greater than 94% with the use of noninvasive IPPV, institute aggressive manually and mechanically assisted coughing. If the baseline SaO2 still has not returned to >94%, this implies microscopic atelectasis and mandates the use of manually assisted coughing and mechanical In-exsufflation every 10 to 30 minutes until SaO2 remains normal. Once baseline SaO2 has returned to >94%, insufflation-exsufflation is only used to immediately reverse any intercurrent mucus plug associated oxyhemoglobin desaturations or upon patient request to assist in coughing.
If the patient has pneumonia and the SaO2 can not be normalized by noninvasive IPPV and assisted airway secretion management the patient can be temporarily intubated. We then do the following:
1. deep insufflations or "sighs" will be delivered at increasing volumes approaching the predicted inspiratory capacity, at a rate of at least several every 5 minutes
2. aggressive mechanical insufflation-exsufflation will be delivered via the tube every 10 to 30 minutes whenever the SaO2 dips below 94%, or upon patient request for assisted coughing
3. once the SaO2 is continuously greater than 94% without receiving supplemental oxygen, the patient will be switched to using a portable volume ventilator and extubated.
Ventilatory support will subsequently be provided by noninvasive IPPV as needed, and assisted coughing as required to continue to maintain normal SaO2. Whether or not patients can be entirely weaned from ventilator use, they are extubated and maintained at home using noninvasive aids as required. Tracheostomy is only used if lung pathology is not reversible. That is, if a lung is entirely collapsed and it is not possible to reexpand it in any way.
Many small children with SMA may need to be intubated for several days at a time 3 or 4 times before becoming old enough to cooperate fully with the use of noninvasive aids. It is important to realize that once intubated, the child must not be extubated until the SaO2 is greater than 94% without supplemental oxygen and he or she must not receive oxygen, but rather, use noninvasive IPPV (such as BiPAP) after extubation. A common mistake is to extubate children using oxygen while hypoventilation and airway secretions are still problems. Also, when using BiPAP, it is a common mistake to use it at grossly inadequate pressure spans. Whenever BiPAP is used, it should ALWAYS be used at inspiratory pressures of about 16 to 22 and expiratory pressures of 2 or 3. Smaller spans are never warranted. Children should not have to undergo tracheostomy because physicians are not familiar with how to manage them when they are intubated or after extubation.
Refer your physicians to the following book: Pulmonary Rehabilitation: The Obstructive and Paralytic Conditions. By John R. Bach, publisher Philadelphia: Hanley & Belfus, 1996.