I am very sorry to hear of your myopathy with respiratory muscle weakness. I cannot tell from your description, what type of respiratory muscle weakness you have, but I suspect that your doctors have determined the cause, be it genetic (unlikely at your age), inflammatory, associated with a systemic disease (respiratory muscle weakness can occur in 5% to 10% of the patients with dermatomyositis and polymyositis and may be found in as many as 75% of individuals if respiratory muscle function is carefully evaluated) or metabolic diseases, for example, Glycogen Storage Disease, also referred to as Pompe Disease, that occurs in both childhood and adult forms. A muscle biopsy may be necessary to distinguish muscular dystrophies from inflammatory skeletal muscle disorders and other forms of dystrophy. Much of the following factual information was taken from Mason: Murray and Nadel's Textbook of Respiratory Medicine, 5th ed. Copyright 2010 Saunders
Dermatomyositis and polymyositis are systemic inflammatory diseases of unknown etiology that can cause profound skeletal muscle weakness. These inflammatory myopathies can involve the diaphragm, intercostal muscles, and accessory muscles but other peripheral muscle groups are usually more severely affected than the respiratory muscles. However, respiratory muscle weakness can occur in 5% to 10% of the patients with dermatomyositis and polymyositis and may be found in as many as 75% of individuals if respiratory muscle function is carefully evaluated. Interstitial lung disease may occur in up to 70% of patients with dermatomyositis or polymyositis. Individuals diagnosed with dermatomyositis or polymyositis should be evaluated for the presence of restrictive pulmonary disease, which may be due to respiratory muscle weakness as well as to underlying interstitial lung disease.
A number of enzyme deficiencies can lead to disordered glycogen metabolism, resulting in accumulation of glycogen in tissue including skeletal and cardiac muscle. The glycogen storage diseases that are most likely to affect the respiratory system are acid maltase deficiency (type II—Pompe disease) and debranching enzyme deficiency (type III—Forbes-Cori disease). These disorders usually present in childhood, but some, such as Pompe disease, have separate adult-onset forms.
You describe hypoventilation and atelectasis, commonly seen in conjunction with recurrent respiratory infection, including but not limited to pneumonia. The prompt treatment of infection is crucial and, in addition, cough-assist devices or assisted cough can be helpful in aiding removal of airway secretions. Nocturnal ventilatory assistance, may be required, especially in the presence of nocturnal hypoventilation, right heart failure, or the presence of an elevated Paco2 either at night or during the day. Noninvasive ventilation is a therapeutic intervention that typically can be delivered with a positive-pressure device using an interface such as a nasal mask, nasal-oral mask, or mouthpiece (discussed further later). Noninvasive ventilation may improve quality of life, physical activity, hemodynamics (including pulmonary artery pressure and, normalize arterial blood gases and prevent or attenuate pulmonary hypertension. Endurance and strength training targeting the inspiratory muscles may slow the progression of the disease in individuals with mild to moderate weakness, but the evidence for this is not strong
With respiratory muscle involvement, there may be restrictive ventilatory limitation and, in most severe cases, respiratory failure. Pulmonary function testing would document the degree of restrictive lung disease from respiratory muscle weakness. In fact the nodules you describe might be a reflection of interstitial lung disease as a second cause of restrictive lung disease.
The results from trials of enzyme replacement therapy with recombinant acid α-glucosidase are promising, showing potential improvements in motor status, function, and survival. Experts in the mechanisms and treatment (enzyme replacement and gene replacement therapy) of this class of diseases are 1) DD Koeberl and PS Kishani in the Division of Medical Genetics/Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA. dwight.***@**** and, 2) M Tarnolposky in the Department of Pediatrics and Medicine, McMaster University, Hamilton, Ont., Canada. ***@**** You may wish to mention these clinical researchers to your doctors to decide if consultation with them might be helpful.
You note that carbon dioxide retention/elevation (hypercapnia) has been documented during sleep and ask if that is a reflection of the respiratory muscle disease. The answer is yes, to the extent that chronic respiratory failure is present, secondary to respiratory muscle weakness and/or comprised muscle endurance.
You also note having had an oxygen saturation of 93% at this same time. The coexistence of these values can only occur with the use of supplemental oxygen. Preservation of a normal oxygen saturation during sleep is imperative for many reasons but especially for the prevention of pulmonary hypertension. If this can be achieved without incrementally increased levels of carbon dioxide, fine, but any further increase in the nocturnal levels of carbon dioxide should warrant consideration of the use of a positive pressure, ventilatory assistance device during sleep. You asked about having had a “serum CO2 and it was high at 34”. That probably represents, at least in part a compensatory response of your body to the respiratory acidosis induced by carbon dioxide retention.
The information you have provided suggests that your lung function is seriously compromised, resulting in chronic respiratory insufficiency. In some, but not all instances, this comprise of respiratory function can be progressive. For that reason it is imperative that the cause of your respiratory muscle disease has been determined with reasonable certainty and that your doctors are aware of and have considered the most up-to-date therapy available, wherever that availability and expertise might be found in North America.
My pulmo. also said I have alveolitis. Not sure what part,if any, this has in all this.
I saw my pulmo. who did a blood gas. My PCO2 was elevated at 47 and my PAO2 was 70. He said it needed to be monitored but no intervention was done at this point. This was done in the daytime. He did say use of bipap could correct this but I am not scheduled to see him until Dec. He is repeating my CTA scan at that time.