Breathing and voice

At a glanceUnlike most forms of CMT, CMT2C often involves the vocal cords and the breathing muscles [6]. This page gathers what the medical sources say about protecting them: why oxygen alone is not safe for weak breathing muscles [153], why CPAP is not the right machine when they are weak [307], the early signs to mention to your doctor, and how to get ready for colds and surgery. Your own lung specialist will know what fits you.

How CMT2C can affect your voice and breathing

• Vocal fold weakness was found in 85% of TRPV4 registry participants who were examined by an ENT specialist, compared with 55% overall [3]. If you have never had your vocal folds examined, it is worth asking.
• Upper respiratory infections cause vocal fold swelling and can worsen airway obstruction [6].
• Difficulty breathing when lying flat and sleep apnea can occur [6].

CPAP and weak breathing muscles

Some adults with neuromuscular disease are prescribed CPAP, and some are told they must first “fail” CPAP before they can try anything else [312]. Breathe with MD, a charity for people with neuromuscular breathing weakness, explains why CPAP can be a problem [312]:

• It treats a problem most people with weak muscles do not have. CPAP works like an air splint that holds the airway open. People with neuromuscular disease generally do not have trouble keeping the airway open, and if they do, bilevel support can deal with that as well [312].
• It does not move air. Weak breathing muscles need help moving air in and out of the lungs, which is called ventilation. CPAP does not do that, so it cannot treat under-breathing (hypoventilation) during sleep [307].
• It is hard to breathe out against. A pressure high enough to fill the lungs can make breathing out uncomfortably hard for weak muscles [312].
• It does not fix a carbon dioxide build-up. When under-breathing has already raised carbon dioxide in the lungs and blood (hypercapnia), CPAP will not bring it down, and in some cases can make it worse [312].
• It adds work instead of resting the muscles. CPAP increases the effort of breathing, while the goal with weak breathing muscles is to reduce that effort and rest them during sleep [312].

What helps instead: ventilation. Bilevel support (often called BiPAP or BPAP) gives a higher pressure to breathe in and a much lower pressure, or none, to breathe out. A portable home ventilator can do the same. Set up properly for the person, bilevel ventilation treats under-breathing and the carbon dioxide build-up it causes [312]. In muscle disease, the gap between the two pressures is usually large, to help the muscles that breathe in and leave little or no resistance when breathing out [311]. A backup breathing rate is preferred, and volume-assured modes (VAPS) are another option [307]. The American College of Chest Physicians' 2023 guideline recommends non-invasive ventilation (breathing support through a mask or mouthpiece) for people with neuromuscular disease whose breathing is failing [308].

If you have been offered CPAP. Some general references, including the main clinical summary on TRPV4 disease, still list “BiPAP or CPAP” together [6]. If you have any sign of breathing-muscle weakness, ask a lung specialist who treats neuromuscular disease whether bilevel support or a ventilator would suit you better. CPAP is meant for a blocked airway, such as obstructive sleep apnea on its own, in people whose breathing is otherwise normal, and testing is needed to confirm this [288].

Quotes you can share with a clinician. Breathe with MD's CPAP Clarification and Advocacy Sheet collects quotes from medical articles, each with a link, for exactly this purpose [312]. Here are two that I checked against the original articles:

• “Continuous positive-airway pressure (CPAP) is not adequate to treat hypoventilation that occurs with NMD.” (Graustein, Carmona and Benditt, 2023) [307]
• Dr. John Bach told the Muscular Dystrophy Association that weak patients need “very high-span BiPAP or use of portable ventilators to fully rest muscles”, and “not CPAP, oxygen or low-span BiPAP” [311].

Spotting weak breathing early

Breathing-muscle weakness usually shows up first at night, during sleep [288]. Signs to mention to your doctor include shortness of breath or anxiety when lying down, restless sleep, waking often, waking tired after a full night, a headache on waking that goes away within minutes, repeated chest infections and sleepiness during the day [289]. They can creep up slowly, so they are easy to put down to something else.

Here are three things worth asking for at your breathing checks, from a specialist's review of breathing care in neuromuscular disease [288]:

• Test sitting and lying down. Vital capacity (how much air you can blow out after your deepest breath) normally falls by no more than 7.5% when you lie down. A bigger drop points to a weak diaphragm, often before anything shows when you are sitting up.
• Measure carbon dioxide at night, not only oxygen. Sleep studies are built for sleep apnea and can read weak breathing as apneas.
• Measure the strength of your cough. A peak flow meter can measure how hard you can cough. About 160 liters a minute is the minimum for an effective cough.

A handout to print or share. Morning headaches and breathing (PDF, 3 pages) puts these signs on one checklist, explains the first two tests above and gives you words to use with your doctor.

Getting ready for colds and surgery

• Colds are the usual trigger. In neuromuscular disease, breathing crises most often start with an ordinary cold that turns into pneumonia because the cough is too weak to clear mucus [288]. If your cough is weak, ask about air stacking (filling the lungs with several breaths from a hand-squeezed bag) and a cough assist machine [288]. It is easier to ask while you are well than in the middle of an infection.
• Before surgery or sedation, tell the anesthesiologist about your vocal folds and your breathing. Articles on anesthesia in neuromuscular disease stress a careful assessment before the operation, close monitoring during and after it, and breathing support ready afterward if needed [290].

These points come from research on neuromuscular disease in general, mostly from one specialist's review, and none has been tested in CMT2C. Your own lung specialist will know what fits you. Breathe with MD, a patient-run charity, explains each step in more detail [289].

A free course on breathing weakness. Stephanie Carmody, who lives with TRPV4 breathing weakness, highly recommends Breathe with MD's online course “Breathing Muscle Weakness 101”. She took it herself and, although she already knew a lot, learned new things. She finds the teaching clear. She suggests sharing it with family members who have breathing weakness too. The course is free, self-paced and mostly video, for adults living with a neuromuscular disease and their loved ones (not for clinicians). The 2026 course is open until 31 December, with a limited number of places [306].

What you can do next

• Book the yearly checks recommended for TRPV4 disease, listed under Build your team and your calendar, and use the care team guide to find the lung specialist and ENT you need.
• If you can, get your care at a CMT Center of Excellence.
• Note changes in your breathing, sleep, voice and swallowing in the printable symptom tracker, and bring it to each visit.
• See how often voice and breathing are affected in CMT2C on Symptoms and outlook.

Next: Why ABS-0871 matters