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Breathing

Breathing Changes: What to Watch For and When to Call

Breathing muscles weaken quietly. Watch for breathlessness lying flat, a headache on waking, daytime sleepiness, a cough gone soft, and neck muscles working at rest. A slow change over weeks goes to the next appointment. Confusion, blue lips, or breathlessness at rest is a call today. You cannot see oxygen or carbon dioxide levels at home, and a fingertip device will not tell you.

Early signs of breathing problems a caregiver actually sees

Weak breathing muscles rarely announce themselves as breathlessness. They show up as tiredness, poor sleep, and a cough that has lost its punch. These are the signs clinical teams ask about, drawn from the respiratory and sleep literature on ALS and other neuromuscular conditions.

• Breathless lying flat. Called orthopnea. The 2019 review in Nature and Science of Sleep notes people compensate by propping themselves more upright in bed.
• A headache on waking that fades over the first hour or two. Both the Muscle Nerve 2023 pulmonary care review and the sleep literature list morning headache as a symptom of overnight carbon dioxide buildup.
• Daytime sleepiness. In a 2011 ALS capnography study, daytime drowsiness was present in about 81 percent of the patients assessed.
• Broken, unrefreshing sleep. Waking repeatedly, waking with a start, or never feeling rested no matter the hours.
• A weak cough. It sounds soft or wet, and it stops clearing anything.
• A quieter voice, shorter sentences. Running out of air partway through. StatPearls calls this conversational dyspnea.
• Neck and shoulder muscles working. The European Respiratory Review notes accessory muscle use and shallow breathing are typically late signs, not early ones.

Any one of these on its own can have another explanation. A cluster of them, or one that is clearly new this month, is worth a phone call rather than a wait.

Why breathing weakness shows up at night first

Sleep removes most of the backup. During REM sleep the body actively switches off skeletal muscle activity, and that includes the external intercostal and accessory breathing muscles. As the 2019 sleep review puts it, that atonia spares the diaphragm, so the diaphragm is left holding almost the whole job alone.

If the diaphragm is already weak, the same review states that alveolar ventilation becomes too low to sufficiently exhale carbon dioxide. Lying flat makes it harder again. That is why the earliest evidence of a problem is a night thing: unsettled sleep, then a morning headache, then a day spent exhausted.

The practical consequence matters. Someone can look and sound completely normal sitting in a chair at 2pm and still be under-breathing every night. Daytime observation alone will miss it, which is exactly why clinics order overnight testing.

What you notice, what it may mean, what to do

A normal pulse oximeter reading is not reassurance

This is the single most important thing on this page. A fingertip pulse oximeter measures the saturation of oxygen carried in the red blood cells. It does not measure carbon dioxide. In weak breathing muscles, carbon dioxide is usually the thing going wrong first.

The 2011 PLoS One capnography study states it plainly: nocturnal pulse oximetry monitoring assesses the oxygenation status rather than the ventilation status of patients, and as such it may not be sufficiently sensitive to detect nocturnal hypoventilation. The 2023 Muscle Nerve review puts a number on it. Nocturnal pulse oximetry has only about 70 percent sensitivity for detecting nocturnal hypercapnia.

So the reading can sit in a comfortable range while carbon dioxide is dangerously high. A 2022 review in Frontiers in Medicine makes the mirror point: a drop in saturation is not specific either, because it cannot tell hypoventilation apart from other causes. The number is ambiguous in both directions.

Accuracy is a second problem. The American Lung Association points to an FDA alert listing poor circulation, dark skin pigmentation, thick skin, tobacco use, cool skin, and dark or artificial nails as factors that compromise the reading. Its own guidance is that pulse oximeter numbers should not be used in isolation to determine your state of health.

There is one more thing worth saying out loud. The fingertip oximeter in our own equipment catalog carries a disclaimer on its product listing that it is “for Sports and Aviation use only and is not a medical device.” That is the product itself telling you what it is for.

We are not linking one on this page. We would rather you spent the money on nothing at all than on a false sense of safety.

If the clinic has given you a device and told you what number to call about, follow the clinic. That is monitoring with a plan attached. Buying one yourself as a home safety net is not the same thing.

Slow change or acute change

Most families do not need a rule for the emergency. They need a rule for the middle, the change that is real but not dramatic. Use the clock, not the severity.

• Weeks to months. An extra pillow, a bit more tired, cough not quite as strong. Write it down with the date. Bring it to the next appointment.
• Days. New morning headaches, sleeping sitting up when they did not before, sleeping through the afternoon. Phone the clinic this week and say what changed and when.
• Hours. Breathless at rest, confused, blue-tinged, cannot clear secretions, cannot speak a sentence. Emergency services.

When you call, lead with the change and the date it started. “Two weeks ago he started needing three pillows, and this week he has woken with a headache four times.” That sentence is more useful to a respiratory nurse than any device reading you could give them.

What the breathing tests measure, and why they keep repeating them

Clinics repeat respiratory testing because no single test catches everything, and because the trend is worth more than any one result. The American Academy of Neurology’s practice parameter notes that forced vital capacity can be insensitive, citing a study where 13 of 20 patients with an FVC above 70 percent still had abnormal maximal inspiratory pressure.

• FVC sitting and lying down. The practice parameter notes supine FVC may be a better predictor of diaphragm weakness than the seated measure.
• Sniff nasal inspiratory pressure. A sniff through the nose. It gets around the mouthpiece seal problem when lips and face are weak.
• Maximal inspiratory and expiratory pressure. How hard they can pull in and push out against resistance.
• Peak cough flow. How fast air moves on a cough. Cochrane 2021 states adults need more than 160 L/minute for an effective cough, and more than 270 L/minute when well, because cough flows fall during a chest infection.
• Overnight oximetry. Recommended by the practice parameter to detect hypoventilation regardless of the FVC.
• Carbon dioxide measurement. Transcutaneous CO2 is described in the 2023 Muscle Nerve review as the most accurate noninvasive way to estimate arterial CO2. Blood gas is the gold standard.

Frequency depends on the person and how fast things are moving. A 2022 review of long-term home ventilation monitoring notes that reviews may be needed as often as every three months. Ask your clinic directly what interval they are working to, and ask them to tell you which number they are watching.

Making lying down easier

If someone is propping themselves up to sleep, a wedge is more stable than a stack of pillows that collapses at 3am. It is a comfort measure and a positioning aid. It is not a treatment for weak breathing muscles, and needing one is itself a thing to report. More positioning equipment is in our bed and pressure care catalog.

Common questions

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