Respiratory Disorders

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What are the common respiratory disorders most likely to affect sleep?

Respiratory disorders affect the breathing passages and lungs, muscles of breathing, breathing centers in the brain, and the space around the lungs (pleural space). Any respiratory illness that affects breathing can disrupt sleep. The most common respiratory conditions in the US are asthma and chronic obstructive pulmonary disease (COPD). People with respiratory failure (breathing difficulties due to muscle weakness, lung disease, or severe obesity) can also have increased problems with breathing at night.

Q:	Can asthma affect sleep quality?
A:	Over two-thirds of people with asthma experience narrowing of their airways during the night. This explains why the symptoms of many asthmatics worsen at night or early in the morning as evidenced by cough, wheeze, or breathlessness.

Q:	Why does airway narrowing (bronchoconstriction) occur at night?
A:	There is no single reason. In normal people, there are circadian changes in bronchoconstriction with a decrease in airway caliber at night. This response is exaggerated in asthmatics. Other factors that can cause airway narrowing include sleeping position, allergens in bedding, reflux, and impairment of mucous transport in the airways at night.

Q:	How does nocturnal wheeze affect sleep?
A:	Sleep is disrupted by the mechanics of coughing and the inability to get enough air into the lungs. This causes the oxygen level in the blood to fall. If the disruption is significant enough, it will lead to symptoms of daytime sleepiness. Although death from asthma is rare, most deaths from asthma occur at night or early morning.

What can I do about my nocturnal asthma symptoms?

Nocturnal bronchoconstriction is a definite sign of poor asthma control and you should seek medical advice about your asthma condition. Long-acting beta2-agonist inhalers are useful and the addition of a steroid inhaler may be necessary to reduce airway inflammation leading to bronchoconstriction. If you also suffer from sleep apnea, treatment of this condition will also improve asthma control. People with gastroesophageal reflux also benefit from acid suppression therapies. Keeping a regular peak flow meter chart will allow you to assess your progress and help your doctor work out a medication regimen for you.

Q:	I have been diagnosed with COPD. How could this affect my sleep?
A:	If your COPD (chronic obstructive pulmonary disease) is moderate to severe, you could experience periods of low blood oxygen levels during the night. Generally, your oxygen levels will fall at first during REM sleep and then as the disease progresses, during NREM as well. Low oxygen at night may make you feel unrefreshed in the morning and contribute to more restless sleep.

What causes oxygen levels to fall during the night in COPD?

You will probably already be experiencing lower oxygen levels during the day due to destruction of lung tissue responsible for transferring oxygen from the lungs into the blood. During the night, as muscles relax, oxygen levels drop further because you are breathing less during sleep. This is the most likely explanation for low oxygen levels at night in people with moderate to severe COPD. Once oxygen levels start to deteriorate, carbon dioxide levels build up and can lead to morning headaches and feelings of nausea as well as fatigue and sleepiness during the day. If someone has concurrent sleep apnea, then the problem can be worsened significantly.

Q:	How does low oxygen affect the body?
A:	Long-term low oxygen levels in the body can lead to heart rhythm problems as well as problems with increasing pressure on the right side of the heart, leading to heart failure with fluid buildup in the body. Sometimes, overproduction of hemoglobin to high levels occurs to deal with the low oxygen levels in the body, and this can also lead to problems.

Q:	Should I have a sleep study to find out what my oxygen levels are during the night?
A:	If your oxygen saturation as measured by the doctor is less than about 85 percent during the day while breathing room air at rest, your oxygen levels are probably dropping during the night, thereby leading to unrefreshing sleep. Overnight monitoring of your oxygen saturation using a probe on the finger (oximeter) is the first step toward being assessed.

What happens if my oxygen levels are low?

If your oxygen saturations drop significantly during the night as determined by your doctor, you may benefit from overnight oxygen delivered by nasal prongs to your nose. However, oxygen therapy is prescribed only to people who do not smoke. If you have carbon dioxide retention during the day as well as low oxygen, which your doctor can determine by doing a blood gas test, then you may benefit from other forms of treatment, with or without additional oxygen therapy. At that stage, you should be referred to a respiratory or sleep specialist who will assess you further.

Q:	Can I use sedatives for my insomnia if I have COPD?
A:	This depends on how severe your COPD is and how low your oxygen levels are. All sedatives must be used with caution: your doctor will be able to discuss the possible options with you.

What happens during sleep in respiratory failure?

In the early stages, gas exchange is relatively well preserved in NREM sleep; it is only during REM sleep when our body is “paralyzed” that breathing might not be adequate to compensate for breathing difficulties. Oxygen levels can dip sharply and carbon dioxide levels rise. As breathing problems grow more severe, the drop in oxygen and rise in carbon dioxide starts to occur throughout all stages of sleep and will then persist during the daytime. This leads to the symptoms of moderate to severe Type 2 respiratory failure.

Q:	What are the symptoms of Type 2 respiratory failure?
A:	Type 2 respiratory failure can give rise to a number of symptoms including shortness of breath; poor sleep quality with nightmares, insomnia, and arousals; early morning headaches; fatigue, sleepiness, and loss of energy; reduced daytime performance; loss of appetite and weight loss.

Q:	How is respiratory failure treated?
A:	Your doctor will advise you on this. You should be referred to a lung or sleep specialist who will examine you, do tests, and assess your breathing. Some people benefit from a treatment called noninvasive ventilation (see How does noninvasive ventilation work?).

Q:	How does noninvasive ventilation work?
A:	As you inhale, a machine delivers room air under pressure into your airway. This augments your own breathing and allows the muscles of ventilation to rest. When successful, central control of breathing improves. The pressure is delivered through a mask, similar to that used in continuous positive airway pressure . Oxygen may be added to increase overnight oxygen levels.

Q:	Can I use sedatives if I have respiratory failure?
A:	It depends on how severe your respiratory failure is and how low your oxygen levels are. All sedatives must be used with caution, so discuss this with your doctor.

Myth or truth?

Myth

“Disease does not affect either the quality or quantity of sleep”

Truth

This is not true. It is important to recognize that even in the absence of a primary sleep disorder, such as sleep apnea or narcolepsy, sleep and daytime functioning can be significantly affected by other medical or mood disorders as well as by pain, whether it be short-term or chronic.

What is chronic respiratory failure?

Chronic respiratory failure is of 2 types: in Type 1, not enough oxygen enters the bloodstream from the lungs but the carbon dioxide levels stay low; in Type 2, oxygen levels are low and carbon dioxide levels high. In someone with normal breathing, oxygen levels are high and carbon dioxide levels are low. The types of conditions in which people develop respiratory failure are outlined here:

Table
Area of body	Conditions associated with respiratory failure
Lungs and airways	Pulmonary fibrosis (scarring of the lung tissue) Pulmonary vascular disease (disease of the arteries and veins of the lungs) COPD (chronic obstructive pulmonary disease) Bronchiectasis (abnormally wide airways with excessive mucus production) Cystic fibrosis
Rib cage	Kyphoscoliosis (excessive curvature of the spine) Thoracoplasty (deforming surgery to the ribcage) Obesity hypoventilation (diminished drive to breathe due to massive obesity)
Central nervous system	Central alveolar hypoventilation (diminished or absent drive to breathe)
Muscles and nerves	Cervical cord lesions (injuries to the spinal cord in the neck) Motor neuron disease (progressive degeneration of the nerves in the brain and spinal cord that control muscles) Poliomyelitis Post-polio syndrome (muscle weakness and fatigue many years after recovering from polio) Muscular dystrophies and myopathies (muscle disorders resulting in muscle weakness)