Chronic Obstructive Pulmonary Disease (COPD)

Last Updated 06/06/2023

Author:Kevin M. O’Neil, MD, FCCP

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About Chronic Obstructive Pulmonary Disease (COPD)

Key facts about COPD
  • COPD is a common disease that can be prevented.
  • COPD causes loss of lung function over time.
  • To diagnose COPD, your provider will give you breathing tests.
  • You are at risk for COPD if you smoke; breathe indoor air pollution, including second-hand smoke; or are exposed to chemicals, fumes, or dust at work.
  • COPD is one of the leading causes of death and disability worldwide.

COPD Life Stories

A diagnosis of Chronic Obstructive Pulmonary Disease (COPD) can leave you feeling confused and unsure about how your daily life will be affected. You might wonder what changes you will need to make. It’s normal to feel unsure about how to manage your disease. The most important step you can take is being honest and open with your care team. Janice and John share how they came to understand their disease and live a full life with COPD.

Janice takes charge of her disease by never giving up.

John shares his experience being diagnosed and living with COPD, as well as hope for the future.

Chronic swelling in your lungs damages your airways (the tubes that carry air to your lungs) by narrowing them and causing your lungs to fill will mucus. Also, swelling in the air sacs in your lungs, called alveoli, damages lung tissue. This process makes it hard to get oxygen into and remove carbon dioxide from your body.

As this disease—called chronic obstructive pulmonary disease, or COPD—gets worse, the swelling causes shortness of breath and can limit your ability to perform everyday tasks, like housework or climbing stairs. People with COPD also experience sudden worsening of symptoms, called flares, which are often triggered by infections. Severe flares can require emergency care.

COPD can also cause cough, chest tightness, wheezing, and increased mucus production. Severe COPD can lead to weight loss and fatigue. Depression, thin bones, lung cancer, heart disease, and muscle weakness are more common in people with COPD. COPD can also cause severe disability and even death

No one knows why some people get COPD and others do not. Many factors may lead to the lung tissue damage seen in COPD, including environmental exposure and genetics. Other factors are related to childhood illnesses and early lung development.

COPD costs the United States $50 billion a year in lost wages and medical bills and is the third most common cause of death. In the United States, 16 million people have COPD.

COPD myths busted infographic

Managing Your COPD: Myths Busted

Misinformation can leave you feeling unsure of how to manage your COPD. Get facts you can trust to help inform you about the disease.

Download the PDF »

Learn More About COPD: Infographic

Get information you need to know at a glance, making it easier to understand the diagnosis and disease management options.

Get the Infographic »

COPD infographic

Questions to ask your doctor about COPD infographic

Questions to Ask Your Doctor: Patient Checklist

Working with your doctor is the best way to manage your COPD. By bringing this checklist to your next doctor’s appointment, you have a tool with you to help guide your conversations and get the most out of your time.

Download the Checklist »

This educational campaign on the burden of disease is funded by GSK and developed in collaboration with CHEST.

Recently diagnosed? Get help making a plan

If you’ve recently been diagnosed with COPD, you may feel scared, confused, and overwhelmed. The first step you can take to help alleviate these feelings is to make a plan. That’s why we’ve created a shared decision-making tool to help you do that.

The tool assesses your lifestyle, guiding you through information that you should take into account when choosing a treatment option. It records all of your answers so that you can print it out and take it to your doctor appointment. From there, you and your care team can work together to create the best treatment plan possible.

Please read over the infographic before accessing the shared decision-making tool, as it provides an overview of the topics that you will be covering and how to appropriately answer questions.

View the infographic »

COPD Shared Decision-Making Toolkit

Supported in part by an educational grant from Viatris and Theravance Biopharma

COPD Infographic References

COPD Mythbuster References

  • Aaron SD. Exploring below the tip of the iceberg: the prognostic impact of acute exacerbations of chronic obstructive pulmonary disease in primary care. Am J Respir Crit Care Med 2018;198:415–416.
  • 2020 Global Initiative for Chronic Obstructive Lung Disease Report, https://goldcopd.org.
  • Stolz D, Hirsch HH, Schilter D, Louis R, Rakic J, Boeck L, et al. Intensified therapy with inhaled corticosteroids and long-acting β2-agonists at the onset of upper respiratory tract infection to prevent chronic obstructive pulmonary disease exacerbations: a multicenter, randomized, double-blind, placebo-controlled trial. Am J Respir Crit Care Med 2018;197:1136–1146.
  • Chapman KR, Hurst JR, Frent SM, Larbig M, Fogel R, Guerin T, et al. Long-term triple therapy de-escalation to indacaterol/glycopyrronium in patients with chronic obstructive pulmonary disease (SUNSET): a randomized, double-blind, triple-dummy clinical trial. Am J Respir Crit Care Med 2018;198:329–339.
  • Osadnik CR et al, Non-invasive ventilation for the management of acute hypercapnic respiratory failure due to exacerbation of chronic obstructive pulmonary disease. Cochrane Database Syst Rev. 2017 Jul 13;7:CD004104.
  • Nagata K, Kikuchi T, Horie T, Shiraki A, Kitajima T, KadowakiT, et al. Domiciliary high-flow nasal cannula oxygen therapy for patients with stable hypercapnic chronic obstructive pulmonary disease: a multicenter randomized crossover trial. Ann Am Thorac Soc 2018;15:432–439.

Symptoms of COPD

It’s easy to mistake COPD for other diseases, including asthma, chronic lung infections, and heart disease, especially in the early stages of COPD. Most people with COPD start having symptoms when they reach their 50s and 60s. A small number of people who have an inherited form of COPD called Alpha-1 can have symptoms at a much earlier age.

COPD typically develops slowly. Symptoms start out mild but get worse, especially if you continue to smoke or breathe in pollution or chemicals. The most common symptoms are:

  • Shortness of breath
  • Cough with mucus production
  • Wheezing
  • Chest tightness
  • Weight loss, poor appetite, weakness, and fatigue (with advanced disease)

What are the risk factors for COPD?

Smoking increases the risk of getting many diseases in addition to COPD, including lung cancer and heart disease. Not all smokers develop COPD. If you smoke, the risk of developing COPD increases about 20% to 25% depending on how much you smoke.

Other risk factors for developing COPD exist:

  • Second-hand smoke exposure, which is the best known and most important risk factor
  • Some dust and fumes in the workplace
  • Indoor air pollution from burning wood and coal as fuel for heat and cooking
  • Alpha-1 antitrypsin deficiency, an uncommon inherited condition that greatly increases the risk of developing COPD
  • Having asthma, particularly if you smoking, as well
  • Early lung infections and other conditions during childhood that limit normal lung development

Diagnosing COPD

Elderly gentleman doing spirometry test,insets compare normal alveoli and bronchiole with COPD bronchiole and alveoli.
Elderly gentleman doing spirometry test, insets compare normal alveoli and bronchiole with COPD bronchiole and alveoli.

Early diagnosis and management of COPD can help reduce its effect on your life.

How is COPD diagnosed?

To determine if you have COPD, your health care provider will ask you about your medical history and your symptoms. He or she will also give you a breathing test that shows how well you can breathe out. Your provider may recommend other tests, as well, including:

  • A chest X-ray
  • Measuring your oxygen level
  • A blood test to check for an inherited (genetic) form of COPD
  • Additional breathing tests
  • Exercise testing

Get tested for COPD if you have ongoing problems with shortness of breath, a cough that produces mucus, wheezing, or chest tightness. Getting tested is especially important if you are a smoker or have a family history of COPD at an early age (before age 50).

If you already know that you have COPD, contact your health care provider if your symptoms get worse.

Treating COPD

The most important step in treating COPD is to remove the cause of your lung inflammation. For most people, that’s cigarette smoke. There’s no good way to repair damaged lungs, but quitting smoking can slow the loss of lung function. It also helps prevent disease flares.

If you smoke, stop. If you don’t smoke, don’t start and try to avoid being around those who do smoke. If you need help quitting, ask your health care provider for resources to help you stop.

Treating COPD with medication

Medication can help relieve many of the symptoms of COPD. It can also treat disease flares. Many COPD medications are taken using an inhaler, which helps drive more medication into the lungs. Often, several medications are combined in one inhaler. Health care providers may prescribe any of the following types of medication to treat COPD:

  • Bronchodilators. Bronchodilators work by relaxing the muscles in the airways to make it easier to breathe out. There are 2 types of bronchodilators; which one a provider prescribes depends on how the drugs relax the muscles. The 2 type works differently, and they can be combined.
  • Inhaled steroids. Inhaled steroids are medications that reduce swelling in the lungs.
  • Phosphodiesterase-4 inhibiters. These medications help reduce swelling. They are often prescribed to patients who have more severe COPD.
  • Antibiotics. Antibiotics are sometimes used to treat severe symptoms of COPD.
  • Oxygen therapy. Oxygen can help patients who have low oxygen levels during exercise to exercise longer.

Use of inhaled medications for long-term COPD maintenance

LAMA (long-acting muscarinic antagonist) is one type of bronchodilator. The other is LABA (long-acting beta-agonist).

Nebulizer Therapy for Long-Term COPD Maintenance »

Inhaled Medications for Long-Term COPD Maintenance »

This is a non-promotional, non-CME disease state educational program brought to you by CHEST. Sponsored by Theravance BioPharma and Viatris.

Treating COPD with surgery

Two types of surgery are used to treat severe symptoms of COPD:

  • Lung volume reduction surgery. This surgery involves removing damaged lung tissue so that the remaining lung can work better. The procedure can help a small number of patients with COPD.
  • Lung transplant. Lung transplant surgery can help some patients with very severe COPD.

Other treatments for COPD

  • Vaccinations. Vaccinations can held decrease the risk for severe lung infections.
  • Pulmonary rehabilitation programs. These programs combine education about COPD with a supervised exercise program that can improve patients’ ability to exercise and reduce shortness of breath.

Self-care and COPD

Patients with COPD face many challenges. COPD is a long-term disease and can affect many aspects of your life. But you can take steps to reduce the impact of COPD on your life:

  • Stop smoking. And don’t allow others to smoke around you. Avoiding smoke helps slow the progression of COPD and reduce the risk of severe symptom flares.
  • Stay active. Twenty minutes of moderate exercise 3 times a week helps reduce the risk of heart disease, decreases shortness of breath, and improves your well-being. If you can’t do 20 minutes of exercise or if you can’t do your normal activities because of shortness of breath, ask your health care provider to send you to pulmonary rehabilitation.
  • Eat a healthy diet. A healthy body weight helps avoid shortness of breath.
  • Educate yourself. Know about your disease and the treatment options. Know when you need to contact your provider. Have a plan for dealing with severe symptoms.
  • Take your medications. Many of the medicines used to treat COPD are expensive, and not many generic substitutes are available. If you can’t afford your medicine, let your health care team know. There are programs that may help you cover the cost of your medication.
  • Have a plan. If your COPD is moderate to severe, talk to your family and health care team about your wishes for end-of-life care. Knowing what’s important to you can help your provider and your family care for you as the disease progresses.

COPD progresses at a different rate for each person. For many people, COPD can eventually limit activity and reduce quality of life. Other diseases, like heart disease, depression, anxiety, and osteoporosis, are common among patients who have COPD and can also affect quality of life.

COPD Infographic

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COPD Myths Busted

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This patient education guide, infographic, and other collateral pieces are generously supported by the Allergy and Asthma Network.

Get the facts about COPD: Myths BUSTED

Myth:

Only smokers get COPD.

Fact:

10% to 20% of people who get COPD have never smoked. Right now that number adds up to between 24,000 and 48,000 patients with COPD who never smoked.

Myth:

COPD is a rare disease.

Fact:

COPD is the third leading cause of death in the US, impacting roughly 24 million Americans.

Myth:

I haven’t got COPD. This is just a smoker’s cough.

Fact:

There is no such thing as a smoker’s cough. If you’re experiencing a recurrent and productive cough and/or sputum, you probably have an inflamed airway, which may be a sign of chronic bronchitis. If you have a persistent cough, see a qualified health-care provider.

Myth:

I’ve smoked for more than 20 years. Stopping now won’t make any difference.

Fact:

When you stop smoking you achieve two benefits to counter COPD. First, you dramatically reduce your risk for a heart attack (myocardial infarction). Secondly, you increase your life expectancy, literally adding years to your life. So it’s never too late to stop smiling to improve your health.

Myth:

COPD only happens to old people.

Fact:

COPD can occur at any age. While most people with COPD contract the disease in their 60s or later, it can occur as early as 40 and, in rare cases, even earlier.

Myth:

There is no treatment for COPD.

Fact:

COPD is a treatable condition and there are many options to help you manage the disease and feel better.

Myth:

Getting started with oxygen therapy is a death sentence.

Fact:

Many patients with COPD live more than 10 years while on oxygen therapy. With the latest, lightweight and portable oxygen concentrators, oxygen therapy no longer limits your mobility so you can continue activities outside of your home.

COPD Myths Busted

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Women with COPD

COPD is the fourth leading cause of death for women in the United States and, currently, there are an estimated 7 million women living with COPD. Unfortunately, the number of women with COPD is increasing. Women have different patterns when it comes to the symptoms and severity of this disease compared with men. In this section, we’ll look at how COPD affects women.

Differences in COPD for Women

A quick snapshot of COPD highlights the key differences for women regarding the disease:

  • 6.8% of all women have COPD compared with 5.5% for men.1
  • Women are two times more likely to be diagnosed with chronic bronchitis while men are more likely to be diagnosed with chronic emphysema.2
  • Women with early onset COPD (between the ages of 40 and 64) have more severe symptoms than men.3
  • Women have a higher rate of hospitalization for COPD than men. Of the 1.4 million hospitalizations due to COPD in the United States annually, 64% (898,000) were women vs 36% (551,000) for men.4
  • While the number of men dying from COPD is decreasing, the number of women dying of COPD increased four-fold in the United States over the past 3 decades.5
  • Between 1999 and 2019, death rates of COPD dropped significantly for men (from 57.0 per 100,000 in 1999 to 40.5 per 100,000 in 2019) but only slightly for women (from 35.3 per 100,000 in 1999 to 34.3 per 100,000 in 2019).6
  • Roughly, 15% of all people diagnosed with COPD are non-smokers and women make up 80% of this group.7
  • Women have a higher incidence of COPD from environmental pollutants and exposures than men.8

Reasons for increases in COPD for women

Why is the number of cases for women with COPD on the rise and why are women smokers 50% more likely to develop COPD than men smokers? Researchers speculate there are a number of reasons:

  • Experts believe cigarette smoking may be more damaging to a woman’s lungs. Women have smaller lungs and bronchial tubes, so the same amount of inhaled smoke creates higher exposure to harmful effects, causing more damage.
  • Smoking wasn’t culturally acceptable for US women until the late 1950s. Smoking increased among women in the 1960s and 1970s. Subsequent to the rise of smoking in women, the number of cases of women with COPD began increasing then, and, in 2000, more women than men died of COPD for the first time.
  • More women smoke menthol cigarettes, which are particularly harmful because menthol cigarette smokers tend to take deeper breaths and hold them longer.
  • Estrogen may make women’s lungs more susceptible to tobacco smoke exposure, increasing potential damage. However, no direct correlation between female hormones or hormone replacement therapy (HRT) and COPD has been documented.

Characteristics of women with COPD

COPD presents differently in women. Compared with men, women:

  • tend to be younger when diagnosed with COPD;
  • have lower pack-years if they smoke;
  • have lower body mass index (BMI);
  • have a lower socioeconomic status; and
  • are multiracial, American Indian, Alaska native, Black or White vs Hispanic or Asian.

The most common risk factors for COPD in women are:

  • Smoking – cigarette, e-cigarette, marijuana
  • Exposure to secondhand smoke
  • Air pollution
  • Occupational dust and/or fumes

Women’s COPD symptoms are also different. Compared with men, women experience:

  • More shortness of breath
  • Greater airflow limitations in the lungs
  • Less expectoration of mucus
  • More flare-ups
  • Worse symptoms related to quality of life

Additionally, women who smoke experience a more rapid decline in lung function than men.

Women with COPD often have other health problems, including:

  • Asthma
  • Osteoporosis: More than half the people with COPD also have osteoporosis. Women should talk to their doctors about the use of inhaled corticosteroids, a common treatment for COPD, which can contribute to osteoporosis. Bone density scans and vitamin D and calcium supplements may be needed to reduce the likelihood of osteoporosis.
  • Depression and anxiety
  • Inflammatory bowel syndrome
  • Non-small cell lung cancer
  • Heart disease: Cardiovascular disease is a more common health problem for men with COPD than women, but it does impact women, as well.

More women than men are living with COPD in the United States today. But, there is some good news: women have a higher 5-year survival rate (86.9%) than men (76.3%).

Sources

  1. Percentage of adults in the U.S. with chronic obstructive pulmonary disease as of 2017, by smoking status and gender. Statistica. 2021.
  2. Martinez, FJ, Curtis, JL, Sciurba, F, et. al., National Emphysema Treatment Trial Research Group, Sex differences in severe pulmonary emphysema. Am J Respir Crit Care Med. 2007; 176(3):243-252.
  3. Sørroim, I, Johannessen, A, Gulski, A, Per; et. al., Gender differences in COPD: Are women more susceptible to smoking effects than men? Thorax. 2010; 65(6).
  4. COPD Foundation website, 2021.
  5. Trends in COPD (Chronic Bronchitis and Emphysema): Morbidity and Mortality. American Lung Association. March 2013.
  6. COPD Death Rates in the U.S. 1999 – 2019.Centers for Disease Control and Prevention Data Statistics.
  7. Chrvala, Carole A. COPD: What’s gender got to do with it? MedPage Today online.
  8. COPD and women’s lung health. Brigham Women’s Hospital website.

Resources

Think you might be at risk for COPD? Take this short screener.

Online and phone support

There are many places to get support for COPD. Local and online groups can help you find answers to your questions and provide assistance. Your health care provider will likely know the support groups in your area. Online resources are listed below:

Call to learn more about COPD and talk to people who understand the effect COPD has on your life.

Support groups

Information about COPD

For health-care providers

  • WipeCOPD. WipeCOPD is an acronym for Web-based Interactive Professional Education in Chronic Obstructive Pulmonary Disease. This program was developed with the help of an educational grant entitled the “GlaxoSmithKline Distinguished Scholar Award in Respiratory Health” from the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.

Frequently asked questions about COPD

  • Do I have COPD?

    This sounds like a simple question, but many diseases can be confused with COPD, especially asthma. Some patients have features of both asthma and COPD, called asthma-COPD overlap syndrome. Patients with this syndrome should see a lung specialist because they tend to have more problems than patients with either asthma or COPD alone.

  • How severe is my COPD?

    Health care providers use breathing tests and the GOLD classification system to grade COPD severity. The scoring system can be helpful, but it’s not always accurate. The more important question to ask yourself and to discuss with your provider is, “How does COPD keep me from doing what I want to do?”

  • Am I up to date on my immunizations?

    Preventing infection is important for patients with COPD. Patients should be up to date on all immunizations but pay particular attention to influenza (flu) and pneumonia vaccinations. Current recommendations say that patients with COPD should receive yearly flu shots and both pneumococcal (pneumonia) vaccinations.

  • What are the side effects of my medications?

    This is an important question. Your health care provider should review with you how to take all new medications and their possible side effects. Ask if there are any interactions with your other medications and how to tell if the side effects are serious enough for you to stop the medication.

  • What should I do if my breathing gets worse?

    Ask your health care provider what you should do when your provider’s office isn’t open when you need help.

  • What should I do if I’m traveling? Do I need oxygen for an airplane flight?

    Traveling can create challenges. If you are traveling, make sure that you have enough medication for the trip in your carry-on bag (if you’re flying). If you use oxygen, you will need it when flying. Some people who don’t typically use oxygen will also need it on an airplane. Your health care provider can tell if you will need oxygen based on some simple office tests. You will also need to notify the airline. If you need oxygen at your destination, your oxygen supplier will need to arrange this in advance.

  • I can exercise by myself. Why do I need to go to pulmonary rehabilitation?

    Pulmonary rehabilitation is more than just exercise. These programs offer education that can help patients with COPD. Exercise in pulmonary rehabilitation is monitored by medical professionals, and you are less likely to stop exercising if you do it with a group.

  • Do I need a nebulizer?

    Nebulizers convert liquid medicine into a mist that can be inhaled. Most patients with COPD don’t need nebulizers, but these devices can help some patients who have difficulty using inhalers. There are several disadvantages to using nebulizers, too. For example:

    • It takes extra time to deliver medication through a nebulizer.
    • Nebulizers are less portable and require cleaning.
    • Not all medications can be given with a nebulizer.
    • Nebulizer medication doses are much larger than those in inhalers, so the risk of side effects is higher

    Talk to your provider about a nebulizer if you’re having problems using an inhaler.

  • Oral steroids help my breathing when I have a flare. Why can’t I take them all the time?

    Oral steroids can help with flares, but they have many side effects that get worse when you use them over time. Also, oral steroids have not been shown to help most patients with stable COPD, and they are not recommended for long-term use.

  • Should I have a lung transplant?

    COPD is the most common reason for a lung transplant. Lung transplants can improve survival and quality of life in some patients with end-stage COPD, but they can have complications, as well. After a lung transplant, you need to take medication to keep from rejecting the transplant. The supply of lungs for transplant is limited, and not everyone with COPD is healthy enough for the surgery. Transplants are typically done when a person has less than 2 years to live, but it can be difficult to predict how quickly COPD will get worse. If you think you may be interested in a lung transplant, ask your provider to send you to a transplant center for testing.

COPD for Clinicians

COPD is a debilitating respiratory condition that is mostly preventable and manageable. Low public awareness of the condition and its symptoms often leaves those newly diagnosed feeling unsure how to best manage their care. Establishing a relationship is crucial to building trust between you and your patient, who can often be hesitant to disclose symptoms. Providing your patients with the information they need to educate themselves can help prevent exacerbations, which cause irreversible lung damage and become increasingly uncomfortable if not managed correctly.

Managing COPD can be a team effort between patients and their clinicians. We have developed resources to assist both you and your patients in understanding the condition, raising awareness of treatment options and working together to develop a treatment plan.

Infographic: Inhaled Medications for Long-Term COPD Maintenance 

Get an overview of how to utilize nebulized LABA and LAMA for treating your patients with COPD. 

Download the Infographic »

Myths Busted: Nebulized LAMA for COPD 

Learn the truth behind common myths about nebulized therapy for long-term COPD management. 

Access the PDF »

Developed by the American College of Chest Physicians with support from Viatris and Theravance Biopharma.

COPD myths busted infographic

Managing COPD: Myths Busted

Common misconceptions that could impact the effectiveness of your patients’ COPD management plan.

Download the PDF»

COPD Healthcare Provider Resource

Quick overview of some disease management options.

View the Infographic »

COPD infographic

This educational campaign on the burden of disease is funded by GSK and developed in collaboration with CHEST.

COPD Healthcare Provider Resource  References

  • Melani AS. Long-acting muscarinic antagonists. Expert Rev Clin Pharmacol 2015; 8(4): 479-501 
  • Montuschi P. Pharmacological treatment of chronic obstructive pulmonary disease. Int J Chron Obstruct Pulmon Dis. 2006;1(4):409–423 
  • Murphy, A. How to help patients optimise their inhaler technique The Pharmaceutical Journal27 JUL 2016 
  • Hanania NA et al. Pulmonary Disease Aerosol Delivery Devices, 3rd Edition American Association for Respiratory Care, © 2017 Chronic Obstr Pulm Dis. 2018;5:111-123 

COPD Mythbuster References

  • Aaron SD. Exploring below the tip of the iceberg: the prognostic impact of acute exacerbations of chronic obstructive pulmonary disease in primary care. Am J Respir Crit Care Med 2018;198:415–416.
  • 2020 Global Initiative for Chronic Obstructive Lung Disease Report, https://goldcopd.org.
  • Stolz D, Hirsch HH, Schilter D, Louis R, Rakic J, Boeck L, et al. Intensified therapy with inhaled corticosteroids and long-acting β2-agonists at the onset of upper respiratory tract infection to prevent chronic obstructive pulmonary disease exacerbations: a multicenter, randomized, double-blind, placebo-controlled trial. Am J Respir Crit Care Med 2018;197:1136–1146.
  • Chapman KR, Hurst JR, Frent SM, Larbig M, Fogel R, Guerin T, et al. Long-term triple therapy de-escalation to indacaterol/glycopyrronium in patients with chronic obstructive pulmonary disease (SUNSET): a randomized, double-blind, triple-dummy clinical trial. Am J Respir Crit Care Med 2018;198:329–339.
  • Osadnik CR et al, Non-invasive ventilation for the management of acute hypercapnic respiratory failure due to exacerbation of chronic obstructive pulmonary disease. Cochrane Database Syst Rev. 2017 Jul 13;7:CD004104.
  • Nagata K, Kikuchi T, Horie T, Shiraki A, Kitajima T, KadowakiT, et al. Domiciliary high-flow nasal cannula oxygen therapy for patients with stable hypercapnic chronic obstructive pulmonary disease: a multicenter randomized crossover trial. Ann Am Thorac Soc 2018;15:432–439.