Chronic respiratory disease

Breathing needs airflow and gas exchange

Air travels through airways into alveoli, where oxygen crosses a thin barrier into blood and carbon dioxide moves in the opposite direction. Ventilation, gas exchange, and perfusion cooperate but are different processes. Narrow airways increase resistance. Damaged alveolar walls can alter exchange area and elasticity. Mismatching airflow with blood flow also reduces efficiency. Breathlessness describes an experience rather than locating the fault in one of these processes.

Chronic respiratory disease can increase the work of breathing during activity. Avoiding walking or stairs may then reduce fitness, making the same task harder. This interaction explains why disease and deconditioning both influence function. It does not mean every breathless person should exercise without assessment: new or rapidly worsening symptoms require consideration of cause and urgency. Record the baseline and acute changes separately so that new problems are not automatically attributed to a pre-existing lung diagnosis.

NHLBI: What Is COPD?

Variability and inflammation in asthma

Asthma involves chronic airway inflammation and variable airflow limitation. Symptoms may change with time, exposure, and treatment. Smooth-muscle contraction, swelling, and secretions can all affect airflow. Wheeze, cough, chest tightness, and breathlessness provide clues, but none independently establishes the diagnosis. A normal result on one day cannot automatically exclude a condition characterized by variability. History and suitable objective measurements must be considered together.

Relief of symptoms does not necessarily mean airway inflammation has disappeared, so long-term control and immediate symptom relief may serve different purposes. Medicines and devices should follow the individual prescription and current clinical guidance rather than be borrowed from a friend. A written action plan should clarify usual treatment, changes requiring team contact, and signs requiring emergency help. Asking the patient to explain and demonstrate inhaler use can reveal a gap between taking a medicine and delivering it effectively to the airways.

NHLBI: What Is Asthma?

NHLBI: Living With Asthma

Persistent airflow limitation and COPD exposures

Chronic obstructive pulmonary disease, or COPD, involves persistent airflow limitation associated with airway changes, excess mucus, and emphysema in varying proportions. Emphysema damages alveolar structure and elastic recoil, making expiration more difficult. Patients do not all have the same mixture of abnormalities, and COPD is not simply a synonym for frequent coughing. Diagnosis brings together symptoms, exposure history, and lung-function testing, especially properly performed spirometry.

Smoking is important but not the only contributor. Occupational dusts and fumes, household fuel pollution, limited early lung development, and some inherited factors can also matter. People who never smoked may develop COPD, and stopping smoking or reducing harmful exposures remains useful after diagnosis. Asthma and COPD share symptoms and can coexist. Treating the terms as interchangeable can distort understanding of the disease course, inhaled treatment, and exacerbation risk. Mechanism and objective evidence are more informative than a label based on one symptom.

NHLBI: What Is COPD?

WHO: Chronic obstructive pulmonary disease

Know what measurements capture and miss

Spirometry measures volumes and flow during breathing maneuvers and helps identify airflow limitation. A pulse oximeter estimates oxygen saturation but does not fully assess ventilation or directly determine whether carbon dioxide is accumulating. Imaging answers selected structural questions. Because the tools measure different things, a reassuring number should not override severe breathlessness or altered consciousness. Technique, device performance, peripheral circulation, and other factors can affect measurements.

Suppose someone has an acceptable saturation while walking slowly but can no longer manage their usual shopping. The reading does not establish preserved function. Activity tolerance, symptoms, examination, and the course require attention. Conversely, an unexpected reading may merit checking measurement conditions, but repeated verification must not delay help for an obviously unwell person. A record of baseline status, onset of change, activity limitations, and treatment is more useful at a visit than a screenshot of one isolated number.

FDA: Pulse Oximeters

What FEV1 and FVC tell us

During spirometry, the person inhales fully, then breathes out as forcefully and completely as possible. Forced vital capacity (FVC) is the total volume exhaled during that maneuver. Forced expiratory volume in one second (FEV1) is the volume exhaled in its first second. FEV1/FVC expresses the first-second volume as a proportion of the total; it does not mean “how much lung function remains.” The volumes and ratio require appropriate reference values and clinical context. (ATS/ERS: Standardization of Spirometry, 2019)

Check test quality before interpreting an abnormal number. A weak start, coughing, leakage, or stopping early can change the result. Early termination may reduce FVC and raise FEV1/FVC, potentially concealing airflow limitation. Operators therefore inspect the curves and compare repeated acceptable efforts. One low measurement cannot independently diagnose asthma or COPD, and an apparently normal ratio cannot make an inadequately performed maneuver reliable. (NIOSH: Spirometry Quality Assurance)

Combine treatment with support for function

Inhaled medicines may open airways or control inflammation, with selection depending on the disease and clinical situation. Devices can require different inhalation patterns, so a change of device should include demonstration and feedback. For appropriate patients, pulmonary rehabilitation combines training, education, and self-management support to improve functioning and quality of life. It does not promise to regrow damaged alveoli; it helps people use their available capacity more effectively.

Vaccination, infection prevention, reduced smoke exposure, nutritional support, and suitable activity may all contribute. Oxygen should follow assessment and prescription. Not every episode of breathlessness requires oxygen, and increasing the flow independently is not a substitute for evaluating deterioration. Home oxygen also requires fire precautions. Plans should address affordability, device operation, caregiver assistance, and transport, so that the recommended treatment becomes something the person can actually carry out.

WHO: Chronic obstructive pulmonary disease

NHLBI: COPD Treatment

Reasoning from baseline to acute change

Zhao is usually breathless on stairs. Today he is breathless while sitting, cannot speak in full sentences, and is becoming drowsy. His family attributes this to the usual fluctuation of longstanding lung disease. The relevant comparison is with his own baseline, not simply whether he has ever been breathless before. Marked breathlessness at rest, limited speech, and altered awareness are danger signs. Call emergency services and follow dispatcher guidance rather than waiting for an online explanation or repeatedly checking saturation.

Milder early changes without immediate danger should still trigger the agreed action plan and timely team contact. Changes in cough, sputum, fever, activity, and medicine use help assess an exacerbation, infection, or another cause. The same antibiotic or steroid is not automatically appropriate each time. Chronic describes duration, not constant safety. Good continuing care includes recognition, action, and review after deterioration.

Source: NHS: Shortness of breath

Bilingual terms

通气 · Ventilation

Movement of air into and out of the lungs.

灌注 · Perfusion

Blood flow through tissue capillaries.

肺量测定 · Spirometry

Testing of respiratory volumes and airflow.

急性加重 · Exacerbation

Worsening beyond the usual symptom state.

肺康复 · Pulmonary rehabilitation

Training, education, and support designed to improve functioning.

Sources and further reading

• NHLBI: What Is COPD?
• NHLBI: What Is Asthma?
• WHO: Chronic obstructive pulmonary disease
• NHLBI: COPD Treatment
• NHLBI: Living With Asthma
• FDA: Pulse Oximeters
• NHS: Shortness of breath
• ATS/ERS: Standardization of Spirometry, 2019 Update
• NIOSH: Spirometry Quality Assurance—Common Errors and Their Impact on Test Results

Original course source-check record: 9 September 2026. Full Chinese and English sentence-by-sentence language review: 14 September 2026. AI editing and language review are not human clinical review. Linked institutions have not participated in or endorsed this course.