Pathophysiology
II-15. Organ damage from chronic global respiratory failure (COPD)
慢性全呼吸不全（主にCOPD）による臓器障害
Common COPD Comorbidities
Chronic heart failure, atherosclerosis, cachexia (muscle loss), osteoporosis, immunodeficiency, T2DM.
Systemic Inflammation (CRP, TNF-α, Fibrinogen, ROS)
- One inflammatory mechanism amplifies another. Smoking → ↑ROS + ↑TNF-α (CRP-mediated) → CVD, T2DM, cachexia, osteoporosis, COPD.
- Heart failure link: smoking → coronary atherosclerosis → ↓myocardial contractility → ↓CO → pulmonary congestion (diastolic HF) → interstitial edema → ↓O₂ diffusion; congestion → airway narrowing (obstructive) + ↓compliance (restrictive).
Respiratory Failure & Heart Failure
- ↓pO₂ → mean pulmonary arterial pressure ↑ linearly = pulmonary hypoxic vasoconstriction (physiological).
- Distinguishing dyspnea source: failing RV can be replaced by LV work (continuous myocardial bundles); cardiac dyspnea relates to LV failure → pulmonary venous congestion, ↓tissue compliance, ↑airway resistance, low tidal volume. Clinically significant secondary pulmonary hypertension is rare in COPD.
Long-term COPD Outcome
- V/Q mismatch hypoxemia (type 1) → dyspnea → hyperventilation → ↓pCO₂ → respiratory muscle fatigue.
- Hyperventilation stops → ↓pO₂, pCO₂ normalizes → worse muscle fatigue (type 2) → hypoventilation.
- ↓Ventilation → severe ↓pO₂, ↓pH, ↑pCO₂ (type 3).
ECG: Right Heart Strain
- Repolarization abnormality from RV hypertrophy/dilation.
- ST depression + T-wave inversion: right precordial (V1–V3 ±V4), inferior (II, III, aVF — most in III).
- RVH features: right axis deviation, dominant R in V1, dominant S in V5/V6.
Mortality Causes (COPD)
- Men: coronary artery disease (36%), tumor (30%), cerebrovascular (10%), respiratory (9%).
- Women: tumor (30%), coronary (28%), cerebrovascular (15%), respiratory (8%).
Muscle Breakdown
- Inactivity (dyspnea) + inflammation/oxidative stress → ↓protein synthesis + ↑degradation → skeletal muscle wasting.
Treatment
- O₂ 24 hours/day, maintenance of underlying condition + flare prevention, treat comorbidities.
- Death causes: irreversible exertional syncope, infection, diabetes (steroid-treated), heart failure, medication side effects (prolonged steroids).
一問一答
▶What are the common comorbidities of COPD?
Chronic heart failure, atherosclerosis, cachexia (muscle loss), osteoporosis, immunodeficiency, and type 2 diabetes.
▶Which systemic inflammatory markers link COPD to its comorbidities?
CRP, TNF-α, fibrinogen, and ROS — smoking raises ROS and TNF-α, driving CVD, T2DM, cachexia, osteoporosis, and COPD.
▶What are the three stages of long-term COPD respiratory failure progression?
1) Type 1: V/Q mismatch hypoxemia → hyperventilation → ↓pCO₂ → muscle fatigue; 2) Type 2: hyperventilation stops → ↓pO₂, pCO₂ normalizes → worse fatigue → hypoventilation; 3) Type 3: severe ↓pO₂, ↓pH, ↑pCO₂.
▶What ECG changes indicate right heart strain in COPD?
Repolarization abnormality (ST depression + T-wave inversion) in right precordial (V1–V3) and inferior leads (II, III, aVF), plus RVH features: right axis deviation, dominant R in V1, dominant S in V5/V6.
▶What are the leading causes of mortality in men with COPD?
Coronary artery disease (36%), tumor (30%), cerebrovascular (10%), and respiratory (9%).
▶What are the leading causes of mortality in women with COPD?
Tumor (30%), coronary (28%), cerebrovascular (15%), and respiratory (8%).
▶What is the cornerstone of long-term COPD treatment?
Oxygen 24 hours/day, maintenance of the underlying condition with flare prevention, and treatment of comorbidities.
▶Why is clinically significant secondary pulmonary hypertension actually rare in COPD?
Although hypoxic vasoconstriction occurs, clinically significant secondary pulmonary hypertension is uncommon; cardiac dyspnea more often relates to LV failure with pulmonary venous congestion.
▶How does cardiac dyspnea arise in COPD patients?
LV failure → pulmonary venous congestion → ↓tissue compliance, ↑airway resistance, and low tidal volume.
▶How does muscle breakdown develop in chronic COPD?
Inactivity (from dyspnea) plus inflammation/oxidative stress → ↓protein synthesis + ↑degradation → skeletal muscle wasting.
▶What are the main causes of death in advanced COPD?
Irreversible exertional syncope, infection, diabetes (steroid-treated), heart failure, and medication side effects (prolonged steroids).
▶How does smoking link COPD to heart failure?
Smoking → coronary atherosclerosis → ↓myocardial contractility → ↓CO → pulmonary congestion (diastolic HF) → interstitial edema → ↓O₂ diffusion.
▶Why can a failing right ventricle be partly compensated by the left ventricle?
Continuous myocardial muscle bundles allow LV work to partly replace failing RV function.
▶What is pulmonary hypoxic vasoconstriction and its hemodynamic effect?
A physiological response where decreasing pO₂ raises mean pulmonary arterial pressure linearly.
▶Why does respiratory muscle fatigue paradoxically worsen blood gases in COPD?
When hyperventilation can no longer be sustained, ventilation drops → pO₂ falls further and pCO₂ rises (progression from type 1 to type 2/3 failure).
▶Why does ECG show ST depression and T-wave inversion in right precordial leads in COPD?
RV hypertrophy/dilation produces a repolarization abnormality seen in V1–V3 (±V4).
▶How does pulmonary congestion produce both obstructive and restrictive defects in COPD with heart failure?
Congestion narrows airways (obstructive) and reduces lung compliance (restrictive).
▶Which inferior ECG lead shows the most prominent changes in COPD right heart strain?
Lead III (among the inferior leads II, III, aVF).
▶How does the concept of "one inflammatory mechanism amplifying another" apply to COPD?
Smoking-induced systemic inflammation (ROS, TNF-α) feeds forward, linking COPD with cardiovascular disease, T2DM, cachexia, and osteoporosis.
▶Why is prolonged steroid therapy a double-edged sword in COPD?
It treats inflammation but its side effects (e.g., steroid-induced diabetes, infections) are themselves causes of death.