Lung–kidney system ↗Demand raises ventilation and flow
Working muscle increases oxygen use and CO₂ production; ventilation, cardiac output, extraction, and heat-fluid regulation rise together.
LUNGS / 04
Six contexts.
Different failure points.
Exercise and altitude recruit adaptive responses. Asthma and COPD alter airflow through different mechanisms. Pneumonia disrupts alveolar units, while pulmonary embolism obstructs perfusion.
Reserve sets the response
Fitness, intensity, airway and lung mechanics, hemoglobin, heart function, environment, and muscle metabolism constrain performance.
Inspired oxygen pressure falls
Lower barometric pressure reduces inspired PO₂, stimulating ventilation and producing an early respiratory-alkalosis signal.
Kidneys enable acclimatization
Bicarbonate excretion supports sustained hyperventilation; plasma-volume and erythropoietic changes occur on different timescales.
Inflammation and hyperresponsiveness
Susceptible airways can develop swelling, mucus, sensitivity, and episodic smooth-muscle constriction after diverse triggers.
Reliever and controller targets differ
Bronchodilation acts on muscle tone, while inhaled corticosteroids change inflammatory signaling over time.
Persistent expiratory limitation
Airway inflammation, mucus, loss of elastic recoil, and alveolar destruction can combine in different proportions.
Exchange and cardiac load may change
Uneven ventilation, surface loss, hypoxemia, carbon-dioxide retention, and pulmonary vascular effects vary by phenotype and severity.
Inflammatory material fills alveoli
Infection can fill exchange units with fluid, cells, mucus, and debris, producing low ventilation despite continued perfusion.
Systemic demand can rise
Fever, immune activity, breathing work, dehydration, and comorbid reserve influence severity and recovery.
Perfusion is abruptly obstructed
A clot can block pulmonary arterial flow, increasing dead space and right-ventricular afterload.
Symptoms cannot identify the route
Sudden breathlessness, pleuritic chest pain, fainting, or coughing blood requires urgent evaluation rather than graph interpretation.