Lung Mechanics
This primary muscle of inspiration contracts and flattens to create negative intrapleural pressure
What is the diaphragm?
This spirometry measurement represents the volume exhaled during the first second of forced expiration
What is FEV1?
Gas exchange occurs across this thin structure separating alveolar air from pulmonary capillary blood
What is the alveolar-capillary membrane?
In emphysema, lung compliance is increased while this property is decreased
What is elastic recoil?
This is the single most important intervention proven to slow FEV1 decline in COPD patients
What is smoking cessation?
In normal breathing, this phase is passive and driven mainly by elastic recoil of lung tissue.
What is expiration?
A post-bronchodilator FEV1/FVC ratio below this value is diagnostic for COPD according to GOLD criteria
What is 0.70?
According to Fick’s law, emphysema impairs diffusion mainly because of loss of this property
What is alveolar surface area?
This protease released by neutrophils contributes directly to alveolar wall destruction in emphysema
What is neutrophil elastase?
This long-acting muscarinic antagonist provides 24-hour bronchodilation by blocking M3 receptors.
What is tiotropium?
These muscles, including the sternocleidomastoid and scalenes, are normally recruited only during respiratory distress or exercise.
What are accessory muscles of respiration?
A patient with emphysema has increased lung compliance. This means the lungs are easier to inflate but harder to do this during expiration because elastic recoil is lost
What is deflate (or empty)?
In the two-alveolus model, a low V/Q unit causes this major physiologic consequence.
What is hypoxemia?
This genetic deficiency causes panacinar emphysema with lower-lobe predominance
What is alpha-1 antitrypsin deficiency?
A COPD patient with pH 7.38, PaCO2 50 mmHg, and HCO3 29 mmol/L has this acid-base disorder.
What is compensated chronic respiratory acidosis?
In COPD, the diaphragm becomes flattened from hyperinflation, placing it at this mechanical disadvantage described by muscle physiology.
What is an impaired length-tension relationship?
This characteristic shape appears on the expiratory limb of the flow-volume loop in obstructive lung disease
What is a scooped-out or concave expiratory limb?
In COPD, hyperventilating healthy alveoli cannot fully compensate for poorly ventilated alveoli because this curve is flat at high PO2 values
What is the oxygen-hemoglobin dissociation curve?
Smoking worsens emphysema partly because it oxidizes and inactivates this antiprotease
What is alpha-1 antitrypsin?
Chronic hypoxemia stimulates the kidneys to release this hormone, leading to secondary polycythemia
What is erythropoietin (EPO)?
This mechanism explains why pursed lip breathing helps prevent premature airway collapse in emphysema patients
What is creation of positive expiratory back-pressure (a pneumatic splint)?
A patient’s FEV1 improves from 1.5 L to 1.62 L after albuterol. Because the increase is less than both 12% and 200 mL, this diagnosis is less likely.
What is asthma?
A 50-year-old patient has PaCO2 = 50 mmHg and PaO2 = 62 mmHg on room air. Using the alveolar gas equation, the approximate A-a gradient is this value
What is about 25 mmHg?
This pathophysiologic mechanism explains why small airways collapse during expiration in emphysema.
What is loss of radial traction from decreased elastic recoil?
A patient smoked 2 packs/day for 25 years before quitting. This cumulative smoking exposure is calculated in pack-years.
What is 50 pack-years?