Respiratory Volumes, Capacities & Pulmonary Function

Question-and-answer flashcards covering lung volumes, capacities, dead space, spirometry, obstructive vs. restrictive patterns, FEV measurements, PEFR zones, ventilation calculations, and non-respiratory air movements.

What is the normal tidal volume (TV) and what does it represent?

≈500 mL; the volume of air inspired or expired during a normal, quiet breath.

Which lung volume is the extra air that can be inhaled after a normal inspiration, and what is its approximate value?

Inspiratory reserve volume (IRV); about 2100–3200 mL.

Define expiratory reserve volume (ERV) and give its typical range.

The amount of air that can be forcefully exhaled after a normal tidal expiration; ≈1000–1200 mL.

What is residual volume (RV) and why is it physiologically important?

≈1200 mL of air remaining in the lungs after a maximal expiration; it prevents lung collapse by keeping alveoli open.

Which capacity is the sum of tidal volume and inspiratory reserve volume?

Inspiratory capacity (IC).

Functional residual capacity (FRC) is composed of which two volumes?

Expiratory reserve volume (ERV) + residual volume (RV).

How is vital capacity (VC) calculated?

VC = IRV + TV + ERV (or the maximum amount of air exhaled after a maximal inspiration).

State the components of total lung capacity (TLC).

TLC = IRV + TV + ERV + RV (all lung volumes).

What is anatomical dead space and its approximate volume?

Air in conducting passages that does not participate in gas exchange; ~150 mL.

Differentiate anatomical dead space from alveolar dead space.

Anatomical: air in airways; Alveolar: non-functional or collapsed alveoli where gas exchange cannot occur.

Which instrument is used to measure respiratory volumes and capacities?

A spirometer.

How does spirometry distinguish obstructive from restrictive lung disease?

Obstructive shows increased airway resistance and reduced flow rates; restrictive shows reduced TLC and lung volumes due to stiffness or disease.

Give three examples of obstructive lung disorders.

COPD (chronic bronchitis/emphysema), asthma, bronchiectasis.

Give three examples of restrictive lung disorders.

Interstitial lung disease, scoliosis, neuromuscular causes (or severe obesity).

What does FVC stand for and what does it measure?

Forced Vital Capacity; the total gas forcibly exhaled after a maximal inspiration.

Define FEV1.

Forced Expiratory Volume in one second—the volume of air exhaled during the first second of an FVC maneuver.

What is the normal FEV1/FVC ratio in healthy lungs?

80 %.

How is the FEV1/FVC ratio altered in obstructive pulmonary disease?

It falls below 80 % because FEV1 falls more than FVC.

Why can the FEV1/FVC ratio be ≥80 % in restrictive disease?

Both FEV1 and FVC drop, but FVC decreases proportionally more, keeping or increasing the ratio.

What handheld device measures peak expiratory flow rate (PEFR)?

A peak flow meter.

List the PEFR zones and their interpretations.

Green: 80–100 % of personal best (continue routine care); Yellow: 50–80 % (possible exacerbation, adjust meds); Red: <50 % (take bronchodilator, consider steroids, seek help).

Provide the formula for minute ventilation and give its normal resting value.

Minute ventilation = respiratory rate × TV; ≈6 L min⁻¹ at rest (12 breaths×500 mL).

What formula defines alveolar ventilation rate (AVR)?

AVR = respiratory rate × (TV − dead space).

Why does rapid, shallow breathing reduce AVR even if minute ventilation is unchanged?

Because a larger proportion of each small breath occupies dead space, leaving less fresh air for alveoli.

Name at least four non-respiratory air movements that modify normal breathing rhythm.

Coughing, sneezing, laughing, crying, hiccups, yawning.