An experiment is conducted in two persons (subjects T and V) with identical VTs (1000 milliliters), dead space volumes (200 milliliters), and ventilation frequencies (20 breaths per minute). Subject T doubles his VT and reduces his ventilation frequency by 50%. Subject V doubles his ventilation frequency and reduces his VT by 50%. What best describes the total ventilation (also called minute ventilation) and Va of subjects T and V?

Correct Answer: B

Rationale: Total ventilation (VE) = VT × RR; alveolar ventilation (VA) = (VT - VD) × RR. Initially, T and V have VT = 1000 ml, VD = 200 ml, RR = 20/min. VE = 1000 × 20 = 20 L/min; VA = (1000 - 200) × 20 = 800 × 20 = 16 L/min. For T: VT doubles to 2000 ml, RR halves to 10/min. VE = 2000 × 10 = 20 L/min (constant); VA = (2000 - 200) × 10 = 1800 × 10 = 18 L/min (increases). For V: VT halves to 500 ml, RR doubles to 40/min. VE = 500 × 40 = 20 L/min (constant); VA = (500 - 200) × 40 = 300 × 40 = 12 L/min (decreases). T's larger VT boosts VA despite lower RR, as more air exceeds VD. V's smaller VT reduces VA, as dead space consumes a larger fraction per breath despite higher RR. Option B (T: VE constant, VA increases; V: VE constant, VA decreases) matches, reflecting how VT impacts VA efficiency at fixed VE.

Correct Answer: A

Rationale: Total lung capacity (TLC) is the maximum air lungs hold after maximal inspiration, summing residual volume (RV, ~1-1.5 L), expiratory reserve volume (ERV, ~1-1.5 L), tidal volume (VT, ~0.5 L), and inspiratory reserve volume (IRV, ~2-3 L). In adults, TLC averages ~6 L (5-7 L, varying by sex, age, size), per standard physiology (e.g., Guyton). Two liters approximates FRC (~2.5-3 L), the resting volume. Four liters nears vital capacity (VC, ~4-5 L), excluding RV. Nine liters exceeds typical capacity, possibly hyperinflation. Six liters aligns with spirometry plus RV (e.g., helium dilution), reflecting full lung expansion in health, making it the best approximation for a normal human, widely validated across respiratory studies.

Correct Answer: C

Rationale: Surfactant reduces alveolar surface tension, causing hysteresis different inflation vs. deflation pressures in lung P-V curves due to tension dynamics, a true property. It lowers pulmonary resistance by easing expansion, not increasing it false but not queried. Surfactant deficiency is common in preterm neonates (<37 weeks), causing RDS, but in term neonates (≥37 weeks), production is typically mature, making commonly deficient in term-neonates' incorrect RDS is rare at term barring defects. Surfactant indirectly prevents pulmonary edema by stabilizing alveoli, reducing fluid transudation pressure, though not its primary role true enough. The term-neonate error misaligns with developmental physiology, where surfactant sufficiency is expected, distinguishing it as the incorrect statement amid surfactant's established functions.

Correct Answer: D

Rationale: Per Poiseuille's law (R ∝ 1/r^4), a 10% airway diameter increase reduces resistance by ~40%, not increases it false. COPD (e.g., emphysema) is common due to smoking, not least false. Pulmonary fibrosis, restrictive, reduces compliance, not airway resistance (obstructive) false. In fibrosis, FEV1/FVC is ≥80% (normal or higher) as both FEV1 and FVC drop proportionally true, unlike obstructive diseases (<70%). This ratio's preservation reflects restricted volume, not airflow, a key diagnostic feature, making it the true statement amid misconceptions about resistance and prevalence.

Correct Answer: C

Rationale: Coastal regions have milder climates due to water's high specific heat capacity (~4.18 J/g°C) and greater evaporation, moderating temperatures. Evaporation and cloud cover increase humidity, reflecting solar radiation and stabilizing heat summers cool, winters warm compared to inland. Water's albedo (~0.06) is low, absorbing more heat, not reflecting it false. Water's specific heat is higher, not lower, than land (~1 J/g°C), storing energy false. Latitude affects insolation broadly, not coast-specific false. Evaporation and clouds, tied to water's thermal inertia, buffer temperature swings, a key maritime effect (e.g., Mediterranean climates), making this the best explanation.