Which of the following regarding Residual volume is correct?

Correct Answer: D

Rationale: Residual volume (RV) stays constant lifelong (D) (Page 4, Ans: D). RV (~1.2 L) is air left after maximal expiration, not tidal (A, false tidal ends at FRC, ~2.5 L). COPD increases RV (B, false) via air trapping (hyperinflation, TLC > 6 L). Fibrosis reduces RV (C, false) by stiffening lungs (TLC < 6 L, Q1). D's stability set by lung structure, not age holds unless disease alters elasticity or recoil (normal 20-25% TLC). Unlike A's confusion with FRC or B's obstructive error, D reflects physiology's baseline, per spirometry standards.

Correct Answer: C

Rationale: Surfactant isn't deficient in term neonates . Type II cells mature by 36 weeks, producing surfactant (Q26). It causes hysteresis (A, true), easing inspiration vs. expiration. It doesn't raise resistance (B, false) it lowers work (Q9). Edema prevention (D) is indirect via stability, not primary. C's term-neonate claim unlike A's lung behavior contradicts physiology; deficiency is preterm (IRDS, Q5).

Correct Answer: D

Rationale: In pulmonary fibrosis, FEV1/FVC is ≥ normal. A 10% diameter increase cuts resistance (R ∝ 1/r^4), not raises it (A, false). COPD is common (B, false). Fibrosis restricts, not obstructs (C, false resistance normal). D's ratio (> 80%) holds as FEV1 and FVC drop evenly (Q1), unlike A's physics error, per restrictive physiology.

Correct Answer: D

Rationale: Chronic emphysema, an obstructive disease, causes CO₂ retention (hypercapnia), lowering pH (acidosis) as HCO₃⁻ rises to compensate respiratory acidosis. Chloride drops (low Cl⁻) via renal compensation, shifting anions, yielding low pH, low chloride, high CO₂ content' (D). High pH (A, E) suggests alkalosis, unfit for chronic CO₂ buildup. Eosinophilia (B) ties to allergy, not emphysema. Low CO₂ (C) fits hyperventilation, not obstruction. This blood gas shift e.g., pH 7.30, PaCO₂ 60 mmHg reflects ventilatory failure, critical in monitoring COPD progression and guiding oxygen or ventilatory support in advanced stages.

Correct Answer: D

Rationale: Pickwickian syndrome (obesity hypoventilation syndrome) features obesity (A), somnolence (B), and polycythemia high RBCs from chronic hypoxia (e.g., SpOâ‚‚ <90%). Excessive appetite (C) contributes to obesity but isn't a core association weight gain drives it. Anemia (D) contradicts hypoxia's erythropoietic stimulus; polycythemia is typical. This triad obesity restricts breathing, causing COâ‚‚ retention and daytime sleepiness defines the syndrome, distinct from sleep apnea alone. Anemia's absence (D) is the exception, key in recognizing this respiratory-metabolic overlap, guiding weight loss or ventilatory support in nursing care.