Juvenile rheumatoid arthritis may include:

Correct Answer: D

Rationale: Juvenile rheumatoid arthritis (JRA) all true : uveitis (A eye inflammation), erythema multiforme (B rash, less common), pericarditis/valvular (C cardiac), lymphadenopathy/hepatosplenomegaly (D systemic JIA). Multisystem involvement is key, guiding nursing for eye exams, steroids, and systemic monitoring.

Correct Answer: D

Rationale: Fick's law of diffusion states that the rate of gas diffusion across a membrane (e.g., alveolar-capillary) is proportional to the surface area (A), diffusion coefficient (D), and partial pressure gradient (ΔP), and inversely proportional to diffusion distance (d): Rate = (A × D × ΔP) / d. When comparing different gases (e.g., O2 vs. CO2), the diffusion coefficient (D) varies most significantly, as it depends on gas solubility and molecular weight (D ∝ solubility / √MW). CO2's solubility is ~20 times higher than O2's (0.51 vs. 0.024 ml/mmHg/L), though O2's molecular weight is slightly lower (32 vs. 44), making CO2 diffuse ~20 times faster despite similar gradients. Partial pressure gradient drives diffusion but is gas-specific and often comparable (e.g., O2: 100-40 mmHg, CO2: 46-40 mmHg). Temperature and distance affect all gases similarly in the lung. Thus, the diffusion coefficient has the most pronounced effect across different gases, explaining why CO2 equilibrates faster than O2 across the respiratory membrane.

Correct Answer: B

Rationale: Mixed expired PCO2 (PECO2) reflects CO2 in exhaled air, diluted by dead space ventilation. Given dead space (VD) is one-third of tidal volume (VT), VD/VT = 1/3. The Bohr equation relates physiological dead space to CO2: VD/VT = (PaCO2 - PECO2) / PaCO2, where PaCO2 (arterial PCO2) is 45 mmHg. Substituting: 1/3 = (45 - PECO2) / 45. Solving: 45 / 3 = 45 - PECO2, so 15 = 45 - PECO2, and PECO2 = 45 - 15 = 30 mmHg. This assumes physiological dead space equals anatomic here, as no alveolar dead space is specified. Intuitively, if one-third of each breath doesn't participate in gas exchange (PCO2 ~0 mmHg in inspired air), the expired CO2 is diluted from arterial levels (45 mmHg) to two-thirds strength (30 mmHg), matching the calculation. Options like 45 mmHg imply no dead space effect, while 20 mmHg overestimates dilution. Thus, 30 mmHg aligns with the given ratio and respiratory physiology principles.

Correct Answer: D

Rationale: Pulmonary fibrosis, a restrictive disease, stiffens lungs with interstitial scarring. The FEV1/FVC ratio is normal or high (≥80%) because both FEV1 and FVC decrease proportionally, unlike obstructive diseases. Increased pulmonary vascular resistance occurs as fibrosis compresses capillaries, raising resistance. Peak expiratory flow (PEF), when corrected for reduced lung volume, can remain normal or above, as airflow isn't obstructed, just limited by volume. However, residual volume (RV) decreases in pulmonary fibrosis (e.g., from 1.5 L to <1 L) due to stiff lungs limiting all volumes, contrasting with obstructive diseases (e.g., COPD) where RV increases from air trapping. Increased RV doesn't fit fibrosis's restrictive pattern, where reduced elasticity shrinks residual air, not expands it, making this the inconsistent value among the set, reflecting the disease's impact on lung mechanics.

Correct Answer: D

Rationale: In a healthy upright individual, regional ventilation varies due to gravity and pleural pressure gradients. At rest, intrapleural pressure (IPP) is more negative at the apex (~-10 cm H2O) than the base (~-2.5 cm H2O) due to lung weight, making apices less compliant (stiffer) and bases more compliant (easier to expand). During quiet breathing (VT = 400 ml, RR = 12/min), the diaphragm's downward pull preferentially ventilates the lower zones, where compliance is higher and initial volume lower, allowing greater volume change (ΔV). Studies (e.g., West) show lower lobes receive ~4 times more ventilation per unit volume than apices. Thus, ventilation is greatest in the lower zones, followed by middle, then upper (Lower > Middle > Upper). Equal ventilation ignores gravity's effect, and Upper > Middle > Lower reverses the gradient. For this boy, VA = (400 - ~120 ml VD) × 12 = ~3.36 L/min, distributed predominantly to the base, making this the best description.