If a young female develops a circulating anticoagulant directed against factor VIII, which underlying diagnosis is most likely:

Correct Answer: A

Rationale: Lupus erythematosus (A) SLE produces lupus anticoagulant (e.g., anti-phospholipid antibodies), rarely against factor VIII, causing bleeding (acquired hemophilia mimic). Hepatitis (B), leukemia (C) don't target VIII. None' (D) dismisses. SLE's autoimmune link is key, guiding nursing for ANA and immunosuppression.

Correct Answer: D

Rationale: In a severe asthmatic attack, bronchoconstriction obstructs airways, reducing airflow, particularly during expiration, leading to wheezing. Forced expiratory volume in 1 second (FEV1) drops more than forced vital capacity (FVC), decreasing the FEV1/FVC ratio (normal >80%) due to obstruction, not increasing it. The ventilation/perfusion (V/Q) ratio in affected areas decreases, as ventilation is impaired more than perfusion, causing mismatching and hypoxemia (PaO2 60 mmHg, normal 75-100 mmHg). Arterial PCO2 (30 mmHg, normal 35-45 mmHg) is lower than normal, not higher, because hypoxemia stimulates hyperventilation via peripheral chemoreceptors, increasing respiratory rate to compensate for low oxygen. This overbreathing expels CO2 faster than it accumulates, despite uneven ventilation, contrasting with conditions like COPD where CO2 retention occurs. The lower PCO2 reflects this compensatory mechanism, aligning with asthma's acute physiology where gas exchange inefficiency drives respiratory effort, not CO2 trapping.

Correct Answer: D

Rationale: Vital capacity (VC) is the maximum volume of air a person can exhale after a maximal inhalation, measured via spirometry as the sum of inspiratory reserve volume (IRV, ~2-3 L), tidal volume (VT, ~0.5 L), and expiratory reserve volume (ERV, ~1-1.5 L), totaling ~4-5 L in adults. It excludes residual volume (RV), which remains after maximal exhalation. Sum of all lung volumes' describes total lung capacity (TLC, ~6 L), including RV, not VC. Tidal volume plus residual volume' (~2 L) is far less than VC, missing IRV and ERV. IRV plus ERV' omits VT, underestimating VC (~3-4 L). The correct definition IRV + VT + ERV captures the full expirable volume, reflecting the lung's functional capacity for deep breathing, a key metric in assessing respiratory health, distinguishing it from TLC or partial volume sums.

Correct Answer: C

Rationale: Lung compliance (C) is the change in lung volume per change in transpulmonary pressure (C = ΔV / ΔP), correctly defined. It's not maximal during quiet breathing (tidal volume ~500 ml); it's tested across a range, peaking at moderate volumes but decreasing at high volumes (e.g., near TLC) due to stiffness. In quiet breathing, compliance operates efficiently but isn't at its maximum. Crucially, compliance is inversely related to surface tension higher tension (e.g., no surfactant) stiffens alveoli, reducing compliance, as in RDS, not increasing it. This statement is incorrect, contradicting Laplace's law (P = 2T/r), where high tension raises collapse pressure, lowering compliance. Fibrosis decreases compliance by stiffening lungs with collagen, and emphysema increases it by destroying elastic fibers both correct. The surface tension error misrepresents surfactant's role, making it the exception among these statements, as compliance falls with rising tension.

Correct Answer: A

Rationale: Airway resistance (R) follows Poiseuille's law (R ∝ 1/r^4), but total resistance depends on cross-sectional area. Later generations (bronchioles) have smaller radii, yet their vast number increases total area (e.g., ~300 cm² vs. trachea's 3-4 cm²), reducing overall R most resistance is in larger airways (trachea, bronchi), where flow is turbulent, making this false. Normally, ~80% of R is in large airways, dropping in smaller ones due to laminar flow and area. Increased R (e.g., asthma) lowers FEV1/FVC (<70%), as FEV1 falls more, a true obstructive sign. Loss of elasticity (emphysema) and bronchoconstriction (asthma) raise R by collapsing or narrowing airways, also true. The false idea of increasing R in later generations misinterprets branching dynamics, where resistance peaks proximally, not distally, aligning with physiological airflow distribution.