Oxygens percentage in the atmospheric air is that CO2 percentage and its solubility in solution (Example: Olood) is than CO2 solubility.

Correct Answer: B

Rationale: Atmospheric air contains approximately 21% oxygen (O2) and 0.04% carbon dioxide (CO2), meaning O2's percentage is much higher than CO2's, reflecting their natural abundances. Solubility in blood, governed by Henry's law, depends on the solubility coefficient of each gas. O2 has a solubility coefficient of about 0.024 ml O2/mmHg/L blood, while CO2's is much higher at 0.51 ml CO2/mmHg/L blood over 20 times greater. This means CO2 is far more soluble in solution than O2, despite its lower atmospheric presence. In blood, O2 relies heavily on hemoglobin binding (98% of transport), with only ~1-2% dissolved, whereas CO2 is transported dissolved (~7%), as bicarbonate (~70%), and bound to hemoglobin (~23%), leveraging its high solubility. Thus, O2's higher atmospheric percentage contrasts with its lower solubility compared to CO2, driving distinct transport mechanisms critical for respiration and acid-base balance.

Correct Answer: A

Rationale: Work of breathing (WOB) is the energy required to overcome elastic (compliance) and resistive (airway) forces during ventilation. Lung compliance (C = ΔV / ΔP) measures lung stretchability; low compliance (stiff lungs) increases pressure needed for a given volume, raising WOB. Thus, WOB is inversely related to compliance when C decreases, WOB increases, as in fibrosis. During exercise, WOB rises with higher ventilation rates and volumes, not remaining constant. Airway resistance (R) directly affects WOB; higher R (e.g., asthma) increases effort, contradicting not affected.' In pulmonary fibrosis, stiff lungs (low compliance) elevate WOB, not reduce it, unlike emphysema where high compliance might lower elastic work but raise resistive work. The inverse compliance relationship is fundamental, as WOB = ∫P dV, where pressure (P) rises as compliance falls, making this the correct statement reflecting respiratory mechanics.

Correct Answer: A

Rationale: Functional residual capacity (FRC) is the volume in the lungs after a normal expiration, equaling expiratory reserve volume (ERV) plus residual volume (RV). The spirogram shows maximal inhalation to total lung capacity (TLC) and exhalation to RV, with VC (vital capacity) as TLC - RV. RV is given as 1.0 L via helium dilution. FRC = ERV + RV, but without the figure, assume a typical female FRC (~2-3 L). If VC is ~4 L (normal for a young woman) and TLC ~5 L, then after maximal exhalation to RV (1 L), the difference from TLC to FRC includes ERV. Standard ERV is ~1-1.5 L; with RV = 1 L, FRC = 1 + 1 = 2.0 L fits option A, plausible for a smaller female frame. Higher values (2.5-3.5 L) align with larger individuals or males (~3 L). Without exact spirogram data, 2.0 L is reasonable, matching RV + minimal ERV, consistent with helium-derived RV and typical physiology.

Correct Answer: C

Rationale: A stab wound causing pneumothorax allows air into the pleural space, disrupting the negative intrapleural pressure (~-4 to -6 mmHg) that keeps lungs expanded. This equalizes pleural pressure to atmospheric (760 mmHg), eliminating the force opposing lung elastic recoil, which pulls the lung inward to collapse toward the hilum, reducing its volume. Meanwhile, the chest wall's outward recoil, no longer countered by lung tension, causes it to expand outward, increasing thoracic diameter. Thus, the lung collapses and the chest wall expands, a classic pneumothorax feature. Both expanding defies recoil mechanics, fixing at FRC ignores pressure loss, and collapse-collapse misrepresents chest wall behavior. This dynamic reflects the opposing elastic properties unleashed by pleural breach, critical for understanding respiratory compromise and interventions like chest tube placement.

Correct Answer: D

Rationale: Inspiration relies on Boyle's law: expanding the thorax lowers intrapulmonary pressure (e.g., 760 to 758 mmHg) below atmospheric, creating a pressure difference driving air in. Diaphragm and intercostal contraction generate this ~1-2 mmHg gradient for tidal breathing (~500 ml). Atmospheric pressure (760 mmHg) is static, not a force its difference with intrapulmonary pressure matters. Muscular spasm implies involuntary action, unlike controlled respiratory muscle contraction. Reduced surface tension (via surfactant) eases expansion but isn't the force pressure difference is. Muscle relaxation drives expiration, not inspiration. This gradient, directly linking mechanics to airflow, is the primary force, quantifiable and fundamental to ventilation, distinguishing it from secondary factors like surfactant or muscle state.