Why does angina occur in a person with coronary artery disease during exercise?

A. Respiratory acidosis:Respiratory acidosis occurs when hypoventilation causes CO2 retention, leading to a decreased pH (acidemia) and elevated PaCO2. In this scenario, the pH is elevated, and PaCO2 is low, which does not align with respiratory acidosis.

B. Metabolic alkalosis:Metabolic alkalosis involves an elevated pH and increased HCO3-. In this case, HCO3- is within normal limits (24 mEq/L), so the primary disturbance is not metabolic.

C. Respiratory alkalosis:Respiratory alkalosis results from hyperventilation, causing excessive CO2 elimination. This decreases PaCO2 (30 mmHg), elevates pH (7.50), and shows normal HCO3-, indicating a primary respiratory origin with no metabolic compensation.

D. Metabolic acidosis:Metabolic acidosis presents with a decreased pH and low HCO3-, often with a compensatory decrease in PaCO2. The elevated pH and normal HCO3- in this case do not support metabolic acidosis.

• Hypotension: Decreased circulating volume reduces venous return and cardiac output, leading to low blood pressure. Hypotension is a primary sign of hypovolemia and can compromise perfusion to vital organs. It reflects inadequate intravascular volume in fluid deficit states.

• Bounding pulses: Excess intravascular volume increases stroke volume and arterial pressure, producing strong, forceful pulses. The heart ejects a larger volume of blood with each beat, which is palpable as a bounding pulse. This is a classic sign of hypervolemia and is commonly seen in fluid overload states.

• Poor skin turgor (elasticity): Loss of interstitial and intravascular fluid causes the skin to become less elastic and slow to recoil when pinched. Poor skin turgor is a reliable indicator of dehydration and extracellular fluid deficit. It reflects overall hypovolemia and reduced tissue hydration.

• Hypernatremia: Fluid deficit increases the concentration of sodium in the blood due to water loss exceeding sodium loss. Hypernatremia is commonly associated with dehydration and reflects an imbalance between water and solute in the body. It signals a fluid deficit rather than overload.

• Crackles in the lungs: Pulmonary interstitial edema occurs when fluid accumulates in the alveoli due to volume overload. This results in crackles heard on auscultation, especially in the bases of the lungs. Pulmonary congestion is a hallmark of fluid excess, often associated with heart failure or renal impairment.

• Ascites: Excess fluid may accumulate in the peritoneal cavity, leading to abdominal distension. Ascites reflects chronic fluid overload and often occurs in liver disease, heart failure, or nephrotic syndrome. This manifestation indicates extracellular fluid accumulation beyond normal vascular and interstitial compartments.