1. ^{Increased respiratory efforts associated with obstructive airway disease}
2. ^{Increased chest wall compliance associated with obesity}
3. ^{Decreased lung compliance associated with acute respiratory distress syndrome}
4. ^{Fatigue due to excess work in inflating the emphysematous lung.}

Answer: The answer is (b). The pathophysiological mechanisms contributing to dyspnea include increased respiratory efforts to fill an obstructed lung, decreased lung compliance in conditions like heart failure, interstitial lung disease and acute respiratory distress syndrome, decreased chest wall compliance and conditions where there is respiratory muscle fatigue due to over work. In obesity the chest wall compliance is decreased and hence it causes dyspnea.

1. ^Asthma
2. ^Pneumonia
3. ^{Acute respiratory distress syndrome}
4. ^{Metabolic alkalosis}

Answer: The answer is (d). The list of common causes for acute dyspnea includes acute severe asthma, lung infections, acute pulmonary edema, pneumothorax, acute respiratory distress syndrome and acute pulmonary embolism. Metabolic alkalosis does not cause dyspnea. There might be tachypnea in case of metabolic acidosis as a compensatory mechanism.