Which PFT finding is typically normal in patients with asthma?

Which PFT finding is typically normal in patients with asthma?

• A. FEV1/FVC ratio
• B. TLC
• C. DLCO
• D. RV

Answer: (C)

In asthma, the primary issue revolves around reversible airway obstruction, which is characterized by the presence of bronchial hyperreactivity and inflammation. When considering pulmonary function tests (PFTs), one of the key findings is that the diffusion capacity of the lungs for carbon monoxide (DLCO) typically remains normal in patients with asthma. This is because asthma does not typically result in intrinsic lung parenchymal disease or vascular complications that would impair diffusion. The forced expiratory volume in one second (FEV1) and its ratio with forced vital capacity (FVC) are often decreased during asthma exacerbations due to obstruction, while total lung capacity (TLC) may vary depending on the patient’s condition and is not always normal in those with asthma, particularly if there is any associated hyperinflation. Residual volume (RV) can be increased due to air trapping during asthma attacks, reflecting impaired airflow. Thus, the normal DLCO in asthma patients indicates that the gas exchange surface area in the lungs is still intact, which distinguishes asthma from other restrictive or obstructive lung diseases that affect gas exchange. This is crucial for differentiating asthma from other conditions that may exhibit similar symptoms but involve greater impairment of lung function.

In asthma, the primary issue revolves around reversible airway obstruction, which is characterized by the presence of bronchial hyperreactivity and inflammation. When considering pulmonary function tests (PFTs), one of the key findings is that the diffusion capacity of the lungs for carbon monoxide (DLCO) typically remains normal in patients with asthma. This is because asthma does not typically result in intrinsic lung parenchymal disease or vascular complications that would impair diffusion.

The forced expiratory volume in one second (FEV1) and its ratio with forced vital capacity (FVC) are often decreased during asthma exacerbations due to obstruction, while total lung capacity (TLC) may vary depending on the patient’s condition and is not always normal in those with asthma, particularly if there is any associated hyperinflation. Residual volume (RV) can be increased due to air trapping during asthma attacks, reflecting impaired airflow.

Thus, the normal DLCO in asthma patients indicates that the gas exchange surface area in the lungs is still intact, which distinguishes asthma from other restrictive or obstructive lung diseases that affect gas exchange. This is crucial for differentiating asthma from other conditions that may exhibit similar symptoms but involve greater impairment of lung function.