Determining the Slow Vital Capacity (SVC)* and Residual Volume (RV)* allow for assessment of Total Lung Capacity (TLC) which can clarify whether a restrictive or obstructive process is the cause of a decreased Forced Vital Capacity (FVC) and Forced Expiratory Volume in the 1st second (FEV1).
pft at ALLERGY & ASTHMA utilizes inert gas dilution or nitrogen washout to measure lung volumes.
DIFFUSING CAPACITY (DLCO)
The DLCO measures the ability of the lungs to transfer gas from inhaled air in the alveoli to the red blood cells in pulmonary capillaries.
Measuring Diffusing Capacity (DLCO)* is useful in identifying the cause of dyspnea or hypoxemia, monitoring disease progression in interstitial lung disease, and identifying pulmonary hypertension in patients at risk.
A FeNO test, in patients with allergic or eosinophilic asthma, is a way to determine how much airway inflammation is present and how well an inhaled corticosteroid (ICS) is suppressing this inflammation.
From ATS Guidelines, "FeNO offers added advantages for patient care including, but not limited to (1) detecting of eosinophilic airway inflammation, (2) determining the likelihood of corticosteroid responsiveness, (3) monitoring of airway inflammation to determine the potential need for corticosteroid, and (4) unmasking of otherwise unsuspected non-adherence to corticosteroid therapy."
External link to ATS:
Am J Respir Crit Care Med. 2011 Sep 1;184(5):602-15. doi: 10.1164/rccm.9120-11ST.