"Although not in common usage, the term gas trapping is more accurate 14."
"The presence of air trapping can arise from a number of causes (the mnemonic HSBC can be used to help remember these) but usually suggests airway disease (often small airways disease). Air trapping can occur in isolation, or in association with bronchiectasis, interstitial lung disease, or rarely tree-in-bud opacity, which can help narrow the aetiology 3,6:"
"high BMI / obesity 12,13,15"