restrictive pattern
A restrictive pattern is the spirometry signature of lungs that cannot expand to their full size — like a balloon that has lost its stretch or is squeezed in a box. The airways are open and air flows out freely, but there is simply less air to move.
Its hallmark is reduced volumes — a low FVC — with a normal or high FEV1/FVC ratio, because both FEV1 and FVC shrink together. The flow–volume loop looks like a normal loop scaled down to a smaller, narrower shape rather than scooped out.
True restriction is proven only by measuring a reduced total lung capacity; spirometry alone can merely suggest it. Causes fall into two camps: the lung itself is stiff (fibrosis, prior surgery) or something outside the lung limits expansion (obesity, chest-wall deformity, pleural disease, or weak respiratory muscles).
A patient with idiopathic pulmonary fibrosis has FVC 55 percent predicted, a ratio of 0.88, a reduced total lung capacity and a low DLCO — restriction from stiff lung tissue.
Small volumes with a preserved ratio define restriction.
Pairing spirometry with DLCO helps locate the cause: restriction with a low DLCO points to lung-tissue disease such as fibrosis, while restriction with a normal DLCO suggests a chest-wall or neuromuscular cause.