Restrictive Lung Disease (RLD)

Confirm the pattern - TLC below 80% predicted is the diagnostic finding; spirometry alone only suggests restriction. Expect a reduced FVC with a preserved or increased FEV1/FVC and a convex flow-volume curve, and read DLCO alongside it — a low DLCO points at parenchymal disease rather than a chest-wall or neuromuscular load.

Know which mechanism you are facing - intrinsic parenchymal disease is diffusion impairment plus shunt, so raising FiO2 buys less than you expect. Extrinsic disease is pump failure and answers to ventilatory support. The distinction decides whether you are chasing oxygenation or ventilation.

Ventilate to protect the lung - low tidal volume scaled to predicted body weight, PEEP, an extended inspiratory time, and recruitment maneuvers. The older habit of 10 to 15 mL/kg with zero end-expiratory pressure is the recipe for volutrauma, barotrauma, and atelectrauma.

Watch driving pressure - it is the ventilator number that tracks with postoperative pulmonary complications, and it falls when tidal volume and PEEP are titrated together rather than separately.

Rate compensates, not volume - these patients hold their CO2 normal by breathing fast, and hypercapnia only appears late in the disease. When you drop tidal volume, put the minute ventilation back with rate.

Position costs volume - supine and head-down let the abdomen splint the diaphragm, which is the entire mechanism in ascites and central obesity. Under anesthesia FRC falls roughly 50% in the patient with obesity versus about 20% in the non-obese patient.

Right heart is the silent comorbidity - chronic hypoxemia and distorted lung architecture drive pulmonary hypertension and cor pulmonale, so hypoxemia, hypercarbia, and acidosis all raise pulmonary vascular resistance at the worst moment. Get an echo if there are signs of heart strain.

Plan the back end before induction - the pulmonary complications that follow are pneumonia, atelectasis needing bronchoscopy, and respiratory failure. Decide in advance whether this patient extubates in the room or goes to the unit still ventilated.

Restrictive lung disease is a family of disorders that share one mechanic: the lungs will not expand. Total lung capacity and FVC fall while expiratory flow is preserved, so the FEV1/FVC ratio stays normal or rises — the mirror image of the obstructive pattern. Intrinsic causes scar the parenchyma (interstitial lung disease, sarcoidosis, occupational exposure), thickening the alveolar septa and dropping DLCO. Extrinsic causes load the pump instead: kyphoscoliosis, ankylosing spondylitis, obesity, ascites, pleural effusion, neuromuscular weakness. Either way compliance falls, so every milliliter of tidal volume costs more pressure and more work of breathing. Hypoxemia follows from ventilation-perfusion mismatch and intrapulmonary shunt in intrinsic disease and from hypoventilation and pump failure in extrinsic disease, and chronic hypoxemia ends in pulmonary hypertension and cor pulmonale.