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Abstract : pIntroduction: Forced expiratory volume in one second (FEV1) is an independent predictor for respiratory morbidity. Reports are varied and controversial substantiating the use of either lung perfusion (Q) or ventilation (V) scintigraphy as a single stage investigation to predict postoperative (ppo) FEV1in patients scheduled for lung resection surgeries. It is said that there is no additional benefit by performing both V/Q scan. As per one of the recommendations, no further respiratory function tests are required for a lobectomy if the postbronchodilator FEV1is gt;1.5 l. We wanted to study the ppo FEV1in patients with FEV1of lt;1.5 L scheduled for lung surgeries. Being a high-risk population, we wanted to assess (a) whether the ppo changes by this combined V/Q imaging and (b) whether the incidence of respiratory complication in the postoperative setting of this subgroup is different, (c) and study the short- and long-term clinical outcome. Materials and Methods: Fifty-two high-risk patients (with comorbidities) and borderline preoperative FEV1of 1.5 L or less planned for lung resection were enroled in this prospective study. V and Q scans were performed, and tracer uptake percentage was tabulated. Results: Tracer uptake in each lung was quantitated. Manual method of ROI drawing is preferred in high risk patients with reduced pulmonary reserve over the automatic method. Based on uptake patterns by V/Q scans, 4 different types of patterns were tabulated. Eighty-eight percentage of centrally placed tumors showed the difference in uptake patterns. Chronic obstructive pulmonary disease patients usually showed more modest ventilatory defects (categorised as type 2 or 3). Lung tumours produce erratic uptake patterns (Type 4) which depend heavily on their location and extent. The range of FEV1predicted was 0.6-1.38 L/min Conclusion: We recommend that combined imaging should be performed in patients with borderline pulmonary reserve to derive the benefit of surgery as it provides a realistic ppo FEV1in patients with moderate to severely damaged lung. Centrally placed hilar or bronchial tumors (even those lt;2 cm in size), produce discrepancies in V/Q distribution pattern. Patient who was thought ineligible for surgery due to low baseline FEV1may be actually be operable by this combined imaging if uptake pattern is better in V or Q scan with a good outcome. Accurate estimation of postop FEV1in fact helps the surgical team to implement measures to prepare high risk patients to reduce postoperative complications, enable faster weaning from ventilatory support and ensure favourable prognosis. © 2018 Indian Journal of Nuclear Medicine | Published by Wolters Kluwer -Medknow./p