How is predicted postoperative FEV₁ calculated for lobectomy?

For anatomic lung resection, predicted postoperative FEV₁ equals preoperative FEV₁ multiplied by one minus the number of functioning segments to be removed divided by the total number of functioning segments. A simple 19-segment count applies only when all segments are functioning and unobstructed.

How is predicted postoperative DLCO calculated for pneumonectomy?

For pneumonectomy, predicted postoperative DLCO equals preoperative DLCO multiplied by one minus the fraction of total perfusion assigned to the lung being removed. Use the quantitative perfusion study rather than an estimated side-to-side contribution.

Does a ppo FEV₁ or DLCO result decide whether lung surgery can proceed?

No. Predicted postoperative values are one component of a physiologic assessment. Exercise capacity, symptoms, cardiovascular risk, imaging, operative approach, functional testing, cancer context, and multidisciplinary evaluation remain important.

Thoracic surgery physiologic assessment

Predicted Postoperative FEV₁ & DLCOlung-resection calculator

Estimate predicted postoperative FEV₁ and DLCO with a transparent segment-count method for lobectomy or a perfusion-based method for pneumonectomy—then place the numbers in their proper clinical context.

Two guideline-based methodsFormula trace shownNo clearance verdict

Educational clinical decision support. These estimates are intended for clinician-facing preoperative discussion in candidates for lung resection. They do not determine operability, quantify an individual complication risk, or replace a thoracic-surgery, pulmonary, anesthesia, or multidisciplinary assessment.

Lung-resection physiologic estimate

Calculate predicted postoperative FEV₁ and DLCO

Choose the method that matches the planned operation. Segment counting estimates lobar or sublobar resection; quantitative perfusion estimates pneumonectomy.

Method

What is planned?

Baseline PFTs

Enter measured preoperative values

Percent-predicted FEV₁ and DLCO are required. Absolute FEV₁ is optional and produces a ppo FEV₁ volume estimate; do not substitute a percent-predicted value for an absolute volume.

Preoperative FEV₁ (optional)

Preoperative FEV₁ % predicted

Preoperative DLCO % predicted

Segment method

Count functioning segments—not simply anatomy

Start with 19 only when all segments are functioning and unobstructed. If imaging or bronchoscopy shows complete obstruction, use the total functioning segments and count only the functioning segments planned for resection.

Total functioning segments

of 19

Functioning segments to resect

segments

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Calculation methods

Match the calculation to the resection

Lobectomy or segmentectomy

Use functioning segment counting: ppo = preoperative value × (1 − a/b), where a is functioning segments resected and b is total functioning segments. A 19-segment count is a starting anatomy—not a substitute for accounting for completely obstructed segments.

This method is typically used for lobectomy. In borderline cases, teams may use imaging-based split-function assessment or quantitative CT as part of the broader evaluation.

Pneumonectomy

Use quantitative perfusion: ppo = preoperative value × (1 − perfusion fraction of lung removed). Enter the perfusion fraction reported for the operative lung, rather than using a generic right/left split.

A ventilation scan may also be used in some pathways, but there is not generally added benefit from performing both ventilation and perfusion studies solely for this calculation.

Use the estimate well

A physiologic input—not an answer by itself

FEV₁ and DLCO should be measured in candidates for lung-cancer resection, and predicted postoperative values help identify who may need further functional assessment. Common pathways treat values above 60% predicted as a more reassuring starting point, values from 30% to 60% as requiring fuller functional context, and values below 30% as a reason to consider formal CPET if surgery remains under consideration.

Those ranges are pathway prompts, not universal rules. Functional capacity, CPET or lower-technology tests, symptoms, cardiovascular risk, gas exchange, radiographic distribution, operation type, minimally invasive options, and oncologic alternatives all matter.

Review GLI spirometry Review perioperative pulmonary risk

Important boundaries

Do not use ppo FEV₁ or ppo DLCO alone to select or exclude a patient from resection.
Do not use a generic 19-segment count when complete obstruction changes functional segments.
For pneumonectomy, use quantitative perfusion rather than an estimated lung-side split.
Do not treat this result as a personalized probability of mortality or complications.

Frequently asked questions

Predicted postoperative lung-function estimates

Which method should I use for lobectomy?

Use the segment-count method for lobectomy, segmentectomy, or other anatomic segment resection. The calculator uses ppo = preoperative value × (1 − functioning segments resected / total functioning segments). Enter 19 only when all segments are functioning and unobstructed.

Which method should I use for pneumonectomy?

Use quantitative perfusion for pneumonectomy. The calculator uses ppo = preoperative value × (1 − fraction of total perfusion assigned to the resected lung). Use the value reported by the study rather than estimating right-versus-left contribution.

What does a ppo FEV₁ or ppo DLCO below 30% predicted mean?

It is a very low predicted reserve that merits specialist assessment. Common pathways use this range to prompt formal cardiopulmonary exercise testing if resection remains under consideration; it is not an automatic finding that surgery must or must not proceed.

Can a normal ppo FEV₁ replace DLCO?

No. DLCO adds information about gas-exchange reserve and can be clinically important even when spirometry is not markedly abnormal. Both should be interpreted with symptoms, functional capacity, imaging, comorbidity, and the planned operation.

Evidence base

Formula sources and clinical context

Evidence and links reviewed September 23, 2026. The calculator retains the published segment and perfusion equations. Threshold context is presented as a prompt for clinical assessment, never as a surgical decision rule.

ERS/ESTS clinical practice guideline on fitness for curative-intent treatment of lung cancer (2025)Current multidisciplinary guideline supporting baseline FEV₁ and DLCO assessment and using physiologic evaluation in the broader curative-treatment pathway.ERS/ESTS guideline: split-function equations and recommendationsDefines functional segment counting for lobectomy and quantitative perfusion for pneumonectomy, with the ppo FEV₁ and DLCO equations used by this calculator.ACCP physiologic evaluation guideline summaryRecommends measuring FEV₁ and DLCO and calculating predicted postoperative values in candidates for lung-cancer resection; very low ppo values prompt further physiologic assessment rather than a calculator-only decision.ERS Breathe review: pulmonary-function prediction in lung-resection candidates (2025)Contemporary review of segment and perfusion methods, evolving thresholds, and the need to combine ppo values with exercise and clinical assessment.

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