What is the estimated postoperative FEV1 (forced expiratory volume in one second) for a patient with emphysema undergoing right upper lobectomy, given a preoperative FEV1 of 1.8 L and using the segment‑counting method?

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Last updated: September 26, 2026 • View editorial policy

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Estimated Postoperative FEV1 Calculation

For a patient with emphysema undergoing right upper lobectomy with a preoperative FEV1 of 1.8 liters, the estimated postoperative FEV1 using the segment counting method would be approximately 1.52 liters.

Calculation Method

Using the BTS/SCTS guideline formula for lobectomy 1:

Estimated postoperative FEV1 = preoperative FEV1 × [(19 – segments removed) / 19]

For right upper lobectomy:

  • Right upper lobe contains 3 segments 1
  • Total lung segments = 19 1
  • Calculation: 1.8 L × [(19 – 3) / 19] = 1.8 L × (16/19) = 1.52 liters

Clinical Context and Risk Stratification

This calculation assumes all segments are ventilated and unobstructed 1. In emphysema patients, if segments are obstructed, the formula must be modified 1:

Modified formula: epoFEV1 = preFEV1 × [(19 – a) – b] / (19 – a)

  • Where a = number of obstructed segments
  • Where b = number of unobstructed segments to be resected

Important Considerations for This Patient

Risk assessment based on the calculated postoperative FEV1:

  • The absolute postoperative FEV1 of 1.52 L exceeds the historical threshold of 0.8 L (800 mL) 1
  • However, you must express this as % predicted to properly stratify risk 1
  • The 2025 ERS/ESTS guidelines recommend stratifying risk using ppoFEV1 categories: ≥80%, 60-79%, 40-59%, and <40% predicted 2

Critical Next Steps

This patient requires:

  1. Calculation of postoperative FEV1 as % predicted using normative values for age, sex, and height 1
  2. Assessment of DLCO (transfer factor) with calculation of predicted postoperative DLCO 1, 2
  3. Oxygen saturation measurement on room air at rest 1

Risk thresholds 1:

  • Average risk: ppoFEV1 >40% predicted AND ppoDLCO >40% predicted AND SaO2 >90%
  • High risk: ppoFEV1 <40% predicted AND ppoDLCO <40% predicted
  • Intermediate: All other combinations → consider exercise testing

Common Pitfalls

The segment counting method tends to underestimate actual postoperative values, particularly in patients with poor baseline lung function 1. This conservative estimate means patients above the threshold are generally suitable for resection 1.

For emphysema patients specifically:

  • The calculation may be inaccurate if the right upper lobe is emphysematous (non-functional tissue) 1
  • Recent evidence suggests the segment method overestimates functional loss after lower lobectomy by approximately 10% but correlates well with upper lobectomy 3
  • Active smokers and younger patients (<60 years) may have greater discrepancies between predicted and actual postoperative function 4

Do not rely solely on absolute FEV1 values - this approach disadvantages women and elderly patients who may have lower absolute values but adequate % predicted values 1.

References

3
Research

[Changing pattern of the respiratory function associated with resected lung lobe].

Kyobu geka. The Japanese journal of thoracic surgery, 2005

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