Preoperative physiologic pulmonary evaluation for lung resection

INTRODUCTION — Lung resection is frequently considered in patients with lung cancer, and less commonly, in patients with some benign disorders (eg, localized bronchiectasis). For patients with lung cancer, surgery (typically lobectomy or pneumonectomy) is the only cure and is associated with the best long term survival; thus, pushing the boundaries of resectability in the lung cancer population is critical.

In many cases surgical resection needs to be considered in patients with impaired pulmonary function who have risk factors for complications. The evaluation involves assessing the effect of resection on the postoperative level of lung function as well as on the development of cardiopulmonary complications. In this topic, we discuss the approach to assessing the effect of resection on postoperative lung function. Importantly, the recommendations outlined in this topic assume that the cardiovascular risk is low. General preoperative pulmonary and cardiovascular assessments are discussed separately. (See "Evaluation of perioperative pulmonary risk" and "Evaluation of cardiac risk prior to noncardiac surgery".)

GUIDELINES — Most recommendations for lung resection have been informed by the American College of Chest Physicians (algorithm 1) [1] and the European Respiratory Society/European Society of Thoracic Surgeons (please refer to Figure 2 in the guidelines) [2]. Similarities and differences among these guidelines are described throughout the text of the individual sections in this topic. There is also an older set of guidelines available from the British Thoracic Society (2001) [3].

INITIAL ASSESSMENT — Initial preoperative evaluation for resective surgery in the office involves a general pulmonary assessment. Pulmonary function testing (PFTs), typically spirometry and diffusing capacity, should also be obtained in patients undergoing lung resection. PFTs are particularly important in those with underlying lung disease for estimating post-resective lung function (eg, chronic obstructive lung disease [COPD] and emphysema).

General assessment including cardiovascular risk — For patients who are being evaluated for pulmonary resective surgery (ie, lobectomy, pneumonectomy, wedge resection), a general history and examination should be performed. The clinician should assess the patient's understanding of the reason for resection and alternatives available. The clinician should also specifically look for a past history of resections (eg, surgery for old tuberculosis or bronchiectasis), COPD or emphysema, cystic lung disease, interstitial lung disease, or mixed components of lung diseases, all of which can affect tolerability of lung resection and post-resective lung function.

Patients should also be examined, looking for evidence of old thoracotomy or thoracoscopy scars and for signs of chronic hyperinflation (eg, increased resonance to percussion, accessory muscle use, pursed lip breathing, paradoxical retraction of the lower interspaces during inspiration [ie, Hoover's sign]) or severe restriction (eg, limited chest expansion).

Chest computed tomography — With the specific resective surgery in mind (ie, pneumonectomy versus lobectomy), imaging should be evaluated for the anatomy of the region of the lung to be resected, relationship of the disease to adjacent structures, and the possible presence of disease in lung tissue that will not be resected. Chest computed tomography (CT) best serves this purpose and is typically already available. The same chest CT can additionally be used to count segments for postoperative lung function prediction.

Patients undergoing resection are often at risk for other general, pulmonary, and cardiovascular complications, the evaluation for which is discussed separately. (See "Evaluation of cardiac risk prior to noncardiac surgery" and "Evaluation of perioperative pulmonary risk".)

Preoperative pulmonary function — We agree with guidelines that the forced expiratory volume in one second (FEV₁; ie, spirometry) and the diffusing capacity for carbon monoxide (DLCO) should be measured in all patients in whom resectional surgery is being considered [1-3]. Although lung volumes are also classically measured, they do not factor in to predicting postoperative pulmonary function following resection. If testing has not been performed within the previous 6 to 12 months, new testing should be requested. (See "Overview of pulmonary function testing in adults".)

Spirometry and diffusing capacity — The FEV₁ and DLCO have become the primary values used for preoperative assessment. Their main utility is to distinguish patients who are at low risk of surgery (both values are greater than or equal to 80 percent predicted) from those who may need further evaluation (one or more values are less than 80 percent predicted).

●Spirometry – The FEV₁ correlates well with the degree of respiratory impairment in patients with COPD, and it provides an indirect measure of pulmonary reserve. In studies evaluating a variety of preoperative spirometric values, a reduced preoperative FEV₁ (<60 percent predicted) was the strongest predictor of postoperative complications [4-9].

●Diffusing capacity – Retrospective studies have reported that actual DLCO (as a percent of the predicted value) and predicted postoperative DLCO are the most important predictors of mortality and postoperative complications in patients undergoing resection [10-12]. (See 'Predicted postoperative pulmonary function' below.)

Others — Other measures such as indicators of gas exchange and other PFT parameters, although often performed, are not typically predictive of mortality or postoperative lung function and do not assist in determining optimal amounts of lung that can be resected.

Arterial blood gases — Arterial blood gases have not proved to be as useful as measuring FEV₁ and DLCO. However, they may be indicated in the general assessment of patients undergoing surgery, which is discussed separately. (See "Evaluation of perioperative pulmonary risk".)

●Arterial oxygen tension (PaO₂) – There are no predictors or formulae that can estimate the chronic need for supplemental oxygen following resective surgery. In patients who are already receiving supplemental oxygen, removal of healthy gas exchanging surface area will likely increase the supplemental oxygen needs, and, as such, would preclude resective surgery. In contrast, the resting arterial PaO₂ may remain the same or improve when regions of the lung that are significantly diseased or obstructed undergo resection [13,14].

●Arterial carbon dioxide tension (PaCO₂) – Hypercapnia (ie, PaCO₂ greater than 45 mmHg) has traditionally been considered a significant risk factor for pulmonary resection [14], although newer studies suggest no difference in the outcome [15,16]. However, hypercapnia may be a marker of poor underlying lung function. Thus, although hypercapnia, per se, is not a contraindication to surgery, surgery is frequently precluded in hypercapnic patients because of a low predicted postoperative FEV₁ or poor exercise performance.

Maximum voluntary ventilation — Maximal voluntary ventilation (MVV) represents an integrated test that takes into account both airflow and muscle strength. However, its strong dependence on patient effort has led to its removal from most standard pulmonary function testing, and it is now rarely used for preoperative evaluation.

SELECTING PATIENTS FOR FURTHER TESTING (ACCP APPROACH) — We adhere to the American College of Chest Physicians (ACCP) algorithm when evaluating patients for resective surgery [1]. The approach outlined by the ACCP algorithm selects patients for further testing based upon the results of initial preoperative forced expiratory volume in one second (FEV₁) and diffusing capacity for carbon monoxide (DLCO). It is important to recognize that these guidelines were written using data derived from the lung cancer population, which is the population in whom resective surgery is most commonly performed. Similar principles are used for patients undergoing resective surgery for benign disease. Importantly, the recommendations outlined in the sections below assume that the cardiovascular risk is low. (See 'Preoperative FEV1 and DLCO ≥80 percent' below and 'Preoperative FEV1 and DLCO <80 percent' below.)

An alternative approach outlined by the European Respiratory Society/European Society of Thoracic Surgeons (ERS/ESTS) [2] is discussed below. (See 'Alternate approach (ERS/ESTS)' below.)

Despite clear guidelines by both societies, many clinicians do not adhere to them [17].

Preoperative FEV1 and DLCO ≥80 percent — Patients with a preoperative FEV₁ and DLCO that are both ≥80 percent predicted do not need to undergo further testing for assessing postoperative lung function or risk. These patients are considered low risk and can generally tolerate lobectomy or pneumonectomy without resulting in clinically significant residual lung dysfunction. (See 'Low risk' below.)

While in the past an FEV₁ greater than two liters was considered low risk, this absolute cutoff is no longer widely used since it does not take into consideration size, or age [3,18-20].

Preoperative FEV1 and DLCO <80 percent — Patients with a preoperative FEV₁ or DLCO <80 percent predicted need to undergo further evaluation to allow calculation of predicted postoperative (PPO) lung function [1]. While the ACCP supports PPO lung function assessment in this group [1], the ERS/ESTS suggest performing a cardiopulmonary exercise test (CPET), which is also appropriate and the details of which are below [2]. (See 'Integrated cardiopulmonary exercise testing' below and 'Alternate approach (ERS/ESTS)' below.)

Predicted postoperative pulmonary function — PPO values for FEV₁ and DLCO take into account the preoperative values, the amount of lung tissue to be resected (eg, one lung, one lobe, two lobes, partial lobe), and its contribution to overall lung function. The contribution of the region of lung that is to be resected to overall lung function can be determined by quantitative lung scintigraphy or by lung segment counting [3,21-23]; the latter is typically performed on chest computed tomography (CT; these tests are also termed "split lung function studies"). Although both methods can be used for calculating postoperative lung function, perfusion scintigraphy is the most widely used method in patients undergoing pneumonectomy while lung segment counting is recommended for patients undergoing lobectomy [1-3]. Lung segment counting is done on the chest CT performed for lung cancer staging. Scintigraphy plays a limited role in the assessment of patients undergoing lobectomy because of the difficulty in interpreting the contribution of individual lobes to the overall perfusion [2].

Several studies have shown that assessment using volumetric CT correlates better with postoperative lung function than segment counting or scintigraphy [24]. This method provides a 3-D quantification of the volume and relative volume percentages of each lung, and can stratify the results by lung thirds (upper, middle, and lower). Although volumetric CT analysis can also be performed on the routine preoperative chest CT, it is currently seldom used in clinical practice.

In the past, a predicted postpneumonectomy FEV₁ greater than 0.8 L was chosen as the threshold value for surgery [25]. However, we no longer use absolute cutoffs for FEV₁ or DLCO to predict risk of lung resection since functional status may vary depending upon age, gender, and height. Thus, estimates are expressed as percent predicted values rather than absolute numbers. Formulae for these PPO predictions are below.

Formula — Quantitative lung scintigraphy or lung segment counting can be used to determine the PPO FEV₁ and DLCO. Either method can be used but lung scintigraphy may be less accurate in patients undergoing lobectomy than pneumonectomy.

●Quantitative lung scintigraphy: Perfusion method (pneumonectomy) – Although ventilation or perfusion scintigraphy can be used, perfusion methods are more widely used for calculating PPO lung function. We support guidelines from the ACCP that suggest quantitative radionuclide perfusion lung scanning to calculate the PPO FEV₁ in a patient undergoing pneumonectomy (calculator 1) [1]:

The absolute value obtained is then compared with the predicted value for FEV₁ for that individual’s height, age, and gender to obtain the percent predicted postoperative FEV₁. The same formula can be used to predict PPO DLCO by substituting values for diffusing capacity [23,26].

●Segment counting: Anatomic method (lobectomy) – Lung segment counting on chest CT is used most commonly for predicting PPO lung function in patients undergoing lobectomy but can also be used for patients undergoing pneumonectomy. Using this method, the estimated postoperative FEV₁ is calculated by the formula (calculator 2) [27]:

The value obtained is then compared with the predicted value for FEV₁ for that individual’s height, age, and gender to obtain the percent predicted postoperative FEV₁.

Analogous formulas can also be used for calculating PPO DLCO.

Efficacy — Data to support the use of these formulas are limited:

●Older data report good correlation between PPO lung function using scintigraphy and observed postoperative lung function (which was stable over time) following pneumonectomy [28]. However, following lobectomy, there was a disproportionate early loss in postoperative function (compared with the predicted loss), followed by significant functional improvement over time.

●In one study, a PPO FEV₁ that was 40 percent or more of the predicted normal value for that patient was associated with no postoperative mortality (in 47 patients), whereas a value less than 40 percent was associated with 50 percent mortality (in six patients) [23].

●A subsequent study confirmed a correlation between PPO FEV₁ and the likelihood of postoperative complications in patients undergoing lung resection [15]. The odds ratio for complications was 1.46 for each 0.2 L decrease in PPO FEV₁.

●In other studies, high morbidity and mortality were associated with a predicted PPO DLCO below 40 percent [21,23].

Interpreting postoperative predictions — We follow the ACCP algorithm that stratifies patients with a PPO FEV₁ and/or DLCO cutoff of 60 percent predicted to determine who needs additional evaluation in preparation for resective surgery [1]. An alternate approach issued by the ERS/ESTS is discussed below. (See 'Alternate approach (ERS/ESTS)' below.)

Postoperative predicted FEV1 and DLCO ≥60 percent — Based upon the low risk of death and cardiopulmonary complications when both the PPO FEV₁ and PPO DLCO are ≥60 percent, no further testing is necessary. These patients are considered low risk and the patient is deemed to have sufficient pulmonary function to undergo resectional surgery. (See 'Low risk' below.)

Postoperative predicted FEV1 or DLCO <60 percent but ≥30 percent — For patients with either PPO FEV₁ or PPO DLCO <60 percent predicted, and where both values are ≥30 percent predicted, a low technology exercise test (either stair climb or a shuttle walk test) should be performed. There is likely a broad range of risk in this group. Low technology exercise testing is used to select those within this group that may proceed with resective surgery and those that need further testing, namely a CPET.

Incremental shuttle walk test — An incremental shuttle walk test (ISWT) distance greater than 400 meters (ie, 40 x 10 meter "shuttles") has been associated with a maximum oxygen uptake (VO₂max) ≥15 mL/kg/minute [1]; these patients can undergo major thoracic surgery and do not need a CPET. In contrast, patients whose ISWT distance falls below this cutoff are at increased risk for perioperative mortality and cardiopulmonary complications; these patients should undergo CPET with measurement of VO₂max [1]. (See 'Integrated cardiopulmonary exercise testing' below.)

Details of how this test is performed are provided separately. (See "Overview of pulmonary function testing in adults", section on 'Incremental shuttle walk test'.)

Stair climbing — Patients whose exercise ability is equal to or above 22 meters on the stair climbing test are considered low risk and the patient is deemed to have sufficient pulmonary function to undergo resectional surgery (see 'Low risk' below). In contrast, patients whose exercise ability falls below the designated cutoff of 22 meters should undergo CPET for measurement of VO₂max due to the increased risk for perioperative death and cardiopulmonary complications in this population [1]. (See 'Integrated cardiopulmonary exercise testing' below.)

Although poorly standardized, this form of testing has been shown to identify patients at increased risk for lung resection [29-35]. As examples:

●In a prospective series of 640 lobectomy and pneumonectomy patients, attainment of a lower altitude (less than 12 meters) on a symptom-limited stair climbing test was associated with a twofold increase in the risk of cardiopulmonary complications and 13-fold increase in mortality, compared with climbing to a higher altitude (22 meters) [32].

●A prospective series of 160 patients studied one day prior to lung resection found that those who were able to climb more than eight flights of stairs, at their own pace, were less likely to experience complications than those who could climb fewer than seven flights of stairs (6.5 versus 50 percent) [31]. Patients who climbed between seven and eight flights of stairs had an intermediate risk of complications (30 percent).

●In a meta-analysis of 13 articles, being unable to climb more than 10 meters in the stair climb test was associated with a 2.3-fold risk of complications [35].

Although this test is suggested in algorithms of patient selection for thoracic surgery, compliance with it may be poor due to a lack of standardization in pulmonary function laboratories and lack of reimbursement [24].

Postoperative predicted FEV1 and DLCO <30 percent — If either PPO FEV₁ or PPO DLCO is <30 percent, a formal CPET with measurement of VO₂max should be performed.

Guidelines from the ACCP [1] and the ERS/ESTS [2] use a cutoff value for PPO FEV₁ or DLCO of 30 percent (rather than the 40 percent used in several studies), due to improvements in surgical technique and the belief that removal of hyperinflated, poorly functioning lung tissue during surgery ameliorates the calculated loss in lung function through a "lung volume reduction effect."

Integrated cardiopulmonary exercise testing — The most important measurement during CPET that correlates with postoperative complications is the maximum level of work achieved, as measured by the VO₂max; other parameters measured during exercise provide little additional useful data, unless some undiscovered cardiovascular or other limitation to exercise is found incidentally [36]. All guideline groups agree on using cutoff values of 10 and 20 mL/kg/minute, where those who achieve a VO₂max >20 mL/kg/minute (or over 75 percent predicted) are considered low risk, and <10 mL/kg/minute (or <35 percent predicted) are high risk [1]. Patients who achieve a VO₂max between 10 and 20 mL/kg/minute have a wide range of risk and are considered as "moderate risk" per the ACCP guidelines, which suggest individualizing the approach in this population. While the ERS/ESTS also agree on the wide range of risk in this group, they provide further guidance on how to select possible candidates for surgery; further details are provided below. (See 'Determining the risk' below and 'Preoperative FEV1 and DLCO <80 percent' below.)

Studies supporting this approach are limited to observation studies [21,22,37-44]. Most physicians express VO₂max in terms of mL/kg/minute, since it takes into account the patient's body mass and may increase the predictive power of the test [21,38-40]. As an example, one study found that only 1 of 10 patients able to achieve a VO₂max greater than 20 mL/kg/minute had a postoperative complication, whereas all six patients with a VO₂max below 15 mL/kg/minute experienced a postoperative complication [38]. As another example, 20 patients who were considered to be at high risk for resection by standard criteria, but who had a VO₂max of 15 mL/kg/minute or greater, survived surgery and had an acceptable postoperative complication rate [39]. In contrast, several series have demonstrated that patients with VO₂max <10 mL/kg/minute are at very high risk for perioperative complications and mortality [22,40,41].

While it has become standard to express the VO₂max in mL/kg/minute, it may also be used when expressed as a percentage of the predicted value. One report found that a VO₂max <43 percent of predicted was associated with a 90 percent probability of developing serious postoperative complications [42]. A cutoff value below 60 percent predicted was found to be prohibitive for resections involving more than one lobe, whereas a value above 75 percent predicted suggested a good outcome, regardless of the extent of resection. Two subsequent studies, including a total of 280 patients with potentially operable lung cancer, also noted increased mortality among those with VO₂max <50 percent of predicted [43,44].

ALTERNATE APPROACH (ERS/ESTS) — The guidelines of the American College of Chest Physicians (ACCP) (algorithm 1) and those of the European Respiratory Society and the European Society of Thoracic Surgeons (ERS/ESTS) (see figure 2 in the guidelines at http://erj.ersjournals.com/content/34/3/782.full.pdf+html) differ slightly in the exact timing and indications for cardiopulmonary exercise testing (CPET) in the evaluation of a patient for potential lung resection [1,2]. The ERS/ESTS suggest performing CPET in all patients with a preoperative forced expiratory volume in one second (FEV₁) or diffusing capacity for carbon monoxide (DLCO) <80 percent predicted. In contrast, the ACCP uses predicted postoperative (PPO) values in this population to determine who should undergo CPET (see 'Predicted postoperative pulmonary function' above). However, for those who undergo CPET, they agree that patients with a maximal oxygen consumption (VO₂max) >20 mL/kg/minute are at low risk of death or developing complications following resective surgery while patients with a VO₂max <10 mL/kg/minute are considered high risk.

Preoperative FEV1 and DLCO ≥80 percent — Similar to the ACCP guidelines, in the ERS/ESTS algorithm, patients with a preoperative FEV₁ and DLCO ≥80 percent predicted are considered low risk and will likely tolerate resective surgery. (See 'Low risk' below.)

Preoperative FEV1 and DLCO <80 percent — In contrast with the ACCP algorithm, in the ERS/ESTS algorithm, patients with a preoperative FEV₁ or DLCO <80 percent predicted should undergo CPET-determined VO₂max; VO₂max then determines who undergoes PPO lung function testing (see 'Integrated cardiopulmonary exercise testing' above):

●Patients with a VO₂max >20 mL/kg/minute (or >75 percent predicted) are considered low risk and are suitable for any type of lung resection (in agreement with the ACCP guidelines). (See 'Determining the risk' below.)

●Patients with a VO₂max <10 mL/kg/minute (or <35 percent predicted) are considered at high risk and noninvasive options are preferred (in agreement with the ACCP guidelines). (See 'Determining the risk' below.)

●Patients with a VO₂max between 10 and 20 mL/kg/minute (or between 35 and 75 percent predicted) should undergo further testing to determine predicted postoperative FEV₁ and DLCO. The ACCP and ERS/ESTS guidelines agree that the risk of surgery varies significantly among patients with a VO₂max between 10 and 20 mL/kg/minute; some may be suitable for surgery while some may not be well suited; the ERS/ESTS guidelines provide additional guidance for surgical candidacy within this category. (See 'Predicted postoperative pulmonary function' above.)

•If the PPO FEV₁ and PPO DLCO are both >30 percent, then resection up to the calculated extent is allowed. (See 'Moderate risk' below.)

•If at least one parameter (PPO FEV₁ and/or PPO DLCO) is <30 percent, then a PPO peak VO₂max is calculated. Patients with a PPO peak VO₂max <10 mL/kg/minute (or <35 percent predicted) are considered high risk, and minimally invasive or noninvasive options should be sought (see 'High risk' below). In patients with a PPO peak VO₂max ≥10 mL/kg/minute (or >35 percent) predicted, resection is not absolutely contraindicated and resection up to the calculated extent is allowed. However, considerable judgment may be involved, and the patient must understand the higher risk, particularly when the PPO FEV₁ or DLCO is <30 percent. (See 'Moderate risk' below.)

The PPO VO₂max is calculated using data derived from perfusion or other studies that predict postoperative lung function using the following formulas:

-Perfusion scintigraphy for pneumonectomy (perfusion method): PPO peak VO₂max  =  preoperative peak VO₂max  x (1 - fraction of the total perfusion for the lung to be resected)

-Segment counting for lobectomy (anatomic method): PPO peak VO₂max  =  preoperative peak VO₂max  x (1 - number of segments to be resected/total number of lung segments [typically 18]).

DETERMINING THE RISK — Few studies provide strict definitions for risk associated with resective surgery, but the categories below are considered a reasonable guideline.

Low risk — In the low risk category, the expected risk of mortality is below 1 percent. Major anatomic resections can be safely performed in this group without incurring a significant risk of residual lung dysfunction. Patients who are typically included in this category are the following:

●Patients with preoperative forced expiratory volume in one second (FEV₁) and diffusing capacity for carbon monoxide (DLCO) both being ≥80 percent predicted. (See 'Preoperative FEV1 and DLCO ≥80 percent' above.)

●Patients with predicted postoperative (PPO) FEV₁ and PPO DLCO that are both ≥60 percent. (See 'Postoperative predicted FEV1 and DLCO ≥60 percent' above.)

●Patients with PPO FEV₁ or PPO DLCO <60 percent predicted but whose PPO FEV₁ and PPO DLCO are both ≥30 percent and who pass either a stair climb (ie, ≥22 meters) or a shuttle walk test (ie, ≥400 meters). (See 'Postoperative predicted FEV1 or DLCO <60 percent but ≥30 percent' above.)

Moderate risk — For patients in this category, morbidity and mortality of lung resection surgery and residual functional loss following resection may vary widely (eg, mortality may range from 2 to 9 percent). Recommendations for surgery are heavily influenced by the values of predicted postoperative testing, exercise tolerance, and extent of resection. Risks and benefits of the operation should be thoroughly discussed with the patient. (See 'Postoperative predicted FEV1 and DLCO <30 percent' above and 'Integrated cardiopulmonary exercise testing' above.)

Patients included in this category are those with maximal oxygen consumption (VO₂max) values between 10 and 20 mL/kg/minute. The European Respiratory Society/European Society of Thoracic Surgery (ERS/ESTS) guidelines suggest managing this group by calculating the PPO VO₂max, the details of which are discussed above [2]. (See 'Alternate approach (ERS/ESTS)' above.)

High risk — The risk of mortality in this group is generally higher than 10 percent. Considerable risk of severe cardiopulmonary morbidity and residual functional loss is expected. Patients should be counseled about alternative surgical (eg, minor resections or minimally invasive surgery) or nonsurgical options. (See 'Integrated cardiopulmonary exercise testing' above and "Systemic therapy in resectable non-small cell lung cancer" and "Stereotactic body radiation therapy for lung tumors".)

SPECIAL POPULATIONS

Combined resection and lung volume reduction surgery — Guidelines from the American College of Chest Physicians (ACCP) suggest that for patients undergoing resection for lung cancer, combining resective surgery with lung volume reduction surgery (LVRS) is appropriate [1]; this is predicated on the cancer being located in an area of upper lobe emphysema, and the patient's preoperative forced expiratory volume in one second (FEV₁) and diffusing capacity for carbon monoxide (DLCO) both being >20 percent predicted. Optimal patient selection criteria have not been precisely defined for this combined approach, and predicting postoperative lung function following combined LVRS and resective surgery is challenging since the FEV₁ and DLCO are expected to improve following LVRS but worsen following resection. Further details on LVRS are provided separately. (See "Lung volume reduction surgery in COPD".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Chronic obstructive pulmonary disease" and "Society guideline links: Diagnosis and management of lung cancer".)

SUMMARY AND RECOMMENDATIONS

●Scope – The most common indication for lung resection is lung cancer, but resective surgery may also be indicated in patients with some benign lung disorders (eg, localized bronchiectasis). In many cases surgical resection needs to be considered in patients with impaired pulmonary function. Patients should be assessed to determine the effect of resection on the postoperative level of lung function as well as on the risk for development of cardiopulmonary complications. Guidelines from the American College of Chest Physicians (ACCP) are provided in the algorithm (algorithm 1). Guidelines from the European Respiratory Society (ERS)/European Society of Thoracic Surgery (ESTS) can be accessed in Figure 2 at the following site http://erj.ersjournals.com/content/34/3/782.full.pdf+html. (See 'Introduction' above and 'Guidelines' above.)

●Initial assessment – Initial preoperative evaluation for resective surgery involves a general pulmonary assessment and pulmonary function tests (PFTs). Specifically, the forced expiratory volume in one second (FEV₁) and diffusing capacity for carbon monoxide (DLCO) are the most useful PFT measurements that help predict tolerability of resection and the need for additional testing. (See 'Initial assessment' above.)

●FEV₁ and DLCO ≥80 percent – Patients with a preoperative FEV₁ and DLCO that are both ≥80 percent predicted do not need to undergo further testing. These patients are considered low risk and can generally tolerate lobectomy or pneumonectomy without resulting in residual dysfunction. (See 'Preoperative FEV1 and DLCO ≥80 percent' above and 'Low risk' above.)

●FEV₁ and DLCO <80 percent – Patients with a preoperative FEV₁ or DLCO <80 percent predicted should have their predicted postoperative (PPO) FEV₁ and DLCO calculated. While the ACCP supports this approach, the ERS/ESTS suggest performing a cardiopulmonary exercise test (CPET) in this population, which is also appropriate. (See 'Preoperative FEV1 and DLCO <80 percent' above.)

●Calculating the PPO FEV₁ and DLCO – The PPO FEV₁ and DLCO should be calculated based upon the preoperative values and the fractional functional contribution of the lung to be resected (calculator 1 and calculator 2). The fractional contribution of the lung to be resected can be estimated with quantitative perfusion scanning or anatomic calculation of the number of segments to be resected. (See 'Predicted postoperative pulmonary function' above.)

•PPO FEV₁ and PPO DLCO ≥60 percent – Patients with both PPO FEV₁ and PPO DLCO ≥60 percent predicted are considered low risk and should tolerate surgical lobectomy or pneumonectomy. (See 'Interpreting postoperative predictions' above and 'Postoperative predicted FEV1 and DLCO ≥60 percent' above.)

•PPO FEV₁ or PPO DLCO <60 percent – For patients with either PPO FEV₁ or PPO DLCO <60 percent predicted, but both ≥30 percent predicted, a low technology exercise test (either stair climb or a shuttle walk test) should be performed. (See 'Interpreting postoperative predictions' above and 'Postoperative predicted FEV1 or DLCO <60 percent but ≥30 percent' above.)

-Patients who can climb ≥22 meters (on a stair climb test) or walk ≥400 meters (on a shuttle walk test) are considered low risk and should tolerate resective surgery. (See 'Stair climbing' above and 'Incremental shuttle walk test' above.)

-For patients who fail to meet cutoffs for the stair climb (ie, <22 meters) or shuttle walk test (ie, <400 meters), a formal CPET is indicated with measurement of maximal oxygen consumption (VO₂max).

•PPO FEV₁ or PPO DLCO <30 percent – For patients with either the PPO FEV₁ or PPO DLCO <30 percent, a CPET is indicated with measurement of VO₂max. (See 'Interpreting postoperative predictions' above and 'Postoperative predicted FEV1 and DLCO <30 percent' above.)

●CPET – For patients who undergo CPET, we suggest the following (see 'Integrated cardiopulmonary exercise testing' above):

•VO₂max >20 mL/kg/minute – Patients who can achieve a VO₂max >20 mL/kg/minute (or >75 percent predicted) are likely to have an acceptable rate of postoperative complications and should tolerate resective surgery. (See 'Low risk' above.)

•VO₂max <10 mL/kg/minute – Patients with a VO₂max <10 mL/kg/minute (or less than 35 percent predicted) have an unacceptably high risk for the development of serious complications, including death, from resective lung surgery. These patients are best managed by minimally invasive or nonsurgical modalities. (See 'High risk' above.)

•VO₂max between 10 and 20 mL/kg/minute – Patients that achieve a VO₂max between 10 and 20 mL/kg/minute have a wide range of risk and are considered as "moderate risk" per the ACCP guidelines, which suggest individualizing the approach in this population. While the ERS/ESTS also agree on the wide range of risk in this group, they provide further guidance on how to select possible candidates for surgery. We agree with the ERS/ESTS approach that calculates the PPO VO₂max in this population. If the PPO VO₂max is <10 mL/kg/minute (or <35 percent), surgical candidacy is poor and minimal or nonresectional options should be sought. On the other hand, if the PPO VO₂max is ≥10 mL/kg/minute (or ≥35 percent), resection up to the calculated extent is allowed; however, the patient must understand the higher risk, particularly if either the PPO FEV₁ or DLCO is <30 percent predicted. (See 'Moderate risk' above and 'Integrated cardiopulmonary exercise testing' above and 'Alternate approach (ERS/ESTS)' above.)