**3. Lung function tests**

In the preoperative thoracic surgery the functional assessment schemes have varied over the past 50 years. Most respirotary function tests which were utilized in order to minimize morbidity and postoperative mortality (table 3) are no longer used today, being replaced by simpler techniques that provide similar or better information. Today the process of lung function assessment is spread out over several phases comprising a series of breathing tests that the patients scheduled for thoracic surgery will be given according to their baseline pulmonary function and the amount of lung tissue for resection. These steps complement each other, so that the degree of severity of impairment of lung function is the fact that determines whether or not to go a step higher.


Table 3. Pulmonary function test used in the preoperative assessment. FVC: Forced vital capacity. FEV1: Forced expiratory volume in 1 second. ppo: postoperative. TLC: Total lung capacity. RV: Residual volumen. DLCO: Diffusion capacity of the lung for carbon monoxide. PaO2: Oxygen partial pressure of artery. PaCO2: Carbon dioxide partial pressure of artery. PAP: Pulmonary artery pressure. PVR: Pulmonary vascular resistance. VO2: Oxygen uptake.

Perioperative Pulmonary Functional Assessment 375

complications in patients with preoperative FEV1 greater than 70%. In addition, among these patients, who also have ppo-FEV1 less than 40%, the mortality is 4.8%. These findings explain the so-called "lung volume reduction effect", which shows a reduction of functional loss in patients with airflow limitations, such as, for example, in patients with chronic

A ppo-FEV1 value of 40% is currently being used to distinguish between normal and high risk of complications in thoracic surgery. However, due to improvements in surgical

Although the ppo-FEV1 is fairly accurate in predicting the final residual value of FEV1 within 3-6 months after thoracic surgery, the real value of FEV1 is overestimated in the first postoperative days, when most of the complications occur. In this regard, it has been shown that the first postoperative day and after a lobecctomia the real value of FEV1 was 30% lower than expected. Therefore, it would be a better predictor of complications than the

The current recommendations of the ERS / ESTS Task Force are that the ppo-FEV1 should not only be used to select patients with pulmonary cancer for lung resection, especially in patients with moderate or severe COPD. It is known that in patients with COPD it is likely to overestimate the loss of lung function in the early postoperative stages and ppo-FEV1 does not seem to be a reliable predictor of complications. Finally, a value of ppo-FEV1 less than 30% predicted would be a high risk parameter when included in an algorithm for

The DLCO represents the amount of carbon monoxide trapped by the lungs after inspiration of a small amount of this gas. This test provides us with information about the alveolocapillary membrane, which is responsible for alveolar oxygen exchange. Thus, the DLCO is

Although DLCO is a technique which allows to estimate the risk of postoperative complications, it is not as well studied as FEV1. Several studies have shown that a preoperative DLCO less than 60% predicted was associated with increased mortality and postoperative complications were increased when the DLCO was less than 80% of predicted value (Ferguson et al., 1998). It has also been observed that patients with decreased DLCO (65.3 ± 5.0%) had more respiratory complications than those with normal DLCO (90.1 ± 5.9%) (Wang et al., 1999). In addition, decreased DLCO is related to an increase in the

Therefore, the DLCO is an additional test to spirometry in which if a patient's preoperative functional evaluation has a FEV1 and DLCO greater than or equal to 80%, no additional testings are required. But if a patient has a DLCO lower than 80% despite a FEV1 greater than or equal to 80%, additional tests should be performed to make sure that it is a good candidate for thoracic surgery. This indicates that the DLCO is an important test to predict postoperative complications both in patients without COPD as well as in patients suffering

On the other hand, a value of postoperative DLCO (ppo-DLCO) of 40% is currently being used to distinguish between normal and high risk of complications in patients undergoing lung resection (Wyser et al., 1999) (figure 1). However, taking into account advances in perioperative care and surgical techniques, the allowed limit of ppo-DLCO should be

techniques and perioperative management, the value of ppo-FEV1 could fall to 30%.

assessing pulmonary reserve before thoracic surgery (Brunelli et al., 2009).

used to evaluate the surgical risk in patients scheduled for thoracic surgery.

frequency of hospital readmissions and poor quality of life for the long term.

**3.2 Diffusing capacity of the lung for carbon monoxide** 

from this pathology (Ferguson et al., 2008).

lowered to 30%.

obstructive lung disease (COPD) (Sekine et al., 2003).

ppo-FEV1 was (Varela et al., 2007).

#### **3.1 Spirometry**

Spirometry is a simple, inexpensive test of high reproducibility, easy to perform. From the standpoint of the preoperative evaluation the most important variables are the FEV1 and FVC. In the early 1950s spirometry was already considered as the most valid technique to assess morbidity and postoperative mortality in the thoracic surgery.

The first authors who used the predictive power of FEV1 in such surgery observed that the complications derived from the resection of bronchial carcinoma were associated with absolute values of FEV1 lower than 2 liters (Boushy et al., 1971). Subsequently, the measurements of spirometry were combined with those of lung volumes and there was observed an increase in complications with a FEV1 less than 1.20 liters, reserve volume (RV) greater than 3.30 liters and total lung capacity (TLC) greater than 7.90 liters (Lockwood, 1973). On the other hand, there was an attempt to link the value of FEV1 with the type of lung resection and it was noticed that the requirement for pneumonectomy was a FEV1 more than 2 liters, for lobectomy more than 1 liter and for segmentectomy or wedge resection more than 0.6 liter (Miller et al., 1981).

Considering FEV1 in absolute values can lead to errors in the estimation of lung function, especially in patients of advanced age or low height. In this sense, there have been some studies whose data contemplate a reduction in complications when the FEV1 is greater than 60% (Richter et al., 1997) or 89 ± 19% (Wang et al., 2000) of predicted values (table 4). Therefore, it is preferable to place greater emphasis on FEV1 percentage value in relation to its theoretical value than to the absolute one. In addition, the highest possible FEV1 will be chosen using the available therapeutic arsenal (smoking cessation, pulmonary rehabilitation or drug treatment with bronchodilators or corticosteroids). Finally, we could say that for thoracic surgery the advisable value of FEV1 is greater than or equal to 80%.


Table 4. Preoperative lung function variables in relation to complications. FEV1: Forced expiratory volume in 1 second. FVC: Forced vital capacity. RV: Residual volume. TLC: Total lung capacity. DLCO: Diffusion capacity of the lung for carbon monoxide. VA: Alveolar volume. ns: not significant (Wang et al., 2000).

In the algorithms used for the functional assessment of candidates for lung resection, the value of postoperative FEV1 (ppo-FEV1) plays an important role in the alternative to perform further tests or exclude patients from surgery without performing these tests (Wyser et al., 1999) (figure 1). In this sense, a value of ppo-FEV1 less than 40% of predicted increases the risk of perioperative complications and mortality by 16-50% (Pierce et al., 1994), being higher (60%) when ppo-FEV1 is less than 30% (Nakahara et al., 1985).

Even today there is a disagreement about whether ppo-FEV1 is a good predictor of perioperative complications or not. It has been seen that ppo-FEV1 is not a good predictor of

Spirometry is a simple, inexpensive test of high reproducibility, easy to perform. From the standpoint of the preoperative evaluation the most important variables are the FEV1 and FVC. In the early 1950s spirometry was already considered as the most valid technique to

The first authors who used the predictive power of FEV1 in such surgery observed that the complications derived from the resection of bronchial carcinoma were associated with absolute values of FEV1 lower than 2 liters (Boushy et al., 1971). Subsequently, the measurements of spirometry were combined with those of lung volumes and there was observed an increase in complications with a FEV1 less than 1.20 liters, reserve volume (RV) greater than 3.30 liters and total lung capacity (TLC) greater than 7.90 liters (Lockwood, 1973). On the other hand, there was an attempt to link the value of FEV1 with the type of lung resection and it was noticed that the requirement for pneumonectomy was a FEV1 more than 2 liters, for lobectomy more than 1 liter and for segmentectomy or wedge

Considering FEV1 in absolute values can lead to errors in the estimation of lung function, especially in patients of advanced age or low height. In this sense, there have been some studies whose data contemplate a reduction in complications when the FEV1 is greater than 60% (Richter et al., 1997) or 89 ± 19% (Wang et al., 2000) of predicted values (table 4). Therefore, it is preferable to place greater emphasis on FEV1 percentage value in relation to its theoretical value than to the absolute one. In addition, the highest possible FEV1 will be chosen using the available therapeutic arsenal (smoking cessation, pulmonary rehabilitation or drug treatment with bronchodilators or corticosteroids). Finally, we could say that for thoracic surgery the advisable value of FEV1 is greater than or equal to 80%.

Table 4. Preoperative lung function variables in relation to complications. FEV1: Forced expiratory volume in 1 second. FVC: Forced vital capacity. RV: Residual volume. TLC: Total lung capacity. DLCO: Diffusion capacity of the lung for carbon monoxide. VA: Alveolar

1994), being higher (60%) when ppo-FEV1 is less than 30% (Nakahara et al., 1985).

In the algorithms used for the functional assessment of candidates for lung resection, the value of postoperative FEV1 (ppo-FEV1) plays an important role in the alternative to perform further tests or exclude patients from surgery without performing these tests (Wyser et al., 1999) (figure 1). In this sense, a value of ppo-FEV1 less than 40% of predicted increases the risk of perioperative complications and mortality by 16-50% (Pierce et al.,

Even today there is a disagreement about whether ppo-FEV1 is a good predictor of perioperative complications or not. It has been seen that ppo-FEV1 is not a good predictor of

assess morbidity and postoperative mortality in the thoracic surgery.

resection more than 0.6 liter (Miller et al., 1981).

volume. ns: not significant (Wang et al., 2000).

**3.1 Spirometry** 

complications in patients with preoperative FEV1 greater than 70%. In addition, among these patients, who also have ppo-FEV1 less than 40%, the mortality is 4.8%. These findings explain the so-called "lung volume reduction effect", which shows a reduction of functional loss in patients with airflow limitations, such as, for example, in patients with chronic obstructive lung disease (COPD) (Sekine et al., 2003).

A ppo-FEV1 value of 40% is currently being used to distinguish between normal and high risk of complications in thoracic surgery. However, due to improvements in surgical techniques and perioperative management, the value of ppo-FEV1 could fall to 30%.

Although the ppo-FEV1 is fairly accurate in predicting the final residual value of FEV1 within 3-6 months after thoracic surgery, the real value of FEV1 is overestimated in the first postoperative days, when most of the complications occur. In this regard, it has been shown that the first postoperative day and after a lobecctomia the real value of FEV1 was 30% lower than expected. Therefore, it would be a better predictor of complications than the ppo-FEV1 was (Varela et al., 2007).

The current recommendations of the ERS / ESTS Task Force are that the ppo-FEV1 should not only be used to select patients with pulmonary cancer for lung resection, especially in patients with moderate or severe COPD. It is known that in patients with COPD it is likely to overestimate the loss of lung function in the early postoperative stages and ppo-FEV1 does not seem to be a reliable predictor of complications. Finally, a value of ppo-FEV1 less than 30% predicted would be a high risk parameter when included in an algorithm for assessing pulmonary reserve before thoracic surgery (Brunelli et al., 2009).

#### **3.2 Diffusing capacity of the lung for carbon monoxide**

The DLCO represents the amount of carbon monoxide trapped by the lungs after inspiration of a small amount of this gas. This test provides us with information about the alveolocapillary membrane, which is responsible for alveolar oxygen exchange. Thus, the DLCO is used to evaluate the surgical risk in patients scheduled for thoracic surgery.

Although DLCO is a technique which allows to estimate the risk of postoperative complications, it is not as well studied as FEV1. Several studies have shown that a preoperative DLCO less than 60% predicted was associated with increased mortality and postoperative complications were increased when the DLCO was less than 80% of predicted value (Ferguson et al., 1998). It has also been observed that patients with decreased DLCO (65.3 ± 5.0%) had more respiratory complications than those with normal DLCO (90.1 ± 5.9%) (Wang et al., 1999). In addition, decreased DLCO is related to an increase in the frequency of hospital readmissions and poor quality of life for the long term.

Therefore, the DLCO is an additional test to spirometry in which if a patient's preoperative functional evaluation has a FEV1 and DLCO greater than or equal to 80%, no additional testings are required. But if a patient has a DLCO lower than 80% despite a FEV1 greater than or equal to 80%, additional tests should be performed to make sure that it is a good candidate for thoracic surgery. This indicates that the DLCO is an important test to predict postoperative complications both in patients without COPD as well as in patients suffering from this pathology (Ferguson et al., 2008).

On the other hand, a value of postoperative DLCO (ppo-DLCO) of 40% is currently being used to distinguish between normal and high risk of complications in patients undergoing lung resection (Wyser et al., 1999) (figure 1). However, taking into account advances in perioperative care and surgical techniques, the allowed limit of ppo-DLCO should be lowered to 30%.

Perioperative Pulmonary Functional Assessment 377

surgery. However, they do not provide as useful measurement as FEV1 or DLCO in the

In relation to arterial oxygen pressure (PaO2), few studies describe the exact role of this parameter in the assessment of perioperative risk. In some of them it has been shown that PaO2 below 50 mmHg is associated with postoperative complications (Mittman & Bruderman., 1977). Furthermore, sometimes hypoxemia in patients with bronchial carcinoma may be due to a shunt secondary to pulmonary atelectasis that is improved after

With regard to the blood pressure of CO2 (PaCO2), it has been postulated that hypercapnia (PaCO2 greater than 45 mmHg) involves an increase in postoperative complications (Meyer-Erkelenz et al., 1980). However, one study has demonstrated that patients with severe airflow obstruction (FEV1 40 ± 6%) and PaCO2 of 44 ± 4 mmHg, did not have any complications after lobectomy (Morice et al., 1992) (table 5). In this sense, other authors have also come to the conclusion that hypercapnia is not a risk factor for the presence of postoperative pulmonary complications (Miller et al., 1981). Therefore, although there is no consensus about the usefulness of the arterial gasometry in the perioperative functional assessment, it seems clear

Table 5. Relationship among spirometry, arterial blood gases and exercise testing in patients undergoing lung resection. FVC: Forced vital capacity. FEV1: Forced expiratory volume in 1 s. DCO: Diffusion capacity of the lung for carbon monoxide. TLC: Total lung capacity. PO2: Oxygen partial pressure of artery. PCO2: Carbon dioxide partial pressure of artery.

The quantitative perfusion scintigraphy is based on the radiation emitted by an isotope that is taken up by the lungs after being injected intravenously. The percentage of radioactivity is associated with lung function, the right lung being the largest (55% of the total radiation).

The calculation of ppo-FEV1 in patients scheduled for pneumonectomy, from preoperative FEV1 and lung perfusion scintigraphy, is performed as follows (Kristersson et al., 1972):

ppo FEV1 preoperative FEV1 x % of perfusion of the undisturbed lun − = g

Therefore, if such a patient is a candidate for left pneumonectomy and has a 3-liter preoperative FEV1 and the scintigraphy shows 30% perfusion in the left lung and 70% in the

VO2: Oxygen uptake. RV: Right ventricule. (Morice et al., 1992).

The left lung is responsible for the remaining 45% (figure 2).

**3.4 Quantitative ventilation/perfusion scintigraphy** 

right, the value of FEV1 postpneumonectomy is:

that hypercapnia should not exclude patients who are candidates for lung resection.

perioperative functional assessment.

the lung resection.

Fig. 1. Proposed algorithm for the assessment of the cardio-respiratory reserves of lung resection candidates. Tl 5 thallium; Tc 5 technetium. ECG: electrocardiogram. FEV1: Forced expiratory volume in 1 second. DLCO: Diffusion capacity of the lung for carbon monoxide. ppo: postoperative. VO2: Oxygen uptake. (Wyser et al., 1999).

The current recommendations of the ERS / ESTS Task Force indicate that the DLCO should be a routine measurement of functional evaluation of candidates for lung resection, especially if the spirometry is altered. The threshold value of ppo-DLCO of 30% is high risk when included in an algorithm for the assessment of pulmonary reserve before thoracic surgery (Brunelli et al., 2009).

#### **3.3 Measurement of gas exchange**

Arterial gasometry, is a test that is requested routinely in patients about to undergo thoracic surgery. Unlike spirometry, arterial blood gases values provide some more direct information about the problem with the gas exchange that is often present in this type of

Fig. 1. Proposed algorithm for the assessment of the cardio-respiratory reserves of lung resection candidates. Tl 5 thallium; Tc 5 technetium. ECG: electrocardiogram. FEV1: Forced expiratory volume in 1 second. DLCO: Diffusion capacity of the lung for carbon monoxide.

The current recommendations of the ERS / ESTS Task Force indicate that the DLCO should be a routine measurement of functional evaluation of candidates for lung resection, especially if the spirometry is altered. The threshold value of ppo-DLCO of 30% is high risk when included in an algorithm for the assessment of pulmonary reserve before thoracic

Arterial gasometry, is a test that is requested routinely in patients about to undergo thoracic surgery. Unlike spirometry, arterial blood gases values provide some more direct information about the problem with the gas exchange that is often present in this type of

ppo: postoperative. VO2: Oxygen uptake. (Wyser et al., 1999).

surgery (Brunelli et al., 2009).

**3.3 Measurement of gas exchange** 

surgery. However, they do not provide as useful measurement as FEV1 or DLCO in the perioperative functional assessment.

In relation to arterial oxygen pressure (PaO2), few studies describe the exact role of this parameter in the assessment of perioperative risk. In some of them it has been shown that PaO2 below 50 mmHg is associated with postoperative complications (Mittman & Bruderman., 1977). Furthermore, sometimes hypoxemia in patients with bronchial carcinoma may be due to a shunt secondary to pulmonary atelectasis that is improved after the lung resection.

With regard to the blood pressure of CO2 (PaCO2), it has been postulated that hypercapnia (PaCO2 greater than 45 mmHg) involves an increase in postoperative complications (Meyer-Erkelenz et al., 1980). However, one study has demonstrated that patients with severe airflow obstruction (FEV1 40 ± 6%) and PaCO2 of 44 ± 4 mmHg, did not have any complications after lobectomy (Morice et al., 1992) (table 5). In this sense, other authors have also come to the conclusion that hypercapnia is not a risk factor for the presence of postoperative pulmonary complications (Miller et al., 1981). Therefore, although there is no consensus about the usefulness of the arterial gasometry in the perioperative functional assessment, it seems clear that hypercapnia should not exclude patients who are candidates for lung resection.


Table 5. Relationship among spirometry, arterial blood gases and exercise testing in patients undergoing lung resection. FVC: Forced vital capacity. FEV1: Forced expiratory volume in 1 s. DCO: Diffusion capacity of the lung for carbon monoxide. TLC: Total lung capacity. PO2: Oxygen partial pressure of artery. PCO2: Carbon dioxide partial pressure of artery. VO2: Oxygen uptake. RV: Right ventricule. (Morice et al., 1992).

#### **3.4 Quantitative ventilation/perfusion scintigraphy**

The quantitative perfusion scintigraphy is based on the radiation emitted by an isotope that is taken up by the lungs after being injected intravenously. The percentage of radioactivity is associated with lung function, the right lung being the largest (55% of the total radiation). The left lung is responsible for the remaining 45% (figure 2).

The calculation of ppo-FEV1 in patients scheduled for pneumonectomy, from preoperative FEV1 and lung perfusion scintigraphy, is performed as follows (Kristersson et al., 1972):

ppo FEV1 preoperative FEV1 x % of perfusion of the undisturbed lun − = g

Therefore, if such a patient is a candidate for left pneumonectomy and has a 3-liter preoperative FEV1 and the scintigraphy shows 30% perfusion in the left lung and 70% in the right, the value of FEV1 postpneumonectomy is:

Perioperative Pulmonary Functional Assessment 379

It is difficult to establish a definitive cut-off of ppo-FEV1 or ppo-DLCO above which resection of lung parenchyma will be safe. Some authors have estimated 0.8 liters as the limit below which it is unreasonable to perform the resection of the pulmonary parenchyma (Olsen et al., 1974). As an absolute value it can lead to errors, which is why it is better to use

Several studies have shown that in candidates for lung resection, when ppo-FEV1 is greater than 40%, postoperative mortality is reduced (Markos et al., 1989), but other authors did not observe its increase when ppo-FEV1 is less than 40% (Morice et al., 1992). In relation to the ppo-DLCO it has also been noticed that the risk of postoperative complications is greater when the ppo-DLCO is less than 40% (Markos et al., 1989), and even one study estimates that this parameter is the best assessment of mortality and postoperative complications

In practice, the scintigraphy has not been widely used in the functional assessment of patients about to undergo a lobectomy because of the difficulty in interpreting the individual contribution of each of the lobes to the whole of ventilation and perfusion. This could explain why several researchers consider that the simple calculation of the lung segments can predict the ppo-FEV1 as accurately as the ventilation perfusion scintigraphy does (Win et al., 2004). The ventilation scintigraphy has been widely used to predict postoperative lung function in patients with lung cancer who are scheduled for

The correlation between current and predicted ppo-FEV1 using the ventilation/perfusion scintigraphy has been variable with r between 0.67 and 0.9 (Win et al., 2006a). Both the ventilation and perfusion scintigraphies offer a good prediction of postoperative lung function individually, but it seems that there is no additional benefit in the performance of both (Win et al., 2006). However, the interpretation of the results should take into account that these techniques may underestimate the actual postoperative value (Zeiher et al., 1995).

During the exercise the patient is subjected to physical stress so that the whole system that regulates the uptake, transport and use of oxygen can be studied through the exercise test. When the latter is started, the lung increases the ventilation, oxygen uptake (VO2), CO2 production and blood flow similar to that which occurs during the postoperative period

Among all the variables mentioned above, the most important is the peak oxygen uptake (VO2 peak), which gives us an idea of the global response to the effort and is defined as the maximum amount of oxygen a subject can capture, transport and use during the exercise. In addition, during the preoperative evaluation process the VO2 peak is the parameter that estimates the probability of complications best of all. Despite this, the exercise test should be performed only in selected cases (decrease in FEV1 and/or in DLCO below 80%) (Wayser et

**3.5.1 Low-technology exercise; stair climbing, shuttle walk, and 6-min walk tests**  Six-minute walk, stair climbing and shuttle walk tests have proved to be useful for preoperative risk stratification. In this sense, the 6-min walk test has a high reliability in the estimation of VO2 peak in healthy subjects and patients with COPD or those who are about to undergo lung transplantation and, therefore, in assessing the postoperative risk after

the percentage with respect to the theoretical value.

(Ferguson et al., 2008).

**3.5 Exercise test** 

al., 1999).

following the lung resection.

thoracic surgery (Brunelli et al, 2009).

pneumonectomy (Colice et al., 2007).

ppo FEV1 3 litersx 0,7 2,1 liters −= =

It has been shown that there is a good relationship between the ppo-FEV1 and real postoperative FEV1, while the ppo-FEV1 can be 10% lower than the measured FEV1 3 months after the surgery.

Wernley et al. applied the method of lung perfusion scintigraphy to calculate the FEV1 after lobectomy with the following formula (Wernly et al., 1980):

Estimate of the FEV1 loss preoperative FEV1 x % affected lung perfusion x (number of segments in the lobe to be resected / number of segments in the lung) <sup>=</sup>

Perfusion scintigraphy has also been used to calculate ppo-DLCO, using the same formulas for estimating the ppo-FEV1. Therefore, the ppo-DLCO is calculated using the following formula:

ppo DLCO − =preoperative DLCO x % de perfusion of the unresected lung

Fig. 2. Anterior and posterior images from perfusion scintigram. Three equally sized regions of interest over lungs are shown. Counts in each zone are measured. Geometric means of anterior and posterior images are then used to calculate relative perfusion and ventilation for each zone for each lung. By this method, percentages are obtained for upper, middle, and lower zones of right and left lungs for both perfusion and ventilation. (Win et al., 2006).

ppo FEV1 3 litersx 0,7 2,1 liters −= = It has been shown that there is a good relationship between the ppo-FEV1 and real postoperative FEV1, while the ppo-FEV1 can be 10% lower than the measured FEV1 3

Wernley et al. applied the method of lung perfusion scintigraphy to calculate the FEV1 after

Estimate of the FEV1 loss preoperative FEV1 x % affected lung perfusion x (number of

Perfusion scintigraphy has also been used to calculate ppo-DLCO, using the same formulas for estimating the ppo-FEV1. Therefore, the ppo-DLCO is calculated using the following

ppo DLCO − =preoperative DLCO x % de perfusion of the unresected lung

Fig. 2. Anterior and posterior images from perfusion scintigram. Three equally sized regions of interest over lungs are shown. Counts in each zone are measured. Geometric means of anterior and posterior images are then used to calculate relative perfusion and ventilation for each zone for each lung. By this method, percentages are obtained for upper, middle, and lower zones of

right and left lungs for both perfusion and ventilation. (Win et al., 2006).

<sup>=</sup>

segments in the lobe to be resected / number of segments in the lung)

lobectomy with the following formula (Wernly et al., 1980):

months after the surgery.

formula:

It is difficult to establish a definitive cut-off of ppo-FEV1 or ppo-DLCO above which resection of lung parenchyma will be safe. Some authors have estimated 0.8 liters as the limit below which it is unreasonable to perform the resection of the pulmonary parenchyma (Olsen et al., 1974). As an absolute value it can lead to errors, which is why it is better to use the percentage with respect to the theoretical value.

Several studies have shown that in candidates for lung resection, when ppo-FEV1 is greater than 40%, postoperative mortality is reduced (Markos et al., 1989), but other authors did not observe its increase when ppo-FEV1 is less than 40% (Morice et al., 1992). In relation to the ppo-DLCO it has also been noticed that the risk of postoperative complications is greater when the ppo-DLCO is less than 40% (Markos et al., 1989), and even one study estimates that this parameter is the best assessment of mortality and postoperative complications (Ferguson et al., 2008).

In practice, the scintigraphy has not been widely used in the functional assessment of patients about to undergo a lobectomy because of the difficulty in interpreting the individual contribution of each of the lobes to the whole of ventilation and perfusion. This could explain why several researchers consider that the simple calculation of the lung segments can predict the ppo-FEV1 as accurately as the ventilation perfusion scintigraphy does (Win et al., 2004). The ventilation scintigraphy has been widely used to predict postoperative lung function in patients with lung cancer who are scheduled for pneumonectomy (Colice et al., 2007).

The correlation between current and predicted ppo-FEV1 using the ventilation/perfusion scintigraphy has been variable with r between 0.67 and 0.9 (Win et al., 2006a). Both the ventilation and perfusion scintigraphies offer a good prediction of postoperative lung function individually, but it seems that there is no additional benefit in the performance of both (Win et al., 2006). However, the interpretation of the results should take into account that these techniques may underestimate the actual postoperative value (Zeiher et al., 1995).

#### **3.5 Exercise test**

During the exercise the patient is subjected to physical stress so that the whole system that regulates the uptake, transport and use of oxygen can be studied through the exercise test. When the latter is started, the lung increases the ventilation, oxygen uptake (VO2), CO2 production and blood flow similar to that which occurs during the postoperative period following the lung resection.

Among all the variables mentioned above, the most important is the peak oxygen uptake (VO2 peak), which gives us an idea of the global response to the effort and is defined as the maximum amount of oxygen a subject can capture, transport and use during the exercise. In addition, during the preoperative evaluation process the VO2 peak is the parameter that estimates the probability of complications best of all. Despite this, the exercise test should be performed only in selected cases (decrease in FEV1 and/or in DLCO below 80%) (Wayser et al., 1999).

#### **3.5.1 Low-technology exercise; stair climbing, shuttle walk, and 6-min walk tests**

Six-minute walk, stair climbing and shuttle walk tests have proved to be useful for preoperative risk stratification. In this sense, the 6-min walk test has a high reliability in the estimation of VO2 peak in healthy subjects and patients with COPD or those who are about to undergo lung transplantation and, therefore, in assessing the postoperative risk after thoracic surgery (Brunelli et al, 2009).

Perioperative Pulmonary Functional Assessment 381

The reliability of the exercise test with incremental protocol has been confirmed by numerous studies. In 1982 it was already proved that the complication rate decreased in patients with VO2 peak more than 1 liter (Eugene et al., 1982). In 1984 it was observed that the rate of postoperative complications was 100% when the VO2 peak was less than 15 mL/kg/min, but if this parameter was greater than 20 mL/kg/min, the risk of

In 1992 it was found that among the patients with preoperative FEV1 less than or equal to 40%, ppo-FEV1 less than or equal to 33% or PaCO2 more than or equal to 45 mmHg, those who did not undergo a exercise test and had a VO2 peak above 15 ml/kg/min were considered

In 1995 with a larger group of patients, it was already found that the VO2 peak, expressed as a percentage of predicted, estimated better postoperative complications, and that the patients with a VO2 peak more than 75% had 10% probability of complications. In contrast, in patients with VO2 peak less than 43% this probability increased to 90%, using as the cutoff point the VO2 peak of 60% (Bolliger et al. 1995a). At the same time, it was observed that patients with complications had a VO2 peak lower than 62.8% and if postoperative VO2 peak (ppo-VO2 peak) was less than 10 mL/kg/min, the risk of complications was very high

Recently it has been noticed that patients with complications have a VO2 peak of 15 mL/kg/min, while those without complications, have a VO2 peak of 19.2 mL/kg/min (Wang et al., 1999). Therefore, we can say that patients with a VO2 peak less than 10 mL/kg/min are not candidates for lung resection surgery. On the contrary, they are candidates if the VO2 peak is more than 15 mL/kg/min. Furthermore, in connection with the completion of pneumonectomy, VO2 peak values above 20 mL/kg/min or 75% of predicted value indicate a low risk of postoperative complications, while values below 10

Trying to get a better tolerance for exercise testing, especially in patients with dyspnoea who were not able to reach their VO2 peak, the submaximal protocol was proposed. In it the

After studying the exercise test with submaximal protocol in candidates for lung resection surgery, it has been observed that the VO2 reached allowed to predict the risk of postoperative complications (Miyoshi et al., 1989). However, this type of protocol usually requires invasive techniques which are not tolerated so well, therefore, this type of protocol

The current recommendations of the ERS / ESTS Task Force is that the cardiopulmonary exercise test is sure, reproducible and should be performed in a controlled environment. In addition, the VO2 peak measured during the test with incremental protocol should be considered as the most important parameter to assess, as a measure of exercise capacity and as a good predictor of postoperative complications after thoracic surgery. Finally, to perform pneumonectomy the value of 75% of predicted or more than 20 mL/kg/min should be considered as cutoff point. The risk of postoperative complications is high if the VO2 peak is less than 35% of predicted or less than 10 mL/kg/min for any resection. Instead, there is insufficient evidence to recommend cutoff points for lobectomy (Brunelli et al., 2009).

Thoracic computed tomography (CT) has efficacy comparable to that of perfusion scintigraphy in the calculation of ppo-FEV1 (Wu et al., 2002). In one study that compared

mL/kg/ min or 40% of predicted indicate a high risk (Bolliger et al., 1995b).

patient performs a pre-defined level of work (ATS, 2003).

is usually replaced by the incremental one.

suitable for lung resection with less postoperative complications (Morice et al., 1992).

complications was 10% (Smith et al., 1984).

(Bolliger et al., 1995b).

**3.6 Other tests** 

The shuttle walk test appears more reproducible and highly correlated with VO2 peak, estimating that 25 routes in this test are equivalent to a VO2 peak of 10 mL/kg/min (Singh et al, 1994). This cutoff point has been included in the algorithm proposed by the British Thoracic Society (BTS, 2001). However, no statistically significant differences have been found in the shuttle walk test among patients with and without complications after lung resection (Win et al., 2006b). This test tends to overestimate the exercise capacity in its range of lower values compared to VO2 peak, concluding that it should not be used alone to exclude patients from surgery (BTS, 2001). It has also been observed that patients who walk more than 400 meters in the shuttle walk test have a VO2 peak higher than 15 mL/kg/min (BTS, 2001).

The effectiveness of stair climbing test to predict serious cardiopulmonary complications following the lung resection surgery has already been demonstrated (Olsen et al., 1991). Against this background, the patients who climb less than 12 meters have a 2-fold higher rate of complications and mortality 23 times higher when compared with those who climb more than 22 meters, with a mortality rate of less than 1% (Brunelli et al., 2008). It has also been noticed that in patients with ppo-FEV1 or ppo-DLCO less than 40%, who climed more than 22 meters, the mortality rate is nonexistent (Brunelli et al., 2008).

Oximetry during the exercise has been proposed as a useful test in the preoperative assessment of candidates for lung resection (Colice et al., 2007). The role of oxygen desaturation during the exercise in postoperative risk stratification has not been defined in relation to early complications after the resection. In addition, it has been seen that oxygen desaturation during the exercise is a good predictor of postoperative respiratory failure, need for admission to an Intensive Care Unit (ICU), prolonged hospital stays and home treatment with oxygen (Ninan et al., 1997). On the other hand, oxygen saturation below 90% during the exercise test with incremental protocol is not a good predictor of postoperative cardiopulmonary morbidity (Varela et al., 2001).

#### **3.5.2 High-technology exercise; cardiopulmonary exercise testing**

There are 2 types of exercise protocol that have been used to evaluate the surgical risk: incremental or submaximal. They are usually carried out on a bicycle or a treadmill. The incremental protocol is the most used and consists in increasing the work to be performed by each patient to the limit of his tolerance. The exercise ends when the symptoms do not allow the patient to continue performing the exercise or when the registered variables do not permit to continue the test (ATS, 2003) (table 6).

Table 6. Indications for exercise terminations. ECG: electrocardiogram. SpO2: arterial oxygen saturation. (ATS, 2003).

The shuttle walk test appears more reproducible and highly correlated with VO2 peak, estimating that 25 routes in this test are equivalent to a VO2 peak of 10 mL/kg/min (Singh et al, 1994). This cutoff point has been included in the algorithm proposed by the British Thoracic Society (BTS, 2001). However, no statistically significant differences have been found in the shuttle walk test among patients with and without complications after lung resection (Win et al., 2006b). This test tends to overestimate the exercise capacity in its range of lower values compared to VO2 peak, concluding that it should not be used alone to exclude patients from surgery (BTS, 2001). It has also been observed that patients who walk more than 400 meters in the shuttle walk test have a VO2 peak higher than 15 mL/kg/min

The effectiveness of stair climbing test to predict serious cardiopulmonary complications following the lung resection surgery has already been demonstrated (Olsen et al., 1991). Against this background, the patients who climb less than 12 meters have a 2-fold higher rate of complications and mortality 23 times higher when compared with those who climb more than 22 meters, with a mortality rate of less than 1% (Brunelli et al., 2008). It has also been noticed that in patients with ppo-FEV1 or ppo-DLCO less than 40%, who climed more

Oximetry during the exercise has been proposed as a useful test in the preoperative assessment of candidates for lung resection (Colice et al., 2007). The role of oxygen desaturation during the exercise in postoperative risk stratification has not been defined in relation to early complications after the resection. In addition, it has been seen that oxygen desaturation during the exercise is a good predictor of postoperative respiratory failure, need for admission to an Intensive Care Unit (ICU), prolonged hospital stays and home treatment with oxygen (Ninan et al., 1997). On the other hand, oxygen saturation below 90% during the exercise test with incremental protocol is not a good predictor of postoperative

There are 2 types of exercise protocol that have been used to evaluate the surgical risk: incremental or submaximal. They are usually carried out on a bicycle or a treadmill. The incremental protocol is the most used and consists in increasing the work to be performed by each patient to the limit of his tolerance. The exercise ends when the symptoms do not allow the patient to continue performing the exercise or when the registered variables do

Table 6. Indications for exercise terminations. ECG: electrocardiogram. SpO2: arterial

than 22 meters, the mortality rate is nonexistent (Brunelli et al., 2008).

**3.5.2 High-technology exercise; cardiopulmonary exercise testing** 

cardiopulmonary morbidity (Varela et al., 2001).

not permit to continue the test (ATS, 2003) (table 6).

oxygen saturation. (ATS, 2003).

(BTS, 2001).

The reliability of the exercise test with incremental protocol has been confirmed by numerous studies. In 1982 it was already proved that the complication rate decreased in patients with VO2 peak more than 1 liter (Eugene et al., 1982). In 1984 it was observed that the rate of postoperative complications was 100% when the VO2 peak was less than 15 mL/kg/min, but if this parameter was greater than 20 mL/kg/min, the risk of complications was 10% (Smith et al., 1984).

In 1992 it was found that among the patients with preoperative FEV1 less than or equal to 40%, ppo-FEV1 less than or equal to 33% or PaCO2 more than or equal to 45 mmHg, those who did not undergo a exercise test and had a VO2 peak above 15 ml/kg/min were considered suitable for lung resection with less postoperative complications (Morice et al., 1992).

In 1995 with a larger group of patients, it was already found that the VO2 peak, expressed as a percentage of predicted, estimated better postoperative complications, and that the patients with a VO2 peak more than 75% had 10% probability of complications. In contrast, in patients with VO2 peak less than 43% this probability increased to 90%, using as the cutoff point the VO2 peak of 60% (Bolliger et al. 1995a). At the same time, it was observed that patients with complications had a VO2 peak lower than 62.8% and if postoperative VO2 peak (ppo-VO2 peak) was less than 10 mL/kg/min, the risk of complications was very high (Bolliger et al., 1995b).

Recently it has been noticed that patients with complications have a VO2 peak of 15 mL/kg/min, while those without complications, have a VO2 peak of 19.2 mL/kg/min (Wang et al., 1999). Therefore, we can say that patients with a VO2 peak less than 10 mL/kg/min are not candidates for lung resection surgery. On the contrary, they are candidates if the VO2 peak is more than 15 mL/kg/min. Furthermore, in connection with the completion of pneumonectomy, VO2 peak values above 20 mL/kg/min or 75% of predicted value indicate a low risk of postoperative complications, while values below 10 mL/kg/ min or 40% of predicted indicate a high risk (Bolliger et al., 1995b).

Trying to get a better tolerance for exercise testing, especially in patients with dyspnoea who were not able to reach their VO2 peak, the submaximal protocol was proposed. In it the patient performs a pre-defined level of work (ATS, 2003).

After studying the exercise test with submaximal protocol in candidates for lung resection surgery, it has been observed that the VO2 reached allowed to predict the risk of postoperative complications (Miyoshi et al., 1989). However, this type of protocol usually requires invasive techniques which are not tolerated so well, therefore, this type of protocol is usually replaced by the incremental one.

The current recommendations of the ERS / ESTS Task Force is that the cardiopulmonary exercise test is sure, reproducible and should be performed in a controlled environment. In addition, the VO2 peak measured during the test with incremental protocol should be considered as the most important parameter to assess, as a measure of exercise capacity and as a good predictor of postoperative complications after thoracic surgery. Finally, to perform pneumonectomy the value of 75% of predicted or more than 20 mL/kg/min should be considered as cutoff point. The risk of postoperative complications is high if the VO2 peak is less than 35% of predicted or less than 10 mL/kg/min for any resection. Instead, there is insufficient evidence to recommend cutoff points for lobectomy (Brunelli et al., 2009).

#### **3.6 Other tests**

Thoracic computed tomography (CT) has efficacy comparable to that of perfusion scintigraphy in the calculation of ppo-FEV1 (Wu et al., 2002). In one study that compared

Perioperative Pulmonary Functional Assessment 383

The use of algorithms in the evaluation of lung function in patients scheduled for thoracic surgery has as the main objective the step standardization of a series of diagnostic tests. These procedures avoid unnecessary costs, save time and allow you to gain experience in a more regulated way. This rationalization process contributes to improved patients care and

Although several algorithms have been proposed to assess respiratory function in patients undergoing thoracic surgery, there are few validations of them. In addition, they depend on the patients population being served and the technical possibilities of each hospital or center

One of the most widely accepted algorithms was proposed by Bolliger et al. and performed in 80 patients scheduled for resection of lung parenchyma (Bolliger et al. 1995a). This algorithm was validated later by Wyser et al. in 137 patients (figure 1), demonstrating a low

Fig. 4. Algorithm for assessment of cardiopulmonary reserve before lung resection in lung cancer patients. FEV1: Forced expiratory volume in 1 s. DLCO: Diffusion capacity of the lung for carbon monoxide. ppo: postoperative. VO2: Oxygen uptake. (Brunelli et al., 2009)

**4. Algorithms in the preoperative functional assessment** 

where they are performed (Juliá Serdá et al., 2010).

decreased postoperative morbidity and mortality (Juliá Serdá et al., 2010).

postoperative complication rate (11%) and mortality (1.5%) (Wyser et al., 1999).

the usefulness of thoracic CT (figure 3), single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) in patients with bronchogenic carcinoma who are candidates for lung resection, MRI proved to be more accurate than the other two techniques in the measurement of ppo-FEV1 (Ohno et al., 2007).

Fig. 3. Quantitative CT scan shows functional lung (*red*), pulmonary emphysema (*black*), and lung cancer (*white*). (Ohno et al., 2007).

The anatomical method is the calculation of postoperative lung function with the help of a formula that uses the preoperative FEV1 or FVC and the number of segments planned for resection (Zeiher et al., 1995). In case of lobectomy this formula estimates accurately the FEV1 postoperative and FCV which is not true in the case of pneumonectomy. That is why the latter is considered as inaccurate anatomical method.

The studies of pulmonary hemodynamics have also been used in the reseach of respiratory function in lung resection candidates. Perioperative risk is estimated by measuring the pulmonary arterial pressure and PaO2 during temporary occlusion of the pulmonary artery. This technique simulates the "physiological pneumonectomy" and is performed both at rest and during the exercise. It has been observed that growth in pressure in the pulmonary artery during the occlusion period increases the postoperative risk and complications (Gass & Olsen 1986). In addition, it has been observed that if the pulmonary arterial pressure is higher than 35 mmHg and PaO2 less than 45 mmHg, the patient is inoperable (Olsen et al., 1975). Another hemodynamic parameter used in the postoperative pulmonary assessment is the measurement of pulmonary vascular resistence (Schuurmans et al., 2002).

The main drawbacks of the use of pulmonary hemodynamics are the complexity of these techniques and the fact that they are invasive. Currently and in practice pulmonary hemodynamics is rarely used in respirotary assessing of candidates for thoracic surgery because the noninvasive tests have proved to have equal or superior efficacy.

the usefulness of thoracic CT (figure 3), single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) in patients with bronchogenic carcinoma who are candidates for lung resection, MRI proved to be more accurate than the other two

Fig. 3. Quantitative CT scan shows functional lung (*red*), pulmonary emphysema (*black*), and

The anatomical method is the calculation of postoperative lung function with the help of a formula that uses the preoperative FEV1 or FVC and the number of segments planned for resection (Zeiher et al., 1995). In case of lobectomy this formula estimates accurately the FEV1 postoperative and FCV which is not true in the case of pneumonectomy. That is why

The studies of pulmonary hemodynamics have also been used in the reseach of respiratory function in lung resection candidates. Perioperative risk is estimated by measuring the pulmonary arterial pressure and PaO2 during temporary occlusion of the pulmonary artery. This technique simulates the "physiological pneumonectomy" and is performed both at rest and during the exercise. It has been observed that growth in pressure in the pulmonary artery during the occlusion period increases the postoperative risk and complications (Gass & Olsen 1986). In addition, it has been observed that if the pulmonary arterial pressure is higher than 35 mmHg and PaO2 less than 45 mmHg, the patient is inoperable (Olsen et al., 1975). Another hemodynamic parameter used in the postoperative pulmonary assessment is

The main drawbacks of the use of pulmonary hemodynamics are the complexity of these techniques and the fact that they are invasive. Currently and in practice pulmonary hemodynamics is rarely used in respirotary assessing of candidates for thoracic surgery

the measurement of pulmonary vascular resistence (Schuurmans et al., 2002).

because the noninvasive tests have proved to have equal or superior efficacy.

techniques in the measurement of ppo-FEV1 (Ohno et al., 2007).

lung cancer (*white*). (Ohno et al., 2007).

the latter is considered as inaccurate anatomical method.
