F. Pulmonary Function Testing and Evaluation for Lung Resectability. Goals in performing pulmonary function tests in a patient scheduled for lung resection include (1) identification of the patient at risk of increased postoperative morbidity and mortality, (2) identification of the patient who will need short- or long-term postoperative ventilatory support, and (3) evaluation of the beneficial effect and reversibility of airway obstruction with the use of bronchodilators.

G. Spirometry. A patient with an abnormal vital capacity has a 33% likelihood of complications and a 10% risk of postoperative mortality.

1. In the past, a forced expiratory volume in 1 second (FEV₁) of <800 mL in a 70-kg man had been considered an absolute contraindication to lung resection. However, with the advent of thoracoscopic surgery and improved postoperative pain management, patients with smaller lung volumes are now successfully undergoing surgery.

2. The ratio of FEV₁ to forced vital capacity (FVC) is useful in differentiating between restrictive (normal ratio) and obstructive pulmonary disease (ratio low).

3. A ratio of residual volume to total lung capacity of >50% is generally indicative of a high-risk patient for pulmonary resection.

H. Flow-volume loops display essentially the same information as a spirometer but are more convenient for measurement of specific flow rates (Fig. 37-2).

1. Patients with obstructive airways disease (asthma, bronchitis, emphysema) typically have grossly decreased FEV₁/FVC ratios.

2. Patients with restrictive disease such as (pulmonary fibrosis, scoliosis) typically have decreased FVC with a relatively normal FEV₁.

I. Significance of Bronchodilator Therapy. Pulmonary function tests are usually performed before and after bronchodilator therapy to assess the reversibility of the airways obstruction. A 15% improvement in pulmonary function tests may be considered a positive response to bronchodilator therapy and indicates that this therapy should be initiated before surgery.

J. Split-lung Function Tests. Regional lung function studies serve to predict the function of the lung tissue that would remain after lung resection. A whole (two)-lung test may fail to estimate whether the amount of postresection lung tissue will allow the patient to function at a reasonable level of activity without disabling dyspnea or cor pulmonale.

K. Computed Tomography and Positron Emission Tomography Scans

1. The CT scan can delineate the size of the tumor and reveal if there is airway or cardiovascular compression.

2. Positron emission tomography (PET) may be more accurate than CT for mediastinal staging and can be used to further evaluate lesions that are seen on a CT scan.

L. Diffusing Capacity for Carbon Monoxide

1. The ability of the lung to perform gas exchange is reflected by the diffusing capacity for carbon monoxide. (A predicted postoperative diffusing capacity for carbon monoxide <40% is associated with increased risk.)

2. Predicted postoperative diffusing capacity percent is the strongest single predictor of risk of complications and mortality after lung resection.

M. Maximal oxygen consumption (VO2 max) is a predictor of postoperative complications (<10 mL/kg/min indicates very high risk for lung resection). The preoperative evaluation of the patient for lung resection is summarized in Figure 37-1.

II. PREOPERATIVE PREPARATION. The wide spectrum of physiologic changes that occur during thoracic surgery puts patients at great risk of developing postoperative complications (Table 37-3).

III. INTRAOPERATIVE MONITORING (Table 37-4)

A. Pulse oximetry is especially valuable during thoracic surgery because hypoxemia may occur during one-lung ventilation (OLV).

B. Dysrhythmias occur commonly both during and after thoracic surgery, making the usual need for continuous ECG monitoring even more important.

IV. ONE-LUNG VENTILATION

A. Indications for OLV may be categorized as absolute and relative (Table 37-5).

B. Methods of Lung Separation

1. Double-lumen endobronchial tubes are the most widely used means of achieving lung separation and OLV. Lung separation is achieved by inflation of two cuffs (a proximal tracheal cuff and a distal bronchial cuff located in the main stem).

2. Because the left main bronchus is considerably longer than the right bronchus, there is a narrow margin of safety on the right main bronchus, with potentially a greater risk of upper lobe obstruction whenever a right-sided double-lumen tube (DLT) is used. A left-sided DLT is preferred for both right- and left-sided procedures.

3. Tracheal and bronchial dimensions can be also directly measured from the chest radiograph or chest CT scan. (Correlation between patient height and airway size is poor.) Typically, most women will need a 37-Fr DLT, and most men will be adequately managed with a 39-Fr DLT.

4. The common practice of fiberoptic bronchoscopy has lessened the risk of undetected distal placement or migration of the bronchial tip. The depth required for insertion of the DLT correlates with the height of the patient. For any adult 170 to 180 cm tall, the average depth for a left-sided DLT is 29 cm. For every 10-cm increase or decrease in height, the DLT is advanced or withdrawn 1 cm.

C. Placement of Double-Lumen Tubes

1. The insertion of the tube is performed with the distal concave curvature facing anteriorly. After the tip of the tube is past the vocal cords, the stylet is removed, and the tube is rotated through 90 degrees. A left-sided tube is rotated 90 degrees to the left, and a right-sided tube is rotated to the right. Advancement of the tube ceases when moderate resistance to further passage is encountered, indicating that the tube tip has been firmly seated in the main stem bronchus (Fig. 37-3).

2. When the tube is believed to be in the proper position, a sequence of steps should be performed to check its location (Table 37-6).

3. Confirmation of placement using a fiberoptic bronchoscope is recommended (Table 37-7; Figs. 37-4 and 37-5).

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