(Fig. 37-1: The order of tests to determine the cardiopulmonary status of the patient and the extent of lung resection that would be tolerated).
The preoperative evaluation of the patient for thoracic surgery should focus on the extent and severity of pulmonary disease and cardiovascular involvement. Thoracic surgery is known to be associated with high risk, and patient factors that have been associated with increased risk include advanced age, poor general health status, and chronic obstructive pulmonary disease (COPD).
- History (Table 37-1: Patient Medical History that Should be Obtained Before Thoracic Surgery)
- Physical Examination (Table 37-2: Physical Examination that Should be Performed Before Thoracic Surgery)
- Electrocardiogram A patient with COPD may present with electrocardiographic features of right atrial and ventricular hypertrophy and strain.
- Chest Radiography. Hyperinflation and increased vascular markings are usually present with COPD. Tracheal or carinal shift should be noted. Review of a computed tomography (CT) study often provides more information about tumor size and location than the chest radiograph.
- Arterial blood gases. A common finding in arterial blood gas analysis of patients with COPD is hypoventilation and CO2 retention.
- “Blue bloaters” (chronic bronchitis) are cyanotic, hypercarbic, hypoxemic, and usually overweight. These patients may hypoventilate when given high oxygen concentrations to breathe because of a decreased hypoxic drive.
- “Pink puffers” (patients with emphysema) are typically thin, dyspneic, and pink, with essentially normal arterial blood gas values. They present with an increase in minute ventilation to maintain their normal Paco
2, which explains the increase in work of breathing and dyspnea.
- 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.
- Spirometry. A patient with an abnormal vital capacity has a 33% likelihood of complications and a 10% risk of postoperative mortality.
- 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.
- The ratio of FEV1 to forced vital capacity (FVC) is useful in differentiating between restrictive (normal ratio) and obstructive pulmonary disease (ratio low).
- A ratio of residual volume to total lung capacity of >50% is generally indicative of a high-risk patient for pulmonary resection.
- Flow-volume loops display essentially the same information as a spirometer but are more convenient for measurement of specific flow rates (Fig. 37-2: Flow–volume loops relative to lung volumes in a normal subject in a patient with chronic obstructive pulmonary disease (COPD), a patient with fixed obstruction (tracheal stenosis), and a patient with pulmonary fibrosis (restrictive defect)).
- Patients with obstructive airways disease (asthma, bronchitis, emphysema) typically have grossly decreased FEV1/FVC ratios.
- Patients with restrictive disease such as (pulmonary fibrosis, scoliosis) typically have decreased FVC with a relatively normal FEV1.
- 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.
- 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.
- Computed Tomography and Positron Emission Tomography Scans
- The CT scan can delineate the size of the tumor and reveal if there is airway or cardiovascular compression.
- 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.
- Diffusing Capacity for Carbon Monoxide
- 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.)
- Predicted postoperative diffusing capacity percent is the strongest single predictor of risk of complications and mortality after lung resection.
- 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.