Pulmonary Diagnostic Procedures

Pulmonary Diagnostic Procedures

1. Pulmonary Function Testing
A. 100,000 thoracotomies are performed annually
B. Preoperative assessment of risk required
C.Resectability
1) The amount of lung tissue than can be safely removed without pulmonary insufficiency.
2) Depends on pulmonary reserve.
D. Operability
1) Ability of the patient to survive the procedure and perioperative complications.
2) Depends on Comorbid conditions

2. Pulmonary Function Testing
A. Pulmonary spirometric studies
B. Pulmonary hemodynamic response testing
C. Exercise testing

3. Spirometry
A. Modern spirometry is complex and sophisticated
B. Affected by height, age, weight, sex, race and posture
C. Blacks, Polynesians, Asians - lung volumes 10-12% less than similarly aged whites
D. Main stays of preoperative assessment are arterial oxygenation, spirometry, and diffusion capacity
E. Spirometry and arterial oxygen not predictive of postoperative complications

4. Diffusion Capacity
A. Is more sensitive as a predictor of postoperative complications
B. DLCO estimates pulmonary capillary surface area, hemoglobin content, alveolar micro architecture
C. DLCO is decreased in emphysema, pulmonary hypertension and interstitial lung disease
D. DLCO <60% was the best predictor of mortality 5. Ventilation/Perfusion Scans A. Useful in determination of postoperative lung function B. Perfusion scans (Tc99 ) are more predictable than ventilation scans (Xe133) C. Spirometry and lung scans accurately predict postoperative lung function D. A calculated postoperative FEV1 of less than 40% of predicted was associated with 50% mortality rate E. Absolute minimum postoperative FEV1 should be > 800 cc

6. Pulmonary Hemodynamics Response Testing
A. Not popular in North America
B. Pulmonary artery pressure and resistance determine survival
C. Pulmonary arterial pressure > 35 mmHg results in decreased survival (10 fold)
D. Pulmonary hypertension is a contraindication to lung resection
E. PVR > 190 dynes associated with 90% mortality
F. Unfortunately pulmonary function tests do not identify patients with high pulmonary vascular resistance

7. Exercise Testing
A. Minimal achievement tests
1) Submaximal effort, not standardized
B. Maximum exercise tests
1) Arterial desaturation with exercise
2) Maximal oxygen consumption (MVO2)
3) Blood lactate level during exercise

8. Guidelines for Patient Selections
A. FVC < 50% of predicted B. FEV1 < 50% of predicted C. FEV1 < 2.0 Liters D. DLCO < 60% of predicted E. PAP > 35 mm/Hg
F. PVR > 190 dynes
G. MVV < 50% of predicted (with good patient cooperation)

9. Summary
A. Postoperative lung function (based on spirometry and V/Q scans) can be predicted
B. In pneumonectomy patients the best predictor of death was calculated postoperative FEV1
C. In all patients the best predictor of death was calculated postoperative DLCO
D. Best predictor of overall complications was DLCO and predicted postoperative DLCO

EXTENDED OUTLINE

1. Pulmonary Lympatic Drainage
A. RUL - lower paratracheal higher paratracheal neck
B. RML - subcarinal right paratracheal
C. RLL - subcarinal right paratracheal
D. LUL - subaortic (Botallo's node) Anterior mediastinal or left paratracheal
E. LLL - subcarinal
clinical findings often do not correlate with anatomical predictions

2. Scalene Node Biopsy
A. Indicated with a palpable node
B. Staging ie. nonpalpable is more controversal
1) SNB vs. Mediastinoscopy
a) M&M the same
b) Yield: SNB - 10% positive, Mediastinoscopy- 30% positive
C. Technique
1) anatomical bonderies include:
2) inferiorly: subclavian vein
3) medially: internal jugular
4) posteriorly: anterior scalene

4. Mediastinoscopy
A. Positive node 30-35% of the time
B. Controversy
1) Do patients with suspected cancer who are otherwise operable need this procedure
2) What to with a positive node (N2 Disease)
C. Studies
1) Maassen
a) 1921 cases of Stage I & II
b) central masses - 23% positve nodes
c) peripheral masses - 19% positive
D. CT Scan
1) Negative predictive rate 80-97%
2) Positive predictive rate 44-82%
3) Dales: meta-analysis
a) false negative 20%
b) false positive 21%
4) Kerr: 15% of positive restricted nodes are less than 10mm
E. N2 Disease carries a 5 yr survival of 3% (Mountain et al 28%)
1) exceptions:
a) limited aortopulmonary nodes and no anterior mediastinal nodes
b) non-small cell with limited ipsilateral tracheobroncial intranodal involvement
F. Morbidity less than 0.1%
G. Technique

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1. Definition
Over 100,000 thoracotomies are performed annually in the United States alone, and preoperative assessment of risk is required. Two concepts are key to risk assessment: resectability, which is the amount of lung tissue than can be safely removed without pulmonary insufficiency, and operability, which is the ability of the patient to survive the procedure and any perioperative complications. Resectability depends on pulmonary reserve and operability depends on comorbid conditions. The main tests for preoperative assessment are arterial oxygenation, spirometry, and diffusion capacity.

2. Arterial Blood Gases
A. The gas partial pressure in liquid is equal to the barometric pressure times the fractional gas concentration
B. The solubility of oxygen and carbon dioxide in blood is affected by hemoglobin and buffers
C. Lower temperature, an increase in pH, and a fall in blood PCO2 will all shift the HbO2 dissocation curve to the left, increasing the affinity of hemoglobin for oxygen
D. Three points of the curve to remember:
PaO2 Saturation
100 (arterial) 97%
50 84%
40 (venous) 75%
E. CO2 is usually transported as HCO3-, but can combine with hemoglobin and carbonic anhydrase
F. Venous PCO2 is about 46; arterial and alveolar PCO2 is about 40
G. Normal alveolar-arterial (A-a) PO2 gradient is 10 in young adults and up to 20 in older adults
H. Calculate A-a gradient as follows: PAO2 = 150-PaCO2, then subtract the PaO2
I. Common causes of increased A-a gradient include hypoventilation, reduced inspired oxygen, right-to-left shunting, and V/Q mismatch from atelectasis or airway obstruction
J. A PaCO2 greater than 45 indicates a higher risk of morbidity and mortality, but hypoxemia is unreliable as a predictor of poor outcome

3. Spirometry
A. Modern spirometry is complex, sophisticated, and is affected by height, age, weight, sex, race and posture
B. Important values include VT, FEV1, FVC, and FEV1/FVC
C. In restrictive disease, the total lung capacity, vital capacity, and FEV1 are all reduced, but the FEV1/FVC is normal
D. In obstructive diseases like emphysema, the total lung capacity and vital capacity are increased, and the FEV1 and FEV1/FVC are reduced
E. Blacks, Polynesians, and Asians have lung volumes 10-12% less than similarly aged whites
F. An FEV1 less than 2.0 liters indicates a higher risk of morbidity and mortality

4. Diffusion Capacity
A. Is more sensitive than spirometry as a predictor of postoperative complications
B. DLCO estimates pulmonary capillary surface area, hemoglobin content, and alveolar microarchitecture
C. The test is particularly useful in patients with dyspnea and relatively normal spirometry
D. DLCO is decreased in emphysema, pulmonary hypertension and interstitial lung disease; it is increased in mitral stenosis, left-sided failure, and polycythemia
E. A DLCO less than 60% is a good predictor of mortality

5. Ventilation/Perfusion Scans
A. Blood flow (perfusion) is absent in pulmonary vascular obstruction and ventilation is absent in atelectasis
B. The perfusion portion (Tc99) is more predictable than the ventilation portion(Xe133)
C. When used together with spirometry, lung scans can accurately predict postoperative lung function

6. Pulmonary Hemodynamics Response Testing
A. Pulmonary artery pressure and resistance are determinants of survival
B. A pulmonary arterial pressure greater than 35 mmHg results in a 10-fold decreased survival
C. Pulmonary hypertension is a contraindication to lung resection
D. PVR greater than 190 dynes is associated with 90% mortality
E. Unfortunately, pulmonary function tests do not identify patients with high pulmonary vascular resistance

7. Exercise Testing
A. Maximal oxygen consumption (MVO2) may be useful in evaluating marginal patients
B. Elevated blood lactate level during exercise may help predict mortality, but is not useful for postoperative complications

8. Guidelines for Patient Selections
A. FVC Less than 50% of predicted
B. FEV1 Less than 50% of predicted
C. DLCO Less than 60% of predicted
D. MVV Less than 50% of predicted (with good patient cooperation)

9. Bronchoscopy
A. Indications
1) A wide range of diseases are indications for either diagnostic or therapeutic bronchoscopy, most commonly carcinoma, pulmonary infections, and interstitial lung disease
2) The surgeon must perform bronchoscopy prior to thoracotomy on any patient who may undergo pulmonary resection
3) Specific indications for the procedure include chronic, persistent cough; hemoptysis; localized wheezing; and bronchial obstruction
B. Diagnostic Bronchoscopy
1) An 8 x 40mm rigid bronchoscope is suitable for most adults
2) The flexible bronchoscope is useful for peripheral or upper lobe lesions, but is limited in the presence of thick secretions and excessive bleeding
3) Either topical or general anesthesia may be used depending on patient status and age
4) As the tip of the bronchoscope passes the larynx, the patient's head is lowered and extended
5) Use ball-tip or cup forceps for tissue sampling, and always biopsy proximal to a gross tumor to define the upper limit of the tumor
6) Flexible bronchoscopy allows for transbronchial needle biopsy, washings, and brushings
C. Therapeutic Bronchscopy
1) Most foreign bodies can be removed by bronchoscopy; grasping forceps or a Fogarty catheter are the most useful
2) Heavy retained secretions can usually be drained using flexible bronchoscopy with a large side port
3) Palliation resection of endobronchial obstructing tumors can be done with the Nd:YAG laser
4) Other treatments include brachytherapy and phototherapy
D. Specific Conditions
1) Bronchogenic carcinoma can present as an endobronchial mass, submucosal or peribronchial involvement, a peripheral mass, diffuse metastatic disease, or occult tumor
2) Masses and metastatic disease should be directly biopsied, while submucosal involvement and peripheral masses requires transbronchial needle biopsy, washings and brushings
3) Occult tumors are discovered from positive sputum cytology; a thorough bronchoscopic examination will find the majority of these lesions
4) Bronchoscopy is also useful for tuberculosis, fungal infections, and opportunistic infections in the immunocompromised patient