Ventilation Perfusion Scan Click for full image (63k).

Ventilation-Perfusion Lung Scan:

• to determine the likelihood of pulmonary emboli
• less common indications include:
  • evaluation of lung transplantation
  • preoperative evaluation
  • right-to-left shunt evaluation

Pulmonary Function Testing
Pulmonary function testing is performed most commonly to:

• Assist in a differential diagnosis
• Estimate prognosis
• Follow the course of a disease or its response to therapy.
• Estimate the risk or procedures or therapy.
• Detect untoward reactions to drugs.
• Assess functional impairment and/or disability.

• Evaluate respiratory symptoms, especially dyspnea, wheeze, stridor and persistent cough.
• Evaluate abnormal laboratory tests, such as hypoxemia, hypercapnia, polycythemia, etc.
• Diagnose an obstructive or restrictive ventilatory impairment, or any extrathoracic upper airway obstruction.
• Help assess peri-operative risk or exercise capacity.
• Monitor the course of chronic obstructive lung diseases, such as asthma and COPD.
• Monitor the course or chronic restrictive diseases, such as fibrosing alveolitis or a neuromuscular disorder.
• Evaluate the response to specific therapy for a respiratory condition.
• Help validate subjective complaints in occupational or environmental settings.

2) Carbon Monoxide Diffusing Capacity

• Establish the presence of parenchymal lung disease in patients with an obstructive ventilatory impairment ( e.g. differentiating asthma from underlying emphysema).
• Establish the presence of parenchymal lung disease in patients with a restrictive ventilatory impairment (e.g. differentiate intrinsic lung disease from an extrapulmonary process)
• Establish the presence parenchymal lung disease in patients with otherwise normal pulmonary function studies (e.g. asbestosis, fibrosing alveolitis, drug-induced or radiation pneumonitis, pheumoncystis pneumonia.)
• Help assess disease severity in patients with parenchymal or pulmonary vascular disease and to estimate functional impairment and/or disability.
• Help monitor patients with pulmonary haemorrhage syndromes.

3) Functional Residual Capacity

• Confirm a diagnosis suspected by spirometry.
• In a restrictive disease, diagnose a respiratory disorder not clearly evident from spirometry or to help assess disease severity.
• Help monitor the progression of parenchymal lung disease or assess its response to therapy.

4) Oximetry

• Estimate oxygen saturation in a patient at rest with or without supplemental oxygen therapy.
• Document changes in oxygen saturation with exercise, (usually in patients with SaO₂ > 90% at rest).
• Document improvement in oxygen saturation following change in therapy or in level of oxygen supplementation.

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