• SOM 4th Yr Curriculum

• CLERKSHIP INFORMATION
• Introduction / Goals and Objectives
• Rotations
  • HMC
  • UWMC
  • VAMC
• Seminars
• Faculty Only
• PULMONARY EDUCATION
• Pulmonary Med Library
• Arterial Blood Gases
• Cardiopulmonary Exercise Testing
• Mechanical Ventilation
• Pulmonary Function Testing
• Pleural Effusion
• Radiology

Pulmonary Function Testing

Case 4 Answer

A 25 year-old man presents to his physician with complaints of dyspnea and wheezing. He is a non-smoker. Two years ago, he was in a major motor vehicle accident and was hospitalized for 3 months. He had a tracheostomy placed because he remained on the ventilator for a total of 7 weeks. His tracheostomy was removed 2 months after his discharge from the hospital.

His pulmonary tests are as follows:

His flow volume loop is as follows:

This patient has evidence of airflow obstruction on spirometry as he has a low FEV₁ and a reduced FEV₁/FVC ratio of 0.54. Given that the FEV₁ is 69% of predicted this patient would be labeled as having “mild airflow obstruction.

In order to make a correct diagnosis in this patient, however, you cannot look simply at the numbers from his spirometry testing but must also look at the flow volume loops. A noteworthy feature of his flow volume loop is that there is flattening of both the inspiratory and expiratory limbs. This pattern is seen in patients who have a fixed upper airway obstruction. In a patient with a prior history of tracheostomy, you would be very suspicious that this patient has developed tracheal stenosis, a known long-term complication of tracheostomy tubes.

Other forms of airway obstruction will also demonstrate characteristic patterns on the flow-volume loops. Patients with a variable intrathoracic obstruction (eg. a carcinoid tumor in a mainstem bronchus) have flattening of the expiratory limb of the flow-volume loop while patients with variable extrathoracic obstruction (eg. a thyroid tumor) have flattening of the inspiratory limb of the flow-volume loop.

All three of these patterns are demonstrated in the figure below.

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