The Science Journal of the American Association for Respiratory Care
Flow volume Loop provides invaluable information on the lung function characteristics. The understanding of genesis of the flow-volume loop allows uncovering many disorders of inspiratory and expiratory phases of the breathing cycle. In current practice flow-volume loop is obtained as a part of the routine spirometry. Many office spirometers are equipped with this application. When performed in erect and supine positions Flow-volume loop can reveal underlying variable airway obstruction. The authors present one case of symptomatic postural airway obstruction to illustrate this point.
A 46-year-old African American woman presented with dyspnea upon lying down and exertion. The physical examination revealed a mass in the neck consistent with enlarged thyroid. A flow-volume loop obtained in sitting position was normal. However, when the study was repeated in supine position the flattening of the inspiratory limb of the Flow-volume loop became obvious indicating the variable extrathoracic obstruction. The patient underwent total thyroidectomy. Her symptoms resolved postoperatively. Later, a repeat study of Flow-volume loop was normal both in erect and supine positions.