Hospital Vega Baja
Correspondence to: Eduardo Garcia-Pachon, MD, Department of Internal Medicine, Hospital Vega Baja, Orihuela-Alicante, E-03314 Spain
The visual inspection of the flow-volume loop can reveal the
presence of flow oscillations. Flow oscillations are defined as a
reproducible sequence of alternating decelerations and accelerations of
flow.1In a large retrospective survey2 of
2,800 flow-volume loops, the incidence of flow oscillations was of
1.4%. These oscillations can be due to a variety of causes, such as
obstructive sleep apnea syndrome, structural or functional disorders of
the larynx, or neuromuscular diseases,1 but
tracheobronchomalacia has not been mentioned.
A 58-year-old man with a diagnosis of COPD with chronic cough and
exertional dyspnea was referred to the Respiratory Medicine Division
because of a pulmonary nodule. The patient did not have symptoms of
sleep disorders or neuromuscular disease. At fiberoptic bronchoscopy,
the larynx was normal, but the trachea and main bronchus completely
collapsed even during quiet expiration. Thoracic CT revealed a 1.5-cm
nodule, and images obtained during expiration demonstrated the collapse
of the trachea. Spirometry showed FVC of 3.96 L (118% of reference
value) and FEV1 of 2.28 L (84%); the volume-time
curve did not have morphologic alterations, but the visual inspection
of the flow-volume loop revealed reproducible flow oscillations on the
The prevalence of tracheobronchomalacia is relatively low: 1% and
4.5% in two large series of bronchoscopies.3 The
principal symptom is chronic dyspnea, but attacks like those in asthma
are seldom seen, and response to bronchodilator treatment is
scanty.3 In patients with tracheobronchomalacia, a typical
notch (can be one or more) in the volume-time curve of the spirogram
has been reported3; this finding was not found in the
patient described here. The notch is considered to reflect a sudden
diminution of flow at the beginning of the expiration when the airway
collapses. Nevertheless, alterations on the flow-volume loop have not
The finding of flow oscillations on the flow-volume loop should
instigate extensive investigations primarily directed at the upper
airway and its surrounding musculature.1 In view of the
case described here, tracheobronchomalacia should be considered among
the possible causes of flow oscillations.
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