*From the Departments of Respiratory Medicine (Ms. Wilson, and Drs. Widdowson, Swanney, Meyer, and Beckert) and Cardiothoracic Surgery (Mr. Singh), Christchurch Hospital, Christchurch, New Zealand.
Correspondence to: Kathryn L. Wilson, BSc (Hons), Respiratory Scientist, Respiratory Physiology Laboratory, Department of Respiratory Medicine, Christchurch Hospital, Private Bag 4710, Christchurch 8140, New Zealand; e-mail: firstname.lastname@example.org
A 46-year-old woman presented with a 2-year history of exertional dyspnoea and wheeze accompanied by chest tightness and fatigue. These symptoms had progressively worsened over the preceeding 4 to 6 months. She had no significant cough, hemoptysis, or chest pain, and there was no diurnal variation to her symptoms. The patient was a nonsmoker, had no history of asthma or atopy, had no significant family history, and did not take any regular medication.
On examination, the patient looked well, weighing 60 kg with a measured height of 158 cm (body mass index, 24 kg/m2). She was afebrile, her pulse was 72 beats/min and regular, and her BP was 128/84 mm Hg. Her trachea was central with no evidence of tug, and no cervical lymphadenopathy was detected. She had mild audible inspiratory and expiratory noise, but no definite stridor. The chest examination was suggestive of a mild reduction in expansion of the left hemithorax compared to the right, but was normally resonant to percussion. Her breath sounds were vesicular throughout both lung fields with the exception of somewhat harsh breath sounds in the left mid-zone and axilla. She had no evidence of wheeze or crepitations.
Pulmonary function testing revealed an obstructive pattern of moderate severity with no significant im-provement in FEV1 or FVC 15 min after bronchodilator (salbutamol, 5 mg) administration. Lung volume and diffusing capacity measurements were within the normal limits of the reference range. The flow-volume loop is shown in Figure 1
, top, and the pulmonary function results are shown in Table 1
. A chest radiograph taken at the time of presentation is shown in Figure 1, bottom. The accompanying radiologist’s report indicated that the chest radiograph findings were normal.
Examination of the flow-volume loop revealed the following unusual flow pattern: a biphasic flow pattern during expiration and a truncated flow pattern during inspiration (Fig 1, top). This finding, combined with the spirometric identification of airway obstruction, and normal lung volumes and diffusing capacity, suggested the presence of a fixed large airway obstruction.
The shape of the spirometric curve is the key finding highlighted in this case report. The biphasic expiratory curve, with an initial phase of rapid emptying followed by a slower phase of delayed emptying, is most commonly seen in patients with severe COPD who have undergone a single lung transplantation but can also be seen in patients with a tumor situated within a main bronchus. The biphasic expiratory flow pattern seen in patients who have undergone transplantation is a combination of flow patterns from the following two sources: the native “obstructed” lung; and the transplanted “normal” lung. Given that the patient in this case report had not undergone transplantation, a bronchial tumor obstructing a major airway was the most likely diagnosis.
The patient in this case report had a reduction in both expiratory and inspiratory flow. A reduction in both inspiratory and expiratory flow is suggestive of a fixed obstruction, regardless of whether the site (or origin) of the obstruction is intrathoracic or extrathoracic. Inspection of the shape of the flow-volume loop in patients with obstructive airways disease provides useful clues toward the identification of abnormalities such as the fixed obstruction seen in this case report.
CT scanning revealed a discrete, almost spherical, endobronchial lesion within the left main bronchus (Fig 2
, top left). Retrospective examination of the chest radiograph indicated that the endobronchial lesion could be identified on the chest radiograph (Fig 2, top right). The lesion was missed in the initial radiologist’s report because it was faint and therefore difficult to detect. Fiberoptic bronchoscopy performed on the same day confirmed the presence of a highly vascular, endobronchial lesion, which measured 13 × 11 mm, was located 165 mm from the carina, and almost completely occluded the lumen of the left main bronchus. Biopsy was not performed due to the vascular nature of the lesion and the likelihood of hemorrhage.
The patient presented with a 2-year history of shortness of breath and wheeze, which had significantly worsened over the last 4 to 6 months. These symptoms, accompanied by obstructive spirometry and a normal chest radiograph findings raised the possibility of asthma. However, there was no reversibility after bronchodilator administration, and there was an absence of past respiratory disease or other associated symptomatology to suggest an atopic process. Reversibility is a characteristic feature of asthma; thus, a significant improvement in FEV1 following the administration of a bronchodilator is considered to be a strong indicator of this diagnosis. The absence of reversibility seen in this patient’s spirometry finding, therefore, gives less weight to a diagnosis of asthma.
The patient in this case report had moderate airflow obstruction on spirometry. Airflow obstruction is most commonly seen in smokers and asthmatic patients. The absence of a history of smoking ruled out smoking-related disease, and several of the following features argued against asthma as the cause of her symptoms: no associated symptomatology to suggest an atopic disease; no personal or family history of asthma; a nonreversible obstructive pattern; an expiratory biphasic curve; and a reduction in both expiratory and inspiratory air flow.
The patient was referred to a cardiothoracic surgeon, who performed a sleeve resection of the left main bronchus. The lesion was completely removed, with preservation of the left lung, and a subsequent pathologic examination confirmed it to be a typical carcinoid tumor, arising from the submucosa of the left main bronchus. Spirometry was repeated 7 months after surgery, showing complete resolution of the patient’s obstructive flow pattern (Fig 2, bottom right, Table 2
Bronchial carcinoid tumors are uncommon, accounting for approximately 5% of all primary lung tumors. Patients with bronchial carcinoid tumors may be asymptomatic, present with hemoptysis, or have evidence of bronchial obstruction. The overall incidence for bronchial carcinoid is three to five tumors per million people per year, although it has been reported that there is a slightly higher incidence in women. Thus, bronchial carcinoid tumor is a diagnosis that is not often suspected.
This case highlights the importance of examining the shape of the flow-volume loop, as well as the numerical data, when interpreting spirometry. Diagnosis of a fixed large airway obstruction can be missed if the shape of the flow-volume loop is ignored or is unavailable.
Spirometry, including expiratory and inspiratory flow-volume loops, should be performed in all patients presenting with dyspnea.
Inspection of the flow-volume loop, in conjunction with the numerical data, is important for the interpretation of results.
While the most common causes of airflow obstruction are COPD and asthma, less common causes, such as localized endobronchial obstruction, should be considered in the appropriate clinical setting.
The biphasic expiratory curve, with an initial phase of rapid emptying followed by a slower phase of delayed emptying, is most commonly seen in patients with severe COPD following single lung transplantation but can also occur with a mainstem bronchial tumor.
Bronchial carcinoid tumor is a potentially curable tumor if detected and treated early.
FEF25–75% = forced expiratory flow, midexpiratory phase; Dlco = diffusing capacity of the lung for carbon monoxide; TLC = total lung capacity.
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