Tension ball valve mucus plug in asthma

Lung Hyperlucency: A Clinical-Radiologic Algorithmic Approach to Diagnosis

Areas of diminished lung density are frequently identified both on routine chest radiographs and chest CT examinations. Colloquially referred to as hyperlucent foci of lung, a broad range of underlying pathophysiologic mechanisms and differential diagnoses account for these changes. Despite this, the spectrum of etiologies can be categorized into underlying parenchymal, airway, and vascular-related entities. The purpose of this review is to provide a practical diagnostic algorithmic approach to pulmonary hyperlucencies incorporating clinical history and characteristic imaging patterns to narrow the differential.

Fatal bronchial asthma with bilateral lung collapse

Fatal bronchial asthma is classically characterized in pathology textbooks and journal articles as associated with lung hyperinflation at autopsy. The following is a report of a case of fatal bronchial asthma associated instead with bilateral lung collapse. This manifestation of asthma at autopsy has not been previously reported, to my knowledge. A 31-year-old man with a history of recurrent asthma was found in an unresponsive state in his automobile after a low-speed collision. Medical personnel during the resuscitation noted a decrease in breath sounds bilaterally and some wheezing. There was no escaping air with needle thoracostomies at the outset. Cardiac monitoring demonstrated pulseless electrical activity during most of the 30-minute resuscitation attempt. An autopsy disclosed collapsed lungs bilaterally. Microscopic examination of the lungs disclosed the characteristic histopathologic features of bronchial asthma.

Pressure-flow signatures of central-airway mucus plugging

SETTING

Medical Intensive Care Unit of Regions Hospital, a University of Minnesota-affiliated teaching hospital.

PATIENT

Mechanically ventilated woman with status asthmaticus and acute respiratory failure.

INTERVENTION

Observations of airway pressure and flow tracings before and after bronchoscopic inspection and airway lavage.

MAIN RESULTS

Four newly observed signs were recorded that may serve to identify occult central airway mucus plugging in the ventilated asthmatic patient.

Mucus plugging as a cause of acute lobar overdistension

Acute lobar overdistension in children is usually indicative of foreign body aspiration, especially when a history of a choking episode is recalled. An unusual presentation of asthma as recurrent overdistension of the left lung in a toddler is described. The child had undergone two consecutive negative bronchoscopies with a presumptive diagnosis of foreign body aspiration; however, it was only the antiasthmatic treatment that resulted in an excellent outcome.

Can capnography detect bronchial flap-valve expiratory obstruction?

OBJECTIVE

We have previously shown in a mechanical lung model [1] that bronchial flap-valve expiratory obstruction results in sequential lung expiration, best detected by prolonged and low magnitude tracheal expired flow (V) from the obstructed lung. However, the normal expiratory resistance of clinical ventilation circuits might also generate prolonged, low value exhaled V, that could be confused with bronchial flap-valve obstruction. We reasoned that bronchial flap-valve obstruction would also cause sequential CO2 unloading from each lung and result in a biphasic tracheal capnogram.

METHODS

To test this hypothesis, we ventilated (VT, 650 ml; f, 10 br/min) a dual mechanical test lung, with each side connected to a separate alcohol-burning chamber. An airway adapter-monitor system measured airway V, P, PCO2, and FO2. The circumference of the diaphragm in a respiratory one-way valve was trimmed to generate unidirectional resistance to expiratory V. Measurement sequences were repeated after this flap-valve was interposed in the left "main-stem bronchus."

RESULTS AND DISCUSSION

During moderate or severe left bronchial flap-valve obstruction, left bronchial V was delayed so that the left lung anatomical dead space (devoid of CO2) mixed with normal right exhalate to depress the expiratory upstroke or early plateau of the tracheal capnogram. During severe obstruction, decreased perfusion of the left lung caused lower alveolar PCO2. Then, prolonged low V from the left bronchus also resulted in depression of the end of the tracheal alveolar plateau. In general, the low magnitude of bronchial V from the obstructed lung limited its effect on the tracheal capnogram and the best marker of sequential lung emptying during bronchial flap-valve obstruction may be late exhaled V without reduction in total tidal volume.

Exhaled flow monitoring can detect bronchial flap-valve obstruction in a mechanical lung model

Flap-valve obstruction to expiratory flow (V) in a major bronchus can result from inspissated secretions, blood, or foreign body. During inhalation, increasing airway caliber preserves inspired V past the obstruction; during exhalation, decreasing airway diameter causes airflow obstruction and even frank gas trapping. We reasoned that the resultant sequential, biphasic exhalation of the lungs would be best detected by measuring exhaled V versus time. Accordingly, we designed an airway obstruction element in a mechanical lung model to examine flap-valve bronchial obstruction. A mechanical lung simulator was ventilated with a pressure-limited flow generator, where f = 10/min, tidal volume = 850 mL, and respiratory compliance = 40 mL/cm H2O. Airway V (pneumotachometer) and pressure (P) were digitally sampled for 1 min. Then, the circumference of the diaphragm in a respiratory one-way valve was trimmed to generate unidirectional resistance to expiratory V. Measurement sequences were repeated after this flap-valve was interposed in the right "main-stem bronchus." Integration of airway V versus time generated changes in lung volume. During flap-valve obstruction of the right bronchus, the V-time plot revealed preservation of peak expired flow from the normal lung, followed by retarded and decreased flow from the obstructed right lung. Gas trapping of the obstructed lung occurred during conditions of decreased expiratory time and increased expiratory resistance. Airway P could not differentiate between bronchial and tracheal flap-valve obstruction because P decreased abruptly in both conditions. The flow-volume loop displayed less distinctive changes than the flow-time plot, in part because the flow-volume loop was data (flow) plotted against its time integral (volume), with loss of temporal data. In this mechanical lung model, we conclude that bronchial flap-valve obstruction was best detected by the flow-time plot, which could measure the sequential emptying of the lungs.

Unilateral hyperlucency with left lower lobe mass in a patient with bronchial asthma

Mucoepidermoid tumors are rare bronchial adenomas whose clinical presentation can mimic that of bronchial asthma. Bronchial adenoma should be included in the differential diagnosis of a patient with a persistent radiographic abnormality and clinical features of bronchial asthma. We present an adolescent female with a history suggestive of bronchial asthma and a persistent left lower lobe atelectasis, who later was found to have a low-grade mucoepidermoid tumor.

Transient unilateral hyperlucent lung due to mucus plugs

A 63-year-old patient with a tracheostomy presented with a transient unilateral hyperlucent lung and absent breath sounds over the left lower lobe. A tracheobronchial cast and an additional floating mucus plug in the left lower lobe bronchus were retrieved with fiberbronchoscopy. Subsequently normalisation of ventilation and radiological appearance of the left lung occurred.

Unilateral bronchospasm during pleurodesis in an asthmatic patient

A case of unilateral bronchospasm during pleurodesis in a patient with a history of recurrent pneumothorax and asthma is presented. The etiology of this event is not clear; however, it likely includes reflex parasympathetic bronchoconstriction due to physical stimulation of the pleural surface during pleurodesis. Treatment involved independent lung ventilation, corticosteroids, and aminophylline.