Tension pneumothorax?

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A two and a half week old male infant presents with a history of distressed noisy breathing for several hours, progressively worsening with periods of apnea and cyanosis. He had appeared well all day at the baby-sitter’s until one hour after his last feeding when he was found to have the symptoms of respiratory distress. He had no history of fever, URI symptoms, vomiting, or diarrhoea. No possible exposure to toxins or foreign bodies could be found.

Birth history was that of a full term, NSVD, 7lb. 8oz. born to a 23 y/o G3P2 mother without sepsis risk factors. He seemed to be doing well since discharge but had been noted by his parents to have “funny breathing” since birth. This was described as periodic rapid breathing with “deep caving” in of his anterior chest. It did not cause cyanosis, nor did it interfere with feeding. Weight gain since birth has been appropriate.

 

Exam Findings

T36.7, P160, R60, BP 100/70. Oxygen saturation 86% in room air.

He was alert and anxious, with obvious tachypnea and retractions. Skin color was intermittently dusky until oxygen was administered and then remained pink (oxygen saturation 96-100%). Head atraumatic. No signs of URTI. Neck supple.

Suprasternal, intercostal, and subcostal retractions present. Breath sounds are faint throughout the chest, without auscultatory rales, wheezes, or stridor heard. Heart sounds are distant, and no murmur is heard. Pulses are strong and regular. Capillary refill is brisk. There are no rashes. Abdominal, neurologic, and musculoskeletal exams are unremarkable.

 

Investigations

A CBC with differential, blood culture, electrolytes, glucose, UA and CXR are obtained. Room air ABG: pH 7.33, pCO2 46, pO2 43 in room air. On oxygen by mask, his pO2 increased to 150.

A chest radiograph is obtained.

 

 

[DDET View CXR comments]

This CXR shows hyperlucency of the left chest with a mediastinal/cardiac shift to the right. [/DDET]

 

Should I get my needle out ASAP?

[DDET Answer and explanation]

Before needling the chest (2nd intercostal space, midclavicular line with an 18 or 20G catheter over the needle) review the evidence for a tension pneumothorax.

This infant has respiratory distress with hypoxia. Breath sounds were described as faint throughout the chest rather than unequal. Is this consistent with a tension pneumothorax? Yes, infants with tension pneumothorax rarely have unequal breath sounds. The intrathoracic volume of the infant’s chest is so small and the mediastinum is so mobile that decreased ventilation due to free air compressing both lungs usually results in distant or faint breath sounds and decreased chest movement bilaterally, rather than the differential findings between the two sides seen in adults.

This infant’s circulation does not appear compromised clinically. The patient was alert with good pulses and capillary refill. Is this consistent with tension pneumothorax? No, the hallmark of tension pneumothorax is persistent hypoxia (despite supplemental oxygen) with circulatory compromise (hypotension and/or bradycardia).

The fact that this patient did not have impaired perfusion should make you refrain from needling the chest and examine the CXR more carefully.[/DDET]

 

Re-examine the CXR above and view new CXR comments

[DDET Answer and explanation]

What at first appears to be a tension pneumothorax may instead be severe emphysema of one or more lobes of the lung. Every attempt should be made to visualise lung markings and the lung edge within the hyperlucent space. Remember that lung markings may be very faint because the blood vessels are spread out.

Additionally, there may be reflex hypoxic vasoconstriction as an attempt to match VQ. Carefully examining the CXR using a hot light may prevent you from mistakenly needling the chest and causing a severe complication.

There are indeed lung markings throughout the left chest. (These are evident on the original film, but it was very difficult to reproduce this on the scanned image).[/DDET]

 

Clinical Progress

You decide to intubate the patient and transfer to the ICU, but the patient’s condition worsens after intubation.

 

What can I do?

[DDET Answer and explanation]

If this patient’s emphysema becomes life-threatening (which may happen rapidly if positive pressure is applied) the only treatment would be a lateral thoracotomy to allow the lung to herniate out of the chest.

When you call the surgeon, he/she asks if you are sure this is not hypoplasia of the right lung or a diaphragmatic hernia. [/DDET]

 

How do I support my  diagnosis of emphysema on CXR?

[DDET Answer and explanation]

There are several parameters to assess in order to answer this question.

Before anything else, it is essential to evaluate the CXR for the presence of any rotation. A rotated chest film can both mimic and obscure a mediastinal shift. Evaluation of the clavicles is one recommended method, but is often confounded by irregular positioning of both clavicles.

Another useful method is to evaluate the horizontal length of the ribs at the mid-chest level measuring from the lateral chest to the centre of the spine on either side. If one side is longer, the patient is rotated to that side and all structures will appear to be falsely shifted to the same side.[/DDET]

 

[DDET View rotated CXR]

rotated cxr

 

 

This neonatal CXR is rotated, as can be determined by looking at the location of the proximal clavicles and the non-symmetry of the rib origins. This gives the CXR the appearance of left sided hyperexpansion with the heart pushed over to the right; however, this appearance is purely due to rotational artifact. Once the degree, if any, of rotation has been determined, several other areas should be evaluated.

The bony thorax may show increased space between the ribs on one side, indicative of emphysema or pneumothorax. The diaphragms should be evaluated for position and evidence of compression or elevation. A flattened (compressed) hemidiaphragm implies emphysema of an adjacent lobe or tension pneumothorax. An elevated hemidiaphragm implies volume loss in that hemithorax due to atelectasis, hypoplasia or a diaphragmatic hernia. A decubitus film can demonstrate failure of the emphysematous lobe to deflate when placed down. Fluid in the hemithorax will displace the heart, but would appear radiopaque.[/DDET]

 

[DDET View patient’s CXR again and then read comments]

Our patient’s CXR shows:

1. Hyperexpanded left “lung” (actually the left upper lobe) that herniates into the right chest.

2. Spreading of ribs of the left chest.

3. Shift of the mediastinum to the right.

4. Compression of the left hemidiaphragm.

5. Left lower lobe atelectasis (It is so small, that you can hardly see it. It is largely obscured.) visible in the left inferior medial chest.

6. Normal position of the right hemidiaphragm.

7. No infiltrates or fluid.

8. All these findings are consistent with emphysema of the left upper lobe.[/DDET]

 

Learning points

  • An important aspect of paediatric emergency care is to be aware of congenital anomalies and the manner and timing with which they present.
  • The differential diagnosis of any acute medical presentation in the first few months of life must include congenital problems. Within the first weeks of life, respiratory and cardiac problems often present precipitously. This patient had congenital lobar emphysema of the left upper lobe and was also found to have a patent ductus arteriosus. The history suggests mild symptoms since birth with acute deterioration. At lobectomy, the left upper lobe bronchus was noted to have abnormalities of the cartilage structures. The bronchus was collapsed with an intraluminal mucous plug.
  • Emphysema may be caused by cartilaginous malformation, intrinsic obstruction, or extrinsic compression. This condition is most common in the upper lobes and associated in 10% of cases with congenital heart defects, most commonly patent ductus arteriosus. Most cases present with respiratory distress within the first 4 months of life and may eventually require resection. Occasionally, asymptomatic cases are found fortuitously on chest radiographs in later years.
  • Evaluation for coexisting congenital anomalies may be made through non-invasive tests such as echocardiography, CT, MRI, and ventilation-perfusion lung scan.
  • Be Aware of . . . Whenever regional emphysema is present in the lung, suspicion of a foreign body should be very high. The young age of our patient made this unlikely but in the high-risk age group, approximately 5 months to 5 years of age, this diagnosis must be pursued even in the face of a negative history. Often bronchoscopy is needed to make the diagnosis and alleviate the condition. Also, think of a foreign body when faced with cases of recurrent wheezing or pneumonia (See Case 8 of Volume 1, Foreign Body Aspiration in a Child).
  • If this infant had a true tension pneumothorax, staphylococcal pneumonia should be highly suspected. It is most common in the first six months of life and often has an extremely rapid onset with fever, tachypnea, and grunting. Commonly, endobronchial infection ruptures through to the pleural space, creating a bronchopleural fistula early in the course of disease, leading to life-threatening pneumothorax and/or empyema. This requires urgent placement of a chest tube, along with appropriate antibiotics and treatment for septic shock. Staphylococcal pneumonia develops rapidly and initial CXR findings may show no evident infiltrate or only a small amount of pleural fluid.

 

References

Gerbeaux J, Couvreur J, Tournier G. Pediatric Respiratory Disease, second edition. New York, J. Wiley and Sons, 1982, pp. 217-223.

Markowitz RI, Mercurio MR, Vahjen GA, Gross I, Touloukian RT. Congenital Lobar Emphysema. Clinical Pediatrics 1989;28(1):19-23.

Scarpeli EM, Auld P, Goldman HS. Pulmonary Disease of the Fetus, Newborn, and Child. Philadelphia, Lea & Febiger, 1978, pp. 194-196.

Templeton JM. Thoracic Emergencies. In: Fleisher GR, Ludwig S. Textbook of Pediatric Emergency Medicine, third edition. Baltimore, Williams & Wilkins, 1993, pp. 1336-1362.

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Prof Loren Yamamoto MD MPH MBA. Professor of pediatrics at the University of Hawaii and a practising pediatric emergency doctor in Honolulu. | Contact | View Loren's DFTB posts