Tag Archives: respiratory

Missed PTX signs on CXR

Chest x-rays often miss pneumothoraces in the trauma room. These are occult pneumothoraces. A study using agreement by two fellowship trained radiologists as the gold standard for CXR interpretation showed that 80% of these were truly occult, ie. not detectable by the radiologists from CXR and only demonstrable on CT. Of those seven cases that could or should have been identified by emergency physicians (ie. ‘missed’ pneumothoraces) subcutaneous emphysema (5), pleural line (3), and deep sulcus sign (2) were detected by the radiologist reviewers.

This serves both as a reminder of the signs to look for on CXR for pneumothorax, and of the inadequacy of plain radiography in trauma patients. The authors advise in their discussion that  ‘Thoracic ultrasonography may be the ideal diagnostic modality as it has a high sensitivity for the detection of PTX and it may be performed quickly at the bedside while maintaining spinal precautions’.

If you don’t know how to detect a pneumothorax with ultrasound yet, have a look here.

Occult Pneumothoraces Truly Occult or Simply Missed: Redux
J Trauma. 2010 Dec;69(6):1335-7

Magnesium in asthma limits tachycardia

Dr WFS Sellers and colleagues describe several cases that demonstrate convincingly a protective effect of intravenous magnesium sulphate against the tachycardia produced by intravenous salbutamol in patients with asthma. This effect was observed both when magnesium was given before and when given after the salbutamol. It was seen in critically ill asthmatic patients and in a volunteer with well-controlled asthma.

Intravenous magnesium sulphate increases atrial contraction time and refractory times. It is used to treat atrial tachyarrhythmias and has a negative chronotropic and dromotropic effect.

Intravenous magnesium sulphate prevents intravenous salbutamol tachycardia in asthma
Br J Anaesth. 2010 Dec;105(6):869-70

Hypertonic saline in bronchiolitis

A Canadian randomised controlled trial compared nebulised 3% saline with 0.9% saline in 81 infants under 2 years of age with bronchiolitis. The short-term use of nebulised 3% saline did not result in any statistically significant benefits, although a non-significant trend toward a decrease in hospital admission and improvement in respiratory distress was found. A larger study would be required to determine whether these trends arise from a clinically relevant treatment effect.

There’s really not much that’s been shown to make a difference in this disease, as this review article reminds us.

Effect of inhaled hypertonic saline on hospital admission rate in children with viral bronchiolitis: a randomized trial.
CJEM. 2010 Nov;12(6):477-84

A-a gradient unhelpful in pregnancy

"Man, she's enormous. I can't reach the chest to auscultate!"

Given that thromboembolism is the leading cause of maternal death in the UK according to the latest UK CEMACE report, it would be nice to have reliable non-ionising tests in the ED to rapidly rule out this disease in pregnant women. Unfortunately, the alveolar-arterial oxygen gradient does not do the job.

A recent study compared the A-a gradient with CTPA as the gold standard. Of 102 patients who were pregnant or up to 6 weeks post-partum, there were 13 PEs (2 antepartum and 11 postpartum). The best sensitivity, specificity, and negative and positive predictive values for A-a gradients were 76.9%, 20.2%, 80.0%, and 11.5%, respectively.

Assessment of the alveolar-arterial oxygen gradient as a screening test for pulmonary embolism in pregnancy
Am J Obstet Gynecol. 2010 Oct;203(4):373.e1-4

High flow O2 and mortality in COPD

An Australian randomised controlled trial of pre-hospital oxygen therapy in COPD patients compared titrated oxygen therapy with high flow oxygen. The primary outcome was prehospital and in-hospital mortality.

Titrated oxygen treatment was delivered by nasal prongs to achieve arterial oxygen saturations between 88% and 92%, with concurrent bronchodilator treatment administered by a nebuliser driven by compressed air. High flow oxygen was 8-10 l/min administered by a non-rebreather face mask, with bronchodilators delivered by nebulisation with oxygen at flows of 6-8 l/min.
Titrated oxygen treatment significantly reduced mortality, hypercapnia, and respiratory acidosis compared with high flow oxygen in acute exacerbations of chronic obstructive pulmonary disease. The authors claim: ‘For high flow oxygen treatment in patients with confirmed chronic obstructive pulmonary disease in the prehospital setting, the number needed to harm was 14; that is, for every 14 patients who are given high flow oxygen, one will die.

The authors did not report data on the in-hospital management of the patients.

Effect of high flow oxygen on mortality in chronic obstructive pulmonary disease patients in prehospital setting: randomised controlled trial
BMJ. 2010 Oct 18;341:c5462

Pneumonia scores equivalent

Got a favourite assessment tool for classifying the severity of community acquired pneumonia? Two systematic reviews showed no significant differences in performance between Pneumonia Severity Index (PSI) and various versions of CURB (CURB, CURB-65, and CRB-65).
An accompanying editorial* opines that CRB-65 is the simplest tool and can easily be remembered. It also discusses some of the more subtle strengths and weaknesses of the tools.

Severity assessment tools for predicting mortality in hospitalised patients with community-acquired pneumonia. Systematic review and meta-analysis
Thorax. 2010 Oct;65(10):878-83

Value of severity scales in predicting mortality from community-acquired pneumonia: systematic review and meta-analysis

Thorax. 2010 Oct;65(10):884-90

*Severity scores for CAP. ‘Much workload for the next bias’
Thorax 2010 Oct;65:853-855

Bronchiolitis – not much works

A review article on bronchiolitis reminds us that there is little evidence to support any specific therapies. Bronchodilators, steroids, adrenaline (epinephrine), CPAP, heliox, mucolytics and leukotriene antagonists are all reviewed. Of these, inhaled 3% saline as a mucolytic has some promise in that studies show it to reduce length of stay in admitted patients by one day. CPAP has been shown to reduce pCO2 but evidence of further benefit may have been limited by a lack of adequately powered studies.

Current Therapies in Bronchiolitis
Pediatr Emerg Care. 2010 Apr;26(4):302-7

Steroids for pneumonia?

Steroids are useful in asthma and COPD exacerbations, which are lung problems. Pneumonia is a lung infection, so steroids might help there too right? Erm… no.

A double blind randomised controlled trial demonstrated no benefit from steroids (prednisolone) versus placebo in patients with community acquired pneumonia, and late therapaeutic failure (>72 h after admission) was more common in the prednisolone group.
Efficacy of Corticosteroids in Community-acquired Pneumonia: A Randomized Double-Blinded Clinical Trial
Am J Respir Crit Care Med. 2010 May 1;181(9):975-82

B lines be gone!

Vicki Noble’s Emergency Ultrasound team describe the resolution of Songraphic B lines on the lung ultrasound of a patient with end stage renal disease who presented with dyspnoea due to pumonary oedema which was treated with CPAP.
B-lines are hyperechoic vertical lines that originate at and slide with the pleura and extend radially to the edge of the screen without fading. Isolated B-lines may be seen in normal lungs, but diffuse B-lines in multiple zones indicate interstitial thickening, most commonly seen in congestive heart failure (CHF).

Image from cardiovascularultrasound.com

This case is interesting because it describes real-time resolution of B-lines during therapy in the ED demonstrating that in CHF, B-lines reflect acute rather than chronic changes within lung parenchyma.
Real-time resolution of sonographic B-lines in a patient with pulmonary edema on continuous positive airway pressure
Am J Emerg Med. 2010 May;28(4):541.e5-8