Management of Open Pneumothorax in Tactical Combat Casualty Care: TCCC Guideline Change 13-02 Frank K. Butler, MD; Joseph J. Dubose, MD; Edward J. Otten, MD; Donald R. Bennett, MD; Robert T. Gerhardt, MD; Bijan S. Kheirabadi, PhD; Kirby R. Gross, MD; Andrew P. Cap, MD; Lanny F. Littlejohn, MD; Erin P. Edgar, MD; Stacy A. Shackelford, MD; Lorne H. Blackbourne, MD; Russ S. Kotwal, MD; John B. Holcomb, MD; Jeffrey A. Bailey, MD Journal of Special Operations Medicine Volume 13, Edition 3/Fall 2013 PMID: 24048995
There has been some recent debate on the merits of using occlusive dressings on chest wounds. Current TCCC guidelines recommend that all 'open and/or sucking chest wounds should be treated by immediately applying a vented chest seal to cover the defect." The guidelines then go on to state that if no vented seal is available a non vented dressing should be applied and the patient monitored for development of a tension pneumothorax.
The question has been raised (and at least conceptually proven) why should we treat an open pneumothorax with an occlusive dressing potentially converting it to a leathal tension pneumothorax? Why not just leave it alone? (1)
Before continuing a brief overview of physiology may be helpful here. First, the muscles of respiration and the chest wall do not directly pull on the lungs. Rather they expand and create negative pressure (-5mm Hg) (7) in the intrapleural space between the lining of the chest wall (parietal pleura) and the lung (visceral pleura). When an injury allows open communication between atmospheric air and the intrapleural space, that negative pressure which expands the lungs is either diminished or lost. The degree of impact depends on the size of the hole and how much time during the respiratory phase the hole remains patent to the outside. The concern here is that if there is complete loss of the negative pressure in the pleural space for the entire inspiratory phase then that lung will not be ventilated. If it is only open for part of the inspiratory phase (imagine that the lung itself blocks the hole for the first half of the respiratory phase) then partial filling of the lung may occur. In either case this may result in respiratory compromise of the patient.
Any communication with atomospheric pressure and the intrapleural space can create a pneumothorax. There are 3 types of pneumothoraces.
1) Open pneumothorax: injury through the chestwall that extends to the intrapleural space. This is what we classically think of with penetrating trauma.
2) Closed pneumothorax: With no hole in the chest wall it is considered a closed pneumothorax, for example a primary blast injury to the lung or even underlying COPD with ruptured bleb.
3) Tension pneumothorax: A tension pneumothroax develops when the wound remains open longer in the inspiratory phase (allowing air into the chest cavity) than it is open in the expiratory phase (preventing air from escaping the chest cavity). When the pressure in the chest cavity around the lung is greater than the the air pressure in the lung- it collapses and eventually the pressure builds enough to push the heart to the side and slowing blood return to the heart (a mix of physical kinking of the vessels with blood backing up -seen as JVD- and increased intrathoracic pressure which prevents blood returning into the chest to get to the heart) somewhere around 15-20 mmHg intrathoracic pressure.(7) This will be seen as a drop in blood pressure, increased heart rate, drop in O2 sats and classically the deviated trachea and JVD.
A little physics here helps explain that in general air will still prefer to enter the trachea over the wound in the intrapleural space until the trachea is no longer the path of least resistance. This tipping point happens when the hole in the chest wall approaches 1/2 size (area) of the trachea. Poiseuille's Law - look it up, you know you want to....
So in either case - an open pneumothorax that causes oxygen desaturation because of failed oxygenation and ventilation, loss of negative pressure also decreases the amount of blood that returns to the chest and subsquently the heart, or a tension pneumothorax which further decreases cardiac output - and our patient suffers. Add to that hypovolemic shock with already compromised tissue perfusion or a TBI and you have a recipe for disaster.
So why not ignore the open pneumothorax and simply transport? In a system the provides rapid transit to definitive (surgical) repair like civilian EMS, this might be acceptable. With only one pt to worry about you can simply overcome the failure to oxygenate with increased supplemental O2. If a tension pneumorthorax develops, then the standard NCD can be performed. Once a chest tube has been placed, positive pressure ventilation will allow for expansion of the lungs regardless of loss of negative pressure in the intrapleural space.
The paper from the CoTCCC points out that in austure or tactical environments this level of one on one care might not always be possible. Especially in an MCI where your ability to monitor patients will be strained and the ability to provide PPV potentially unrealistic. It is in these settings that the occlusive dressing might be of greatest benefit. A study by Kheirabadi demonstrated in animal models that a vented chest seal could in fact prevent conversion of an open pneumothorax to a tension pneumothorax.(2)
Manufacturers differ in the type of venting system they provide. A study by J Kotora evaluated three vented chest seals: Hyfin by North American Rescue, SAM (SAM Medical Products) and the Sentinel Battle Seal (Combat Medical Systems) all performed equally well in preventing accumulation of a tension pneumothorax in their animal models. (3) While the authors did inject blood into the chest cavity, it was unclear if blood ever came in contact with the vents of the chest seal and if so what the effect was. Nor were there recommendations on what to do if blood was seen at the vents. It seems reasonable that if there is concern you could either burp the chest seal, perform NCD, or replace it. Pt positioning may also be helpful here when circumstances allow it. This is a frequently misunderstood point with medics who confuse which way to place the injured side with the pt in the recovery position. The chest seal should be up allow air to reach the vent and hopefully minimizing risk of blood pooling around the vent. Alternatively, a patient could be left sitting up or reclined if risk of vomiting/aspiration not a concern.
The Asherman chest seal was one of the first vented chest seals in use, but experience and eventually a study showed it failed to adhere sufficiently to bloody or dirty skin (4) compared to the Bolin chest seal. The focus article cites a pending publication that comparing the Bolin, Halo, Sherman, H&H, Hyfin, Russell, SAM-valved, and Sentinel chest seals on volunteers who were sprayed with evaporated or canned milk. The results suggested that the SAM-valved and Bolin chest seals adhered the best.(5)
The article also reminds readers that previous a 2008 CoTCCC review of hasty dressings made of any readily available impermeable material and taped on three sides failed to show any proof that they reliably prevented development of a tension pneumothorax. (5) That said if it's all you have, it might be considered with the understanding that it is no better than a completely occlusive dressing and will necessitate close monitoring of the pt, vs not treating the open thorax.
Of note Kotora did an excellent job pointing out that no chest seal was designed for prevention of accumulation of pneumothorax in a patient on positive pressure ventilation (BIPAP, BVM, ETT on vent, etc).(3) While PPV will allow you to restore adequate expansion of the lung despite loss of intrapleural negative pressure- these patients require a chest tube first.
Bottom Line: Great article and well worth the read. I believe it absolutely justifies the use of vented chest seals for treatment of open pneumothoraces in a tactical environment. Within the civilian sector, if rapid transport is available or if close monitoring of the patient is practical, it may be acceptable to not occlude the open pneumothorax and simply transport. The debate regarding not treating may more appropriately reflect the importance of choosing the right tool for the right job and highlight the critical need for thinking providers. Know what you're treating, know the complications and be prepared to intervene.
Understand the different types of pneumothraces (closed, open, tension). Know that an occlusive dressing is applied to an open chest wound with the intent of allowing at least partial restoration of lung ventilation and oxygenation. The risk of any occlusive dressing is the potential conversion of an open pneumothorax to a tension pneumothorax. Using a vented chest seal decreases that risk. If a tension pneumothorax develops either burp the chest seal, place an NCD or replace the chest seal (if vents become clogged).
1) Frank K. Butler, MD; Joseph J. Dubose, MD; Edward J. Otten, MD; Donald R. Bennett, MD; Robert T. Gerhardt, MD; Bijan S. Kheirabadi, PhD; Kirby R. Gross, MD; Andrew P. Cap, MD; Lanny F. Littlejohn, MD; Erin P. Edgar, MD; Stacy A. Shackelford, MD; Lorne H. Blackbourne, MD; Russ S. Kotwal, MD; John B. Holcomb, MD; Jeffrey A. Bailey, MD. "Management of Open Pneumothorax in Tactical Combat Casualty Care: TCCC Guideline Change 13-02", Journal of Special Operations Medicine, Fall 2013; 13(3) PMID: 24048995
2) B Kheirabadi, et al. "Vented versus unvented chest seals for the treatment of pneumothorax and prevention of tension pneumothorax in a swine model." Journal of Trauma Acute Care Surgery, Jul 2013; 75(1):150-6. PMID 23940861
3) J Kotora, J Henao, L Littlejohn, S. Kircher. "Vented chest seals for prevention of tension pneumothorax in a communicating pneumothorax". The Journal of Emergency Medicine, 2013; 45 (5) 686-694. PMID: 23921173
4) F Arnaud, T Tomori, J Yun, R McCarron, R Mahon. "Evaluation of chest seal performance in a swine model: comparison of Asherman vs. Bolin seal." Injury, 2008 SEP; 39(9): 1082-8. PMID:18589420
5) Supinski DP, Nesbitt ME, Gerhardt RT: Chest seal adherence on human test subjects: a prospective study. Manuscript in preparation. - as cited in the title article.
6) CoTCCC minutes July 2008
7) BA Nicks, D Manthey: Ch 68: Pneumothorax, Tintinalli's Emergency Medicine, A Comprehensive Study Guide, Eighth Edition, 2016.