CHEST SEALS. THREE SIDES OR FOUR SIDES?

 

OPEN PNEUMOTHORAX AND IMPROVISED CHEST SEALS

THREE SIDES OR FOUR SIDES?

A Definitive DoD, NATO, ACS, ATLS, PHTLS, TCCC, TECC, and Combat Experience Review (Updated 2026)

By DrRamonReyesMD ⚕️ EMS Solutions International

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EXECUTIVE SUMMARY

If an operator, medic, paramedic, physician, combat lifesaver, first responder, or civilian rescuer must improvise a chest seal using plastic, sterile packaging, IV bags, occlusive dressings, or other non-engineered materials, the question remains:

Should the seal be secured on three sides or four sides?

After reviewing:

• Department of Defense doctrine
• Joint Trauma System guidance
• Committee on Tactical Combat Casualty Care
• American College of Surgeons
• ATLS
• PHTLS
• TECC
• NATO combat medical doctrine
• Historical combat experience from World War I, World War II, Korea, Vietnam, Iraq, Afghanistan, and Ukraine
• Experimental chest seal research

the answer is clear:

FOR AN IMPROVISED CHEST SEAL:

THREE SIDES

FOR A MODERN VENTED COMMERCIAL CHEST SEAL:

FOUR SIDES AS DESIGNED

This conclusion is not based on tradition.

It is based upon:

• respiratory physiology
• pleural pressure dynamics
• fluid mechanics
• combat casualty outcomes
• experimental animal studies
• modern tactical medicine doctrine

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THE PHYSICS OF AN OPEN PNEUMOTHORAX

The thoracic cavity normally functions as a negative-pressure system.

During inspiration:

• diaphragm descends
• thoracic volume increases
• intrapleural pressure decreases
• air enters through the tracheobronchial tree

When the chest wall is violated:

atmospheric air gains direct access to the pleural space.

The pleural cavity ceases to function as a negative-pressure chamber.

The lung partially or completely collapses.

This is the fundamental pathophysiology of pneumothorax.

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WHY SUCKING CHEST WOUNDS ARE DANGEROUS

Historically, military surgeons observed that some chest wounds appeared to breathe.

Air entered and exited through the wound.

These injuries became known as:

Sucking Chest Wounds

When a chest wall defect is sufficiently large, airflow may preferentially enter through the wound rather than the trachea.

Ventilation efficiency deteriorates.

Gas exchange declines.

Hypoxia develops.

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THE TRUE KILLER IS NOT THE OPEN PNEUMOTHORAX

The true killer is:

TENSION PNEUMOTHORAX

Once intrapleural pressure exceeds atmospheric pressure:

• the lung collapses further
• the mediastinum shifts
• the vena cava becomes compressed
• venous return falls
• cardiac output decreases

The patient develops:

• obstructive shock
• severe hypoxia
• pulseless electrical activity
• death

This mechanism was documented repeatedly during:

• WWI
• WWII
• Korea
• Vietnam
• Iraq
• Afghanistan
• Ukraine

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WHY FOUR-SIDED IMPROVISED SEALS ARE DANGEROUS

This is where physiology becomes critical.

A plastic sheet taped on four sides has:

• no vent
• no valve
• no pressure-relief mechanism

If a pulmonary air leak continues:

air escapes from the injured lung.

The air accumulates inside the pleural cavity.

The seal prevents external escape.

The pleural space becomes a pressure vessel.

The patient can progress toward tension physiology.

In engineering terms:

the system has become:

A CLOSED CONTAINER WITH A CONTINUOUS INTERNAL GAS SOURCE

This is inherently dangerous.

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WHY THREE-SIDED SEALS WERE DEVELOPED

Military medics did not invent the three-sided seal because it was elegant.

They invented it because it worked.

By leaving one edge unsecured:

• air entry is reduced
• air escape remains possible
• pressure accumulation becomes less likely

The unsecured edge acts as a crude one-way pressure relief mechanism.

Not perfect.

Not engineered.

Not equivalent to a vented commercial seal.

But physiologically superior to a completely closed improvised dressing.

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WORLD WAR I

Massive artillery injuries produced devastating thoracic trauma.

Open pneumothoraces were common.

Mortality was extremely high.

Understanding of pleural pressure physiology was limited.

Most treatment focused on:

• wound closure
• drainage
• infection control

The concept of pressure-mediated tension physiology was only beginning to emerge.

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WORLD WAR II

Thoracic surgery advanced dramatically.

Military physicians increasingly understood:

• mediastinal shift
• pleural pressure
• lung collapse

Chest drainage systems became standard.

The importance of controlled evacuation of intrapleural air became evident.

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KOREA AND VIETNAM

Helicopter evacuation transformed trauma care.

Combat physicians recognized tension pneumothorax as a preventable cause of death.

Needle decompression became established.

Open chest wound management evolved toward pressure management rather than simple closure.

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IRAQ AND AFGHANISTAN

The modern era of Tactical Combat Casualty Care produced the most detailed analysis of preventable combat deaths ever conducted.

Work by:

• Butler
• Kotwal
• Eastridge
• Holcomb
• Mabry

demonstrated that thoracic injuries remained a major source of potentially preventable mortality.

The emphasis shifted toward:

• chest seals
• decompression
• finger thoracostomy
• prolonged field care

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UKRAINE 2022–2026

Ukraine reintroduced large-scale conventional warfare.

Mass artillery.

Drones.

Fragmentation injuries.

Delayed evacuation.

Cold-weather operations.

Prolonged casualty holding.

The conflict reinforced a reality known since antiquity:

Medical devices fail.

Supplies run out.

Improvisation becomes necessary.

When commercial vented chest seals are unavailable, improvised management still matters.

The underlying physiology has not changed.

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WHAT DOES THE CoTCCC TEACH?

Current TCCC doctrine does not emphasize the historical three-versus-four-sided debate because it assumes availability of vented chest seals.

Current doctrine recommends:

• vented chest seal application
• continuous reassessment
• decompression when indicated
• chest tube placement as definitive care

If deterioration occurs:

• burp the seal
• remove the seal
• decompress the chest

This recommendation itself confirms the underlying concern:

pressure accumulation beneath an occlusive dressing remains a real threat.

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EXPERIMENTAL EVIDENCE

Kheirabadi et al.

Journal of Trauma and Acute Care Surgery

DOI: 10.1097/TA.0b013e3182988afe

Demonstrated superior prevention of tension physiology with vented chest seal designs compared with completely occlusive systems.

PubMed: https://pubmed.ncbi.nlm.nih.gov/23940861/

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Kotora et al.

Journal of Emergency Medicine

Demonstrated effective evacuation of air and blood using vented chest seal systems in communicating pneumothorax models.

https://www.jem-journal.com/article/S0736-4679(13)00507-6/abstract

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Butler FK et al.

Management of Open Pneumothorax in Tactical Combat Casualty Care

Journal of Special Operations Medicine

https://www.naemt.org/docs/default-source/education-documents/tccc/tcccmp_1708/13-02-tccc-butler-open-pneumo-jsom-2013.pdf

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DEPARTMENT OF DEFENSE CONCLUSION

The DoD standard of care is:

VENTED COMMERCIAL CHEST SEAL

NOT

FOUR-SIDED IMPROVISED PLASTIC

The existence of vented chest seals represents an engineering solution to the same physiological problem that originally motivated the three-sided seal.

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FINAL VERDICT

The question is often framed incorrectly.

The issue is not:

"Three sides or four sides?"

The issue is:

"Can trapped intrapleural air escape?"

If the answer is:

NO

then four-sided closure is potentially dangerous.

If the answer is:

YES

then pressure accumulation becomes less likely.

Therefore:

IMPROVISED CHEST SEAL

THREE SIDES

Because the fourth side functions as a primitive pressure-relief mechanism.

COMMERCIAL VENTED CHEST SEAL

FOUR SIDES

Because the valve or vent system replaces the need for the open side.

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DRRAMONREYESMD RULE 2026

NO VENT = THREE SIDES

VENT = FOUR SIDES

THE OBJECTIVE IS NOT TO CLOSE THE HOLE.

THE OBJECTIVE IS TO PREVENT TENSION PHYSIOLOGY.

Failure to understand that distinction has killed casualties on battlefields from antiquity to Ukraine.

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SELECTED REFERENCES

Kheirabadi BS et al. DOI: 10.1097/TA.0b013e3182988afe https://pubmed.ncbi.nlm.nih.gov/23940861/

Kotwal RS et al. DOI: 10.1001/archsurg.2011.213 https://pubmed.ncbi.nlm.nih.gov/21844425/

Eastridge BJ et al. DOI: 10.1097/TA.0b013e3182755dcc https://pubmed.ncbi.nlm.nih.gov/23192066/

Butler FK et al. https://www.naemt.org/docs/default-source/education-documents/tccc/tcccmp_1708/13-02-tccc-butler-open-pneumo-jsom-2013.pdf

TCCC Clinical Practice Guidelines 2026 https://tccc.org.ua/files/downloads/clinical-guidelines-2026-en.pdf

MSD Manual Professional Open Pneumothorax https://www.msdmanuals.com/professional/injuries-poisoning/thoracic-trauma/open-pneumothorax