How the Iron Lung Artificial Respirator Works
A 1933 patent for a mechanical respirator that uses external air pressure changes to force a patient's lungs to expand and contract.
Original patent title: “Artificial respirator”
A 1933 patent for a mechanical respirator that uses external air pressure changes to force a patient's lungs to expand and contract. Granted to Individual in 1933 with 7 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
The device, commonly known as an iron lung, creates a sealed environment around a patient's body, leaving only the head exposed. By using a pump to rhythmically lower and raise the air pressure inside the chamber, the device forces the patient's chest to expand and deflate. This mechanical action mimics the natural process of breathing for individuals who have lost the ability to control their own diaphragm muscles.
The gap
What does this patent NOT cover?
- Does not cover positive-pressure ventilators that push air directly into the lungs through a tube.
- Does not cover portable or wearable breathing assistance devices.
- Does not cover electronic sensors or automated feedback loops for monitoring blood oxygen levels.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The invention cleverly uses external negative pressure to manipulate the chest wall, avoiding the need for invasive procedures or direct intubation of the patient's airway.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
The Drinker Respirator
Historical polio ward iron lung machines
Why it matters
The bigger picture
This invention was critical during the mid-20th century polio epidemics, providing life-saving support for patients suffering from respiratory paralysis. It represents a foundational moment in intensive care medicine, proving that mechanical intervention could sustain life during prolonged respiratory failure.
Filed
November 27, 1931
Granted
May 2, 1933
Market context
Who's building on this
Companies in this space
Modern respiratory care has largely moved toward positive-pressure ventilation, with companies like Medtronic and Philips leading the development of advanced ventilators. The iron lung is now a historical artifact, though its principles influence modern non-invasive ventilation techniques.
Market impact
This patent enabled the establishment of the first specialized intensive care units. It set the standard for life support technology before the transition to modern, computerized positive-pressure ventilation systems.
Claim 1 — Plain English
What this patent covers
The device, commonly known as an iron lung, creates a sealed environment around a patient's body, leaving only the head exposed. By using a pump to rhythmically lower and raise the air pressure inside the chamber, the device forces the patient's chest to expand and deflate. This mechanical action mimics the natural process of breathing for individuals who have lost the ability to control their own diaphragm muscles.
The clever bit
The invention cleverly uses external negative pressure to manipulate the chest wall, avoiding the need for invasive procedures or direct intubation of the patient's airway.
What it does not cover
- Does not cover positive-pressure ventilators that push air directly into the lungs through a tube.
- Does not cover portable or wearable breathing assistance devices.
- Does not cover electronic sensors or automated feedback loops for monitoring blood oxygen levels.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Limited data
Citation count
18/40
Early citations
Claim breadth
0/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$11K – $34K
Midpoint $21K · expired or expiring · industry ×2.2
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
Concepts involved
Citations
Patent lineage
Cite this patent
Agassiz, S. L., & Philip, D. (1933). How the Iron Lung Artificial Respirator Works (U.S. Patent No. 1,906,844). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/1906844/iron-lung-respirator-drinker
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How the Iron Lung Artificial Respirator Works cover?
A 1933 patent for a mechanical respirator that uses external air pressure changes to force a patient's lungs to expand and contract.
Who owns patent US 1906844?
Individual owns this patent, granted in 1933.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 1906844 cited by?
This patent has been cited by 7 later patents that build on its ideas.
What problem does this patent solve?
This invention was critical during the mid-20th century polio epidemics, providing life-saving support for patients suffering from respiratory paralysis. It represents a foundational moment in intensive care medicine, proving that mechanical intervention could sustain life during prolonged respiratory failure.
What does this patent NOT cover?
Does not cover positive-pressure ventilators that push air directly into the lungs through a tube.
Same assignee
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