# How Dr. Forrest Bird's Mechanical Respirator Controls Patient Breathing

> A 1965 patent describing a mechanical ventilator that automatically switches between inhaling and exhaling based on pressure levels in a patient's airway.

- **Patent:** US 3191596
- **Original title:** Respirator
- **Owner:** Individual
- **Granted:** 1965
- **Status:** Public domain (expired)
- **Times cited:** 78
- **Field:** mechanical, biotech

## What it does

The device acts as an automated breathing controller that connects a pressurized gas source to a patient's airway. It uses a main valve to toggle between inhalation and exhalation phases. The system monitors the air pressure at the patient's airway; when the pressure hits a specific threshold, the controller automatically closes the valve to end inhalation. If the pressure fails to reach that threshold within a set time, a secondary valve system triggers an additional flow of gas to ensure the patient receives the required volume of air.

## What it does NOT cover

- Does not cover electronic or microprocessor-based control systems.
- Does not cover non-pressure-sensitive ventilation methods.
- Does not cover portable manual resuscitation bags (Ambu bags).

## The clever bit

The invention uses a fail-safe pneumatic timer that detects when a patient is not receiving enough pressure, automatically injecting extra gas to maintain the breathing cycle.

## Real-world examples

1. Bird Mark 7 respirator
2. Hospital mechanical ventilators
3. Emergency medical transport ventilators

## Why it matters

This patent represents a foundational step in modern critical care medicine. Forrest Bird's inventions moved ventilation from bulky, iron-lung style machines to portable, reliable devices that could be used in ambulances and emergency rooms, saving countless lives during respiratory failure.

## Frequently asked questions

### What does How Dr. Forrest Bird's Mechanical Respirator Controls Patient Breathing cover?

A 1965 patent describing a mechanical ventilator that automatically switches between inhaling and exhaling based on pressure levels in a patient's airway.

### Who owns patent US 3191596?

Individual owns this patent, granted in 1965.

### 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 3191596 cited by?

This patent has been cited by 78 later patents that build on its ideas.

### What problem does this patent solve?

This patent represents a foundational step in modern critical care medicine. Forrest Bird's inventions moved ventilation from bulky, iron-lung style machines to portable, reliable devices that could be used in ambulances and emergency rooms, saving countless lives during respiratory failure.

### What does this patent NOT cover?

Does not cover electronic or microprocessor-based control systems.

**Full plain-English explainer:** https://patentbrief.org/patent/us/3191596/bird-respirator-ventilator

**Original patent:** https://patents.google.com/patent/US3191596

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._


## Related patents

Semantically similar inventions in the PatentBrief corpus:

- [How the Iron Lung Artificial Respirator Works](https://patentbrief.org/patent/us/1906844/iron-lung-respirator-drinker) — A 1933 patent for a mechanical respirator that uses external air pressure changes to force a patient's lungs to expand and contract.
- [How CPAP Machines Gradually Increase Air Pressure for Sleeping Patients](https://patentbrief.org/patent/us/5199424/cpap-sleep-apnea-sullivan) — A 1993 patent describing a CPAP machine that lets patients choose how slowly the air pressure ramps up to their therapeutic level, making it easier to fall asleep.
- [How the Aqua-Lung Scuba Regulator Works](https://patentbrief.org/patent/us/2485039/aqualung-scuba-cousteau-gagnan) — The foundational 1947 patent by Jacques Cousteau and Emile Gagnan for the automatic demand regulator that allows divers to breathe compressed air underwater.
- [How the First Heart-Lung Machine Oxygenated Blood](https://patentbrief.org/patent/us/2702035/heart-lung-machine-gibbon) — A 1955 invention that allowed surgeons to oxygenate a patient's blood outside the body, enabling the first successful open-heart surgeries.
- [How Early Vehicle Airbag Safety Systems Work](https://patentbrief.org/patent/us/3552770/automotive-airbag-safety-device) — A 1968 patent describing an early vehicle safety system that uses a rapidly inflating confinement to protect passengers during a collision.