Major Karl Connell MD (1878-1941)

Major Karl Connell Sr (1878-1941) was an American surgeon, serviceman and inventor

Connell was responsible for some of the first anaesthesia machines that incorporated a carbon dioxide absorber and a gauge that allowed accurate delivery of multiple gases at once. His innovative flair is seen in the steel rectangular-box of his later anaesthesia machines which at the time where cylinders were all the rage, was a true novelty in itself! 

His most famous invention was the Connell Mask, the first all-American gas mask to be used during World War I although a shortage of materials, saw him modify British gas masks to keep up with demand (although still called American masks). After retiring back to civilian life, Connell also a business man, set up the Connell Apparatus Company and went on to obtain 10 patents for a series of anaesthetic machines developed in the 1930’s. Whilst his company did not survive, his legacy does; his designs and ideas, a part of the foundations of modern anaesthesia equipment today.

  • Born on July 4, 1878 at Omaha, Nebraska. Son of WJ Connell, prominent Omaha lawyer, and the nephew of RW Connell, Nebraska health commissioner
  • 1898-1900 educated in Creighton University Medical College and the College of Physicians and Surgeons at Columbia University (MD, 1900)
  • 1904 – elected a Fellow of the Academy
  • 1910-1914 associate in surgery in Columbia University and an assistant attending surgeon from at the Roosevelt Hospital in New York (1908-1918). During his work he notes the inefficiency of anaesthesia equipment which could not provide a steady flow of gases leading to patients fluctuating between deep and shallow anaesthesia. At this time, the most common method of anaesthesia was ‘dripping’ anaesthetic liquids onto face masks.
  • 1911 – joins the 71st Regiment, New York National Guard
  • 1912 – invents the Anaesthetometer. This model was cylindrical, but subsequent models were rectangular and stainless steel – a right novelty! It is one of the first anaesthesia machines to accurately deliver known percentages of gases including ether, nitrous oxide and oxygen. A rebreather circuit is later added.
  • 1913 – introduces a metal oropharyngeal airway (Connell Airway) to counter the problem of patient’s bite occluding the earlier rubber airways. This is produced up until the 1960’s
  • 1915 – established an Advance Hospital Unit in France; toured Germany and Austria as accredited sanitary observer for the National Guard of New York. On return to the US assigned by the Surgeon General to the problems of wound treatment and standardization of the surgery in the Advance Zone.
  • 1916 – becomes a member of the Medical Council of National Defence; serves as a Major in the Chemical Warfare Service with the AEF between 1917-1919 where he develops the Connell mask for gas defence in war. This earns him the Distinguished Service Medal in 1919
  • 1917 – develops the Gas-Oxygen Apparatus it allowed for the greater control over the delivery of anaesthetic gases. It was also more portable and thus found home among the US and Allied Forces during WWI where it was used in many field hospitals. It was dubbed the “Connell’s War Special
  • 1919-1924 demobilised from the military and returns to civilian life. Professor of surgery at Creighton University, Omaha. During this period also founds the Presbyterian Hospital (1920) and serves as its president until 1924
  • 1925 – retires from medical practice and devotes the next six years to designing anaesthestic apparatus to a total of 10 patents.
  • Founds the Connell Apparatus Company which is sold in 1940 to the Ohio Chemical Company
  • Died on October 18, 1941 at Searsdale, New York from a heart attack

Medical Eponyms
Connell Airway (1912)

Was the Connell take of the classic oropharyngeal airway which at the time was made from rubber. Whilst effective (as a one of the first rudimentary airway devices), it could be easily occluded by the patient’s bite. Connell thus introduced a metal version of the oropharyngeal airway which was shaped to fit the roof of the mouth and upper throat – a design that would persist on in later airways

Connell Airway (1912) 1947 model
Connell Airway (1912) – 1947 model

Anæsthetometer (1913)

Anæsthetometer: This word has been coined, in the lack of an existing term, to designate an apparatus or instrument for the automatic measuring and mixing of vapors and gases used in anesthesia and for other purposes.

Connell. 1913

The first anaesthesia apparatus developed to deliver known percentages of ether, nitrous oxide, and oxygen. It was also intended to be used for artificial respiration and oxygen therapy.  Its finely calibrated controls set a new standard.

Connell described the first, cylindrical model of his Anesthetometer in 1912 and introduced the rectangular version in 1915. Both designs used the body of a meter built to supply and measure gas for household lighting.

CONNELL Anæsthetometer 1913 Major Karl Connell
Connell Anæsthetometer 1913

Connell Gas Mask

Developed during his time in military service, Connell was tasked with working on gas defence however never quite made it to British Gas Defence School. Instead, his prior work on anaesthesia gas masks caught the attention of the head of the Gas Service Section where during an interview, Connell was quick to propose modifications to the already existing gas masks. Clearly, the impression Connell left had him skip gas defence school and shipped to Paris where he developed the first prototype of his mask which he wore himself in a chlorine gas chamber.

After further modifications, the Connell Mask was distributed to front lines and embedded into American History. The mask comprised a metal face plate and foam rubber to provide a face seal and a filter at the back of the head, a departure from the typical US gas masks where the filters were positioned on the chest. A layer of paper in the filter added an extra line of defence and removed particulates (e.g. sneezing agents) passing through the activated charcoal. It was secured on the head by an elastic harness.

The mask was more comfortable to wear and had less fogging of the eye pieces achieved by the Tissot mask’s principal of drawing air across the eyepieces. This meant that the eye pieces were repeatedly exposed to cooler air than the air within the mask which prevented condensation. Because of demand and issues with foam supply, the Military opted to purchase British masks which Connell would then modify to match the Connell mask – and so the British mask quite quickly became an American mask.

An estimated 1000 Connell masks were manufactured in Great Britain and sent to the US. It was later superseded by the AT and KT gasmasks. 

Connell gas mask
Connell Mask

Connell Model

The Connell Anaesthesia machines were a series of machines developed in the 1930’s which allowed for the accurate titration of multiple gases to the patient by means of ball-bearing gauges or ‘flow meters.’ This flowmeter design set a new standard in the industry. His machines also were among the first to incorporate a carbon dioxide absorber.

Models could deliver carbon dioxide, oxygen, ethylene, nitrous oxide, cyclopropane, ether and helium. To counter the danger associated with using flammable agents, the Connell Models incorporated safety features such as glass domes to allow visibility of valves and gas flow and conducting wires fixed within the rubber breathing tubes to reduce the possibility of explosion. Indeed, they were advertised as ‘explosion proof machines.’ An inbuilt humidifier was also incorporated.

Earlier models were cylindrical in shape. The stainless-steel rectangular version introduced a novelty to the industry.

Major Publications



Eponymous terms


the person behind the name

Emergency registrar at Sir Charles Gairdner Hospital, Perth

BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |


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