1. The inventions of John Blease
A.G. McKenzie 
British Journal of Anaesthesia 
Volume 85, Issue 6, Pages (December 2000)
DOI: /bja/
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

2. Fig 1
John Blease and the ‘Blease Special’ (courtesy of Mr M. A. Blease).
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

3. Fig 2
Roberts dental anaesthetic machine (courtesy of Mr M. A. Blease).
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

4. Fig 3
Alfo-Blease anaesthetic machine, circa Prior to this, the head bore the insignia ‘Alfo-Blease’ (© Thackray Medical Museum, 2000).
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

5. Fig 4
Drawing of prototype of Blease ‘Pulmoflator’, 1947 (modified from British Patent 625,284). Key: 1, glass cylinder; 2, rubber rebreathing bag; 3, corrugated tubing to anaesthetic apparatus; 4, inflation pressure gauge; 5, adjustable expiratory valve (semi-closed circuit); 6, hand bellows (closed circuit); 7, compression chamber; 8, rotary pump with air inlet; 9, belt gearing; 10, electric motor; 11, cam; 12, adjustable deflation valve (cam operated); 13, manual valve to discontinue pressure; 14, branch for introduction of oxygen, nitrous oxide; 15, inflation pressure gauge; 16, inspiratory valve; 17, auxiliary inlet to enable introduction of oxygen or carbon dioxide. Modus operandi The ‘bag in a bottle’ is rhythmically squeezed by the electric compressor through the cam and valve mechanism.
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

6. Fig 5
Drawing of early Blease ‘Pulmoflator’, 1949 (modified from British Patent 649,229). Key: 1, face-mask; 2, flexible tubing; 3, valved head; 4, air chamber; 5, casing, housing the operating mechanism; 6, carbon dioxide absorber (soda-lime); 7, pipe for introduction of anaesthetic gas from source; 8, source; 9, pump for supplying air through tubing 13, to another air chamber (within 5, separated by a flexible diaphragm from a vacuum chamber); 10, manually controlled valve to disconnect tubing 2 from head 3 and connect 2 to tubing 11 leading to rubber bag 12 for manual respiration; 14, knob to control needle valve for adjusting inspiratory time; 15, knob to control needle valve for adjusting expiratory time; 16, control lever for compression spring (resisting the diaphragm), which regulates inflation pressure; 17, control lever for slide valve to hold lungs inflated; 18, lever for manual control of respiration; 19, pressure gauge. Modus operandi The ‘bag in a bottle’ is rhythmically squeezed by the electric compressor through the ‘cycling box’, which is a spring-diaphragm-ratchet device explained in Fig. 6.
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

7. Fig 6
Drawing of New Blease ‘Pulmoflator’ (P.1), Key: 1, pressure chamber; 2, compressed air inlet; 3, concertina reservoir bag; 4, tubing to patient; 5, flexible diaphragm; 6, compression spring within vacuum chamber; 7, exhaust valve; 8, control lever for cycling pressure; 9, needle valve controlling duration of expiratory phase; 10, needle valve controlling rate of inflation; 11, slide valve to hold lungs inflated; 12, control lever for 11; 13, positive pressure safety valve; 14, valve to allow spontaneous breathing (inactivating ventilator); 15, adjustable spring-loaded spill valve; 16, ‘manual/auto’ control; 17, one-way valve; 18, breathing bag (for manual ventilation); 19, pointers; 20, calibrated scale; 21, manometer; 22, notched disc; 23, compression/expansion spring; 24, activating rod; 25 and 26, ratchet bars; 27 and 28, striking pins; 29, connecting rod. Modus operandi Compressed air enters the main chamber and acts on the outside of the concertina bellows, the contents of which therefore inflate the patient's lungs. During this phase the diaphragm is displaced to the right and the notched disc rotates clockwise. At the crucial point the ratchet mechanism flicks over, opening the exhaust valve so that the pressure in the main chamber falls to atmospheric and expiration occurs. The spring pressing on the diaphragm causes it to move in the opposite direction until the ratchet flicks over again, closing the valve and restarting the inspiratory phase.
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

8. Fig 7
Drawing of triggering device, 1959 (modified from British Patent 848,725). Key: 1 air chamber; 3 Venturi-effect device; 5 two-way differential valve; 6 collapsible bellows; 7, 8 one-way valves; 9 pipe to patient; 10 diaphragm; 11 low-pressure chamber; 12 rod with valves 13; 14 spring with regulator 15; 16, 17 adjustable bleed valves; 18 triggering mechanism comprising chamber 19 with bowed diaphragm 20, spring-loaded by spring 21 with regulator 22; 23 rod; 24 non-return valve; 25 pipe, leading from patient connection through a one-way valve 27 to the Venturi-effect device 3, which operates to apply a partial vacuum to the patient's lungs; 26 pipe leading from 25 to the chamber 19 of the triggering mechanism; 28 pressure gauge; 29 pointer, which moves over a scale 30, to indicate the degree of deflation of bellows 6 (i.e. tidal volume). Modus operandi If the patient attempts to breathe, the slight negative pressure in the breathing system lifts the diaphragm 20, opening the valve 24 and admitting air to the low pressure chamber 11. Thereupon the diaphragm 10 moves quickly to the left, closing valve 13. As a result the pressure in the air chamber 1 builds up, squeezing the contents of the bellows into the patient's lungs.
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

9. Fig 8 Blease ‘Pulmoflator’ Model P11 (courtesy of Mr MA Blease).
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

10. Fig 9
Drawing of apparatus for constant volume ventilation, 1959 (modified from British Patent 885,221). Key: 1, transparent chamber which is cyclically pressurized and vented to atmosphere through opening 2, (by pressure-operated valve mechanism); 3, collapsible bellows; 4, inlet pipe for admission of air or gases; 5, inlet port; 6, outlet port; 7, outlet pipe to patient; 8, scale with pointer 9 for indication of tidal volume; 10, threaded rod with knob 11 at its upper end and a stop 12 at its lower end, arranged to co-operate with an abutment 13; 14, depending rod; 15, lock nut. Modus operandi Adjustment of 10–15 facilitates presetting the stroke of the bellows.
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

11. Fig 10
Drawing of prototype of Manley ventilator, 1960 (modified from British Patent 900,866). Key: 1, bellows, connected to a source of gases under pressure, and in communication with a 2nd bellows 2 through tube 3 containing a two-way tap 4; 5, valve (V1); 6, pivoted frame, biassed by means of tension spring 7; 8, pivoted frame, adjustably biassed by a movable jockey weight 9; 10, movable contact coupled to valve 5 (V1); 11, arcuate arm, having adjustable stop member 12; 13, contact, coupled to valve 5 (V1); 14, wide bore tube leading from bellows 2 to inhalation valve 15 (V2) attached to 16 spring biased diaphragm in small pressure chamber; 17, flexible tubing to patient; 18, exhalation valve (V3) attached to 19 spring biased diaphragm in small pressure chamber; 20, expiratory valve; 21, by-pass tube from two-way tap 4 to facilitate manual respiration; 22, breathing bag; 23, tube, pneumatically linking valves V1, V2 and V3; 24 valve (needle and seating) which closes when bellows 1 is empty, providing a constant back pressure on the rotameters. Modus operandi: Inspiration; pressure generator (from weighted bellows 2). Bellows 1 fills during this phase. Inspiratory–expiratory cycling; time cycled by the filling of bellows 1 until contact 10 trips a toggle and lever (bistable) system and valve 5 (V1) opens. Due to the pneumatic linking 23, this causes valve 15 (V2) to close and valve 18 (V3) to open. Expiration; passive pressure generation to atmosphere. Bellows 1 empties and bellows 2 fills during this phase. Expiratory-inspiratory cycling; volume cycled by the setting of 12, so that when bellows 2 has filled to the set volume, contact 13 trips the toggle and lever (bistable) system in the other direction—valve 5 (V1) closes, valve 15 (V2) opens and valve 18 (V3) closes.
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions

12. Fig 11
Mr and Mrs J. H. Blease, London, 1955 (© Leslie Rendell-Baker, 1955).
British Journal of Anaesthesia  , DOI: ( /bja/ )
Copyright © 2000 British Journal of Anaesthesia Terms and Conditions