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 Table of Contents    
LETTER TO EDITOR
Year : 2012  |  Volume : 56  |  Issue : 2  |  Page : 201-202  

Improvised device for negative-pressure leak test


Department of Anaesthesiology and Critical Care, Mahatma Gandhi Medical College and Research Institute, Pillaiyarkuppam, Puducherry, India

Date of Web Publication17-May-2012

Correspondence Address:
Ashish Saraogi
318, Vaigai Street, Ashok Nagar, Lawspet, Puducherry - 605 008
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0019-5049.96311

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How to cite this article:
Saraogi A, Hemanth Kumar V R, Parthasarathy S, Ravishankar M. Improvised device for negative-pressure leak test. Indian J Anaesth 2012;56:201-2

How to cite this URL:
Saraogi A, Hemanth Kumar V R, Parthasarathy S, Ravishankar M. Improvised device for negative-pressure leak test. Indian J Anaesth [serial online] 2012 [cited 2019 Dec 6];56:201-2. Available from: http://www.ijaweb.org/text.asp?2012/56/2/201/96311

Sir,

Leaks in the low-pressure segment of an anaesthesia machine can affect patients by causing hypoxia, awareness and hypercarbia. [1],[2] The low-pressure segment includes the flow tubes, vaporizer manifold, vaporizers and one-way check valve on most modern anaesthesia machines. Leaks in these components are difficult to identify.

Different methods are used to check the low-pressure segment for leaks. The 1993 Food and drug administration universal negative-pressure leak test is one of them. It was named "universal" because at that time it could be used to check all anaesthesia machines, regardless of the presence or absence of check valves in the low-pressure segment. At present, most anaesthesia machines are compatible with this test. It is the most sensitive of all leak tests because it is independent of flow. It can detect leaks as small as 30 mL/min. Several mishaps have resulted from application of a wrong leak test to the anaesthesia machine. [3]

Negative-pressure leak test is performed by creating negative pressure in the low-pressure segment with a negative-pressure leak-testing device. This device is made of a suction bulb and tubing connecting suction bulb to a 15 mm adaptor, which fits the common gas outlet. [4] Suction bulb has unidirectional air outlet valve (as shown in [Figure 1]) to evacuate air from the machine side of the bulb and to create a negative pressure of 65 cm of water.
Figure 1: Improvised device

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   Anaesthesia Apparatus Checkout Recommendations, 1993 Top


Step 5. Leak Check of Machine Low-Pressure System [5] -

  1. Verify that the machine master switch and flow control valves are OFF
  2. Attach a "suction bulb" to the common (fresh) gas out
  3. Squeeze the bulb repeatedly until it is fully collapsed
  4. Verify that the bulb stays fully collapsed for at least 10 s
  5. Open one vaporizer at a time and repeat steps c and d as above
  6. Remove the suction bulb and reconnect the fresh gas hose.


Only few anaesthesia machines are supplied with a negative-pressure leak-testing device. With prolonged use, the supplied device gets damaged or lost. One improvised device is shown in [Figure 1] to perform the leak test in such situations. A simple suction bulb, used for neonatal resuscitation, is connected to the "a" end of a three-way stopcock connector and the "c" end is connected to a 15 mm adaptor by a piece of rubber tubing used in a mercury sphygmomanometer cuff. All junctions are made leak proof with adhesive.

The negative-pressure leak test with this device is performed by manipulating the three-way connector (as shown in [Figure 1]) and squeezing the suction bulb. This device generates negative pressure of more than 250 mmHg, which was tested by connecting it to a pressure transducer.{Figure 1}


   Steps Top


  1. Verify that the machine master switch and flow control valves are OFF
  2. Connector is adjusted to close "b" end and open "a-c" ends. Suction bulb is squeezed completely and device is connected to common gas outlet
  3. If bulb fills with air, connector is adjusted to close "c" end and open "a-b" ends to remove air by squeezing it
  4. With squeezed suction bulb, connector is turned to close "b" end and open "a-c" ends
  5. Steps 3 and 4 are repeated until the bulb is fully collapsed
  6. Verify that the bulb stays fully collapsed for at least 10 s
  7. Open one vaporizer at a time and repeat steps 3-6
  8. Remove the device and reconnect the fresh gas hose


This improvised device is effective. It is easy to make and cheap because the required materials are of low cost and easily available in the operation theatre.[6]

 
   References Top

1.Sompraki P, Soontranan P. Low pressure leakage in anaesthetic machines. Evaluation by positive and negative pressure tests. Anaesthesia 1996;51:461-4.  Back to cited text no. 1
    
2.Berner MS. Profound hypercapnia due to disconnect ion within an anaesthetic machine. Can J Anaesth 1987;34:622-6.  Back to cited text no. 2
[PUBMED]  [FULLTEXT]  
3.Brockwell RC, Andrews JJ. Inhaled Anesthetic Delivery Systems. In Miller RD (editor), Miller's Anaesthesia. 7 th ?ed.Philadelphia: Elsevier; 2010. p.?667-718.  Back to cited text no. 3
    
4.Dorsch JA, Dorsch SA. Equipment Checkout and Maintenance. In  ed.Philadelphia: Elsevier; 2010. p. 667-718.  Back to cited text no. 4
    
5.Dorsch JA, Dorsch SA. Equipment Checkout and Maintenance. In Understanding Anaesthesia Equipments. 5 th ed. New Delhi: Lippincott William's and Wilkins; 2008. p. 931-54.  Back to cited text no. 5
    
6.Riutort KT, Brockwell RC, Brull SJ, Andrews JJ. The Anesthesia Workstation and Delivery Systems. In: Barash PG (editor) Clinical Anesthesia. 6 th ed. New Delhi: Lippincott William's and Wilkins; 2009. p. 644-94.  Back to cited text no. 6
    


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