Well,it doesn't depend on pressure only but on the size of the suction catheter in french you are choosing, and the endotracheal tube size as well .

Thanks Aboud,

Yes this is true suctioning safely involves several aspects . Catheter to ET tube ratio, depth of suctioning and time, as well as pressure setting.

However a size 14 French (4.7 mm OD) catheter will suction 56 liters per minute toward an occlusion pressure of 70 kPa (525 mm Hg) whereas when regulated to    16 kPa or 120 mm Hg a flow of 20 litres per minute will be seen through that same catheter toward  occlusion pressure. An occlusion pressure of 48 kPa (365 mm Hg) will  draw a reported 40 liters per minute through a size 14 Fr suction catheter.

As the catheter is inserted further into the quickly narrowing airways negative pressure distal to the catheter will increase (become more negative) as resistance to return flow increases. Particularly with open suction. Should airway collapse occur, then the set suction pressure will be transmitted directly to the tissues beyond I suspect.

Interestingly, any negative pressure within the airways below - 40 mm Hg will cause negative pressure pulmonary oedema with the maximum negative pressure that an average human can develop against an occluded airway being about 80 mm Hg. as in choking or strangulation.

But this is not the question.  guidelines have existed for many years now recommending (sensibly) a requirement to take care with the amount of vacuum used and yet this does not always happen. Questions of a safety, legal and ethical nature may arise when a known risk is not taken into account when performing a procedure as seemingly straightforward as ET suctioning.  To what extent practice does or should follow "best practice" or "evidence based "practice guides is yet  to be examined.

>David Arbon> I agree with you. 

But the concept of (a known risk is not taken into account) is not restricted to this procedure only, but may be expanded to include many other entities.

One of the major ones in developing countries, is unavailability of the safer, more suitable alternative/s.

I reviewed many articles regarding recommended pressure..... mostly 80 m Hg to 120 mmHg is seen in literature.

Thank you Elsayed Abdelkreem. What you say is true.

I am always impressed with the enthusiasm and interest from people in the developing world who with the aid of global information sharing seek to improve outcomes. Usually they will know and acknowledge  this issue in their work and can adapt to minimize risk.

Actually changing practice can be quite another issue, even in the "Developed" world.

Sheela Durai, Thank you for your interest and information. 

David Arbon, thank you for the response. Could you share the sources of evidence which recommend negative pressures other than 80 mm Hg to120 mmHg?

I would be grateful if you could.

In Answer to your request  Sheela Durai.

Thank you for your interest and yes it is now common to read that suction pressure, occluded pressure, should not be set at more than 150mm of Hg (20kPa).  It is tempting for operators to feel that more is better without fully understanding the consequences. More suction may create more secretions therefore more suction is required, if you like, and the process can be self perpetuating.

An "archaeology"  (after Foucault) of setting of different suction pressures appears as Appendix 5 of my Systematic Review.

https://digital.library.adelaide.edu.au/dspace/handle/2440/71485

 I suspect this is why surveys of the practice have been inclined to see more than the recommended suction pressure being used. Of course in some areas the suction regulator is simply not available due to cost constraints and researchers have described only being able to use some 350 mm Hg to study suctioning effects ;  ( Celic, S S and Elbas, N O, The Standard of Suction for patients undergoing endotracheal intubation. Intensive Crit Care Nurs 16, 191-198(2000).

There are other issues, such as the way in which the suction is developed. Whether it is created by a venturi control from an air or oxygen source or from an electrical stand alone suction machine or as at a large facility a central suction source piped to various wall outlets. Kevin Klosec at Boehringer in the US has written on this and the makers of OHIO Suction Regulators have some good educational material  working with  Patricia Carroll.

( Carroll PL; The principle of Vacuum and its use in the Hospital Environment. 2006 Monograph.)

 A low flow suction regulator is suitable for naso-gastic or underwater seal drain suction but a high flow regulator is needed for endotracheal suctioning as it is the flow that will sweep the secretions into the catheter and into the drainage receptacle.  The idea is to maximize the flow and minimize risk on high negative intra-pleural pressures and catheter induced trauma.

As for recommendations for settings above 120mm Hg, here are some recent references but, as you have observed yourself, you will be hard pressed in 2015 to see someone recommending anything over 200 mm Hg . This could be a typo and perhaps they mean 200 cm H2O . That has been done not so long ago by a fairly prestigious journal but corrected quickly.

 Nevertheless, The Chief Medical Officer for South Australia has, only this year, written to me to say that I am not to be concerned that Government Intensive Care Units in SA use 550 to 600 mm Hg (70 to 80 kPa) to perform endotracheal suction. Much to my chagrin.

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Recent papers;

150 mm Hg

Differential Effects of Endotracheal Suctioning on Gas Exchanges in Patients with Acute Respiratory Failure under Pressure-Controlled and Volume-Controlled Ventilation

Xiao-Wei Liu,1 Yan Jin,1 Tao Ma,1 Bo Qu,2 and Zhi Liu1

BioMed Research International  Volume 2015 (2015), Article ID 941081, 6 pages

http://dx.doi.org/10.1155/2015/941081

http://www.hindawi.com/journals/bmri/2015/941081/

150 to 200 mmHg

Comparing the effect of open and closed endotracheal suctioning on pain and oxygenation in post CABG patients under mechanical ventilation

Ali Mohammadpour1 , Shahram Amini2 , Mohammad Taghi Shakeri3 , Sahereh Mirzaei ;    

Iranian Journal of Nursing and Midwifery Research | March-April 2015 | Vol. 20 | Issue 2     

file:///C:/Users/David/Downloads/1168-2090-1-PB.pdf

100 mm Hg and 200mm Hg

Comparing two levels of closed system suction pressure in ICU patients: Evaluating the relative safety of higher values of suction pressure

Ahmad R. Yazdannik, Somayeh Haghighat, Mahmoud Saghaei1, Maryam Eghbali2

Iranian Journal of Nursing and Midwifery Research | March-April 2013 | Vol. 18 | Issue 2

Hope this is useful

I am afraid I might have to team up with an engineer to write a paper about the physics of flow through a tube and it's relevance to such human interventions.

Yours

David Arbon.

Aleydis July Peterson. Colombia Valledupar

It is not my area, but if the subject of my interest.

Suction device placed at a maximum suction pressure ranging from 20-50 mmHg, depending on the size of the patient and you want exert pressure nurse / a performing art.

It is advisable hyperoxygenate 30 seconds before inserting the probe of suction, usually hyperoxygenate 50% of schedule as FiO 2, that is, if a patient is pre with a FiO2 of 0.4, it is up to 0, 8. Hyperoxygenation down completely finish the minute suction technique, then gradually lowers hyperoxygenation

Chapter 71: Aspiration of secretions through tubes endotraquealeshttp: //www.eccpn.aibarra.org/temario/seccion5/capitulo71/capitulo71.htm. Spain. [Accessed 12 October 2015].

Thank you Aleydis ,

Sounds reasonable.

An interesting chapter regarding suction in the neo natal /pediatric environment. Not sure about saline these days but thank you for sharing this.

David.

I bring a different approach to the real issue here: clearing secretions effectively without damaging the mucosa or generating barotrauma to the lung parenchyma. I perform bronchoalveolar lavage on a regular basis for various indications. It is often in the context of ICU care and mechanical ventilation with or without orotracheal intubation. When fluid is instilled ahead of aspiration, the potential for mucosal injury when the catheter is above the segmental bronchi is very low. The effective vacuum from the large bore bronchoscopes (T180 or T-190 Olympus Bronchoscopes) is great for evacuating secretions. If you irrigate ahead of the process, your ability to clear the mucous is vastly improved. I think this is a key issue in gentle clearance. Another is to avoid impacting your scope into the segmental bronchi without allowing the inflow of air from beyond your scope. Bleeding is the common result when this happens along with barotrauma petechia. 

Catheters with twin ports at the tip are also safer because they cannot engage a spot on the mucosal as long as the tip is not buried within one of the segmental or sub segmental bronchi. There, the pull vacuum is applied and bleeding is invariably the result. 

Thanks Paul

Our P160s have a 2mm suction / instrument channel if I recall and the T 180 has 3mm ?  About the same as a 10 (3.3mm OD) or 12(4mmOD) French catheter in aspiration power do you think?

How much driving force do you use /Vacuum? If I may ask.

I just did to BAL's at bedside this AM and tried to quantify this. It seems variable even on the regulator. I set it to maximum to remove the secretions effectively because I avoid sealing the orifice of the bronchus with the tip of the scope. 

I'll try to get the actual number and get back with you.

p