1 jkf - Actiflow · 2019. 9. 10. · •xb 1 jkf Airflow simulations of the OR - design principles...

Transcript of 1 jkf - Actiflow · 2019. 9. 10. · •xb 1 jkf Airflow simulations of the OR - design principles...

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Airflow simulations of the OR - design principles and fairytales NVMM symposium, 28-03-2018

ir. M.G.M. (Mike) van der HeijdenTel: +31 (0)76 542 2220©2018 Actiflow BV
Disclosure of speaker’s interests

(Potential) conflict of interest None / see below

Potentially relevant company relationships in

connection with event Actiflow BV

Sponserships None

Fee or other (financial) payment Actiflow BV

Shareholder None

Other relationship, i.e. None
Table of Contents

1) Introduction Actiflow

2) Scope & Objective

3) Design & Assessment methods

a) Design methods

b) VCCN RL7 & WIP guideline

c) Summary of methods

4) CFD Simulations

5) Simulation resultsa) Impact of ‘at rest’ vs ‘in operation’

b) Role for CFD in selection of systems & design changes?

6) General remarks and conclusions
Table of Contents




a) Design methods



4) CFD Simulations



Introduction Actiflow1
Table of Contents




a) Design methods



4) CFD Simulations



The design process of an operating theatre is mainly based on simplified design principles and in situ (‘at rest’) cleanliness measurements after completion. This presentation will focus on general airflow patterns and cleanliness ‘at operation’.

Scope & Objective2

Factors that influence cleanliness:- Location of OR table;- Location of surgical team;- Temperature of supplied clean air;- Type & shape of surgical light;- Location of surgical light;- Amount of people in OR;- Clothing system of surgical team;- Cleanliness path towards OR;- Cleaning of the OR;- Cleanroom protocols & procedures;- Gowning procedures;- Opening of doors; - Location of instrumentals and tables;- Maintenance of HVAC system;- Financial pressure- …

Postoperativeinfection

Air based contamination

CFUs in air

Direct to woundTo instrument-table

Source: Original image of P. van den Broek

Scope & Objective2



CFUs in air


Scope of this presentationFactors that influence cleanliness:- Location of OR table;- Location of surgical team;- Temperature of supplied clean air;- Type & shape of surgical light;- Location of surgical light;- Amount of people in OR;- Clothing system of surgical team;- Cleanliness path towards OR;- Cleaning of the OR;- Cleanroom protocols & procedures;- Gowning procedures;- Opening of doors; - Location of instrumentals and tables;- Maintenance of HVAC system;- Financial pressure- … Source: Original image of P. van den Broek

Scope & Objective2



CFUs in air


Scope of this presentationObjective with regard to airflow:- Identification of current OR design principles;- Assessment method of a OR when built;- Show difference in flow patterns with ‘at rest’ vs ‘in

operation’ conditions;- Show potential for CFD when selecting

different systems;

Source: Original image of P. van den Broek
Table of Contents




a) Design methods



4) CFD Simulations



Design & Assessment methods3

A very basic calculation method focusses on the people as the main contamination source, were under fully mixed conditions the steady state average CFU concentration can be estimated (max of 10 CFU/m3).

C [CFU/m3] n ∙ p [CFU/s] ɸ [m3/s]

2.96 2 ∙ 3⅓ 0.25 ms-1 x 9m2

5.92 4 ∙ 3⅓ 0.25 ms-1 x 9m2

8.89 6 ∙ 3⅓ 0.25 ms-1 x 9m2

11.85 8 ∙ 3⅓ 0.25 ms-1 x 9m2
Design & Assessment methods3

C [CFU/m3] n ∙ p [CFU/s] ɸ [m3/s]

2.96 2 ∙ 3⅓ 0.25 ms-1 x 9m2

5.92 4 ∙ 3⅓ 0.25 ms-1 x 9m2

8.89 6 ∙ 3⅓ 0.25 ms-1 x 9m2

11.85 8 ∙ 3⅓ 0.25 ms-1 x 9m2

A very basic calculation method focusses on the people as the main contamination source, were under fully mixed conditions the steady state average CFU concentration can be estimated (max of 10 CFU/m3).
Table of Contents




a) Design methods



4) CFD Simulations



A gentle reminder of the Dutch method for testing and classification of operating theatres (with performance level 1):

- Objective A, protection for contamination from periphery;

- Objective B, quick recovery ;

- Testing and classification ‘at rest’;

- Highly recommended to take OR lights into account;

- Bases of code is in line with codes from Germany, UK, Sweden,

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(not necessary in original version 2014, now recommended, likely mandatory

in next revision in 2019)

(fixed equipment present without taking into account persons and non-fixed

medical equipment. Including the latter would be testing ‘in operation’)

(ISO 5 in protected area, ISO 7 in periphery, protected area level 2 to 3, meaning

that cleanliness of protected area is a factor 100 to 1.000 of periphery (logarithmic)

(In case of a contamination in the protected area dilution of by a factor 100 should

occur within 3 minutes)

(differences do exist e.g. in recommended ISO levels for mixing systems ‘at

rest’, also additional requirements on minimal air change rates may be present)

France, Switzerland for UDF systems;

Dutch WIP & VCCN RL7 guidelines (after completion of OR)






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BGx = Protection level at location x [-]Cx = Particle concentration at x [#/m

3]Cref = Concentration in periphery [#/m

3]

source: RL7 VCCN 2017







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BGx = Protection level at location x [-]Cx = Particle concentration at x [#/m

3]Cref = Concentration in periphery [#/m

3]


t0,01 = recovery time [min]t100n = time for recovery factor 100 [min]tn = start time for recovery [min]


emission

Measurement 1:100







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‘Open’-variant ‘Closed’-variant ‘Semi open’-variant











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‘Open’-variant ‘Closed’-variant ‘Semi open’-variant











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France, Switzerland for UDF systems; (differences do exist e.g. in recommended ISO levels for mixing systems ‘at




van der Heijden et al. (2009)







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rest’, also additional requirements on minimal air change rates may be present) van der Heijden et al. (2009)









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Summary of methods3

There is a substantial difference between design calculations and the quality assessment measurement when built.

Differences exist in for instance:

a) Design calculation ‘in operation’;b) Assessment when built ‘at rest’;

a) Design calculation PI = CFU concentration;b) Assessment PI = protected area or recovery time;

a) Design calculation airflow patterns not taken into account;b) Assessment specific airflow is taken into account;
Summary of methods3

There is a substantial difference between design calculations and the quality assessment measurement when built.

Differences exist in for instance:

a) Design calculation ‘in operation’;b) Assessment when built ‘at rest’;

a) Design calculation PI = CFU concentration;b) Assessment PI = protected area or recovery time;

a) Design calculation airflow patterns not taken into account;b) Assessment specific airflow is taken into account;
Table of Contents




a) Design methods



4) CFD Simulations



From the information provided up to this point it has become clear that there might be a need for a design- and assessment method which are more coherent to each other. In order to show the impact of ‘at rest’ vs ‘in operation’ conditions Computational Fluid Dynamics (CFD) is used to assess the protected area under different conditions.

CFD simulations4

Reference case- Dimensions 7.5m x 7.5m x 2.8m;- Plenum 3m x 3m;- 8 returns in walls;- 5 people + patient;- Plenum inlet velocity 0.25 m/s;- Localized heatload per persons (Sens 80W);- Heatload of Lights (100W per light)- Operating table with patient;- Instrument tables (4x);

Simulation settings- Number of cells 4.066.941 [-];- OpenFOAM solver (buoyantBoussinesq)- Mesh made with ANSA- 5 prims layers (y+ checked)- Non orthogonality mesh check and quality control

7.5m

7.5m

2.8m

ɸ [m3/s]

CFD simulations4



CFD simulations4



CFD simulations4



CFD simulations4


CFD simulations4

From the information provided up to thispoint it has become clear that there mightbe a need for a design- and assessmentmethod which are more coherent to eachother. In order to show the impact of ‘atrest’ vs ‘in operation’ conditionsComputational Fluid Dynamics (CFD) isused to assess the protected area underdifferent conditions.
CFD simulations4

CFD simulations4

In order to visualize the impact of equipment and persons on the airflow patterns in an operating theatre, the following situations are addressed by computational fluid dynamics.

First session:

- Situation A = airflow patterns with only patient in OR;

- Situation B = situation A + heatload;

- Situation C = situation B + surgeon;

- Situation D = situation C + instrumentalist;

- Situation E = situation D + OR Lights;

- Situation F = situation D + two persons;

- Situation G = situation F + 4 x tables and anaesthetist

Second session:

- Impact of shape OR lights;

- Impact of location OR lights;

- Type of system;

Outline of simulations4

First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;


First session:








Second session:



- Type of system;

Table of Contents




a) Design methods



4) CFD Simulations


b) Role for CFD in selection of system & changes?

Results - ‘at rest’ vs ‘in operation’5Included in model:

- UDF Plenum;

- Eight returns;

- Patient without heat-source;
Included in model:

- UDF Plenum;

- Eight returns;


Results - ‘at rest’ vs ‘in operation’5
Included in model:

- UDF Plenum;

- Eight returns;

- Patient with heat-source;

Included in model:

- UDF Plenum;

- Eight returns;


- Surgeon with heat-source;

Included in model:

- UDF Plenum;

- Eight returns;


- Two surgeons with heat-source;

Included in model:

- UDF Plenum;

- Eight returns;


- Two surgeons with heat-source;- Two Lights (RL7 position);

Included in model:

- UDF Plenum;

- Eight returns;


- Four surgeons with heat-source;- Two lights (RL7 position);

Included in model:

- UDF Plenum;

- Eight returns;


- Four surgeons with heat-source;- Two lights with heat-source (RL7 position);

- Anaesthetist with heat-source;

- Instrument tables (4x)

Included in model:

- UDF Plenum;

- Eight returns;


--

-

-

Included in model:

- UDF Plenum;

- Eight returns;


--

-

-


1:100 periphery concentration
Included in model:

- UDF Plenum;

- Eight returns;


--

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-

Included in model:

- UDF Plenum;

- Eight returns;


- One surgeon with heat-source;-

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-

Included in model:

- UDF Plenum;

- Eight returns;


- Two surgeons with heat-source;-

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-

Included in model:

- UDF Plenum;

- Eight returns;


- Two surgeons with heat-source;- Two lights (RL7 position);

-

-

Included in model:

- UDF Plenum;

- Eight returns;



-

-

Included in model:

- UDF Plenum;

- Eight returns;






- UDF Plenum;

- Eight returns;


- Four surgeons with heat-source;- Two lights with heat-source (RL7

position);

- Anaesthetist with heat-source;- Instrument tables (4x)

- UDF Plenum;

- Eight returns;


- Four surgeons with heat-source;- Two lights with heat-source (RL7

position);

- Anaesthetist with heat-source;- Instrument tables (4x)

- UDF Plenum;

- Eight returns;

Summery of first-results5

Based on a comparison for a 1T plenum between ‘at rest’ and ‘in operation’ conditions, there are indications that:

1) The dimension and shape of the protected area (level 2) in the operating theatre is dependent of the location of people and equipment;

2) Location of lights and tables does have a significant influence;

3) There are indications that the protected area can increase by instrument tables etc., however this extended area might become less stable.

‘at rest’ without lights ‘in operation’ with lights
Summery of first-results5

Based on a comparison for a 1T plenum between ‘at rest’ and ‘in operation’ conditions, there are indications that:

1) The dimension and scape of the protected area (level 2) in the operating theatre is dependent of the location of people and equipment;

2) Location of lights and tables does have a significant influence;

3) There are indications that the protected area can increase by instrument tables etc., however this extended area might become less stable.

‘at rest’ without lights ‘in operation’ with lights
Table of Contents




a) Design methods



4) CFD Simulations



Included in model:

- UDF Plenum;

- Eight returns;





Results - impact of OR lights5

Semi-openSmallWider location realistic


Semi-openOR lights

SmallOR lights
Results - impact of different systems5

2TPlenum

Supply inPeriphery
Results - impact of different systems5

2TPlenum

Supply inPeriphery
Table of Contents




a) Design methods



4) CFD Simulations



General remarks and conclusions6

1) There is a strong indication that the airflow patterns under ‘at rest’ vs ‘in operation’ - conditions differ substantially from each other;

2) In line with current guidelines it has been found that the shape and location of the lights has a substantial impact;

3) Computational fluid dynamics might breach the gap between the design phase and calibration &testing when built.

The results shown in this presentation lead to the following conclusions:
General remarks and conclusions6The results shown in this presentation lead to the following conclusions:

Future outline – Determination of CFU concentration with persons as contamination source in CFD

Neck as CFU source

Design based on ‘in operation’ - conditions & CFU concentration

1) There is a strong indication that the airflow patterns under ‘at rest’ vs ‘in operation’ - conditions differ substantially from each other;

2) In line with current guidelines it has been found that the shape and location of the lights has a substantial impact;

3) Computational fluid dynamics might breach the gap between the design phase and calibration &testing when built.
General remark

The objective of this study was to identify the difference in airflow between ‘at rest’ vs ‘in operation’. The results show that the airflow pattern is influenced significantly by people, lights and e.g. instrument tables. The results aren’t meant to show the advantage or disadvantage of a certain system nor the preference for a certain type of system. Moreover, the results are mainly valet for this reference case, additional research is necessary for more generic conclusions about specific airflow patterns under different circumstances and dimensions of the operating room. In conclusion, in this presentation the difference in airflow patterns is shown between ‘at rest’ vs ‘in operation’, for any other conclusions additional research is necessary.
ir. M.G.M. (Mike) van der HeijdenBouwfysisch & FSE adviseurTel: +31 (0)76 5422 220Actiflow B.V.

1 jkf - Actiflow · 2019. 9. 10. · •xb 1 jkf Airflow simulations of the OR - design principles...

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Transcript of 1 jkf - Actiflow · 2019. 9. 10. · •xb 1 jkf Airflow simulations of the OR - design principles...