Dear Editors:Laparoscopic surgery has advantages over open surgery for several abdominal conditions due to
improved short-term outcomes.[1] Performing laparoscopic surgery in many low and middle-income country (LMIC) settings
is restricted by the lack of general anaesthesia (GA) and carbon dioxide (CO2)
insufflation. Gasless laparoscopic surgery employs the use of a mechanical anterior abdominal
wall lift device to create internal space within the abdomen. This negates the need for GA and
CO2 which may help increase adoption of laparoscopic surgery in LMIC settings.[2]The safety and efficacy of gasless techniques appear to be non-inferior when compared to
conventional laparoscopic surgery for many gastrointestinal and gynaecological conditions.[3] However, concerns from surgeons before adopting this technique are operative field of
view and safety concerns including damage to the abdominal wall during the lift.[3] Many lift devices produce a tenting effect, creating an angular cavity that can
restrict view.[3] Monitoring to ensure a ‘safe’ force is applied is also essential, as lifting the
abdominal wall carries the potential for trauma if too much force is applied.[4] Our aim was to develop methods that may be used in future clinical studies aimed at
mitigating these concerns by assessing field of view and force exerted on tissues during
gasless lift procedures.Firstly, we developed a novel mechanical force sensor and integrated this into a lift device.
The sensor indicated the magnitude and estimated ‘safety’ of the vertical load applied to the
wall during lifting. Using a frugal design approach, we developed a ‘spring-balance’ system
which provides a robust low-cost mechanism that can be readily manufactured and maintained in
LMICs (Figure 1). The gauge consists
of a spring housed within 2 concentric tubes, combined with a calibrated colour scale on the
outside of the inner tube to inform the user of the load being applied. The sensor was
calibrated to display Green (Force = 0-130N), Yellow (Force = 130-150N), and Red (Force =
150-170N). These values align with literature values for acceptable force ranges exerted
during conventional laparoscopic surgery.[5] The sensor can be readily integrated into a low-cost lift system and would be ideal
during training to provide the user with objective visual feedback on loading.
Figure 1.
3D scanning technology and a novel mechanical force sensor can be used to evaluate
field of view and safe lift forces during gasless laparoscopic experiments.
3D scanning technology and a novel mechanical force sensor can be used to evaluate
field of view and safe lift forces during gasless laparoscopic experiments.Secondly, we conducted an experiment using a single human cadaver. The purpose of this was to
assess the field of view via 3 dimensional (3D) abdominal wall surface scanning and volumetric
analysis. Intra-abdominal volume created via the techniques was used as the proxy for field of
view. Paper reference markers were sutured to the abdominal surface to aid registration during
the surface scanning that was carried out using a commercially available 3D laser scanner
(Artec Space Spider, Artec 3D). The associated scans were processed using a bespoke software
package (Artec Studio 12, Artec 3D) and the resultant surfaces of the cadaveric abdominal wall
were analysed to obtain cross-sectional data using an open source 3D mesh analysis software
(CloudCompare). The headroom profile and abdominal wall shape created by conventional
laparoscopic surgery at 12 mmHg and gasless lift were compared (Figure 1). While some ‘tenting’ effects are apparent,
similar volumes were achieved by gasless techniques as compared to insufflation. Further
validation as to the impact of field of view in clinical studies is required.Our results demonstrate the use of the 3D surface scanning technology and the novel
mechanical force sensor are suitable methods to evaluate field of view and force applied to
the abdominal wall. These methods have relevance to support further evaluation of gasless
surgery techniques in clinical trials with living patients.
Dissemination Declaration
The results will be disseminated on social media platforms and reports back to funders.
Author Contributions
William S. Bolton, Peter R. Culmer, Jesudian Gnanaraj and David G. Jayne conceptualised the
study. William S. Bolton, Noel K. Aruparayil, Joshua R. Burke and William R. Kitchen
arranged the cadaveric assessments. Manish Chauhan, Kevin J. N. Gnanaraj, Alice M. Benton,
and Sophie E. Hutchinson led the development of the mechanical force sensor and conducted
volumetric analysis. William S. Bolton prepared the first draft of the manuscript which was
subsequently edited by all authors. David G. Jayne is the study guarantor.Study concept and design: William S. Bolton, Peter R. Culmer, Jesudian Gnanaraj, and David
G. JayneAcquisition of data: William S. Bolton, Noel K. Aruparayil, Joshua R. Burke, and William R.
KitchenAnalysis and interpretation: Manish Chauhan, Kevin J. N. Gnanaraj, Alice M. Benton, and
Sophie E. HutchinsonStudy supervision: David G. Jayne and Peter R. Culmer
Figure 1.