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Terminal gas velocity during laparoscopy
Laura W Lackey1, Douglas E Ott
1Mercer University, 1400 Coleman Avenue, Macon, GA 31207, USA.
Study Objective:
To assess the effect of port size in relation to laparoscopic gas flow and to determine the terminal velocity of gas flow during insufflation.
Design:
Analysis and mathematical modeling of gas flow characteristics.
Setting:
University biomedical engineering department.
Intervention:
Analytic calculations including Bernoulli's equation to describe gas volumetric flow and velocity as it exits laparoscopic intraabdominal entrance sites.
Measurements And Main Results:
Mathematical modeling showed that terminal velocity of gas entering the abdomen through needles or trocars reaches a practical limit depending on size and configuration of the gas exit site, amount of turbulence, length of delivery port, and gas flow. Flow rate was evaluated for circles of 2, 5, and 10 mm and annular slots of 0.1- to 0.01-mm thickness.
Conclusion:
Resistance to gas flow increases and gas exiting terminal velocity increases as the effective area of the gas exit site decreases. Depending on the configuration of variable parameters, gas flow can reach 30 m/second.