Research Papers

Design, Manufacture, and Testing of the Easycuff™ Pressure Measuring Syringe

[+] Author and Article Information
Alexander H. Slocum, Samuel C. Duffley, Jaime M. Gamazo, Adrienne Watral

Department of Mechanical Engineering,  Massachusetts Institute of Technology, Cambridge, MA 02139

Joan E. Spiegel

Department of Anesthesiology,  Beth Israel Deaconess Medical Center, Boston, MA 02215

J. Med. Devices 6(3), 031008 (Aug 20, 2012) (7 pages) doi:10.1115/1.4007250 History: Received April 30, 2011; Revised March 13, 2012; Published August 20, 2012; Online August 20, 2012

A pressure measuring syringe, known as the EasyCuff™, has been designed and manufactured to provide physicians with a tool to accurately measure the pressure inside the distal cuff of endotracheal tube tubes (ETTs). The syringe, identical in size to a standard 10 cc syringe, has four components: a seal, a plunger, a barrel, and a silicone-rubber bellows (the pressure measuring component). A finite-element model of the bellows was created using ADINA™; silicone rubber bellows were then produced and shown to correlate linearly with the model to within ±5% up to a load equivalent to an internal pressure of 200 cm H2 O. 20 of these bellows were then assembled into EasyCuff™ syringes and tested to assess their accuracy and repeatability. The experimental setup used a currently-available manometer, which the EasyCuff™ is designed to replace, as a reference tool. The data show that the relationship between measured pressure and bellows deflection is linear, with a correlation factor of R2  = 0.99; additionally, environmental testing showed that the EasyCuff™ is unaffected by temperature cycling between −15 °F and +170 °F.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Schematic diagram of endotracheal intubation showing an endotracheal tube, inserted into the trachea, and the cuff which the EasyCuff™ is used to inflate

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Figure 2

The EasyCuff™ pressure measuring syringe

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Figure 3

(a) Cuff pressure indicator; (b) Posey Cufflator® (www.posey.com); (c) Rusch EndoTest® (www.rusch.com)

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Figure 4

Bellows design concept with two seals (top) and a single seal (bottom); areas of hatched lines illustrate regions where the pressure is the same

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Figure 5

Alpha prototype pressure-measuring syringe with silicone-rubber bellows

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Figure 6

Free body diagram of bellows

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Figure 7

(a) Adina™ mesh of final convolution geometry; (b) mesh of [1/2] bellows

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Figure 8

Stress distribution for 20 mm Hg applied pressure. One quarter of the circular section can be seen, as implemented by ADINA™. Stress is indicated in Pa.

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Figure 9

Results of FEA showing vertical displacement (mm) versus pressure (mm Hg) as being linear for the bellows

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Figure 10

Plot of load versus deflection for the simulation (solid line) as well as two tests; slow (pink, or dark) and fast (yellow, or light)

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Figure 11

Experimental setup, with a cuff-pressure indicator (Simms-Portex, Keene, NH), used to measure the repeatability of 25 EasyCuff™ samples [20]

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Figure 12

Repeatability of 25 EasyCuff™ samples [(20),21]

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Figure 13

Testing 20 randomly selected bellows from multiple manufacturing batches. There are 30 data points on each plot, representing 10 cycles of 0–10, 0–20, and 0–30 cm H2 O.

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Figure 14

Testing ten randomly selected bellows after performing drop tests and temperature cycling. The same cycling from 0–10, 0–20, and 0–30 was performed for these EasyCuff™ samples.

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Figure 15

Summary of results of environmental testing showing the 10 random samples pre- and postenvironmental testing, as well as the lot of 20 pre-environmental testing. CPI pressure is shown as a reference.




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