Redesign of a Safety Syringe

University of PittsburghSenior Design – BioE 1160/1161

Jessica ChechakJason Keiser

Ellsworth Weatherby

April 18, 2005

Presentation Overview

• Problem Statement• Proposed Solution

• Specific Aims• Design Considerations• Design Requirements

• Design Process• Initial Design• Final Design• Design Review • Prototype Fabrication• Functionality Testing

• Quality Systems• Manufacturability• Human Factors• Regulatory

• Economic Considerations

• Project Timeline• Group Responsibilities

• Ellsworth• Jason• Jessica

Problem Statement•There are approximately 236,000 percutaneous injuries resulting from accidental needlesticks every year

•50% of injuries occur between the time the procedure is completed and disposal of the device•20% are associated with disposal of the device

•Needlestick injuries expose health care workers to diseases caused by bloodborne pathogens

•AIDS (from HIV)•0.001 probability of contracting per needlestick

•hepatitis B (from HBV)•0.126 probability of contracting per needlestick

•hepatitis C (from HCV)•0.024 probability of contracting per needlestick

•Adoption of needles with safety features would prevent about 69,000 needlesticks each year

Proposed Solution

We propose the creation of a single use safety syringe that includes several categories of safer device features:

1.Retractable Needle

2.Sliding Sheath

3.Screw-on cap

• This novel design combines several safety features to satisfy FDA guidelines

• These engineering controls effectively reduce the risk of an exposure incident in several sites

Specific Aims

• Modify current “safety syringe” designs to increase safety to the user as well as anyone who is exposed to the syringe. • Our proposed design contains aspects of several

marketed designs, along with a few new features• Current models may have an exposed needle or a

retractable needle that can leak – both are biohazards. • The combination of a retractable needle, needle shield

and screw on cap will prevent needle-stick injury and leaking of biohazardous materials before and after use.

• The combination of safety features will ease disposal and prevent reuse.

Specific Aims

• Fabricate a sufficient number of prototypes to support Phase I functionality testing.• The design was drafted in SolidWorks • The body of the syringe was produced with a rapid-

prototyper thorough the process of Stereolithography (SLA).

• The parts were hand-assembled by the Design Coordinator using a documented process.

• Several variations of the design were prototyped to assure best fit, and to experiment with various materials

Specific Aims

• Test the Phase I prototypes, in vitro, to demonstrate basic functionality.• The research team used an in vitro testing

apparatus to test the syringes. • Tests will show that the prototype successfully

meets the functionality standards set forth by the team: • no leakage pre-use or post use• successful fluid delivery• a retractable needle

• FDA Guidelines• 29 CFR part 1910.1030, The Bloodborne Pathogens

Standard• Enforced by OSHA through citations and fines

• Injuries Statistics• 236,000 needlesticks/year• Every year about 1.3 million people die of blood infections caused

by the re-use of syringes

• Consequences of needlesticks• Disease transmission• Post-exposure prophylaxis ~ $500-$1,000 per injury• 1.7 million workers needed time off to recuperate after

incidents

Initial Design Considerations

Safety Syringe Design Requirements

Our design goals were to achieve every FDA recommended design feature characteristic of a safer device:

Provide a barrier between the operator's hands and the needle after useWill allow the operator's hands to remain behind the needle at all timesBe an integral component of the device, and not an accessoryProvide protection before, during and after use and after disposalBe simple and self-evident to all operators and require little training and no particular expertise

Design Process: Initial Design

• The initial design utilized a push button to retract the protective shield. • This facet was redesigned to

reduce the complexity of the design and to reduce the cost of mass manufacturing.

• The retractable needle mechanism was initially activated when the plunger reached the bottom of the syringe body.• This was modified to make the

retractable needle mechanism user activated.

• Initially the syringe was intended to be pre-filled; this modification allowed the syringe to be sold unfilled.

Design Mid-December

Design Process: Final Design

• The protective shield was designed to allow the user to slide it up and down the syringe body without having to compress a button, thus simplifying the device.

• The retractable needle is activated by a spring loaded mechanism located in the luer of the needle. • This system is triggered by a 5lb

downward force on the plunger by the user after the medication has been delivered.

• The protective cap remains locked into position before and after use until a force of 1lb is applied.

Final Design: Before Use

Final Design: Intended Use

Before UseReady To

Inject

Ready ForDisposalAfter Use

Design ReviewSyringe Body

Are the dimensions in mm? Yes

Does the body fit into the protective shield? Yes

Does the syringe body have a 9mm opening for the plunger?

Yes

Does the syringe body bottom opening have a luer thread pattern comforming with ISO 594-1:1986 "Female Fittings"?

Yes

Does the body have an opening to lock-in the push button mechanism?

Yes

Protective Shield

Are the dimensions in mm? Yes

Does the protective shield fit over the syringe body?

Yes

Does the shield have a luer thread pattern on the ouside end conforming to ISO 594-2:1998 "Male Fittings"?

Yes

Does the shield have a square pattern on the top for use with the push button?

Yes

Does the luer threading and shield fit into the Protective Cap?

Yes

Protective Cap

Are the dimensions in mm? Yes

Does the Cap have a luer thread pattern on the inside conforming to ISO 594-1:1986 "Female Fittings?“

Yes

Does the luer threading and cap fit onto the protective shield?

Yes

Backing Pad

Are the dimensions in mm? Yes

Does the backing pad fit against the back of the protective shield?

Yes

After all questions were answered “Yes” prototyping began.

Prototype Fabrication

• The prototype was produced by quickparts.com• Solidworks files of the design were used • Stereolithography (SLA) rapid prototyping was used

to produce the parts• The initial prototypes were made of Somos® 14120 (a

low viscosity photopolymer – white color)• Issues with tolerances and angle of threads

• A second set of prototypes was made also using Somos® 14120

• Parts were assembled, fit was good, but thread angle needed to be changed

• A final set of prototypes was made of Somos® 11120 (a low viscosity photopolymer – clear color)

• New material had different tolerances, but we were able to combine parts to produce the final prototypes

Prototype: Intended Use

Before UseReady To Inject

Ready For DisposalAfter Use

Comparison to Current Syringes:Before and After Use

Before Use After Use

Our HybridSafety Syringe

Protective ShieldSafety Syringe

Retractable NeedleSafety Syringe

Normal Syringe(Non-Safety)

Functionality Testing

• Functionality testing was performed to demonstrate that the syringe met the standards for success:

• No leakage pre-use or post use• Successful fluid delivery• A retractable needle• Operational needle shield• Operational screw-on cap

Quality Systems Considerations

Manufacturability• Simple Design

• Needle is surgical grade stainless steel (standard size 23 gauge)

• Plastic components will be made from PTFE and polypropylene

• Rapid Injection Molding will be used for production of plastic components

Human factors• Ease of use• Biocompatability of components• Non-Allergenic components• Easily disposable – Biohazard safe

Regulatory• 29 CFR 1910.1830 - Bloodborne Pathogen

standard• The Occupational Safety and Health

Administration (OSHA) promulgates a standard to reduce occupational exposure to bloodborne pathogens through a combination of:

• Engineering controls• Work practice controls

• Enforcement Procedures • Show evidence of adoption of devices/engineering

controls that reduce exposure • Document plan annually and any difficulties • Inspections: complaints & some scheduled inspections • OSHA does not require a specific device

Quality Systems Considerations

• Regulatory (cont.)• The Needlestick Safety and Prevention Act

• Directed OSHA to revise the bloodborne pathogen standard:

• New definitions in engineering controls • Sharps with engineering sharps injury protection• Needless systems

• Annual review/update of exposure control plan• Employers are required to select safer needle devices as

they become available• Involve frontline workers in device selection

• maintain detailed sharps injury log

• The Centers for Disease Control and Prevention estimated in March 2000 that selecting safer medical devices could prevent from 62 to 88 percent of sharps injuries in hospital settings.

Quality Systems Considerations

Economic ConsiderationsCost of Safety devices:

• 1 to 3.5 times more than conventional devices• The increased purchase costs of using needles with safety

features would be between $70 million and $352 million per year.

Cost of Post-Exposure Prophylaxis: • $500 low; $1,500 moderate; $2,500 high risk • Eliminating 69,000 needlesticks per year would reduce post-

exposure treatment costs for by between $37million and $173 million per year.

Market size• 550M per year (US hospital patients)

Frost & Sullivan (www.chetday.com/medmistakes.html)

Distribution• Hospitals, Individuals

Cost Effectiveness of Safety Devices

Cost of safety devices are offset by cost of post-exposure prophylaxis and follow up in medium

and high-risk scenarios

Projected Project Timeline

This is our initial project timeline.

We remained on schedule within a day or two of our initial project deadlines. We received our initial

prototype earlier than expected. This gave us time for several redesigns to produce the final prototype.

Group Responsibilities

• Ellsworth: Business Manager / Safety Coordinator

• Jason: Design Coordinator

• Jessica: Project Coordinator

Ellsworth’s Achievements

• Business Manager• Research on Market Size… etc.• Creation of final PowerPoint presentation• Updating controlled documents

• Safety Coordinator• Research on OSHA standards for “Safe

Sharps”

• Writing Section B of the SBIR Phase I Application

• Design Coordinator:• Modeling of design in Solidworks• Design modifications• Design Review• Prototyping• Functionality Testing• Writing Section D of the SBIR Phase I

Application

Jason’s Achievements

• Project Coordinator• Scheduling Team meetings• Creation of final PowerPoint presentation• Writing Sections A and C of the SBIR Phase I

Application• A: Specific Aims• C: Relevant Experience / Preliminary Work / Design

Review

• Editing the SBIR Phase I Application• Updating Controlled Documents

Jessica’s Achievements

Any Questions?

Hypodermic syringes with “Needle-Sheath” safety feature

• Active Safety Feature

A feature that requires the operator to activate the safety mechanism, and failure to do so leaves the operator unprotected “Needle-sheath” syringe

Hypodermic syringes with “Retractable Technology” safety feature

• Passive Safety FeatureA safety feature that remains in effect before, during and after use, the operator does not need to "activate" the safety feature

• Integrated Safety Design

The device has the safety feature included into its design and it can not be removed or inactivated. This is the preferred safety feature.

Retractable needle safety syringe