Compressed air injection technique to standardize block injection pressures.

Area of Science:

• Anesthesiology
• Regional Anesthesia
• Medical Devices

Background:

• Standardized methods for monitoring injection pressures during peripheral nerve blocks are lacking.
• High injection pressures are associated with clinically significant nerve injury.

Purpose of the Study:

• To evaluate a compressed air injection technique for maintaining pressures below the nerve injury threshold.
• To assess the feasibility of using Boyle's law and standard regional anesthesia equipment for pressure monitoring.

Main Methods:

• An in vitro model using syringes (20 and 30 mL) and various needles (18G-24G) was employed.
• Injection pressures were measured in a closed system with controlled air compression percentages.
• Linear regression analysis was used to estimate pressure at 50% air compression.

Main Results:

• Boyle's law demonstrated high linearity (r = 0.99) in the model.
• Estimated net pressure at 50% compression was 744.8 mmHg (99% CI: 729.6-760.0 mmHg).
• Different syringe and needle combinations yielded similar pressure results.

Conclusions:

• Maintaining 50% or less air compression in syringes significantly reduces injection pressures below the 1293 mmHg nerve injury threshold.
• This technique offers a simple, objective, and real-time method for monitoring injection pressures.
• The method inherently controls injection speed, potentially enhancing safety during local anesthetic administration.