Blood Pressure Measurement

Invasive (direct) Method of Blood Pressure Measurement

Introduction • This technique involves direct

measurement of arterial pressure by inserting a catheter (thin, hollow, and flexible tube).

• Invasive (intra-arterial) blood pressure (IBP) monitoring is a commonly used technique in the Intensive Care Unit (ICU) and in the operating theatre.

Cont. Introduction

• IBP technique also allows accurate blood

pressure readings specially the very low

pressures, for example in shocked patients.

• It allows continuous ‘beat-to-beat’ blood

pressure monitoring.

• Its complex procedure involves many risks.

The first invasive bloodpressure measurement

• The first invasive

attempt to measure

blood pressure was

made by Stephen

Hales in 1733.

• He inserted a glass

tube directly into the

artery of a horse

Catheterization method types

• Generally, this Invasive technique can be divided

into two division:

Extravascular Sensor System

Intravascular Sensor System

Extravascular Sensor System

• The sensor is located behind the catheter and the vascular pressure is transmitted by hydraulic connection.

catheter

Invasive BP transducer kit

IBP sensor

Percutaneous radial artery cannulation

Steps to: Percutaneous radial artery cannulation

(A) The wrist is positioned and the artery identified by palpation. (B) The catheter-over-needle assembly is introduced through the

skin and advanced toward the artery.(C) Entry of the needle tip into the artery is identified by the

flash of arterial blood in the needle hub reservoir. (D) Needle-catheter assembly is advanced at a lower angle to

assure entry of the catheter tip into the vessel. (E) If blood flow continues into the needle reservoir, the catheter

is advanced gently over the needle into the artery.(F) The catheter is attached to pressure monitoring tubing while

maintaining proximal occlusive pressure on the artery.

Specification

• Anesthetic solution (typically 1% lidocaine) is injected intradermally and subcutaneously alongside the artery, using a 25- or 26- gauge needle

• A 3-mL syringe with the plunger removed should be used as a blood reservoir

• Teflon catheter is the most common one used for radial artery cannulation

• The size (20- or 18-gauge) of the catheter• The catheter is advanced at an angle of 30 to 45

degree and lowering with each advance to ensure that catheter enters the vessel lumen

Advantages of direct arterial blood pressure measurement

• Arterial blood sampling• Continuous real-time monitoring• Intentional pharmacologic or mechanical

cardiovascular manipulation• Failure of indirect blood pressure

measurement• Supplementary diagnostic clues.

Implantation technique for blood pressure measurement

• A novel less-invasive blood pressure monitoring system involve the principle:

if a blood vessel is pressed against a flat surface of a pressure sensor diaphragm until vessel flattening occurs, according to Laplace’s law the pressure measured by the sensor will be approximately equal to the pressure inside the vessel

Implantable blood pressure monitoring system

Prototype implantable blood pressure monitoring

cuff with rigid isolation ring

Implant electronic system architecture

Blood pressure