GB2317450A

GB2317450A - Central venous pressure zero-marker

Info

Publication number: GB2317450A
Application number: GB9619743A
Authority: GB
Inventors: David Stewart Simpson
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-09-21
Filing date: 1996-09-21
Publication date: 1998-03-25
Also published as: GB9619743D0

Abstract

A light or laser pen 13 is attached to a transducer holder (9) at the level of the atmospheric port on the transducer (6,Fig.1). The pen has a spirit-level built into its shaft (14). The pen may be 'levelled' manually with regard to the spirit level. A beam of light produces a 'spot' on the patient. The transducer holder may then be adjusted on its pole 10 until the 'spot' is at mid-chest level 14. This permits the transducer to be zeroed accurately to the level of the patient.

Description

CENTRAL VENOUS PRESSURE ZERO-MARKER This invention relates to a lightpen device creating a sharp spotlight for establishing the remote zero pressure level for a central venous pressure transducer.

Anaesthetists, surgeons and intensive care workers measure the central venous pressure of patients by introducing a catheter into a large central vein. The proximal end of the catheter is then connected to a remote pressure transducer.

The transducer is electrically connected to an LCD display of the current pressure at the catheter tip, in the patient. Zero pressure has to be established, relative to the patient. The proximal end of the catheter is opened to atmosphere by a three-way -tap, and the transducer is then adjusted up or down a pole, several feet from the patient, so that it lies at the level of the patient's chest. This is normally done by judgement only; by 'eyeballing' the relative height of the transducer. Alternatively an open ended disposable loop of clear plastic tubing with a column of water in it, can be helpful for zeroing.

Errors in zero are important. Normal levels are 5 to I Ocms., yet it is difficult to be accurate to more than a centimetre or two, especially when the transducer is at some distance from the patient. Water filled loops of plastic tubing are messy, inconvenient and a potential source of infection in a sterile environment.

The present invention provides a light or laser pen with a focused beam, which is attached to the transducer holder. The pen has a spirit-level in its shaft, so that with a simple levelling adjuster, a beam can be projected onto the patient's chest, so that the 'spot' is reliably at the level of the remote transducer. The pen may be integral to the transducer holder, or detachable. A clipping device secures it the level of the open three-way port. When the pen is switched on, the transducer height can then be adjusted on the pole, until the 'spot' is optimally on the centre of the patients chest.

This secures a dependable 'zero' mark.

The pen is similar in design to the device used for 'pointing' at overhead projection screens used for audience presentation The invention is now described by way of example with reference to the accompanying drawing in which -: Fig.l shows the present transducer- patient relationship and requirements.

Fig.2 shows the spiritlevel light-pen.

Fig.3 shows the pen in position on the transducer holder Fig.4 shows the invention in position relative to transducer and patient.

Referring to Fig.1, a central vein (3)in a patient (1), has a catheter (4) inserted, which is opened to atmosphere at the port (6) , for zeroing. The transducer (7) on the holder (9) is then adjusted up or down on the pole at the adjuster (10), until '6 ' is deemed to be at the same height as '3' (mid-chest level). This is normally done by rough judgement. Pressure is displayed at 8.

Referring to Fig 2., the lightpen(13) is dipped onto a plastic plafform (12) on the transducer holder (9). Currently marketed transducer holders have a range of ridges and horizontal platforms which may be ideal. A screw adjuster (15) permits the pen to be levelled, which can be confirmed by the spirit-level (14). A spot beam can then be projected at the patient (16) Referring to Fig.3, the lightpen (13) might be dipped to the back of the transducer holder (9)so that there is room for the pole adjuster (10), the transducer (7) and the atmospheric port (6) on the front.

Referring to Fig.4, the lightpen(13) is switched on, and a 'light-spot' (14) is projected onto the patient. The pen may be levelled, using the spirit-level and adjuster screw. The transducer holder (9) may then be adjusted up or down the pole, until the 'spot' on the patient is at the mid-chest level. The port of the transducer can then be opened to atmosphere, and 'zeroed'.

( a range of simple options for the pen level-adjuster, are possible. A screwadjuster is given in this description. This is an example, only)

Claims

CLAIMS 1 A central venous pressure zero marker, consisting of a highly focused lightpen with a spirit level built into its shaft and a manually adjustable levelling mechanism, which may be adjusted with regard to the spirit-level.
2. A central venous pressure zero marker as claimed in claim 1 wherein the pen is detachable but has a clip for attachment to existing transducer holders.
3. A central venous pressure zero marker as claimed in claim 1 wherein the pen, along with its level-adjusting mechanism is integral to the transducer holder.
4. A central venous pressure zero marker as claimed in claim 1, claim 2 and claim 3, wherein a laser is used rather than a conventional lightpen beam.