Tourniquet apparatus for applying minimum effective pressure

• US 5,439,477 A
• Filed: 09/28/1993
• Issued: 08/08/1995
• Est. Priority Date: 01/29/1990
• Status: Expired due to Term

• Current Assignee: Zimmer Orthopaedic Surgical Products (Zimmer Biomet Holdings, Inc.)
• Original Assignee: Abatis Medical Technologies Limited
• Inventors: McEwen, James A.
• Primary Examiner(s): Pellegrino, Stephen C.
• Assistant Examiner(s): NASSER, ROBERT L
• Application Number:
  US08/128,478
• Time in Patent Office: 679 Days
• Field of Search: 604/30, 604/31, 604/65-67, 606/201-203, 128/677, 128/686, 128/783, 128/744, 128/DIG. 12, 128/DIG. 13
• US Class Current: 606/203
• CPC Class Codes: A61B 17/1355 Automated control means therefor
• CPC Class Codes: A61B 2505/05 Surgical care
• CPC Class Codes: A61B 5/02255 the pressure being controlled by plethysmographic signals, e.g. derived from optical sensors
• CPC Class Codes: A61B 5/1106 to assess neuromuscular blockade, e.g. to estimate depth of anaesthesia
• CPC Class Codes: A61B 5/6828 Leg
• CPC Class Codes: A61B 5/6829 Foot or ankle
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61B 5/7435 Displaying user selection data, e.g. icons in a graphical user interface
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: Y10S 128/12 Pressure infusion
• CPC Class Codes: Y10S 128/13 Infusion monitoring

Abstract

Tourniquet apparatus for use in intravenous regional anesthesia and limb surgery includes a pressurizing cuff for substantially encircling a limb and applying a varying pressure to an underlying vein in response to variations in a pressure control signal, applied venous pressure sensing means for producing an applied venous pressure signal representative of a pressure applied by the cuff to the underlying vein, venous pressure estimation means for producing a venous fluid pressure signal representative of the pressure of fluid in the vein distal to the cuff, and pressure control means responsive to the venous fluid pressure signal and applied venous pressure signal for generating a pressure control signal to maintain a predetermined relationship between the applied venous pressure signal and the venous fluid pressure signal. The apparatus automatically controls the introduction, retention and release of anesthetic fluid in the limb.

Claims

1. Tourniquet apparatus for maintaining the lowest constant pressure applied by a pressurizing cuff to a limb to stop blood flow past the cuff for the duration of a surgical procedure, comprising:

a) a pressurizing cuff responsive to cuff pressure control means for substantially encircling and applying pressure to a limb;

b) distal flow sensing means for sensing the flow of blood past the pressurizing cuff;

c) cuff pressure control means for controlling the pressure applied by the pressurizing cuff to the limb in response to a cuff pressure control signal;

d) signal generating means responsive to the distal flow sensing means for generating a variable signal indicative of varying pressure to be applied by the cuff to the limb;

e) estimation means for producing an estimate of a pressure level to be applied by the cuff to the limb so that the sensed blood flow is below a threshold level near zero;

f) constant pressure means for producing a constant signal that is greater than the estimate and is indicative of a constant reference pressure to be applied by the cuff to the limb to stop blood flow past the cuff for the duration of a surgical procedure; and

g) selection means for selecting either the variable signal or the constant signal to be the cuff pressure control signal.

2. Apparatus as defined in claim 1 wherein the estimate produced by the estimation means is indicative of the lowest pressure at which no blood flow can be sensed past the pressurizing cuff.

3. Apparatus as defined in claim 1 wherein the estimate produced by the estimation means is indicative of the highest pressure at which blood flow can be sensed past the cuff.

4. Apparatus as defined in claim 2 wherein the estimation means also produces a second estimate indicative of the highest pressure at which blood flow can be sensed past the pressurizing cuff, and wherein the constant pressure means is responsive to the estimation means for producing a constant signal that is a function of the first-mentioned estimate and the second estimate.

5. Apparatus as defined in claim 1 wherein the estimate produced by the estimation means is indicative of the highest pressure at which blood flow can be sensed past the pressurizing cuff.