1985-07-30
1986-11-04
Rosenbaum, C. Fred
Surgery
Truss
Pad
128361, A61B 1742
Patent
active
046205446
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a vacuum extractor.
The vacuum extractor has been well accepted as having a useful place in modern obstetrics since Malstrom's cup was introduced in 1954. John Yonge (1706) had first tried to use a suction device but his instrument met with very little success. The vacuum found a place in clinical practice again in 1947 with Couzigous' ventouse eutocique in France, and Koller's instrument in Norway in 1950.
Since then the instrument has been improved by a number of workers. Lovset in 1965 suggested modifying the vacuum, by making one side of the vacuum cup thinner, moving the suction connection from the centre to the edge of the cup, and applying traction to the cup from four equally-spaced points at the peripheries of the cup. These points were attached to two loops of cord, each of which had its own block attached. The two blocks were then joined by a further loop which had a further block attached to it. However this arrangement was not considered practical, and did not gain wide acceptance.
In 1969, Bird suggested applying traction to the cup by a chain llinked to a small, centrally situated half ring. The peripherally placed vacuum suction tubing was connected to his cup in a similar manner to Lovset's cup.
In modern obstetrics the vacuum cups designed by Bird and Malstrom have gained wide acceptance. Both of these cups have the intrinsic disadvantage of producing a rotational force, causing one edge of the cup to lift while the other remains the fulcrum. The problem is illustrated in FIG. 1 of the accompanying drawings in which:
By vector analysis the force required to break the vacuum can be calculated using the formula:
The force (A) which effectively lifts the baby can be calculated using the formula:
This has to be computed for angles from 0.degree. to 45.degree. from the perpendicular. With a 5 cm Bird cup, the effective traction on the baby is approximately 50% when the direction of pull is 45.degree. from the perpendicular axis.
Most clinicians are aware of the problem and so attempt to pull at 90.degree. to the surface of the cup. As this is not always possible, the experienced clinician is able to apply force at the margin of the cup.
These rotational forces introduce unnecessary tissue trauma and decrease the effective lifting force of the vacuum cup.
According to the present invention there is provided a vacuum extractor having a cup shaped member for forming an air-tight seal around its lip in use and having means through which its interior can be evacuated in use, elongate connection means for transferring an applied force to the cup-shaped member, and adaptor means through which the connection means is attached to the cup-shaped member, the adaptor means being adapted and arranged so that the line of a force exerted on the cup through the connection means passes through or adjacent the centre of a closed figure defined by the lip of the cup-shaped member over a range of angles between the line of force and a line normal to the plane of the closed figure.
The adaptor means may be attached to the connection means through a ring or hook for attachment of a chain, cord, string, plastics extrusion or the like. The ring or hook may be slidable on an arcuate rod, the centre of the rod's arc being at or adjacent the centre of the closed figure defined by the lip of the cup-shaped member. The rod itself may be rotatable on the cup-shaped member so that the rod describes part of the surface of an imaginary sphere centred at or adjacent the centre of the closed figure. The rod may extend rigidly from a ring or plate freely rotatable on the base of the cup-shaped member.
Alternatively the adaptor means can be provided by a cord, string or other elongate flexible member extending from the cup-shaped member at its opposed sides. Again, the connection means is attached to the adaptor means so as to be movable along it.
The adaptor means may comprise a second elongate flexible member secured at each end of the cup-shaped member at diametrically opposed locations intermediate t
REFERENCES:
patent: 13453 (1855-08-01), Buffum
patent: 2227673 (1941-01-01), Price
patent: 2702038 (1955-02-01), Uddenberg
patent: 2871054 (1959-01-01), Zinke
patent: 4166648 (1979-09-01), Creskoff
patent: 4512347 (1985-04-01), Uddenberg
J. Lovset, "Vaginal Operative Delivery" (Scandanavian University Books, 1968).
Kartchner Gene B.
O'Neil Alexander G.
O'Neil Christine
Rosenbaum C. Fred
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