ZMI Corp. v. Cardiac Resuscitator Corp.

• Decision Date: 22 April 1988
• Docket Number: No. 87-1338,87-1338
• Citation: 6 USPQ2d 1557,844 F.2d 1576
• Parties: ZMI CORPORATION, Plaintiff-Appellee, v. CARDIAC RESUSCITATOR CORPORATION, Defendant-Appellant.
• Court: U.S. Court of Appeals — Federal Circuit

Page 1576

844 F.2d 1576

6 U.S.P.Q.2d 1557

ZMI CORPORATION, Plaintiff-Appellee, v. CARDIAC RESUSCITATOR CORPORATION, Defendant-Appellant.

No. 87-1338.

United States Court of Appeals Federal Circuit.

April 22, 1988.

Robert E. Hillman, Fish & Richardson, Boston, Mass., argued, for plaintiff-appellee. With him on the brief, was G. Roger Lee.

Jerry D. Voight, Finnegan, Henderson, Farabow, Garrett & Dunner, Washington, D.C., argued, for defendant-appellant. With him on the brief, was C. Larry O'Rourke.

Before ARCHER, Circuit Judge, NICHOLS, Senior Circuit Judge, and MAYER, Circuit Judge.

ARCHER, Circuit Judge.

Cardiac Resuscitator Corporation (CRC) appeals from a judgment of the United States District Court for the District of Oregon in favor of ZMI Corporation (ZMI) holding that CRC infringed U.S. Patent No. 4,349,030 ('030) which issued to Alan Belgard, et al. and was assigned to ZMI. We reverse-in-part, vacate-in-part, and remand.

Background

ZMI sued CRC for infringement of the '030 patent directed to an external, noninvasive cardiac stimulation device. Six models of cardiac stimulation devices manufactured by CRC were found to infringe: "Heart Aid" Models 80, 95 and 97 and "Pace Aid" Models 50, 52 and 53. For the purpose of this infringement suit, all three of the Heart Aid models are considered together as are all three of the Pace Aid models.

When a heart has stopped (asystole) or has slowed to the point of no longer being life sustaining, or when ventricular fibrillation occurs (i.e., an electrical malfunctioning of the heart evidenced by irregular beating that prevents blood from flowing through the heart), an electrical stimulus applied to the heart may defibrillate the heart and/or pace the heart at a selected rate.

In the 1950's, external, noninvasive pacing was first introduced to artificially stimulate hearts with pulses of electricity applied externally. This method failed to gain widespread acceptance because the external application of pulses of electricity caused too much pain to the patient. In passing the electrical pulses through the skin and the skeletal muscles of the body to reach the heart, the patient experienced violent and painful chest pounding and painful stinging of the skin. To avoid these problems, invasive pacing techniques were developed whereby electrical pulses were delivered to the heart by electrodes placed inside the body. However, these methods proved too slow and invasive to be satisfactory.

The '030 patent is directed toward a system for applying external noninvasive cardiac stimulation whereby electrical pulses are applied to a patient externally but are within a pain threshold so as to be useful on a conscious patient. The patent states that this is accomplished "through the use of electrodes with large surface, nonmetallic, skin-contacting members providing low current density, and also through the use of a pulse generator for the electrodes that provides constant current without spikes." The '030 patent has two independent claims: apparatus claim 1 and method claim 14. ¹ The district court found that

each of these claims includes the following three components:

1. a pulse duration longer than five milliseconds;

2. constant current pulses without high current spikes; and

3. electrodes that have nonmetallic skin-contacting members.

It is not disputed on appeal that the accused devices include the first two components (pulse duration longer than five milliseconds and constant current pulses without spikes). The dispute here goes to whether the accused devices meet the claim limitation:

a pair of electrodes having nonmetallic skin-contacting members that provide low current density to reduce stimulation of local sensory nerves and resulting pain.

CRC argues that it is the electrodes themselves that must function to provide the low current density, while ZMI argues that the three element combination provides the low current density. ²

The district court found that "[t]he electrode covered by the patent must be nonmetallic and provide low current density in order to reduce the stimulation of local sensory nerves which results in pain" but also found that "a person skilled in the art would understand that the requirement that the electrodes deliver low current density is a result of the three element combination and not simply a result of the electrodes themselves." The court went on to say that:

The relevant inquiry before this court as to the electrode element of this patent is whether CRC's devices use nonmetallic electrodes in combination with the other two elements of the invention, constant current and long pulses, in order to provide lower current and resulting low current density. There is no dispute that CRC's devices do that.

The primary difference for the purpose of this infringement suit between CRC's Pace Aid and Heart Aid models is in the amount of current supplied. The Heart Aid model, used in emergency situations when ventricular fibrillation occurs, transmits too high a current to make it tolerable to most conscious patients. The Pace Aid model, on the other hand, uses a much lower current and is useful on conscious patients.

CRC argues on appeal that the district court erred in its interpretation of the claims and that when properly interpreted the claims are not infringed by the Heart Aid and Pace Aid devices either literally or under the doctrine of equivalents.

OPINION

Analysis of patent infringement involves two inquiries: first the claims must be properly construed to determine their scope and then it must be determined whether the properly interpreted claims encompass the accused structure. Mannesmann Demag Corp. v. Engineered Metal Products Co., 793 F.2d 1279, 1282, 230 USPQ 45, 46 (Fed.Cir.1986). Literal infringement requires that every limitation of the patent claim must be found in the accused device. Id. Improper claim construction, i.e., an improper determination of the scope of the claims, can distort the entire infringement analysis. Moeller v. Ionetics, Inc., 794 F.2d 653, 656, 229 USPQ 992, 994 (Fed.Cir.1986).

A. Claim Construction

"Claim construction is reviewed as a matter of law.... However, interpretation of a claim may depend on evidentiary material about which there is a factual dispute, requiring resolution of factual issues as a basis for interpretation of the claim.... The question of literal infringement (do the claims read on the accused device) is determined as a factual inquiry and is reviewed on a clearly erroneous standard." Uniroyal, Inc. v. Rudkin-Wiley Corp., 837 F.2d 1044, 1054, 1988 WL 990, 5 USPQ2d 1434, 1441 (Fed.Cir.1988).

The district court found:

All claims of the Belgard patent contain the following three essential elements required by independent claims 1 and 14:

1. two electrodes having nonmetallic skin-contacting members that provide low current density to reduce stimulation of local sensory nerves and resulting pain;

2. constant current pulses without high-current spikes that cause skeletal muscle contraction;

3. a pulse duration of greater than 5 milliseconds to reduce the threshold current required for cardiac stimulation to permit the use of lower current pulses to provide effective stimulation at the same time that skeletal muscle contraction is reduced by the lower current.

After holding that the constant current and the pulse duration limitations of the claims are found in the accused device, the district court explained with respect to the claim limitation relating to the electrodes:

The current density provided by the electrodes is primarily a function of the current coupled to them by the electric signal source....

The court finds that a person skilled in the art would understand that the requirement that the electrodes deliver low current density is a result of the three element combination and not simply a result of the electrodes themselves....

The relevant inquiry before this court as to the electrode element of this patent is whether CRC's devices use nonmetallic electrodes in combination with the other two elements of the invention, constant current and long pulses, in order to provide lower current and resulting low current density. There is no dispute that CRC's devices do that.

CRC argues that the district court erred, as a matter of law, when it "construed the requirement for low current density as applying to 'the entire [claimed] system.' " CRC argues that the district court failed "to accept the plain words of the claims in view of the patent specification and ... prosecution history." In essence CRC contends that the plain meaning of the claim as drafted requires something in the structure of the electrode that causes a low current density, as for example, electrodes having a high impedance or a large surface area. CRC argues that since its electrodes are low impedance electrodes they do not provide the low current density and therefore its Pace Aid and Heart Aid devices do not infringe.

ZMI responds by arguing that according to its expert " 'the only reason current density appears in that location [in the claim] is that's where [the current] is actually delivered to the skin.' In other words, the low current density provided by the whole system--by all the elements of the claim--is delivered to the patient by the electrodes, thus accounting for its grammatical location in the claim." ZMI further states that no electrode can itself provide low current density. Rather, the current density provided by electrodes is primarily a function of the current coupled to them by an electric signal source.

In interpreting claims resort should be made to the claims at issue, the specification, and the prosecution history. Loctite Corp. v. Ultraseal Ltd., 781 F.2d 861, 867, 228 USPQ 90, 93 (Fed.Cir.1985). All three are illuminating in this instance.

1. The claims

"The threshold requirement in claim construction is an examination of the claim at issue." McGill Inc....