Surgery – Blood drawn and replaced or treated and returned to body – Constituent removed from blood and remainder returned to body
Reexamination Certificate
1998-10-21
2004-05-18
Bianco, Patricia (Department: 3762)
Surgery
Blood drawn and replaced or treated and returned to body
Constituent removed from blood and remainder returned to body
C604S004010, C422S044000, C128SDIG003, C210S645000, C210S646000, C210S739000, C210S746000, C210S087000, C210S090000, C210S321600, C210S418000
Reexamination Certificate
active
06736789
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a method for continuous monitoring of an extracorporeal blood treatment, especially a method whereby blood in an extracorporeal circulation flows through a blood chamber of a dialyzer or hemofilter subdivided by a semipermeable membrane into the blood chamber and a dialysis fluid chamber or a hemofiltrate chamber. In addition, the present invention concerns a machine for extracorporeal blood treatment with a device for continuous monitoring of the extracorporeal blood treatment.
BACKGROUND OF THE INVENTION
Acute emergencies during dialysis demand immediate action. Such emergencies may be caused by the blood treatment itself or they may occur independently of the blood treatment. A drop in blood pressure is one of the main complications during a dialysis treatment and/or hemofiltration. The most common cause of such an incident is hypovolemia due to excessive withdrawal of fluid. Other causes may include concentration changes, temperature variations or biocompatibility reactions (Journal für das Nephrologische Team [Journal for the Nephrological Team], vol. 3 (1996), p. 113).
There are known hemodialysis machines having a plug-in unit which permits indirect measurement of a patient's systolic and diastolic blood pressure. This plug-in unit is a conventional sphygmomanometer with an inflatable rubber cuff connected to a manometer. To measure systolic blood pressure, the cuff pressure is increased slowly until the pulse is no longer palpable. The systolic pressure can be measured by subsequently reducing the cuff pressure slowly until the first pulse beat can be palpated. If the cuff pressure drops below the systolic blood pressure, vascular noises occur in synchronization with the pulse, but cannot be detected on reaching the diastolic pressure as the cuff pressure is released further. The measurement is fully automatic with an acoustic sensor, a pressure sensor and an electric air pump for inflating the cuff. One disadvantage is that with the known dialysis machines having a conventional sphygmomanometer, a patient's blood pressure is monitored only at certain intervals. There is usually an interval of approximately 10 to 15 minutes between two measurements. Shorter intervals in the minute range are possible, but this would be unreasonable for the patient during a hemodialysis treatment, usually lasting for several hours. Within this period of time, signs of a cardiovascular problem may remain undetected, and the subsequent measurement may be too late to initiate appropriate countermeasures so that treatment can be continued without interruption.
A method is known for continuous, noninvasive monitoring of changes in blood pressure on the basis of analysis of the pulse wave transit time (Psychophysiology, vol. 13, no. 1, 1976). With the known method, the blood pressure is determined on the basis of the transit time required for a wave produced by a cardiac contraction to reach a certain site in the body. Various studies have confirmed the fact that there is an approximately linear relationship between the pulse wave transit time and the systolic and diastolic blood pressure or the mean blood pressure.
OBJECTS OF THE INVENTION
The object of the present invention is to provide a method of continuous monitoring of an extracorporeal blood treatment that will reduce the risk of complications due to a drop in blood pressure during the blood treatment. This object is achieved according to invention using a method of continuously monitoring a subject's extracorporeal blood treatment comprising the steps of: providing blood to be treated to a blood treatment device in an extracorporeal blood path; determining a pulse wave velocity or pulse wave transit time; determining a blood pressure value by correlating the pulse wave velocity or pulse wave transit time with a predetermined blood pressure value or value correlating to blood pressure for the pulse wave velocity or pulse wave transit time; comparing the blood pressure value with a predetermined blood pressure limit; and generating a signal to initiate a change in the extracorporeal blood treatment when the blood pressure value falls outside the predetermined blood pressure limit.
Another object of the present invention is to create a device for extracorporeal blood treatment, where the risk of complications due to a drop in blood pressure during the blood treatment is reduced. This object is achieved with a blood treatment device according to the present invention having an extracorporeal blood path connecting the subject to the blood treatment device, the blood treatment device having an inlet and an outlet, the extracorporeal blood path carrying blood from the subject to the blood treatment device inlet and from the blood treatment device outlet back to the subject. The blood treatment device further comprises a measurement device for continuously determining the subject's pulse wave velocity or pulse wave transit time. A correlation device is connected to the measurement device and the correlation device is adapted to correlate the pulse wave velocity or pulse wave transit time with a predetermined blood pressure value or value correlating with blood pressure. A comparison device is connected to the correlation device and the comparison device is adapted to compare the blood pressure value or value correlating with blood pressure with a predetermined blood pressure limit and generate a signal when the blood pressure value is outside the blood pressure limit. A control unit is connected to the comparison device and the control unit adapted to initiate a change in the subject's extracorporeal blood treatment in response to the signal.
With the method and the device according to the present invention, the blood pressure or a quantity correlating with the patient's blood pressure is monitored continuously during the blood treatment. If the measured value drops greatly, a control signal is generated to initiate a measure in the treatment process to counteract the drop in blood pressure. Since the measurement is performed continuously, a drop in blood pressure can be detected immediately and counteracted immediately.
This continuous, noninvasive blood pressure measurement is based on detection of the propagation rate of the pulse waves produced by contractions of the cardiac contractions propagating through the patient's arterial system. Instead of the propagation rate, the transit time of the pulse waves can be determined over a segment of the vascular system of a predetermined length.
It is advantageous that the patient is unaware of the monitoring of the blood treatment, especially since no tedious blood pressure measurement using an inflatable rubber cuff is necessary at certain intervals.
Blood treatment machines are understood to include all machines in which the blood of a patient or a donor is subjected to a certain treatment in an extracorporeal system. Blood treatment machines include not only machines for hemodialysis or hemofiltration but also the known cell separators in which a donor's blood is centrifuged to separate it into its components.
For continuous measurement of blood pressure, the pulse wave transit time is preferably determined. The means for determining the pulse wave transit time include a device for recording an electrocardiogram and a device for detecting the pulse waves at a location remote from the patient's heart, in particular a fingertip or the earlobes, as well as a device for determining the time between the time at which the so-called R wave (maximum ventricular depolarization) occurs in the electrocardiogram and the time when the pulse wave is detected at a location on the patient's body which can be attributed to the cardiac contraction. In an especially advantageous embodiment, the device for detecting the pulse waves may also be the arterial pressure sensor of the extracorporeal blood circulation which is present anyway in the known blood treatment equipment.
With the method and the de
Bianco Patricia
Fresenius Medical Care Deutschland GmbH
Kenyon & Kenyon
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