Patent Application
20180008164
The present invention relates to a non-invasive method and system for assessing the survival of a transplanted flap. More particularly, the invention relates to a method and system for assessing the survival of a flap by detecting with a detection electrode the bioelectrical impedance of the skin to which the flap has been transplanted.
As disclosed in http://sunifeng.blogspot.tw/2015/08/blog-post_94.html, the most important issue after a flap surgery is to ensure that the flap in question survives, and whether a flap survives or not can be determined by observation, in particular by inspection, by palpation, by stabbing with a needle, and with a thermometer.
In other words, the survival of a transplanted flap can be determined by: 1) the color of the flap; 2) the flap's reaction to a capillary blanching test; 3) the warmth of the flap; and 4) how a stab wound of the flap bleeds.
The characteristics of a failed flap include: 1) a continuous decrease in temperature (a rapid decrease can be found where an artery lies, and a slow decrease can be found where a vein extends); 2) a loss of tissue flexibility (the flap may feel rigid where a vein lies, and empty where an artery extends); 3) an abnormal color (the flap may look pale where an artery lies, and bruised where a vein extends); and 4) a change of condition at the border of the flap (blisters may occur around the sutures).
Therefore, Taiwan Patent No. 1507172, titled “INFRARED THERMOGRAPHY SYSTEM AND METHOD FOR ANALYZING FACTORS THAT INFLUENCE SURFACE TEMPERATURE OF FREE FLAP”, discloses obtaining the actual surface temperature of a free flap on a living body via an infrared thermographer; obtaining a core temperature of the living body and an ambient temperature corresponding to the environment where the living body is; performing a thermal conduction- and thermal convection-related calculation on the core temperature and the ambient temperature to produce an estimated surface temperature; and according to the closeness between the estimated surface temperature and the actual surface temperature, determining whether factors influencing the surface temperature of the free flap have changed. Any change thus found will be used for compensation and calibration, in order to increase the accuracy of the surface temperature taken by the infrared thermographer of the free flap as a reference indicator.
However, the conventional observation methods are subject to the surroundings and therefore tend to be inaccurate. If an invasive detection method is used instead, a lower level of comfort can be expected during detection.
To overcome the aforementioned drawbacks of the prior art, the present invention provides a non-invasive method for assessing the survival of a transplanted flap, wherein the method is carried out as follows:
A. A constant current is generated at a fixed frequency and passed through a detection electrode. B. The detection electrode detects a bioelectrical impedance of the skin to which the flap has been transplanted. C. The bioelectrical impedance of the skin with the transplanted flap is compared with a pre-defined threshold value, and the former exceeding the latter is identified as an abnormal condition.
Preferably, step C is performed by subtracting a pre-transplantation bioelectrical impedance of the skin from a post-transplantation bioelectrical impedance of the skin to produce a difference, and the difference exceeding a pre-defined threshold value is identified as the abnormal condition.
Preferably, step C is performed by dividing a post-transplantation bioelectrical impedance of the skin that is detected with a relatively low-frequency current by a post-transplantation bioelectrical impedance of the skin that is detected with a relatively high-frequency current to produce a quotient, and the quotient exceeding a pre-defined threshold value is identified as the abnormal condition.
Preferably, step C is performed by standardizing a bioelectrical impedance of the skin, and either Im1(t)/Im1(0) or Im1(t)/Im2(0) exceeding a pre-defined threshold value is identified as the abnormal condition, wherein: Im1(t) is the ratio of a post-transplantation bioelectrical impedance of the skin that is detected over time with a relatively low-frequency current to a post-transplantation bioelectrical impedance of the skin that is detected over time with a relatively high-frequency current, Im1(0) is the ratio of a pre-transplantation bioelectrical impedance of the skin that is detected with the relatively low-frequency current to a pre-transplantation bioelectrical impedance of the skin that is detected with the relatively high-frequency current, and Im2(0) is the ratio of a bioelectrical impedance of a normal skin that is detected with the relatively low-frequency current to a bioelectrical impedance of the normal skin that is detected with the relatively high-frequency current.
The present invention also provides a non-invasive system for assessing the survival of a transplanted flap by the foregoing method, wherein the non-invasive system includes: a control unit; a variable-frequency current generator circuit electrically connected to the control unit; a pair of detection electrodes electrically connected to the variable-frequency current generator circuit; and a voltage-reading circuit electrically connected to the detection electrodes and the control unit.
The control unit instructs the variable-frequency current generator circuit to generate the constant current. The voltage-reading circuit reads the potential difference between the detection electrodes. Then, the control unit calculates the bioelectrical impedance of the skin with the transplanted flap according to the constant current and the potential difference, and compares the bioelectrical impedance with the pre-defined threshold value.
The non-invasive system of the present invention further includes a control input interface circuit, which is electrically connected to the control unit and through which the desired frequency values can be input.
The non-invasive system of the present invention further includes a wireless transmission circuit electrically connected to the control unit in order to output the data obtained by the control unit.
The non-invasive system of the present invention further includes a display interface circuit electrically connected to the control unit in order to output the data obtained by the control unit.
The foregoing technical features produce the following advantageous effects:
1. The survival of a transplanted flap can be accurately assessed by measuring a bioelectrical impedance of the skin to which the flap has been transplanted, and this approach is less subject to the surroundings than the conventional ones.
2. The non-invasive detection system and method of the present invention feature a high level of comfort during detection and are therefore suitable for long-term monitoring applications.
The present invention incorporates the foregoing technical features into a non-invasive method and system for assessing the survival of a transplanted flap, whose major effects are demonstrated by the following embodiments.
Referring to
In this embodiment, the foregoing system is configured to perform a method including the following steps:
A. The control unit 1 instructs the variable-frequency current generator circuit 2 to generate a constant current at a fixed frequency and pass the constant current through the detection electrodes 3. The desired frequency value can be input through the control input interface circuit 5.
B. The detection electrodes 3 detect a bioelectrical impedance of a skin to which a flap has been transplanted and of a normal skin. More specifically, the voltage-reading circuit 4 reads the potential difference between the detection electrodes 3, in order for the control unit 1 to calculate the bioelectrical impedance of the skin with the transplanted flap or of the normal skin according to the constant current and the potential difference.
C. The bioelectrical impedance of the skin with the transplanted flap is compared with a pre-defined threshold value. When the bioelectrical impedance of the skin with the transplanted flap exceeds the pre-defined threshold value, it is determined that an abnormal condition has occurred. The pre-defined threshold value is determined by a medical professional. For example, the difference in bioelectrical impedance between the skin with the transplanted flap and the normal skin (i.e., the variation of bioelectrical impedance of the skin with the transplanted flap) is calculated. When the ratio of the variation to the bioelectrical impedance of the normal skin exceeds a certain percentage (meaning the variation is significant), it is determined that the skin with the transplanted flap is in an abnormal condition (e.g., necrosis has taken place). The pre-defined threshold value will be dealt with further below in association with different determination methods.
The wireless transmission circuit 6 is configured to transmit the data obtained by the control unit 1 to a backend PC or other processer. The display interface circuit 7 is configured to output the data obtained by the control unit 1.
Referring to
Referring to
The embodiments described above should be able to enable a person of ordinary skill in the art to fully understand the operation, use, and effects of the present invention. Those embodiments, however, are but some preferred embodiments of the invention and are not intended to be restrictive of the scope of the invention. All simple, equivalent changes and modifications made according to the appended claims and the disclosure of this specification should fall within the scope of the present invention.
