The subject matter disclosed herein relates to localizing bleeding, both internal and external, including localizing such occurrences outside of a hospital environment.
Vascular trauma with vessel disruption can occur in a variety of environments, including both military and civilian environments. In some instances, the vascular trauma may be internal, without a clear break (e.g., an entry or exit wound) in the skin corresponding to the location of the trauma. In such circumstances, it may be difficult to localize where in the body an internal bleeding event is occurring so that treatment can be applied or, indeed, if there is internal bleeding occurring at all. Even in the presence of entry and exit wounds, it may be difficult to ascertain which blood vessel was affected and the location of the bleed.
For example, a skilled or trained person may be able to determine if a severe bleed event is present based on indications of vascular injury that include pulsatile hemorrhage, expanding hematoma, bruit or thrill over the injury site, absent extremity pulses, and arterial pressure index<0.9. However, such indications may be insufficient to make such a determination even by a trained individual, and likely would be impossible or impractical for an untrained individual to evaluate. Further, even to the extent these factors may allow a skilled or trained person to determine if a vascular injury is present, they may be still insufficient to localize the internal site of the vascular trauma, which is necessary to apply treatment.
Certain embodiments commensurate in scope with the originally claimed subject matter are summarized below. These embodiments are not intended to limit the scope of the claimed subject matter, but rather these embodiments are intended only to provide a brief summary of possible embodiments. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.
In one embodiment, a method is provided for localizing a vascular bleed. In accordance with this embodiment, blood flow velocities are measured at one or more locations on a body of a patient. The blood flow velocities are fit to a vascular tree model. Based upon the fit of the blood flow velocities to the vascular tree model, one or both of a location or a size of a bleed event within the patient are determined.
In a further embodiment, another method is provided for localizing a vascular bleed. In accordance with this embodiment, one or more waveforms are generated using ultrasound imaging. The one or more waveforms describe one or both of vascular vessel cross-sectional area at one or more locations or blood flow velocity at the one or more locations. The one or more waveforms or components or features derived from the one or more waveforms are input to a trained machine learning algorithm. An output of the trained machine learning algorithm is one or both of a location or a size of a bleed event within a patient.
In another embodiment, a system for localizing bleed events is provided. In accordance with this embodiment, the system comprises an ultrasound scanner configured to generate ultrasound data at one or more locations of a body of a patient; a memory component configured to store one or more processor-executable routines; and a processing component configured to receive or access the ultrasound data and to execute the one or more processor-executable routines. The one or more routines, when executed by the processing component, cause the processing component to perform acts comprising: measuring at least blood flow velocities at one or more locations on a body of a patient; and processing at least the blood flow velocities or one or more components or features derived from at least the blood flow velocities to determine one or both of a location or a size of a bleed event within the patient.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Furthermore, any numerical examples in the following discussion are intended to be non-limiting, and thus additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments.
As discussed herein, bleeding, whether internal or external, can be difficult to diagnose and, if present, difficult to localize for appropriate treatment. Doppler ultrasound has been used in some circumstances to detect the presence of arterial injuries and can also be used for localization of the injury. However, the scanning process can be time consuming, especially if the bleed location (e.g., a puncture or tear in the blood vessel) is less than obvious, and may require a person trained in ultrasound to perform.
With this in mind, the present technique relates to localization of bleeds (e.g., blood vessel bleed events, such as punctures or tears in an artery) using fewer or a minimum number of ultrasound scans. In one implementation, doppler ultrasound measured blood flow velocities are used in a one-dimensional (1D) arterial tree model to determine the location and size of bleed. In a second implementation, ultrasound measured waveforms for blood flow velocity and vessel cross-sectional area are de-composed into forward and backward running wave components. The features in the de-composed waveforms are then used to locate the bleed using a trained machine learning algorithm.
Regardless of whether the first or the second technique is employed, once the bleed has been detected and accurately localized, a treatment plan can be formulated and therapy to contain blood loss delivered. Conventional therapeutic approaches at the point of care may include application of pressure or hemostatic pads, but additional therapies are being explored. For example, balloon catheters for bleeds in major arteries have recently been developed. Detailed information about the location of the bleed as may be acquired using the present techniques would enable deployment of such catheters in a location to maximize therapeutic effectiveness and to minimize side effects.
With the preceding in mind, and by way of providing useful context,
Each transducer element is associated with respective transducer circuitry, which may be provided as one or more application specific integrated circuits (ASICs) 20, which may be present in a probe or probe handle. That is, each transducer element in the array 14 is electrically connected to a respective pulser 22, transmit/receive switch 24, preamplifier 26, swept gain 34, and/or analog to digital (A/D) converter 28 provided as part of or on an ASIC 20. In other implementations, this arrangement may be simplified or otherwise changed. For example, components shown in the circuitry 20 may be provided upstream or downstream of the depicted arrangement, however, the basic functionality depicted will typically still be provided for each transducer element. In the depicted example, the referenced circuit functions are conceptualized as being implemented on a single ASIC 20 (denoted by dashed line), however it may be appreciated that some or all of these functions may be provided on the same or different integrated circuits.
Also depicted in
With the preceding system level discussion in mind as useful context, the present techniques may utilize such an ultrasound system to acquire raw data or reconstructed images that may be processed as discussed herein to localize the location of bleeding in a patient.
By way of example, in accordance with a first technique, vascular tree model is employed. While the vascular tree described in the examples below is an arterial tree, the methods and approaches described herein could also be applied to venous trees or a combined tree consisting of both arteries and veins. In one implementation the arterial tree model has multiple segments (e.g., 55 connected segments). Blood flow in the segments of the arterial tree model is modeled using a one-dimensional (1D) wave propagation model. Though 1D models are discussed herein to simplify explanation and illustration of the present concepts, the present technique may also be extended to use with two-, three-, or four-dimensional models (i.e., 2D, 3D, or 4D) and should therefore be understood to not be limited to the present 1D model examples. In one example, flow rate, pressure, and cross-sectional area are modeled or solved for by the arterial tree model as part of modeling blood flow. Terminal segments in the arterial tree model may have a zero-dimensional (0D) lumped model at the outlet modeling the terminal resistance and compliance. The heart may also be modeled using a 0D lumped model, such as a time-varying elastance model that may be used to simulate cardiac contraction.
Using this arterial tree model, 1D models of arterial bleeds may be simulated. By way of example, in studies performed in accordance with the present technique, bleeds of different sizes (2 mm in diameter, 2.5 mm in diameter and 4 mm in diameter) were modeled in the right femoral artery. In particular, the resistance to flow due to pressure drop across the bleed was modeled by treating the bleed as an orifice through which the blood expands into a much larger volume. This enables a larger size bleed to bleed more than a smaller size bleed. The pressure drop is modeled using the following equation:
Here As is the bleed area, A0 is the larger area into which the blood is expanding, Q is the flow rate, ρ is the density of blood and Kt is a constant. Tissue resistance seen by the bleed was also modeled using an assumption that tissue is a porous media with permeability K. Under these assumptions, tissue resistance is given by the following equation:
Here μ is the blood viscosity, L is the length of the porous media, A is its cross-sectional area and K is the permeability associated with the tissue. The cross-sectional area, A0, in the pressure-drop equation is assumed to be the same as the porous media cross-sectional area, A. A conceptualized view of this model is shown in
The terminal pressure is assumed to be zero, though in reality it will increase as blood starts to pool in the tissue. The tissue resistance seen by the bleed is lower than the microcirculation resistance. The bleed thus offers a low resistance path to the blood flow causing blood to be diverted to this location (though this effect may be temporarily dampened in real world scenarios due to autoregulation mechanisms).
The effects of this diversion of blood in response to a bleed event may manifest by impacting or otherwise influencing the arterial waveform seen for that arterial segment or a connected arterial segment. In this manner, an arterial flow waveform can be used to locate the bleed within the arterial tree. By way of example, and turning to
In the preceding example, the waveform shape changes because there is more bleed-out at the proximal (i.e., upstream) site compared to the distal (i.e., downstream) site. However, even when the amount of bleeding at the two sites are the same, the waveform shapes can be different. Consider
With the preceding in mind, and turning to
Based on the 1D arterial tree model a bleed event (e.g., blood vessel puncture or tear) may be localized and its size determined by measuring (step 90) blood flow velocities 92, such as using Doppler ultrasound, at one or more locations If the bleed location is approximately known, the ultrasound measurements may be made upstream or downstream of the bleed. On the other hand, if it is suspected that there is a bleed in the legs for example and the bleed location is completely unknown, then Doppler measurements can be made at a few landmark locations. The landmark locations could include the left and right knees, the left and right ankle and the upper portion of the left and right thighs, close to the groin. In addition, to blood flow velocities 82, additional information may be optionally acquired. For example, one or both of blood pressure 96 or heart rate 98 may be measured (step 94) using suitable methodologies.
The measured blood flow velocities 92 and any additional acquired blood pressure or heart rate data may be fit (step 100) to the 1D arterial tree model to determine the size and location of the bleed event (block 102). By way of example, in one embodiment the location and size of the bleed in the 1D arterial tree model 80 may be optimized to minimize the error between predicted and measured blood flow velocities 92.
While the preceding relates to one technique for determining the location and size or severity of a bleed event, Additional embodiments are also contemplated. For example, a second technique for localization of a bleed event using waveforms may be based on the observation that the bleed event (e.g., puncture or tear in a blood vessel, such as an artery) generates pulse wave reflections that may be extracted from the original waveform and used to locate the bleed.
For example, given pressure (p) and velocity (u) waveforms that may be generated using an ultrasound modality, the forward and backward running contributions can be written as:
Here the subscripts “+” and “−” denote the forward and backward running components (i.e., waves) respectively, c is the pulse wave velocity, and ρ is the blood density. While the above decomposition is written in terms of pressure and velocity, it could also be written in terms of area and velocity, both quantities that can be measured using ultrasound imaging.
Based on the above decomposition, one can define a quantity called wave intensity for the forward and backward running waves as:
In this context, the wave intensity is positive for forward running waves and negative for backward running waves.
With the preceding in mind,
Conversely, a scenario involving a bleed is illustrated in
The preceding examples correspond to decompositions of waveforms obtained at a proximal femoral location for a mid-femoral bleed event (i.e., upstream). Waveforms were also obtained and decomposed into forward and backward components for a bleed event close to the proximal femoral location (i.e., a 2 mm bleed in the proximal femoral artery). As shown in
With the preceding in mind, and turning to
Turning to
In practice, the trained machine learning algorithm may be used to localize and/or estimate the size or severity of a bleed event based on ultrasound data (e.g., the raw ultrasound data or waveforms, decomposed components of such waveforms, and/or features extracted from the raw or decomposed waveforms) acquired for a patient at one or more landmark locations. By way of example, and turning to
In the depicted example, the acquired ultrasound waveform data is decomposed (step 130) into forward components 132 and backward components 134, as discussed herein. One or more features 140 may be identified in the forward components 132 and/or backward components 134 and the identified features 140 may be provided as an input to the trained machine learning algorithm 150. Based on the provided input, the trained machine learning algorithm 150 outputs (block 102) a location and/or estimated size of a bleed event of the patient. As noted above, though the present example processes feature 140 extracted from decomposed waveforms 132, 134, in practice the trained machine learning algorithm may also or instead process raw versions of the ultrasound data and/or the decomposed waveforms 132, 134 in addition to or instead of the extracted features 140.
As noted above, once the bleed has been detected and accurately localized by either of the techniques described herein, a treatment plan can be formulated and an appropriate therapy applied to limit and/or stop blood loss. Such therapeutic approaches at the point of care may include, but are not limited to, application of pressure or hemostatic pads, as well as deployment of such balloon catheters at the determined location.
Technical effects of the invention include localization of bleeds (e.g., arterial bleed events) using fewer or a minimum number of ultrasound scans. In one implementation, doppler ultrasound is used to measure blood flow velocities in a one-dimensional (1D) arterial tree model to determine the location and size of bleed. In a second implementation, ultrasound measured waveforms for blood flow velocity and vessel cross-sectional area are de-composed into forward and backward components. The features in the de-composed waveforms are then used to locate the bleed using a trained machine learning algorithm.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.