A Pilot Study to Assess the Feasibility and Tolerability of the AccuFlow Perfusion Sensor for Intrapartum Hemorrhage

July 10, 2021 updated by: Megan Lord

Non-Invasive Hemorrhage Monitoring: A Pilot Study to Assess the Feasibility and Tolerability of the AccuFlow Perfusion Sensor for the Detection of Intrapartum Hemorrhage

Obstetric hemorrhage is one of the leading causes of maternal death worldwide. One of the challenges in management of hemorrhage is that young, healthy women compensate for blood loss via peripheral vasoconstriction, so they maintain their blood pressure and heart rate at normal levels even after experiencing significant blood loss. By the time vital sign abnormalities appear, interventions must be performed extremely rapidly to avoid organ damage and maternal death. Clinical methods of estimating blood loss in real time, such as visual estimation, are notoriously unreliable, and changes in laboratory testing such as hemoglobin levels lag hours behind actual blood loss. A tool which can detect and quantify blood loss in real time, before vital sign changes occur, has the potential to allow for earlier mobilization of resources and intervention in these cases, thus saving lives. This device is meant to detect changes in skin blood flow which reflect vasoconstriction. The investigators believe that this device, therefore, has the potential to be able to detect and quantify blood loss in real-time. However, as this novel device has never been used for this purpose, before undertaking a large clinical trial, the investigators feel it is necessary to perform a pilot study to assess the feasibility and tolerability of this device. The investigators plan to test this by asking 50 patients undergoing planned cesarean section to wear the device during their surgery. The device will collect skin perfusion measurements during the surgery, which will not be available to the operating team. The patients will also be asked to complete a survey regarding their experience wearing the device. The investigators will use this information to ensure that the device is transmitting interpretable data, that patients feel the device is tolerable during surgery, and to ensure that the device can be used in the operating room without any unforeseen logistical challenges which would need to be addressed in planning a larger trial. The investigators will perform a preliminary comparison of sensor readings to laboratory findings, to assist in planning a larger trial.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Hemorrhage remains the leading cause of direct pregnancy-related death in both the developing world and the developed world. Young, healthy patients compensate for hemorrhage via peripheral vasoconstriction, delaying the emergence of vital sign abnormalities until 15-30% of total blood volume has been lost (1-2L in a term pregnant patient). A significant drop in blood pressure and marked tachycardia (>120bpm) are not seen until 30-40% of blood volume has been lost. After 40% loss, however, patients may rapidly decompensate, leaving a narrow window between the emergence of vital sign abnormalities and rapid clinical decompensation. In facilities where obstetricians and anesthesiologists are not in-house at all times and blood product availability is limited, this narrow window may prove catastrophic.

Furthermore, management of obstetrical blood loss presents many unique challenges. First, during delivery, when hemorrhage is expected and occurs acutely and visibly, blood is often mixed with amniotic fluid, making it difficult to establish actual blood loss. Second, laboratory measurement of hemoglobin concentrations can be falsely normal during an acute episode of bleeding, as the hemoglobin measured does not reflect actual hemoglobin concentration until several hours after the hemorrhage event, when equilibration occurs. Third, unlike other surgical patients, postpartum women are expected to experience ongoing vaginal bleeding after their delivery. Bleeding which is persistently slightly heavier than average can lead to significant blood loss over a period of several days, without either the patient or the staff caring for her recognizing the hemorrhage until the patient becomes symptomatic or vital sign instability occurs. The postpartum uterus can serve as a reservoir for retained blood and clot, allowing a patient to continue bleeding into her uterus after delivery without any external evidence of bleeding. In a thin patient this is frequently recognized on "fundal checks" where the size of the uterus is evaluated, but in obese patients the uterine fundus may be difficult to appreciate, and a significant volume of blood can accumulate in the uterus before it is recognized.

Due to the high risk of mortality related to postpartum hemorrhage and the difficulties providers face quantifying blood loss accurately after delivery,, it is imperative to develop a tool that can detect and quantify hemorrhage before vital sign changes occur. This tool should be simple to use, allowing healthcare providers at all levels to identify hemorrhage early and to mobilize appropriate resources. This will facilitate earlier intervention to treat blood loss before clinical decompensation. As stated, vasoconstriction is the earliest physiologic responses to acute hypovolemia6 and, as such, would be an appropriate target for such a tool.

The AccuFlow Sensor is a device that is based on Combined Heat-Flux and Temperature Sensor (CHFT+) technology developed in the heat transfer laboratory at Virginia Tech and produced by ThermanSENSE Corp (Roanoke, VA). The device, which consists of a heat flux sensor, a thin-film thermocouple, and a heater element, makes direct, quantitative measurements of perfusion occurring at the surface of exposed tissue in real-time. The sensor is less than 1mm thick, covers one square inch of skin, and adheres to the patient's skin using a piece of medical-grade silicone adhesive tape. The heater applies a small amount of heat to the skin surface, raising its temperature to approximately 39 degrees C. The heat flux sensor measures the rate at which the heat dissipates into the tissue, and uses this to calculate perfusion using the Pennes Bio-Heat Transfer Equation, which was developed to describe patterns of heat distribution in the human forearm and which has been the standard tool to predict temperature distributions in living human tissue since the 1950s.10 The sensor measures both surface perfusion and deep perfusion (1-2cm below the skin surface).

The primary theoretical source of patient injury or discomfort from the device is thermal injury from the heater element. Under typical circumstances, the device heats up to approximately 39 degrees Celsius (102 Fahrenheit, the temperature of a typical hot tub), and to prevent thermal injury, the device automatically shuts off should it reach a temperature of 45 C (113F, just above the typical hot-shower temperature of 110F). The device has been tested for comfort and tolerability on 20 healthy volunteers, who reported no discomfort while wearing the device or afterwards. Prior studies have shown no evidence of thermal injury in tissues exposed to a temperature of 39C for prolonged periods, and that exposure to temperatures of 45C causes mild thermal injury only after 150 minutes of constant exposure.11 As this device only heats up while it is taking a measurement, and never higher than 45C, the risk of a thermal injury while wearing the device for the duration of a cesarean section as planned during this study is extremely low. However, should the sensor become uncomfortable to the patient, it can easily be removed. To date, the sensor has been used to evaluate viability of organs intended for transplantation, by measuring blood flow at the surface of the organ.7 Currently, the sensor is being used to evaluate differences in tissue perfusion between pediatric patients with sickle cell anemia and healthy controls in an ongoing research study at Virginia Tech. Of note, the device meets FDA criteria for a nonsignificant risk device, and has been determined to be a nonsignificant risk device by the Institutional Review Board at Virginia Tech/Carilion Clinic for use in adult and pediatric patients at Carilion Clinic facilities. As mentioned before, the patent-pending AccuFlow device is provided by ThermaSENSE Corp. (Roanoke, VA) and a number of sensors will be contributed for the purpose of this study. The device has not yet been studied for detection of obstetric hemorrhage.

In order to determine whether the device is able to accurately detect obstetric hemorrhage, it must be tested on a number of patients who can be identified and enrolled in a research study prior to experiencing a significant volume of blood loss, and whose volume of blood loss can be retrospectively calculated with some degree of accuracy and compared to the device's measurements. Patients undergoing planned, scheduled cesarean delivery are an ideal study population, because they undergo routine measurements of height, weight, hemoglobin, and hematocrit before surgery, and a repeat hemoglobin and hematocrit the day after surgery, once physiologic equilibration has occurred. From these hematocrit measurements, the percentage and volume of blood loss can be calculated and compared to the measurements obtained from the Non-Invasive Blood Perfusion Sensor.

The investigators propose to perform a pilot study consisting of 50 patients, with a planned interim analysis after 25 patients. These patients will be asked to wear the sensor during their planned cesarean delivery, and to complete a survey immediately after their surgery regarding their experience wearing the device. The device will be applied preoperatively and removed postoperatively, and a member of the study team will remain in the operating room to monitor the device and to note any significant events which occur during surgery, as well as any potential challenges with the use of the device which must be considered in planning future trials. Additional information will be gathered from the patients' charts including demographics, height, weight, hemoglobin and hematocrit before and after surgery. The investigators will review the sensor readings and the laboratory findings to determine which of a number of different methods of analyzing device readings should be used in a larger trial, as well as which of the measurement sites used by the sensors provides the most relevant data, in order to streamline the device design prior to a larger trial.

Study Type

Interventional

Enrollment (Actual)

25

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • Rhode Island
      • Providence, Rhode Island, United States, 02905
        • Women and Infants Hospital of Rhode Island

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

Female

Description

Inclusion Criteria:

  • Age 18 years or older
  • English speaking
  • Undergoing planned cesarean section at Women and Infants Hospital
  • BMI on admission less than or equal to 35 kg/m2
  • Preoperative hemoglobin greater than or equal to 11.5g/dL on routine labs

Exclusion Criteria:

  • History of allergy or other adverse reaction to adhesives
  • Fever at the time of recruitment

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Diagnostic
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: AccuFlow Sensor
These 50 patients will wear the AccuFlow sensor device during their surgery, and will complete the post-procedural survey. The data will be reviewed after 25 patients, and the pilot study may be stopped at that point if it is felt that the device feasibility and tolerability have been adequately established.
Device: AccuFlow sensor
AccuFlow sensor will be worn and survey completed
Other: Survey
Patients will be asked to complete a survey regarding device tolerability after completing their cesarean section.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Improving sensor design and analysis
Time Frame: 6 months
We will use the sensor readings obtained from this study to determine how best to obtain and analyze sensor readings in a larger trial. This will include comparing different ratios of readings (both different points in time during the case and different measurement sites on the patient) to determine the ideal number and locations of sensors, and ideal method of data analysis, for a larger trial.
6 months

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Device Tolerability
Time Frame: 6 months.
Patients will be asked to complete a survey after their cesarean rating the tolerability of the device, as well as the tolerability of standard anesthesia monitoring equipment (blood pressure cuff and pulse oximeter), to assess how the tolerability of the novel device compares to equipment already in use. This will be done in this way because although there is a validated scale for tolerability of wearable computer devices, this scale is only validated as a comparison between two options, and no absolute threshold below which a device is considered "tolerable" has been established.
6 months.
Accuracy
Time Frame: 6 months
We will compare the available device readings to the available lab measurements of hemorrhage, to determine if a difference is seen between patients with 10% blood volume lost vs 20% blood volume lost. This will assist in planning a larger trial by determining how many patients with higher-volume blood loss would need to be included, and therefore what total enrollment would likely be needed in the larger trial.
6 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Megan Lord

Collaborators

ThermaSENSE Corp

Investigators

  • Principal Investigator: Megan Lord, MD, Women and Infants Hospital of Rhode Island

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

May 20, 2020

Primary Completion (Actual)

February 25, 2021

Study Completion (Actual)

February 28, 2021

Study Registration Dates

First Submitted

April 27, 2020

First Submitted That Met QC Criteria

April 29, 2020

First Posted (Actual)

May 1, 2020

Study Record Updates

Last Update Posted (Actual)

July 13, 2021

Last Update Submitted That Met QC Criteria

July 10, 2021

Last Verified

July 1, 2021

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 1498912

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

No

IPD Plan Description

As this is a pilot study, we do not plan to make IPD available.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

Yes

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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