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    Device Technologies and Biomedical Robotics

    (E-179) Can Backflow Exist in a Medical Aspirator - Portable Suction Devices

    Thursday, October 12, 2023
    2:00 PM – 3:00 PM PDT
    Location: Exhibit Hall - Row E - Poster # 179
    Introduction:: : Suction devices, also known as aspirators, are medical instruments used to remove fluids from a patient's airway or wounds. In airway management, suction devices are among the first equipment used to treat a patient with traumatic injuries. Airway compromise is a major problem in civilian emergencies and the second leading cause of potentially survivable battlefield injuries among US military forces. However, many commercially available portable suction devices have not been scientifically validated for performance measures relevant to prehospital care. The current standard used to measure the performance of portable suction devices is ISO 10079-1. However, the standard's maximum free air flow rate of 20 L/min is confusing since the device's intended use is to suction viscous liquids. This is problematic since manufacturers primarily use this metric to report performance, which can be misleading and overestimate the device's real-world capability. Furthermore, the standard also requires the evacuation of 200 ml of simulated vomitus in not more than 10 seconds but does not include requirements for avoiding backflow of liquid into the patient's mouth, which poses a significant risk of lung infection. To test the hypothesis that time-averaged air flow rate is a better estimate of overall device performance than peak instantaneous air flow rate, four market-leading portable suction devices, weighing less than 1.5 kgs, were selected and tested based on various metrics, such as instantaneous air flow rate, liquid flow rate, vacuum pressure, and backflow.

    Materials and Methods::

    This study tested four portable suction devices using an experimental setup that selected devices based on their frequency of use and weight (less than 1.5 kg) among first responders. Two of the devices were battery-operated (Laerdal LCSU 4 and SSCOR Quickdraw), and two were manually operated (V-VAC and AMBU RES-QUE). The air flow rate of each device was measured by operating the device against a microelectromechanical system (MEMS) air flow sensor to record the instantaneous air flowrate. This was done for all four devices, with each device being tested for 30 seconds at 100 Hz. To measure the liquid flow rate, the volume of liquid (water and ISO vomit solution) that each suction device evacuated from a beaker filled with liquid was calculated. A pressure transducer was attached to the suction tube tip to measure the vacuum pressure during the suction process. The amount of liquid evacuated was measured by tracking the weight of the beaker filled with liquid in real-time using a MATLAB timer. All suction devices were tested until their respective canister capacity was reached, and each device was tested five times at its peak setting. For manually operated suction devices, a single operator operated devices for all five trials. The data collected from the sensors was analyzed using MATLAB and processed using a Digital Acquisition System (DAQ). Overall, this study aimed to evaluate and compare the performance of different portable suction devices and provide useful information for first responders when choosing the appropriate device.


    Results, Conclusions, and Discussions:: Results: Figure 1 presents a comparison between the peak air flowrate, total averaged air flowrate, and manufacturer-claimed peak air flowrate of all four suction devices. Peak air flowrate refers to the highest air flowrate the device can reach during operation, while time-averaged air flowrate refers to the total amount of air evacuated by the suction device over 60 seconds. The figure 2 compares the liquid flowrates of the four suction devices when used with two different liquids: water (µ = 1 cp) and ISO vomit solution (µ = 22cp). Figure 3 shows the instantaneous flowrates of simulated vomitus over time.


    Discussions: Figure 1 compares the total and instantaneous air flowrate of manual suction devices. Instantaneous air flowrate is high, but the time-averaged air flowrate for 60 seconds is much lower. Peak air flowrate is not a useful specification because it does not necessarily correlate with liquid flowrate, which is much closer to a real-world performance metric. Use of the peak (maximum) air flowrate metric allows the manually operated suction devices to claim misleading comparison to performance to their battery-powered counterparts. Time-averaged airflow rate for 60 seconds is a more reliable specification, albeit still limited as it does not reflect the intended use of the device to suction liquids. Backflow in a device to evacuate liquids has potential consequences. The VVAC demonstrated backflow on the order of 2-5% overall.


    The catheter tip is likely in the oropharynx during use, and the patient likely has impaired pulmonary clearance in the first place, the backflow presents risk. Further study is needed to determine the amount of backflow, if any, that could reach the lungs (pulmonary aspiration), and the downstream consequences in terms of patient outcomes.

    Conclusion: Peak average airflow rates show considerable variability among and within devices and is not likely a useful metric for suction devices designed to move liquids. Liquid flowrates show variability between models and differ whether water or simulated vomitus is moved. At least one device, a manual-powered model, showed backflow. Further study is needed to determine patient outcome effects.


    Acknowledgements (Optional): : The authors acknowledge funding support from the Excitus, AS, Hillevågsveien, Norway. Authors (RAD and RLH) are principals in EmergenceMed, LLC., Texas, USA.


    References (Optional): :