(H-309) Liquid Flow Testing: Critical Characterization for Life-Saving Portable Suction Devices

Introduction:: Airway compromise is the second most common cause of preventable death on the battlefield, accounting for over 10% of total casualties. Portable suction devices are an important part of a combat medic’s airway management kit for addressing such injuries. These devices clear the airway by removing blood, vomit, teeth fragments, mud, and other life-threatening obstructions. Despite their life-saving capabilities, many combat medics and civilian first responders have decided not to carry them, because of their high weight (if electrically powered) and/or insufficient power (if manually powered). A major issue in the field is that manufacturer specifications for devices on the market are highly misleading. Commercially available suction devices like the Zoll 330, manufactured by Zoll Medical Corp, are used by the US Air Force and report a 4-hour battery life at “peak settings.” However, calculations on the pump and battery calls this manufacturer claim into doubt. We hypothesize that the Zoll suction device battery life at maximum power peaks is determined using air flow and not liquid flow, which does not reflect the conditions of the actual operational environment.


Materials and Methods:: A water flow test and an airflow test were conducted on the Zoll 330. For the water flow testing, the following components were used: Zoll as the suction source, a 1200 ml canister as a collector, a 2000 ml recipient as a reservoir, a liquid pump of 3.5 liters/min to remove water collected in the canister, and a hydrophobic filter as an exhaust to negate the suction added to the collector canister by the pump. To ensure liquid flow circulation between the components, a suction tubing of ID 6.15 mm was placed from the collector to the reservoir, and a discharge tubing of ID 9.2 mm was placed from the collector to the pump and from the pump to the reservoir. The different ID tubings were selected to balance inflow and outflow within the collector. A total of three trials were conducted, before each the device was fully charged and set to its peak power. During the test, the vacuum pressure and the time were recorded for every 10% drop of battery. For the airflow testing, one trial was conducted, occluding Zoll’s vacuum line at 550 mmHg to measure the discharge rate and compare it with the water flow results.


Results, Conclusions, and Discussions:: The results of the liquid flow tests revealed that at peak settings, Zoll’s battery discharge rate was 10% for every 15 min ± 1 min, and it took an average of 2 hours and 33 minutes ± 2 minutes for full battery discharge, as seen in Figure 1. After 1 hour of testing, the battery dropped to 65.33% ± 2.62%, and after 2 hours, it dropped to 23% ± 0.82%. In contrast, the airflow test showed that the battery discharge rate was 10% every 30 ± 3 minutes, and it took 4 hours and 48 minutes for full battery discharge, as seen in Figure 2.

The study has demonstrated that the hypothesis was correct, and the battery life presented in the user manual of Zoll was obtained using testing that was not relevant to the operational environment. Thus, it is recommended that suction devices be tested under more realistic scenarios so as not to mislead our first-responders in the field. Future work will focus on testing the device with liquids of higher viscosity similar to the body fluids to determine the variation with respect to water. This study highlights the need for increased standardization and regulation when it comes to operational claims of critical, life-saving medical technologies.


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