A PORTABLE HANDHELD OXYGEN BLENDER- A NOVEL DESIGN TO REDUCE EARLY OXYGEN TOXICITY

摘要

Oxygen is an essential therapeutic agent used extensively in all hospitals for patients with compromised function of the respiratory or cardiac systems. All patients (with the exception of neonates with certain heart diseases) are resuscitated with 100% oxygen. The American Heart Association Guidelines for Resuscitation state that it is essential in the post-resuscitative phase to decrease the concentration of O_2 provided to keep oxyhemoglobin saturation (SpO_2) > 94%, with a goal of avoiding hyperoxia while ensuring adequate oxygen delivery. Hyperoxia has been shown to be responsible for worsening tissue injury via oxidative damage following ischemia-reperfusion. Therefore, it is important in the post-resuscitative phase to use the lowest inspired oxygen concentration (FiO_2) that will maintain SpO_2 ≥ 94%. To address this, clinicians use oxygen blenders: devices that mix room air (21% O_2) and medical grade oxygen (100% O_2) to create a desirable FiO_2. Current oxygen blenders have the disadvantage of being wall-mounted, bulky, and are limited to a small set of oxygen delivery devices (nebulizers, mechanical ventilators) with which they can interface. We developed an oxygen blending device capable of mixing room air and 100% O_2 using the venturi principle. The device features a cylindrical body with a venturi nozzle and an entrainment window. It is handheld, portable, and machined from acrylic plastic. An oxygen blender with these features allows for appropriate oxygen therapy during patient transport. As oxygen flows through the device from the inlet orifice, atmospheric air is drawn in through the window, mixed, and then delivered to the patient through the outlet orifice. We designed the outlet orifice to have the same dimensions as the inlet orifice, allowing for universal integration with any device that connects to standard oxygen tubing. The entrainment window area can be adjusted by twisting a cover over the body of the blender, thus adjusting the FiO_2 delivery. Using a venturi nozzle of 6.35 mm in diameter and an entrainment window area of 97 mm~2, we achieved FiO_2 ranging from 40% to 50% using input flow of 100% O_2 at 6 L/min at 50 psi (via rotameter). The key feature of this device is that it can be interposed between any standard oxygen tubing allowing control of FiO_2 at the bedside of the patient in hospital or during transport. Further work is needed to achieve a wider FiO_2 range.