‘WASAP’: WARM as soon as possible - A low-cost instant blood warmer based on dual tube heat exchanger and nanofluid technology

Dear Editor, Warm fluids and blood prevent hypothermia and hypotension in patients.[1,2] Commercial warming devices like blood bathing units and inline fluid and cabinet warmers operate based on dry heat exchangers and countercurrent mechanisms. The cost factors remain a limitation for using these devices in health facilities with limited resources. We have made a low-cost, blood/fluid warmer based on the principle of a dual tube heat exchanger, utilising a passive heat exchange mechanism for heat transfer.[3] The materials for making the warmer included (i) an outer tube made of a 1-L intravenous (IV) bottle, (ii) an inner tube with corrugations, (iii) a double-sided copper tape for taping the inner tube, (iv) a high-butyl polymer rubber coated with aluminium for taping the outer tube, (v) a three-way stop cock, (vi) two epidural needle sheaths/caps, (vii) an endotracheal tube connector, (viii) two submersible aquarium thermometers and (ix) aluminium oxide nanoparticles. These are assembled as shown in Figure 1, and the steps are as follows. Step 1: The outer tube has two openings: a) an inlet, made of a three-way stop cock connected to an epidural sheath located inside the outer tube for infusing preheated IV fluid (about 45°C to 50°C) which will heat the outer tube and b) an endotracheal tube connector fixed in the outer tube has four functionalities: (i) for the insertion of thermometer probe to sense the outer tube fluid temperature, (ii) to suction dewarmed fluid, (iii) to infuse nanofluid and (iv) to create turbulence with air-filled syringe to aid active heat transfer. Step 2: The outer tube heated by a passive transfer mechanism will increase the temperature of the inner tube, which will be recorded using a probe inserted at the exit of the inner tube. The inner corrugated tube is taped with copper, and the outer tube is taped with highly heat-resistant (-30°C–120°C), aluminium-coated, high-butyl polymer rubber to enhance the heat transfer rate and efficiency. In the outer tube, the hot fluid is mixed with nanoparticles, namely, aluminium oxide, a metallic oxide. Nanofluids enhance their heat capacity, thermal conductivity, turbulence, and fluctuations when introduced to a fluid.[4] The blood transfusion set is heated as it travels from one end of the tube to the other, and a second temperature probe is attached to the transfusion set at the inner tube's exit records.Figure 1:: Warm As Soon As Possible 'WASAP' warming device. DTHE: Dual tube heat exchanger, Al2O3: Aluminium oxide, IV:IntravenousThe benefits of 'WASAP' are that no current is used in this, it is cost-effective, and its temperature regulation, simple maintenance, and reusability. Integrating innovative ideas based on scientific principles to cater to low-resource healthcare settings will make us self-reliant.[5] Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.