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Fig. 1
Schematic diagram of the operation of a vortex tube showing the flow inlet, the cold and hot air streams, and the cold and hot outlets.
Fig. 2
The adjustable cold air gun [15] incorporates a vortex tube to divide high pressure compressed air (1) into two low pressure streams, one hot and one cold by turning the fraction control valve (2) which allows hot air to flow through a muffling sleeve and out the hot air exhaust (3) while the cold airstream (4) is also muffled and discharges through the flexible hose. The swivel magnetic base (5) provides easy mounting and portability.
Fig. 3
Schematic representation of the cooling circuit used for nasal cooling showing the locations in the circuit where temperature and flow rate are measured.
Fig. 4
Brain and rectal temperature over time for nasopharyngeal cooling method at a flow rate of 25 L/min and temperature of −5°C ± 2°C at the cold air outlet. The compressed air was supplied from a hospital medical air outlet at fixed inlet pressure of 50 PSI into the vortex tube (Method I) (n = 1).
Fig. 5
Brain and rectal temperature over time for nasopharyngeal cooling method at a flow rate of 50 L/min and temperature of (A) 13°C ± 1°C, −3°C ± 1°C, −22°C ± 2°C and (B) −13°C ± 3°C at the cold air outlet. The compressed air was supplied from medical air cylinders (Method II) at variable inlet pressure of (A) 10, 25 and 50 PSI (all three conditions were applied on the same pig, n = 1) (B) 35 PSI (n = 1).
Fig. 6
Brain and rectal temperature over time for nasopharyngeal cooling method at a flow rate of 50 L/min with an average air temperature of 6°C ± 5°C at the cold air outlet throughout the experiment. The compressed air was supplied from scuba diving cylinders (Method III) at inlet pressure of 25 and 15 PSI (n = 1).
Fig. 7
Changes in the brain-rectal temperature over time by setting the cold air flow rate from the vortex tube to 25 L/min for nasopharyngeal cooling using (A) nasal catheters and (B) the face mask. The average air temperature at cold air outlet was −7°C ± 2°C. The compressed air was supplied to the vortex tube at an inlet pressure of 25 PSI from a medical air tank (n = 1).
Abstract
Vortex tubes are simple mechanical devices to produce cold air from a stream of compressed air without any moving parts. The primary focus of the current study is to investigate the feasibility and efficiency of nasopharyngeal brain cooling method using a vortex tube. Experiments were conducted on 5 juvenile pigs. Nasopharygeal brain cooling was achieved by directing cooled air via a catheter in each nostril into the nasal cavities. A vortex tube was used to generate cold air using various sources of compressed air: (I) hospital medical air outlet (n = 1); (II) medical air cylinders (n = 3); and (III) scuba (diving) cylinders (n = 1). By using compressed air from a hospital medical air outlet at fixed inlet pressure of 50 PSI, maximum brain-rectal temperature gradient of −2°C was reached about 45–60 minutes by setting the flow rate of 25 L/min and temperature of −7°C at the cold air outlet. Similarly, by using medical air cylinders at fill-pressure of 2265 PSI and down regulate the inlet pressure to the vortex tube to 50 PSI, brain temperature could be reduced more rapidly by blowing −22°C ± 2°C air at a flow rate of 50 L/min; brain–body temperature gradient of −8°C was obtained about 30 minutes. Furthermore, we examined scuba cylinders as a portable source of compressed gas supply to the vortex tube. Likewise, by setting up the vortex tube to have an inlet pressure of 25 PSI and 50 L/min and −3°C at the cold air outlet, brain temperature decreased 4.5°C within 10–20 min.
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☆Conflicts of Interest: MFB, LK, and T-YL are inventors on patent application PCT/CA2015/050,216 submitted on March 4, 2013, describing the selective brain cooling method.
☆☆Sources of Funding: Lawson Health Research Institute.
