AS NZS ISO 11990:2002 pdf free.Optics and optical instruments—Lasers and laser-related equipment—Determination of laser resistance of tracheal tube shafts.
5.2 A large number and range of variables are involved in laser ignition of a tracheal tube. A change in one variable may affect the outcome of the test. Caution should be observed, since the direct applicability of the results of this test method to the clinical situation has not been fully established.
5.3 Since it is conceivable that an oxygen-enriched atmosphere may be encountered in the clinical situation, either intentionally or unintentionally, the test is performed in a environment of (98 ± 2) % oxygen.
5.4 A flowrate of 1 litre/mm in a 6,0 mm inner diameter tube was chosen as the best conditions for tube ignition and establishment of a fire based on studies detailed in [1] (see Bibliography).
5.5 Opportunities for development: variations of this method can be applied to study the effect of changing the test conditions, but are outside the scope of this test method. For example, variation of the breathing-gas flowrate or different breathing-gas mixtures may affect the laser resistance of the tracheal tube. Use of beam cross-sectional areas other than circular or modes of laser power delivery other than continuous, e.g. pulsed, superpulsed, Q-switched, ultrapulsed, may alter the tracheal tube’s ignition characteristics. Also, tubes of different diameter will have laser resistances different from that defined in this International Standard (see [2] to [5] in the Bibliography).
6 Apparatus
6.1 Gas supply system
6.1.1 The gas supply system shall provide oxygen to the tracheal tube at a controllable flowrate. Also, the system shall be capable of rapidly flooding the containment box with nitrogen or other inert gas and/or stopping oxygen flow, or both, to extinguish any burning material. An oxygen flow control and flow meter and a quick-action inert gas valve should be part of this system (see Figure 1). The nitrogen or inert gas supplied should be at a higher pressure and allow a flowrate at least an order of magnitude greater than that of the oxygen supplied to the tracheal tube.
6.1.2 Other arrangements, such as an oxygen flood valve for rapidly purging the containment box or an inert gas flooding system for rapid extinguishment of burning material, may be made as long as the requirements of the test method as defined herein are not affected.
6.2 Containment box
6.2.1 The containment box is a means to control the environment around the test specimen while allowing access for the laser delivery system to the test unit (see Figure 2).
6.2.2 The typical containment box shall have the following characteristics:
a) allows direct access of the laser power to the entire length of the tracheal tube shaft;
b) supports the shaft of the tracheal tube 7 cm to 10 cm below the opening for laser access, as shown in Figure 2;
c) maintains an environment of at least 96 % oxygen around the tracheal tube;
d) exhausts the gas flowing through the tube and any products of combustion to a safe area;
e) is fireproof and easily cleaned of soot and residue from burned tracheal tubes;
f) is a rectangular parallelepiped approximately 46 cm x 46 cm x 15 cm;
g) has transparent, non-flammable enclosure covers that are positioned on top of the box to allow visibility of and access to the test unit while maintaining the test environment. The covers shall be able to define an opening of 38 cm2 to allow laser access to the test unit. The covers shall be easily removable for access to the test unit, cleaning of the box, and cleaning of the covers themselves;
h) can be rapidly flooded with nitrogen or other inert gas to extinguish any fire inside the box;
i) the top shall be covered with appropriate filter media to protect from reflections.AS NZS ISO 11990 pdf download.