Published: March 21st, 2013
This paper describes a striaghforward and efficient method of intubating mice for pulmonary function measurements or pulmonary instillation, that allows the mice to recover and be studied at later times. The procedure involves an inexpensive fiberoptic light source that directly illuminates the trachea.
A simple procedure to intubate mice for pulmonary function measurements would have several advantages in longitudinal studies with limited numbers or expensive animal. One of the reasons that this is not done more routinely is that it is relatively difficult, despite there being several published studies that describe ways to achieve it. In this paper we demonstrate a procedure that eliminates one of the major hurdles associated with this intubation, that of visualizing the trachea during the entire time of intubation. The approach uses a 0.5 mm fiberoptic light source that serves as an introducer to direct the intubation cannula into the mouse trachea. We show that it is possible to use this procedure to measure lung mechanics in individual mice over a time course of at least several weeks. The technique can be set up with relatively little expense and expertise, and it can be routinely accomplished with relatively little training. This should make it possible for any laboratory to routinely carry out this intubation, thereby allowing longitudinal studies in individual mice, thereby minimizing the number of mice needed and increasing the statistical power by using each mouse as its own control.
In 1999, Brown et al. published a paper describing a method for intubation of the mouse lung 1. Such a technique has considerable utility in doing repeat pulmonary function or bronchoalveolar lavage in individual mice in longitudinal studies 2. Since that original paper, there have been several other papers that have described different approaches to mouse intubation 3-9. While all of these methods can be used successfully, they usually require considerable training or cost. One of the main issues with such intubation is that as the intubation cannula approaches nears the trachea pending insertion, the cannula itself ....
1. Preparing for the Procedure
One must first obtain and prepare the following items:
As an evaluation of the method, we used four 20 week old male BALB/c mice with average weight (± SEM) of 27.7 ± 0.40 g. They were studied on five consecutive weeks, where the lung resistance was measured using a system as previously described 11. Each mouse was anesthetized with ketamine (100 μg/g BW) and xylazine (15 μg /g BW) in saline via IP injection. They were then intubated as described above. If there is any doubt whether the cannula is in the trachea and not the esophagus, this can .......
The procedure described here has several advantages. First the apparatus is simple and relatively inexpensive.. The fabrication of the apparatus does not require any special tools or costly equipment. The use of a catheter introduces that also is the light source means that one never loses sight of the tracheal opening as the introducer approaches the tracheal opening. The use of a 0.5 mm introducer also serves to minimize trauma that might occur with an initial insertion of a larger cannula. We note here that a similar .......
|BD Insylte, Sparks, MD or Jelco Optiva, Carlsbad, CA
|1-in.-long, 20-gauge intravenous (IV) catheter
|Edmund Optics, Barrington, NJ
|Approximately 2-ft length of 0.5-mm optical fiber (Communication grade plastic fiber). The edge of the fiber end that is inserted into the trachea should be gently rounded by holding the fiber ≈2 cm from the end and then making small circles while dragging the tip for a few seconds on 1,000-grit emory paper.
|Although we use a 150-W halogen light source, any equivalent light source, even with much lower wattage can be used.
|Silicone rubber stopper
|A #1 silicone rubber stopper fits the light source used in this demonstration. Different light sources may require a different size.
|Small silicone rubber tube
|A ≈1.5 cm piece of silicone rubber tubing (0.8 inner diameter, 4 mm outer diameter)
|Angled support stand
|Ours is constucted from plexiglass, but any material to which a thread or wire can be affixed to hold the mouse at an almost vertical angle can be used.
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