Repeated Orotracheal Intubation in Mice

Summary

The goal of this article is to describe a refined method of intubation of the laboratory mouse. The method is noninvasive and, therefore, ideal for studies that require serial monitoring of respiratory function and/or instillation of treatments into the lung.

Abstract

The literature describes several methods for mouse intubation that either require visualization of the glottis through the oral cavity or incision in the ventral neck for direct confirmation of cannula placement in the trachea. The relative difficulty or the tissue trauma induced to the subject by such procedures can be an impediment to an investigator’s ability to perform longitudinal studies. This article illustrates a technique in which physical manipulation of the mouse following the use of a depilatory to remove hair from the ventral neck permits transcutaneous visualization of the trachea for orotracheal intubation regardless of degree of skin pigmentation. This method is innocuous to the subject and easily achieved with a limited understanding of murine anatomy. This refined approach facilitates repeated intubation, which may be necessary for monitoring progression of disease or instillation of treatments. Using this method may result in a reduction of the number of animals and technical skill required to measure lung function in mouse models of respiratory disease.

Introduction

The laboratory mouse is a common animal model for human respiratory disease. Thus, there are several published methods for mouse intubation for the purpose of both instillation of treatments and measurement of respiratory mechanics. Most of the described procedures require visualization of the glottis through the oral cavity with specialized equipment such as a laryngoscope or fiber-optic light source^{1,2,3,4,5,6,7}. However, this can be di....

Protocol

All animal activities described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of The Ohio State University and were conducted in AAALAC-accredited facilities.

1. Procedure Preparation

1. Construct the intubation platform. To achieve the appropriate platform slope, use a three-inch (7.6 cm) 3-ring binder. Fold a 15−20 cm length of 3-0 silk or other thread material in half and adhere the ends of the thread to the top of the inclined platform with tape to create a suspension loop (Figure 1).
2. Select a cannula of the appropriate size and length.
   

Results

Serial monitoring of baseline pulmonary function
Eighteen-week-old female BALB/c and 10-week-old C57BL/6 mice (n = 3 of each strain) were intubated using the described method on day 0, 3, 10, and 17. Following intubation on each day, the subject was connected to a mechanical ventilator supplied with 100% oxygen (Table of Materials). Respiratory resistance (Rrs) was measured using the forced oscillation technique for 60 s following a deep inflation to 25 cm H₂O held for 5 s.......

Discussion

Intubation using the transcutaneous tracheal visualization technique offers a refined approach to the standard skin incision method. With special attention to several key steps, intubation can be easily and quickly achieved. The animal must be placed squarely in dorsal recumbency on the intubation platform with the mouse secured in gentle retraction. This will extend the animal into vertical alignment and proper positioning for intubation. In addition, the depilatory cream should not remain in contact with the animalR.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
18 G x 1 1/4" intravenous catheter, Safelet	Fisher Scientific	#14-841-14	Cannula for intubation
70% ethanol, 10 L	Fisher Scientific	25467025	Cleaning cannula
Abrasive paper (sandpaper)	Porter-Cable	74001201	Cannula preparation
AnaSed (xylazine sterile solution) injection (100 mg/mL)	Akorn Animal Health	NDC# 59399-111-50	Anesthesia
Blue labeling tape (0.5 in x 14 yds)	Fisher Scientific	15966	Restraint on intubation platform
Braided silk suture without needle, nonsterile, (3-0)	Henry Schein	Item #1007842	Intubation platform
Deltaphase Isothermal Pad	Braintree Scientific	39DP	Mouse thermoregulation and recovery
Deltaphase Operating Board	Braintree Scientific	39OP	Mouse recovery (prior to extubation)
Distilled water	ThermoFisher	15230253	Cleaning mouse following depilation
Eye Scissors, angled, sharp/sharp	Harvard Apparatus	72-8437	Cannula preparation
FlexiVent (FX Module 2)	Scireq	N/A	Record lung function data (not required to perform procedure, used in this study to validate procedure)
Gauze sponges	Fisher scientific	13-761-52	Hair removal
Heavy-Duty 3" 3-Ring View Binders	Staples	24690CT	Intubation platform
Instat Software	Graphpad	N/A	Statistical analysis software
Insulin syringe (0.5 cc, U100)	Fisher Scientific	329461	Anesthesia administration
Ketamine HCl Injection, USP (100 mg/mL)	Llyod Laoratories	List No. 4871	Anesthesia
Lung inflation bulb	Harvard Apparatus	72-9083	Confirm cannula placement
Micro Forceps, Curved, Smooth	Harvard Apparatus	72-0445	Retract tongue and create tension on neck for cannula visualization
Nair (hair removal lotion), 9 oz bottle	Church & Dwight	42010440	Hair removal
Sterile saline (0.9%), 10 mL	Fisher Scientific	NC9054335	Anesthesia, cleaning skin following hair removal