Intrabronchial Delivery: A Technique to Administer an Experimental Agent Selectively Into a Mouse Lung

Overview

This video describes an intrabronchial approach to administer an experimental agent selectively into distal right and left lung. In the featured protocol, we will administer bleomycin intrabronchially into a mouse to obtain a better model for pulmonary fibrosis.

Protocol

All procedures involving animals have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.

1. Non-operative IB intubation and delivery approaches

1. IB approach to selective lobar cannulation of the distal right lung
   1. After performing intratracheal (IT) cannulation (use the dominant hand to intubate the extended catheter into the trachea via the oral cavity), rotate the plastic board +30° (Figure 1A).
   2. Hold the hub of the catheter and guide it naturally in parallel to the mouse midline, extending it to weight-based depths as described in Table 1.
      NOTE: The resistance at these depths should be noted. At this point, the mouse will become slightly tachypneic, as explained in the representative results. For an experienced operator, approximately 90% of attempts will successfully cannulate the right lung (with tachypnea noted).
   3. Deliver 20 µL of 0.3% Evans blue dye (EBD, see Table of Materials) with a gel loading tip.
   4. Dispense 1–2 aliquots (0.1 mL each) of air by using the glass dropper.
      NOTE: This ensures clearance of the residual EBD solution (or experimental agents) from inside of the catheter.
   5. Withdraw the catheter, then maintain the mouse position for 30 s.
   6. Place the animal on a warming blanket until it regains consciousness. Recovery is typically complete within 2 min.
2. IB approach to selective segmental cannulation of the distal left lung
   1. After performing IT cannulation (use the dominant hand to intubate the extended catheter into the trachea via the oral cavity), rotate the plastic board -74° (Figure 1B).
   2. Hold the hub of the catheter and apply gentle pressure to advance the catheter into the left mainstem bronchus, while placing modest pressure both downwards (90°) and towards the bookend. At depths noted in Table 1, the operator should note resistance as the lower segments of the left lung are engaged. If tachypnea occurs, withdraw the catheter to the 20–25 mm position, and reattempt.
   3. After cannulating the left lower lung segments, a change in position is required to allow gravitational assistance for agent administration. Rotate the plastic board -30° (Figure 1B).
   4. Deliver 40 µL of 0.3% EBD with a gel loading tip.
      NOTE: It is feasible to deliver a larger volume of agent because the left lung has only one lobe.
   5. Dispense 1–2 aliquots (0.1–0.3 mL each) of air using the glass droppers.
      NOTE: This ensures clearance of any residual EBD (or experimental agents) from inside of the catheter.
   6. Withdraw the catheter, then maintain the mouse position for 30 s.
   7. Place the animal on a warming blanket until it regains consciousness. Recovery is typically complete within 2 min.

Representative Results

Figure 1: Approach for selective right/left lung lobar cannulation and administration. (A) To target the right lung, the plastic board is rotated +30°, improving ease of selectively engaging the right mainstem bronchus. The catheter is advanced (per distances proposed in Table 1) to selectively engage right sided lobes. 20 µL of 0.3% EBD was administered. In ~90% of attempts, the posterior lobe is cannulated. The remaining 10% of attempts engage the inferior lobe. (B) To target the left lung, the plastic board is first rotated -74° for left mainstem engagement. After successful intubation of the catheter, rotation is then decreased to -30° to allow for gravity to assist with agent delivery. To prove selective engagement of the left side, 40 µL of 0.3% EBD was delivered. This approach consistently (100% of attempts) targeted left lung basilar segments.

Body weight (g)	Number of mice tested	Catheter depth (mm) for Selective cannulation		Catheter depth (mm) for whole lung cannulation
		Right lung	Left lung
15 - 19	17	37	38	26
20 - 25	22	38	39	27
25 - 30	29	39	40	28
> 30	11	40	41	31

Table 1: Suggested depth of catheter insertion. Predicted catheter depths necessary to selectively cannulate the distal and proximal lungs were empirically determined using C57BL/6 mice of various weights (total = 79 mice).

Materials

Name	Company	Catalog Number	Comments
22 G shielded IV Catheter	BD	381423
Evans blue dye	Sigma-Aldrich	E2129
LED-30W Fiber Optic Dual Gooseneck Lights Microscope Illuminator	AmScope	LED-30W
Precisionglide needle, 18G x 1"	BD	305195	Beveled tip, 12 mm in length