The whole idea behind intranasal treatment is the fact that the ears are connected to the back of the nose via a tunnel called the eustachian tube. Watch video explanation.
Normally, when the ears are popped (also known as valsalva), the individual is opening up the eustachian tube to allow pressure and/or fluid in the ears to drain/escape out into the back of the nose. That's why when you blow your nose, you often hear a popping noise in the ears. Read more about how/why this happens here.
Patients suffering from eustachian tube dysfunction are unable to get the tunnel to open up. In this scenario, the pressure or fluid remains trapped in the ear. It's a plumbing problem in its essence.
Given the problem is the eustachian tube, intranasal medications are used to try and open up the tunnel and make it easier for the individual to pop the ears open.
Trick is... how to get the intranasal medications to where the eustachian tube is located in the very back of the nose.
There are a few ways to accomplish this... some which work better than others.
Use a nasal spray medication and aim the bottle to the back of the neck while keeping the head down (looking at the floor). The spray bottle MUST be perpendicular to the face. Why? Take a look at the diagram below:
If you aim the bottle towards the eye or top of the head, the medication is hitting areas of the nose where the sinus cavities are... not where the eustachian tube is located.
You have to look down and point the nasal spray bottle up towards the ceiling because all nasal spray medications use a straw that requires vertical orientation (same reason why when you drink Pepsi from a cup, the cup is upright).
Anatomically, the nasal spray "shoots" the medication straight up to where the eustachian tube is located.
Use an eye dropper and place a drop of the medication into the nose and have it "drain" to where the eustachian tube is located. Practically, this means filling a prescription of the nasal spray medication, opening up the bottle, and pouring the contents into an eye dropper.
This method requires positioning the head such that gravity will ensure proper movement of the medication to where the eustachian tube is located.
There are two ways to achieve this. This first way is the "Head-Tipped-Back Position".
In this position, the nasal drop will "fall" down to where the eustachian tube is located:
Techniques of Intranasal Steroid Use. Otolaryngol Head Neck Surg 130(1):5-24.
Intranasal delivery of drugs to eustachian tube orifice. The Journal of Laryngology & Otology (2011), 125: 934-939
Images taken from Techniques of Intranasal Steroid Use and Wikipedia.