Hello, I think that I would not rely on medical protocols from most of Eastern Europe, unless it was an actual University Hospital - they are not known for advanced medical practice. In the US and most countries, pulmonologists use a bronchoscope, with a camera at the end, to examine lungs and retrieve specimens. The patient is sedated for the procedure.

Using the method you describe to "suck from the lower airways" is very risky- below are diagrams of human lung. To reach the carina, you must safely insert the tube through the trachea, and a bad intubation can cause a great deal of damage. At that point, you might retrieve mucus from the bronchi, but any strong suction risks damaging the very delicate alveoli (tiny air sacs in the lung tissue.)

That would not be the same as NTS, where the device is only inserted to the back of the throat and is unlikely to retrieve mucus from the lungs.

It is done in USA in ICU’s and also done on long term and some home ventilator patients, but it has to be done with care and by trained staff or trained providers due to risk of infection, bleeding, etc.
As I said above, I can’t imagine a person being able to do it on their own. The body has a very strong cough reflex and unless you were extremely ill, you’d be coughing that catheter out before it got very far. It would be more likely to go into esophagus than trachea.
I worked in Critical Care for about 20 years (last century 😀) and we did it often for those too sick/sedated to cough sputum out. It’s not a pleasant experience for patients or staff.
As Sue mentioned, bronchs are done with suction to get specimens from lung.