Tretti brystkompresjoner følges av to innblåsninger.

Because Norwegian very often forms compound nouns as a single word.

• bryst = chest
• kompresjoner = compressions

So brystkompresjoner literally means chest compressions.

This is very common in Norwegian. Where English often uses two words, Norwegian often prefers one:

• sykehus = hospital, literally sick-house
• førstehjelp = first aid
• brystkompresjoner = chest compressions

The -s here marks a passive form.

So følges av means something like:

• is followed by
• are followed by

In this sentence:

• Tretti brystkompresjoner følges av to innblåsninger = Thirty chest compressions are followed by two rescue breaths

This -s passive is very common in Norwegian, especially in instructions, formal language, and general statements.

Compare:

• Han følger meg = He follows me
• Han følges av vakter = He is followed by guards

Because the verb phrase here is følges av, which means to be followed by.

The preposition av is needed to introduce what comes next:

• følges av to innblåsninger = is followed by two breaths

This is similar to English followed by.

Compare:

• Middagen følges av dessert = The dinner is followed by dessert
• Applausen ble fulgt av stillhet = The applause was followed by silence

So av is not optional here.

In this sentence, the passive meaning is built into følges, so Norwegian does not need a separate are.

English says:

• Thirty chest compressions are followed by two breaths

Norwegian says:

• Tretti brystkompresjoner følges av to innblåsninger

The passive is already expressed by følges.

Norwegian can also form passives with bli or være, but the -s passive is especially common in short instructions and formal descriptions.

Innblåsninger refers to rescue breaths, the breaths blown into a person during CPR.

It comes from:

• inn = in
• blåse = to blow
• innblåsning = an insufflation / rescue breath
• innblåsninger = plural

A very literal sense is blowings-in, but in natural English CPR language, rescue breaths is usually the best translation.

Because the sentence is talking about multiple compressions and multiple breaths:

• tretti brystkompresjoner = thirty chest compressions
• to innblåsninger = two rescue breaths

In Norwegian, as in English, nouns after numbers greater than one are normally plural.

Singular vs plural:

• én brystkompresjon = one chest compression

• tretti brystkompresjoner = thirty chest compressions

• én innblåsning = one rescue breath
• to innblåsninger = two rescue breaths

Because after numbers, Norwegian normally just uses the number plus the noun.

So:

• tretti brystkompresjoner = thirty chest compressions
• to innblåsninger = two rescue breaths

You do not normally add an article there.

That is similar to English:

• We say thirty chest compressions, not the thirty chest compressions unless we mean some specific set already known from context.

Yes. This is a normal Norwegian sentence.

Structure:

• Tretti brystkompresjoner = subject
• følges = verb
• av to innblåsninger = prepositional phrase

So the basic order is:

Subject + Verb + Rest

That is completely standard in a main clause.

Yes. Norwegian has a few possible ways to express the same idea.

For example:

• Tretti brystkompresjoner blir fulgt av to innblåsninger.
• Etter tretti brystkompresjoner gis to innblåsninger.

But Tretti brystkompresjoner følges av to innblåsninger is concise, formal, and very natural in instructional language like first-aid directions.

Tretti is the standard Norwegian Bokmål form for thirty.

Some learners may also come across tredve, which exists as a variant, but tretti is the form most learners should recognize and use first.

So:

• tretti = thirty
• to = two

In this sentence, both numbers are simply functioning as determiners before plural nouns.