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CPR until ambulance comes: change and helpers

How do we split the CPR between us until the ambulance arrives?

Answer: When a heart stops, CPR must be given without breaks until the ambulance or a defibrillator takes over. Compressions get worse when people get tired, so the Danish First Aid Council recommends changing roughly every 2 minutes when there are several of you. Enter how many minutes you expect to wait for the ambulance, how many of you there are, and your rate. The calculator shows the number of changes, how many times each of you should step in, and how many compressions the patient receives in total. The wait time is your own estimate, e.g. from the emergency centre.

Formula

Skift = minutter til ambulancen ÷ skifteinterval, rundet op.

Gange pr. hjælper = skift ÷ antal hjælpere, rundet op.

One 30:2 cycle takes 30 ÷ (rate ÷ 60) sec + time for 2 breaths.

Kompressioner i alt ≈ ventetid i sek ÷ cyklustid · 30. Andel med kompressioner = kompressionstid ÷ cyklustid.

Symbols and units in the formula
SymbolMeaningUnit
minutterMinutes until the ambulance arrives (your estimate)min
hjaelpereNumber that can provide CPRpersoner
skift_minChange everymin
taktCompression strokekompr./min
indblaesningstidTime used on the 2 insufflationssek
=Total shiftsskift
=Times each helper must be on (max)gange
=Compressions in total (approx.)kompr.
=Share of time with compressions%

Validity and source

Source
Danish First Aid Council / ERC 2025: 30:2, rate 100-120/min, change helper approx. every 2 minutes

Does not apply when

  • The calculator is for practising and planning an emergency response. At an actual heart attack: call 112, start CPR immediately, and get a defibrillator. When the defibrillator arrives, follow its voice, and pauses for analysis come on top. If you are alone, you do not switch: continue as long as you can.

Worked example

The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.

Substituted

  • Minutes until the ambulance arrives (your estimate)10 min
  • Number that can provide CPR2 personer
  • Change every2 min
  • Compression stroke110 kompr./min
  • Time used on the 2 insufflations5 sek

Giver

  • Total shifts5 skift
  • Times each helper must be on (max)3 gange
  • Compressions in total (approx.)843 kompr.
  • Share of time with compressions77 %

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Sådan bruger du den

Ved hjertestop skal HLR fortsætte, til ambulancen overtager. I skal skifte ca. hvert 2. minut, så kvaliteten holdes. Beregneren viser, hvor mange skift det giver, og hvor mange gange hver af jer skal på.

Step by step

  1. Skøn hvor mange minutter ambulancen er om at komme.
  2. Tæl hvor mange der kan give HLR.
  3. Vælg skifteinterval og takt.
  4. Aftal rækkefølgen, før I starter.

Typical errors

  • At skifte for sjældent. Kompressionerne bliver dårligere efter ca. 2 minutter.
  • At holde lange pauser ved skiftet.
  • At glemme hjertestarteren. Den skal hentes med det samme.

Examples from everyday life

To kolleger på et lager

En kollega falder om på lageret. Vagtcentralen siger, at ambulancen er 10 minutter væk, og I er to.

Minutes until the ambulance arrives (your estimate)
10 min
Number that can provide CPR
2 people
Change every
2 min
Compression stroke
110 — mid-range
Time used on the 2 insufflations
5 sek

It means: Det bliver 5 shift i alt, og hver af jer skal på højst 3 times. Patienten får ca. 843 kompr. i alt.

Byggeplads på landet

På en byggeplads på landet er ambulancen 15 minutter væk. I er tre, I holder takt 100 og bruger 6 sekunder på indblæsningerne.

Minutes until the ambulance arrives (your estimate)
15 min
Number that can provide CPR
3 people
Change every
2 min
Compression stroke
100 — lower limit
Time used on the 2 insufflations
6 sek

It means: Det bliver 8 shift, og hver af jer skal på højst 3 times. 75 % af tiden går med kompressioner.

Fire førstehjælpere på kontoret

På et kontor er ambulancen 8 minutter væk, og fire førstehjælpere kan hjælpe.

Minutes until the ambulance arrives (your estimate)
8 min
Number that can provide CPR
4 people
Change every
2 min
Compression stroke
110 — mid-range
Time used on the 2 insufflations
5 sek

It means: Det giver 4 shift, så hver af jer skal kun på én gang. De andre henter hjertestarteren og tager imod ambulancen.

Rule of thumb

Skift hvert 2. minut. 10 minutter giver 5 skift.

How to check the answer

Gange pr. hjælper × hjælpere skal være mindst antallet af skift.