Clinical Notes : Resuscitation

91. Basic Life Support (BLS)



Some countries have a survival rate following out of hospital cardiac arrest of 5% while other countries have a survival rate

as high as 30%. 

Countries with the best outcome have raised national cardiac arrest awareness and have embedded Chain of Survival in their emergency response protocols, so that more bystanders and first responders are able to deliver effective CPR.


In out-of-hospital cardiac arrest, ALS care (Advanced Life Support) is associated with increased ROSC (Return of Spontaneous Circulation), but is not associated with greater functional outcome than BLS care alone .


BLS Adult Cardiac Arrest Algorithm (2015 AHA)

Verify scene safety

Make sure you, the adult and any bystanders are safe




Assess Responsiveness + Get Help


Stimulate and speak to the adult asking if they are ok. Look at the chest and torso for movement and normal breathing.


If responsive:

  • Leave him in the position in which you find him, provided there is no further danger

  • Try to find out what is wrong with him and get help if needed

  • Reassess him regularly

If unresponsive:

  • (One provider) first call the emergency response team and bring an AED to the patient.

  • (Two providers) Have someone near call the emergency response team and bring the AED.

Place the adult supine on a hard flat surface.



Assess for pulse and breathing

Check the adult for a carotid pulse and breathing simultaneously for 5-10 seconds.

Do not check for more than 10 seconds

  • Airway

    • Ensure open airway (jaw thrust or head-tilt-chin-lift)

  • Pulse

    • the carotid pulse (or any other pulse) is an inaccurate method for confirming the presence or absence of circulation

    • assume that the adult who is breathing normally has a pulse

  • Breathing

  • Agonal breathing (or gasping) may be present in up to 40% of adults in the first minutes after cardiac arrest

  • can be interpreted incorrectly as evidence of a circulation and that CPR is not needed



Normal breathing and has a pulse :​

  • Activate emergency response system and retrieve AED

  • Return to the adult and monitor until emergency service arrives


No breathing and has a pulse :​​

  • Breathing

    • Commence rescue breaths immediately.​

    • After 2 min, activate emergency response system and retrieve AED

    • Return to adult and resume rescue breaths 

    • After 2 min, check pulse​

      • if no pulse, start CPR

    • If possible opioid overdose, administer Narcan​ if available


No breathing (or gasping only) and no pulse :​​

  • Start CPR

 CPR  ( Cardio Pulmonary Resuscitation)


  • Place adult supine on a hard flat surface

  • One provider 

    • Give 2 minutes of CPR with cycles of 30 compressions to 2 breaths

    • Use the AED as soon as it is available

  • Two providers 

    • Second provider calls the emergency response team and brings the AED

    • First provider begins cycles of 30 compressions to 2 breaths


If the adult regains a pulse :

Return to the Airway and Breathing portion of the algorithm:

  • Provide 10-20 rescue breaths per minute (1 breath every 3-6 seconds).

  • Recheck pulse every 2 minutes.

If the adult does not regain a pulse :

Continue in the Circulation portion of the algorithm



Chest compressions:

  • Provide 100 to 120 compressions per minute. This is 30 compressions every 15 to 18 seconds.

  • Place your palms midline, one over the other, on the lower 1/3 of the adult’s sternum between the nipples.

    • Lock your arms.

  • Using two arms press to a depth of 5-6 cm (2 to 2.4 inches) or more on the adult’s chest.

    • Press hard and fast.

  • Allow for full chest recoil with each compression.

  • Allow for only minimal interruptions to chest compressions.


1 cycle of adult CPR is 30 chest compressions to 2 rescue breaths.
If two providers are present: switch roles between compressor and rescue breather every 5 cycles.

Hand Placement

Arrange the heel of your hand directly over the heel of your other hand. Interlace your fingers.

Place the heels of your hands over the center of the adult's chest on the lower half of their sternum.

Arm Alignment

Keep both of your arms straight with your elbows fully extented.

Position your shoulders directly above your hands and the adult's chest.

Compression Depth & Rate

Chest compressions should be at a depth between 2 to 2.4 inches (5 cm to 6 cm) and at a rate of 100 to 120 per minute.

2015 to 2020

Quality chest compressions

  • depth : at least 5 cm in the adult, not to exceed 6cm (2 to 2,4 inches)

  • rate : between 100 and 120 compressions per minute

  • allow for complete chest recoil


Minimize chest compression interruption

  • Compression fraction is the time spent actually compressing the chest.

  • Compression fraction : 60% (Within 1 minute, 60% of that 1 minute, at least, should be spent actively doing chest compressions)



In the event of an unwitnessed collapse, drowning, or trauma:

Use the Jaw Thrust maneuver. (This maneuver is used when a cervical spine injury cannot be ruled out.):

  • Place your fingers on the lower rami of the jaw.

  • Provide anterior pressure to advance the jaw forward.


(Use in place of head-tilt/chin-lift if neck injury is suspected)

Place your index fingers behind the angles of the adult's jaw.

Provide upward pressure to lift the adult's jaw while avoiding any neck movement.

In the event of a witnessed collapse with no reason to assume a C-spine injury :

Use the Head Tilt-Chin Lift maneuver:

  • place your palm on the adult’s forehead and apply pressure to tilt the head backward.

  • place the fingers of your other hand under the mental protuberance of the chin and pull the chin forward and cephalic.


Head-tilt / Chin-lift

Using one hand, place downward pressure on the adult's forehead.

Using your other hand, place two fingers below the edge of the adult's chin and provide upward rotating pressure to tilt the head back.



If the adult is breathing adequately:

Continue to monitor and maintain a patent airway and place the adult in the recovery position.

(Only use the recovery position if its unlikely to worsen patient injury.)

If the adult is not breathing or is breathing inadequately:

  • If the adult has a pulse:

    • Commence rescue breaths immediately.

  • If the adult has no pulse:

    • Begin CPR. (move to the “Circulation” portion of the algorithm.)

Rescue Breaths

  • Use a barrier device if available.

  • Pinch the adult’s nose closed.

  • Make a seal using your mouth over the mouth of the adult or use a pocket mask or bag mask.

  • Each rescue breath should last approximately 1 second.

  • Watch for chest rise.

  • Allow time for the air to expel from the adult.

Rescue Breaths

Pinch the adult's nose using the hand that is resting on the adult's forehead.

Make a complete seal over the adult's mouth.

Use a barrier if available.

Give a full deep breath to the adult lasting approximately 1 second.

Watch for chest rise.

Rate of breathing :

  • During normal CPR without an advanced airway:

    • Provide approximately 6-8 rescue breaths per minute

  • During normal CPR with an advanced airway:

    • Provide 10 rescue breaths per minute (don’t pause chest compressions for breaths).

  • If adult has a pulse and no CPR is required:

    • Provide 10 rescue breaths per minute (1 breath every 6 seconds).

    • Recheck pulse every 2 minutes.

2015 to 2020

Avoid gastric insufflation

  • Excessive breaths and excessive tidal volume can increase intrathoracic pressure and reduce blood return to the heart.

  • Excessive tidal volume can push air into the stomach leading to vomiting and aspiration.

  • The average volume of an Ambu bag 1400 cc to 2000 cc. The required tidal volume to be delivered per breath is 500 cc. administered over a period of 1 second.



If there is a foreign body obstruction:

  • Perform abdominal thrusts


Recovery position (lateral recumbent or 3/4 prone position):

This position is used to maintain a patent airway in the unconscious person who is breathing adequately

  • Remove the adult’s glasses, if worn

  • Kneel beside the adult and make sure that both his legs are straight

  • Place the arm nearest to you out at right angles to his body, elbow bent with the hand palm-up

  • Bring the far arm across the chest, and hold the back of the hand against the adult’s cheek nearest to you

  • With your other hand, grasp the far leg just above the knee and pull it up, keeping the foot on the ground

  • Keeping his hand pressed against his cheek, pull on the far leg to roll the adult towards you on to his side

  • Adjust the upper leg so that both the hip and knee are bent at right angles

  • Tilt the head back to make sure that the airway remains open

  • If necessary, adjust the hand under the cheek to keep the head tilted and facing downwards to allow liquid material to drain from the mouth

  • Check breathing regularly

  • Assure the position is stable.

  • Avoid pressure of the chest that could impairs breathing.

  • Ensure there is no obstruction to turning the adult back to supine position if necessry

  • Take precautions to stabilize the neck in case of cervical spine injury.

  • Continue to assess and maintain access of airway.

  • Be prepared to restart CPR immediately if the adult deteriorates or stops breathing normally

2015 to 2020

Cricoid pressure during positive pressure ventilation

  • No longer recommended

Heroin or opioid overdose

  • Potent respiratory depressants leading to respiratory arrest and consequent cardiac arrest.

  • Administer naloxone

  • 2 mg through an intranasal auto-injector or 0.4 mg intramuscular

  • May repeat after 4 minutes