Table 4. Summary of interventions for the quality of bystander cardiopulmonary resuscitation in the included studies.

Modifications to DA-CPR
Modified telephone DA-CPR instructions
Added instructions with speakerphone activation, removing obstacles and continuous instruction [27]	Improved CPR quality, but longer time to first chest compression
Simplified compression only-CPR protocols [34,40]	Improved CPR quality and shorter time to first chest compression
Instructions with“push as hard as you can” [37]	Improved compression depth compared to instruction with “push down firmly 2 inches”
Modified instructions using arm and nipple line [41]	Improved hand position
Elimination of the instruction to remove the victim’s clothing [52]	Shortened time to first compression without affecting CPR quality
Novel protocols with changing instructional content of hand position, compression depth and compression rate at the same time [33]	Improved CPR quality compared to standard protocol
Added instructions with “put the phone down” [22]	Similar CPR quality compared to instruction without “put the phone down”
Instructions with repeated or intensified wording to remind of or emphasize the importance of chest compression depth [26]	Similar CPR quality compared to standard instruction
Instructions with “push as hard as you can” for paediatric CPR[35]	Similar CPR quality compared to instruction with “push down approximately 2 inches”
Video-assisted DA-CPR
Video-conferencing DA-CPR [17,20,28,39,46]	Improved CPR quality in 4 studies [17,20,28,39]; no improvement in 1 study compared to telephone CPR [46] Longer time to first chest compression/rescuer breathing in 3 studies [20,28,39]; similar time to first chest compression [17,46] compared to telephone CPR
Showing a video on cellular phone when performing CPR [50]	Improved CPR quality and shorter time to first chest compression compared to telephone CPR
Playing metronome sounds to the rescuer by the dispatcher [21, 58]	Improved chest compression rates, but tended to shallow compressions
Different methods of performing CPR
Compression-only CPR [18,25,32,42,44]	Improved CPR quality compared to conventional CPR in 5 studies [18,25,32,42,44] Easy physical fatigue in 2 studies [18,32], but similar fatigue in 3 studies [25,42,44] compared to conventional CPR
Dominant hand against the chest wall [36]	Similar CPR quality when compared to non-dominant hand against the chest wall
Two rescuers on the opposite sides [47]	Reduced hands-off time compared to two rescuers at the same side
Four-hand CPR [30]	Improved chest compression depth compared to two-hand CPR
CPR with heels [24]	Improved chest compression depth compared to CPR with hands
Additional aids to bystander CPR
Telephone DA-CPR [23,29,31,48,49]	Improved CPR quality compared to no telephone DA-CPR
Simple basic life support flowchart [51]	Improved CPR quality compared to no such flowchart
Basic life support software programs on a mobile phone with a metronome function [43]	Improved CPR quality, but longer time to first chest compression compared to no such software program.
Newly-developed CPR support applications on a mobile phone [19]	Increased number of total chest compressions, but longer time to start compressions or ventilations compared to no such application
Real-time feedback devices [38,42,45,54–57]	Improved CPR quality compared to no such application.
Pneumatically powered transport ventilators [53]	Improved ventilation quality compared to bag-valve mask

CPR: cardiopulmonary resuscitation; DA-CPR: dispatcher-assisted cardiopulmonary resuscitation.