Does timing have anything to do with it?

all of the 2005 american heart association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care are available on line.

the following was taken from part 3: overview of cpr:

healthcare providers should deliver cycles of compressions and ventilations during cpr when there is no advanced airway (eg, endotracheal tube, laryngeal mask airway [lma], or esophageal-tracheal combitube [combitube]) in place. once an advanced airway is in place for infant, child, or adult victims, 2 rescuers no longer deliver "cycles" of compressions interrupted with pauses for ventilation. instead, the compressing rescuer should deliver 100 compressions per minute continuously, without pauses for ventilation. the rescuer delivering the ventilations should give 8 to 10 breaths per minute and should be careful to avoid delivering an excessive number of ventilations. the 2 rescuers should change compressor and ventilator roles approximately every 2 minutes to prevent compressor fatigue and deterioration in quality and rate of chest compressions. when multiple rescuers are present, they should rotate the compressor role about every 2 minutes. the switch should be accomplished as quickly as possible (ideally in less than 5 seconds) to minimize interruptions in chest compressions.

the following was copied from part 4: adult basic life support:

a compression-ventilation ratio of 30:2 is recommended and further validation of this guideline is needed (class iia). in infants and children (see part 11: "pediatric basic life support"), 2 rescuers should use a ratio of 15:2 (class iib).

this 30:2 ratio is based on a consensus of experts rather than clear evidence. it is designed to increase the number of compressions, reduce the likelihood of hyperventilation, minimize interruptions in chest compressions for ventilation, and simplify instruction for teaching and skills retention. a manikin study suggests that rescuers may find a compression-ventilation ratio of 30:2 more tiring than a ratio of 15:2. further studies are needed to define the best method for coordinating chest compressions and ventilations during cpr and to define the best compression-ventilation ratio in terms of survival and neurologic outcome in patients with or without an advanced airway in place.

once an advanced airway is in place, 2 rescuers no longer deliver cycles of cpr (ie, compressions interrupted by pauses for ventilation). instead, the compressing rescuer should give continuous chest compressions at a rate of 100 per minute without pauses for ventilation. the rescuer delivering ventilation provides 8 to 10 breaths per minute. the 2 rescuers should change compressor and ventilator roles approximately every 2 minutes to prevent compressor fatigue and deterioration in quality and rate of chest compressions. when multiple rescuers are present, they should rotate the compressor role about every 2 minutes.

the compression rate refers to the speed of compressions, not the actual number of compressions delivered per minute. the actual number of chest compressions delivered per minute is determined by the rate of chest compressions and the number and duration of interruptions to open the airway, deliver rescue breaths, and allow aed analysis. rescuers must make every effort to minimize these interruptions in chest compressions. in 1 out-of-hospital study rescuers intermittently achieved compression rates of 100 to 121 compressions per minute, but the mean number of compressions delivered per minute was reduced to 64 compressions per minute by frequent interruptions.

i hope this information was helpful.

...and yea, you are supposed to allow recoil, and make sure your compressions are deep enuf. "Stayin Alive" should get you to the 100/min mark. I've seen rather spastic compression-giving too. I think that it comes out of fear/excitement and fatigue.

Thanks guys- I had my BLS certification in the fall of 2009 so I didn't think it changed that much. Just wanted to make sure I wasn't doing the wrong thing.