Chest compression release velocity: An independent determinant of end-tidal carbon dioxide in out-of-hospital cardiac arrest.

BACKGROUND: Chest compression (CC) depth, CC rate and ventilatory rate (VR) are known to have an impact on end-tidal carbon dioxide (ETCO2 ) values. Chest compression release velocity (CCRV) is increasingly acknowledged as a novel metric in cardiopulmonary resuscitation (CPR). The objective of this study was to analyze whether CCRV would have any effect on ETCO2 values.

METHODS: In out-of-hospital cardiac arrests (OHCA), effects of CC depth, CC rate, CCRV and VR on ETCO2 were analyzed through linear mixed effect models. A stratification was made on a CCRV of 300, 400 and 500 mm/s. In these categories, mean ETCO2 values were corrected for CC depth and compared through a one-way ANOVA.

RESULTS: A 10 mm increase in CC depth was associated with a 1.5 mmHg increase in ETCO2 (p < 0.001), a 100 mm/s increase in CCRV with a 0.8 mmHg increase (p = 0.010) and a 5 breaths per minute increase in VR with a 2.0 mmHg decrease (p < 0.001). CC depth was strongly correlated with CCRV (Pearson's r = 0.709, p < 0.001). After adjusting for CC depth, ETCO2 was on average 6.5 mmHg higher at a CCRV of 500 than at 400 mm/s (p = 0.005) and 5.3 mmHg higher than at 300 mm/s (p = 0.033).

CONCLUSIONS: In OHCA patients, higher CCRV values resulted in higher ETCO2 values. This effect is independent of CC depth, despite the strong correlation between CCRV and CC depth.