Abstract 290: Low Minute Ventilation Volume During CPR Disturbs the Relationship between End-Tidal CO2 and Coronary Perfusion Pressure

• Published in: Circulation (New York, N.Y.) Vol. 128; no. suppl_22
• Main Authors: Ordelman, Simone, van Berkom, Paul, Aelen, Paul, Woerlee, Pierre, Noordergraaf, Gerrit J
• Format: Journal Article
• Language: English
• Published: 26-11-2013
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/circ.128.suppl_22.A290

Abstract only
End-tidal CO
2
(ETCO
2
) is important for monitoring CPR quality as a surrogate for coronary perfusion pressure (CPP) and flow. We hypothesized that sufficient minute volume ventilation is not only needed to control CO
2
buildup, but also for the exhaled CO
2
to CPP relationship to remain valid.
To test our hypothesis, we measured minute volume ventilation together with CPP, arterial PCO
2
(PaCO
2
), and ETCO
2
in a pig model. Ventricular fibrillation was induced in 24 pigs, after which automated CPR (5 cm, 100 cpm) followed for 20 minutes. Animals were ventilated manually using a bag-mask-valve, either continuously at 10 min
-1
(group 1, n=8) or 30:2 mode (group 2, n=16). Correlation coefficients between CPP and ETCO
2
were calculated for each pig during the CPR interval.
Minute volume ventilation during CPR was 3.4 ± 1.0 L/min for group 1 and 2.2 ± 0.3 L/min for group 2 pigs. In group 1, PaCO
2
changed little during CPR (41.1 ± 7.6 mmHg initially vs. 38.6 ± 16.5 mmHg at 20 minutes), indicating suitable minute volume ventilation. ETCO
2
decreased concurrently with CPP. The correlation coefficient between CPP and ETCO
2
was 0.52 ± 0.39. Group 2 pigs showed a large increase in PaCO
2
(49.8 ± 6.6 mmHg initially vs. 58.0 ± 13.6 mmHg at 20 minutes), consistent with small minute volume ventilation. This increase in PaCO
2
was accompanied by a progressively increasing ETCO
2
, while the CPP consistently decreased. The CPP to ETCO
2
correlation coefficient showed a low, but negative (-0.18 ± 0.51) relationship, strongly supporting that the indicator function of ETCO
2
was lost. The figure shows an example.
In conclusion, insufficient ventilation affects ETCO
2
and can disturb the relationship between ETCO
2
and CPR quality as measured by CPP. This is reminiscent of hyperventilation effects. Ventilation minute volumes should therefore be monitored, and hypoventilation avoided, to prevent clinical misinterpretation of ETCO
2
values.