Study Design

Reduced Quality Factors

0 = no serious, - = serious,

- - = very serious

Positive Quality Factors

0 = none, + = one, ++ = multiple

Dichotomous Outcome Summary

Non-Dichotomous Outcome Summary

Brief description

Overall Quality

High, moderate, low,
very low, none

No of studies

Study Type

RoB

Indirectness

Imprecision

Inconsistency

Large Effect

Dose-Response

Confounder

# Intervention with Outcome

# Control with Outcome

RR (95% CI)

Outcome: Favorable neurologic outcome

1

OB

-

-

0

0

0

0

0

Very low

Outcome: Survival to discharge

1

OB

-

-

0

0

0

0

0

Very low

Outcome: ROSC

2

OB

-

-

-

0

0

0

0

Very low

3

EX

0

- -

-

-

0

0

0

Very low

Outcome: Surrogate marker(s) of perfusion

4

Ex

0

- -

-

-

0

0

0

Very low

Introduction

It is generally accepted that ETCO2 during CPR reflects circulation, and by extension, the quality of chest compressions, with higher ETCO2 values associated with (presumably) better blood circulation and (definitively) improved chances of ROSC. Because of the relationship between ETCO2 and quality of chest compressions, ETCO2 may be used to adjust chest compression technique to improve outcome. This question aimed to determine whether ETCO2-guided chest compressions led to improved outcome compared to CPR performed without this guidance.

Consensus on science

Outcomes 1 and 2: Favorable neurologic outcome and Survival to discharge

For the most critical outcomes of FNO and survival to discharge, 1 observational study in people was identified (very low quality of evidence, downgraded for serious risk of bias and serious indirectness) that addresses the PICO question.1 This prospective observational registry study evaluated the impact of monitoring ETCO2 and/or diastolic blood pressure (DBP) (grouped) in 9,096 adults with IHCA, and found no association between this monitoring and survival with a favorable neurologic outcome (OR 0.97, CI95 0.75–1.26, P = 0.83) or survival to discharge (OR 1.04, CI95 0.92–1.18, P = 0.57).1

Outcome 3: ROSC

For the next most critical outcome of ROSC, the same study as above1 and 1 retrospective study2 that included 87 children undergoing CPR were identified (very low quality of evidence, downgraded for serious risk of bias and serious indirectness) that address the PICO question. Sutton et al. found that monitoring using either ETCO2 or DBP was associated with higher odds of ROSC (OR 1.22, CI95 1.04–1.43, p = 0.017) compared to no monitoring.1 The Bullock study found that in pediatric resuscitation, ROSC was achieved more often among subjects where capnography use was documented (64% vs. 14%, P=0.001). Also, the mean duration of CPR was significantly longer among cases where capnography was used (29 minutes vs. 17 minutes, 95% CI 2.1, 20.2, P=0.02), which may indicate the use of ETCO2 to inform decisions to continue CPR or to change CPR technique.2

Three experimental studies (very low quality of evidence, downgraded for very serious indirectness, imprecision, and serious inconsistency) were identified that address the PICO question.3–5 All 3 of these studies compared the effects of ETCO2-guided chest compression delivery to ETCO2-blinded, standard chest compression delivery on ROSC in fibrillatory3 and asphyxial-fibrillatory4,5 models of arrest in piglets. In the fibrillatory arrest model, ROSC was no different when ETCO2 was used to guide compressions (14/20: 70%) compared to real-time audio (pulse oximeter, arterial pressure monitor), verbal, and video (“control”) feedback (13/20: 65%).3 In one asphyxial-fibrillatory piglet model, the same authors4 found that the ETCO2-directed group had a ROSC incidence of 7/14 (50%) compared to 2/14 (14%) in the control group (p=0.04). A final model of prolonged asphyxial-fibrillatory arrest in piglets5 found that at long duration of arrest (23 minutes), survival was equally poor regardless of method used to guide chest compressions (control or ETCO2-directed). After only 17 minutes of arrest, ROSC was 9/14 (64%) in the ETCO2-directed group and 3/14 (21%) in the control / ETCO2-blinded group, though this finding failed to reach significance (P = 0.05).5

Outcome 4: Surrogate markers of perfusion

For the important outcome of surrogate markers of perfusion, 4 experimental piglet studies (very low quality of evidence, downgraded for very serious indirectness, imprecision, and inconsistency) were identified that address the PICO question.3–6 In a porcine fibrillatory arrest model, MAP was better when ETCO2 was used to guide compressions (27.7 ± 5.4 mmHg) compared to real-time audio (pulse oximeter, arterial pressure monitor), verbal, and video (“control”) feedback (21.5 ± 6.4 mmHg; P = 0.002).3 Mean CVP was higher with ETCO2 guidance in this study (P = 0.04), though systemic perfusion pressure (SPP) was not different between groups.3 In an asphyxial-fibrillatory piglet model, the same authors4 found that the ETCO2-directed group had higher DBP during ALS associated with a greater increase in DBP after epinephrine administration compared to the control group (p=0.01). In a model of prolonged asphyxial-fibrillatory arrest in piglets,5 after 17 minutes of arrest, there was no difference between the groups in DBP, MAP, CVP, SPP, CPP, or ICP.5 In the same study, after 17 minutes of arrest, only MAP (P = 0.02), SPP (P = 0.03), and CPP (P = 0.02) were higher during ALS in the ETCO2-directed group than in the control group. After 23 minutes of asphyxial arrest, DBP, MAP, CVP, SPP, ICP, and CPP did not differ between groups during BLS, and only ICP was higher in the ETCO2-directed group during ALS (P = 0.03).5 The final study included a cohort of piglets with asphyxial cardiac arrest and compared a DBP-guided resuscitation strategy to an ETCO2-guided strategy (alternating between the 2 every 2 minutes). The ETCO2-guided chest compressions resulted in higher ICP (21.7 +/- 2.3 versus 16.0 +/- 1.1 mm Hg; P=0.002) while DBP-guided chest compressions were associated with a higher myocardial perfusion pressure (MPP) (6.0 +/- 2.8 versus 2.4+/- 3.2; P=0.02) and CPP (9.0 +/- 3.0 versus 5.5 +/- 4.3; P=0.047).6

Treatment recommendation

We recommend continuous measurement of ETCO2 to guide chest compression quality during CPR in dogs and cats.(strong recommendation, very low quality of evidence)

Justification of treatment recommendation

Few studies were identified that evaluated the presence of continuous ETCO2 monitoring to its absence for chest compression guidance. However, of the studies identified, most showed an improvement in ROSC or various surrogate markers of perfusion when patient-derived feedback (continuous ETCO2 or DBP measurement) was used to guide chest compressions as opposed to non-patient, guideline-driven feedback (visual, audio cues based on general, pre-specified metrics). No studies showed a clear risk of guiding chest compressions with continuous ETCO2; additionally, ETCO2 monitoring is relatively non-invasive, inexpensive, and simple to use.

Knowledge gaps

No studies are available in dogs and cats that evaluate the guidance of chest compressions based on continuous ETCO2, audio / visual feedback based on general guideline principles, or any other method.