Document: Invite

Comments:

BLS-09-v1

RECOVER 2.0 Worksheet

QUESTION ID: BLS-09

PICO Question:
In non-intubated cats and dogs in CPA or during single-rescuer CPR in cats and dogs (P), does the use of another specific compression:ventilation (C:V) ratio (I), compared with a C:V ratio of 30:2 (C), improve ... (O)?

Outcomes:
Favorable neurologic outcome, PaCO2, Oxygenation, Surrogate marker(s) of perfusion, Survival to discharge, ROSC

Prioritized Outcomes (1= most critical; final number = least important):

Favorable neurologic outcome
Survival to discharge
ROSC
PaCO2
Oxygenation
Surrogate markers of perfusion

Domain chairs: Steve Epstein, Kate Hopper; final edit by Jamie Burkitt

Evidence evaluators: Laura Cole, Kerry Doolin

Conflicts of interest: None reported

Search strategy: See attached document

Evidence Review:

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	OBS	- -	- -	0	0	0	0	0	11	19	RR= 1.04, 95% CI of 0.73 to 1.47		Very low
2	EXP	0	-	0	0	0	0	0					Low
Outcome: Survival to hospital discharge
2	OBS	--	-	0	0	0	0	0					Very Low
4	EXP	-	--	0	0	0	0	0					Very Low

Outcome: ROSC
2	OBS	--	--	0	0	0	0	0	Very Low
5	EXP	-	-	0	0	0	0	0	Very Low

Outcome: PaCO2

EXP

- -

Very low

Outcome: Oxygenation

EXP

- -

Very low

PICO Question Summary

Introduction

When providing CPR to animals without an advanced airway such as an endotracheal tube, or during single-rescuer CPR, it is necessary to pause chest compressions in order to provide ventilation. The current human and previous veterinary CPR guidelines recommend a compression : ventilation (C:V) ratio of 30:2.1,2

Consensus on science

Outcome 1: Favorable neurologic outcome:

We identified 2 experimental studies in swine (low quality of evidence, downgraded for serious indirectness) and 1 observational study in people (very low quality of evidence, downgraded for very serious risk of bias and very serious indirectness) that addressed the PICO question.3–5 One experimental study in 42 swine compared neurologic outcome at 24 hours in pigs treated with either chest compression-only CPR, CPR at a ratio of 30 compressions : 1 room air ventilation, or CPR at a ratio of 30 compressions : 2 room air ventilations.4 This study found that pigs undergoing CPR at a C:V ratio of 30:1 had significantly better FNO at 24 hours than those in either the CC only group or those receiving C:V at a ratio of 30:2. Another experimental study in 40 pigs undergoing CPR compared FNO among 4 C:V ratios: 15:2, chest compression-only CPR, 50:5, or 100:2.3 Ventilated gas was simulated exhaled gas with 4% CO2 and 17% O2. This study showed that pigs treated with a C:V of 100:2 had significantly better FNO at 24 hours than those treated with either 15:2 or chest compression-only CPR. One observational study (very low quality of evidence, downgraded for very serious risk of bias and very serious indirectness) in adult human beings with OHCA found no difference in FNO in survivors between patients treated in the field a C:V ratio of 30:2 versus those treated with a C:V ratio of 15:2.5

Outcome 2: Survival to discharge:

For the critical outcome of survival to discharge, we identified 4 experimental studies (very low quality of evidence, downgraded for serious risk of bias and very serious indirectness) and 2 observational studies (very low quality of evidence, downgraded for very serious risk of bias and serious indirectness) that addressed the PICO question.3–8 Two experimental studies in swine showed no difference in 24-hour survival with C:V of 30:2 vs 30:1.3,4 One experimental study in 20 pigs showed no difference in 24-hour survival when pigs underwent either compression-only CPR, C:V of 15:1, or C:V of 5:1.7 This study7 included other interventions that likely yield its results less valuable for this PICO question. The single study in 30 dogs monitored subjects that achieved ROSC and found no difference in 2-hour survival among dogs treated with 15:1, 15:2, or 30:2 compression:ventilation ratios.8 Two human clinical observational studies showed improved survival to discharge with C:V of 30:2 when compared to 15:2; both studies included many additional interventions in combination with the change in C:V. 5,6

Outcome 3: ROSC:

For the critical outcome of ROSC, we identified 5 experimental studies (very low quality of evidence, downgraded for serious risk of bias, serious indirectness, and serious imprecision)4,7–10, and 2 observational studies (very low quality of evidence, downgraded for very serious risk of bias and very serious indirectness) that addressed the PICO question5,6. Of the 5 experimental studies identified, a C:V ratio of 30:2 was shown to be no different than 5:17, 15:18, 15:27–9, 30:14, or 100:5.10 While 4 of these studies were in pigs, 18 was in a dog model. Two human observational studies support the idea that implementation of C:V of 30:2 improves ROSC compared to a ratio of 15:2; both studies included many additional interventions in combination with the change in C:V.5,6

The less critical outcomes of PaCO2, oxygenation, and surrogate markers of perfusion were not fully summarized since a recommendation could be made based on the most critical 3 outcomes.

Treatment recommendation

We recommend a compression : ventilation ratio of 30 chest compressions : 2 breaths (30:2) in non-intubated dogs and cats undergoing CPR (strong recommendation, very low quality of evidence).

Justification of treatment recommendation

There is evidence that a C:V of 30:2 is superior to both lower C:V ratios (ratios that involve fewer consecutive chest compressions for each ventilation break) and to compression-only CPR for the outcome of FNO in experimental studies. Additionally, there is evidence in observational studies in people that a C:V of 30:2 is superior to the lower C:V ratio of 15:2 for the outcomes of survival to discharge and ROSC. There is some evidence in experimental studies that a C:V as high as 100:2 is still superior to the lower C:V of 15:2.

Additionally, 1 experimental study in pigs showed superiority of FNO with C:V of 30:1 compared to 30:2; however, this is a ventricular fibrillation model rather than a model of asphyxial arrest, the more common cause of CPA in dogs and cats.

Taken together, these findings suggest that at least 30 consecutive chest compressions should be administered during CPR in non-intubated dogs and cats, and that while ventilation is important, it is possible that it could be de-emphasized to a 30:1 C:V ratio without meaningfully worse outcome, and possibly with improvement.

Knowledge gaps

In non-intubated dogs and cats, the ideal C:V has not been established for critical outcomes of favorable neurologic outcome, survival to discharge, or ROSC.

It is unknown whether there may be a benefit to C:V of 30:1 (rather than 30:2) in non-intubated dogs and cats undergoing CPR.

References:

1. Fletcher DJ, Boller M, Brainard BM, et al. RECOVER evidence and knowledge gap analysis on veterinary CPR. Part 7: Clinical guidelines: RECOVER clinical guidelines. J Vet Emerg Crit Care. 2012;22(s1):S102-S131.

2. Panchal AR, Bartos JA, Cabañas JG, et al. Part 3: Adult Basic and Advanced Life Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2020;142(16_suppl_2):S366-S468.

3. Sanders AB, Kern KB, Berg RA, et al. Survival and neurologic outcome after cardiopulmonary resuscitation with four different chest compression-ventilation ratios. Ann Emerg Med. 2002;40(6):553-562.

4. Kim YW, Kim HI, Hwang SO, et al. Single Ventilation during Cardiopulmonary Resuscitation Results in Better Neurological Outcomes in a Porcine Model of Cardiac Arrest. Yonsei Med J. 2018;59(10):1232-1239.

5. Hinchey PR, Myers JB, Lewis R, et al. Improved out-of-hospital cardiac arrest survival after the sequential implementation of 2005 AHA guidelines for compressions, ventilations, and induced hypothermia: the Wake County experience. Ann Emerg Med. 2010;56(4):348-357.

6. Sayre MR, Cantrell SA, White LJ, et al. Impact of the 2005 American Heart Association cardiopulmonary resuscitation and emergency cardiovascular care guidelines on out-of-hospital cardiac arrest survival. Prehosp Emerg Care. 2009;13(4):469-477.

7. Kern KB, Hilwig RW, Berg RA, Schock RB, Ewy GA. Optimizing ventilation in conjunction with phased chest and abdominal compression-decompression (Lifestick) resuscitation. Resuscitation. 2002;52(1):91-100.

8. Hwang SO, Kim SH, Kim H, et al. Comparison of 15:1, 15:2, and 30:2 compression-to-ventilation ratios for cardiopulmonary resuscitation in a canine model of a simulated, witnessed cardiac arrest. Acad Emerg Med. 2008;15(2):183-189.

9. Cavus E, Meybohm P, Bein B, et al. Impact of different compression-ventilation ratios during basic life support cardiopulmonary resuscitation. Resuscitation. 2008;79(1):118-124.

10. Kill C, Torossian A, Freisburger C, et al. Basic life support with four different compression/ventilation ratios in a pig model: The need for ventilation. Resuscitation. 2009;80(9):1060-1065.

Supporting information:

PaCO2:

Experimental: In a heterogenous group of studies comparing variable C:V ratios, 9 studies found no difference in PaCO2 and 2 studies showed higher PaCO2 with higher C:V ratios

Outcome 4: PaCO2:

For the important outcome of PaCO2, we identified 11 experimental studies (low quality of evidence, downgraded for risk of bias, indirectness and imprecision) that addressed the PICO question. (5,7,9,31,33,185,187,189,192,193,200) In a heterogenous group of experimental studies comparing variable C:V ratios, 3 canine studies and 6 swine studies (5,7,31,33,185,189,192,193,200) found no difference in PaCO2 and 2 swine studies (9,187) showed higher PaCO2 with higher C:V ratios. Of the studies that evaluated a C:V ratio of 30:2, in one study it was found to have a higher PaCO2 than a ratio of 15:2 (9) and in three studies, no difference in PaCO2 was found when compared to C:V ratios of 30:1 (33,200), 15:2 or 15:1 (189).

Oxygenation:

Experimental: In a heterogenous group of studies comparing variable C:V ratios, 7 studies showed no difference in PaO2. One study showed PaO2 was lower when a C:V ratio of 50:2 or 50:5 was used versus a C:V ratio of 15:2

Outcome 5: Oxygenation:

For the important outcome of oxygenation, we identified 8 experimental studies (low quality of evidence, downgraded for risk of bias, indirectness and imprecision) that addressed the PICO question. [7,11,31,185,187,189,192,200) In a heterogenous group of experimental studies comparing variable C:V ratios, 3 canine studies and 4 swine studies showed no difference in PaO2.( 7,11,31,185,189,192,200) One swine study showed PaO2 was lower when a C:V ratio of 50:2 or 50:5 was used versus a C:V ratio of 15:2. (187)

DMU Timestamp: July 13, 2023 21:18