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, Survival to discharge, Hospital length of stay, Histopathologic damage - No information in the SoF, 0 studies identified.

0

N/A

None

Outcome: Surrogate markers of perfusion

2

Obs

- -

- -

0

-

0

0

0

Very low

Introduction

Chest compression depth is a factor that may alter cardiac output and perfusion to vital organs during CPR, with veterinary guidelines identifying adequate compression depth as critical for optimizing blood flow in dogs and cats during closed chest CPR.( Burkitt-Creedon 2024, Hopper 2024) Ideal compression depth may vary depending on patient conformation and position, intracardiac volume, and other parameters. Compressions that are too shallow may result in inadequate cardiac output, while excessive force and depth may result in mechanical injury to underlying thoracic or abdominal structures. The American Heart Association and Neonatal Resuscitation Program recommend a sternal compression depth of 1/3 of the anterior-posterior (AP) diameter of the chest, though these guidelines are based on very limited data (Wyckoff 2015). Ideal compression depth for newborn dogs and cats is investigated here.

Consensus on science

Outcomes 1-2: Favorable neurologic outcome, Survival to discharge

For the critical outcomes of favorable neurologic outcome and survival to discharge, we identified no studies addressing the PICO question.

Outcome 3: Surrogate markers of perfusion

For the important outcome of surrogate markers of perfusion, we identified 2 observational human studies (very low quality of evidence, downgraded for very serious risk of bias, very serious indirectness, and inconsistency).( Maher 2009/paper 1797, Meyer 2010/paper 1808) In a retrospective cohort study of 6 infants requiring cardiac surgery and subsequent CPR, the depth of chest compressions was initiated at approximately 1/3 of the AP chest diameter and then increased to 1/2 of the AP chest diameter if systolic blood pressure remained <60 mm Hg.( Maher 2009/paper 1797) The mean systolic blood pressure was 52 mmHg for the 1/3 diameter approach and 83 mmHg for the 1/2 diameter approach (p < 0.001), resulting in an increase in systolic blood pressure by 62%. Other outcomes were not measured, however, and only 1 of the 6 patients survived to hospital discharge with a favorable neurologic outcome.( Maher 2009/paper 1797) In another retrospective observational study, 54 neonatal chest CT scans were performed to compare theoretical compression depths of 1/4, 1/3, and 1/2 the AP chest diameter.( Meyer 2010/paper 1808) Ejection fraction (normal value of 69%) was estimated with mathematical modeling and increased incrementally with increasing chest compression depth (51% with 1/4 AP chest compression depth, 69% with 1/3 depth, and 106% with 1/2 depth, p < 0.001). Under-compression (defined as compression inadequate to obtain an ejection fraction of 50%) was predicted in 54% of those with 1/4 depth but no patients with other depths (p < 0.001). Over-compression (defined as lack of adequate residual chest depth) was predicted in 91% of those with 1/2 depth but not in other groups (p < 0.001). The authors concluded that, based on mathematical modeling, 1/3 AP chest compression depth should be more effective than 1/4 depth and safer than ½ depth.( Meyer 2010/paper 1808)

Outcome 4-5: Hospital length of stay, Histopathologic damage

For the important outcomes of hospital length of stay and histopathologic damage, we identified no studies addressing the question in newborns.

Treatment recommendation

In newborn puppies and kittens receiving chest compressions, we suggest a compression depth of 1/3-1/2 the width of the chest for latero-lateral compressions. (weak recommendation, very low quality of evidence)

In newborn puppies and kittens receiving chest compressions, we suggest a compression depth of 1/3 the anterior-posterior (AP) diameter of the chest for ventrodorsal (i.e., sternal) compressions. (weak recommendation, very low quality of evidence)

Justification of treatment recommendation

There is very limited and no direct evidence to answer this question in neonatal puppies and kittens. While one very small observational study in human infants demonstrated improved blood pressure with 1/2 compared to 1/3 of AP chest diameter, another study using mathematical modeling on neonatal CTs estimated adequate ejection fraction in the group with compression of 1/3 of AP chest diameter and over-compression with 1/2 of AP chest diameter. Human newborn guidelines typically recommend a sternal compression depth of 1/3 of the AP diameter of the chest; however, newborn puppies and kittens have different chest conformations, and use of lateral chest compressions is likely more common. It is reasonable to utilize a compression depth of 1/3 to 1/2 the width of the chest with later-lateral chest compressions, as in adult dogs and cats, though caution must be exercised to avoid over-compression of highly compliant chests of newborns. With sternal compression, a proportion of the AP chest diameter is occupied by the vertebral column, diminishing the compressible portion of the chest cavity. We therefore suggest a compression depth of 1/3 the AP diameter of the chest when delivering sternal compressions.

Knowledge gaps

The optimal compression depth in newborn dogs and cats in any position has not been established, and further research is needed in this area. Specifically, it is unclear whether rescuers can note the difference between 1/2 and 1/3 of chest width during compressions, given that this might only constitute 2-3 mm difference in compression distance. Furthermore, CT studies might provide some initial direction regarding the intrathoracic location of the heart in laterally recumbent or supine newborn kittens and puppies and the appropriate compression depth and compression point.