16 Study Design

17 Reduced Quality Factors

18 0 = no serious, - = serious,

19 - - = very serious

20 Positive Quality Factors

21 0 = none, + = one, ++ = multiple

22 Dichotomous Outcome Summary

23 Non-Dichotomous Outcome Summary

24 Brief description

25 Overall Quality

26 High, moderate, low,
very low, none

27 No of studies

28 Study Type

29 RoB

30 Indirectness

31 Imprecision

32 Inconsistency

33 Large Effect

34 Dose-Response

35 Confounder

36 # Intervention with Outcome

37 # Control with Outcome

38 RR (95% CI)

39 Outcome: Favorable neurologic outcome, Survival to discharge, ROSC, Surrogate markers of perfusion

40 0

41 N/A

42 Outcome: Chest compression quality

43 1

44 OBS

45 0

46 -

47 -

48 0

49 0

50 +

51 0

52 In this adult human observational study they identified that chest compression rate was consistent with a single rescuer for up to 3 minutes, however chest compression depth started to significantly diminish at 2 and 3 minutes of chest compressions while there was a linear decrease of 6.6 ± 4.9 mm (p=0.002) over 90 to 180 seconds, representing a 12.1% decay in compression depth during that time.

53 Very low

54 5

55 EXP

56 0

57 -

58 -

59 0

60 0

61 +

62 0

63 5 manikin studies, 2 studies found quality of CC after 1 min were better than after 5 min, one study found, 1 min better than 2 min, one study found no difference over 5 min of continuous CC and one study showed continuous deterioration in CC quality over 10 minutes of continuous compressions

64 Low

66 Introduction

67 High quality chest compressions (CCs) are considered essential to successful CPR. The quality of CCs is impacted by the depth of compression, compression rate, and leaning during the recoil phase. There is evidence that the quality of CCs can deteriorate over time due to rescuer fatigue and the current human and previous veterinary CPR guidelines recommend alternating rescuers every 2 minutes.1,2

68 Consensus on science

69 For the most critical outcomes of FNO, Survival to discharge, ROSC, and Surrogate markers of perfusion, we identified no studies addressing the PICO question.

70 Outcome 5: Chest compression quality

71 For the important outcome of CC quality we found 5 experimental studies and 1 observational study that address the PICO question.3–8 One observational study of CPR in adults with IHCA (very low quality of evidence, downgraded for serious indirectness and serious imprecision, upgraded for dose-response effect) found CC rate was consistent with a single rescuer for up to 3 minutes of CCs; however, CC depth significantly diminished at both 2 and 3 minutes. There was a linear decrease in depth of 6.6 ± 4.9 mm (p=0.002) from 90 to 180 seconds, representing a 12.1% decay in compression depth during that time. Five experimental manikin studies were identified (low quality of evidence, downgraded for serious indirectness and serious imprecision, upgraded for dose-response effect); 2 of these studies found the quality of CCs after 1 minute was better than after 5 minutes. One study found the quality of CCs after 1 minute was better than at 2 minutes and 1 study showed continuous deterioration in CC quality over 10 minutes of continuous compressions with the mean percent of adequate CCs per 30 second interval being < 70% at the 2-minute time point. In contrast, one manikin study found no difference in CC quality over 5 min of continuous CCs.

72 Treatment recommendation

73 We recommend the cycles of chest compressions delivered by an individual rescuer not extend beyond 2 minutes in intubated dogs and cats undergoing CPR.(strong recommendation, low quality of evidence)

74 We recommend that if a rescuer perceives they are becoming fatigued, or if other rescuers perceive inadequate chest compression quality, it is reasonable to change compressors during a cycle while minimizing interruption in chest compressions (< 1 second).(strong recommendation, expert opinion)

75 Justification of treatment recommendation

76 Several experimental studies show diminished chest compression quality between minute 1 and minutes 2-3 of chest compressions in a manikin model, and quality of compressions diminishes greatly when a single rescuer performs 5 or more minutes of continuous chest compressions. While there is also a decline in compression quality from 1 to 2 minutes, data show that compressions must be delivered for 60 seconds before reaching maximal arterial pressures during CPR.9 Thus, the risk of decline in compression quality must be weighed against the potential for longer hands-off time that could result from pausing to change the compressor more frequently.

77 Knowledge gaps

78 The ideal duration of manual, continuous chest compressions before switching rescuers in dogs and cats undergoing CPR is unknown. The ideal duration of chest compression delivery to avoid rescuer fatigue severe enough to compromise chest compression quality may be as short as 1 minute; further research is needed. The onset of rescuer fatigue when performing chest compressions in dogs and cats may be different than that documented in human manikin models and may differ depending on patient size and chest conformation.