Introduction The purpose of inflations during cardiopulmonary resuscitation (CPR) is to deliver an adequate tidal volume (VT) to facilitate gas exchange. However, no study has examined VT delivery during chest compression (CC) in detail to understand the effect of CC on lung aeration. The aim of the study was to examine VT changes during CC and their effect on lung aeration.
Methods Piglets were anaesthetised, instrumented and intubated with zero leak. They were then randomly assigned to CPR using either 3:1 compression:ventilation ratio (C:V) (n=6), continuous CC with asynchronous ventilations (CCaV) (90 CC/min with 30/min asynchronous ventilations) (n=6) or continuous CC superimposed with 30 s sustained inflations (CC+SI) with a CC rate of 120/min (n=5). A respiratory function monitor (NM3, Respironics, Philips, Andover, Massachusetts, USA) was used to continuously measure inspiration tidal volume (VTi) and expirational tidal volume (VTe). ANOVA with Bonferroni post-test were used to compare variables of all three groups.
Results During the inflation in the 3:1 C:V group, the mean (SD) VTi and VTe was 23.5 (5.3) mL/kg and 19.4 (2.7) mL/kg (p=0.16), respectively. During the CC, we observed a significant VT loss in the 3:1 group with VTi and VTe being 4.1 (1.2) mL/kg and 11.1 (3.3) mL/kg (p=0.007), respectively. In the CCaV group, VTe was higher compared with VTi, but this was not significant. In the CC+SI group, a VT gain during each CC with VTi and VTe of 16.3 (3.2) mL/kg and 14 (3) mL/kg (p=0.21), respectively, was observed.
Conclusions VT delivery is improved using CC+SI compared with 3:1 C:V. This improvement in VT delivery may lead to better alveolar oxygen delivery and lung aeration.
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