The Importance of Measuring Ventilation During Resuscitation

The Role of Chest Compressions on Ventilation during Advanced Cardiopulmonary Resuscitation

Background: There is growing interest in the quality of manual ventilation during cardiopulmonary resuscitation (CPR), but accurate assessment of ventilation parameters remains a challenge. Waveform capnography is currently the reference for monitoring ventilation rate in intubated patients, but fails to provide information on tidal volumes and inspiration-expiration timing. Moreover, the capnogram is often distorted when chest compressions (CCs) are performed during ventilation compromising its reliability during CPR. Our main purpose was to characterize manual ventilation during CPR and to assess how CCs may impact on ventilation quality. Methods: Retrospective analysis were performed of CPR recordings fromtwo databases of adult patients in cardiac arrest including capnogram, compression depth, and airway flow, pressure and volume signals. Using automated signal processing techniques followed by manual revision, individual ventilations were identified and ventilation parameters were measured. Oscillations on the capnogram plateau during CCs were characterized, and its correlation with compression depth and airway volume was assessed. Finally, we identified events of reversed airflow caused by CCs and their effect on volume and capnogram waveform. Results: Ventilation rates were higher than the recommended 10 breaths/min in 66.7% of the cases. Variability in ventilation rates correlated with the variability in tidal volumes and other ventilatory parameters. Oscillations caused by CCs on capnograms were of high amplitude (median above 74%) and were associated with low pseudo-volumes (median 26 mL). Correlation between the amplitude of those oscillations with either the CCs depth or the generated passive volumes was low, with correlation coefficients of -0.24 and 0.40, respectively. During inspiration and expiration, reversed airflow events caused opposed movement of gases in 80% of ventilations. Conclusions: Our study confirmed lack of adherence between measured ventilation rates and the guideline recommendations, and a substantial dispersion in manual ventilation parameters during CPR. Oscillations on the capnogram plateau caused by CCs did not correlate with compression depth or associated small tidal volumes. CCs caused reversed flow during inspiration, expiration and in the interval between ventilations, sufficient to generate volume changes and causing oscillations on capnogram. Further research is warranted to assess the impact of these findings on ventilation quality during CPR.

Effects of Chest Compression on Ventilation Quality during Cardiopulmonary Resuscitation

Ventilation is an important part of cardiopulmonary resuscitation (CPR). The advanced airway mode and 30:2 mode are used for intubated and non-intubated patients, respectively. It is debatable that passive produced by 30 compressions can provide adequate tidal volume for 30:2 mode. In addition, the fragmented ventilation caused by continuous compression may result in ineffective ventilation. In the study, one pig was anaesthetized and intubated for 2 CPRs. Continuous chest compressions with ventilation and continuous chest compressions without mechanical ventilation were performed in 2 CPRs, respectively. Three 10-minute data segments including a period of normal ventilation (V segment), a period of only compressions without ventilation (C segment), and a period of compressions with ventilation (C-V segment) were used to analyze peek flow (PF), peek pressure (PP) and tidal volume. All the data was presented as mean ± standard deviation. Chest compression resulted in 14.90% increase in mean PP (2401.40 ± 94.75 Pa vs 2822.06 ± 291.10 Pa, p<0.05), 81.46% increase in average PF (319.58 ± 56.93 ml/s vs 579.92 ± 80.27 ml/s, p<0.05). The mean tidal volumes for C segment, V segment and C-V segment were 189.13 ml, 514.72 ml, and 429.26ml, respectively. Continuous compressions reduced the accumulative tidal volume, but when five compressions were made in one inspiratory phase, there is almost no loss of tidal volume (510.86 ± 47.24 ml vs 514.72 ± 29.25 ml, p<0.05). The study suggested the ventilator without feedback regulation might reduce the peek pressure during CPR and 5 compressions in 2 s inspiratory phase provided higher tidal volume.Clinical Relevance- This study shows that 150 chest compressions per minute provided greater tidal volume than 100 and 120 compressions per minute; continuous chest compressions could also provide a certain amount of oxygen supply.