Optimization of mechanical ventilation in cardiac arrest

Abstract

Mechanical ventilation is one of the significant components of specialized cardiopulmonary resuscitation. Its role is that of oxygenation and release of carbon dioxide (CO₂). However, it has a major impact on haemodynamics. The interaction between the heart and lungs increases in patients during cardiac arrest, as intermittent positive ventilation is closely linked to thoracic compressions and decompressions during external cardiac massage. In order to limit this potentially negative impact, international recommendations stipulate a low tidal volume (6–7 ml / kg) as well as a low ventilation rate (10 / min). Oxgenation is far more dependent on the cardiac flow output, and minimal ventilation is sufficient for alveolar lavage. Conversely, it is recognised that increasing the ventilation rate has a negative impact on the coronary perfusion pressure. So as to reduce the negative haemodynamic effect of positive intermittent ventilation, some authors are interested in a new continuous ventilation technique, allowing a permanent positive pressure to be maintained in the airways; the oxygenation and release of CO₂ occur through simple external cardiac massage actions. Nevertheless, very few studies have concentrated on optimizing the inspired oxygen fraction during resuscitation. Post-resuscitation hyperoxygenation is now recognized as an issue due to oxidative stress and evidence of secondary neuronal lesions. Thus, mechanical ventilation must be optimized, more for the haemodynamic impact and the resulting effects, than for its role as an oxygenator.