No abstract

The optimal ventilation strategy during cardiopulmonary resuscitation (CPR) is unknown. Chest compression (CC) generates circulation, while during decompression, thoracic recoil generates negative pressure and venous return. Continuous flow insufflation of oxygen (CFI) allows noninterrupted CC and generates positive airway pressure (Paw). The main objective of this study was to assess the effects of positive Paw compared with the current recommended ventilation strategy on intrathoracic pressure (P(IT)) variations, ventilation, and lung volume. In a mechanical model, allowing compression of the thorax below an equilibrium volume mimicking functional residual capacity (FRC), CC alone or with manual bag ventilation were compared with two levels of Paw with CFI. Lung volume change below FRC at the end of decompression and P(IT), as well as estimated alveolar ventilation, were measured during the bench study. Recordings were obtained in five cardiac arrest patients to confirm the bench findings. Lung volume was continuously below FRC, and as a consequence P(IT) remained negative during decompression in all situations, including with positive Paw. Compared with manual bag or CC alone, CFI with positive Paw limited the fall in lung volume and resulted in larger positive and negative P(IT) variations. Positive Paw with CFI significantly augmented ventilation induced by CC. Recordings in patients confirmed a major loss of lung volume below FRC during CPR, even with positive Paw. Compared with manual bag ventilation, positive Paw associated with CFI limits the loss in lung volume, enhances CC-induced positive P(IT), maintains negative P(IT) during decompression, and generates more alveolar ventilation.

Despite identical ventilator settings, the different PPV modes lead to substantial differences in VT, PTP, and breathing variability in the presence spontaneous efforts. Clinicians should be aware of the possible harmful effects of i-synchronization especially when high VT is undesirable.

Major complications after the use of CPSN are not in fact rare. The incidence of severe neuropathy or infection complications is, respectively, 0.50% and 0.25%. However, the insertion of CPSN could be considered effective and is associated with only a few minor complications.

BackgroundEarly exercise of critically ill patients may have beneficial effects on muscle strength, mass and systemic inflammation. During pressure support ventilation (PSV), a mismatch between demand and assist could increase work of breathing and limit exercise. A better exercise tolerance is possible with a proportional mode of ventilation (Proportional Assist Ventilation, PAV+ and Neurally Adjusted Ventilatory Assist, NAVA). We examined whether, in critically ill patients, PSV and proportional ventilation have different effects on respiratory muscles unloading and work efficiency during exercise.MethodsProspective pilot randomized cross-over study performed in a medico-surgical ICU. Patients requiring mechanical ventilation >48 h were enrolled. At initiation, the patients underwent an incremental workload test on a cycloergometer to determine the maximum level capacity. The next day, 2 15-min exercise, at 60% of the maximum capacity, were performed while patients were randomly ventilated with PSV and PAV+ or NAVA. The change in oxygen consumption (ΔVO2, indirect calorimetry) and the work efficiency (ratio of ΔVO2 per mean power) were computed.ResultsTen patients were examined, 6 ventilated with PSV/PAV+ and 4 with PSV/NAVA. Despite the same mean inspiratory pressure at baseline between the modes, baseline VO2 (median, IQR) was higher during proportional ventilation (301 ml/min, 270–342) compared to PSV (249 ml/min, 206–353). Exercise with PSV was associated with a significant increase in VO2 (ΔVO2, median, IQR) (77.6 ml/min, 59.9–96.5), while VO2 did not significantly change during exercise with proportional modes (46.3 ml/min, 5.7–63.7, p < 0.05). As a result, exercise with proportional modes was associated with a better work efficiency than with PSV. The ventilator modes did not affect patient’s dyspnea, limb fatigue, distance, hemodynamics and breathing pattern.ConclusionsProportional ventilation during exercise results in higher work efficiency and less increase in VO2 compared to ventilation with PSV. These preliminary findings suggest that proportional ventilation could enhance the training effect and facilitate rehabilitation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13613-017-0289-y) contains supplementary material, which is available to authorized users.