Table 2.
Main characteristics of the clinical studies of variable mechanical ventilation
| Author | Sample (N) | Sample characteristics | Objective | Intervention | Conclusion |
|---|---|---|---|---|---|
| Boker et al.(32) | G1 = 21 patients G2 = 20 patients |
Patients who underwent elective aneurysmectomy of the abdominal aorta | To compare CV with VV for pulmonary gas exchange, respiratory mechanics, and radiological evidence of atelectasis | G1: CV (TV of 10mL/kg; RR of 10rpm; PEEP
of 0cmH2O; FiO2 of 0.6). G2: VV (mode with a volume divider - changes in RR resulted in reciprocal changes in TV to maintain the Vmin of CV) |
VV significantly improved lung function compared with CV |
| Spieth et al.(33) | 13 patients | Patients with acute hypoxemic respiratory failure who underwent ventilation with conventional PSV and variable PSV for 1 hour each, at random | To compare variable PSV with conventional PSV in terms of pulmonary function and improved patient comfort | Conventional PSV - spontaneous RR; support pressure to achieve a TV of ≈ 8mL/kg; PEEP and FiO2 in accordance with current therapy. Variable PSV - support pressure with a variation of 30% to achieve a TV of ≈ 8mL/kg | Variable PSV proved to be safe and feasible compared with conventional PSV; it increased the variability of TV and improved patient-ventilator synchrony, but the rate of gas exchange was similar for the two techniques. |
| Wang et al.(34) | G1 = 83 patients G2 = 79 patients |
Older patients subjected to elective resection of gastrointestinal tumor via laparotomy lasting more than 2 hours | To compare two protective MV strategies for cognitive dysfunction during the postoperative period in elderly patients 1 week after open abdominal surgery | G1: CV (VCV - TV of 8mL/kg; RR to reach
normocapnia; PEEP of 5cmH2O; FiO2 of 0.35).
G2: VV (VCV - TV of ≈ 8mL/kg with random cycle-to-cycle variation of 30%). |
VV versus protective CV decreased the incidence of delirium and cognitive dysfunction in the postoperative period by reducing the systemic proinflammatory response |
CV - conventional ventilation; VV - variable ventilation; G - group; TV - tidal volume; RR - respiratory rate; PEEP - positive end-expiratory pressure; FiO2 - fraction of inspired oxygen; Vmin - volume-minute; PSV - pressure support ventilation; VCV - volume-controlled ventilation.