Can proportional ventilation modes facilitate exercise in critically ill patients? A physiological cross-over study

Abstract

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.

Proportional modes versus pressure support ventilation: a systematic review and meta-analysis

“…Proportional assist ventilation (PAV) [10] and neurally adjusted ventilatory assist (NAVA) [11] are designed to improve patient–ventilator interaction [12]. Both modes are designed to adjust inspiratory pressure proportionally to the patient’s inspiratory demand and are known as proportional modes [13]. PAV+ (Puritan Bennett 840/980 ventilator; Covidien, Boulder, Colorado, USA) automatically measures the elastance and resistance of the respiratory system during spontaneous breathing and delivers the adequate pressure needed to meet the flow and volume demand that are instantaneously measured on a breath-to-breath basis [14].…”

Settings and monitoring of mechanical ventilation during physical therapy in adult critically ill patients: protocol for a scoping review

“…These results could be explained by a lack of knowledge on the optimal dosage of physical therapy for ICU patients (in terms of intensity, duration and frequency) 18–21. Alternatively, during physical therapy a mismatch between ventilatory support and exercise-induced ventilatory demand may excessively increase work of breathing, limiting physical therapy performance and eventually leading to fatigue 22…”

“…Despite expert consensus and recommendations on active mobilisation of mechanically ventilated patients,23 ventilator settings and safety parameters to monitor during mobilisation have not yet been defined. Some authors have suggested strategies to adjust ventilatory support during physical therapy; for example, increasing support level during pressure support ventilation,24 using proportional ventilation modes,22 employing assist-control ventilation before and after physical therapy25 or increasing the fraction of inspired oxygen 25. In addition, mechanical ventilators allow real-time monitoring of respiratory (eg, respiratory rate or minute ventilation) and metabolic variables (eg, carbon dioxide production)22 26 that could provide useful information to individualise the dosage of physical therapy or ventilatory support.…”

“…Some authors have suggested strategies to adjust ventilatory support during physical therapy; for example, increasing support level during pressure support ventilation,24 using proportional ventilation modes,22 employing assist-control ventilation before and after physical therapy25 or increasing the fraction of inspired oxygen 25. In addition, mechanical ventilators allow real-time monitoring of respiratory (eg, respiratory rate or minute ventilation) and metabolic variables (eg, carbon dioxide production)22 26 that could provide useful information to individualise the dosage of physical therapy or ventilatory support. There is therefore a need to summarise the existing knowledge on the use of MV as a potential tool to provide safe and efficient physical therapy for ICU patients.…”

Non-Invasive Ventilation as an Adjunct to Exercise Training in Chronic Ventilatory Failure: A Narrative Review

“…Proportional modes of assisted ventilation like PAV can translate into longer and more efficient training sessions [53]. A preliminary study [72] in intubated patients showed that proportional ventilation modes such as PAV and the more recently introduced Neurally Adjusted Ventilatory Assist (NAVA) [73] during exercise resulted in higher work efficiency and less increase in oxygen consumption compared to ventilation with inspiratory pressure support [72]. Whether these results can be translated to patients with CVF is unknown.…”