#Adult tidal volume chart trial#

#Adult tidal volume chart trial#

Meanwhile, for pediatric ventilation, there is no simple formula to estimate PBW: the dominant PBW formula (used in the ARDS Network trial and generally attributed to Devine ) is formally defined only for heights above about 5 ft/152 cm. Consequently standardization has been proposed. The difference in estimated PBW between these 2 approaches can vary by up to 30%. For adults, PBW formulae do exist, with 2 different approaches used to predict lean body mass in the early ARDS studies. There is the challenge of appropriately estimating a weight from the estimated height. If height cannot be measured or provided by the patient, more convenient surrogate measures such as arm-span, arm demispan, ulna length, or knee height have been devised. There is the challenge of obtaining a reasonable estimation of height (an issue not limited to protective ventilation alone). Such initiatives may be hindered by the multiple challenges in predicting weight from height. Various initiatives have been suggested to improve adherence, such as to change routine charting practices from the absolute tidal volumes (mL) to mL/kg PBW, or to configure alarms around mL/kg PBW rather than absolute volumes. ĭespite consensus in favor of lung protective ventilation, multiple surveys suggest that adherence is not uniform, with much scope for improvement. The tidal volume scaling factor is 5–8 mL/kg of predicted body weight (PBW) (or less at elevated plateau pressure). Therefore, by calculating initial tidal volume based on predicted (or lean) body weight rather than actual weight, configuration of the ventilator retains some connection to metabolic need (weight), while also reducing potential for volutrauma (height). Lung capacity and respiratory system compliance relate more closely to height than to weight, at least in normal subjects. The use of predicted weight is based on the assumption that volutrauma might be minimized by delivering a volume appropriate to the patient’s lung capacity. Key elements of a lung-protective strategy are the application of positive end-expiratory pressure (PEEP), limitation of plateau pressure, and a minimal tidal volume scaled to a ‘predicted’, rather than actual, body weight. Recent consensus guidance recommends the lung-protective strategy also be applied in pediatric acute lung injury. Lung-protective ventilation has also been shown to improve outcomes in patients ventilated in the operating room and in the intensive care unit (ICU). However, a ‘lung-protective strategy’ is increasingly the standard of care for acute ventilation based on data showing that this approach to treating acute respiratory distress syndrome (ARDS) in adults was associated with reduced mortality. This remains common practice for pediatric ventilation, and for much of adult ventilation. Historically, mechanical ventilation was initiated with a tidal volume based on a patient’s actual body weight, which was believed to reflect metabolic need. The ‘PBWmf + MBW’ model retains consistency with current practice over the adult range, while adding prediction for small statures. This model applies the ARDSNet ‘female’ formula to both adult sexes, while providing a tight fit to median body weight at smaller statures down to pre-term. The ‘PBWuf + MBW’ model is proposed as an appropriate compromise between prevailing practice and simplification, while also better representing lean adult body-weight.

Four alternate piecewise-linear lean body-weight predictive formulae were presented for consideration, each with different balance between the objectives. The ARDSNet PBW formulae typically predict weights heavier than the population median, therefore no single relationship could satisfy both references. Error limits for derived PBW models were relative to these references. The traditional ARDSNet PBW formulae acted as the reference for prevailing protective ventilation practice. Historic population-based growth charts were adopted as a reference for lean body weight, from pre-term infant through to adult median weight. This analysis investigated whether it might be practical to derive a unisex PBW formula spanning all body sizes, while retaining relevance to established adult protective ventilation practice.

No agreed PBW formula applies to smaller body sizes. The predicted body weight (PBW) relationship employed in the ARDS Network trial is considered valid only for adults, with a dedicated formula required for each sex. A component of lung-protective ventilation relies on a prediction of lean body weight from height. This concept has expanded to other areas of acute adult ventilation and is recommended for pediatric ventilation. The lung-protective ventilation bundle has been shown to reduce mortality in adult acute respiratory distress syndrome (ARDS).