This month's Editor's Choice comes from a group of respiratory therapists at Children's Hospital of Boston who tackled the issue of determining ideal body weight (IBW) for selecting tidal volumes in pediatric patients. They compared three methods of IBW calculations and found clinically important differences between IBW and actual body weight with each. Importantly, these differences were exaggerated in obese subjects. Rehder and Turner pen an accompanying editorial highlighting the importance of these findings in the wake of an obesity epidemic in children.
Bordessoule and colleagues describe the imposed work of breathing in a bench study of high frequency oscillators. Their results suggest that oscillator frequency was the primary parameter influencing imposed work. Smallwood and DiBlasi provide commentary and attempt to link these bench findings with clinical correlates.
Avoiding ventilator-induced lung injury has become a primary goal of mechanical ventilation. Zhou and coworkers evaluate the determination of stress index by visual inspection of pressure-time waveforms. They report that visual inspection without additional technology is simple and reliable. In an accompanying editorial, authors from Mayo Clinic describe the merits and pitfalls of this approach.
Alqahtani et al describe the impact of humidification on facial skin integrity during noninvasive ventilation. Using a number of sophisticated measures, they found that the addition of humidity may alter the barrier function of the skin. This study in healthy volunteers requires clinical validation; and other aspects of patient comfort, including airway dryness and secretion mobilization, should be considered.
Volsko and others evaluated endotracheal tube position in infants and children using a retrospective record review. They report a significant proportion of tubes were malpositioned on post-intubation chest radiograph. Most of these findings did not lead to clinical consequences.
Deshpande et al describe the placement and securing of a newly designed endotracheal tube compared to a standard tube in a model setting. There were few differences in provider performance between tubes. Importantly, the new tube is meant to reduce unplanned extubation, but that was not evaluated in this study.
Sarhan and others evaluated the effect of a new holding chamber used with a jet and mesh nebulizer on medication delivery in a model and in healthy volunteers. Their data suggest that the holding chamber and mesh nebulizer resulted in an increased medication delivery compared to use of a T-piece.
Passive circuits are in part a key to the successful application of noninvasive ventilation, with ventilators meant to operate with a leak. De Mattia et al compared passive circuits to circuits with an exhalation valve in a small group of subjects with amyotrophic lateral sclerosis at home. They report greater technical adverse events with the active circuit, but these were not associated with important outcomes. Importantly, the a priori decision to use passive versus active circuits may have impacted results, as active circuits were more likely to be applied in subjects with more advanced disease. Passive circuits might also be associated with less reliable tidal volume delivery, an important consideration.
In a bench study of adaptive pressure support, Stagnara and colleagues evaluated the tidal volume (VT) reported to the memory of noninvasive ventilators compared to a laboratory measurement. They report that PEEP, non-intentional leak, and lung model conditions impacted accuracy, primarily underestimating VT. Both the mode and passive circuits may contribute to the inaccuracy in VT measurement. The use of ventilator-recorded volumes to evaluate therapy at intervals or via telemedicine must take these findings into account.
Recent studies have failed to demonstrate improved outcomes associated with heliox during mechanical ventilation. Wise et al performed a single center retrospective review of heliox use for treatment of congenital diaphragmatic hernia, reporting reduced PaCO2 and improved pH compared to conventional mechanical ventilation. Importantly, this was coupled with permissive hypercapnia, which has recently been shown to have a negative impact in this population. To define the role of heliox, prospective controlled trials are required.
Williams and others studied the impact of different closed-circuit suction catheter designs on pMDI aerosol delivery with and without simulated exhaled humidity in a lung model. They report that exhaled humidity impacted measurements and closed-circuit adapters varied in performance. This study highlights some of the limitations of models used to evaluate aerosol delivery.
This year's New Horizon's Symposium features the role of ECMO. Advances in the safety and simplicity of ECMO have resulted in a meteoric rise in the use of ECMO for both cardiovascular and respiratory disease. This series of papers describes new technology, the use of ECMO in hypercapnic respiratory failure, and ECMO to facilitate lung protection. These papers are definitive reviews but must be considered in light of the Rescue Lung Injury in Severe ARDS (EOLIA) Trial that found no difference in 60-d mortality between ECMO and conventional ventilation when using ECMO as a rescue therapy.
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