Editor's Commentary

This month’s Editor’s Choice by Roca and colleagues uses a post hoc analysis of a previous multicenter trial to evaluate the impact of driving pressure (∆P) on the first day of mechanical ventilation on the development of ARDS. They evaluated ∆P in 1,575 subjects, 65 (4%) of whom developed ARDS. Subjects with ∆P >12–15 cm H₂O and ∆P >15 cm H₂O had a higher probability of developing ARDS. They concluded that in subjects without ARDS, a higher ∆P on day 1 was associated with a greater risk of ARDS. Dianti and Fan provide commentary, suggesting that diagnosis and management of patients with ARDS remains a major challenge. Using ∆P to guide ventilator settings could help avoid the need to distinguish between patients with injured and uninjured lungs, thus simplifying management.

Napolitano and colleagues performed a bench study using different nasal cannula interfaces for CPAP in an infant lung model. They altered the cannulae to vary from an occlusive fit to a 70% occlusive fit. They found CPAP was lower than set in the lung with the non-occlusive cannula, which was masked by a higher resistance from the cannula. The authors concluded that interface choice and occlusive fit might be clinically important with regard to delivered airway pressures. Studeny agrees that these pressure differences could have clinical significance, but notes that the goal of CPAP is application to the lung and that mouth leak may have even a greater impact.

Chalmers and others mined an existing database of over 2,500 patients with community-acquired pneumonia or ARDS, and measured trajectory as a marker of respiratory dysfunction. Worsening trajectory was associated with reduced ventilator-free days; every increase in by 0.1 from the previous day resulted in fewer ventilator-free days. / trajectory also provided prognostic information, as an increase in / from the previous day was associated with increased ventilator-free days. They concluded that trajectory alone was as good as /, and more easily monitored. Sampson and colleagues opine that is commonly manipulated in the ICU often erring on the side of hyperoxemia. They suggest that simple trajectory is a useful tool which could be made diagnostic using closed loop control of oxygen to further refine monitoring the progression of lung injury.

Martínez-Castro and others present a bench evaluation of 8 home care ventilators under 18 experimental conditions, evaluating delivered V_T, trigger response, pressurization, and synchrony. They found a wide range of performance characteristics with alterations in model effort and potentially important differences in trigger response times. Asynchrony was more common with higher levels of pressure support combined with reduced effort. They suggest these data might be used to match the right ventilator to the right patient.

Kaur et al describe the early identification of extubation failure using the integrated pulmonary index (IPI) and other risk factors. This retrospective analysis evaluated 216 subjects and the main outcome defined as reintubation or requirement for noninvasive ventilation (NIV) within 48 h. Extubation failure was associated with higher body mass index, severity of illness scores, and a fall in IPI within an hour following extubation. The findings implicate ≥3 risk factors as an independent risk for extubation failure.

Maddux and others performed a multicenter prospective, observational trial in pediatric subjects treated with inhaled nitric oxide (INO) for pulmonary dysfunction. Subjects were categorized into cohorts: subjects born early preterm (< 32 weeks post-conceptual age [PCA]), late preterm (32–37 weeks PCA), and full term. They reported that lower respiratory tract disease, but not history of prematurity, was independently associated with lower mortality. They concluded that clinical trials evaluating INO use should consider stratifying by early preterm status.

Sørensen and co-workers compared arterial blood gases (ABG) and transcutaneous measurements in subjects with COPD exacerbation. They included 57 measurements from 20 subjects to determine the bias for transcutaneous carbon dioxide () and oxygen (). The limits of agreement were -11 to 16 mm Hg for and -28 to 51 mm Hg for . They concluded that transcutaneous measurements of CO₂ and O₂ did not accurately reflect results from ABG analyses in hypercapnic subjects.

Jensen and others evaluated the impact of pneumatic tube transport on measured blood gas and blood analytes. Duplicate blood samples were drawn and one was walked to the lab while the other sent via pneumatic tube transport. They reported that pneumatic tube transport of blood specimens was acceptable for blood gas and supplementary analytes and found no clinical or statistically significant differences between samples.

Dundek et al describe their evaluation of a bubble CPAP system developed for use in low resource settings. Using a bench model including 3D-printed nares, they found that the CPAP, , and delivered relative humidity were within predefined specifications. These bench findings support use in clinical trials for determination of device utility.

Berlinski compared the delivery of 7% hypertonic saline to a model using a continuous output nebulizer, 2 breath-enhanced nebulizers (BEN), and a breath-actuated nebulizer (BAN). He used a breathing simulator mimicking an infant, child, and adult and employed cascade impaction to evaluate aerosol characteristics. Mass median diameter, percentage of particles < 5 μm, and percentage of particles 1–3 μm were similar between BEN and BAN devices. BEN nebulizers had the greatest airway delivery.

Rhodes et al evaluated the impact of environmental factors on particle size distribution from hydrofluoroalkane (HFA) albuterol inhalers. They used a laser particle size analyzer to measure particles in the 1–5 μm range (fine particle fraction [FPF]) at varying factors including cold versus hot, full versus middle versus near empty inhaler actuations, shaken versus unshaken, and inhaler characteristics following water submersion. FPF was reduced with cold temperatures, and the early portion of the inhaler lifespan had higher FPF. There was no impact from shaking, and submersion reduced the FPF.

Crescimanno and colleagues evaluated the short-term impact of pressure-controlled (PC) versus volume-controlled breaths during NIV in subjects with amyotrophic lateral sclerosis (ALS). A cross-over study of 27 ALS subjects included polysomnography and during ventilation during day and night. They found greater asynchrony with volume-controlled breaths, while arousal index was reduced with PC breaths. Patient preference was PC in 21 of 27 subjects. The authors concluded that PC may be favored for NIV in ALS despite similar correction of hyperventilation.

COVID-19 remains an issue in the fall of 2021. Longino and coworkers describe respiratory mechanics of subjects treated early in the pandemic. They retrospectively reviewed recorded daily pulmonary compliance, , , and use of prone positioning (PP). Trends were analyzed separately over days 1–10 and days 1–35, stratified by PP use, survival, and initial /. They reviewed data from 49 subjects demonstrating a fall in compliance from day 1 to day 14 (41 to 25 mL/cm H₂O). / was higher among survivors, and PP improved both oxygenation and pulmonary compliance. They concluded that COVID-19 ARDS follows similar trajectory to other causes of ARDS.

Gochicoa-Rangel an others evaluated gas exchange abnormalities following recovery from COVID-19. They evaluated 171 subjects performing pulmonary function testing and lung computed tomography (CT) as well as exercise ability. Most subjects (96%) had signs of residual pneumonia on CT scan and carbon monoxide diffusing capacity was below the lower limit of normal. During the 6-min walk test, 67% of subjects demonstrated a desaturation of >4%. Subjects who had required mechanical ventilation had greater residual dysfunction.

Homan and Nayak contribute a narrative review on the short and long-term complications of bronchopulmonary dysplasia (BPD). They suggest that the long-term consequences of BPD may best be addressed through future research, including better understanding of the mechanisms leading to BPD and management of BPD patients as adults.

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