This month’s Editor’s Choice by van Dijk and colleagues evaluates global and regional tidal volume (VT) distribution in spontaneously breathing mechanically ventilated children. They measured VT, end-expiratory lung volume (EELV), and calculated the center of ventilation (CoV) during 2 modes of ventilation during a reduction in breathing frequency or pressure support. The median CoV was 50% and did not differ between modes. With a reduction in pressure support there was a shift of CoV towards dependent lung regions. They concluded that allowing spontaneous breathing following recovery of respiratory failure did not negatively impact EELV or distribution of VT. Cheifetz et al provide commentary regarding monitoring with electrical impedance tomography and how these data might be used clinically.
Harnois et al studied 9 volunteers receiving aerosolized saline to evaluate devices used to mitigate aerosol dispersion into the environment. Particle counters were used to measure fugitive aerosol at 1 and 3 feet from participants. They found that fugitive aerosols were greater with small volume nebulizer (SVN) than vibrating mesh nebulizer (VMN), and greater with a face mask than a mouthpiece. Mitigation devices including filters were effective at reducing environmental contamination.
Li and co-workers provide a similar study evaluating fugitive aerosols during aerosol delivery via high-flow nasal cannula (HFNC). They evaluated SVN and VMN with two HFNC devices. Fugitive aerosols were measured as above. They found one HFNC device provided an inhaled dose 6 times greater than the other and consequently more fugitive aerosols. Placing a surgical mask over the cannula effectively reduced fugitive aerosols. Quach provides commentary on the Harnois et al and Li et al studies suggesting that the key mitigation for fugitive aerosols is proper use of personal protective equipment by respiratory therapists.
Elshafei and others performed a bench study of aerosol delivery during continuous high frequency oscillation (CHFO) for airway clearance during mechanical ventilation. A jet nebulizer (JN) or VMN was attached to the manifold or placed between the endotracheal tube (ETT) and ventilator circuit. Albuterol was aerosolized and collected from filters for measurement of drug delivery. Placement of the JN at the manifold resulted in minimal albuterol delivery. Use of the VMN at the ETT delivered a dose 6 times the JN dose. Placing the VMN at the inlet of the humidifier delivered twice the dose compared to the JN.
Walsh and Liu evaluated the impact of a VMN on the in vitro activity of ribavirin. They grew and infected human epithelial type 2 cells and primary epithelial cells with respiratory syncytial virus (RSV). Non-nebulized control and aerosolized ribravin were compared to untreated controls using polymerase chain reaction to determine quantity of the virus. They concluded that the effectiveness of ribavirin was unaffected by VMN.
Haynes and Fishwick verified blood gas quality control (QC) of assayed QC materials and calculated the mean and ranges from a series of measurements. Current standards require laboratories to calculate the mean ±2 standard deviations (SD). They found that manufacturer-reported values were wider than the required 2 SD threshold, validating the need for labs to verify manufacturer-provided QC.
Basiri et al performed a double-blind trial comparing aerosolized salbutamol to normal saline in newborns with transient tachypnea of the newborn (TTN). They measured clinical outcomes at 30 min, 1 h, and 2 h including oxygen requirements and TTN clinical score. The authors concluded that newborns who received salbutamol had reduced oxygen requirements and shorter duration of respiratory support, but there were no differences in length of stay, adverse events, or other measures.
Annangi and Angel evaluated bronchodilator testing in subjects with airflow obstruction to differentiate COPD and asthma-COPD overlap. In a large group of subjects with a baseline FEV1/forced vital capacity <0.7, pre and post bronchodilator spirometry was performed. They found that spirometry performed without bronchodilator testing may lead to misclassification of asthma/COPD overlap and overdiagnosis of COPD.
Zheng et al compared bilevel positive airway pressure (BPAP) and CPAP for prevention of extubation failure in infants after cardiac surgery. Subjects were randomized to BPAP or CPAP following extubation. The main outcome variable was reintubation within 48 h. There was no difference in reintubation rate or duration of respiratory support. Both groups had improved oxygenation and relief of respiratory distress with application of positive airway pressure. The BPAP group had improved oxygenation and CO2 elimination compared to CPAP.
Gómez-Zamora and others evaluated the role of diaphragmatic ultrasound in predicting failure of noninvasive ventilation (NIV) and HFNC in infants with bronchiolitis. Diaphragmatic excursion, diaphragmatic inspiratory/expiratory time, and fraction of diaphragmatic thickening (dTF) were recorded at admission, 24 h, and 48 h. They found that ultrasound evaluation of dTF predicted treatment failure of both BPAP and HFNC but did not predict the need for invasive ventilation.
Willis and coworkers performed a retrospective review of children diagnosed with obstructive sleep apnea (OSA), prescribed positive airway pressure (PAP) therapy who also underwent follow-up polysomnography (PSG) titration. The majority of subjects were prescribed auto-titrating PAP. Following PSG titration, 78% of subjects had changes to PAP therapy. However, adherence was not increased following titration. They concluded that while PSG titration may optimize settings, this alone did not improve adherence.
Beran and others provide a systematic review of prone positioning on outcomes in non-intubated subjects (so called awake prone positioning) with COVID-19. Prone positioning improved gas exchange and resulted in a reduction in mortality as well as a reduced intubation rate, but these findings need to be confirmed in prospective studies.
Straube and colleagues contribute a narrative review on technology for intravascular gas exchange.
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