Daily Respiratory Research Analysis
Three studies stand out today for reshaping respiratory care. A randomized trial shows high‑flow nasal oxygen can safely replace laryngeal mask ventilation for short general anesthesia, though careful CO2 monitoring is needed. A JAMA Pediatrics cross-sectional study challenges the long-held NICU practice of using diaphragm position on chest radiographs to infer neonatal lung volume, and a systematic review quantifies substantial hMPV-associated lower respiratory infection burden in older adults,
Summary
Three studies stand out today for reshaping respiratory care. A randomized trial shows high‑flow nasal oxygen can safely replace laryngeal mask ventilation for short general anesthesia, though careful CO2 monitoring is needed. A JAMA Pediatrics cross-sectional study challenges the long-held NICU practice of using diaphragm position on chest radiographs to infer neonatal lung volume, and a systematic review quantifies substantial hMPV-associated lower respiratory infection burden in older adults, informing vaccine strategy.
Research Themes
- Perioperative respiratory support and monitoring
- Objective neonatal lung volume assessment
- Viral epidemiology informing immunization policy
Selected Articles
1. High-Flow Nasal Oxygen versus Mechanical Ventilation Through a Laryngeal Mask During General Anesthesia Without Muscle Paralysis: A Randomized Clinical Trial.
In 180 hysteroscopy patients under short general anesthesia without neuromuscular blockade, high‑flow nasal oxygen (HFNO) was noninferior to laryngeal mask ventilation for intraoperative respiratory support (99% success in both). HFNO reduced postoperative respiratory symptoms (2% vs 19%) but increased hypercarbia risk, with 43% exceeding transcutaneous CO2 >55 mmHg.
Impact: This pragmatic RCT directly informs airway strategy for short procedures, showing HFNO can avoid airway instrumentation while maintaining efficacy, with a clear safety signal on CO2 retention.
Clinical Implications: HFNO is a reasonable alternative to laryngeal mask ventilation for short, non-paralyzed cases, potentially reducing postoperative respiratory/throat symptoms. However, select patients carefully and monitor CO2 closely; avoid in those at risk for hypercapnia.
Key Findings
- Primary success rate of intraoperative respiratory support was 99% in both HFNO and laryngeal mask groups, meeting noninferiority.
- Postoperative respiratory symptoms were significantly lower with HFNO (2%) versus laryngeal mask (19%).
- HFNO was associated with higher intraoperative transcutaneous CO2; 43% exceeded 55 mm Hg.
Methodological Strengths
- Randomized, noninferiority design with clear, clinically meaningful composite primary outcome
- Complete follow-through of all randomized patients and predefined monitoring of CO2
Limitations
- Single-center gynecologic population limits generalizability
- Short anesthesia duration (~30 minutes) and use of FiO2 1.0 may not reflect longer or diverse procedures
Future Directions: Evaluate HFNO across broader surgical populations and durations, optimize oxygen fraction and flow settings, and define CO2 monitoring/threshold protocols to mitigate hypercarbia risk.
BACKGROUND: Apneic oxygenation with high-flow nasal oxygen is a novel intraoperative respiratory support strategy for patients undergoing general anesthesia, but data about its clinical effects are scarce. We conducted a randomized trial to assess whether high-flow nasal oxygen is noninferior to mechanical ventilation through a laryngeal mask in terms of success rate of intraoperative respiratory support among patients undergoing a 30-minute general anesthesia session. METHODS: Single-center, randomized, noninferiority trial conducted in Italy between May 2022 and June 2023 and involving American Society of Anesthesiologists class I and II patients undergoing general anesthesia for operative hysteroscopy. Participants were randomized to receive laryngeal mask ventilation (volume-controlled ventilation to obtain end-tidal carbon dioxide between 35 and 45 mm Hg, inhaled oxygen fraction to achieve peripheral oxygen saturation greater than 95%) or high-flow nasal oxygen (70 L per minute, inhaled oxygen fraction of 100%) for intraoperative respiratory support. Patients received general anesthesia with propofol target-controlled infusion without neuromuscular blockade. Primary outcome was intraoperative respiratory support success rate, which was defined as peripheral oxygen saturation greater than 94% and transcutaneous carbon dioxide lower than 65 mm Hg with no need for rescue airway interventions for the entire procedure. Secondary outcomes included the rate of airway-related complications (including need for bag-mask or laryngeal mask ventilation, or tracheal intubation), postoperative respiratory symptoms, and postoperative dyspnea. RESULTS: All 180 patients who were randomized completed the trial (90 patients in each group). Median [interquartile range] anesthesia duration was 25 [20-36] minutes in high-flow group and 32 minutes [27-44] in the laryngeal mask group. Intraoperative respiratory support was successful in 89 patients (99%) in both groups (absolute difference 0, unilateral 95% confidence interval, 3%, noninferiority P < .001). Incidence of postoperative respiratory symptoms was significantly lower in high-flow versus laryngeal mask group (2% vs 19%, P < .001), while airway-related complications and postoperative dyspnea were not different. Intraoperative transcutaneous carbon dioxide was significantly higher in high-flow group, with 43% of patients showing values greater than 55 mm Hg. CONCLUSIONS: High-flow nasal oxygen is noninferior to laryngeal mask ventilation for intraoperative respiratory support during 30-minute general anesthesia without muscle paralysis. The risk of hypercarbia warrants careful patient selection and monitoring.
2. Diaphragm Position on Chest Radiograph to Estimate Lung Volume in Neonates.
Among 218 neonates with CT-derived lung volumes, diaphragm position on chest radiograph showed only a weak correlation with aerated lung volume (Kendall τ=0.23), consistent across hemithoraces and consolidation degrees. This challenges NICU practice of using posterior rib counting as a surrogate for lung aeration.
Impact: By rigorously comparing radiographic markers to CT volumetry, this study undermines a ubiquitous bedside practice and calls for more accurate, validated metrics to guide neonatal respiratory support.
Clinical Implications: Avoid relying on diaphragm position/rib counting to titrate ventilatory support in neonates; consider objective modalities (e.g., electrical impedance tomography, standardized lung ultrasound protocols) and physiologic endpoints for guidance.
Key Findings
- Diaphragm position on radiograph correlated weakly with CT-derived total lung volume (Kendall τ=0.23; 95% CI 0.16–0.31).
- Weak associations persisted across left/right hemithoraces and consolidation strata; apex–diaphragm distance had modest correlation (τ=0.40).
- Findings suggest inadequate precision of diaphragm position to guide clinical decisions on lung aeration in NICU.
Methodological Strengths
- Blinded assessment between CT volumetry and radiograph measurements with standardized definitions
- Relatively large neonatal cohort over a decade with semiautomated CT segmentation
Limitations
- Retrospective cross-sectional design; temporal proximity between CXR and CT not fully controlled
- Selection bias toward infants undergoing CT (e.g., 61% with cardiac diagnoses) may limit generalizability
Future Directions: Prospective validation of bedside imaging/physiologic indices (EIT, lung ultrasound, capnography) against gold-standard lung volume; development of NICU protocols minimizing reliance on radiographic heuristics.
IMPORTANCE: Using chest radiographs to guide lung aeration during respiratory support in infants is common practice and recommended in neonatal intensive care unit (NICU) guidelines, but this practice has never been validated. OBJECTIVE: To describe the association between diaphragm position on chest radiograph in infants and aerated lung volume calculated from computed tomography (CT). DESIGN, SETTING, AND PARTICIPANTS: This was a retrospective cross-sectional study conducted at a tertiary children's hospital, the Royal Children's Hospital, in Melbourne, Australia. Included were infants without congenital lung pathology who received a chest CT in the first 30 days after birth between July 9, 2012, to December 31, 2022; infant data were retrieved from the Royal Children's Hospital Medical Imaging database. Study data were analyzed from December 2022 to September 2023. EXPOSURE: Lung volume was calculated using CT semiautomated tissue segmentation and diaphragm position determined using a standardized definition. All investigators analyzing CTs were unaware of the chest radiograph measurements and vice versa. MAIN OUTCOMES AND MEASURES: The primary outcome was the distribution and precision of total lung volume at each of the measured diaphragm positions (6th-11th posterior rib). RESULTS: The imaging data of 218 infants (median [IQR] age, 11 [3-20] days old; mean [SD] age, 37.9 [1.9] weeks' gestation at birth; 119 male [55%]) were analyzed. Infants had a mean (SD) weight of 3055 (584) g at scan, and 132 (61%) had a primary cardiac diagnosis. The number of posterior ribs representing diaphragm position ranged from 6 to 11. There was only a weak association between diaphragm position and lung volume (Kendall τ = 0.23; 95% CI, 0.16-0.31). A similar weak association was observed by hemithorax (left, Kendall τ = 0.25; 95% CI, 0.15-0.34; right, Kendall τ = 0.21; 95% CI, 0.10-0.31), degree of consolidation (Kendall τ = 0.30; 95% CI, 0.21-0.38), apex-diaphragm distance (Kendall τ = 0.40; 95% CI, 0.28-0.51), and Hounsfield unit values (Kendall τ = -0.05; 95% CI, -0.15 to -0.06). CONCLUSIONS AND RELEVANCE: Results of this cross-sectional study suggest that despite long-standing acceptance in the NICU, the use of diaphragm position on chest radiograph lacked the precision required to assess aerated lung volume and guide clinical practice in infants.
3. Incidence of Human Metapneumovirus Among Older Adults in 10 High-Income Countries: A Systematic Literature Review, Meta-analysis, and Modeling Study.
Across 10 high-income locations, hMPV accounted for an estimated 7.0% of lower respiratory infections in adults ≥60 years, translating to incidence rates ranging from 186 to 462 per 100,000 in 2019. These estimates fill a key epidemiologic gap and can guide vaccine development and surveillance priorities.
Impact: Quantifying hMPV burden in older adults provides actionable targets for vaccine and prevention strategies, an area increasingly relevant with expanding adult respiratory virus immunization portfolios.
Clinical Implications: Health systems should incorporate hMPV into routine respiratory surveillance for older adults and consider these incidence estimates in prioritizing vaccine development and resource allocation.
Key Findings
- Meta-analysis of 21 studies estimated that 7.0% (95% CI 5.4–9.1%) of LRI episodes in adults ≥60 were associated with hMPV.
- Modeled hMPV incidence among adults ≥60 ranged from 185.7 to 462.1 per 100,000 across 10 high-income countries in 2019.
- Findings support inclusion of hMPV in routine surveillance and inform vaccine development strategies for older adults.
Methodological Strengths
- PRISMA-consistent systematic review and meta-analysis integrated with Global Burden of Disease incidence estimates
- Multi-country scope enabling cross-national incidence comparisons in older adults
Limitations
- Pre-pandemic year estimates (2019) may not reflect post-pandemic shifts in viral circulation
- Heterogeneity in diagnostic methods and surveillance intensity across studies
Future Directions: Expand standardized, prospective surveillance for hMPV in older adults and assess severity, hospitalization, and mortality metrics to refine vaccine value propositions.
BACKGROUND: The epidemiologic landscape for human metapneumovirus (hMPV), a respiratory pathogen, is poorly characterized, particularly among older adults. METHODS: Leveraging the latest estimates of lower respiratory infection (LRI) incidence from the Global Burden of Disease Study 2021 and meta-analyzed findings from a systematic literature review, we quantified the incidence of LRI with hMPV in 10 high-income locations among older adults in the most recent prepandemic year (2019): Canada, Chile, France, Germany, New Zealand, Netherlands, Italy, Spain, United Kingdom, and United States. RESULTS: The systematic literature review identified 21 studies with data on the percentage of LRI episodes associated with hMPV in adults aged ≥60 years in the targeted locations. Combining the meta-analyzed percentage of LRI cases associated with hMPV from these studies (7.0%; 95% CI, 5.4%-9.1%) with age-, sex-, and location-specific estimates of LRI incidence from the Global Burden of Disease Study 2021, we estimated that hMPV incidence rates per 100 000 in 2019 among adults aged ≥60 ranged from 185.7 (95% uncertainty interval, 134.7-251.1) in Italy to 462.1 (333.1-628.2) in the United States. CONCLUSIONS: Overall, our literature review, meta-analysis, and modeling study confirm a significant burden of hMPV-associated LRI in older adults. This work fills a critical evidence gap in the epidemiologic landscape of hMPV and yields actionable estimates to inform vaccine development strategies and other strategic initiatives. Future inclusion of hMPV in routine surveillance would enable more comprehensive estimates of hMPV incidence and outcomes.