Respiratory Care

Acute respiratory failure (ARF) in bronchiectasis is frequently accompanied by excessive airway secretions. High-flow nasal cannula (HFNC) delivers heated, humidified gas and may improve respiratory mechanics, but quantitatively measured secretion burden during HFNC in bronchiectasis-related ARF is poorly described.

We conducted a prospective, single-center pilot cohort study in a respiratory intermediate care unit including adults with computed tomography–confirmed bronchiectasis admitted with ARF and treated with HFNC as first-line therapy. The primary outcome was cumulative secretion volume (operationally defined as supervised collection of expectorated sputum, with measures to minimize saliva contamination) during the first 3 days of HFNC exposure. Physiologic variables, gas exchange, dyspnea, and clinical outcomes were assessed descriptively.

Twenty-six subjects were enrolled (median age 67 years, 54% female), predominantly with moderate-to-severe bronchiectasis. Median cumulative secretion volume over 72 h was 510 mL (436–743), and daily secretion volume increased from Day 1 to Day 3 (P < .001). Breathing frequency, oxygenation, dyspnea (Borg scale), and selected gas-exchange variables changed significantly over time. No subject required escalation to noninvasive ventilation or endotracheal intubation. In-hospital mortality was 11.5% (3/26), occurring exclusively in subjects with preestablished do-not-intubate directives.

In this pilot cohort of bronchiectasis-related ARF, structured quantification of secretion volume during HFNC was feasible and documented a large early secretion burden over 72 h. Given the uncontrolled design, these findings are descriptive and should not be interpreted as evidence of treatment effect.

Although the use of high-flow nasal cannula (HFNC) is recommended for the management of acute hypoxemic respiratory failure and for postextubation respiratory support, the efficacy for other etiologies remains uncertain. This study aimed to examine temporal trends in HFNC utilization and describe variations in clinical practice and clinical course across diverse disease categories and care settings.

We conducted a retrospective cohort study using a nationwide in-patient database in Japan. Hospitalized subjects who received HFNC between April 2016 and March 2023 were included. Temporal trends in HFNC use were evaluated by fiscal year using the Cochran–Armitage test. Subject characteristics, disease categories, treatment location at HFNC initiation (ICU, high-dependency unit, or general ward), timing of HFNC initiation, use of invasive mechanical ventilation, and in-hospital mortality were analyzed descriptively.

A total of 277,279 subjects received HFNC during the study period. The annual rate of HFNC use per 1,000 admissions increased from 2.0 in 2016 to 8 in 2022 (P < .001). Respiratory diseases were the most common indication (37%), followed by cardiovascular diseases (23%), neonatal conditions (17%), and malignancy (10%). HFNC was frequently used in conjunction with invasive mechanical ventilation, particularly after extubation, among subjects with cardiovascular conditions and neonatal subjects. In contrast, HFNC was more often used without invasive mechanical ventilation in subjects with respiratory diseases or malignancy, frequently in general wards. Overall in-hospital mortality was 25% and varied markedly by disease category and care setting, with particularly high mortality among subjects with interstitial pneumonia or malignancy who initiated HFNC in general wards, approaching 60%.

HFNC use increased markedly in Japan and expanded beyond ICUs into general wards. Utilization patterns and outcomes differed considerably by underlying disease and care setting, indicating heterogeneous clinical roles of HFNC across patient populations.

Mechanical insufflation-exsufflation (MI-E) devices support airway clearance by generating positive and negative pressure cycles that simulate a cough. Bench studies using lung models provide a controlled environment to investigate device performance and optimize settings; however, the lack of methodological standardization limits reproducibility and clinical translation.

A systematic review and network meta-analysis were conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered in PROSPERO (International Prospective Register of Systematic Reviews) (CRD42023486537). Experimental studies using adult mechanical lung models were identified from MEDLINE, Embase, and Web of Science (search updated November 2024). Two reviewers independently extracted data and assessed methodological quality using a customized risk-of-bias tool specifically developed for bench studies of respiratory devices. The primary outcome was peak expiratory flow (PEF); secondary outcomes included insufflation and exsufflation parameters. Random-effects meta-analyses were performed.

Eleven studies (2002–2024) met the inclusion criteria, encompassing 6 MI-E devices and a range of simulated lung mechanics. The most frequently used settings were +40/−40 cm H₂O with 3-s insufflation, 1-s exsufflation, and 1-s pause. Higher pressure pairs (+50/−50 cm H₂O) produced significantly greater PEF compared with lower pressures, particularly in obstructive models (mean difference = 134 L/min, 95% CI 2–267). Methodological quality varied widely, with limited information on calibration, sensor characteristics, and study reproducibility.

Higher pressure differentials generally enhance PEF, but optimal MI-E settings are not universal. MI-E performance depends on pressure settings and simulated respiratory mechanics. Clinically, these findings support individualized adjustment of MI-E parameters based on patient-specific characteristics. The lack of methodological standardization and calibration reporting limits comparability. A structured protocol for MI-E bench studies is proposed to enhance reproducibility, transparency, and translational relevance.

Close monitoring of carbon dioxide (CO₂) levels is crucial in extremely preterm neonates; however, a consensus on the optimal CO₂ thresholds is lacking. We aimed to evaluate the impact of P_aCO2 levels during the first 24 h of life on the outcomes of extremely preterm neonates ventilated with first-intention high frequency jet ventilation (HFJV).

We retrospectively examined neonates ≤26 weeks of gestational age who were ventilated with first-intention HFJV, during 2022–2024, comparing the lowest P_aCO2, peak P_aCO2, P_aCO2 fluctuations, and P_aCO2 deviation from the target (40–50 mm Hg) during the first 24 h of life between neonates who survived without severe intraventricular hemorrhage (IVH) and neonates who developed severe IVH or died.

Among 50 extremely preterm neonates of gestational age 24.3 ± 1.5 weeks and birthweight 656 ± 170 g, 33 (66%) survived without severe IVH. Neonates who survived without severe IVH were of greater gestational age (24.7 ± 1.3 vs 23.6 ± 1.5 weeks, P = .01) and birthweight (696 ± 159 vs 577 ± 167 g, P = .02), compared to neonates who developed severe IVH or died. The latter had significantly higher peak P_aCO2 (66.7 ± 17.0 vs 54.6 ± 10.2 mm Hg, P = .006), P_aCO2 fluctuations (30.8 ± 17.3 vs 16.6 ± 8.8 mm Hg, P = .001), and P_aCO2 deviation from the target (20.0 ± 14.9 vs 9.7 ± 7.3 mm Hg, P = .003), compared to neonates who survived without severe IVH. A higher peak P_aCO2, P_aCO2 fluctuation, and P_aCO2 deviation from the target were significantly associated with severe IVH, death, or severe IVH/death. A cutoff of a peak P_aCO2 <65 mm Hg, P_aCO2 fluctuation <25 mm Hg, and P_aCO2 deviation <15 mm Hg from the target had the best sensitivity and specificity for survival, absence of severe IVH, and survival without severe IVH.

In extremely preterm neonates ventilated with first-intention HFJV, maintaining peak P_aCO2 of <65 mm Hg, P_aCO2 fluctuations <25 mm Hg, and P_aCO2 deviation from target <15 mm Hg was significantly associated with survival without severe IVH.

High-flow nasal cannula (HFNC) therapy improves oxygenation and increases end-expiratory lung volume (EELV). Asymmetric cannulas are a novel interface, but their interaction with body position and breathing route (mouth open vs closed) on EELV is unclear. This study used electrical impedance tomography (EIT) to assess the impact of these factors on end-expiratory lung impedance (EELI), a surrogate for EELV, in healthy subjects.

This prospective, randomized crossover physiological study included 16 healthy volunteers who received HFNC via an asymmetric cannula. EELI was measured across different body positions (Semi-Fowler’s, High Fowler’s, flat [180°] prone, and reverse Trendelenburg, flows (40 and 60 L/min), and mouth conditions (open/closed). A linear mixed-effects model compared EELI changes from baseline.

The greatest significant increase in global EELI occurred in the reverse Trendelenburg at 60 L/min with the mouth closed (difference = 2.07, P < .001). This condition was significantly superior to most other combinations. Mouth closure was a critical factor for increasing EELI. The reverse Trendelenburg specifically enhanced EELI in dorsal lung regions at high flow with a closed mouth.

Body position, flow setting, and mouth condition significantly impacted EELV during asymmetric HFNC. The combination of the reverse Trendelenburg, high flow (60 L/min), and mouth closure resulted in the greatest increase in EELV and promoted more homogeneous lung ventilation in healthy subjects. Encouraging nasal breathing and optimizing positioning could enhance the physiological benefits of HFNC.

Lung protective ventilation strategy, aiming to decrease ventilation-induced lung injury, is based on 2 major principles: (1) ventilation at a narrow range of volume, with low plateau and driving pressures, while (2) keeping the lung open, to avoid tidal alveolar recruitment/de-recruitment. Mechanical power (MP) was developed as a single value describing energy transfer to the lungs. Energy transfer to the lung parenchyma during ventilation is associated with the viscoelastic properties of the lung. This study aimed to describe the correlation between MP and the viscoelastic properties of the lung.

An exploratory prospective study in an 18-bed mixed ICU of a university-affiliated tertiary hospital. Immediately after percutaneous tracheostomy was performed, 2 inspiratory holds were performed, with 2 different constant flows. Based on the ventilator settings, inspiratory hold measurements [including peak pressure, plateau pressure (P_plat), tidal volume], and resistive elements, viscoelastic properties of the lungs (viscoelastic resistance, R₂; viscoelastic compliance, C₂; and viscoelastic time constant, τ₂) and MP were calculated for each inspiratory hold. Those measurements were compared. MP was correlated with the viscoelastic properties of the lung.

Nine subjects were included in the study. No differences were noted in the viscoelastic properties of the lung between the 2 inspiratory hold measurements. The MP increased in the higher flow inspiratory hold. No correlation was found between either R₂ or C₂ and MP. A moderate negative correlation was found between τ₂ and MP.

MP was found to be negatively correlated with τ₂, but not with R₂ or C₂. The clinical implication of this finding has yet to be defined.

Fragmented care models for sleep medicine in Canada disadvantages individuals with socioeconomic barriers. This can lead to delays in diagnoses, treatment, and increased health care utilization. This study aimed to explore whether subjects who receive polysomnography (PSG) during hospitalization represent a marginalised population.

We identified subjects who underwent PSG during hospitalization (inpatient PSG) at an academic hospital in Canada, from January 1, 2019, to December 31, 2021. Time, age- and sex-matched control groups were derived in a 2:1 allocation ratio inclusive of: hospitalized individuals who did not undergo PSG (inpatient control) and individuals referred to an ambulatory sleep medicine clinic (clinic control). Comorbidities, socioeconomic deprivation and marginalization indices, rurality, and health care utilization within the preceding year to enrollment, were compared between groups.

We matched 275 inpatient PSG with 550 inpatient control and 550 clinic control subjects. Compared to both control groups, the inpatient PSG group had greater burden of comorbidities and more frequent specialist physician appointments. They had greater marginalization index, social assistance use, and lower income levels compared to clinic control subjects. More frequent emergency department visits, acute care admissions, and days in hospital were observed in the inpatient PSG group compared to clinic control subjects. Inpatient PSG subjects had more severe sleep disordered breathing (SDB) compared to clinic control subjects.

Subjects evaluated with in-patient PSG had a greater multimorbidity, social disadvantages, and health care usage. Future prospective trials are needed to determine whether routine use of in-patient PSGs can reduce complications associated with untreated SDB.

Proportional assist ventilation plus (PAV+) uses a work of breathing bar (WOB-Bar) to provide real-time, noninvasive estimates of patient work of breathing (WOB_pt). Although designed to guide titration during the transition to spontaneous ventilation, the clinical accuracy of this tool remains unvalidated against gold-standard measures.

This physiological randomized crossover study included 35 subjects weaning from mechanical ventilation. We compared the WOB-Bar against the esophageal pressure-time product (PTP_es-min), the pressure drop in the airway during the first 100 ms of an inspiratory effort against an occluded airway (P_0.1), and the pressure variation during an end-expiratory occlusion (P_occ) across 3 randomized assistance PAV+ levels (20%, 50%, and 70%). Effort was categorized as low, adequate, or high based on suggested physiological thresholds.

The WOB-Bar correctly classified effort (relative to PTP_es-min) in only 44.5% of cases (95% CI 32.9–56.4%), with a negligible weighted κ of 0.01. P_occ demonstrated the best performance with 66.5% agreement (95% CI 57.9–75%) and a κ of 0.35. A multivariable mixed-effects model (R² = 0.84) showed that WOB_pt (P < .001), P_0.1 (P = .040), and P_occ (P = .02) were all independent predictors of PTP_es-min. However, despite a positive association between WOB_pt and PTP_es-min, the categorical WOB-Bar showed limited accuracy and tended to underestimate respiratory effort, particularly in high-effort states. Inter-individual variability accounted for 77.5% of the total variance in respiratory effort.

The WOB-Bar frequently underestimated effort and was insufficient as a stand-alone tool for PAV+ titration. Airway occlusion maneuvers (P_occ and P_0.1) were more reliable indicators of PTP_es-min. Since current thresholds are extrapolated from healthy individuals and unvalidated during weaning, these findings are hypothesis generating. Future studies should establish context-appropriate thresholds and evaluate their clinical implications.

Digital technology has made important inroads to advance the self-management and treatment of cystic fibrosis (CF) symptoms. To date, no integrative, comprehensive, systematic review of digital technology and CF has included the application of digital technology for mental health. The purpose of the current study was to complete an up-to-date systematic review of digital technology interventions for CF across symptom monitoring, treatment adherence, airway clearance, nutrition, exercise, and mental health.

This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Articles reporting a quantitative study examining technology-based interventions for CF were included. Studies were excluded if they did not meet this criterion or if they were not written in English. PsycINFO, MEDLINE, EMBASE, and CINAHL databases were searched. Search terms included technology, CF, symptom monitoring, treatment adherence, quality of life, nutrition, exercise, and mental health.

Thirty-four studies were included in the review. Results demonstrated variable types of digital technologies, most predominantly applied to exercise. Inconsistencies were observed in terms of the effectiveness or efficacy of digital technology to address study outcomes across many application areas. Most consistent findings were found for the efficacy of digital technology applications for symptom monitoring (ie, improving early detection or prediction of pulmonary exacerbation), treatment adherence (ie, improvements in medication adherence, and nebulizer use), and mental health (ie, reductions in depression and anxiety).

Digital technology applications offer the potential for improved CF care; however, many of the existing studies show limited evidence for their effectiveness. Well-designed, methodologically robust studies are required to fully understand the utility of digital technology in CF care.

Colistimethate sodium (CMS) is increasingly being administered as aerosol therapy in mechanically ventilated patients. Although vibrating-mesh nebulizers (VMNs) are commonly used, the impact of repeated high-dose CMS administration on expiratory filter loading and circuit pressure drop has not been well defined. This study evaluated circuit deposition patterns and changes in expiratory filter pressure drop according to the nebulizer position.

A ventilator with adult settings and heated humidification was connected to an endotracheal tube and test lung. A VMN was positioned either at the Y-adapter or at the humidifier inlet. Two CMS vials (160 mg each) were diluted in 6 mL of saline and nebulized. Fourteen treatments were administered over 7 days in 5 independent experiments per group (no. = 5). Drug deposition was quantified by high-performance liquid chromatography. Pressure drop, defined as the difference between upstream and downstream pressure across the expiratory high-efficiency particulate air filter, was measured over repeated administrations and analyzed using a mixed repeated-measures model.

The nebulizer position significantly altered deposition within the ventilator circuit. Placement at the Y-adapter resulted in greater exhalation valve deposition (28.35 ± 4.83 mg vs 5.83 ± 1.51 mg, P < .001) and increased pressure drop over time. A significant time-by-position interaction was observed (P = .01), with higher pressure drop after 14 treatments. In contrast, humidifier-inlet placement was associated with greater drug accumulation within the humidifier chamber (35.59 ± 6.21%) and a smaller increase in pressure drop.

During repeated high-dose CMS administration, the nebulizer position influenced circuit deposition patterns and expiratory filter pressure drop. Placement at the Y-adapter was associated with greater expiratory limb deposition and increased filter pressure drop over time, whereas humidifier-inlet placement shifted the drug accumulation proximally within the circuit.

Physiology-based interventions, including individualized mechanical ventilation and advanced monitoring, can improve outcomes in acute respiratory failure. A multidisciplinary team dedicated to physiologic assessment has emerged to support complex ventilatory management, yet factors influencing its recognition, understanding, and utilization within large ICU systems remain unknown.

We conducted a cross-sectional, self-administered survey of ICU clinicians, including attending physicians, fellows, residents, advanced practice providers, nurses, and respiratory therapists, across multiple adult intensive care units within a large academic medical center. The survey assessed provider demographics, awareness, utilization, and perceptions of a specialized physiology-based Lung Rescue Team (LRT). Descriptive statistics were used to summarize responses and stratifiy results by provider role and years of experience.

Among 169 respondents, 62.7% reported awareness of the LRT, with awareness increasing with years of clinical experience. Of those aware, 93.4% reported moderate or high familiarity with the service, and 76.2% had requested at least 1 consultation in the prior year. Only 10.2% of respondents perceived the service as very well integrated into ICU workflows. The most frequently cited barriers to utilization were lack of awareness and uncertainty regarding consultation criteria, followed by workflow challenges and limited exposure to advanced physiologic monitoring. No respondents reported adverse patient outcomes related to consultation.

A specialized physiology-based team is perceived as valuable and safe but may be underutilized without deliberate integration strategies. Awareness, clear consultation pathways, and workflow integration are perceived as fundamental to utilization. These findings offer practical insights for institutions seeking to develop or optimize similar multidisciplinary services to advance individualized respiratory care.

Hypothermia is a common finding following prehospital trauma with important consequences. Treatment includes removal of the patient from exposure and application of a vapor barrier and blankets. The role of elevated inspired airway temperatures for rewarming has been advocated for decades with little evidence of benefit. We sought to determine if warming of inspired gas up to 44°C will increase core temperature to normothermia after hypothermia as compared with standard of care warming.

Female swine, 39.0 ± 2.5 kg, were orally intubated and placed on a mechanical ventilator (R860, GE Healthcare, Chicago, IL) with the plane of anesthesia maintained via intravenous (IV) propofol infusion. A heat and moisture exchanger (HME) was used for airway humidification and baseline measurements for all animals. After baseline vital signs, airway temperature, and core body temperature were recorded, a simulated hemorrhage was completed via a peristaltic pump. Blood was withdrawn at 1 mL/kg/min until 20% of total calculated blood volume was reached. Shed blood was anticoagulated and retained for later use. Active cooling was the accomplished via Arctic Sun 5000 Temperature Management System. Animals were then randomized to 1 of 4 warming methods: heated humidifier (HH) set at 37°C; HH set at 44°C; HME alone, and HME with warm fluids IV infusion, with 6 animals per group. Animals were wrapped in a mylar thermal blanket, warmed per the randomized warming method, and monitored for 4 hours.

The use of inspired gas temperatures up to 44°C was associated with a small increase (1.5°C) in core body temperature compared with an HME alone. However, none of the methods of rewarming returned animals to the baseline temperature after 4 hours.

Active humidification with supranormal temperatures had minimal impact on core body temperature following 4 hours of treatment.

Electrical impedance tomography (EIT) provides a noninvasive means of assessing posture-related end-expiratory lung impedance and the regional distribution of ventilation. However, the physiological effects of specific bedside postures, including the hands-on-knees and tripod positions, have not been fully characterized using EIT in spontaneously breathing individuals. We aimed to compare the end-expiratory lung impedance and regional ventilation distribution of healthy volunteers across a range of postures as a physiological proof-of-concept to inform future clinical investigations.

The regional end-expiratory lung impedances (ΔEELI) of 20 healthy male subjects who adopted the 6 following postures were compared: supine, prone, sitting, tripod, hands-on-knees, and standing. The distribution of ventilation between the dorsal and ventral lung regions was also analyzed for each posture. The Wilcoxon test with the Holm–Bonferroni correction was used to compare the datasets.

Compared with the supine posture, the hands-on-knees posture was associated with the highest global ΔEELI (3.58 units, 95% CI: 2.81–4.58, P < .001), followed by the tripod position (2.16 units, 95% CI: 1.69–3.47, P < .001). With respect to the regional ventilation, dorsal ventilation was significantly better for all other postures versus the supine posture, particularly for the hands-on-knees and tripod position (ΔEELI in the dorsal region 2.77 units, 95% CI: 2.02–3.33, and 2.02 units, 95% CI: 1.35–2.64, respectively; both P < .001).

In healthy men, the hands-on-knees and tripod postures were associated with greater global and dorsal end-expiratory lung impedance and a more dorsal ventilation distribution. Whether these physiological observations might translate to clinically meaningful improvements in patients with respiratory disease warrants further investigation in clinical studies.

PEEP affects the geometry and function of the diaphragm. During noninvasive ventilation (NIV), applying inspiratory positive airway pressure (IPAP) in addition to expiratory positive airway pressure (EPAP) may further affect diaphragm thickness. Therefore, this study aimed to investigate the acute effects of IPAP and EPAP on the diaphragm thickness in healthy individuals during baseline, as assessed using ultrasound (US).

This physiological study was conducted using a randomized, double-blind, crossover design and included individuals aged 18–50 years. Participants with a history of smoking or other preexisting conditions were excluded. Diaphragm thickening was assessed via US during baseline under 6 conditions without positive pressure (EPAP and IPAP of 0 cm H₂O); EPAP of 5, 10, and 15 cm H₂O without IPAP; and IPAP of 10, 12, and 15 cm H₂O combined with EPAP of 5 cm H₂O.

Data were collected from 90 participants during baseline, with a mean age of 23.2 years and a mean body mass index of 23.9 kg/m². Compared with baseline without positive pressure, EPAP levels of 10 and 15 cm H₂O significantly increased both end-expiratory diaphragm thickness (T_di,ee) and end-inspiratory diaphragm thickness (T_di,ei) (P < .05 for both). Similarly, an IPAP of 15 cm H₂O combined with an EPAP of 5 cm H₂O significantly increased T_di,ei (P < .05). Despite these effects, only IPAP at 15 cm H₂O led to a significant increase in the diaphragm thickening fraction (TF_di) (P < .05).

EPAP levels of 10 cm H₂O or higher and an IPAP level of 15 cm H₂O during NIV significantly affect diaphragm thickness, likely because of their impact on lung volumes. Therefore, standardization of diaphragm thickness monitoring at lower EPAP and IPAP levels is recommended to minimize confounding effects between positive pressure and muscle contraction–induced thickness changes.