Tidal Volume Research Articles

Background Infants of asthmatic mothers have reduced lung function in early life for reasons that remain to be defined. The association between inhaled corticosteroid (ICS) use during pregnancy and lung function in the offspring has not been investigated. Objectives To investigate the association between ICS use during pregnancy and infant lung function. Methods Multivariable regression analysis of infant lung function at 4–6 weeks (tidal breathing flow volume loops and functional residual capacity (FRC)) associated with use of ICS during pregnancy. Results Among infants born to asthmatic mothers, the ratio of time to peak tidal expiratory flow to expiratory time (tPTEF:tE), corrected for end-expiratory lung volume (FRC), was improved in offsprings whose mothers used ICS during pregnancy compared with those who did not (n=161 ICS use vs n=25 no ICS use; coefficient 0.06 /mL, 95% CI 0.01 to 0.11, p=0.014). Compared with a control group of infants born to non-asthmatic mothers, there was a lower tPTEF:tE to FRC ratio in infants born to asthmatic mothers without ICS use (n=46 no asthma vs n=25 asthma no ICS use; coefficient −0.08 /mL, 95% CI −0.01 to −0.02, p=0.012) but not in infants born to asthmatic mothers with ICS use (n=46 no asthma vs n=161 asthma ICS use; coefficient −0.02 /mL, 95% CI −0.06 to 0.03, p=0.453). Conclusions The association between maternal asthma and impaired infant lung function diminished in infants whose mothers used ICS during pregnancy. Trial registration Australian New Zealand Clinical Trials Registry ACTRN12613000202763.

Differences in mechanical ventilation strategies between patients with and without acute brain injury (ABI) remain incompletely characterized. We aimed to compare ventilation approaches in patients with and without ABI over a 10-year period and to investigate impacts of practice changes on Pao2 and Paco2. Retrospective registry-based cohort study involving prospectively collected data from nine ICUs across Toronto, Ontario, Canada. Adult patients (≥ 18 yr) receiving invasive ventilation for at least 48 hours from 2014 to 2023 were included. Patients were classified as having ABI (exposure) or non-ABI (comparator) conditions. Between-group differences in tidal volume (Vt), positive end-expiratory pressure (PEEP), Paco2, and Pao2 were summarized using adjusted linear mixed-effects regression. Six additional ventilation and gas exchange variables were evaluated in unadjusted analyses. None. Thirteen thousand nine hundred twenty-five patients were included. Mean age (sd) was 59.1 years (17.5 yr), 38.1% of patients (n = 5305) were female, and 25.2% had ABI (n = 3503). Over the first 7 ventilation days, Vt was comparable between groups, with a daily median close to 6 mL/kg (interquartile range, 6-7 mL/kg) predicted body weight. PEEP was significantly lower in patients with ABI (median 5 vs. 8 cm H2O in non-ABI patients; p < 0.001). Among patients with hypoxemic respiratory failure, PEEP remained significantly lower in the ABI subset. From 2014 to 2023, Vt decreased slightly in both groups, while PEEP remained unchanged. Paco2 was largely maintained within 35-45 mm Hg in ABI patients and Pao2 remained largely within 80-120 mm Hg. Differences in six additional ventilation parameters between groups were minimal. Both ABI and non-ABI patients received comparable Vt that trended downwards over time. Paco2 and Pao2 remained largely within guideline-recommended ranges. However, PEEP was significantly lower in ABI patients, including among those with hypoxemic respiratory failure, highlighting potential opportunities to improve PEEP application in relevant subsets.

The effect of flow-controlled ventilation (FCV) as compared with volume-controlled ventilation (VCV) on oxygenation and respiratory system mechanics in patients undergoing one-lung ventilation (OLV) is unknown. To test the hypothesis that FCV would improve oxygenation and respiratory system mechanics compared with VCV during OLV. Two-centre, two-arm, randomised controlled clinical trial. University hospital and speciality hospital for pulmonary diseases in Germany. A total of 78 thoracic surgery patients undergoing OLV for more than 30 min. Patients were randomly assigned to OLV with FCV (n = 39), or VCV (n = 39). In both groups, OLV was conducted with tidal volume of 5 ml kg-1, positive end-expiratory pressure of 5 cmH2O, respiratory rate to normocapnia, and inspiratory oxygen fraction of 1.0. The primary outcome was the arterial partial pressure of oxygen (PaO2) 20 min after initiation of OLV. The secondary outcomes included respiratory system mechanics, the need for rescue due to hypoxaemia, and clinical outcome variables. The partial pressure of arterial oxygen did not differ between FCV and VCV at 20 min after starting OLV (PaO2: 24.8 ± 14.8 kPa vs. 26.1 ± 15.9 kPa, mean difference -1.2 (95% confidence interval -8.2 to 5.7), P = 0.721), while mechanical power was lower during FCV compared with VCV. Other variables did not differ at any time thereafter, except for the compliance of the respiratory system at end of surgery. The need for rescue manoeuvres due to hypoxemia or hypercapnia during OLV did not differ between the groups. The incidence of postoperative pulmonary and extrapulmonary complications, as well as the number of hospital-free days at day 30 after surgery, did not differ between FCV and VCV. Compared with VCV in thoracic surgery patients, FCV did not improve oxygenation or respiratory system mechanics during OLV, nor was it associated with improved outcomes.

Background: Respiratory exercises play a key role in rehabilitation programs, especially for older adults and individuals with chronic pulmonary conditions. Despite growing interest in wearable sensors for home-based care, structured reference metrics to quantitatively characterize respiratory exercises are still limited. This study aimed to provide a quantitative characterization of respiratory exercises and evaluate the level of agreement between a low-cost prototypical sensor and a commercial one. Methods: Eleven older adults (9 females; age = 72.6 ± 5.0 years; height = 1.66 ± 0.09 m; mass = 68 ± 10 kg) performed a structured respiratory exercises protocol. Algorithms were developed to identify respiratory cycles, their execution time, and parameters related to respiratory capacity, using accelerometer signals from the two wearable sensors placed on the rib cage. Results: The average respiratory cycle duration ranged from 2.8 to 4.3 s, with normalized inspiratory and expiratory peaks. Tidal volume variability was minimal, confirming consistency in breathing patterns across exercises. User comfort was high (mean VAS = 8.7). Sensor comparison confirmed strong agreement between the two sensors in detecting respiratory cycles, though some variability was observed in timing and tidal volume estimation. Conclusions: These findings suggest that even simple accelerometers can reliably capture key respiratory parameters, supporting the feasibility of using wearable sensors to monitor structured respiratory exercises performed in home-based settings.

Introduction/Background: Manual ventilation is a critical, yet variable skill in prehospital and hospital care. Concerns of over-ventilation (tidal volume, rate, etc.) during bag-valve-mask (BVM) ventilation have led many EMS systems to adopt smaller resuscitator bags, with the risk of underventilation. Research Question/Hypothesis: Can a small adult bag provide adequate ventilation for an average adult male, and can performance be improved after a brief educational intervention using software to measure flow and tidal volume, along with a flow limiting device to encourage more aggressive bag compression to achieve adequate tidal volume, while preventing over-ventilation by mechanically limiting inspiratory flow. Methods/Approach: 55 first responders from Johnson County, KS participated in a pre/post study. Participants were instructed to provide 60 seconds of manual ventilation to a simulated healthy adult male (target Vt: 420-570 ml) using their standard small adult bag (VENTLAB AirFlow 1000 mL). Tidal volume (Vt), peak flow rate, and respiratory rate (RR) were recorded (SotairIQ training platform; SafeBVM, Boston). Afterward, providers completed a 2-minute training video and 1-minute hands-on flow training with a valve which stops inspiratory flow if it exceeds 55 LPM (Sotair, SafeBVM, Boston) and SotairIQ. They then repeated the same task using the same bag with the Sotair inline. Results/Data: Mean peak flow rates and Vt were higher after training (44.5+5.2 vs 28.3+12 LPM; p&lt;0.05; 418+38.6 vs 323.2+92.2 ml; p&lt;0.05). Before training, 87.8% of breaths were &lt;420 mL compared to 51.5% post-training (p&lt;0.05). Baseline respiratory rate was 9.73+2.49, compared to 11.8+4.36 after training; p&lt;0.05. Estimated alveolar ventilation (assuming a dead space of 150 ml) increased from 1776.7 to 3409.7 ml/minute after training (p&lt;.0.05). Conclusion(s): The small adult bag (1,000 ml) leads to smaller tidal volumes than recommended for an average adult male; and (2) although the training tool (+ flow-limiting device) led to a near doubling in estimated alveolar ventilation, many breaths were still suboptimal after training. These results provide further evidence for the inadequacy of small bags in ventilating adults, but suggest that training and the use of a flow-limiting device may improve the quality of ventilation when a small bag is used..

Background: Ventilation during cardiopulmonary resuscitation may affect cardiac arrest management and outcome. Novel strategies such as head and thorax elevation (HTE) and the use of an impedance threshold device (ITD) have been developed to enhance circulation during CPR. However, the impact of these strategies on ventilation during CPR remains poorly understood. Research Question: To describe and understand the impact on ventilation and lung volumes of horizontal (FLAT) versus HTE positions, with or without ITD use, across multiple experimental models. Methods: This was a cross-over experimental trial conducted using three cardiac arrest models: pigs, Thiel-embalmed cadavers, and thawed fresh-frozen cadavers. Two protocols were applied in randomized order: FLAT and HTE positions, with or without ITD. CPR was standardized with a mechanical suction-cup based chest compression device and volume-controlled ventilation. Primary outcome was the calculation of absolute loss of lung volume (Vloss) below the functional residual capacity during CPR, estimated by measuring the difference between inspiratory tidal volume and expiratory tidal volume for the two consecutive respiratory cycles following interruption of chest compressions for each sequence. We also calculated airway opening pressure (AOP) and respiratory system compliance (Crs), both assessed before CPR initiation. Linear mixed models were used for statistical analysis. Results: Eight pigs and eight cadavers (4 Thiel, 4 fresh-frozen) were included. In the cadaver model, Vloss was 178.13 ± 168.19 in the FLAT position and 84.25 ± 112.87 mL in the HTE (p = 0.74). With ITD, Vloss was 192.75 ± 221.02 mL in the FLAT position and 148.5 ± 187.38 mL in the HTE position (p = 0.95). In the pig model, Vloss was 42.5 ± 31.7 mL in the FLAT position and 38.75 ± 44.77 mL in the HTE (p = 0.74). With ITD, Vloss was 104.62 ± 66.56 mL in the FLAT position and 105.13 ± 62.35 mL in the HTE position (p = 0.84). AOP was significantly lower in HTE vs. FLAT: 5.85 (2.85–10.25) vs. 8.05 (6.38–11.50) cmH2O (p = 0.042). Crs was not significantly different in HTE: 30.91 (21.25–34.44) vs. 26.24 (24.04–30.32) mL/cmH2O (p = 0.197). Conclusions: In the present animal and cadaver models, head and thorax elevation during CPR trends to reduce airway opening pressure and improve loss of lung volume above functional residual capacity. These observations contribute to already reported effect of head and thorax elevation and ITD.

Background: Respirator masks are widely used in East Asia for air pollution and, since COVID-19, in public health. However, their physiological impact during exercise remains poorly understood. We evaluates cardiopulmonary responses to exercise under three conditions: no mask, KF80 (Korean Filter; ≥80% filtration of 0.6 μm particles), and KF94 (≥94% filtration of 0.4 μm particles; functionally equivalent to N95). Methods: Forty healthy adults (mean age 33.3 ± 7.2 years, 50% female) underwent a randomized crossover trial, performing cardiopulmonary exercise testing (CPET) using a modified Bruce protocol under no mask, KF80, and KF94. Each session was separated by ≥48 hours. Gas exchange and physiological variables were measured in real time. Outcomes included peak oxygen uptake (VO 2 max), metabolic equivalents (METs), heart rate (HR), tidal volume (VT), minute ventilation (VE), respiratory rate (RR), respiratory exchange ratio (RER), oxygen saturation (SpO 2 ), and systolic blood pressure (SBP). Repeated-measures ANOVA with Bonferroni correction was applied. Results: VO 2 max and METs both declined with greater filtration: VO 2 max was 35.6 ± 8.7 ml/kg/min (No Mask), 31.0 ± 6.5 (KF80), and 29.9 ± 8.0 (KF94; p &lt; 0.001); METs were 7.8 ± 1.3, 6.8 ± 1.2, and 6.2 ± 1.4, respectively ( p &lt; 0.001). Maximal HR decreased from 181.9 ± 15.7 bpm (No Mask) to 176.6 ± 15.9 (KF80) and 171.0 ± 15.3 (KF94; p &lt; 0.001). At 3-min post-exercise, HR remained lower under KF94 (104.2 ± 20.8 bpm) than No Mask (112.6 ± 21.5; p = 0.026), suggesting delayed autonomic recovery. SpO 2 at VO 2 max declined under KF94 (91.8 ± 4.3%) relative to No Mask (94.1 ± 3.0%) and KF80 (93.0 ± 4.2%; p = 0.012); 9 of 40 subjects experienced SpO 2 &lt; 80%. All ventilatory measures declined with increased mask filtration: VE was 66.4 ± 24.3 (No Mask), 43.0 ± 16.8 (KF80), 35.2 ± 15.6 L/min (KF94; p &lt; 0.001); VT was 1.9 ± 0.6, 1.4 ± 0.6, and 1.2 ± 0.4 L ( p &lt; 0.001); and RR was 35.6 ± 8.7, 31.0 ± 6.5, and 29.9 ± 8.0 bpm ( p &lt; 0.01). RER remained unchanged across conditions ( p = 0.24), suggesting consistent metabolic substrate utilization and comparable anaerobic thresholds. Conclusion: KF94 respirators reduce aerobic capacity, maximal HR, and ventilatory efficiency in healthy adults without causing hemodynamic instability. Reduced VO 2 max, blunted HR response, and episodes of desaturation underscore performance trade-offs. These findings support cautious mask use during exertion within evolving post-pandemic health policy.

Background: Hemorrhagic shock, precipitated by rapid blood loss, is highly lethal. Successful treatment requires rapid stabilization to prevent mortality. Ventilatory support may be required when accompanied by respiratory failure, and in austere prehospital settings is most likely to occur via manual bagging, which carries risks of barotrauma and hemodynamic compromise. Airway flow limiting devices can facilitate correct manual ventilation, but their utility in the hemorrhagic shock resuscitation setting is not well established. Objective: Evaluate the use of an airway flow limiting device on manual ventilation performance and hemodynamics in a preclinical model of hemorrhagic shock resuscitation. Methods: We sedated, anesthetized and intubated 20 mixed-breed Yorkshire swine, mean(SD) weight 53.1(4) kg. Animals were mechanically ventilated at 8mL/kg while undergoing instrumentation (pressure transducer in descending aorta via femoral cutdown for assessing mean arterial pressure (MAP) and systolic blood pressure (SBP)). Airway flow, pressure (P AW ) and tidal volume (V T ) were monitored continuously. We bled animals in 60cc draws until MAP &lt;40mmHg, and then commenced manual bagging, with animals randomized to standard ventilation (“SHAM”) or flow modulated ventilation (“FM”; Sotair, SafeBVM, Inc). Respiratory rate was guided by a metronome, dynamically adjusted to maintain eucapnia. After 30 min, all withdrawn blood was returned and bagging continued for another 30 min. Performance and hemodynamic parameters were compared between groups and across shock&amp;resuscitation phases (t-tests; ANOVA). a = 0.05 was the threshold for statistical significance. Results: Fourteen pigs survived initial hemorrhage until randomization (1 animal arrested during resuscitation) and initiation of bagging (FM, n = 7; SHAM, n = 7). Airway performance parameters differed between FM and SHAM (p&lt;0.001). MAP and SBP did not differ between FM and SHAM groups but differed between phases (p&lt;0.001). Conclusions: Bagged ventilations with a flow modulation device resulted in more favorable ventilation performance, but no differences in hemodynamics during hemorrhagic shock/resuscitation.

Background: The efficacy of different conventional ventilation during automated head-up (AHUP) CPR using active decompression and impedance threshold device with head and torso elevation is unknown. We sought to determine the central and peripheral hemodynamics while using the 10:1 versus the 30:2 positive pressure ventilation (PPV). Research Question: Does the PPV delivery method affect the hemodynamics during AHUP-CPR? Methods: Ventricular fibrillation was induced in anesthetized pigs (n=5), followed by AHUP-CPR initiation with positive pressure ventilations applied using an automated bag compressor to deliver 10ml/kg of tidal volume over 1 sec at a rate of 10 breaths/min. After 15 minutes of CPR using a 10:1 ratio, ventilation was changed to a 30:2 ratio for 2 minutes with 2 PPV delivered consecutively. Thereafter 10:1 ratio was resumed followed by another 2-minute round of 30:2 PPV mode. Intraventricular pressures and volumes using conductance catheters placed in the right ventricle (RV), along with other hemodynamic parameters were recorded continuously, during the 2-minute intervals between PPV delivery. A mixed-effects model was used to evaluate the effects of PPV mode on pressure-volume (PV) loop parameters while using a Spearman correlation to explore the relationship between PV loop indices. Results: There was no statistically significant difference between RV stroke volume (SV) with 10:1 versus 30:2 PPV mode (Table 1). Throughout 2 minutes, 30:2 ventilation mode resulted in a significantly higher end-tidal CO2 (ETCO2), and higher pressures with a higher pulmonary elastance (Ea) imposed on RV (p&lt;0.05). Higher Ea was strongly correlated with lower SV and ETCO2 (Spearman's rho correlation confidence of -0.97 and -0.83, respectively). No significant differences were observed between the two ventilation modes in any other hemodynamic parameters, including intrathoracic, aortic and right atrial pressures, as well as coronary and cerebral perfusion pressures. Conclusion: No significant difference was found for right ventricular stroke volume when comparing one breath after 10 chest compressions to two breaths after 30 compressions during automated head-up CPR. Delivering two consecutive breaths after 30 continuous compressions led to an overall higher ETCO2, but it also imposed greater ventricular pressure and afterload, which were significantly correlated with reduced SV and ETCO2.

Pulmonary fibrosis (PF) is a chronic interstitial lung disease characterized by excessive collagen deposition and progressive loss of lung compliance. The prognosis is usually poor and therapeutic options are limited. Recurrent damage to the alveolar surfactant lipid-producing type 2 cells (T2C) is a key driver of PF initiation. Recent data from our lab has showed that mice with T2C-specific loss of low-density lipoprotein receptor-related protein-1 (SPC-LRP1 -/- ) exhibit reduced pulmonary compliance and decreased levels of surfactant lipids at baseline. We hypothesized that LRP1 deficiency in T2C predisposes the alveolar environment to fibrotic remodeling. We challenged 6-months old wild-type (WT) and SPC-LRP1 -/- male mice with repeated low-dose bleomycin (BLM), a well-established profibrotic agent. Mice were euthanized 33 days after the initiation of the BLM challenge. Inflammation was monitored through weekly body weight measurements and by bronchoalveolar lavage (BAL) protein concentration after euthanasia. Pulmonary function was evaluated longitudinally and after euthanasia. Paraffin sections were prepared, pulmonary fibrosis was assessed using the Ashcroft Grade scoring system, and emphysema was quantified via mean linear intercept (MLI). BAL lipid composition was analyzed using mass spectrometry. As the BLM challenge progressed, WT mice showed increased tidal volume and peak inspiratory flow, while the timing between early and late expiration was reduced. In contrast SPC-LRP1 -/- mice showed increased expiratory time and end expiratory pause, with decreased respiratory frequency. Despite these differences, static compliance, inspiratory capacity and forced vital capacity were similarly decreased in both WT and SPC-LRP1 -/- mice at the end of the BLM challenge, which suggested similar restrictive defects in pulmonary function. However, histological analysis showed higher degree of fibrosis and decreased MLI in SPC-LRP1 -/- mice, depicting coexisting emphysematous and fibrotic remodeling. BAL lipid profiling showed lower concentration of surfactant phosphatidylcholine (PC) and of other lipid groups in SPC-LRP1 -/- than in WT mice, suggesting impaired T2C surfactant lipid metabolism. SPC-LRP1 -/- also had higher BAL protein concentration than WT mice, indicating increased inflammation. The data suggest that loss of LRP1 in T2C promotes emphysema and exacerbates BLM-induced fibrosis and inflammation.

Introduction: Current pediatric cardiopulmonary resuscitation (CPR) guidelines recommend that a rescuer performs manual ventilation at a rate of 20-30 breaths per minute (bpm) with an avoidance of excessive ventilation during CPR. Despite these recommendations, excessive ventilation is common during CPR, and performing manual ventilation can be difficult in settings with limited personnel. Using mechanical ventilation during CPR can provide relatively constant minute ventilation and offloads a rescuer to perform other tasks. Research Question: Does mechanical ventilation produce similar gas exchange and intra-arrest hemodynamics compared to manual ventilation during CPR? Aims: To compare gas exchange and intra-arrest hemodynamics when using manual ventilation versus three mechanical ventilation strategies: sustained inflation (SI), pressure-controlled mechanical ventilation (PCV), and volume-controlled mechanical ventilation (VCV). Methods: This was a randomized, crossover study design. Twenty 4-5 kg swine were anesthetized and underwent up to 4 episodes of 1 minute of ventricular fibrillation-induced (VF) cardiac arrest and resuscitation. Each swine was assigned 4 different intra-arrest ventilatory strategies in random order including: 1) manual ventilation at a rate of 25 bpm, 2) SI at 15 cm H 2 O, 3) PCV using pre-arrest peak inspiratory pressures, and 4) VCV using a pre-arrest tidal volume. Swine were resuscitated with chest compressions at 120 compressions per minute, epinephrine administration every 4 minutes, and defibrillation as clinically indicated starting 8 minutes into resuscitation. Arterial blood gases were obtained at baseline and at 4 and 8 min of resuscitation. Arterial diastolic blood pressure (DBP), myocardial perfusion pressure (MPP), and cerebral perfusion pressure (CPP) were measured at baseline and continuously during resuscitation. Results: The twenty swine underwent a total of 32 VF cardiac arrests and resuscitation. At 4 and 8 minutes of CPR, SI, PCV, and VCV produced PaCO 2 and PaO 2 levels similar to that of manual ventilation ( Figure 1 ). DBP, MPP, and CPP levels were also similar among the 4 groups at 4 and 8 minutes of resuscitation ( Figure 2 ). Conclusion: In this swine model of short VF pediatric cardiac arrest, sustained inflation, pressure-controlled and volume-controlled mechanical ventilation are feasible and provide adequate gas exchange and similar hemodynamics compared to manual ventilation.

Opioid-related overdose deaths involving benzodiazepines have increased in recent years, and prior studies have reported that clinically used benzodiazepines can enhance the respiratory-depressant effects of mu opioid receptor (MOR) agonists. TPA023B is an α1-sparing GABAA positive allosteric modulator developed as a potential anxiolytic with fewer benzodiazepine-typical side effects. However, it is unknown if and to what degree TPA023B can affect MOR-agonist induced respiratory depression. The current study compared the effects of either TPA023B or midazolam, alone and combined with fentanyl, on respiratory depression in rats, using whole-body plethysmography. Male Sprague-Dawley rats were implanted with chronic indwelling intravenous (i.v.) catheters for drug infusions. Respiration (frequency, tidal volume, and minute volume) was measured using whole-body plethysmography. The tests consisted of a pretreatment (midazolam, 30mg/kg; i.v.; TPA023B, 1.0mg/kg; i.v; or vehicle) followed by a fentanyl injection (0.01, 0.03, 0.1mg/kg, i.v., or vehicle) and 60min of respiration assessment. Overall, fentanyl alone, but not TPA023B or midazolam alone, produced dose-dependent reductions in tidal volume and minute volume. When administered as pre-treatments, neither midazolam nor TPA023B increased the magnitude of fentanyl-induced respiratory depression, instead producing prolonged reductions in tidal volume and minute volume. Midazolam produced a more sustained reduction in these parameters than TPA023B. Benzodiazepines prolong fentanyl-induced respiratory depression, but this effect may be reduced by eliminating activity at α1GABAA receptor subtypes.

Diaphragm pacing elicits respiratory plasticity in awake rodents after C2 hemisection.

Endotracheal tube (ETT) cuff pressures that exceed 20-30 cmH2O may lead to iatrogenic adverse effects such as cough, sore throat, and tracheal edema or more serious complications including tracheal stenosis, recurrent laryngeal nerve injury, and tracheal rupture. The current study evaluates a novel technique, titration of the ratio of expiratory to inspiratory tidal volumes (TV), to regulate intracuff pressure. This prospective, cross-over trial measured intracuff pressure in a cohort of pediatric patients presenting for general anesthesia with an ETT. Intracuff pressure was measured following adjustment of the expiratory to inspiratory TV to various ratios (1.0, 0.9, and 0.8) by slow removal of air from the ETT cuff. The study cohort included 50 patients with a median age of 12 years. At baseline continuous positive airway pressure (CPAP), the median (IQR) intracuff pressure was 20.4 cmH2O (13.6, 28.8). The intracuff pressure decreased to 12.2 cmH2O (10.2, 18.4) at an expired tidal volume (TVe) to inspired tidal volume (TVi) ratio of 1, 8.9 cmH2O (7.4, 10.9) at 0.9, and to 8.2 cmH2O (6.8, 9.5) at a ratio of 0.8. With both the CPAP method and TVe/TVi ratio of 1, there were cuff pressures greater than 30 cmH2O (10 with CPAP and 2 with TVe/TVi ratio of 1). With a TVe/TVi ratio of 0.9 or 0.8, there were no cuff pressures greater than 30 cmH2O. Adjustment of the TVe/TVi may be a more effective means of ensuring that the cuff pressure is in the desired range than other conventionally used clinical techniques such as sealing the airway to a CPAP of 20 cmH2O. ClinicalTrials.gov: NCT02768831.

Association of preoperative nocturnal hypoxaemia nadir and fentanyl ventilatory sensitivity in children with obstructive sleep apnoea undergoing general anaesthesia: a multicentre clinical cohort study.

Eupneic respiratory pattern and ventilatory responses to environmental CO2 in a small lizard, Anolis carolinensis.

Positive end-expiratory pressure optimization with esophageal pressure during prone position in severe acute respiratory distress syndrome: a physiologic study.

Efficacy of Liuzijue Qigong combined with conventional respiratory rehabilitation after thoracoscopic pulmonary nodule resection: A randomized clinical trial.

Non-invasive tidal volume estimation with wearable sensors using a high-gain observer and deep learning.

Patient 3: despite being maintained on a mandatory ventilation mode for 7 years, tidal volumes of 950 mL were achieved following a period of diaphragmatic conditioning.