Effect of Very-High-Flow Nasal Therapy on Airway Pressure and End-Expiratory Lung Impedance in Healthy Volunteers

Digital Twins of Acute Hypoxemic Respiratory Failure Patients Suggest a Mechanistic Basis for Success and Failure of Noninvasive Ventilation

OBJECTIVES

To clarify the mechanistic basis for the success or failure of noninvasive ventilation (NIV) in acute hypoxemic respiratory failure (AHRF).

DESIGN

We created digital twins based on mechanistic computational models of individual patients with AHRF.

SETTING

Interdisciplinary Collaboration in Systems Medicine Research Network.

SUBJECTS

We used individual patient data from 30 moderate-to-severe AHRF patients who had failed high-flow nasal cannula (HFNC) therapy and subsequently underwent a trial of NIV.

INTERVENTIONS

Using the digital twins, we evaluated lung mechanics, quantified the separate contributions of external support and patient respiratory effort to lung injury indices, and investigated their relative impact on NIV success or failure.

MEASUREMENTS AND MAIN RESULTS

In digital twins of patients who successfully completed/failed NIV, after 2 hours of the trial the mean (sd) of the change in total lung stress was -10.9 (6.2)/-0.35 (3.38) cm H2O, mechanical power -13.4 (12.2)/-1.0 (5.4) J/min, and total lung strain 0.02 (0.24)/0.16 (0.30). In the digital twins, positive end-expiratory pressure (PEEP) produced by HFNC was similar to that set during NIV. In digital twins of patients who failed NIV vs. those who succeeded, intrinsic PEEP was 3.5 (0.6) vs. 2.3 (0.8) cm H2O, inspiratory pressure support was 8.3 (5.9) vs. 22.3 (7.2) cm H2O, and tidal volume was 10.9 (1.2) vs. 9.4 (1.8) mL/kg. In digital twins, successful NIV increased respiratory system compliance +25.0 (16.4) mL/cm H2O, lowered inspiratory muscle pressure -9.7 (9.6) cm H2O, and reduced the contribution of patient spontaneous breathing to total driving pressure by 57.0%.

CONCLUSIONS

In digital twins of AHRF patients, successful NIV improved lung mechanics, lowering respiratory effort and indices associated with lung injury. NIV failed in patients for whom only low levels of positive inspiratory pressure support could be applied without risking patient self-inflicted lung injury due to excessive tidal volumes.

The Role of High Flow Nasal Therapy in Chronic Respiratory Failure

High-flow nasal therapy (HFNT) has an increasing role in the management of acute hypoxic respiratory failure. Due to its tolerable interface and ease of use, its role in chronic hypercapnic respiratory failure (CHRF) is emerging. This article examines the literature to date surrounding the short and long-term mechanisms of HFNT in sleep and wakefulness of CHRF patients. It is likely HFNT will have an increasing role in those patients intolerant of non-invasive ventilation.

High-flow nasal cannula oxygen versus noninvasive ventilation for the management of acute cardiogenic pulmonary edema: a randomized controlled pilot study

BACKGROUND

Whether high-flow nasal oxygen can improve clinical signs of acute respiratory failure in acute heart failure (AHF) is uncertain.

OBJECTIVE

To compare the effect of high-flow oxygen with noninvasive ventilation (NIV) on respiratory rate in patients admitted to an emergency department (ED) for AHF-related acute respiratory failure.

DESIGN, SETTINGS AND PARTICIPANTS

Multicenter, randomized pilot study in three French EDs. Adult patients with acute respiratory failure due to suspected AHF were included. Key exclusion criteria were urgent need for intubation, Glasgow Coma Scale <13 points or hemodynamic instability.

INTERVENTION

Patients were randomly assigned to receive high-flow oxygen (minimum 50 l/min) or noninvasive bilevel positive pressure ventilation.

OUTCOMES MEASURE

The primary outcome was change in respiratory rate within the first hour of treatment and was analyzed with a linear mixed model. Secondary outcomes included changes in pulse oximetry, heart rate, blood pressure, blood gas samples, comfort, treatment failure and mortality.

MAIN RESULTS

Among the 145 eligible patients in the three participating centers, 60 patients were included in the analysis [median age 86 (interquartile range (IQR), 90; 92) years]. There was a median respiratory rate of 30.5 (IQR, 28; 33) and 29.5 (IQR, 27; 35) breaths/min in the high-flow oxygen and NIV groups respectively, with a median change of -10 (IQR, -12; -8) with high-flow nasal oxygen and -7 (IQR, -11; -5) breaths/min with NIV [estimated difference -2.6 breaths/min (95% confidence interval (CI), -0.5-5.7), P  = 0.052] at 60 min. There was a median SpO 2 of 95 (IQR, 92; 97) and 96 (IQR, 93; 97) in the high-flow oxygen and NIV groups respectively, with a median change at 60 min of 2 (IQR, 0; 5) with high-flow nasal oxygen and 2 (IQR, -1; 5) % with NIV [estimated difference 0.8% (95% CI, -1.1-2.8), P  = 0.60]. PaO 2 , PaCO 2 and pH did not differ at 1 h between groups, nor did treatment failure, intubation and mortality rates.

CONCLUSION

In this pilot study, we did not observe a statistically significant difference in changes in respiratory rate among patients with acute respiratory failure due to AHF and managed with high-flow oxygen or NIV. However, the point estimate and its large confidence interval may suggest a benefit of high-flow oxygen.

TRIAL REGISTRATION

NCT04971213 ( https://clinicaltrials.gov ).

Automated oxygen titration with non-invasive ventilation in hypoxaemic adults with cardiorespiratory disease: a randomised cross-over trial

BACKGROUND

Closed-loop oxygen control systems automatically adjust the fraction of inspired oxygen (FiO2) to maintain oxygen saturation (SpO2) within a predetermined target range. Their performance with low and high-flow oxygen therapies, but not with non-invasive ventilation, has been established. We compared the effect of automated oxygen on achieving and maintaining a target SpO2 range with nasal high flow (NHF), bilevel positive airway pressure (bilevel) and continuous positive airway pressure (CPAP), in stable hypoxaemic patients with chronic cardiorespiratory disease.

METHODS

In this open-label, three-way cross-over trial, participants with resting hypoxaemia (n=12) received each of NHF, bilevel and CPAP treatments, in random order, with automated oxygen titrated for 10 min, followed by 36 min of standardised manual oxygen adjustments. The primary outcome was the time taken to reach target SpO2 range (92%-96%). Secondary outcomes included time spent within target range and physiological responses to automated and manual oxygen adjustments.

RESULTS

Two participants were randomised to each of six possible treatment orders. During automated oxygen control (n=12), the mean (±SD) time to reach target range was 114.8 (±87.9), 56.6 (±47.7) and 67.3 (±61) seconds for NHF, bilevel and CPAP, respectively, mean difference 58.3 (95% CI 25.0 to 91.5; p=0.002) and 47.5 (95% CI 14.3 to 80.7; p=0.007) seconds for bilevel and CPAP versus NHF, respectively. Proportions of time spent within target range were 68.5% (±16.3), 65.6% (±28.7) and 74.7% (±22.6) for NHF, bilevel and CPAP, respectively.Manually increasing, then decreasing, the FiO2 resulted in similar increases and then decreases in SpO2 and transcutaneous carbon dioxide (PtCO2) with NHF, bilevel and CPAP.

CONCLUSION

The target SpO2 range was achieved more quickly when automated oxygen control was initiated with bilevel and CPAP compared with NHF while time spent within the range across the three therapies was similar. Manually changing the FiO2 had similar effects on SpO2 and PtCO2 across each of the three therapies.

TRIAL REGISTRATION NUMBER

ACTRN12622000433707.

Pre-oxygenation with high-flow oxygen through the nasopharyngeal airway compared to facemask on carbon dioxide clearance in emergency adults: a prospective randomized non-blinded clinical trial

INTRODUCTION

Before tracheal intubation, it is essential to provide sufficient oxygen reserve for emergency patients with full stomachs. Recent studies have demonstrated that high-flow nasal oxygen (HFNO) effectively pre-oxygenates and prolongs apneic oxygenation during tracheal intubation. Despite its effectiveness, the use of HFNO remains controversial due to concerns regarding carbon dioxide clearance. The air leakage and unknown upper airway obstruction during HFNO therapy cause reduced oxygen flow above the vocal cords, possibly weaken the carbon dioxide clearance.

METHODS

Patients requiring emergency surgery who had fasted < 8 h and not drunk < 2 h were randomly assigned to the high-flow group, who received 100% oxygen at 30-60 L/min through nasopharyngeal airway (NPA), or the mask group, who received 100% oxygen at 8 L/min. PaO2 and PaCO2 were measured immediately before pre-oxygenation (T0), anesthesia induction (T1), tracheal intubation (T2), and mechanical ventilation (T3). The gastric antrum's cross-sectional area (CSA) was measured using ultrasound technology at T0, T1, and T3. Details of complications, including hypoxemia, reflux, nasopharyngeal bleeding, postoperative pulmonary infection, postoperative nausea and vomiting (PONV), and postoperative nasopharyngeal pain, were recorded. The primary outcomes were PaCO2 measured at T1, T2, and T3. The secondary outcomes included PaO2 at T1, T2, and T3, CSA at T1 and T3, and complications happened during this trial.

RESULTS

Pre-oxygenation was administered by high-flow oxygen through NPA (n = 58) or facemask (n = 57) to 115 patients. The mean (SD) PaCO2 was 32.3 (6.7) mmHg in the high-flow group and 34.6 (5.2) mmHg in the mask group (P = 0.045) at T1, 45.0 (5.5) mmHg and 49.4 (4.6) mmHg (P < 0.001) at T2, and 47.9 (5.1) mmHg and 52.9 (4.6) mmHg (P < 0.001) at T3, respectively. The median ([IQR] [range]) PaO2 in the high-flow and mask groups was 404.5 (329.1-458.1 [159.8-552.9]) mmHg and 358.9 (274.0-413.3 [129.0-539.1]) mmHg (P = 0.007) at T1, 343.0 (251.6-428.7 [73.9-522.1]) mmHg and 258.3 (162.5-347.5 [56.0-481.0]) mmHg (P < 0.001) at T2, and 333.5 (229.9-411.4 [60.5-492.4]) mmHg and 149.8 (87.0-246.6 [51.2-447.5]) mmHg (P < 0.001) at T3, respectively. The CSA in the high-flow and mask groups was 371.9 (287.4-557.9 [129.0-991.2]) mm2 and 386.8 (292.0-537.3 [88.3-1651.7]) mm2 at T1 (P = 0.920) and 452.6 (343.7-618.4 [161.6-988.1]) mm2 and 385.6 (306.3-562.0 [105.5-922.9]) mm2 at T3 (P = 0.173), respectively. The number (proportion) of complications in the high-flow and mask groups is shown below: hypoxemia: 1 (1.7%) vs. 9 (15.8%, P = 0.019); reflux: 0 (0%) vs. 0 (0%); nasopharyngeal bleeding: 1 (1.7%) vs. 0 (0%, P = 1.000); pulmonary infection: 4 (6.9%) vs. 3 (5.3%, P = 1.000); PONV: 4 (6.9%) vs. 4 (7.0%, P = 1.000), and nasopharyngeal pain: 0 (0%) vs. 0 (0%).

CONCLUSIONS

Compared to facemasks, pre-oxygenation with high-flow oxygen through NPA offers improved carbon dioxide clearance and enhanced oxygenation prior to tracheal intubation in patients undergoing emergency surgery, while the risk of gastric inflation had not been ruled out.

TRIAL REGISTRATION

This trial was registered prospectively at the Chinese Clinical Research Registry on 26/4/2022 (Registration number: ChiCTR2200059192).

Severe Community-Acquired Pneumonia: Noninvasive Mechanical Ventilation, Intubation, and HFNT

Severe acute respiratory failure (ARF) is a major issue in patients with severe community-acquired pneumonia (CAP). Standard oxygen therapy is the first-line therapy for ARF in the less severe cases. However, respiratory supports may be delivered in more severe clinical condition. In cases with life-threatening ARF, invasive mechanical ventilation (IMV) will be required. Noninvasive strategies such as high-flow nasal therapy (HFNT) or noninvasive ventilation (NIV) by either face mask or helmet might cover the gap between standard oxygen and IMV. The objective of all the supporting measures for ARF is to gain time for the antimicrobial treatment to cure the pneumonia. There is uncertainty regarding which patients with severe CAP are most likely to benefit from each noninvasive support strategy. HFNT may be the first-line approach in the majority of patients. While NIV may be relatively contraindicated in patients with excessive secretions, facial hair/structure resulting in air leaks or poor compliance, NIV may be preferable in those with increased work of breathing, respiratory muscle fatigue, and congestive heart failure, in which the positive pressure of NIV may positively impact hemodynamics. A trial of NIV might be considered for select patients with hypoxemic ARF if there are no contraindications, with close monitoring by an experienced clinical team who can intubate patients promptly if they deteriorate. In such cases, individual clinician judgement is key to choose NIV, interface, and settings. Due to the paucity of studies addressing IMV in this population, the protective mechanical ventilation strategies recommended by guidelines for acute respiratory distress syndrome can be reasonably applied in patients with severe CAP.

High-flow nasal oxygenation versus face mask oxygenation for preoxygenation in patients undergoing double-lumen endobronchial intubation: protocol of a randomised controlled trial

INTRODUCTION

With the growing emphasis on swift recovery, minimally invasive thoracic surgery has advanced significantly. Video-assisted thoracoscopic surgery (VATS) has seen rapid development, and the double-lumen tube (DLT) remains the most dependable method for tracheal intubation in VATS. However, hypoxaemia during DLT intubation poses a threat to the perioperative safety of thoracic surgery patients. Recently, transnasal high-flow nasal oxygen (HFNO) has shown promise in anaesthesia, particularly in handling short-duration hypoxic airway emergencies. Yet, its application in the perioperative period for patients undergoing pulmonary surgery with compromised cardiopulmonary function lacks evidence, and there are limited reliable clinical data.

METHODS AND ANALYSIS

A prospective, randomised, controlled, single-blind design will be employed in this study. 112 patients aged 18-60 years undergoing elective VATS-assisted pulmonary surgery will be enrolled and randomly divided into two groups: the nasal high-flow oxygen group (H group) and the traditional mask transnasal oxygen group (M group) in a 1:1 ratio. HFNO will be used during DLT intubation for the prevention of asphyxia in group H, while conventional intubation procedures will be followed by group M. Comparison will be made between the two groups in terms of minimum oxygen saturation during intubation, hypoxaemia incidence during intubation, perioperative complications and postoperative hospital days.

ETHICS AND DISSEMINATION

Approval for this study has been granted by the local ethics committee at Shenzhen Second People's Hospital. The trial results will be disseminated through peer-reviewed journals and scientific conferences.

TRIAL REGISTRATION NUMBER

NCT05666908.

Optimizing nonintubated laryngeal microsurgery: The effectiveness and safety of superior laryngeal nerve block with high-flow nasal oxygen-A prospective cohort study

BACKGROUND

Laryngeal microsurgery (LMS) typically requires intubated general anesthesia (ITGA). Although nonintubated general anesthesia (NIGA) with high-flow nasal oxygen (HFNO) can be applied with LMS, a muscle relaxant is required, which can cause apnea and hypercapnia. This study evaluated the effectiveness of a superior laryngeal nerve block (SLNB) in improving safety during LMS.

METHODS

This prospective cohort study enrolled a cumulative total of 61 adult patients received LMS under intravenous general anesthesia and allocated to three groups: ITGA group (n = 18), which patients performed intubation; neuromuscular blocking (NMB) group (n = 21), which patients administrated muscle relaxant without intubation and superior laryngeal nerve block (NB) group (n = 22), which patients performed SLNB without intubation or muscle relaxant.

RESULTS

The average (SD) values of PaCO 2 after surgery in ITGA, NMB, and NB group were 50.8 (7.5), 97.5 (24.9), and 54.8 (8.8) mmHg, respectively. The mean postoperative pH values were 7.33 (0.04), 7.14 (0.07), and 7.33 (0.04), respectively. The results were all p < 0.001, and the average pH value of the NMB group was lower than that of the ITGA and NB groups. During the LMS, the mean heart rate (HR) (93.9 [18.1] bpm) and noninvasive blood pressure systolic (NBPs) (143.5 [28.2] mmHg) in the NMB group were higher than those in the ITGA group (HR = 77.4 [13.5] bpm and NBPs = 132.7 [20.8] mmHg) and NB group (HR = 82.3 [17.4] bpm and NBPs = 120.9 [25.0] mmHg). The results of p value by HR and NBPs are p < 0.001. The PaCO 2 and pH values are similar between ITGA group and NB group.

CONCLUSION

Our approach of using HFNO with SLNB was successful for performing nonintubated LMS, enabling the patients to maintain spontaneous breathing and effectively eliminate CO 2 . This approach reduces the risks of hypercapnia and acidosis even when the duration of LMS exceeds 30 minutes.

The Predictive Validity of the Berlin Definition of Acute Respiratory Distress Syndrome for Patients With COVID-19-Related Respiratory Failure Treated With High-Flow Nasal Oxygen: A Multicenter, Prospective Cohort Study

OBJECTIVES

The Berlin definition of acute respiratory distress syndrome (ARDS) was constructed for patients receiving invasive mechanical ventilation (IMV) with consideration given to issues related to reliability, feasibility, and validity. Notwithstanding, patients with acute respiratory failure (ARF) may be treated with high-flow nasal oxygen (HFNO) and may not fall within the scope of the original definition. We aimed to evaluate the predictive validity of the Berlin definition in HFNO-treated patients with COVID-19-related respiratory failure who otherwise met ARDS criteria.

DESIGN

Multicenter, prospective cohort study.

SETTING

Five ICUs of five centers in Argentina from March 2020 to September 2021.

PATIENTS

We consecutively included HFNO-treated patients older than 18 years with confirmed COVID-19-related ARF, a Pa o2 /F io2 of less than 300 mm Hg, bilateral infiltrates on imaging, and worsening respiratory symptoms for less than 1 week.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We evaluated the predictive validity of mortality at day 28 using the area under the receiver operating characteristics curve (AUC), compared the predictive validity across subgroups, and characterized relevant clinical outcomes. We screened 1,231 patients and included 696 ARDS patients [30 (4%) mild, 380 (55%) moderate, and 286 (41%) severe]. For the study cohort, the AUC for mortality at day 28 was 0.606 (95% CI, 0.561-0.651) with the AUC for subgroups being similar to that of the overall cohort. Two hundred fifty-six patients (37%) received IMV. By day 28, 142 patients (21%) had died, of whom 81 (57%) had severe ARDS. Mortality occurred primarily in patients who were transitioned to IMV.

CONCLUSIONS

The predictive validity of the Berlin ARDS definition was similar for HFNO-treated patients as compared with the original population of invasively ventilated patients. Our findings support the extension of the Berlin definition to HFNO-treated patients with ARDS.

Physiological effects of high-flow nasal cannula oxygen therapy after extubation: a randomized crossover study

BACKGROUND

Prophylactic high-flow nasal cannula (HFNC) oxygen therapy can decrease the risk of extubation failure. It is frequently used in the postextubation phase alone or in combination with noninvasive ventilation. However, its physiological effects in this setting have not been thoroughly investigated. The aim of this study was to determine comprehensively the effects of HFNC applied after extubation on respiratory effort, diaphragm activity, gas exchange, ventilation distribution, and cardiovascular biomarkers.

METHODS

This was a prospective randomized crossover physiological study in critically ill patients comparing 1 h of HFNC versus 1 h of standard oxygen after extubation. The main inclusion criteria were mechanical ventilation for at least 48 h due to acute respiratory failure, and extubation after a successful spontaneous breathing trial (SBT). We measured respiratory effort through esophageal/transdiaphragmatic pressures, and diaphragm electrical activity (ΔEAdi). Lung volumes and ventilation distribution were estimated by electrical impedance tomography. Arterial and central venous blood gases were analyzed, as well as cardiac stress biomarkers.

RESULTS

We enrolled 22 patients (age 59 ± 17 years; 9 women) who had been intubated for 8 ± 6 days before extubation. Respiratory effort was significantly lower with HFNC than with standard oxygen therapy, as evidenced by esophageal pressure swings (5.3 [4.2-7.1] vs. 7.2 [5.6-10.3] cmH2O; p < 0.001), pressure-time product (85 [67-140] vs. 156 [114-238] cmH2O*s/min; p < 0.001) and ΔEAdi (10 [7-13] vs. 14 [9-16] µV; p = 0.022). In addition, HFNC induced increases in end-expiratory lung volume and PaO2/FiO2 ratio, decreases in respiratory rate and ventilatory ratio, while no changes were observed in systemic hemodynamics, Troponin T, or in amino-terminal pro-B-type natriuretic peptide.

CONCLUSIONS

Prophylactic application of HFNC after extubation provides substantial respiratory support and unloads respiratory muscles. Trial registration January 15, 2021. NCT04711759.

Effect of trans-nasal humidified rapid insufflation ventilatory exchange on reflux and microaspiration in patients undergoing laparoscopic cholecystectomy during induction of general anesthesia: a randomized controlled trial

Background

Reflux aspiration is a rare but serious complication during induction of anesthesia. The primary aim of this study is to compare the incidence of reflux and microaspiration in patients undergoing laparoscopic cholecystectomy during induction of general anesthesia using either a facemask or trans-nasal humidified rapid insufflation ventilatory exchange.

Methods

We conducted a single-center, randomized, controlled trial. Thirty patients were allocated to either a facemask or a trans-nasal humidified rapid insufflation ventilatory exchange (THRIVE) group. Pre-oxygenation for 5 min with a facemask or THRIVE, positive pressure ventilation for 2 min or THRIVE for 2 min after anesthesia induction was followed. Before endotracheal intubation, the secretion above and below the glottis was collected to measure pepsin content and analyze blood gas. The ELISA assay for supra- and subglottic human pepsin content was used to detect the presence of reflux and microaspiration. The primary outcome was the incidence of reflux and microaspiration. Secondary outcomes were apnea time, PaO2 before tracheal intubation, and the end-expiratory carbon dioxide partial pressure.

Results

Patients in the THRIVE group had a significantly longer apnea time (379.55 ± 94.12 s) compared to patients in the facemask group (172.96 ± 58.87 s; p < 0.001). There were no differences observed in PaO2 between the groups. A significant difference in gastric insufflation, reflux, and microaspiration was observed between the groups. Gastric insufflation was 6.9% in the THRIVE group vs. 28.57% kPa in the facemask group (p = 0.041); reflux was 10.34% in the THRIVE group vs. 32.14% kPa in the facemask group (p = 0.044); and microaspiration was 0% in the THRIVE group vs. 17.86% kPa in the facemask group (p = 0.023).

Conclusion

The application of THRIVE during induction of general anesthesia reduced the incidence of reflux and microaspiration while ensuring oxygenation and prolonged apnea time in laparoscopic cholecystectomy patients. THRIVE may be an optimal way to administer oxygen during the induction of general anesthesia in laparoscopic cholecystectomy patients.

Clinical trial registration

Chinese Clinical Trial Registry, No: ChiCTR2100054086, https://www.chictr.org.cn/indexEN.html.

Extubation to High-Flow Nasal Cannula in Infants Following Cardiac Surgery: A Retrospective Cohort Study

High-flow nasal cannula (HFNC) therapy is commonly used in the pediatric intensive care unit (PICU) for postextubation respiratory support. This hypothesis-generating retrospective cohort study aimed to compare postextubation PICU length of stay in infants extubated to HFNC and low flow oxygen (LF) in PICU following cardiac surgery. Of 136 infants (newborn to 1 year) who were intubated and mechanically ventilated in PICU following cardiac surgery, 72 (53%) were extubated to HFNC and 64 (47%) to LF. Compared with patients extubated to LF, those extubated to HFNC had significantly longer durations of cardiopulmonary bypass (152 vs. 109 minutes; p  = 0.002), aortic cross-clamp (90 vs. 63 minutes; p  = 0.003), and invasive mechanical ventilation (3.2 vs. 1.6 days; p  < 0.001), although demographic and preoperative clinical variables were similar. No significant difference was observed in postextubation PICU length of stay between HFNC and LF groups in unadjusted analysis (3.3 vs. 2.6 days, respectively; p  = 0.19) and after controlling for potential confounding variables (F [1,125] = 0.17, p  = 0.68, R 2  = 0.16). Escalation of therapy was similar between HFNC and LF groups (8.3 vs. 14.1%; p  = 0.41). HFNC was effective as rescue therapy for six patients in the LF group requiring escalation of therapy. Need for reintubation was similar between HFNC and LF groups (8.3 vs. 4.7%; p  = 0.5). Although extubation to HFNC was associated with a trend toward longer postextubation PICU length of stay and was successfully used as rescue therapy for several infants extubated to LF, our results must be interpreted with caution given the limitations of our study.

Ultrasound Assessment of Gastric Volume in Parturients After High-Flow Nasal Oxygen Therapy

BACKGROUND

High-flow nasal oxygen (HFNO) therapy is widely used in critical care obstetrics to improve oxygenation. Much of the benefit of HFNO is linked to the creation of modest levels of positive airway pressure. Pregnant women are generally considered to be at high risk of regurgitation and aspiration. It is unknown whether HFNO may cause gas insufflation into the stomach and further increase this risk. Therefore, this study aimed to systematically evaluate the possible safety effects of HFNO on gastric volume in healthy fasted parturients.

METHODS

Sixty fasted parturients scheduled for elective cesarean delivery were enrolled in an observer-blinded, prospective, interventional study. We used ultrasonography to assess changes of antral cross-sectional area (CSA) and gastric volume before and after a 20-minute treatment with HFNO at a rate of 50 L·min -1 . The primary outcome was the change in gastric volume from before to after HFNO therapy, and the secondary outcome was the distribution of antral grades.

RESULTS

In semirecumbent right lateral position, the antral CSA at baseline and after treatment with HFNO was 3.81 (3.01-4.72) cm 2 and 3.79 (3.03-4.54) cm 2 , respectively. The estimated fluid volume at baseline and after treatment with HFNO was 38.51 (33.39-54.62) mL and 39.71 (32.00-52.82) mL, respectively. All participants had either a grade 0 or grade 1 antrum, and most of them had a grade 0 antrum. There was no significant difference in gastric volume and distribution of antral grades before and after HFNO therapy. Gastric air distension was not shown in any of the parturients either at baseline or after treatment with HFNO.

CONCLUSIONS

Treatment with HFNO for 20 minutes at flow rates up to 50 L·min -1 did not increase gastric volume in term pregnant women breathing spontaneously when evaluated by gastric ultrasonography.

Comparison of the efficacy and comfort of high-flow nasal cannula with different initial flow settings in patients with acute hypoxemic respiratory failure: a systematic review and network meta-analysis

BACKGROUND

High-flow nasal cannula (HFNC) has been proven effective in improving patients with acute hypoxemic respiratory failure (AHRF), but a discussion of its use for initial flow settings still need to be provided. We aimed to compare the effectiveness and comfort evaluation of HFNC with different initial flow settings in patients with AHRF.

METHODS

Studies published by October 10, 2022, were searched exhaustively in PubMed, Embase, Web of Science, Cochrane Library (CENTRAL), and the China National Knowledge Infrastructure (CNKI) database. Network meta-analysis (NMA) was performed with STATA 17.0 and R software (version 4.2.1). A Bayesian framework was applied for this NMA. Comparisons of competing models based on the deviance information criterion (DIC) were used to select the best model for NMA. The primary outcome is the intubation at day 28. Secondary outcomes included short-term and long-term mortality, comfort score, length of ICU or hospital stay, and 24-h PaO₂/FiO₂.

RESULTS

This NMA included 23 randomized controlled trials (RCTs) with 5774 patients. With NIV as the control, the HFNC_high group was significantly associated with lower intubation rates (odds ratio [OR] 0.72 95% credible interval [CrI] 0.56 to 0.93; moderate quality evidence) and short-term mortality (OR 0.81 95% CrI 0.69 to 0.96; moderate quality evidence). Using HFNC_Moderate (Mod) group (mean difference [MD] - 1.98 95% CrI -3.98 to 0.01; very low quality evidence) as a comparator, the HFNC_Low group had a slight advantage in comfort scores but no statistically significant difference. Of all possible interventions, the HFNC_High group had the highest probability of being the best in reducing intubation rates (73.04%), short-term (82.74%) and long-term mortality (67.08%). While surface under the cumulative ranking curve value (SUCRA) indicated that the HFNC_Low group had the highest probability of being the best in terms of comfort scores.

CONCLUSIONS

The high initial flow settings (50-60 L/min) performed better in decreasing the occurrence of intubation and mortality, albeit with poor comfort scores. Treatment of HFNC for AHRF patients ought to be initiated from moderate flow rates (30-40 L/min), and individualized flow settings can make HFNC more sensible in clinical practice.

Heated humidified high flow nasal cannula therapy in children with obstructive sleep apnea: A randomized cross-over trial

OBJECTIVE/BACKGROUND

Moderate-to-severe obstructive sleep apnea (OSA) is highly prevalent in children with obesity and/or underlying medical complexity. The first line of therapy, adenotonsillectomy (AT), does not cure OSA in more than 50% of these children. Consequently, continuous positive airway pressure (CPAP) is the main therapeutic option but adherence is often poor. A potential alternative which may be associated with greater adherence is heated high-flow nasal cannula (HFNC) therapy; however, its efficacy in children with OSA has not been systematically investigated. The study aimed to compare the efficacy of HFNC with CPAP to treat moderate-to-severe OSA with the primary outcome measuring the change from baseline in the mean obstructive apnea/hypopnea index (OAHI).

PARTICIPANTS/METHODS

This was a single-blinded randomized, two period crossover trial conducted from March 2019 to December 2021 at a Canadian pediatric quaternary care hospital. Children aged 2-18 years with obesity and medical complexity diagnosed with moderate-to-severe OSA via overnight polysomnography and recommended CPAP therapy were included in the study. Following diagnostic polysomnography, each participant completed two further sleep studies; a HFNC titration study and a CPAP titration study (9 received HFNC first, and 9 received CPAP first) in a random 1:1 allocation order.

RESULTS

Eighteen participants with a mean ± SD age of 11.9 ± 3.8 years and OAHI 23.1 ± 21.7 events/hour completed the study. The mean [95% CI] reductions in OAHI (-19.8[-29.2, -10.5] vs. -18.8 [-28.2, -9.4] events/hour, p = 0.9), nadir oxygen saturation (7.1[2.2, 11.9] vs. 8.4[3.5, 13.2], p = 0.8), oxygen desaturation index (-11.6[-21.0, -2.3] vs. -16.0[-25.3, -6.6], p = 0.5) and sleep efficiency (3.5[-4.8, 11.8] vs. 9.2[0.9, 15.5], p = 0.2) with HFNC and CPAP therapy were comparable between conditions.

CONCLUSION

HFNC and CPAP therapy yield similar reductions in polysomnography quantified measures of OSA severity among children with obesity and medical complexities.

TRIAL REGISTRATION

NCT05354401 ClinicalTrials.gov.

Home High-Flow Therapy in Patients with Chronic Respiratory Diseases: Physiological Rationale and Clinical Results

High-flow therapy (HFT) is the administration of gas flows above 15 L/min. It is a non-invasive respiratory support that delivers heated (up to 38 °C), humidified (100% Relative Humidity, RH; 44 mg H2O/L Absolute Humidity, AH), oxygen-enriched air when necessary, through a nasal cannula or a tracheostomy interface. Over the last few years, the use of HFT in critically ill hypoxemic adults has increased. Although the clinical benefit of home high-flow therapy (HHFT) remains unclear, some research findings would support the use of HHFT in chronic respiratory diseases. The aim of this review is to describe the HFT physiological principles and summarize the published clinical findings. Finally, we will discuss the differences between hospital and home implementation, as well as the various devices available for HHFT application.

The efficacy of high-flow nasal cannula (HFNC) versus non-invasive ventilation (NIV) in patients at high risk of extubation failure: a systematic review and meta-analysis

BACKGROUND

Studies suggest that high-flow nasal cannula (HFNC) and non-invasive ventilation (NIV) can prevent reintubation in critically ill patients with a low risk of extubation failure. However, the safety and effectiveness in patients at high risk of extubation failure are still debated. Therefore, we conducted a systematic review and meta-analysis to compare the efficacies of HFNC and NIV in high-risk patients.

METHODS

We searched eight databases (MEDLINE, Cochrane Library, EMBASE, CINAHL Complete, Web of Science, China National Knowledge Infrastructure, Wan-Fang Database, and Chinese Biological Medical Database) with reintubation as a primary outcome measure. The secondary outcomes included mortality, intensive care unit (ICU) length of stay (LOS), incidence of adverse events, and respiratory function indices. Statistical data analysis was performed using RevMan software.

RESULTS

Thirteen randomized clinical trials (RCTs) with 1457 patients were included. The HFNC and NIV groups showed no differences in reintubation (RR 1.10, 95% CI 0.87-1.40, I² = 0%, P = 0.42), mortality (RR 1.09, 95% CI 0.82-1.46, I² = 0%, P = 0.54), and respiratory function indices (partial pressure of carbon dioxide [PaCO₂]: MD - 1.31, 95% CI - 2.76-0.13, I² = 81%, P = 0.07; oxygenation index [P/F]: MD - 2.18, 95% CI - 8.49-4.13, I² = 57%, P = 0.50; respiratory rate [Rr]: MD - 0.50, 95% CI - 1.88-0.88, I² = 80%, P = 0.47). However, HFNC reduced adverse events (abdominal distension: RR 0.09, 95% CI 0.04-0.24, I² = 0%, P < 0.01; aspiration: RR 0.30, 95% CI 0.09-1.07, I² = 0%, P = 0.06; facial injury: RR 0.27, 95% CI 0.09-0.88, I² = 0%, P = 0.03; delirium: RR 0.30, 95%CI 0.07-1.39, I² = 0%, P = 0.12; pulmonary complications: RR 0.67, 95% CI 0.46-0.99, I² = 0%, P = 0.05; intolerance: RR 0.22, 95% CI 0.08-0.57, I² = 0%, P < 0.01) and may have shortened LOS (MD - 1.03, 95% CI - 1.86-- 0.20, I² = 93%, P = 0.02). Subgroup analysis by language, extubation method, NIV parameter settings, and HFNC flow rate revealed higher heterogeneity in LOS, PaCO₂, and Rr.

CONCLUSIONS

In adult patients at a high risk of extubation failure, HFNC reduced the incidence of adverse events but did not affect reintubation and mortality. Consequently, whether or not HFNC can reduce LOS and improve respiratory function remains inconclusive.

Postoperative Respiratory Failure and Advanced Ventilator Settings

Postoperative respiratory failure has a multifactorial etiology, of which atelectasis is the most common mechanism. Its injurious effects are magnified by surgical inflammation, high driving pressures, and postoperative pain. Chest physiotherapy and noninvasive ventilation are good options to prevent progression of respiratory failure. Acute respiratory disease syndrome is a late and severe finding, which is associated with high morbidity and mortality. If present, proning is a safe, effective, and underutilized therapy. Extracorporeal membrane oxygenation is an option only when traditional supportive measures have failed.

The effects of flow settings during high-flow nasal cannula support for adult subjects: a systematic review

BACKGROUND

During high-flow nasal cannula (HFNC) therapy, flow plays a crucial role in the physiological effects. However, there is no consensus on the initial flow settings and subsequent titration. Thus, we aimed to systematically synthesize the effects of flows during HFNC treatment.

METHODS

In this systematic review, two investigators independently searched PubMed, Embase, Web of Science, Scopus, and Cochrane for in vitro and in vivo studies investigating the effects of flows in HFNC treatment published in English before July 10, 2022. We excluded studies that investigated the pediatric population (< 18 years) or used only one flow. Two investigators independently extracted the data and assessed the risk of bias. The study protocol was prospectively registered with PROSPERO, CRD42022345419.

RESULTS

In total, 32,543 studies were identified, and 44 were included. In vitro studies evaluated the effects of flow settings on the fraction of inspired oxygen (F_IO₂), positive end-expiratory pressure, and carbon dioxide (CO₂) washout. These effects are flow-dependent and are maximized when the flow exceeds the patient peak inspiratory flow, which varies between patients and disease conditions. In vivo studies report that higher flows result in improved oxygenation and dead space washout and can reduce work of breathing. Higher flows also lead to alveolar overdistention in non-dependent lung regions and patient discomfort. The impact of flows on different patients is largely heterogeneous.

INTERPRETATION

Individualizing flow settings during HFNC treatment is necessary, and titrating flow based on clinical findings like oxygenation, respiratory rates, ROX index, and patient comfort is a pragmatic way forward.

Newly Proposed Diagnostic Criteria for Acute Respiratory Distress Syndrome: Does Inclusion of High Flow Nasal Cannula Solve the Problem?

Acute respiratory distress syndrome (ARDS) is a common life-threatening clinical syndrome which accounts for 10% of intensive care unit admissions. Since the Berlin definition was developed, the clinical diagnosis and therapy have changed dramatically by adding a minimum positive end-expiratory pressure (PEEP) to the assessment of hypoxemia compared to the American-European Consensus Conference (AECC) definition in 1994. High-flow nasal cannulas (HFNC) have become widely used as an effective respiratory support for hypoxemia to the extent that their use was proposed in the expansion of the ARDS criteria. However, there would be problems if the diagnosis of a specific disease or clinical syndrome occurred, based on therapeutic strategies.

High-Flow Versus VenturiMask Oxygen Therapy to Prevent Reintubation in Hypoxemic Patients after Extubation: A Multicenter Randomized Clinical Trial

Rationale: When compared with VenturiMask after extubation, high-flow nasal oxygen provides physiological advantages. Objectives: To establish whether high-flow oxygen prevents endotracheal reintubation in hypoxemic patients after extubation, compared with VenturiMask. Methods: In this multicenter randomized trial, 494 patients exhibiting Pa_O2:Fi_O2 ratio ⩽ 300 mm Hg after extubation were randomly assigned to receive high-flow or VenturiMask oxygen, with the possibility to apply rescue noninvasive ventilation before reintubation. High-flow use in the VenturiMask group was not permitted. Measurements and Main Results: The primary outcome was the rate of reintubation within 72 hours according to predefined criteria, which were validated a posteriori by an independent adjudication committee. Main secondary outcomes included reintubation rate at 28 days and the need for rescue noninvasive ventilation according to predefined criteria. After intubation criteria validation (n = 492 patients), 32 patients (13%) in the high-flow group and 27 patients (11%) in the VenturiMask group required reintubation at 72 hours (unadjusted odds ratio, 1.26 [95% confidence interval (CI), 0.70-2.26]; P = 0.49). At 28 days, the rate of reintubation was 21% in the high-flow group and 23% in the VenturiMask group (adjusted hazard ratio, 0.89 [95% CI, 0.60-1.31]; P = 0.55). The need for rescue noninvasive ventilation was significantly lower in the high-flow group than in the VenturiMask group: at 72 hours, 8% versus 17% (adjusted hazard ratio, 0.39 [95% CI, 0.22-0.71]; P = 0.002) and at 28 days, 12% versus 21% (adjusted hazard ratio, 0.52 [95% CI, 0.32-0.83]; P = 0.007). Conclusions: Reintubation rate did not significantly differ between patients treated with VenturiMask or high-flow oxygen after extubation. High-flow oxygen yielded less frequent use of rescue noninvasive ventilation. Clinical trial registered with www.clinicaltrials.gov (NCT02107183).

High-flow nasal oxygen for suspension laryngoscopy: a multicenter open-label study

In this study, we aimed to assess the efficacy of high-flow nasal oxygen (HFNO) to maintain blood peripheral oxygen saturation (SpO2) in patients undergoing suspension laryngoscopy under general anesthesia. Adult patients were included in this bicenter study. After face-mask oxygenation, HFNO at a flow rate of 70 L min^-1 and fraction of inspired oxygen 100% was initiated at loss of consciousness. At the end of HFNO, blood gas analysis was performed. Of the 29 included patients, five (17.2%; 95% confidence interval [CI]: 7.6-34.5) presented SpO2 <95% during the first 15 minutes of the procedure and eight patients (27.6%; 95% CI: 14.7-45.7) presented SpO2 <95% throughout the procedure. Six patients (20.7%; 95% CI: 9.8-38.4) required rescue jet ventilation. Median apnea time before SpO2 <95% was 13.5 (interquartile range [IQR]: 10-17.7) minutes. Arterial carbon dioxide tension at the end of the procedure or at the time of study discontinuation was 9.73 (IQR: 8.8-10.9) kPa and was higher than 8 kPa in 88.9% (95% CI: 71.9-96.1) of patients. HFNO was associated with a relatively high incidence of suboptimal oxygen saturation and hypercapnia during suspension laryngoscopy under general anesthesia and may not be considered the reference technique.

Anesthetic management using high-flow nasal cannula therapy during cardiac catheter examination of a neonate with hypoplastic left heart syndrome

Background

Sedation during cardiac catheter examination in neonates with complex congenital heart disease is challenging, as even the slightest change in the circulatory or respiratory status can lead to hemodynamic collapse. Here, we report a case wherein we achieved adequate sedation with a high-flow nasal cannula (HFNC) for catheter examination in a neonate with a congenital cardiac anomaly.

Case presentation

An 11-day-old boy with hypoplastic left heart syndrome was scheduled for a cardiac catheter examination prior to the Norwood procedure. He underwent bilateral pulmonary artery banding (PAB) on day 1 and was receiving dobutamine, milrinone, alprostadil, and dexmedetomidine in addition to air and nitrogen insufflation via HFNC, which was applied following extubation on day 3 and nitrogen therapy on day 6 owing to persistent pulmonary overcirculation symptoms (tachypnea and low arterial blood pressure) despite bilateral PAB. A catheter examination was performed on day 11 with careful monitoring of expired carbon dioxide and observation of chest wall motion. Adequate sedation was provided with supplemental midazolam and fentanyl along with HFNC without tracheal intubation.

Conclusions

The findings from this case suggest that HFNC is a safe and effective tool for oxygenation during cardiac catheter examination under sedation in neonates.

Acute respiratory distress syndrome in adults: diagnosis, outcomes, long-term sequelae, and management

Acute respiratory distress syndrome (ARDS) is characterised by acute hypoxaemic respiratory failure with bilateral infiltrates on chest imaging, which is not fully explained by cardiac failure or fluid overload. ARDS is defined by the Berlin criteria. In this Series paper the diagnosis, management, outcomes, and long-term sequelae of ARDS are reviewed. Potential limitations of the ARDS definition and evidence that could inform future revisions are considered. Guideline recommendations, evidence, and uncertainties in relation to ARDS management are discussed. The future of ARDS strives towards a precision medicine approach, and the framework of treatable traits in ARDS diagnosis and management is explored.

Changes in lung volume estimated by electrical impedance tomography during apnea and high-flow nasal oxygenation: A single-center randomized controlled trial

Background

Previous studies concerning humidified, heated high-flow nasal oxygen delivered in spontaneously breathing patients postulated an increase in functional residual capacity as one of its physiological effects. It is unclear wheter this is also true for patients under general anesthesia.

Methodology

The sincle-center noninferiority trial was registered at ClinicalTrials.gov (NCT NCT03478774). This secondary outcome analysis shows estimated differences in lung volume changes using electrical impedance tomography between different flow rates of 100% oxygen in apneic, anesthetized and paralyzed adults prior to intubation. One hundred and twenty five patients were randomized to five groups with different flow rates of 100% oxygen: i) minimal-flow: 0.25 l.min-1 via endotracheal tube; ii) low-flow: 2 l.min-1 + continuous jaw thrust; iii) medium-flow: 10 l.min-1 + continuous jaw thrust; iv) high-flow: 70l.min-1 + continuous jaw thrust; and v) control: 70 l.min-1 + continuous video-laryngoscopy. After standardized anesthesia induction with non-depolarizing neuromuscular blockade, the 15-minute apnea period and oxygen delivery was started according to the randomized flow rate. Continuous electrical impedance tomography measurements were performed during the 15-minute apnea period. Total change in lung impedance (an estimate of changes in lung volume) over the 15-minute apnea period and times to 25%, 50% and 75% of total impedance change were calculated.

Results

One hundred and twenty five patients completed the original study. Six patients did not complete the 15-minute apnea period. Due to maloperation, malfunction and artefacts additional 54 measurements had to be excluded, resulting in 65 patients included into this secondary outcome analysis. We found no differences between groups with respect to decrease in lung impedance or curve progression over the observation period.

Conclusions

Different flow rates of humidified 100% oxygen during apnea result in comparable decreases in lung volumes. The demonstrated increase in functional residual capacity during spontaneous breathing with high-flow nasal oxygenation could not be replicated during apnea under general anesthesia with neuromuscular blockade.

Peri-intubation oxygenation for Caesarean delivery: is there an optimal technique?

Peri-intubation oxygen administration to the pregnant patient during induction of general anaesthesia is critical to avoiding hypoxaemia and harm to the mother and fetus. Recent modelling comparing low-flow with high-flow nasal oxygen in simulated term pregnant women of varying body habitus, taken together with previous work, suggests that face mask preoxygenation with the use of low-flow or high-flow nasal oxygen during the period of apnoea prolongs the safe apnoea period, with the benefit varying by body habitus. Low-flow compared with high-flow nasal oxygen may be easier to combine with face mask preoxygenation and is readily available in all operating theatres, although future improvements in high-flow nasal oxygen delivery systems may improve ease of use for this indication.

High flow nasal cannula for patients undergoing bronchoscopy and gastrointestinal endoscopy: A systematic review and meta-analysis

Background

High flow nasal cannula is gaining increasingly used in patients undergoing endoscopic procedures. We undertook this systematic review and meta-analysis to determine whether high flow nasal cannula (HFNC) could effectively minimize the risk of hypoxemia as compared with conventional oxygen therapy (COT).

Methods

We performed a comprehensive search of Pubmed, Cochrane Central Register of Controlled Trials (CENTRAL), Embase, and Web of Science. Studies involving the application of HFNC during endoscopic procedures were identified.

Results

We included 15 randomized controlled trials (7 bronchoscopy, 8 gastrointestinal endoscopy). Patients receiving HFNC during endoscopic procedures had a significantly lower risk of hypoxemia (defined as SpO2 &lt; 90%) versus COT group (risk ratio = 0.32; 95%CI (0.22–0.47), 13 studies, 4,093 patients, moderate-quality evidence, I2 = 48.82%, P &lt; 0.001). The lowest SpO2 was significantly higher in HFNC group (mean difference = 4.41; 95%CI (2.95–5.86), 9 studies, 1,449 patients, moderate-quality evidence, I2 = 81.17%, P &lt; 0.001) than those receiving COT. No significant difference was detected between groups in end-procedure partial pressure of CO2 (standard mean difference  =  −0.18; 95%CI (−0.52–0.15), 5 studies, 238 patients, moderate-quality evidence, I2 = 42.25%, P = 0.29). Patients receiving HFNC were associated a lower need for airway intervention (risk ratio = 0.45; 95%CI (0.24–0.84), 8 studies, 2,872 patients, moderate-quality evidence, I2 = 85.97%, P = 0.01) and less procedure interruption (risk ratio = 0.36; 95%CI (0.26–0.51), 6 studies, 1,562 patients, moderate-quality evidence, I2 = 0.00%, P &lt; 0.001). The overall intubation rate after endoscopy was 0.20% in both group, with no difference detected (risk ratio = 1.00; 95%CI (0.30–3.35), 7 studies, 2,943 patients, low-quality evidence, I2 = 0.00%, P = 1.00).

Conclusion

This systematic review and meta-analysis found moderate to low evidence that the application of HFNC was associated with improved oxygenation, decreased need for airway intervention, and reduced procedure interruption in patients undergoing endoscopic procedures. Future larger sample and high-quality studies are warranted to confirm our result and further investigate the effectiveness of HFNC in patients at risk.

Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier: CRD42022298032.

Impact of High-Flow Nasal Cannula Oxygenation on the Prevention of Hypoxia During Endoscopic Retrograde Cholangiopancreatography in Elderly Patients: A Randomized Clinical Trial

BACKGROUND

Hypoxia is the most frequently occurring adverse effect during endoscopic retrograde cholangiopancreatography (ERCP) under sedation; thus, oxygen must be properly supplied to prevent a reduction of oxygen saturation. In this study, we intend to verify the preventive effect for hypoxia during ERCP, using a high-flow nasal cannula (HFNC), in elderly patients.

METHODS

As a multicenter prospective randomized trial, patients who underwent ERCP with propofol-based sedation were randomly assigned into two groups: Patients in the HFNC group were supplied with oxygen via an HFNC, and those in the standard nasal cannula group were supplied with oxygen via a low-flow nasal cannula. The co-primary end points were the lowest oxygen saturation rate and hypoxia during the overall procedure.

RESULTS

A total of 187 patients (HFNC group: 95; standard nasal cannula group: 92) were included in the analysis. Unexpected hypoxia events were more frequently observed among patients in the standard nasal cannula group than among patients in the HFNC group (13% vs. 4%, odds ratio 3.41, 95% confidence interval 1.06-11.00, p = 0.031). The mean of the lowest oxygen saturation rate during ERCP was significantly lower in the standard nasal cannula group than in the HFNC group (95% vs. 97%, p = 0.002).

CONCLUSION

Oxygen supplementation with an HFNC can prevent oxygen desaturation and hypoxia events in patients undergoing ERCP under sedation. Trial registration Clinical Research Information Service (CRIS; KCT0004960).

Comparison of Transnasal Humidified Rapid-Insufflation Ventilatory Exchange and Facemasks in Preoxygenation: A Systematic Review and Meta-Analysis

Background

Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) has received increasing attention and application as an effective noninvasive mode of ventilation in the treatment of clinical anesthesia and critically ill patients. The conclusions reached in clinical studies of THRIVE and facemask oxygenation are still controversial, and the main objective of this systematic review is to determine the advantages of THRIVE over facemask oxygenation in intensive care units, respiratory medicine, and perioperative preoxygenation.

Methods

PubMed, Embase, Web of Science, and Cochrane Library have search restrictions. The search library was full of English language articles from the first publication to 15 July 2021. Eligible randomized controlled study designs were included. 245 records were screened, and 5 studies met the inclusion criteria, enrolling a total of 235 patients.

Results

Studying the THRIVE group compared to the facemask group, three studies analyzing intubation time showed that there is no difference in the effect of THRIVE and facemasks (MD -1.22, 95% CI -7.23 to 4.78, and P = 0.69 > 0.05). Three studies analyzing apnea showed that there was no difference between the two groups (SMD 1, 95% CI -0.76 to 2.76, and P = 0.27 > 0.05). Three studies analyzing PaO₂ after preoxygenation showed that THRIVE is more effective than facemasks (MD 72.58, 95% CI 31.25 to 113.90, Z = 3.44, and P < 0.001). Two studies analyzing oxygen saturation SpO₂ after successful intubation showed that there was no difference in the effectiveness (MD 0.09, 95% CI -1.03 to 1.22, and P = 0.87 > 0.05). Two studies analyzing PCO₂ after complete paralysis or intubation preoxygenation showed that there was no difference between the two groups (MD 2.76, 95% CI -1.74 to 7.26, and P = 0.23 > 0.05).

Conclusions

THRIVE does not have a greater advantage over a facemask in improving apnea time, oxygenation time, PCO₂, and SpO₂, but it has an advantage in improving arterial partial pressure of oxygen (PaO₂) after preoxygenation, which can improve PaO₂ well. This trial is registered with the protocol registration number CRD42021268143.

Nasal pillow noninvasive ventilation versus high-flow nasal therapy after extubation in surgical intensive care patients: A propensity-matched cohort study

Objective

To evaluate the tolerability and efficacy of nasal pillow-noninvasive ventilation (NP-NIV) compared with high-flow nasal therapy (HFNT) in postsurgical patients.

Methods

This propensity score-matched retrospective study enrolled postoperative patients that received NP-NIV (NP-NIV group) or HFNT (HFNT group) in the intensive care unit. Data were collected from their medical records and the tolerability and respiratory status before and after extubation were compared between the two groups.

Results

The study enrolled 83 patients in the NP-NIV group and 27 patients in the HFNT group. After propensity score matching, there were 19 patients in each group. After matching, there were no significant differences in the baseline demographic and clinical characteristics before extubation. The tolerability was similar in both groups. When the NP-NIV group was compared with the HFNT group, the respiratory rate was significantly lower (median 16 [interquartile range, 14–17] versus median 19 [interquartile range, 18–26], respectively) and the partial pressure of arterial oxygen/fraction of inspired oxygen ratio was significantly higher (median 205 [174–256] versus median 155 [130–192], respectively) at 1 h after extubation.

Conclusion

NP-NIV was equally well tolerated and provided better respiratory support than HFNT in postsurgical patients.

High Flow Nasal Cannula compared to Continuous Positive Airway Pressure: a bench and physiological study

High-flow nasal cannula (HFNC) is extensively used for acute respiratory failure. However, questions remain regarding its physiological effects. We explored 1) whether HFNC produced similar effects to continuous positive airway pressure (CPAP); 2) possible explanations of respiratory rate changes; 3) the effects of mouth opening. Two studies were conducted: a bench study using a manikin's head with lungs connected to a breathing simulator while delivering HFNC flow rates from 0 to 60L/min; a physiological cross-over study in 10 healthy volunteers receiving HFNC (20 to 60L/min) with the mouth open or closed and CPAP 4cmH2O delivered through face-mask. Nasopharyngeal and esophageal pressures were measured; tidal volume and flow were estimated using calibrated electrical impedance tomography. In the bench study, nasopharyngeal pressure at end-expiration reached 4cmH2O with HFNC at 60L/min, while tidal volume decreased with increasing flow. In volunteers with HFNC at 60L/min, nasopharyngeal pressure reached 6.8cmH2O with mouth closed and 0.8cmH2O with mouth open; p<0.001. When increasing HFNC flow, respiratory rate decreased by lengthening expiratory time, tidal volume did not change, and effort decreased (pressure-time product of the respiratory muscles); at 40L/min, effort was equivalent between CPAP and HFNC40L/min and became lower at 60L/min (p=0.045). During HFNC with mouth closed, and not during CPAP, resistance to breathing was increased, mostly during expiration. In conclusion, mouth closure during HFNC induces a positive nasopharyngeal pressure proportional to flow rate and an increase in expiratory resistance that might explain the prolonged expiration and reduction in respiratory rate and effort, and contribute to physiological benefits.

Management of Respiratory Failure: Ventilator Management 101 and Noninvasive Ventilation

Mechanical ventilation is a lifesaving therapy for critically ill patients with respiratory failure, but like all treatments, it has the potential to cause harm if not administered appropriately. This review aims to give an overview of the basic principles of invasive and noninvasive mechanical ventilation. Topics covered include modes of mechanical ventilation, respiratory mechanics and ventilator waveform interpretation, strategies for initial ventilator settings, indications and contraindications for noninvasive ventilation, and the effect of the ventilator on kidney function.

Effect of respiratory rate and size of cannula on pressure and dead-space clearance during nasal high flow in patients with COPD and acute respiratory failure

Nasal high flow (NHF) is an efficient oxygenation tool for the treatment of respiratory failure. The study investigated the effect of breathing pattern on positive airway pressure and dead-space clearance by NHF. The breathing cycle during NHF was characterized in 26 patients with acute respiratory failure (ARF) and stable COPD and after mechanical ventilation (post-MV) via tracheostomy where also pressure was measured in the trachea. Dead-space clearance was measured in airway models during different breathing patterns. NHF reduced the respiratory rate (RR) and T_I/T_E through prolonging the T_E; the T_I/T_E ranged between ≤0.5 observed in the COPD patients and ∼1.0 in the ARF patients. NHF via a standard medium-sized cannula interface generated a low-level expiratory pressure proportional to NHF rate and breathing flow; the median generated positive end-expiratory pressure was only 1.71 cmH₂O at NHF 45 L/min. The dilution and purging of expired gas from a nasal cavity model were observed to occur at the end of expiration as expiratory flow slowed and the dynamic pressure decreased. The higher RR with shorter end-expiratory period resulted in reduced dead-space clearance by NHF; 20 L/min cleared 43 ± 2 mL at RR 15 min⁻¹ vs. 9 ± 5 mL at RR 45 min⁻¹, P < 0.001, which was increased at higher NHF rate. At lower RR, the clearance was similar between NHF rates 20 and 60 L/min. Higher NHF rates elevate positive airway pressure, and at the increased RR can improve the clearance. This may enhance gas exchange and lead to a reduction in the work of breathing.

NEW & NOTEWORTHY During nasal high flow (NHF) an increased breathing frequency, which is commonly observed in acute respiratory failure, can lead to decreased dead-space clearance. Higher NHF rates increase the clearance and reduce the rebreathing which may eventually lower the respiratory rate and the work of breathing. Monitoring of the respiratory rate could be an important indicator of not only the respiratory function but also the NHF rate selection and the therapy efficacy.

High-flow nasal cannula for reducing hypoxemic events in patients undergoing bronchoscopy: A systematic review and meta-analysis of randomized trials

BACKGROUND

Patients undergoing bronchoscopic procedures may develop hypoxemia and severe complications. High-flow nasal cannula (HFNC) may prevent hypoxemic events during bronchoscopy. We conducted a systematic review of randomized controlled trials (RCTs) to evaluate the effectiveness of HFNC in these patients.

METHODS

We conducted a search in PubMed, Embase, and the Cochrane Library for RCTs published before November 2021. Individual effect sizes were standardized, and a meta-analysis was performed to calculate the pooled effect size using random-effects models. The primary outcome was the incidence of hypoxemic events (oxygen saturation [SpO2] < 90%) during bronchoscopy. Secondary outcomes included the incidence of interrupted bronchoscopy due to desaturation, lowest SpO2 during bronchoscopy, partial pressure of oxygen (PaO2), partial pressure of carbon dioxide (PaCO2), end-tidal CO2 (EtCO2) at the end of bronchoscopy, and the incidence of intubation after the procedure.

RESULTS

Five trials involving 257 patients were reviewed. The incidence of hypoxemic events was lower in the HFNC group than in the conventional oxygen therapy group (risk ratio, 0.25; 95% confidence interval [CI], 0.14-0.42). The lowest SpO2 during the procedure was significantly higher in the HFNC group than in the conventional oxygen therapy group (weighted mean difference [WMD], 7.12; 95% CI, 5.39-8.84). PaO2 at the end of the procedure was significantly higher in the HFNC group than in the conventional oxygen therapy group (WMD, 20.36; 95% CI, 0.30-40.42). The incidence of interrupted bronchoscopy due to desaturation, PaCO2 and EtCO2 at the end of the procedure, and the incidence of intubation after the procedure were not significantly different between groups.

CONCLUSIONS

HFNC may reduce the incidence of hypoxemic events and improve oxygenation in patients undergoing bronchoscopy.

High-flow nasal cannula versus face mask for preoxygenation in obese patients: A randomised controlled trial

BACKGROUND

Preoxygenation efficacy with high-flow nasal cannula (HFNC) in obese patients is not clearly established. The primary aim of this study was to compare heated, humidified, high-flow nasal cannula with face mask for preoxygenation in this population.

METHODS

We conducted a single-centre, randomised, controlled trial. Forty subjects with BMI ≥ 35 kg m^-2 were randomly assigned to receive 5.0 min of preoxygenation with face mask and 7 cm H₂ O of PEEP (PEEP group) or HFNC at 70 L min^-1 (HF group). Following induction, bag-mask ventilation continued until laryngoscopy, whereas HFNC was maintained before and during intubation. The primary outcomes were end-tidal fraction of oxygen (EtO₂ ) at 2.5 and 5.0 min duration of preoxygenation. Secondary outcomes included PaO₂ and PaCO₂ at 2.5 and 5.0 min of preoxygenation and at intubation.

RESULTS

Mean (±SD) EtO₂ was 0.89 (±0.04) versus 0.90 (±0.05) after 2.5 min (95% CI for mean difference -0.02, 0.04) and 0.93 (±0.02) versus 0.91 (±0.02) after 5.0 min of preoxygenation (95% CI for mean difference -0.03, -0.002) in the PEEP (n = 18) and HF group (n = 20), respectively. All subjects reached an EtO₂  ≥ 0.85 at 5.0 min. There were no differences in mean PaO₂ or PaCO₂ during preoxygenation. Subjects in the HF group had a mean (±SD) apnoea time of 199 (±38) s, but no desaturation (SpO₂  < 100%) occurred.

CONCLUSIONS

Face mask with PEEP was superior to HFNC for preoxygenation in obese subjects. HFNC provided adequate preoxygenation quality in all subjects and may be considered as an alternative to face mask in selected patients.

TRIAL REGISTRATION

#ISRCTN37375068 (www.isrctn.com).

Physiological Responses and Perceived Comfort to High Flow Nasal Cannula Therapy in Awake Adults: Effects of Flow Magnitude and Temperature

Clinical use of heated, high flow nasal cannula (HFNC) for non-invasive respiratory support is increasing and may have a therapeutic role in stabilizing the upper airway in obstructive sleep apnea (OSA). However, physiological mechanisms by which HFNC therapy may improve upper-airway function and effects of different temperature modes are unclear. Accordingly, this study aimed to determine effects of incremental flows and temperature modes (heated and non-heated) of HFNC on upper airway muscle activity (genioglossus), pharyngeal airway pressure, breathing parameters and perceived comfort. Six participants (2 females, aged 35±14 years) were studied during wakefulness in supine position and received HFNC at variable flows (0-60 L/min) during heated (37ºC) and non-heated (21ºC) modes. Breathing parameters via calibrated Respitrace inductance bands (chest and abdomen), upper-airway pressures via airway transducers, and genioglossus muscle activity via intra-muscular bipolar fine wire electrodes were measured. Comfort levels during HFNC were quantified using a visual analogue scale. Increasing HFNC flows did not increase genioglossus muscle activation despite increased negative epiglottic pressure swings (p=0.009). HFNC provided ~7cmH₂O positive airway pressure at 60 L/min in non-heated and heated modes. In addition, increasing the magnitude of HFNC flow reduced breathing frequency (p=0.045), increased expiratory time (p=0.040), increased peak inspiratory flow (p=0.002), and increased discomfort (p=0.004). Greater discomfort occurred at higher flows in non-heated versus heated mode (p=0.034). These findings provide novel insight into key physiological changes that occur with HFNC for respiratory support and indicate the primary mechanism for improved upper-airway stability is positive airway pressure, not increased pharyngeal muscle activity.

High flow nasal oxygen during procedural sedation for cardiac implantable electronic device procedures: A randomised controlled trial

BACKGROUND

High flow nasal oxygen may better support the vulnerable respiratory state of patients during procedural sedation.

OBJECTIVE

The objective of this study was to investigate the effects of high flow nasal oxygen in comparison to facemask oxygen on ventilation during cardiac implantable electronic device procedures performed with procedural sedation.

DESIGN

A randomised controlled trial.

SETTING

The study was conducted at one academic hospital in Canada.

PARTICIPANTS

Adults undergoing elective cardiac implantable electronic device procedures with sedation administered by an anaesthesia assistant, supervised by an anaesthesiologist from August 2019 to March 2020.

INTERVENTIONS

Participants were randomised 1 : 1 to facemask (≥ 8 l · min-1) or high flow nasal oxygen (50 l · min-1 and a 50 : 50 oxygen to air ratio).

MAIN OUTCOME MEASURES

The primary outcome was peak transcutaneous carbon dioxide. Outcomes were analysed using Bayesian statistics.

RESULTS

The 129 participants who were randomised and received sedation were included. The difference in peak transcutaneous carbon dioxide was 0.0 kPa (95% CI -0.17 to 0.18). Minor adverse sedation events were 6.4 times more likely to occur in the high flow nasal oxygen group. This estimate is imprecise (95% CI 1.34 to 42.99). The odds ratio for oxygen desaturation for the high flow nasal oxygen group compared with the facemask group was 1.2 (95% CI 0.37 to 3.75). The difference in satisfaction with sedation scores between groups was 0.0 (95% CI -0.33 to 0.23).

CONCLUSIONS

Ventilation, as measured by TcCO2, is highly unlikely to differ by a clinically important amount between high flow nasal oxygen at 50 l min-1 or facemask oxygen at 8 l min-1. Further research with a larger sample size would be required to determine the optimal oxygen:air ratio when using high flow nasal oxygen during cardiac implantable electronic device procedures performed with sedation.

TRIAL REGISTRATION NUMBER

NCT03858257.

Noninvasive Tidal Volume Measurements, Using a Time-of-Flight Camera, Under High-Flow Nasal Cannula-A Physiological Evaluation, in Healthy Volunteers

OBJECTIVES

The mechanisms of high-flow nasal cannula are still debated but may be mediated by the generation of low positive end-expiratory pressure and a washout of the airway dead space. The aims of this study were to assess the effects of high-flow nasal cannula on tidal volume using a noninvasive method using a time-of-flight camera, under various conditions.

DESIGN

A physiologic evaluation in healthy volunteers.

SETTING

An university hospital ICU.

SUBJECTS

Ten healthy volunteers were included in a physiologic study (CamOpt study, ClinicalTrials.gov identifier: NCT04096183).

INTERVENTIONS

All volunteers were submitted to 12 different conditions (i.e., gas flow [baseline = 0; 30-60 L/min]; mouth [open/closed]; respiratory rate [baseline; baseline + 10 breaths/min]). Tidal volume measurements were performed every minute, during a 6-minute recording period. In all combinations, reference respiratory rate was measured by using chronometric evaluation, over a 30-second period (RRREF), and by using the time-of-flight camera (RRTOF).

MEASUREMENTS AND MAIN RESULTS

Tidal volume increased while increasing gas flow whatever the respiratory rate and mouth condition (p < 0.001). Similar results were observed whatever the experimental conditions (p < 0.01), except one (baseline respiratory rate + 10 breaths/min and mouth closed). Tidal volume increased while decreasing respiratory rate (p < 0.001) and mouth closing (p < 0.05). Proportion of tidal volume greater than 10, 15, and 20 mL/kg changed while increasing the flow. RRTOF was in agreement with RRREF (intraclass correlation coefficient, 0.96), with a low mean bias (0.55 breaths/min) and acceptable deviation.

CONCLUSIONS

Time-of-flight enables to detect tidal volume changes under various conditions of high-flow nasal cannula application. Tidal volume increased significantly while increasing gas flow and mouth closing. Such technique might be useful to monitor the risk of patient self-inflicted lung injury or under assistance.

Association between increased nonaerated lung weight and treatment failure in patients with de novo acute respiratory failure: Difference between high-flow nasal oxygen therapy and noninvasive ventilation in a multicentre retrospective study

PURPOSE

To determine the association between lung collapse and treatment failure in high-flow nasal cannula oxygen therapy (HFNC) or noninvasive ventilation (NIV).

METHODS

We performed a quantitative analysis of chest computed tomography in patients with de novo acute respiratory failure who received HFNC (HFNC group) or NIV (NIV group) between January 2012 and December 2017. In the HFNC and NIV group, the nonaerated lung weight were compared between patients in whom respiratory treatment succeeded or failed, respectively. We used logistic regression to examine the association between the nonaerated lung weight and treatment failure.

RESULTS

Treatment failed in 70/118 (59%) patients in the HFNC group and 66/101 (65%) patients in the NIV group. The nonaerated lung weight was significantly greater in unsuccessfully treated patients than in successfully treated patients in the HFNC group (p = 0.005), but not in the NIV group (p = 0.535). Logistic regression revealed that greater nonaerated lung weight was associated with increased risk of HFNC failure (adjusted odds ratio 1.30 per 5% increase, 95% confidence interval 1.09-1.55, p = 0.003) but not of NIV failure.

CONCLUSIONS

Patients with a greater nonaerated lung weight had a higher risk of HFNC failure, but not of NIV failure.

High flow nasal cannula for adult acute hypoxemic respiratory failure in the ED setting: A narrative review

Introduction

High flow nasal cannula (HFNC) is a noninvasive ventilation (NIV) system that has demonstrated promise in the emergency department (ED) setting.

Objective

This narrative review evaluates the utility of HFNC in adult patients with acute hypoxemic respiratory failure in the ED setting.

Discussion

HFNC provides warm (37 °C), humidified (100% relative humidity) oxygen at high flows with a reliable fraction of inspired oxygen (FiO₂). HFNC can improve oxygenation, reduce airway resistance, provide humidified flow that can flush anatomical dead space, and provide a low amount of positive end expiratory pressure. Recent literature has demonstrated efficacy in acute hypoxemic respiratory failure, including pneumonia, acute respiratory distress syndrome (ARDS), coronavirus disease 2019 (COVID-19), interstitial lung disease, immunocompromised states, the peri-intubation state, and palliative care, with reduced need for intubation, length of stay, and mortality in some of these conditions. Individual patient factors play an important role in infection control risks with respect to the use of HFNC in patients with COVID-19. Appropriate personal protective equipment, adherence to hand hygiene, surgical mask placement over the HFNC device, and environmental controls promoting adequate room ventilation are the foundation for protecting healthcare personnel. Frequent reassessment of the patient placed on HFNC is necessary; those with severe end organ dysfunction, thoracoabdominal asynchrony, significantly increased respiratory rate, poor oxygenation despite HFNC, and tachycardia are at increased risk of HFNC failure and need for further intervention.

Conclusions

HFNC demonstrates promise in several conditions requiring respiratory support. Further randomized trials are needed in the ED setting.

A framework for modeling bioimpedance measurements of nonhomogeneous tissues: a theoretical and simulation study

Objective.Bioimpedance technology is experiencing an increased use to assess health in a wide range of new consumer, research and clinical applications. However, the interaction between tissues producing bioimpedance data is often unclear.Methods.This work provides a novel theoretical framework to model bioimpedance measurements of nonhomogeneous tissues. We consider five case studies to validate the usefulness of our approach against finite element model simulations.Results.Theoretical and FEM-simulated apparent resistance and reactance data were in good agreement, with a maximum relative errors <4% and <8%, respectively.Conclusion.The biophysics-driven framework developed provides compact analytical expressions to model nonhomogeneous bioimpedance measurements including multiple tissues with arbitrary shape and electrical properties. This work provides a new perspective to interpret nonhomogeneous bioimpedance measurements usingseries,parallel, andseries-parallelcircuit-like topology equivalents.Significance.Our framework is a new tool to better understand and describe complex nonhomogeneous biological measurements as, for example, cardiac, brain and respiratory applications using (non)invasive electrodes.

Effects of nasal high flow on sympathovagal balance, sleep, and sleep-related breathing in patients with precapillary pulmonary hypertension

BACKGROUND

In precapillary pulmonary hypertension (PH), nasal high flow therapy (NHF) may favorably alter sympathovagal balance (SVB) and sleep-related breathing through washout of anatomical dead space and alleviation of obstructive sleep apnea (OSA) due to generation of positive airway pressure.

OBJECTIVES

To investigate the effects of NHF on SVB, sleep, and OSA in patients with PH, and compare them with those of positive airway pressure therapy (PAP).

METHODS

Twelve patients with PH (Nice class I or IV) and confirmed OSA underwent full polysomnography, and noninvasive monitoring of SVB parameters (spectral analysis of heart rate, diastolic blood pressure variability). Study nights were randomly split into four 2-h segments with no treatment, PAP, NHF 20 L/min, or NHF 50 L/min. In-depth SVB analysis was conducted on 10-min epochs during daytime and stable N2 sleep at nighttime.

RESULTS

At daytime and compared with no treatment, NHF20 and NHF50 were associated with a flow-dependent increase in peripheral oxygen saturation but a shift in SVB towards increased sympathetic drive. At nighttime, NHF20 was associated with increased parasympathetic drive and improvements in sleep efficiency, but did not alter OSA severity. NHF50 was poorly tolerated. PAP therapy improved OSA but had heterogenous effects on SVB and neutral effects on sleep outcomes. Hemodynamic effects were neutral for all interventions.

CONCLUSIONS

In sleeping PH patients with OSA NHF20 but not NHF50 leads to decreased sympathetic drive likely due to washout of anatomical dead space. NHF was not effective in lowering the apnea-hypopnoea index and NHF50 was poorly tolerated.

Visually guided inspiration breath-hold facilitated with nasal high flow therapy in locally advanced lung cancer

BACKGROUND AND PURPOSE

Reducing breathing motion in radiotherapy (RT) is an attractive strategy to reduce margins and better spare normal tissues. The objective of this prospective study (NCT03729661) was to investigate the feasibility of irradiation of non-small cell lung cancer (NSCLC) with visually guided moderate deep inspiration breath-hold (IBH) using nasal high-flow therapy (NHFT).

MATERIAL AND METHODS

Locally advanced NSCLC patients undergoing photon RT were given NHFT with heated humidified air (flow: 40 L/min with 80% oxygen) through a nasal cannula. IBH was monitored by optical surface tracking (OST) with visual feedback. At a training session, patients had to hold their breath as long as possible, without and with NHFT. For the daily cone beam CT (CBCT) and RT treatment in IBH, patients were instructed to keep their BH as long as it felt comfortable. OST was used to analyze stability and reproducibility of the BH, and CBCT to analyze daily tumor position. Subjective tolerance was measured with a questionnaire at 3 time points.

RESULTS

Of 10 included patients, 9 were treated with RT. Seven (78%) completed the treatment with NHFT as planned. At the training session, the mean BH length without NHFT was 39 s (range 15-86 s), and with NHFT 78 s (range 29-223 s) (p = .005). NHFT prolonged the BH duration by a mean factor of 2.1 (range 1.1-3.9s). The mean overall stability and reproducibility were within 1 mm. Subjective tolerance was very good with the majority of patients having no or minor discomfort caused by the devices. The mean inter-fraction tumor position variability was 1.8 mm (-1.1-8.1 mm;SD 2.4 mm).

CONCLUSION

NHFT for RT treatment of NSCLC in BH is feasible, well tolerated and significantly increases the breath-hold duration. Visually guided BH with OST is stable and reproducible. We therefore consider this an attractive patient-friendly approach to treat lung cancer patients with RT in BH.

High-flow nasal cannula oxygen therapy for outpatients undergoing flexible bronchoscopy: a randomised controlled trial

INTRODUCTION

High-flow nasal cannula (HFNC) provides benefits to patients undergoing flexible bronchoscopy (FOB). We compared the effects of HFNC versus standard therapy (ST) on gas exchange, lung volume and diaphragm function in patients undergoing FOB for bronchoalveolar lavage (BAL).

METHODS

36 outpatients were randomised to ST or HFNC. Arterial blood gases, episodes of severe desaturation, changes of end-expiratory lung impedance (ΔEELI), diaphragm ultrasound were recorded. Measurements were done at baseline (T0), after bronchoscope insertion (T1), at the end of the procedure (T2) and 10 min afterwards (T3).

RESULTS

Arterial partial oxygen pressure (PaO₂) was not different between T0 (10.8 (95% CI 8.7 to 12.0) kPa and T2 (11.1 (95% CI 10.4 to 12.0) kPa) with HFNC, while decreased from 11.1 (95% CI 10.5 to 12.1) to 9.1 (95% CI 8.4 to 9.8) kPa with ST. At T2, PaO₂ was significantly higher with HFNC than with ST (p<0.001). Also, with HFNC, compared with ST, fewer desaturations occurred (11% vs 56%; p<0.01). ΔEELI was no different at the different time points with HFNC, while with ST there was a significant decrease at T1 (-170 (95% CI -382 to -32) mL, p=0.003), T2 (-211 (95% CI -425 to -148) mL, p<0.001) and T3 (-213 (95% CI -398 to -81) mL, p<0.001), as opposed to T0. EELI was lower with ST than HFNC at T1 (p=0.006), T2 (p=0.001) and T3 (p=0.002). Diaphragm displacement was no different between groups (p=0.748), while the thickening fraction significantly increased at T1 and T2 with ST only (p<0.01).

CONCLUSIONS

During FOB for BAL, HFNC improves gas exchange, avoiding loss of end-expiratory lung volume and preventing increase of diaphragm activation.

TRIAL REGISTRATION NUMBER

NCT04016480.