Optimum support by high-flow nasal cannula in acute hypoxemic respiratory failure: effects of increasing flow rates

PURPOSE

Limited data exist on the correlation between higher flow rates of high-flow nasal cannula (HFNC) and its physiologic effects in patients with acute hypoxemic respiratory failure (AHRF). We assessed the effects of HFNC delivered at increasing flow rate on inspiratory effort, work of breathing, minute ventilation, lung volumes, dynamic compliance and oxygenation in AHRF patients.

METHODS

A prospective randomized cross-over study was performed in non-intubated patients with patients AHRF and a PaO₂/FiO₂ (arterial partial pressure of oxygen/fraction of inspired oxygen) ratio of ≤300 mmHg. A standard non-occlusive facial mask and HFNC at different flow rates (30, 45 and 60 l/min) were randomly applied, while maintaining constant FiO₂ (20 min/step). At the end of each phase, we measured arterial blood gases, inspiratory effort, based on swings in esophageal pressure (ΔPes) and on the esophageal pressure-time product (PTP_Pes), and lung volume, by electrical impedance tomography.

RESULTS

Seventeen patients with AHRF were enrolled in the study. At increasing flow rate, HFNC reduced ΔPes (p < 0.001) and PTP_Pes (p < 0.001), while end-expiratory lung volume (ΔEELV), tidal volume to ΔPes ratio (V _T/ΔPes, which corresponds to dynamic lung compliance) and oxygenation improved (p < 0.01 for all factors). Higher HFNC flow rate also progressively reduced minute ventilation (p < 0.05) without any change in arterial CO₂ tension (p = 0.909). The decrease in ΔPes, PTP_Pes and minute ventilation at increasing flow rates was better described by exponential fitting, while ΔEELV, V _T/ΔPes and oxygenation improved linearly.

CONCLUSIONS

In this cohort of patients with AHRF, an increasing HFNC flow rate progressively decreased inspiratory effort and improved lung aeration, dynamic compliance and oxygenation. Most of the effect on inspiratory workload and CO₂ clearance was already obtained at the lowest flow rate.

High-flow nasal oxygen in patients with COVID-19-associated acute respiratory failure

PURPOSE

Whether the use of high-flow nasal oxygen in adult patients with COVID-19 associated acute respiratory failure improves clinically relevant outcomes remains unclear. We thus sought to assess the effect of high-flow nasal oxygen on ventilator-free days, compared to early initiation of invasive mechanical ventilation, on adult patients with COVID-19.

METHODS

We conducted a multicentre cohort study using a prospectively collected database of patients with COVID-19 associated acute respiratory failure admitted to 36 Spanish and Andorran intensive care units (ICUs). Main exposure was the use of high-flow nasal oxygen (conservative group), while early invasive mechanical ventilation (within the first day of ICU admission; early intubation group) served as the comparator. The primary outcome was ventilator-free days at 28 days. ICU length of stay and all-cause in-hospital mortality served as secondary outcomes. We used propensity score matching to adjust for measured confounding.

RESULTS

Out of 468 eligible patients, a total of 122 matched patients were included in the present analysis (61 for each group). When compared to early intubation, the use of high-flow nasal oxygen was associated with an increase in ventilator-free days (mean difference: 8.0 days; 95% confidence interval (CI): 4.4 to 11.7 days) and a reduction in ICU length of stay (mean difference: - 8.2 days; 95% CI - 12.7 to - 3.6 days). No difference was observed in all-cause in-hospital mortality between groups (odds ratio: 0.64; 95% CI: 0.25 to 1.64).

CONCLUSIONS

The use of high-flow nasal oxygen upon ICU admission in adult patients with COVID-19 related acute hypoxemic respiratory failure may lead to an increase in ventilator-free days and a reduction in ICU length of stay, when compared to early initiation of invasive mechanical ventilation. Future studies should confirm our findings.

Awake prone positioning in patients with hypoxemic respiratory failure due to COVID-19: the PROFLO multicenter randomized clinical trial

Background

The effect of awake prone positioning on intubation rates is not established. The aim of this trial was to investigate if a protocol for awake prone positioning reduces the rate of endotracheal intubation compared with standard care among patients with moderate to severe hypoxemic respiratory failure due to COVID-19.

Methods

We conducted a multicenter randomized clinical trial. Adult patients with confirmed COVID-19, high-flow nasal oxygen or noninvasive ventilation for respiratory support and a PaO₂/FiO₂ ratio ≤ 20 kPa were randomly assigned to a protocol targeting 16 h prone positioning per day or standard care. The primary endpoint was intubation within 30 days. Secondary endpoints included duration of awake prone positioning, 30-day mortality, ventilator-free days, hospital and intensive care unit length of stay, use of noninvasive ventilation, organ support and adverse events. The trial was terminated early due to futility.

Results

Of 141 patients assessed for eligibility, 75 were randomized of whom 39 were allocated to the control group and 36 to the prone group. Within 30 days after enrollment, 13 patients (33%) were intubated in the control group versus 12 patients (33%) in the prone group (HR 1.01 (95% CI 0.46–2.21), P = 0.99). Median prone duration was 3.4 h [IQR 1.8–8.4] in the control group compared with 9.0 h per day [IQR 4.4–10.6] in the prone group (P = 0.014). Nine patients (23%) in the control group had pressure sores compared with two patients (6%) in the prone group (difference − 18% (95% CI − 2 to − 33%); P = 0.032). There were no other differences in secondary outcomes between groups.

Conclusions

The implemented protocol for awake prone positioning increased duration of prone positioning, but did not reduce the rate of intubation in patients with hypoxemic respiratory failure due to COVID-19 compared to standard care.

Trial registration

ISRCTN54917435. Registered 15 June 2020 (https://doi.org/10.1186/ISRCTN54917435).

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03602-9.

Impact of flow and temperature on patient comfort during respiratory support by high-flow nasal cannula

BACKGROUND

The high-flow nasal cannula (HFNC) delivers up to 60 l/min of humidified air/oxygen blend at a temperature close to that of the human body. In this study, we tested whether higher temperature and flow decrease patient comfort. In more severe patients, instead, we hypothesized that higher flow might be associated with improved comfort.

METHODS

A prospective, randomized, cross-over study was performed on 40 acute hypoxemic respiratory failure (AHRF) patients (PaO₂/FiO₂ ≤ 300 + pulmonary infiltrates + exclusion of cardiogenic edema) supported by HFNC. The primary outcome was the assessment of patient comfort during HFNC delivery at increasing flow and temperature. Two flows (30 and 60 l/min), each combined with two temperatures (31 and 37 °C), were randomly applied for 20 min (four steps per patient), leaving clinical FiO₂ unchanged. Toward the end of each step, the following were recorded: comfort by Visual Numerical Scale ranging between 1 (extreme discomfort) and 5 (very comfortable), together with respiratory parameters. A subgroup of more severe patients was defined by clinical FiO₂ ≥ 45%.

RESULTS

Patient comfort was reported as significantly higher during steps at the lower temperature (31 °C) in comparison to 37 °C, with the HFNC set at both 30 and 60 l/min (p < 0.0001). Higher flow, however, was not associated with poorer comfort. In the subgroup of patients with clinical FiO₂ ≥ 45%, both lower temperature (31 °C) and higher HFNC flow (60 l/min) led to higher comfort (p < 0.01).

CONCLUSIONS

HFNC temperature seems to significantly impact the comfort of AHRF patients: for equal flow, lower temperature could be more comfortable. Higher flow does not decrease patient comfort; at variance, it improves comfort in the more severely hypoxemic patient.

Comparison of high-flow nasal oxygen therapy with conventional oxygen therapy and noninvasive ventilation in adult patients with acute hypoxemic respiratory failure: A meta-analysis and systematic review

PURPOSE

The role of high-flow nasal oxygen (HFNO) therapy in adult patients with acute hypoxemic respiratory failure is controversial.

METHODS

This meta-analysis of prospective randomized controlled trials (RCTs) has been designed to compare HFNO with noninvasive ventilation (NIV) and conventional oxygen therapy in such patients.

RESULTS

Initial database searching revealed 336 RCTs, of which 7 were included in this meta-analysis. Five RCTs compared HFNO with standard oxygen therapy, one compared HFNO with NIV, and one compared all three. HFNO did not decrease the requirement of higher respiratory support compared with control group. HFNO was associated with improved respiratory rate and dyspnea score, and better comfort in 3 RCTs, whereas other studies did not find any difference.

CONCLUSION

High-flow nasal oxygen does not offer any benefit over NIV or conventional oxygen therapy in terms of requirement of higher respiratory support.

Using a high-flow nasal cannula provides superior results to OxyMask delivery in moderate to severe bronchiolitis: a randomized controlled study

The effectiveness of using a face mask with a small diffuser for oxygen delivery (OxyMask) was compared to use of a high-flow nasal cannula (HFNC) in patients with moderate or severe bronchiolitis.The study population in this open, phase 4, randomized controlled trial consisted of 60 patients aged 1-24 months diagnosed with moderate or severe bronchiolitis and admitted to an intensive care unit (ICU) for oxygen therapy. The patients were randomized into two groups according to the method of oxygen delivery: a diffuser mask group and an HFNC group.There were seven failures in the mask group and none in the HFNC group. The survival probability differed significantly between the two treatment methods (p = 0.009).Time to weaning off oxygen therapy was 56 h in the HFNC group and 96 h in the mask group (p < 0.001).Conclusion: HFNC use decreased the treatment failure rate and the duration of both oxygen therapy and ICU treatment compared to the diffuser mask, which implies that an HFNC should be the first choice for treating patients admitted to the ICU with severe bronchiolitis. What is known: • A high-flow nasal cannula (HFNC) does not significantly reduce the time on oxygen compared to standard therapy in children with moderate to severe bronchiolitis. Observational studies show that, since the introduction of HFNC, fewer children with bronchiolitis need intubation. For children with moderate to severe bronchiolitis there is no proof of its benefit. What Is New: • In children with moderate to severe bronchiolitis, HFNC provides faster and more effective improvement than can be achieved with a diffuser mask.

Performance of the ROX index to predict intubation in immunocompromised patients receiving high-flow nasal cannula for acute respiratory failure

Background

Delayed intubation is associated with high mortality. There is a lack of objective criteria to decide the time of intubation. We assessed a recently described combined oxygenation index (ROX index) to predict intubation in immunocompromised patients. The study is a secondary analysis of randomized trials in immunocompromised patients, including all patients who received high-flow nasal cannula (HFNC). The first objective was to evaluate the accuracy of the ROX index to predict intubation for patients with acute respiratory failure.

Results

In the study, 302 patients received HFNC. Acute respiratory failure was mostly related to pneumonia (n = 150, 49.7%). Within 2 (1–3) days, 115 (38.1%) patients were intubated. The ICU mortality rate was 27.4% (n = 83). At 6 h, the ROX index was lower for patients who needed intubation compared with those who did not [4.79 (3.69–7.01) vs. 6.10 (4.48–8.68), p < 0.001]. The accuracy of the ROX index to predict intubation was poor [AUC = 0.623 (0.557–0.689)], with low performance using the threshold previously found (4.88). In multivariate analysis, a higher ROX index was still independently associated with a lower intubation rate (OR = 0.89 [0.82–0.96], p = 0.04).

Conclusion

A ROX index greater than 4.88 appears to have a poor ability to predict intubation in immunocompromised patients with acute respiratory failure, although it remains highly associated with the risk of intubation and may be useful to stratify such risk in future studies.

Physiological effects of awake prone position in acute hypoxemic respiratory failure

BACKGROUND

The effects of awake prone position on the breathing pattern of hypoxemic patients need to be better understood. We conducted a crossover trial to assess the physiological effects of awake prone position in patients with acute hypoxemic respiratory failure.

METHODS

Fifteen patients with acute hypoxemic respiratory failure and PaO2/FiO2 < 200 mmHg underwent high-flow nasal oxygen for 1 h in supine position and 2 h in prone position, followed by a final 1-h supine phase. At the end of each study phase, the following parameters were measured: arterial blood gases, inspiratory effort (ΔPES), transpulmonary driving pressure (ΔPL), respiratory rate and esophageal pressure simplified pressure-time product per minute (sPTPES) by esophageal manometry, tidal volume (VT), end-expiratory lung impedance (EELI), lung compliance, airway resistance, time constant, dynamic strain (VT/EELI) and pendelluft extent through electrical impedance tomography.

RESULTS

Compared to supine position, prone position increased PaO2/FiO2 (median [Interquartile range] 104 mmHg [76-129] vs. 74 [69-93], p < 0.001), reduced respiratory rate (24 breaths/min [22-26] vs. 27 [26-30], p = 0.05) and increased ΔPES (12 cmH2O [11-13] vs. 9 [8-12], p = 0.04) with similar sPTPES (131 [75-154] cmH2O s min-1 vs. 105 [81-129], p > 0.99) and ΔPL (9 [7-11] cmH2O vs. 8 [5-9], p = 0.17). Airway resistance and time constant were higher in prone vs. supine position (9 cmH2O s arbitrary units-3 [4-11] vs. 6 [4-9], p = 0.05; 0.53 s [0.32-61] vs. 0.40 [0.37-0.44], p = 0.03). Prone position increased EELI (3887 arbitrary units [3414-8547] vs. 1456 [959-2420], p = 0.002) and promoted VT distribution towards dorsal lung regions without affecting VT size and lung compliance: this generated lower dynamic strain (0.21 [0.16-0.24] vs. 0.38 [0.30-0.49], p = 0.004). The magnitude of pendelluft phenomenon was not different between study phases (55% [7-57] of VT in prone vs. 31% [14-55] in supine position, p > 0.99).

CONCLUSIONS

Prone position improves oxygenation, increases EELI and promotes VT distribution towards dependent lung regions without affecting VT size, ΔPL, lung compliance and pendelluft magnitude. Prone position reduces respiratory rate and increases ΔPES because of positional increases in airway resistance and prolonged expiratory time. Because high ΔPES is the main mechanistic determinant of self-inflicted lung injury, caution may be needed in using awake prone position in patients exhibiting intense ΔPES. Clinical trail registeration: The study was registered on clinicaltrials.gov (NCT03095300) on March 29, 2017.

Efficacy of non-invasive and invasive respiratory management strategies in adult patients with acute hypoxaemic respiratory failure: a systematic review and network meta-analysis

Background

Although non-invasive respiratory management strategies have been implemented to avoid intubation, patients with de novo acute hypoxaemic respiratory failure (AHRF) are high risk of treatment failure. In the previous meta-analyses, the effect of non-invasive ventilation was not evaluated according to ventilation modes in those patients. Furthermore, no meta-analyses comparing non-invasive respiratory management strategies with invasive mechanical ventilation (IMV) have been reported. We performed a network meta-analysis to compare the efficacy of non-invasive ventilation according to ventilation modes with high-flow nasal oxygen (HFNO), standard oxygen therapy (SOT), and IMV in adult patients with AHRF.

Methods

The Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, and Ichushi databases were searched. Studies including adults with AHRF and randomized controlled trials (RCTs) comparing two different respiratory management strategies (continuous positive airway pressure (CPAP), pressure support ventilation (PSV), HFNO, SOT, or IMV) were reviewed.

Results

We included 25 RCTs (3,302 participants: 27 comparisons). Using SOT as the reference, CPAP (risk ratio [RR] 0.55; 95% confidence interval [CI] 0.31–0.95; very low certainty) was associated significantly with a lower risk of mortality. Compared with SOT, PSV (RR 0.81; 95% CI 0.62–1.06; low certainty) and HFNO (RR 0.90; 95% CI 0.65–1.25; very low certainty) were not associated with a significantly lower risk of mortality. Compared with IMV, no non-invasive respiratory management was associated with a significantly lower risk of mortality, although all certainties of evidence were very low. The probability of being best in reducing short-term mortality among all possible interventions was higher for CPAP, followed by PSV and HFNO; IMV and SOT were tied for the worst (surface under the cumulative ranking curve value: 93.2, 65.0, 44.1, 23.9, and 23.9, respectively).

Conclusions

When performing non-invasive ventilation among patients with de novo AHRF, it is important to avoid excessive tidal volume and lung injury. Although pressure support is needed for some of these patients, it should be applied with caution because this may lead to excessive tidal volume and lung injury.

Trial registration protocols.io (Protocol integer ID 49375, April 23, 2021). 10.17504/protocols.io.buf7ntrn.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03835-8.

Non-invasive ventilation alternating with high-flow nasal oxygen versus high-flow nasal oxygen alone after extubation in COPD patients: a post hoc analysis of a randomized controlled trial

Background

Several randomized clinical trials have shown that non-invasive ventilation (NIV) applied immediately after extubation may prevent reintubation in patients at high-risk of extubation failure. However, most of studies included patients with chronic respiratory disorders as well as patients without underlying respiratory disease. To date, no study has shown decreased risk of reintubation with prophylactic NIV after extubation among patients with chronic obstructive pulmonary disease (COPD). We hypothesized that prophylactic NIV after extubation may decrease the risk of reintubation in COPD patients as compared with high-flow nasal oxygen. We performed a post hoc subgroup analysis of COPD patients included in a multicenter, randomized, controlled trial comparing prophylactic use of NIV alternating with high-flow nasal oxygen versus high-flow nasal oxygen alone immediately after extubation.

Results

Among the 651 patients included in the original study, 150 (23%) had underlying COPD including 86 patients treated with NIV alternating with high-flow nasal oxygen and 64 patients treated with high-flow nasal oxygen alone. The reintubation rate was 13% (11 out of 86 patients) with NIV and 27% (17 out of 64 patients) with high-flow nasal oxygen alone [difference, − 14% (95% CI − 27% to − 1%); p = 0.03]. Whereas reintubation rates were significantly lower with NIV than with high-flow nasal oxygen alone at 72 h and until ICU discharge, mortality in ICU did not differ between groups: 6% (5/86) with NIV vs. 9% (6/64) with high-flow nasal oxygen alone [difference − 4% (95% CI − 14% to 5%); p = 0.40].

Conclusions

In COPD patients, prophylactic NIV alternating with high-flow nasal oxygen significantly decreased the risk of reintubation compared with high-flow nasal oxygen alone.

Trial registration The study was registered at http://www.clinicaltrials.gov with the trial registration number NCT03121482 (20 April 2017)

Pediatric airway surgery under spontaneous respiration using high-flow nasal oxygen

OBJECTIVES

In pediatric airway surgery, SponTaneous Respiration using IntraVEnous anesthesia and Hi-flow nasal oxygen (STRIVE Hi) has not been well explored. Here, we report our experience of using STRIVE Hi in endoscopic evaluations and surgeries of the pediatric airway.

METHODS

This retrospective review was based on 45 airway procedures conducted under STRIVE Hi, performed by a single surgeon at a single institute from May 2017 to September 2018. After induction of anesthesia, continuous infusion with propofol and remifentanil was provided to ensure an adequate level of anesthesia and supply of humidified oxygen via a nasal cannula. Monitoring was conducted using a transcutaneous CO₂ sensor and a pulse oximeter, and the oxygen reserve and bispectral indexes were measured. No muscle relaxant was administered.

RESULTS

The median age of the patients was 16.0 months (range: 1-215 months) and the median weight was 10.2 kg (range: 2.4-38.5 kg). The median duration of spontaneous respiration was min 40 (range: 10-140 min). The airway procedures included diagnostic microlaryngoscopy, tracheocutaneous fistula excision, balloon dilation, supraglottoplasty, laryngeal cleft repair, injection laryngoplasty, papilloma excision, and subglottic cyst removal. During these procedures, STRIVE Hi facilitated evaluation of dynamic obstruction of the airway and the immediate outcome of surgical treatment and provided a good surgical view. Intubation and the termination of spontaneous respiration were required in only five patients.

CONCLUSIONS

STRIVE Hi is an effective and feasible anesthesia option in pediatric airway surgery. It provides unobstructed surgical access and is applicable to a wide range of procedures.

Long-term outcomes of patients with COVID-19 treated with helmet noninvasive ventilation or usual respiratory support: follow-up study of the Helmet-COVID randomized clinical trial

PURPOSE

To evaluate whether helmet noninvasive ventilation compared to usual respiratory support reduces 180-day mortality and improves health-related quality of life (HRQoL) in patients with acute hypoxemic respiratory failure due to COVID-19 pneumonia.

METHODS

This is a pre-planned follow-up study of the Helmet-COVID trial. In this multicenter, randomized clinical trial, adults with acute hypoxemic respiratory failure (n = 320) due to coronavirus disease 2019 (COVID-19) were randomized to receive helmet noninvasive ventilation or usual respiratory support. The modified intention-to-treat population consisted of all enrolled patients except three who were lost at follow-up. The study outcomes were 180-day mortality, EuroQoL (EQ)-5D-5L index values, and EQ-visual analog scale (EQ-VAS). In the modified intention-to-treat analysis, non-survivors were assigned a value of 0 for EQ-5D-5L and EQ-VAS.

RESULTS

Within 180 days, 63/159 patients (39.6%) died in the helmet noninvasive ventilation group compared to 65/158 patients (41.1%) in the usual respiratory support group (risk difference - 1.5% (95% confidence interval [CI] - 12.3, 9.3, p = 0.78). In the modified intention-to-treat analysis, patients in the helmet noninvasive ventilation and the usual respiratory support groups did not differ in EQ-5D-5L index values (median 0.68 [IQR 0.00, 1.00], compared to 0.67 [IQR 0.00, 1.00], median difference 0.00 [95% CI - 0.32, 0.32; p = 0.91]) or EQ-VAS scores (median 70 [IQR 0, 93], compared to 70 [IQR 0, 90], median difference 0.00 (95% CI - 31.92, 31.92; p = 0.55).

CONCLUSIONS

Helmet noninvasive ventilation did not reduce 180-day mortality or improve HRQoL compared to usual respiratory support among patients with acute hypoxemic respiratory failure due to COVID-19 pneumonia.

Non-invasive ventilation versus high-flow nasal oxygen for postextubation respiratory failure in ICU: a post-hoc analysis of a randomized clinical trial

Background

In intensive care units (ICUs), patients experiencing post-extubation respiratory failure have poor outcomes. The use of noninvasive ventilation (NIV) to treat post-extubation respiratory failure may increase the risk of death. This study aims at comparing mortality between patients treated with NIV alternating with high-flow nasal oxygen or high-flow nasal oxygen alone.

Methods

Post-hoc analysis of a multicenter, randomized, controlled trial focusing on patients who experienced post-extubation respiratory failure within the 7 days following extubation. Patients were classified in the NIV group or the high-flow nasal oxygen group according to oxygenation strategy used after the onset of post-extubation respiratory failure. Patients reintubated within the first hour after extubation and those promptly reintubated without prior treatment were excluded. The primary outcome was mortality at day 28 after the onset of post-extubation respiratory failure.

Results

Among 651 extubated patients, 158 (25%) experienced respiratory failure and 146 were included in the analysis. Mortality at day 28 was 18% (15/84) using NIV alternating with high-flow nasal oxygen and 29% (18/62) with high flow nasal oxygen alone (difference, − 11% [95% CI, − 25 to 2]; p = 0.12). Among the 46 patients with hypercapnia at the onset of respiratory failure, mortality at day 28 was 3% (1/33) with NIV and 31% (4/13) with high-flow nasal oxygen alone (difference, − 28% [95% CI, − 54 to − 6]; p = 0.006). The proportion of patients reintubated 48 h after the onset of post-extubation respiratory failure was 44% (37/84) with NIV and 52% (32/62) with high-flow nasal oxygen alone (p = 0.21).

Conclusions

In patients with post-extubation respiratory failure, NIV alternating with high-flow nasal oxygen might not increase the risk of death.

Trial registration number

The trial was registered at http://www.clinicaltrials.gov with the registration number NCT03121482 the 20th April 2017.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03621-6.

An expanded definition of acute respiratory distress syndrome: Challenging the status quo

Although the Berlin definition of acute respiratory distress syndrome (ARDS), 2012 has been widely used in clinical practice, issues have occasionally been raised regarding various criteria since it was proposed. High-flow nasal oxygen (HFNO) is widely used for effective respiratory support in acute respiratory failure. As patients who do not require ventilation but meet the Berlin criteria have similar characteristics to those with ARDS, the definition of ARDS may be broadened to include patients receiving HFNO. As the PaO₂/FiO₂ under-recognizes the diagnosis of ARDS, a SpO₂/FiO₂ value of ≤315 may be considered instead of a PaO₂/FiO₂ value of ≤300 for diagnosing the condition in resource-constrained settings. In this context, patients with severe COVID-19 always meet other criteria for ARDS except for 7-day acute onset. Therefore, the timeframe for the onset of ARDS may be extended to up to 14 days. An expanded definition of ARDS may allow early identification of patients with less severe diseases and facilitate testing and application of new therapies in patients with a high risk of poor outcomes. Here, we discuss the major controversies regarding the extension of the ARDS definition with a view to improving clinical implementation and patient outcomes.

Utility of high-flow nasal oxygen in comparison to conventional oxygen therapy during upper gastrointestinal endoscopic procedures under sedation: A systematic review and meta-analyses

BACKGROUND

Sedation and analgesia are the integral components of modern-day upper gastrointestinal (GI) endoscopic procedures. Irrespective of the sedative agent, hypoxia is the most commonly encountered unwarranted event with sedation. The current study intends to scrutinize whether high-flow nasal oxygen (HFNO) is advantageous for providing respiratory support during upper GI endoscopic procedures over other conventional low-flow oxygen delivery modalities, e.g. nasal cannula, facemask, etc. METHODS: An extensive screening of electronic databases was done till July 31, 2022, after enlisting in International prospective register of systematic reviews (PROSPERO) (CRD42021245409). Randomized controlled trials (RCT), comparative cohort studies, case series, cross-sectional studies and case-control studies evaluating the utility of HFNO during upper GI endoscopy under sedation were included in this meta-analysis.

RESULTS

We retrieved eight randomized control studies and one longitudinal study with 3294 patients. The application of HFNO during endoscopy led to lesser incidence of desaturation spells (odds ratio [OR] = 0.23; 95% CI 0.11-0.48; I² = 71%), reduced procedural interruption (OR = 0.11; 95% CI 0.02-0.60; I² = 88%), better nadir SpO² level during procedure (mean difference [MD] = 3.16; 95% CI 0.54-5.78; I² = 73%), overall lesser incidence of sedation-related adverse events (OR = 0.63; 95% CI 0.42-0.93; I² = 25%), with no significant impact on the duration of endoscopy (MD = 0.15; 95% CI - 0.02 to 0.31, I² = 0%).

CONCLUSION

HFNO is a novel option for upper GI endoscopy under sedation.

CLINICAL TRIAL NUMBER AND REGISTRY URL

CRD42021245409 ( https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021245409 ).

High-flow nasal oxygen (HFNO) for patients with Covid-19 outside intensive care units

Introduction

High-flow nasal oxygen (HFNO) has traditionally only been used in intensive care units (ICU) especially in acute respiratory distress syndrome (ARDS).

Methods

We studied the use of HFNO at Södersjukhuset, Stockholm, in patients with moderate to severe ARDS related to Covid-19 as well as its benefits both for patients and to offload the ICU. The patients were observed with frequent controls to assess the need of ICU in case of deterioration.

Results

We studied 41 patients with HFNO treatment either as primarily treatment (Step-Up) or after stabilizing in the ICU (Step-Down). The average duration for treatment with HFNO was 5.6 days. Of these patients 55% were discharged home or to geriatric rehabilitation and 10% avoided ICU completely. The usage of HFNO saved in total 229 days in the ICU. Mortality was higher among elderly patients, and patients with comorbidities (mainly hypertension and obesity).

Discussion and conclusion

HFNO treatment is feasible and efficient for patients with Covid-19, saving resources in the ICU and offering additional advantages as waken proning and fewer complications compared to traditional ICU care. It requires however frequent controls as deterioration is recurrent.

Noninvasive Respiratory Assist Devices in the Management of COVID-19-related Hypoxic Respiratory Failure: Pune ISCCM COVID-19 ARDS Study Consortium (PICASo)

Objective

To determine whether high-flow nasal oxygen (HFNO) or noninvasive ventilator (NIV) can avoid invasive mechanical ventilation (IMV) in COVID-19-related acute respiratory distress syndrome (ADRS), and the outcome predictors of these modalities.

Design

Multicenter retrospective study conducted in 12 ICUs in Pune, India.

Patients

Patients with COVID-19 pneumonia who had PaO₂/FiO₂ ratio <150 and were treated with HFNO and/or NIV.

Intervention

HFNO and/or NIV.

Measurements

The primary outcome was to assess the need of IMV. Secondary outcomes were death at Day 28 and mortality rates in different treatment groups.

Main results

Among 1,201 patients who met the inclusion criteria, 35.9% (431/1,201) were treated successfully with HFNO and/or NIV and did not require IMV. About 59.5% (714/1,201) patients needed IMV for the failure of HFNO and/or NIV. About 48.3, 61.6, and 63.6% of patients who were treated with HFNO, NIV, or both, respectively, needed IMV. The need of IMV was significantly lower in the HFNO group (p <0.001). The 28-day mortality was 44.9, 59.9, and 59.6% in the patients treated with HFNO, NIV, or both, respectively (p <0.001). On multivariate regression analysis, presence of any comorbidity, SpO₂ <90%, and presence of nonrespiratory organ dysfunction were independent and significant determinants of mortality (p <0.05).

Conclusions

During COVID-19 pandemic surge, HFNO and/or NIV could successfully avoid IMV in 35.5% individuals with PO₂/FiO₂ ratio <150. Those who needed IMV due to failure of HFNO or NIV had high (87.5%) mortality.

How to cite this article

Jog S, Zirpe K, Dixit S, Godavarthy P, Shahane M, Kadapatti K, et al. Noninvasive Respiratory Assist Devices in the Management of COVID-19-related Hypoxic Respiratory Failure: Pune ISCCM COVID-19 ARDS Study Consortium (PICASo). Indian J Crit Care Med 2022;26(7):791-797.

Impact of flow and temperature on patient comfort during respiratory support by high-flow nasal cannula

BACKGROUND

The high-flow nasal cannula (HFNC) delivers up to 60 l/min of humidified air/oxygen blend at a temperature close to that of the human body. In this study, we tested whether higher temperature and flow decrease patient comfort. In more severe patients, instead, we hypothesized that higher flow might be associated with improved comfort.

METHODS

A prospective, randomized, cross-over study was performed on 40 acute hypoxemic respiratory failure (AHRF) patients (PaO₂/FiO₂ ≤ 300 + pulmonary infiltrates + exclusion of cardiogenic edema) supported by HFNC. The primary outcome was the assessment of patient comfort during HFNC delivery at increasing flow and temperature. Two flows (30 and 60 l/min), each combined with two temperatures (31 and 37 °C), were randomly applied for 20 min (four steps per patient), leaving clinical FiO₂ unchanged. Toward the end of each step, the following were recorded: comfort by Visual Numerical Scale ranging between 1 (extreme discomfort) and 5 (very comfortable), together with respiratory parameters. A subgroup of more severe patients was defined by clinical FiO₂ ≥ 45%.

RESULTS

Patient comfort was reported as significantly higher during steps at the lower temperature (31 °C) in comparison to 37 °C, with the HFNC set at both 30 and 60 l/min (p < 0.0001). Higher flow, however, was not associated with poorer comfort. In the subgroup of patients with clinical FiO₂ ≥ 45%, both lower temperature (31 °C) and higher HFNC flow (60 l/min) led to higher comfort (p < 0.01).

CONCLUSIONS

HFNC temperature seems to significantly impact the comfort of AHRF patients: for equal flow, lower temperature could be more comfortable. Higher flow does not decrease patient comfort; at variance, it improves comfort in the more severely hypoxemic patient.

Subphenotypes in patients with acute respiratory distress syndrome treated with high-flow oxygen

BACKGROUND

Acute respiratory distress syndrome (ARDS) subphenotypes differ in outcomes and treatment responses. Subphenotypes in high-flow nasal oxygen (HFNO)-treated ARDS patients have not been investigated.

OBJECTIVES

To identify biological subphenotypes in HFNO-treated ARDS patients.

METHODS

Secondary analysis of a prospective multicenter observational study including ARDS patients supported with HFNO. Plasma inflammation markers (interleukin [IL]-6, IL-8, and IL-33 and soluble suppression of tumorigenicity-2 [sST2]) and lung epithelial (receptor for advanced glycation end products [RAGE] and surfactant protein D [SP-D]) and endothelial (angiopoietin-2 [Ang-2]) injury were measured. These biomarkers and bicarbonate were used in K-means cluster analysis to identify subphenotypes. Logistic regression was performed on biomarker combinations to predict clustering. We chose the model with the best AUROC and the lowest number of variables. This model was used to describe the HAIS (High-flow ARDS Inflammatory Subphenotype) score.

RESULTS

Among 41 HFNO patients, two subphenotypes were identified. Hyperinflammatory subphenotype (n = 17) showed higher biomarker levels than hypoinflammatory (n = 24). Despite similar baseline characteristics, the hyperinflammatory subphenotype had higher 60-day mortality (47 vs 8.3% p = 0.014) and longer ICU length of stay (22.0 days [18.0-30.0] vs 39.5 [25.5-60.0], p = 0.034). The HAIS score, based on IL-8 and sST2, accurately distinguished subphenotypes (AUROC 0.96 [95%CI: 0.90-1.00]). A HAIS score ≥ 7.45 was predictor of hyperinflammatory subphenotype.

CONCLUSION

ARDS patients treated with HFNO exhibit two biological subphenotypes that have similar clinical characteristics, but hyperinflammatory patients have worse outcomes. The HAIS score may identify patients with hyperinflammatory subphenotype and might be used for enrichment strategies in future clinical trials.

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).

High-flow nasal cannula oxygen therapy in acute hypoxemic respiratory failure and COVID-19-related respiratory failure

Although standard oxygen face masks are first-line therapy for patients with acute hypoxemic respiratory failure, high-flow nasal cannula oxygen therapy has gained major popularity in intensive care units. The physiological effects of high-flow oxygen counterbalance the physiological consequences of acute hypoxemic respiratory failure by lessening the deleterious effects of intense and prolonged inspiratory efforts generated by patients. Its simplicity of application for physicians and nurses and its comfort for patients are other arguments for its use in this setting. Although clinical studies have reported a decreased risk of intubation with high-flow oxygen compared with standard oxygen, its survival benefit is uncertain. A more precise definition of acute hypoxemic respiratory failure, including a classification of severity based on oxygenation levels, is needed to better compare the efficiencies of different non-invasive oxygenation support methods (standard oxygen, high-flow oxygen, and non-invasive ventilation). Additionally, the respective role of each non-invasive oxygenation support method needs to be established through further clinical trials in acute hypoxemic respiratory failure, especially in severe forms.

Effects of non-invasive respiratory support in post-operative patients: a systematic review and network meta-analysis

BACKGROUND

Re-intubation secondary to post-extubation respiratory failure in post-operative patients is associated with increased patient morbidity and mortality. Non-invasive respiratory support (NRS) alternative to conventional oxygen therapy (COT), i.e., high-flow nasal oxygen, continuous positive airway pressure, and non-invasive ventilation (NIV), has been proposed to prevent or treat post-extubation respiratory failure. Aim of the present study is assessing the effects of NRS application, compared to COT, on the re-intubation rate (primary outcome), and time to re-intubation, incidence of nosocomial pneumonia, patient discomfort, intensive care unit (ICU) and hospital length of stay, and mortality (secondary outcomes) in adult patients extubated after surgery.

METHODS

A systematic review and network meta-analysis of randomized and non-randomized controlled trials. A search from Medline, Embase, Scopus, Cochrane Central Register of Controlled Trials, and Web of Science from inception until February 2, 2024 was performed.

RESULTS

Thirty-three studies (11,292 patients) were included. Among all NRS modalities, only NIV reduced the re-intubation rate, compared to COT (odds ratio 0.49, 95% confidence interval 0.28; 0.87, p = 0.015, I2 = 60.5%, low certainty of evidence). In particular, this effect was observed in patients receiving NIV for treatment, while not for prevention, of post-extubation respiratory failure, and in patients at high, while not low, risk of post-extubation respiratory failure. NIV reduced the rate of nosocomial pneumonia, ICU length of stay, and ICU, hospital, and long-term mortality, while not worsening patient discomfort.

CONCLUSIONS

In post-operative patients receiving NRS after extubation, NIV reduced the rate of re-intubation, compared to COT, when used for treatment of post-extubation respiratory failure and in patients at high risk of post-extubation respiratory failure.

Comparison between high-flow nasal oxygen (HFNO) alternated with non-invasive ventilation (NIV) and HFNO and NIV alone in patients with COVID-19: a retrospective cohort study

BACKGROUND

Non-invasive respiratory support (conventional oxygen therapy [COT], non-invasive ventilation [NIV], high-flow nasal oxygen [HFNO], and NIV alternated with HFNO [NIV + HFNO] may reduce the need for invasive mechanical ventilation (IMV) in patients with COVID-19. The outcome of patients treated non-invasively depends on clinical severity at admission. We assessed the need for IMV according to NIV, HFNO, and NIV + HFNO in patients with COVID-19 according to disease severity and evaluated in-hospital survival rates and hospital and intensive care unit (ICU) lengths of stay.

METHODS

This cohort study was conducted using data collected between March 2020 and July 2021. Patients ≥ 18 years admitted to the ICU with a diagnosis of COVID-19 were included. Patients hospitalized for < 3 days, receiving therapy (COT, NIV, HFNO, or NIV + HFNO) for < 48 h, pregnant, and with no primary outcome data were excluded. The COT group was used as reference for multivariate Cox regression model adjustment.

RESULTS

Of 1371 patients screened, 958 were eligible: 692 (72.2%) on COT, 92 (9.6%) on NIV, 31 (3.2%) on HFNO, and 143 (14.9%) on NIV + HFNO. The results for the patients in each group were as follows: median age (interquartile range): NIV (64 [49-79] years), HFNO (62 [55-70] years), NIV + HFNO (62 [48-72] years) (p = 0.615); heart failure: NIV (54.5%), HFNO (36.3%), NIV + HFNO (9%) (p = 0.003); diabetes mellitus: HFNO (17.6%), NIV + HFNO (44.7%) (p = 0.048). > 50% lung damage on chest computed tomography (CT): NIV (13.3%), HFNO (15%), NIV + HFNO (71.6%) (p = 0.038); SpO2/FiO2: NIV (271 [118-365] mmHg), HFNO (317 [254-420] mmHg), NIV + HFNO (229 [102-317] mmHg) (p = 0.001); rate of IMV: NIV (26.1%, p = 0.002), HFNO (22.6%, p = 0.023), NIV + HFNO (46.8%); survival rate: HFNO (83.9%), NIV + HFNO (63.6%) (p = 0.027); ICU length of stay: NIV (8.5 [5-14] days), NIV + HFNO (15 [10-25] days (p < 0.001); hospital length of stay: NIV (13 [10-21] days), NIV + HFNO (20 [15-30] days) (p < 0.001). After adjusting for comorbidities, chest CT score and SpO2/FiO2, the risk of IMV in patients on NIV + HFNO remained high (hazard ratio, 1.88; 95% confidence interval, 1.17-3.04).

CONCLUSIONS

In patients with COVID-19, NIV alternating with HFNO was associated with a higher rate of IMV independent of the presence of comorbidities, chest CT score and SpO2/FiO2. Trial registration ClinicalTrials.gov identifier: NCT05579080.

Effect of prone positioning and high flow nasal oxygen on oxygenation and overall outcome in spontaneously breathing awake patient with severe COVID-19 induced acute hypoxemic respiratory failure: A prospective observational study

Background

Previous studies suggest that prone positioning can increase PaO2/FiO2 and reduce mortality in moderate to severe acute respiratory distress syndrome. Effect of prone positioning and high flow nasal oxygen has been studied individually in COVID-19 patients but their combined effect on patient's outcome is yet to be reported.

Methods

In this study 120 severe COVID-19 positive patients were included and placed in awake prone positioning with high flow nasal oxygen. The efficacy in improving oxygenation with prone positioning and high flow nasal oxygen were evaluated by blood gas analysis. The primary outcome was a proportion of patients requiring non-invasive ventilation or invasive ventilation. The secondary outcomes were a comparison of arterial blood gas parameters and biochemical inflammatory parameters pre proning, end of first proning and end of last prone position in these patients.

Results

We found only 35 patients (34.3%) required the need for non-invasive or invasive mechanical ventilation support whereas 67 patients (65.7%) were managed successfully on high flow nasal oxygen along with awake prone positioning (p = 0.001). We found there were statistically significant improvements in arterial blood gas parameters and biochemical inflammatory markers after the end of last prone positioning with high flow nasal oxygen.

Conclusions

Early application of prone positioning in combination with high flow nasal oxygen may help in avoiding mechanical ventilation by improving oxygenation and biochemical inflammatory markers.