High flow through nasal cannula in exacerbated COPD patients: a systematic review

Physiological effects and clinical evidence of high-flow nasal cannula during acute exacerbation in COPD patients: A narrative review

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death worldwide. During severe exacerbations, COPD patients may develop acute respiratory failure (ARF), often necessitating hospital admission due to impaired gas exchange. In COPD patients, the diaphragm is subjected to an increased workload resulting from airflow limitations and geometric changes in the thorax due to pulmonary hyperinflation. Noninvasive ventilation (NIV) plays a crucial role in managing type II ARF by improving alveolar ventilation, reducing the work of breathing, minimizing the need for endotracheal intubation (ETI), and decreasing both hospital stays and mortality rates. Studies have shown that approximately 64% of patients with acute exacerbation of COPD (AECOPD) may fail NIV, primarily due to worsening respiratory function, interface intolerance, cardiovascular instability, or neurological deterioration. For patients intolerant to NIV, a trial with a high-flow nasal cannula (HFNC) is recommended. Recently, HFNC has gained popularity as a novel respiratory support system and is increasingly used in routine clinical practice for AECOPD patients. It delivers warmed, humidified, and oxygen-enriched air through a nasal cannula at flow rates of up to 60 L/min. This narrative review aims to describe the physiological effects of HFNC in the COPD population and provide an updated overview of HFNC's role in AECOPD patients requiring hospitalization.

High-velocity nasal insufflation versus noninvasive positive pressure ventilation for moderate acute exacerbation of chronic obstructive pulmonary disease in the emergency department: A randomized clinical trial

BACKGROUND

Acute exacerbations of chronic obstructive pulmonary disease (COPD) in the emergency department (ED) involve dyspnea, cough, and chest discomfort; frequent exacerbations are associated with increased mortality and reduced quality of life. Noninvasive positive pressure ventilation (NiPPV) is commonly used to help relieve symptoms but is limited due to patient intolerance. We aimed to determine whether high-velocity nasal insufflation (HVNI) is noninferior to NiPPV in relieving dyspnea within 4 h in ED patients with acute hypercapnic respiratory failure.

METHODS

This randomized control trial was conducted in seven EDs in the United States. Symptomatic patients with suspected COPD, partial pressure of carbon dioxide (pCO2) ≥ 60 mm Hg, and venous pH 7.0-7.35 were randomized to receive HVNI (n = 36) or NiPPV (n = 32). The primary outcome was dyspnea severity 4 h after the initiation of study intervention, as measured by the Borg score. Secondary outcomes included vital signs, oxygen saturation, venous pCO2, venous pH, patient discomfort level, and need for endotracheal intubation.

RESULTS

Sixty-eight patients were randomized between November 5, 2020, and May 10, 2023 (mean age 65.6 years; 47% women). The initial pCO2 was 77.7 ± 13.6 mm Hg versus 76.5 ± 13.6 mm Hg and the initial venous pH was 7.27 ± 0.063 versus 7.27 ± 0.043 in the HVNI and NiPPV groups, respectively. Dyspnea was similar in the HVNI and NiPPV groups at baseline (dyspnea scale score 5.4 ± 2.93 and 5.6 ± 2.41) and HVNI was noninferior to NiPPV at the following time points: 30 min (3.97 ± 2.82 and 4.54 ± 1.65, p = 0.006), 60 min (3.09 ± 2.70 and 4.07 ± 1.77, p < 0.001), and 4 h (3.17 ± 2.59 and 3.34 ± 2.04, p = 0.03). At 4 h, there was no difference between the groups in the pCO2 mm Hg (68.76 and 67.29, p = 0.63). Patients reported better overall comfort levels in the HVNI group at 30 min, 60 min, and 4 h (p = 0.003).

CONCLUSIONS

In participants with symptomatic COPD, HVNI was noninferior to NiPPV in relieving dyspnea 4 h after therapy initiation. HVNI may be a reasonable treatment option for some patients experiencing moderate acute exacerbations of COPD in the ED.

Real-world data on home high-flow nasal cannula oxygen therapy in end-stage respiratory disease

High-flow nasal oxygen therapy (HFNOT) is a cornerstone treatment modality in severe acute hypoxemic respiratory failure, with benefits in improving oxygen deficit while normalizing breathing rate and having an effect on airway humidification. These physiological effects indicate a potential benefit in end-stage chronic respiratory failure. We aimed to assess the clinical impact of home HFNOT in reducing both exacerbation rates and overall disease burden in end-stage chronic respiratory disease. We designed a retrospective study including patients followed in the pulmonology department of a tertiary center who started home HFNOT until June 2023. Pre- and post-home HFNOT exacerbations and hospital admissions were registered, and each patient served as their own control for the statistical analysis. In total, 36 patients were included in the study: 24 patients (66.7%) with interstitial lung disease and 12 (33.3%) with obstructive lung disease. Overall, the median titrated fraction of inspired oxygen was significantly lower in obstructive patients; no significant differences were found between groups regarding titrated airflow. Obstructive patients had a significantly higher number of pre-treatment exacerbations and hospital stays. Both clinical subgroups presented less median overall post-treatment exacerbations and hospital admissions vs. pre-treatment start. Although mortality was high, home treatment was well tolerated by most patients, with only one patient interrupting high-flow therapy due to intolerance. Home HFNOT proved to be an overall feasible treatment strategy for patients with end-stage respiratory disease. Obstructive lung disease patients benefited the most from the treatment, possibly due to hypercapnia correction.

The Effects of Home High-Flow Nasal Cannula Oxygen Therapy on Clinical Outcomes in Patients with Severe COPD and Frequent Exacerbations

Background: Chronic Obstructive Pulmonary Disease (COPD) is a disease with high morbidity and mortality globally. Exacerbations of COPD are major contributors to disease progression and a decline in health-related quality of life (HRQoL). High-flow nasal cannula (HFNC) oxygen therapy is an innovative therapy that provides humidified and heated blended air and oxygen through a nasal cannula. There is some preliminary evidence supporting the effectiveness of HFNC in managing COPD exacerbations, but there are limited data on its effectiveness when used at home for patients with stable, severe COPD. The aim of the present study is to test the hypothesis that home HFNC can decrease the COPD exacerbations rate and hospital admissions and improve HRQoL measures in severe COPD patients with frequent COPD exacerbations. Methods: In a prospective proof-of-concept interventional multicenter study, 40 GOLD stage III and IV COPD patients with a high disease burden (≥2 exacerbations treated with antibiotics and/or corticosteroids) and ≥1 hospital admission in the last year were included. Patients were given instructions on the usage of HFNC by a ventilation practitioner during a group session. The flow rate was 25-30 L/min and FiO2 was 21-35%. Outcome measures included the COPD exacerbations rate, hospital admissions, in-hospital days, Medical Research Council dyspnea (MRC) score, Clinical COPD Questionnaire (CCQ) score, Hospital Anxiety Depression Scale (HADS) scores and capillary pCO2. Repeated analysis of variance (ANOVA) was used to analyze the data. Significant effects identified in the ANOVA were further examined using Student's t-tests. Results: After 1 year, 27 patients could be evaluated. The COPD exacerbations rate decreased by 1.40 (mean difference ± SD: 1.40 ± 2.09; p = 0.002), hospital admissions decreased by 0.96 admissions per year (0.96 ± 1.37; p = 0.001), and in-hospital days decreased by 7.22 days (7.22 ± 9.26; p = 0.001). Capillary pCO2 decreased by 0.02 kPa (0.02 ± 0.52; p = 0.85). The CCQ score decreased by 0.06 (0.06 ± 0.96; p = 0.76). The MRC dyspnea score decreased by 0.04 (0.04 ± 0.80; p = 0.81). The HADS anxiety score decreased by 0.63 (0.63 ± 3.12; p = 0.31). And finally, the HADS depression score decreased by 0.32 (0.32 ± 3.48; p = 0.64). There was a significant difference between the normocapnic (capillary pCO2 < 6.0 kPa) group and the hypercapnic group in terms of change in the CCQ score (-0.24 ± 0.55 and 0.49 ± 1.32 decrease, respectively, p = 0.05) and the HADS depression score (-0.76 ± 1.86 and 2.20 ± 4.75 decrease, respectively, p = 0.03) after 1 year of HFNC treatment. Conclusions: One-year-long HFNC therapy significantly decreased the COPD exacerbations rate, hospital admissions, and in-hospital days in severe COPD patients with a high disease burden and frequent COPD exacerbations irrespective of them having hypercapnia and with the HRQoL measures only improving in the hypercapnic group. This may imply that severe COPD patients with a high disease burden and frequent COPD exacerbations, irrespective being hypercapnic, are candidates for treatment with home HFNC oxygen therapy.

High-Flow Nasal Oxygen in Patients with Acute Hypercapnic Respiratory Failure: A Narrative Review of the Physiological Rationale and Clinical Evidence

Acute hypercapnic respiratory failure is a life-threatening condition caused by alveolar hypoventilation. It is mostly caused by an acute exacerbation of chronic obstructive pulmonary disease or conditions yielding muscle dysfunction. Noninvasive ventilation through a facemask is the cornerstone first-line strategy to support hypercapnic patients with acidemia, and current guidelines strongly recommend this intervention to improve survival and long-term clinical outcomes. Because of its benefits related to carbon dioxide washout from the upper airways and the enhanced comfort, high-flow nasal oxygen has been proposed as a respiratory support strategy in patients with hypercapnic respiratory failure, both as an alternative to and in combination with noninvasive ventilation. When compared to noninvasive ventilation as a first-line intervention, high-flow nasal oxygen shows a higher rate of failure. Hence, if not contraindicated, the use of noninvasive ventilation should be preferred. After the resolution of acidemia with noninvasive ventilation, high-flow nasal oxygen showed promising physiological effects compared to conventional oxygen. During weaning from mechanical ventilation in patients with or at risk of developing hypercapnia, high-flow nasal oxygen showed encouraging results, especially when applied alternating with sessions of noninvasive ventilation. Optimal settings of high-flow nasal oxygen in hypercapnic patients include the use of a smaller-size cannula, flows ranging between 30 and 40 L/min, and FiO2 adjusted to obtain SpO2 between 88% and 92%. Specific interfaces, such as asymmetric cannulas, may further enhance the benefits of a high flow in terms of carbon dioxide clearance. In this narrative review, we provide an updated overview of the physiological rationale and clinical evidence concerning the use of high-flow nasal oxygen in patients with acute hypercapnic respiratory failure.

[High-flow nasal oxygen therapy and hypercapnic acute respiratory failure]

Humidified high-flow nasal oxygen therapy (HFNO) has, in recent years, come to assume a key role in the management of hypoxemic acute respiratory failure (ARF). While non-invasive ventilation (NIV) currently represents the first-line ventilatory strategy in patients exhibiting hypercapnic ARF, the operating principles and physiological effects of HFNO could be interesting and useful in the initial management of hypercapnic ARF and/or after extubation, particularly in acute exacerbations of chronic obstructive pulmonary disease. Under these conditions, HFNO could be used either alone continuously or in combination with NIV during breaks in spontaneous breathing, depending on the severity and etiology of the underlying hypercapnic ARF.

Nasal High-Flow Oxygen Therapy in Chronic Respiratory Failure for Homecare Applications-A Feasibility Study

Background: While high-flow nasal cannulas (HFNCs) represent the standard of care in the intensive care unit for patients with severe hypoxemia, its use in homecare settings is uncommon despite its potential. The potential benefits and challenges of the high-flow nasal cannula (HFNC) in homecare settings compared to standard long-term oxygen via nasal low-flow therapy are unclear. Methods: We conducted a prospective monocentric feasibility study at the Department of Respiratory Medicine, University Hospital, Goethe University Frankfurt, Germany. Patients with interstitial lung disease or severe bronchiectasis (including cystic fibrosis) were enrolled into the study. The HFNC was introduced during hospitalization. The patients' compliance with home use advice and arterial blood gas results were evaluated at a 4-6-week follow-up. Results: A total of 12 patients were analyzed. HFNC initiation did not result in a significant improvement of the pO2/fiO2 (p/f) ratio. Only 8 out of 12 (66.6%) patients used the HFNC at home after the initial in-hospital initiation. Only 7 of the total 12 patients were using the therapy at a follow-up 3-6 weeks after HFNC onset. Two patients died during the observation, resulting in a surveillance mortality rate of 16.7%. Conclusions: The feasibility data showed low adherence to the HFNC at home. The lack of any positive effect on the p/f ratio may be due to low airflow rates and overall mild hypoxemia compared to patients with severe respiratory failure in the ICU.

Effectiveness, Adherence and Safety of Home High Flow Nasal Cannula in Chronic Respiratory Disease and Respiratory Insufficiency: A Systematic Review

INTRODUCTION

The effectiveness of home high flow nasal cannula (HFNC) for the treatment of chronic respiratory failure in patients with chronic respiratory diseases (CRDs) has not been summarized. We aimed to conduct a systematic review of the effectiveness, adherence, and safety of HFNC in the long-term treatment of patients with chronic respiratory diseases and respiratory failure.

METHODS

A systematic review was conducted. PubMed, Web of science, and SCOPUS were search up to August 2023. Long-term HFNC studies (≥4 weeks) reporting dyspnea; exacerbations, hospitalizations; peripheral oxygen saturation (SpO2), comfort; patient experience, health-related quality of life or partial pressure of carbon dioxide (paCO2) were included.

RESULTS

Thirteen articles (701 patients) based on 10 studies were selected: randomized control trials (n=3), randomized crossover trials (n=2), crossover (n=3) and retrospective (n=2) studies. COPD (n=6), bronchiectasis (n=2), COPD/bronchiectasis (n=1) and ILD (n=1) were the underlined CRDs. HFNC reduced exacerbations when compared to usual care/home respiratory therapies (n=6). Quality of life outcomes were also in favor of HFNC in patients with COPD and bronchiectasis (n=6). HFNC had significant effects on hospitalizations, paCO2, and lung function. Adherence ranged from 5.2 to 8.6h/day (n=5). Three studies reported no events, 3 non-serious events and 2 no differences compared with other home respiratory therapies.

CONCLUSIONS

HFNC seems more effective than usual care or other home respiratory therapies in reducing exacerbations and improving quality of life in patients with COPD and bronchiectasis, while presenting good adherence and being safe. Its apparently superior effectiveness needs to be better studied in future real-world pragmatic trials.

Effects of high-flow nasal cannula oxygen therapy in bronchiectasis and hypercapnia: a retrospective observational study

BACKGROUND

The effectiveness of high-flow nasal cannula (HFNC) therapy in patients with bronchiectasis experiencing hypercapnia remains unclear. Our aim was to retrospectively analyze the short-term outcomes of HFNC therapy in such patients, and to further explore the predictors of HFNC treatment failure in this particular patient population.

METHODS

A retrospective review was conducted on patients with bronchiectasis who received HFNC (n = 70) for hypercapnia (arterial partial pressure of carbon dioxide, PaCO2 ≥ 45 mmHg) between September 2019 and September 2023.

RESULTS

In the study population, 30% of patients presented with acidemia (arterial pH < 7.35) at baseline. Within 24 h of HFNC treatment, there was a significant reduction in PaCO2 levels by a mean of 4.0 ± 12.7 mmHg (95% CI -7.0 to -1.0 mmHg). Concurrently, arterial pH showed a statistically significant increase with a mean change of 0.03 ± 0.06 (95% CI 0.01 to 0.04). The overall hospital mortality rate in our study was 17.5%. The median length of hospital stay was 11.0 days (interquartile range [IQR] 8.0 to 16.0 days). Sub-analysis revealed no statistically significant differences in hospital mortality (19.0% vs. 20.4%, p = 0.896), length of hospital stay (median 14.0 days [IQR 9.0 to 18.0 days] vs. 10.0 days [IQR 7.0 to 16.0 days], p = 0.117) and duration of HFNC application (median 5.0 days [IQR 2.0 to 8.5 days] vs. 6.0 days [IQR 4.9 to 9.5 days], p = 0.076) between the acidemia group and the non-acidemia group (arterial pH ≥ 7.35). However, more patients in the non-acidemia group had do-not-intubate orders. The overall treatment failure rate for HFNC was 28.6%. Logistic regression analysis identified the APACHE II score (OR 1.24 per point) as the independent predictor of HFNC failure.

CONCLUSIONS

In patients with bronchiectasis and hypercapnia, HFNC as an initial respiratory support can effectively reduce PaCO2 level within 24 h of treatment. A high APACHE II score has emerged as a prognostic indicator for HFNC treatment failure. These observations highlight randomized controlled trials to meticulously evaluate the efficacy of HFNC in this specific population.

Water Sorption and Structural Properties of Human Airway Mucus in Health and Muco-Obstructive Diseases

Muco-obstructive diseases change airway mucus properties, impairing mucociliary transport and increasing the likelihood of infections. To investigate the sorption properties and nanostructures of mucus in health and disease, we investigated mucus samples from patients and cell cultures (cc) from healthy, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF) airways. Atomic force microscopy (AFM) revealed mucin monomers with typical barbell structures, where the globule to spacer volume ratio was the highest for CF mucin. Accordingly, synchrotron small-angle X-ray scattering (SAXS) revealed more pronounced scattering from CF mucin globules and suggested shorter carbohydrate side chains in CF mucin and longer side chains in COPD mucin. Quartz crystal microbalance with dissipation (QCM-D) analysis presented water sorption isotherms of the three types of human airway mucus, where, at high relative humidity, COPD mucus had the highest water content compared to cc-CF and healthy airway mucus (HAM). The higher hydration of the COPD mucus is consistent with the observation of longer side chains of the COPD mucins. At low humidity, no dehydration-induced glass transition was observed in healthy and diseased mucus, suggesting mucus remained in a rubbery state. However, in dialyzed cc-HAM, a sorption-desorption hysteresis (typically observed in the glassy state) appeared, suggesting that small molecules present in mucus suppress the glass transition.

Dyspnoea relief as an inherent benefit of high flow nasal cannula therapy: A laboratory randomized trial in healthy humans

BACKGROUND AND OBJECTIVE

Persistent dyspnoea is a public health issue for which the therapeutic arsenal is limited. This study tested high-flow nasal cannula therapy (HFNT) as a means to alleviate experimental dyspnoea.

METHODS

Thirty-two healthy subjects underwent an experimental dyspnoea induced by thoracoabdominal elastic loading. HFNT was administered with alternately FiO2 of 100% (HFNT100) or 21% (HFNT21). The sensory (S-VAS) and affective (A-VAS) components of dyspnoea, transcutaneous CO2 pressure (PtcCO2 ), pulse-oximetry oxygen saturation (SpO2 ), heart rate, respiratory rate and skin galvanometry were monitored continuously. Three experimental sessions of 8 min were conducted: the first session consisted in familiarization with the experimental dyspnoea and the next two sessions tested the effects of HFNT100 and HFNT21 alternatively in a randomized order.

RESULTS

HFNT21 and HFNT100 significantly reduced dyspnoea, respectively of ∆A-VAS = 0.80 cm [-0.02-1.5]; p = 0.007 and ∆A-VAS = 1.00 cm [0.08-1.75]; p < 0.0001; ∆S-VAS = 0.70 cm [-0.15-1.98]), p < 0.0001 and ∆S-VAS = 0.70 cm [0.08-1.95]), p = 0.0002) with no significant difference between HFNT21 and HFNT100. HFNT did not significantly alter the respiratory rate or the heart rate, reduced PtcCO2 only on room air and GSR under both experimental conditions.

CONCLUSION

HFNT was associated with a statistically significant reduction in the intensity of the sensory and affective components of dyspnoea, independent of oxygen addition. This relief of laboratory dyspnoea could result from a reduction of afferent-reafferent mismatch.

High-Flow Nasal Cannula Oxygen Therapy in the Management of Respiratory Failure: A Review

High-flow nasal cannula (HFNC) oxygen therapy is gaining traction globally as a treatment for respiratory failure. There are several physiological benefits, and there is a growing body of evidence showing improved quality of life and patient comfort with HFNC, both in acute and home settings. Due to the increased burden of long-term respiratory conditions such as chronic obstructive pulmonary disease (COPD) on healthcare systems worldwide, the role of ward-based and post-discharge interventions in the prevention of hospital readmissions is an area of increasing interest. In this narrative review, we outline the physiological effects of HFNC and assess its applications in both the hospital and home settings for acute and chronic respiratory failure. We also consider the evidence of non-invasive ventilation (NIV) versus HFNC in the hospital setting and the application of HFNC at home in stable hypercapnic respiratory failure to improve the quality of life and prevent readmissions. We also look at applications of HFNC in specific circumstances, such as the perioperative period, emergency department, and acute (mainly critical care) setting including in immunocompromised patients and palliative care.

High-flow nasal cannula may prolong the length of hospital stay in patients with hypercapnic acute COPD exacerbation

BACKGROUND

High-flow nasal cannula (HFNC) is increasingly used in patients with acute exacerbation of COPD (AECOPD). We aimed to confirm whether the baseline bicarbonate is an independent predictor of outcomes in patients with hypercapnic AECOPD receiving HFNC.

METHODS

This was a secondary analysis of a multicentre randomised trial that enrolled 330 patients with non-acidotic hypercapnic AECOPD supported by HFNC or conventional oxygen treatment (COT). We compared the length of stay (LOS) in hospital and the rate of non-invasive positive pressure ventilation (NPPV) use according to baseline bicarbonate levels using the log-rank test or Cox proportional hazard model.

RESULTS

In the high bicarbonate subgroup (n = 165, bicarbonate 35.0[33.3-37.9] mmol/L, partial pressure of arterial carbon dioxide [PaCO2] 56.8[52.0-62.8] mmHg), patients supported by HFNC had a remarkably prolonged LOS in hospital when compared to COT (HR 1.59[1.16-2.17], p = 0.004), whereas patients in the low bicarbonate subgroup (n = 165, bicarbonate 28.8[27.0-30.4] mmol/L, PaCO2 48.0[46.0-50.0] mmHg) had a comparable LOS in hospital regardless of respiratory support modalities. The rate of NPPV use in patients with high baseline bicarbonate level was significantly higher than that in patients with low baseline bicarbonate level (19.4 % vs. 3.0 %, p < 0.0001). Patients with high bicarbonate level in HFNC group had a lower rate of NPPV use compared to COT group (15.4 % vs. 23.0 %, p = 0.217).

CONCLUSIONS

Among patients with non-acidotic hypercapnic AECOPD with high baseline bicarbonate level, HFNC is significantly associated with a prolonged LOS in hospital, which may be due to the reduced escalation of NPPV treatment.

TRIAL REGISTRATION

clinicaltrials.gov (NCT03003559).

Efficacy of high-flow nasal cannula in patients with acute heart failure: a systematic review and meta-analysis

BACKGROUND

Acute heart failure (AHF) is often associated with diffuse insufficiency and arterial hypoxemia, requiring respiratory support for rapid and effective correction. We aimed to compare the effects of high-flow nasal cannula(HFNC) with those of conventional oxygen therapy(COT) or non-invasive ventilation(NIV) on the prognosis of patients with AHF.

METHODS

We performed the search using PubMed, Embase, Web of Science, MEDLINE, the Cochrane Library, CNKI, Wanfang, and VIP databases from the inception to August 31, 2023 for relevant studies in English and Chinese. We included controlled studies comparing HFNC with COT or NIV in patients with AHF. Primary outcomes included the intubation rate, respiratory rate (RR), heart rate (HR), and oxygenation status.

RESULTS

From the 1288 original papers identified, 16 studies met the inclusion criteria, and 1333 patients were included. Compared with COT, HFNC reduced the intubation rate (odds ratio [OR]: 0.29, 95% CI: 0.14-0.58, P = 0.0005), RR (standardized mean difference [SMD]: -0.73 95% CI: -0.99 - -0.47, P < 0.00001) and HR (SMD: -0.88, 95% CI: -1.07 - -0.69, P < 0.00001), and hospital stay (SMD: -0.94, 95% CI: -1.76 - -0.12, P = 0.03), and increase arterial oxygen partial pressure (PaO2), (SMD: 0.88, 95% CI: 0.70-1.06, P < 0.00001) and oxygen saturation (SpO2 [%], SMD: 0.70, 95% CI: 0.34-1.06, P = 0.0001).

CONCLUSIONS

There were no significant differences in intubation rate, RR, HR, arterial blood gas parameters, and dyspnea scores between the HFNC and NIV groups. Compared with COT, HFNC effectively reduced the intubation rate and provided greater clinical benefits to patients with AHF. However, there was no significant difference in the clinical prognosis of patients with AHF between the HFNC and NIV groups.

TRIAL REGISTRATION

PROSPERO (identifier: CRD42022365611).

High flow nasal cannula versus noninvasive ventilation in the treatment of acute hypercapnic respiratory failure: A systematic review and meta-analysis

Chronic obstructive pulmonary disease can lead to acute hypercapnic respiratory failure (AHRF), often treated using noninvasive ventilation (NIV). Emerging research suggests the potential utility of high flow nasal cannula (HFNC) for AHRF. This systematic review and meta-analysis aimed to determine the effect of HFNC versus NIV on AHRF management. A search of electronic databases (CINAHL, MEDLINE, and Academic Search Complete), web sources, and trial registries was last conducted on 9 February 2023. Quality and risk of bias assessments were conducted. Meta-analyses were used to synthesise data. Seven randomised controlled trials were included. No statistically significant differences between HFNC and NIV were found within the following outcomes of interest: (i) correction of pCO2: standardised mean difference (SMD) = -0.16, 95% confidence interval (CI) (-0.34 to 0.02), p = 0.08; (ii) correction of pH: SMD = -0.05, 95% CI (-0.25 to 0.14), p = 0.59; (iii) correction of pO2: SMD = -0.15, 95% CI (-0.40 to 0.09), p = 0.22; (iv) intubation rates: risk ratio (RR) = 0.87, 95% CI (0.41 to 1.82), p = 0.71; (v) mortality rates: RR = 0.85, 95% CI (0.47 to 1.56), p = 0.61; and (vi) treatment switch: RR = 1.30, 95% CI (0.43 to 3.94), p = 0.64. More controlled trials with large sample sizes are required to investigate the management of AHRF of various aetiologies. HFNC may be used as a final exhaustive measure for COPD-related AHRF where NIV is not tolerated, and when it is not clinically indicated to extend to endotracheal intubation.

Comparison of High-Flow Nasal Cannula with Conventional Oxygen Therapy in Patients with Hypercapnic Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis

Purpose

This study aimed to evaluate the clinical outcomes of high-flow nasal cannula (HFNC) compared with conventional oxygen therapy (COT) in patients with hypercapnic chronic obstructive pulmonary disease (COPD), including arterial partial pressure of carbon dioxide (PaCO₂), arterial partial pressure of oxygen (PaO₂), respiratory rate (RR), treatment failure, exacerbation rates, adverse events and comfort evaluation.

Patients and Methods

PubMed, EMBASE and the Cochrane Library were retrieved from inception to September 30, 2022. Eligible trials were randomized controlled trials and crossover studies comparing HFNC and COT in hypercapnic COPD patients. Continuous variables were reported as mean and standard derivation and calculated by weighted mean differences (MD), while dichotomous variables were shown as frequency and proportion and calculated by odds ratio (OR), with the 95% confidence intervals (Cl). Statistical analysis was performed using RevMan 5.4 software.

Results

Eight studies were included, five with acute hypercapnia and three with chronic hypercapnia. In acute hypercapnic COPD, short-term HFNC reduced PaCO₂ (MD -1.55, 95% CI: -2.85 to -0.25, I² = 0%, p <0.05) and treatment failure (OR 0.54, 95% CI: 0.33 to 0.88, I² = 0%, p<0.05), but there were no significant differences in PaO₂ (MD -0.36, 95% CI: -2.23 to 1.52, I² = 45%, p=0.71) and RR (MD -1.07, 95% CI: -2.44 to 0.29, I² = 72%, p=0.12). In chronic hypercapnic COPD, HFNC may reduce COPD exacerbation rates, but there was no advantage in improving PaCO₂ (MD -1.21, 95% CI: -3.81 to 1.39, I² = 0%, p=0.36) and PaO₂ (MD 2.81, 95% CI: -1.39 to 7.02, I² = 0%, p=0.19).

Conclusion

Compared with COT, short-term HFNC reduced PaCO₂ and the need for escalating respiratory support in acute hypercapnic COPD, whereas long-term HFNC reduced COPD exacerbations rates in chronic hypercapnia. HFNC has great potential for treating hypercapnic COPD.

High-flow nasal cannula therapy with sequential noninvasive ventilation versus noninvasive ventilation alone as the initial ventilatory strategy in acute COPD exacerbations: study protocol for a randomized controlled trial

BACKGROUND

Noninvasive ventilation (NIV) is the recommended mode of ventilation used in acute respiratory failure secondary to an acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Recent data has shown that high-flow nasal cannula (HFNC) treatment can be an alternative for patients with hypercapnic respiratory failure. The purpose of this study is to evaluate HFNC with sequential NIV versus NIV alone as the initial ventilatory strategy in AECOPD.

METHODS

This investigator-initiated, unblinded, single center, randomized controlled trial will be conducted in the emergency department, emergency intensive care unit, or respiratory intensive care unit of a tertiary-care urban teaching hospital. A total of 66 patients will be enrolled and randomized into the intervention group (HFNC with sequential NIV) or the control group (NIV group). The primary endpoint will be the mean difference in PaCO2 from baseline to 24 h after randomization. Secondary endpoints include the mean difference in PaCO2 from baseline to 6, 12, and 18 h, as well as the dyspnea score, overall discomfort score, rate of treatment failure, respiratory rate, rate of endotracheal intubation, length of hospital stay, and mortality.

DISCUSSION

Taking the advantages of both HFNC and NIV on AECOPD patients into account, we designed this clinical trial to investigate the combination of these ventilatory strategies. This trial will help us understand how HFNC with sequential NIV compares to NIV alone in treating AECOPD patients.

TRIAL REGISTRATION

ChiCTR2100054809.

Current Considerations in Emergency Airway Management

Purpose of Review

Emergency airway management is populated by many new concepts, evolving equipment, and contemporary strategies for optimal procedural success. This review aims to discuss various topics within these realms and to continue the ongoing conversation regarding improvement of emergency airway management.

Recent Findings

Various literature, opinion pieces, podcasts, and trials have prompted renewed interest in the field of emergency airway management. Though common threads can be found, there is significant debate on optimal practice. Accompanying these conversations is continuous production of new equipment which can be beneficial to providers. However, this ongoing accumulation of material, data, and pathways can create challenges in remaining up to date. Rather than a comprehensive review of current literature and discussion of research findings, this article aims to discuss selected and impactful concepts in real time context and provide potentially immediate additions to emergency airway manager practice.

Summary

As emergency airway management evolves, it remains a significant task to maintain up to date on current trends, data, and new equipment. This article aims to discuss several of these items in a digestible fashion and provide immediate impact for emergency airway providers.

Inpatient Management of the Acutely Decompensating Lung Transplant Candidate

Lung allocation in the US changed nearly 15 years ago from time accrued on the waiting list to disease severity and likelihood of posttransplant survival, represented by the lung allocation score (LAS). Notably, the risk of death within a year plays a stronger role on the score calculation than posttransplant survival. While this change was associated with the intended decrease in waitlist mortality (most recently reported at 14.6%), it was predictable that transplant teams would have to care for increasingly older and complex candidates and recipients. This urgency-based allocation also led centers to routinely consider transplanting patients with higher acuity, often hospitalized and, not infrequently, in the intensive care unit (ICU). According to the Scientific Registry for Transplant Recipients, from 2009 to 2019, the proportion of lung recipients hospitalized and those admitted to the ICU at the time of transplant increased from 18.9% to 26.8% and from 9.2% to 16.5%, respectively..

Current Practice of High Flow through Nasal Cannula in Exacerbated COPD Patients

Acute Exacerbation of Chronic Obstructive Pulmonary Disease is a form of severe Acute Respiratory Failure (ARF) requiring Conventional Oxygen Therapy (COT) in the case of absence of acidosis or the application of Non-Invasive Ventilation (NIV) in case of respiratory acidosis. In the last decade, High Flow through Nasal Cannula (HFNC) has been increasingly used, mainly in patients with hypoxemic ARF. However, some studies were also published in AECOPD patients, and some evidence emerged. In this review, after describing the mechanism underlying potential clinical benefits, we analyzed the possible clinical application of HFNC to AECOPD patients. In the case of respiratory acidosis, the gold-standard treatment remains NIV, supported by strong evidence in favor. However, HFNC may be considered as an alternative to NIV if the latter fails for intolerance. HFNC should also be considered and preferred to COT at NIV breaks and weaning. Finally, HFNC should also be preferred to COT as first-line oxygen treatment in AECOPD patients without respiratory acidosis.

[Translated article] Spanish COPD Guidelines (GesEPOC) 2021 Update. Diagnosis and Treatment of COPD Exacerbation Syndrome

This article details the GesEPOC 2021 recommendations on the diagnosis and treatment of COPD exacerbation syndrome (CES). The guidelines propose a definition-based syndromic approach, a new classification of severity, and the recognition of different treatable traits (TT), representing a new step toward personalized medicine. The evidence is evaluated using GRADE methodology, with the incorporation of 6 new PICO questions. The diagnostic process comprises four stages: 1) establish a diagnosis of CES, 2) assess the severity of the episode, 3) identify the trigger, and 4) address TTs. This diagnostic process differentiates an outpatient approach, that recommends the inclusion of a basic battery of tests, from a more comprehensive hospital approach, that includes the study of different biomarkers and imaging tests. Bronchodilator treatment for immediate relief of symptoms is considered essential for all patients, while the use of antibiotics, systemic corticosteroids, oxygen therapy, and assisted ventilation and the treatment of comorbidities will vary depending on severity and possible TTs. The use of antibiotics will be indicated particularly if sputum color changes, when ventilatory assistance is required, in cases involving pneumonia, and in patients with elevated C-reactive protein (≥ 20 mg/L). Systemic corticosteroids are recommended in CES that requires admission and are suggested in moderate CES. These drugs are more effective in patients with blood eosinophil counts ≥ 300 cells/mm3. Acute-phase non-invasive mechanical ventilation is specified primarily for patients with CES who develop respiratory acidosis despite initial treatment.

Nasal high flow oxygen therapy during acute admissions or periods of worsening symptoms

PURPOSE OF REVIEW

Nasal high flow therapy (NHF) is increasingly used in acute care settings. In this review, we consider recent advances in the utilization of NHF in chronic obstructive pulmonary disease (COPD), terminal cancer and symptom management. Considerations around NHF use during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic are also discussed.

RECENT FINDINGS

NHF enables humidification and high flows to be provided together with titrated, supplemental oxygen therapy. Compared to conventional oxygen therapy, NHF improves respiratory physiology by reducing workload, enhancing muco-ciliary clearance and improving dead space washout. Some studies suggest that early use of NHF in people being cared for in the emergency department leads to lower rates of invasive ventilation and noninvasive ventilation. There is also emerging evidence for NHF use in people with COPD and chronic respiratory failure, and in palliative care. NHF is comfortable, well-tolerated and safe for use in the management of breathlessness in people with cancer. NHF can be delivered by face mask to patients with SARS-CoV-2 infection, to ease the burden on critical care resources.

SUMMARY

The evidence base for NHF is rapidly growing and offers promise in relieving troublesome symptoms and for people receiving palliative care.

ERS Clinical Practice Guidelines: High-flow nasal cannula in acute respiratory failure

BACKGROUND

High-flow nasal cannula (HFNC) has become a frequently used non-invasive form of respiratory support in acute settings, however evidence supporting its use has only recently emerged. These guidelines provide evidence-based recommendations for the use of HFNC alongside other noninvasive forms of respiratory support in adults with acute respiratory failure (ARF).

MATERIALS AND METHODOLOGY

The European Respiratory Society Task Force panel included expert clinicians and methodologists in pulmonology and intensive care medicine. The Task Force used the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) methods to summarize evidence and develop clinical recommendations for the use of HFNC alongside conventional oxygen therapy (COT) and non-invasive ventilation (NIV) for the management of adults in acute settings with ARF.

RESULTS

The Task Force developed 8 conditional recommendations, suggesting using: 1) HFNC over COT in hypoxemic ARF, 2) HFNC over NIV in hypoxemic ARF, 3)HFNC over COT during breaks from NIV, 4) either HFNC or COT in post-operative patients at low risk of pulmonary complications, 5) either HFNC or NIV in post-operative patients at high risk of pulmonary complications, 6) HFNC over COT in non-surgical patients at low risk of extubation failure, 7) NIV over HFNC for patients at high risk of extubation failure unless there are relative or absolute contraindications to NIV, 8) trialling NIV prior to use of HFNC in patients with chronic obstructive pulmonary disease (COPD) and hypercapnic ARF.

CONCLUSIONS

HFNC is a valuable intervention in adults with ARF. These conditional recommendations can assist clinicians in choosing the most appropriate form of non-invasive respiratory support to provide to patients in different acute settings.

The efficacy and safety of high-flow nasal cannula therapy in patients with COPD and type II respiratory failure: a meta-analysis and systematic review

Background

High-flow nasal cannula (HFNC) and noninvasive ventilation (NIV) have been used for the treatment of COPD and respiratory failure in clinical settings. We aimed to evaluate the efficacy and safety of HFNC therapy in patients with COPD and type II respiratory failure, to provide evidence to the clinical COPD management.

Methods

We searched Cochrane et al. databases up to Dec 31, 2020 for randomized controlled trials (RCTs) on the use of HFNC therapy in patients with COPD and type II respiratory failure. Two researchers independently screened the literature according to the inclusion and exclusion criteria, and evaluated the quality of the literature and extracted data. We used Revman5.3 software for statistical analysis of collected data.

Results

A total of 6 RCTs involving 525 COPD and type II respiratory failure patients. Meta-analyses indicated that compared with NIV, HFNC could significantly reduce PaCO₂ level (MD = − 2.64, 95% CI (− 3.12 to − 2.15)), length of hospital stay ((MD = – 1.19, 95 CI (− 2.23 to − 0.05)), the incidence of nasal facial skin breakdown ((OR = 0.11, 95% CI (0.03–0.41)). And there were no significant differences between the two groups in PaO₂ ((MD = 2.92, 95% CI (− 0.05 to 5.90)), incidence of tracheal intubation ((OR = 0.74, 95% CI (0.34–1.59)) and mortality (OR = 0.77, 95% CI (0.28–2.11)).

Conclusions

HFNC is more advantageous over NIV in the treatment of COPD and type II respiratory failure. Future studies with larger sample size and strict design are needed to further elucidate the role of HFNC in COPD and respiratory failure.

Effects of different high-flow nasal cannula flow rates on swallowing function

BACKGROUND

High-flow nasal cannula therapy is used as a noninvasive treatment for people with acute respiratory disease. The aim of this study was to assess the impact of high-flow nasal cannula different flow rates on different characteristics of swallowing in healthy volunteers.

METHODS

A prospective cohort study where healthy adult volunteers were subject to high-flow nasal cannula at different flow rates (0, 10, 20, 30, 40, and 50 L/min, in random order). The 30-mL water swallow test, repetitive saliva swallowing test, and 0-100 mm visual analog scale assessed aspiration, swallow frequency and effort, respectively.

FINDINGS

Thirty subjects (mean age 30 years) were enrolled. Nine subjects (30.0%) choked at 10, 40 and 50 L/min during the 30-mL water swallow test (p < 0.05). Swallowing effort was increased during flow rates ≥20 compared to 10 L/min (p < 0.05). Flow rates ≥20 L/min resulted in lower number of swallows during the repetitive saliva swallowing test compared to 0 and 10 L/min (p < 0.05).

INTERPRETATION

High-flow nasal cannula flow rates above 40 L/min associated with choking (increased risk of aspiration), and was associated with decreased swallowing function in healthy volunteers. It may be important to assess swallowing function in patients with various clinical conditions and treated with high-flow nasal cannula, especially those at risk of aspiration pneumonia.

Oxygenation strategies during flexible bronchoscopy: a review of the literature

During flexible fiberoptic bronchoscopy (FOB) the arterial partial pressure of oxygen can drop, increasing the risk for respiratory failure. To avoid desaturation episodes during the procedure several oxygenation strategies have been proposed, including conventional oxygen therapy (COT), high flow nasal cannula (HFNC), continuous positive airway pressure (CPAP) and non-invasive ventilation (NIV). By a review of the current literature, we merely describe the clinical practice of oxygen therapies during FOB. We also conducted a pooled data analysis with respect to oxygenation outcomes, comparing HFNC with COT and NIV, separately. COT showed its benefits in patients undergoing FOB for broncho-alveolar lavage (BAL) or brushing for cytology, in those with peripheral arterial oxyhemoglobin saturation < 93% prior to the procedure or affected by obstructive disorder. HFNC is preferable over COT in patients with mild to moderate acute respiratory failure (ARF) undergoing FOB, by improving oxygen saturation and decreasing the episodes of desaturation. On the opposite, CPAP and NIV guarantee improved oxygenation outcomes as compared to HFNC, and they should be preferred in patients with more severe hypoxemic ARF during FOB.

An Integrated Model including the ROX Index to Predict the Success of High-Flow Nasal Cannula Use after Planned Extubation: A Retrospective Observational Cohort Study

High-flow nasal cannula (HFNC) therapy is commonly used to prevent reintubation after planned extubation. In clinical practice, there are no appropriate tools to evaluate whether HFNC therapy was successful or failed after planned extubation. In this retrospective observational study, we investigated whether the use of the ROX index was appropriate to differentiate between HFNC success and failure within 72 h after extubation and to develop an integrated model including the ROX index to improve the prediction of HFNC success in patients receiving HFNC therapy after planned extubation. Of 276 patients, 50 patients (18.1%) were reintubated within 72 h of extubation. ROX index values of >8.7 at 2 h, >8.7 at 6 h, and >10.4 at 12 h after HFNC therapy were all meaningful predictors of HFNC success in extubated patients. In addition, the integrated model including the ROX index had a better predictive capability for HFNC success than the ROX index alone. In conclusion, the ROX index at 2, 6, and 12 h could be applied to extubated patients to predict HFNC success after planned extubation. To improve its predictive power, we should also consider an integrated model consisting of the ROX index, sex, body mass index, and the total duration of ventilator care.

Impact of the COVID-19 pandemic on the management of chronic noninfectious respiratory diseases

Introduction: The COVID-19 pandemic has challenged health care across the world, not just by the severity of the disease and the high mortality rate but also by the consequences on the management of the patients with chronic diseases.Areas covered: This review summarizes the most up-to-date published data regarding the impact of COVID-19 on the management and outcomes of patients with chronic noninfectious respiratory illnesses including obstructive sleep apnea, asthma, chronic obstructive pulmonary disease, bronchiectasis, interstitial and pulmonary vascular diseases, and lung cancer.Expert opinion: Most of chronic respiratory diseases (except asthma and cystic fibrosis) are associated with more severe COVID-19 and poor outcomes but the mechanisms involved are not yet identified. The therapeutic management of the patients with chronic respiratory diseases and COVID-19 is similar to the other patients but the post-recovery course could be worse in this population and followed by the development of pulmonary fibrosis, bronchiectasis, and pulmonary hypertension. The pandemic highly impacted our usual medical activities by limiting the access to several diagnosis procedures, the necessity to develop new methods for the monitoring of the disease and adapt the therapeutic strategies. The long-term consequences of all these changes are still unknown.

Portable High-Flow Nasal Oxygen during Walking in Patients with Severe Chronic Obstructive Pulmonary Disease: A Randomized Controlled Trial

BACKGROUND

High-flow nasal oxygen (HFNO) improves exercise capacity, oxygen saturation, and symptoms in patients with chronic obstructive pulmonary disease (COPD). Due to the need of electricity supply, HFNO has not been applied during free ambulation.

OBJECTIVE

We evaluated whether HFNO delivered during walking by a battery-supplied portable device was more effective than usual portable oxygen in improving exercise capacity in patients with COPD and severe exercise limitation. The effects on 6-min walking tests (6MWTs) were the primary outcome.

METHODS

After a baseline 6MWT, 20 stable patients requiring an oxygen inspiratory fraction (FiO2) <0.60 during exercise, randomly underwent 2 6MWT carrying a rollator, under either HFNO with a portable device (HFNO test) or oxygen supplementation by a Venturi mask (Control) at isoFiO2. Walked distance, perceived dyspnea, pulse oximetry, and inspiratory capacity at end of the tests as well as patients' comfort were compared between the tests.

RESULTS

As compared to baseline, walked distance improved significantly more in HFNO than in the control test (by 61.1 ± 37.8 and 39.7 ± 43.8 m, respectively, p = 0.01). There were no significant differences between the tests in dyspnea, peripheral oxygen saturation, or inspiratory capacity, but HFNO test was appreciated as more comfortable.

CONCLUSION

In patients with COPD and severe exercise limitation, HFNO delivered by a battery-supplied portable device was more effective in improving walking distance than usual oxygen supplementation.

Effect of high-flow nasal cannula oxygen therapy in patients with chronic obstructive pulmonary disease: A meta-analysis

BACKGROUND

High-flow nasal cannula oxygen therapy reduces the arterial partial pressure of carbon dioxide and acute exacerbation but does not increase exercise capacity or decrease hospitalisation or mortality. The study aimed to test the hypothesis that in chronic obstructive pulmonary disease patients, the use of high-flow nasal cannula decreases arterial partial pressure of carbon dioxide and increases the partial pressure of oxygen and 6-min walking distance.

METHODS

PubMed, Embase and the Cochrane library were searched for eligible studies published from database inception to November 2020 (Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist). The primary outcomes were partial pressure of carbon dioxide and partial pressure of oxygen, and the secondary outcomes were transcutaneous partial pressure of carbon dioxide and 6-min walking distance.

RESULTS

Nine studies (680 patients) were included. high-flow nasal cannula did not decrease partial pressure of carbon dioxide compared with the control interventions (mean difference = -0.81, 95% confidence interval: -2.68 to 1.06, p = .395; I²  = 42.9%, p_{heterogeneity}  = .105). high-flow nasal cannula decreased partial pressure of carbon dioxide compared with long-term oxygen therapy (mean difference = -3.25, 95% confidence interval: -5.65 to -0.85, p = .008; I²  = 0%, p_{heterogeneity}   = .375); no difference was observed for the control modalities. high-flow nasal cannula resulted in better partial pressure of carbon dioxide compared with control interventions in hypoxemic patients (mean difference = -2.59, 95% confidence interval: -4.82 to -0.35, p = .023; I²  = 32.5%, p_{heterogeneity}  = .224), but not in other types of patients. high-flow nasal cannula did not increase partial pressure of oxygen compared with the control interventions (mean difference = 1.17, 95% confidence interval: -1.50 to 3.83, p = .390; I²  = 0%, p_{heterogeneity}  = .660). high-flow nasal cannula decreased transcutaneous carbon dioxide tension (transcutaneous partial pressure of carbon dioxide) compared with the control interventions (mean difference = 2.37, 95% confidence interval: 0.07-4.68, p = .044; I²  = 8.7%, p_{heterogeneity}   = .295). high-flow nasal cannula increased 6-min walking distance compared with the control interventions (mean difference = 18.22, 95% confidence interval: 0.86-,35.57, p = .040; I²  = 0%, p_{heterogeneity}  = .918). The sensitivity analyses showed that the results were robust.

CONCLUSIONS

High-flow nasal cannula did not significantly decrease partial pressure of carbon dioxide or increase partial pressure of oxygen in chronic obstructive pulmonary disease patients, which is different from the previous meta-analysis, but it decreases transcutaneous partial pressure of carbon dioxide and increased 6-min walking distance.

RELEVANCE TO CLINICAL PRACTICE

This meta-analysis shows that in patients with chronic obstructive pulmonary disease, high-flow nasal cannula improves both transcutaneous partial pressure of carbon dioxide and 6-min walking distance, suggesting the high-flow nasal cannula has benefits in the management of chronic obstructive pulmonary disease. Considering that the literature suggests no impact of high-flow nasal cannula on hospitalisation and mortality, the benefits of high-flow nasal cannula might be limited to the patients who survive the chronic obstructive pulmonary disease events. Still, the global impact of high-flow nasal cannula on the quality of life of patients with chronic obstructive pulmonary disease should be examined.

Non-invasive respiratory support paths in hospitalized patients with COVID-19: proposal of an algorithm

COVID-19 related Acute Respiratory Failure, may be successfully treated with Conventional Oxygen therapy, High Flow Nasal Cannula, Continuous Positive Airway Pressure or Bi-level Positive-Pressure ventilation. Despite the accumulated data in favor of the use of different Non-invasive Respiratory therapies in COVID-19 related Acute Respiratory Failure, it is not fully understood when start, escalate and de-escalate the best respiratory supportive option for the different timing of the disease. Based on the current published experience with Non-invasive Respiratory therapies in COVID-19 related Acute Respiratory Failure, we propose an algorithm in deciding when to start, when to stop and when to wean different NIRT. This strategy may help clinicians in better choosing NIRT during this second COVID-19 wave and beyond.

High flow nasal oxygen for acute type two respiratory failure: a systematic review

Background: Acute type two respiratory failure (AT2RF) is characterized by high carbon dioxide levels (PaCO 2 >6kPa). Non-invasive ventilation (NIV), the current standard of care, has a high failure rate. High flow nasal therapy (HFNT) has potential additional benefits such as CO 2 clearance, the ability to communicate and comfort. The primary aim of this systematic review is to determine whether HFNT in AT2RF improves 1) PaCO 2, 2) clinical and patient-centred outcomes and 3) to assess potential harms. Methods: We searched EMBASE, MEDLINE and CENTRAL  (January 1999-January 2021). Randomised controlled trials (RCTs) and cohort studies comparing HFNT with low flow nasal oxygen (LFO) or NIV were included. Two authors independently assessed studies for eligibility, data extraction and risk of bias. We used Cochrane risk of bias tool for RCTs and Ottawa-Newcastle scale for cohort studies. Results: From 727 publications reviewed, four RCTs and one cohort study (n=425) were included. In three trials of HFNT vs NIV, comparing PaCO 2 (kPa) at last follow-up time point, there was a significant reduction at four hours (1 RCT; HFNT median 6.7, IQR 5.6 - 7.7 vs NIV median 7.6, IQR 6.3 - 9.3) and no significant difference at  24-hours or five days. Comparing HFNT with LFO, there was no significant difference at 30-minutes. There was no difference in intubation or mortality. Conclusions: This review identified a small number of studies with low to very low certainty of evidence. A reduction of PaCO 2 at an early time point of four hours post-intervention was demonstrated in one small RCT. Significant limitations of the included studies were lack of adequately powered outcomes and clinically relevant time-points and small sample size. Accordingly, systematic review cannot recommend the use of HFNT as the initial management strategy for AT2RF and trials adequately powered to detect clinical and patient-relevant outcomes are urgently warranted.

Spanish COPD Guidelines (GesEPOC) 2021 Update Diagnosis and Treatment af COPD Exacerbation Syndrome

This article details the GesEPOC 2021 recommendations on the diagnosis and treatment of COPD exacerbation syndrome (CES). The guidelines propose a definition-based syndromic approach, a new classification of severity, and the recognition of different treatable traits (TT), representing a new step toward personalized medicine. The evidence is evaluated using GRADE methodology, with the incorporation of 6 new PICO questions. The diagnostic process comprises four stages: 1) establish a diagnosis of CES, 2) assess the severity of the episode, 3) identify the trigger, and 4) address TTs. This diagnostic process differentiates an outpatient approach, that recommends the inclusion of a basic battery of tests, from a more comprehensive hospital approach, that includes the study of different biomarkers and imaging tests. Bronchodilator treatment for immediate relief of symptoms is considered essential for all patients, while the use of antibiotics, systemic corticosteroids, oxygen therapy, and assisted ventilation and the treatment of comorbidities will vary depending on severity and possible TTs. The use of antibiotics will be indicated particularly if sputum color changes, when ventilatory assistance is required, in cases involving pneumonia, and in patients with elevated C-reactive protein (≥ 20 mg/L). Systemic corticosteroids are recommended in CES that requires admission and are suggested in moderate CES. These drugs are more effective in patients with blood eosinophil counts ≥ 300 cells/mm³. Acute-phase non-invasive mechanical ventilation is specified primarily for patients with CES who develop respiratory acidosis despite initial treatment.

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.

Chronic obstructive pulmonary disease exacerbation fundamentals: Diagnosis, treatment, prevention and disease impact

In chronic obstructive pulmonary disease (COPD), exacerbations (ECOPD), characterized by an acute deterioration in respiratory symptoms, are fundamental events impacting negatively upon disease progression, comorbidities, wellbeing and mortality. ECOPD also represent the largest component of the socioeconomic burden of COPD. ECOPDs are currently defined as acute worsening of respiratory symptoms that require additional therapy. Definitions that require worsening of dyspnoea and sputum volume/purulence assume that acute infections, especially respiratory viral infections, and/or exposure to pollutants are the main cause of ECOPD. But other factors may contribute to ECOPD, such as the exacerbation of other respiratory diseases and non-respiratory diseases (e.g., heart failure, thromboembolism). The complexity of worsening dyspnoea has suggested a need to improve the definition of ECOPD using objective measurements such as blood counts and C-reactive protein to improve accuracy of diagnosis and a personalized approach to management. There are three time points when we can intervene to improve outcomes: acutely, to attenuate the length and severity of an established exacerbation; in the aftermath, to prevent early recurrence and readmission, which are common, and in the long-term, establishing preventative measures that reduce the risk of future events. Acute management includes interventions such as corticosteroids or antibiotics and measures to support the respiratory system, including non-invasive ventilation (NIV). Current therapies are broad and better understanding of clinical phenotypes and biomarkers may help to establish a more tailored approach, for example in relation to antibiotic prescription. Other unmet needs include effective treatment for viruses, which commonly cause exacerbations. Preventing early recurrence and readmission to hospital is important and the benefits of interventions such as antibiotics or anti-inflammatories in this period are not established. Domiciliary NIV in those patients who are persistently hypercapnic following discharge and pulmonary rehabilitation can have a positive impact. For long-term prevention, inhaled therapy is key. Dual bronchodilators reduce exacerbation frequency but in patients with continuing exacerbations, triple therapy should be considered, especially if blood eosinophils are elevated. Other options include phosphodiesterase inhibitors and macrolide antibiotics. ECOPD are a key component of the assessment of COPD severity and future outcomes (quality of life, hospitalisations, health care resource utilization, mortality) and are a central component in pharmacological management decisions. Targeted therapies directed towards specific pathways of inflammation are being explored in exacerbation prevention, and this is a promising avenue for future research.

Physiological Effects of High-Flow Nasal Cannula Therapy and Its Use in Acute Cardiogenic Pulmonary Edema

High-flow nasal cannula (HFNC) is an open oxygen delivery system, which provides heated and humidified oxygen at a high flow (up to 60 L/min). This effect can improve mucociliary function, airway clearance, and level of comfort to the patient. It can provide controlled and adequate fraction of inspired oxygen (FiO₂) between 21% and 100%. Generation of end-expiratory pressure helps in carbon dioxide washout, reduction of anatomical dead space, and recruitment of collapsed alveoli, ultimately improving tissue oxygenation.

The use of HFNC in acute hypoxemic respiratory failure, post-extubation period, pre-intubation period, respiratory infection, and obstructive airway disease has been extensively studied, but there are very few studies regarding its use in cardiogenic pulmonary edema. This review provides the current understanding of the physiological effect of HFNC and its application in acute cardiogenic pulmonary edema (ACPE). We conducted a literature search on PubMed using appropriate terms and reviewed relevant articles published within the last 10 years. We found that initial therapy with HFNC in ACPE patients can improve oxygenation and respiratory rate. HFNC can potentially be an alternative to non-invasive positive-pressure ventilation in terms of initial oxygen therapy in patients with ACPE. There is a need for larger prospective studies to evaluate and develop guidelines to consider the use of HFNC in patients with ACPE. We also highlight the fact that if there is no improvement in arterial blood gas parameters after HFNC therapy, initiation of invasive ventilation should not be delayed.

Nasal high flow oxygen in acute respiratory failure

Thermo-humidified nasal high flow (NHF) oxygen therapy is increasingly used in the management of respiratory failure. This therapy has recently gained attention as an alternative non-invasive respiratory support in several clinical scenarios, including acute and chronic settings. NHF enhances the patient's comfort and tolerance when compared with standard oxygen by supplying a heated and humidified mixture of air and oxygen at flows up to 60L/min. It can be delivered through different devices. Although few studies have compared the clinical effects of different NHF systems, the purpose of this paper is to describe the major benefits of NHF and to provide a quick guide on how to implement this therapy in daily practice. We have also included a brief description of the most frequently used NHF systems.

Comparison of high-flow oxygenation with noninvasive ventilation in COPD exacerbation: A crossover clinical trial

OBJECTIVES

To compare the therapeutic effects of high-flow-oxygen-Therapy (HFT) and noninvasive-ventilation (NIV) for stabilizing chronic obstructive pulmonary disease during exacerbation.

METHODS

In this randomized clinical trial at Masih-Daneshvari hospital, between July 2019 and Oct 2019, 30 exacerbated-COPD-patient with PaCO₂ 64.58 ± 11.61 mm Hg, Respiratory Rate 24.43 ± 2.75, and PH 7.31 ± 0.02 were divided into two groups, N = 15. By a simple randomized allocation, patients receive either NIV or HFT for 1 hour, and following a washout period of 30 minutes, they switched to the other treatment option. Arterial Blood Gas Parameters, as well as Respiratory Rate (RR), Dyspnea Score, Heart Rate (HR), and Oxygen Saturation (SO₂ ), were compared before and after the intervention and between groups.

RESULTS

Baseline patient characteristics were similar in the two groups. Pre and post-analysis revealed that in both groups, all improved significantly. After the first period, there was no difference in all parameters between groups except for SO₂ which was significantly higher in HFT (%92.1 ± 1) than that of NIV (%89 ± 1), P = .001. Likewise, following the washout period, patients in HFT and NIV had a dyspnea score of 1.93 ± 0.7 and 2.73 ± 0.9, respectively, P = .01. No carryover-effect and was observed but the period effect was significant for some outcomes. A significant improvement in SO₂ and HR was observed by HFT according to treatment effect by combining two periods' results. During the study, no side effects were reported.

CONCLUSION

In this short-term study HFT appears feasible for patients with COPD exacerbation to reduce dyspnea score and improve respiratory distress.

High flow nasal therapy versus noninvasive ventilation as initial ventilatory strategy in COPD exacerbation: a multicenter non-inferiority randomized trial

Background

The efficacy and safety of high flow nasal therapy (HFNT) in patients with acute hypercapnic exacerbation of chronic obstructive pulmonary disease (AECOPD) are unclear. Our aim was to evaluate the short-term effect of HFNT versus NIV in patients with mild-to-moderate AECOPD, with the hypothesis that HFNT is non-inferior to NIV on CO₂ clearance after 2 h of treatment.

Methods

We performed a multicenter, non-inferiority randomized trial comparing HFNT and noninvasive ventilation (NIV) in nine centers in Italy. Patients were eligible if presented with mild-to-moderate AECOPD (arterial pH 7.25–7.35, PaCO₂ ≥ 55 mmHg before ventilator support). Primary endpoint was the mean difference of PaCO₂ from baseline to 2 h (non-inferiority margin 10 mmHg) in the per-protocol analysis. Main secondary endpoints were non-inferiority of HFNT to NIV in reducing PaCO₂ at 6 h in the per-protocol and intention-to-treat analysis and rate of treatment changes.

Results

Seventy-nine patients were analyzed (80 patients randomized). Mean differences for PaCO₂ reduction from baseline to 2 h were − 6.8 mmHg (± 8.7) in the HFNT and − 9.5 mmHg (± 8.5) in the NIV group (p = 0.404). By 6 h, 32% of patients (13 out of 40) in the HFNT group switched to NIV and one to invasive ventilation. HFNT was statistically non-inferior to NIV since the 95% confidence interval (CI) upper boundary of absolute difference in mean PaCO₂ reduction did not reach the non-inferiority margin of 10 mmHg (absolute difference 2.7 mmHg; 1-sided 95% CI 6.1; p = 0.0003). Both treatments had a significant effect on PaCO₂ reductions over time, and trends were similar between groups. Similar results were found in both per-protocol at 6 h and intention-to-treat analysis.

Conclusions

HFNT was statistically non-inferior to NIV as initial ventilatory support in decreasing PaCO₂ after 2 h of treatment in patients with mild-to-moderate AECOPD, considering a non-inferiority margin of 10 mmHg. However, 32% of patients receiving HFNT required NIV by 6 h. Further trials with superiority design should evaluate efficacy toward stronger patient-related outcomes and safety of HFNT in AECOPD.

Trial registration: The study was prospectively registered on December 12, 2017, in ClinicalTrials.gov (NCT03370666).

A narrative review on trans-nasal pulmonary aerosol delivery

The use of trans-nasal pulmonary aerosol delivery via high-flow nasal cannula (HFNC) has expanded in recent years. However, various factors influencing aerosol delivery in this setting have not been precisely defined, and no consensus has emerged regarding the optimal techniques for aerosol delivery with HFNC. Based on a comprehensive literature search, we reviewed studies that assessed trans-nasal pulmonary aerosol delivery with HFNC by in vitro experiments, and in vivo, by radiolabeled, pharmacokinetic and pharmacodynamic studies. In these investigations, the type of nebulizer employed and its placement, carrier gas, the relationship between gas flow and patient's inspiratory flow, aerosol delivery strategies (intermittent unit dose vs continuous administration by infusion pump), and open vs closed mouth breathing influenced aerosol delivery. The objective of this review was to provide rational recommendations for optimizing aerosol delivery with HFNC in various clinical settings.

Histopathological findings in a COVID-19 patient affected by ischemic gangrenous cholecystitis

BACKGROUND

Since its first documentation, a novel coronavirus (SARS-CoV-2) infection has emerged worldwide, with the consequent declaration of a pandemic disease (COVID-19). Severe forms of acute respiratory failure can develop. In addition, SARS-CoV-2 may affect organs other than the lung, such as the liver, with frequent onset of late cholestasis. We here report the histological findings of a COVID-19 patient, affected by a tardive complication of acute ischemic and gangrenous cholecystitis with a perforated and relaxed gallbladder needing urgent surgery.

CASE PRESENTATION

A 59-year-old Caucasian male, affected by acute respiratory failure secondary to SARS-CoV-2 infection was admitted to our intensive care unit (ICU). Due to the severity of the disease, invasive mechanical ventilation was instituted and SARS-CoV-2 treatment (azithromycin 250 mg once-daily and hydroxychloroquine 200 mg trice-daily) started. Enoxaparin 8000 IU twice-daily was also administered subcutaneously. At day 8 of ICU admission, the clinical condition improved and patient was extubated. At day 32, patient revealed abdominal pain without signs of peritonism at examination, with increased inflammatory and cholestasis indexes at blood tests. At a first abdominal CT scan, perihepatic effusion and a relaxed gallbladder with dense content were detected. The surgeon decided to wait and see the evolution of clinical conditions. The day after, conditions further worsened and a laparotomic cholecystectomy was performed. A relaxed and perforated ischemic gangrenous gallbladder, with a local tissue inflammation and perihepatic fluid, was intraoperatively met. The gallbladder and a sample of omentum, adherent to the gallbladder, were also sent for histological examination. Hematoxylin-eosin-stained slides display inflammatory infiltration and endoluminal obliteration of vessels, with wall breakthrough, hemorrhagic infarction, and nerve hypertrophy of the gallbladder. The mucosa of the gallbladder appears also atrophic. Omentum vessels also appear largely thrombosed. Immunohistochemistry demonstrates an endothelial overexpression of medium-size vessels (anti-CD31), while not in micro-vessels, with a remarkable activity of macrophages (anti-CD68) and T helper lymphocytes (anti-CD4) against gallbladder vessels. All these findings define a histological diagnosis of vasculitis of the gallbladder.

CONCLUSIONS

Ischemic gangrenous cholecystitis can be a tardive complication of COVID-19, and it is characterized by a dysregulated host inflammatory response and thrombosis of medium-size vessels.

High-flow nasal cannula oxygen therapy as an emerging option for respiratory failure: the present and the future

Conventional oxygen therapy (COT) and noninvasive ventilation (NIV) have been considered for decades as frontline treatment for acute or chronic respiratory failure. However, COT can be insufficient in severe hypoxaemia whereas NIV, although highly effective, is poorly tolerated by patients and its use requires a specific expertise. High-flow nasal cannula (HFNC) is an emerging technique, designed to provide oxygen at high flows with an optimal degree of heat and humidification, which is well tolerated and easy to use in all clinical settings. Physiologically, HFNC reduces the anatomical dead space and improves carbon dioxide wash-out, reduces the work of breathing, and generates a positive end-expiratory pressure and a constant fraction of inspired oxygen. Clinically, HFNC effectively reduces dyspnoea and improves oxygenation in respiratory failure from a variety of aetiologies, thus avoiding escalation to more invasive supports. In recent years it has been adopted to treat de novo hypoxaemic respiratory failure, exacerbation of chronic obstructive pulmonary disease (COPD), postintubation hypoxaemia and used for palliative respiratory care. While the use of HFNC in acute respiratory failure is now routine as an alternative to COT and sometimes NIV, new potential applications in patients with chronic respiratory diseases (e.g. domiciliary treatment of patients with stable COPD), are currently under evaluation and will become a topic of great interest in the coming years.

COVID-19 pandemic and non invasive respiratory management: Every Goliath needs a David. An evidence based evaluation of problems

Background and aim

The war against Covid-19 is far from won. This narrative review attempts to describe some problems with the management of Covid-19 induced acute respiratory failure (ARF) by pulmonologists.

Methods

We searched the following databases: MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials and reviewed the references of retrieved articles for additional studies. The search was limited to the terms: Covid-19 AND: acute respiratory distress syndrome (ARDS), SARS, MERS, non invasive ventilation (NIV), high flow nasal cannula (HFNC), pronation (PP), health care workers (HCW).

Results

Protection of Health care workers should be paramount, so full Personal Protective Equipment and Negative pressure rooms are warranted. HFNC alone or with PP could be offered for mild cases (PaO2/FiO2 between 200–300); NIV alone or with PP may work in moderate cases (PaO2/FiO2 between 100–200). Rotation and coupled (HFNC/NIV) strategy can be beneficial. A window of opportunity of 1–2 h is advised. If PaO2/FIO2 significantly increases, Respiratory Rate decreases with a relatively low Exhaled Tidal Volume, the non-invasive strategy could be working and intubation delayed.

Conclusion

Although there is a role for non-invasive respiratory therapies in the context of COVID-19 ARF, more research is still needed to define the balance of benefits and risks to patients and HCW. Indirectly, non invasive respiratory therapies may be of particular benefit in reducing the risks to healthcare workers by obviating the need for intubation, a potentially highly infectious procedure.