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

Humidification during Invasive and Non-Invasive Ventilation: A Starting Tool Kit for Correct Setting

The humidification process of medical gases plays a crucial role in both invasive and non-invasive ventilation, aiming to mitigate the complications arising from bronchial dryness. While passive humidification systems (HME) and active humidification systems are prevalent in routine clinical practice, there is a pressing need for further evaluation of their significance. Additionally, there is often an incomplete understanding of the operational mechanisms of these devices. The current review explores the historical evolution of gas conditioning in clinical practice, from early prototypes to contemporary active and passive humidification systems. It also discusses the physiological principles underlying humidity regulation and provides practical guidance for optimizing humidification parameters in both invasive and non-invasive ventilation modalities. The aim of this review is to elucidate the intricate interplay between temperature, humidity, and patient comfort, emphasizing the importance of individualized approaches to gas conditioning.

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

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

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.

Clinical application of ultrasound-guided totally implantable venous access ports implantation via the posterior approach of the internal jugular vein

BACKGROUND

To determine the feasibility and safety of ultrasound-guided totally implantable venous access port (TIVAP) implantation via the posterior approach of the internal jugular vein (IJV).

METHODS

From September 2021 to August 2022, 88 oncology patients underwent ultrasound-guided implantation of TIVAPs via the posterior approach of the IJV for the administration of chemotherapy. The catheter tip was adjusted to be positioned at the cavoatrial junction under fluoroscopic guidance. Clinical data including surgical success, success rate for the first attempt, intraoperative, and postoperative complications were all collected and analyzed.

RESULTS

All patients underwent successful surgery (100%), whereby 58 were via the right IJV and 30 via the left IJV, and the success rate for the first attempt was 96.59% (85/88). The operation time was 20 to 43 minutes, with an average of 26.59 ± 6.18 minutes with no intraoperative complications. The follow-up duration ranged from 1 to 12 months (mean = 5.28 ± 3.07) and the follow-up rate was 100%. The rate of postoperative complications was 4.55% (4/88), including port-site infection in two cases, fibrin sheath formation in one case, and port flip in one case. No other complications were observed during follow-up.

CONCLUSION

Ultrasound-guided TIVAP implantation via the posterior approach of the IJV is feasible, safe, and effective, with a low rate of intraoperative and postoperative complications. Not only was the curvature of the catheter device smooth, but patients were satisfied with the comfort and cosmetic appearance. Additionally, we could reduce the possible complications of pinching and kinking of the catheter by using this approach. Therefore, further large-sample, prospective, and randomized controlled trials are warranted.

Factors influencing nasal airway pressure and comfort in high-flow nasal cannula oxygen therapy: a volunteer study

BACKGROUND

High-flow nasal cannula (HFNC) oxygen therapy is essentially a constant-flow, noninvasive respiratory support system similar to a noninvasive ventilator operating in constant-flow mode. The clinical outcome of HFNC oxygen therapy is strongly associated with the pressure generated by high-flow gas and the patient's comfort level. This study was performed to explore the relevant factors affecting pressure and comfort of HFNC oxygen therapy in vivo.

METHODS

Thirty-five healthy volunteers were enrolled in the trial. They underwent placement of nasal cannulas of various inner diameters (3, 4 or 5 mm) and treatment with different HFNC devices [HFT-300 (Weishengkang Medical Technology Co., Ltd., Jiangsu China) or H-80 M (BMC Medical Co., Ltd., Beijing China)],and the nasal airway pressure and comfort were assessed. Multiple linear regression was used to determine predictors of airway pressure.

RESULTS

Multiple linear regression showed that the end-expiratory pressure was associated with the flow rate, sex, height, and cannula size. The end-expiratory pressure increased by 0.6 cmH2O per 1-mm increase in cannula diameter, decreased by 0.3 cmH2O per 10-cm increase in participant height (with a 0.35 cmH2O decrease for men), and increased by 1 cmH2O when the flow rate increased by 10 L/min (R2 = 0.75, P < 0.05 for all variables in model). In addition, the pressure generated by the H-80 M device was higher than that generated by the HFT-300 device (P < 0.05). Discomfort manifested as difficulty in expiration, and its severity increased as the cannula diameter increased; however there was no significant difference in comfort between the two HFNC devices (P > 0.05).

CONCLUSION

In volunteers undergoing HFNC oxygen therapy, the nasal cannula diameter, flow rate, sex, height, and device model can affect the nasal airway pressure, and the nasal catheter diameter and flow rate can affect comfort. These factors should be given close attention in clinical practice.

TRIAL REGISTRATION

ChiCTR2300068313 (date of first registration: 14 February 2023,  https://www.chictr.org.cn ).

Proposed protocol for utilising high-flow nasal oxygen therapy in treatment of dogs hospitalised due to pneumonia

BACKGROUND

High-flow nasal oxygen (HFNO) therapy is a non-invasive respiratory support method that provides oxygen-enriched, warmed, and humidified air to respiratory-compromised patients. It is widely used in human medical care, but in veterinary medicine it is still a relatively new method. No practical guidelines exist for its use in canine pneumonia patients, although they could potentially benefit from HFNO therapy. This study aims to provide a new, safe, non-invasive, and effective treatment protocol for oxygen supplementation of non-sedated dogs with pneumonia.

METHODS

Twenty privately owned dogs with pneumonia will receive HFNO therapy at a flow rate of 1-2 L/kg, and the fraction of inspired oxygen will be determined individually (ranging from 21% to 100%). HFNO therapy will continue as long as oxygen support is needed based on clinical evaluation. Patients will be assessed thrice daily during their hospitalisation, with measured primary outcomes including partial pressure of oxygen, oxygen saturation, respiratory rate and type, days in hospital, and survival to discharge.

DISCUSSION

The proposed protocol aims to provide a practical guideline for applying HFNO to dogs hospitalised due to pneumonia. The protocol could enable more efficient and well-tolerated oxygenation than traditional methods, thus hastening recovery and improving survival of pneumonia patients.

Post-extubation high-flow nasal cannula oxygen therapy <em>versus</em> non-invasive ventilation in chronic obstructive pulmonary disease with hypercapnic respiratory failure

The sequential use of non-invasive ventilation (NIV) for weaning in hypercapnic respiratory failure patients is a recommended practice. However, the effectiveness of weaning on High flow nasal cannula (HFNC) is unclear. Chronic obstructive pulmonary disease patients with hypercapnic respiratory failure who received invasive ventilation were screened for enrolment. This study was a single-centre, prospective, randomized comparative study. The primary outcome was treatment failure within 72 hours after extubation. Patients who were screened positive for extubation were enrolled in the study and randomized into the HFNC group and NIV group using a computer-generated simple randomization chart. The treatment failure was defined as a return to invasive mechanical ventilation, or a switch in respiratory support modality (i.e., changing from HFNC to NIV or from NIV to HFNC). Of 72 patients, 62 patients were included in the study. Treatment failure occurred in 8 patients (26.67 %) in HFNC group and 8 patients in NIV group (25%) (p=0.881). The mean duration of ICU stay in HFNC group was 5.47±2.26 days and 6.56±3.39 in NIV group (p=0.376). In the current study, HFNC was non-inferior to NIV in preventing post-extubation respiratory failure in COPD patients, while HFNC had better treatment tolerance.

Broadening the Berlin definition of ARDS to patients receiving high-flow nasal oxygen: an observational study in patients with acute hypoxemic respiratory failure due to COVID-19

BACKGROUND

High-flow nasal oxygen (HFNO) is increasingly used in patients with acute hypoxemic respiratory failure. It is uncertain whether a broadened Berlin definition of acute respiratory distress syndrome (ARDS), in which ARDS can be diagnosed in patients who are not receiving ventilation, results in similar groups of patients receiving HFNO as in patients receiving ventilation.

METHODS

We applied a broadened definition of ARDS in a multicenter, observational study in adult critically ill patients with acute hypoxemic respiratory failure due to coronavirus disease 2019 (COVID-19), wherein the requirement for a minimal level of 5 cm H₂O PEEP with ventilation is replaced by a minimal level of airflow rate with HFNO, and compared baseline characteristics and outcomes between patients receiving HFNO and patients receiving ventilation. The primary endpoint was ICU mortality. We also compared outcomes in risk for death groups using the PaO₂/FiO₂ cutoffs as used successfully in the original definition of ARDS. Secondary endpoints were hospital mortality; mortality on days 28 and 90; need for ventilation within 7 days in patients that started with HFNO; the number of days free from HFNO or ventilation; and ICU and hospital length of stay.

RESULTS

Of 728 included patients, 229 patients started with HFNO and 499 patients with ventilation. All patients fulfilled the broadened Berlin definition of ARDS. Patients receiving HFNO had lower disease severity scores and lower PaO₂/FiO₂ than patients receiving ventilation. ICU mortality was lower in receiving HFNO (22.7 vs 35.6%; p = 0.001). Using PaO₂/FiO₂ cutoffs for mild, moderate and severe arterial hypoxemia created groups with an ICU mortality of 16.7%, 22.0%, and 23.5% (p = 0.906) versus 19.1%, 37.9% and 41.4% (p = 0.002), in patients receiving HFNO versus patients receiving ventilation, respectively.

CONCLUSIONS

Using a broadened definition of ARDS may facilitate an earlier diagnosis of ARDS in patients receiving HFNO; however, ARDS patients receiving HFNO and ARDS patients receiving ventilation have distinct baseline characteristics and mortality rates.

TRIAL REGISTRATION

The study is registered at ClinicalTrials.gov (identifier NCT04719182).

Effect of lidocaine spray on reliving non-coring needle puncture-related pain in patients with totally implantable venous access port: a randomized controlled trial

PURPOSE

Patients with the placement of a totally implantable venous access port (TIVAP) commonly suffer from pain caused by inserting a non-coring needle. At present, lidocaine cream and cold spray are extensively used for pain management, but they are complex to manage in busy medical environments and developing countries. The lidocaine spray combines the analgesic effect of lidocaine cream and the rapid onset of cold spray, which can effectively alleviate the pain related to non-coring needle puncture in patients with TIVAP. This randomized-controlled trial aimed to explore the effectiveness, acceptability, and safety of lidocaine spray in relieving the pain of non-coring needle puncture in patients with TIVAP.

METHODS

A total of 84 patients who were hospitalized in the oncology department of a Grade III Level-A hospital in Shanghai from January 2023 to March 2023 and were implanted with TIVAP and required non-coring needle puncture were selected as the study subjects. The recruited patients were randomly assigned to the intervention group and the control group (n=42). Before routine maintenance, the intervention group received lidocaine spray 5 min before disinfection, while the control group received water spray 5 min before disinfection. The main clinical outcome was pain, and the degree of puncture pain in both groups was evaluated using the visual analogue scale.

RESULTS

There were no significant differences between the two groups in age, gender, educational level, body mass index, port implantation time, and disease diagnosis (P>0.05). The pain score in the intervention and control groups was 15.12±6.61mm and 36.50±18.79mm, respectively (P<0.001). There were 2 (4.8%) patients with moderate pain in the intervention group and 18 (42.9%) patients with moderate pain in the control group (P<0.001). In the control group, 3 (7.1%) patients reported severe pain. The median comfortability score for the two groups of patients was 10, but there was a difference between the two groups (P<0.05) because the intervention group tilted to the right. The successful puncture rate of the first time puncture had no difference between the two groups, both being 100%. Moreover, 33 patients (78.6%) in the intervention group and 12 patients (28.6%) in the control group reported that they would choose the same spray for intervention in the future (P<0.001). During the 1 week of follow-up, 1 patient in the intervention group developed skin itching (P>0.05).

CONCLUSIONS

The local use of lidocaine spray in patients with TIVAP is effective, acceptable, and safe to alleviate the pain caused by non-coring needle puncture.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (registration number: ChiCTR2300072976).

Comparison of actual performance in humidification among different high-flow nasal cannula devices: a bench study

Background

The physiological effects of HFNC devices are closely related to temperature and humidity. HFNC devices from different manufacturers may have varied performances. It is unclear whether there are differences in the humidification performance of different HFNC devices and the degree of differences.

Methods

Four integrated HFNC devices (AIRVO 2, Fisher & Paykel Healthcare, Auckland, New Zealand; TNI softFlow 50, TNI Medical AG, Würzburg, Germany; HUMID-BH, RESPIRACARE, Shenyang, China; OH-70C, Micomme, Hunan, China) and a ventilator with an HFNC module (bellavista 1000, Imtmedical, Buchs, Switzerland) were evaluated using their matching circuits. The dew point temperature was set at 31, 34, and 37°C (set-DP). In MR850, it was set to non-invasive mode (34°C/-3°C) and invasive mode (40°C/-3°C), respectively. At each level of set-DP, the flow was set from 20 L/min up to its maximum set limit at a gradient of 5 L/min or 10 L/min. After stabilization, the dew point temperature, temperature, relative humidity, and flow rate of the delivered gas from the cannulas were recorded.

Results

There were significant differences in actual-DP among these devices at any set-DP (p < 0.001). The actual-DP of OH-70C and TNI softFlow 50 was lower than set-DP, and the difference between the actual-DP and the set-DP of these two devices increased with the increase of set-DP. AIRVO 2, bellavista 1000 (MR850), and HUMID-BH can provide the nominal humidity at 37°C. The actual-DP increased with the increase of set-flow under each set-DP in AIRVO 2, TNI softFlow 50 and bellavista 1000 (MR850), but decreased when the set-flow was greater than 60 L/min. The actual-T of the delivered gas was higher than actual-DP in all devices and was higher than set-DP in AIRVO 2 and HUMID-BH.

Conclusion

Set-flow, set-DP, and types of devices will affect the actual temperature and humidity of the delivered gas. AIRVO 2, bellavista 1000 (MR850), and HUMID-BH can provide the nominal humidity at 37°C and may be more suitable for tracheotomy patients. The flow rate over 60 L/min should be set with caution.

Changes in Oxygen Saturation During Fiberoptic Bronchoscopy: High-Flow Nasal Cannula versus Standard Oxygen Therapy

BACKGROUND

Hypoxemia is a relatively common complication in stable patients during fiberoptic bronchoscopy (FOB). To prevent this complication, high-flow nasal cannula (HFNC) has been described as an alternative to standard oxygen therapy. However, the advantages of HFNC over standard oxygen therapy in acute care patients receiving supplemental oxygen before FOB performed with an oral approach are unknown.

METHODS

We conducted an observational study that involved subjects with a presumptive diagnosis of pneumonia and a clinical indication for a bronchial aspirate sample. The type of oxygen support (standard oxygen therapy vs HFNC) was selected according to availability. The oxygen flow in the HFNC group was 60 L/min. In both groups, the FIO2 was set at 0.40. Hemodynamic, respiratory dynamics, and gas exchange data were collected at baseline, before, during, and 24 h after FOB.

RESULTS

Forty subjects were included, 20 in each group (HFNC and standard oxygen therapy). The study was performed on day 5 of hospitalization in the HFNC group and on day 4 in the standard oxygen therapy group (P = .10). No significant between-group differences in baseline characteristics were observed. HFNC vs standard oxygen therapy was associated with a smaller decrease in SpO2 levels during the procedure (94% vs 90%; P = .040, respectively) and with less variation between the last SpO2 measured before FOB and the lowest SpO2 during FOB (Δ SpO2 ): 2% versus 4.5% (P = .01, respectively).

CONCLUSIONS

In acute subjects who required oxygen support before FOB, the use of HFNC during FOB with an oral approach was associated with a smaller decrease in SpO2 and lower Δ SpO2 compared with standard oxygen therapy.

The use of High-Flow Nasal Oxygen Therapy in 4 dogs undergoing bronchoscopy

Introduction

High-Flow Nasal Oxygen Therapy is a method to deliver warmed, humidified air-oxygen blended at high flow rates to patients through a nasal cannula using a specialized, commercially available machine. This is a well-tolerated, safe and effective method for oxygen delivery to healthy and hypoxemic dogs. Patients undergoing bronchoscopic procedures frequently develop hypoxemia. Human trials have shown a reduction in incidents of hypoxemic events and higher pulse oximeter oxygen saturation during bronchoscopies in patients on High-Flow Nasal Oxygen.

Materials and methods

This is a single-centre, prospective case series. All dogs weighing between 5 and 15 kg and undergoing bronchoscopy during the study period (03/07/2022-01/10/2022) were eligible.

Results

Twelve patients were eligible for inclusion of which four were enrolled. No clinically significant complications related to the use of High-Flow Nasal Oxygen Therapy were recorded. Two of the patients were re-intubated post bronchoscopy due to clinician preference for recovery. One of the patients had a self-limiting period of severe hypoxemia with a pulse oximeter oxygen saturation of 84% for &lt; 1 min during bronchoalveolar lavage, and whilst undergoing High-Flow Nasal Oxygen administration. Another patient had a self-limiting episode of mild hypoxemia (SpO2 of 94% lasting &lt; 1 min) 5 min after completion of bronchoalveolar lavage.

Conclusion

No clinically relevant complications relating to High-Flow Nasal Oxygen Therapy were recorded in this case series, although further studies are required to confirm this conclusion. This initial data suggests that the use of High-Flow Nasal Oxygen therapy during bronchoscopy is feasible and potentially safe, although it may not prevent hypoxemia in these patients. The use of High-Flow Nasal Oxygen Therapy during bronchoscopy in small patients carries multiple potential benefits and further studies to compare its efficacy against other traditional oxygen delivery systems are warranted in this patient population.

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

BACKGROUND

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

METHODS

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

RESULTS

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

INTERPRETATION

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

Efficacy and safety of high-flow nasal cannula therapy in elderly patients with acute respiratory failure

INTRODUCTION

To assess the efficacy and safety of high-flow nasal cannula (HFNC) in elderly patients with acute respiratory failure (ARF) not due to COVID-19, refractory to treatment with conventional oxygen therapy and/or intolerant to noninvasive ventilation (NIV) or continuous positive airway pressure (CPAP) and without criteria for admission to intensive care units (ICU).

METHODS

Prospective observational study of patients with ARF treated with HFNC who presented clinical and arterial blood gas deterioration after 24 h of medical treatment and oxygenation by conventional systems. The degree of dyspnoea, gas exchange parameters (arterial O2 pressure/inspired O2 fraction ratio (PaO2/FiO2); oxygen saturation measured by oximetry/ inspired fraction of oxygen (Sp02/Fi02), ROX index), degree of patient tolerance and mortality were evaluated. These were measured at discharge from the emergency department (ED), 24 h after treatment with conventional oxygenation and 60, 120 min and 24 h after initiation of HFNC. The results were analyzed for all patients as a whole and for patients with hypercapnia (arterial carbon dioxide tension (PaCO2) < 45 mmHg) separately.

RESULTS

200 patients were included in the study between November 2019 and November 2020, with a mean age of 83 years, predominantly women (61.9%), obese (Body Mass Index (BMI) 31.1), with high comorbidity (Charlson index 4) and mild-moderate degree of dependence (Barthel 60). A number of 128 patients (64%) were hypercapnic. None had respiratory acidosis (pH 7.39). Evaluation at 60 min, 120 min and 24 h showed significant improvement in all patients and in the subgroup of hypercapnic patients with respect to baseline parameters in respiratory rate (RR), dyspnoea, ROX index, PaO2/FiO2, SpO2/FiO2 and patient comfort. No changes in PaCO2 or level of consciousness were observed. HFNC was well tolerated. Ten patients (5%) died due to progression of the disease causing ARF.

CONCLUSIONS

HFNC is an effective and safe alternative in elderly patients with ARF not due to COVID-19, refractory to treatment with conventional oxygen therapy and/or intolerant to NIV or CPAP and without criteria for admission to ICU.

Techniques for Oxygenation and Ventilation in Coronavirus Disease 2019

This paper discusses mechanisms of hypoxemia and interventions to oxygenate critically ill patients with COVID-19 which range from nasal cannula to noninvasive and mechanical ventilation. Noninvasive ventilation includes continuous positive airway pressure ventilation (CPAP) and high-flow nasal cannula (HFNC) with or without proning. The evidence for each of these modalities is discussed and thereafter, when to transition to mechanical ventilation (MV). Various techniques of MV, again with and without proning, and rescue strategies which would include extra corporeal membrane oxygenation (ECMO) when it is available and permissive hypoxemia where it is not, are discussed.

Effect of high-flow nasal cannula therapy on thirst sensation and dry mouth after extubation: A single-centre prospective cohort study

OBJECTIVES

Little is known regarding the association between the type of oxygen therapy and thirst sensation after extubation. This study aimed to assess the effect of post-extubation high-flow nasal cannula on thirst.

RESEARCH METHODOLOGY/DESIGN AND SETTING

This single-centre prospective cohort study included 100 ventilated patients. After extubation, patients received either high-flow nasal cannula (n = 19) or conventional oxygen therapy (n = 81). Thirst intensity was evaluated by a self-reporting numeric rating scale, and dry mouth was defined objectively using an oral moisture checking device.

MAIN OUTCOME MEASURES

The primary outcome was thirst intensity 24 hours post-extubation. Secondary outcomes were thirst intensity at 4 hours post-extubation and prevalence of dry mouth at 4 hours and 24 hours post-extubation.

RESULTS

At 24 hours post-extubation, the median (interquartile range) thirst intensity was 5 (1, 7) in the high-flow nasal cannula group and 5 (4, 6) in the conventional oxygen group. After adjustment, high-flow nasal cannula therapy was significantly associated with lower thirst intensity (adjusted odds ratio, 0.14; 95 % confidence interval (CI) 0.04-0.49; P = 0.002). At 4 hours post-extubation, high-flow nasal cannula was also associated with lower thirst intensity (adjusted odds ratio, 0.19; 95 % CI, 0.06-0.60; P = 0.005). The number of patients with dry mouth was not significantly different between the two groups (high-flow vs conventional oxygen therapy, 42.1 % vs 30.9 % [4 hours after extubation]; 47.4 % vs 34.6 % [24 hours after extubation]).

CONCLUSIONS

High-flow nasal cannula therapy was associated with lower thirst intensity than conventional oxygen therapy following extubation. However, there was no significant difference in the prevalence of dry mouth.

Clinical review of high-flow nasal oxygen therapy in human and veterinary patients

Oxygen therapy is the first-line treatment for hypoxemic acute respiratory failure. In veterinary medicine this has traditionally been provided via mask, low-flow nasal oxygen cannulas, oxygen cages and invasive positive pressure ventilation. Traditional non-invasive modalities are limited by the maximum flow rate and fraction of inspired oxygen (FiO₂) that can be delivered, variability in oxygen delivery and patient compliance. The invasive techniques are able to provide higher FiO₂ in a more predictable manner but are limited by sedation/anesthesia requirements, potential complications and cost. High-flow nasal oxygen therapy (HFNOT) represents an alternative to conventional oxygen therapy. This modality delivers heated and humidified medical gas at adjustable flow rates, up to 60 L/min, and FiO₂, up to 100%, via nasal cannulas. It has been proposed that HFNOT improves pulmonary mechanics and reduces respiratory fatigue via reduction of anatomical dead space, provision of low-level positive end-expiratory pressure (PEEP), provision of constant FiO₂ at rates corresponding to patient requirements and through improved patient tolerance. Investigations into the use of HFNOT in veterinary patients have increased in frequency since its clinical use was first reported in dogs with acute respiratory failure in 2016. Current indications in dogs include acute respiratory failure associated with pulmonary parenchymal disease, upper airway obstruction and carbon monoxide intoxication. The use of HFNOT has also been advocated in certain conditions in cats and foals. HFNOT is also being used with increasing frequency in the treatment of a widening range of conditions in humans. Although there remains conflict regarding its use and efficacy in some patient groups, overall these reports indicate that HFNOT decreases breathing frequency and work of breathing and reduces the need for escalation of respiratory support. In addition, they provide insight into potential future veterinary applications. Complications of HFNOT have been rarely reported in humans and animals. These are usually self-limiting and typically result in lower morbidity and mortality than those associated with invasive ventilation techniques.

High-flow nasal cannula oxygen therapy is superior to conventional oxygen therapy in intensive care unit patients after extubation

BACKGROUND

Optimal oxygen supply is the cornerstone of the management of critically ill patients after extubation. High flow oxygen system is an alternative to standard oxygen therapy. This research explored the efficacy of high-flow nasal cannula (HFNC) oxygen therapy in patients after extubation in the intensive care unit (ICU).

METHOD

We retrospectively analyzed critically ill patients admitted to the ICU and subjected to HFNC or conventional oxygen therapy from January 2018 to June 2022 at the Suzhou Hospital of Integrated Traditional Chinese and Western Medicine. Blood gas analysis, a cough and sputum assessment, and cardiovascular function examinations were performed to evaluate the effect of HFNC oxygen therapy on patients. Also, the 28-d mortality rate, reintubation rate and incidence of respiratory failure were analyzed to evaluate whether HFNC oxygen therapy could improve patients' outcome.

RESULTS

In patients who received HFNC oxygen therapy, the partial pressure of oxygen and oxygenation index increased, and the respiratory rate decreased. HFNC oxygen therapy improved the patients' ability to cough up sputum and promoted the expulsion of sputum. In terms of cardiovascular function, patients who received HFNC oxygen therapy had a significant improvement in heart rate, but there was no real effect on patients' arterial pressure. There was no significant difference in the rates of reintubation (P = 0.202), 28-d mortality (P = 0.558) or respiratory failure (P = 0.677) between patients who received different oxygen therapies including HFNC oxygen therapy.

CONCLUSION

HFNC oxygen therapy improves the respiratory function of patients after extubation in their ICU and improves their coughing ability.

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

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

Recent advances in the use of high flow nasal oxygen therapies

High flow nasal oxygen is a relatively new option for treating patients with respiratory failure, which decreases work of breathing, improves tidal volume, and modestly increases positive end expiratory pressure. Despite well-described physiologic benefits, the clinical impact of high flow nasal oxygen is still under investigation. In this article, we review the most recent findings on the clinical efficacy of high flow nasal oxygen in Type I, II, III, and IV respiratory failure within adult and pediatric patients. Additionally, we discuss studies across clinical settings, including emergency departments, intensive care units, outpatient, and procedural settings.

Performance of Invasive Mode in Different Heated Humidification Systems With High-Flow Nasal Cannula

BACKGROUND

Oxygen therapy via high-flow nasal cannula generates physiologic changes that impact ventilatory variables of patients. However, we know that there are detrimental effects on airway mucosa related to inhalation of gases. The objective of this study was to evaluate the performance in terms of absolute humidity, relative humidity, and temperature of different brands of heated humidifiers and circuits in the invasive mode during the use of high-flow oxygen therapy in flows between 30 and 100 L/min.

METHODS

A prospective observational study conducted at the Sanatorio Anchorena equipment analysis laboratory; September 5 to October 20, 2019.

RESULTS

A statistically significant interaction was found among the programmed flows and the different combinations of devices and circuits for the delivery of absolute humidity (P < .001). An effect of flow on delivered absolute humidity was found, regardless of the equipment and circuit combination (P < .001). However, in the invasive mode, the combination of the Fisher&Paykel MR850 heated humidifier with the Medtronic-Dar circuit, the Intersurgical circuit, and the AquaVENT circuit always reached or achieved absolute humidity values > 33 mg/L, even at flows up to 100 L/min. The combination of the Flexicare FL9000 heated humidifier with the Fisher&Paykel RT202 circuit, the Fisher&Paykel Evaqua 2 circuit, the Flexicare circuit, the AquaVENT circuit, and the GGM circuit achieved similar results. The mean (SD) of absolute humidity delivered in the invasive mode (36.2 ± 5.9 mg/L) was higher compared with the noninvasive mode (26.8 ± 7.2 mg/L) (P < .001), regardless of circuit and programmed flows.

CONCLUSIONS

When heated humidifiers were used in the invasive mode for high-flow oxygen therapy, absolute humidity depended not only on the heated humidifiers and the combination of circuits but also on the programmed flow, especially at flows > 50 L/min. Moreover, the heated humidifiers exhibited different behaviors, in some cases inefficient, in delivering adequate humidification. However, some equipment improved performance when set to the invasive mode.

Transnasal High-Flow Oxygen Therapy versus Noninvasive Positive Pressure Ventilation in the Treatment of COPD with Type II Respiratory Failure: A Meta-Analysis

Objective

To compare the safety and efficacy of transnasal high-flow oxygen therapy (HFNT) and noninvasive positive pressure ventilation (NIV) in the treatment of chronic obstructive pulmonary disease (COPD) with type II respiratory failure.

Methods

PubMed, the Cochrane Library, Embase, CBM, CNKI, and other databases were searched for randomized controlled trials (RCTS) on the efficacy of HFNT and NIV in the treatment of COPD. Meta-analysis was conducted using RevMan 5.3 software after two researchers screened literatures, extracted data, and evaluated the methodological quality of the included studies according to inclusion and exclusion criteria.

Results

A total of 948 patients were included in 12 RCTS. Comprehensive analysis results showed that the HFNC group had higher levels of 12 h-PAO2, 48 h-PACO2 and, 48 h-pH than the NIV group, and the differences were statistically significant (P < 0.05). There were no significant differences in 24 h-PAO2 and 72 h-PAO2, 12 h-PACO2, 24 h-PACO2 and 72 h-PACO2, 24 h-pH, 48 h-pH, and 72 h-pH between the two groups after treatment (P > 0.05).

Conclusions

Compared with NIV, HFNC does not increase the treatment failure rate in COPD patients with type II respiratory failure, and HFNC has better comfort and tolerance, which is a new potential respiratory support treatment for COPD patients with type II respiratory failure.

Use of high flow nasal cannula in patients with acute respiratory failure in general wards under intensivists supervision: a single center observational study

BACKGROUND

Few data exist on high flow nasal cannula (HFNC) use in patients with acute respiratory failure (ARF) admitted to general wards.

RATIONALE AND OBJECTIVES

To retrospectively evaluate feasibility and safety of HFNC in general wards under the intensivist-supervision and after specific training.

METHODS

Patients with ARF (dyspnea, respiratory rate-RR > 25/min, 150 < PaO₂/FiO₂ < 300 mmHg during oxygen therapy) admitted to nine wards of an academic hospital were included. Gas-exchange, RR, and comfort were assessed before HFNC and after 2 and 24 h of application.

RESULTS

150 patients (81 male, age 74 [60-80] years, SOFA 4 [2-4]), 123 with de-novo ARF underwent HFNC with flow 60 L/min [50-60], FiO₂ 50% [36-50] and temperature 34 °C [31-37]. HFNC was applied a total of 1399 days, with a median duration of 7 [3-11] days. No major adverse events or deaths were reported. HFNC did not affect gas exchange but reduced RR (25-22/min at 2-24 h, p < 0.001), and improved Dyspnea Borg Scale (3-1, p < 0.001) and comfort (3-4, p < 0.001) after 24 h. HFNC failed in 20 patients (19.2%): 3 (2.9%) for intolerance, 14 (13.4%) escalated to NIV/CPAP in the ward, 3 (2.9%) transferred to ICU. Among these, one continued HFNC, while the other 2 were intubated and they both died. Predictors of HFNC failure were higher Charlson's Comorbidity Index (OR 1.29 [1.07-1.55]; p = 0.004), higher APACHE II Score (OR 1.59 [1.09-4.17]; p = 0.003), and cardiac failure as cause of ARF (OR 5.26 [1.36-20.46]; p = 0.02).

CONCLUSION

In patients with mild-moderate ARF admitted to general wards, the use of HFNC after an initial training and daily supervision by intensivists was feasible and seemed safe. HFNC was effective in improving comfort, dyspnea, and respiratory rate without effects on gas exchanges. Trial registration This is a single-centre, noninterventional, retrospective analysis of clinical data.

High flow nasal catheter therapy versus non-invasive positive pressure ventilation in acute respiratory failure (RENOVATE trial): protocol and statistical analysis plan

Background: The best way to offer non-invasive respiratory support across several aetiologies of acute respiratory failure (ARF) is presently unclear. Both high flow nasal catheter (HFNC) therapy and non-invasive positive pressure ventilation (NIPPV) may improve outcomes in critically ill patients by avoiding the need for invasive mechanical ventilation (IMV). Objective: Describe the details of the protocol and statistical analysis plan designed to test whether HFNC therapy is non-inferior or even superior to NIPPV in patients with ARF due to different aetiologies. Methods: RENOVATE is a multicentre adaptive randomised controlled trial that is recruiting patients from adult emergency departments, wards and intensive care units (ICUs). It takes advantage of an adaptive Bayesian framework to assess the effectiveness of HFNC therapy versus NIPPV in four subgroups of ARF (hypoxaemic non-immunocompromised, hypoxaemic immunocompromised, chronic obstructive pulmonary disease exacerbations, and acute cardiogenic pulmonary oedema). The study will report the posterior probabilities of non-inferiority, superiority or futility for the comparison between HFNC therapy and NIPPV. The study assumes neutral priors and the final sample size is not fixed. The final sample size will be determined by a priori determined stopping rules for non-inferiority, superiority and futility for each subgroup or by reaching the maximum of 2000 patients. Outcomes: The primary endpoint is endotracheal intubation or death within 7 days. Secondary outcomes are 28-day and 90-day mortality, and ICU-free and IMV-free days in the first 28 days. Results and conclusions: RENOVATE is designed to provide evidence on whether HFNC therapy improves, compared with NIPPV, important patient-centred outcomes in different aetiologies of ARF. Here, we describe the rationale, design and status of the trial. Trial registration:ClinicalTrials.gov NCT03643939.

Comparison of comfort and complications of Implantable Venous Access Port (IVAP) with ultrasound guided Internal Jugular Vein (IJV) and Axillary Vein/Subclavian Vein (AxV/SCV) puncture in breast cancer patients: a randomized controlled study

Background

Axillary vein/subclavian vein (AxV/SCV) and Internal jugular vein (IJV) are commonly used for implantable venous access port (IVAP) implantation in breast cancer patients for chemotherapy. Previous research focused on comparison of complications while patient comfort was ignored. This study aims to compare patient comfort, surgery duration and complications of IVAP implantation between IJV and AxV/SCV approaches.

Methods

Two hundred forty-eight breast cancer patients were enrolled in this randomized controlled study from August 2020 to June 2021. Patients scheduled to undergo IVAP implantation were randomly and equally assigned to receive central venous catheters with either AxV /SCV or IJV approaches. All patients received comfort assessment using a comfort scale table at day 1, day 2 and day 7 after implantation. Patient comfort, procedure time of operation as well as early complications were compared.

Results

Patient comfort was significantly better in the AxV/SCV group than that of IJV group in day 1 (P < 0.001), day 2 (P < 0.001) and day 7(P = 0.023). Procedure duration in AxV/SCV group was slightly but significantly shorter than IJV group (27.14 ± 3.29 mins vs 28.92 ± 2.54 mins, P < 0.001). More early complications occurred in AxV/SCV group than IJV group (11/124 vs 2/124, P = 0.019). No difference of complications of artery puncture, pneumothorax or subcutaneous hematoma between these two groups but significantly more catheter misplacement in AxV/SCV group than IJV group (6/124 vs 0/124, P = 0.029). Absolutely total risk of complications was rather low in both groups (8.87% in AxV/SCV group and 1.61% in IJV group).

Conclusions

Our study indicates that patients with AxV/SCV puncture have higher comfort levels than IJV puncture. AxV/SCV puncture has shorter procedure duration but higher risk of early complications, especially catheter misplacement. Both these two approaches have rather low risk of complications. Consequently, our study provides an alternative choice for breast cancer patients to reach better comfort.

High-Flow Nasal Cannula and COVID-19: A Clinical Review

During the coronavirus disease 2019 (COVID-19) pandemic, noninvasive respiratory support has played a central role in managing patients affected by moderate-to-severe acute hypoxemic respiratory failure, despite inadequate scientific evidence to support its usage. High-flow nasal cannula (HFNC) treatment has gained popularity because of its effectiveness in delivering a high fraction of humidified oxygen, which improves ventilatory efficiency and the respiratory pattern, as well as its reported high tolerability, ease of use, and application outside of ICUs. Nevertheless, the risk of infection transmission to health-care workers has raised some concerns about its use in the first wave of the pandemic outbreak, with controversial recommendations provided by different scientific societies. This narrative review provides an overview of the recent evidence on the physiologic rationale, risks, and benefits of using HFNC instead of conventional oxygen therapy and other types of noninvasive respiratory support devices, such as continuous positive airway pressure and noninvasive ventilation in patients affected by COVID-19 pneumonia with associated acute hypoxemic respiratory failure. It also summarizes the available evidence with regard to the clinical use of HFNC during the current pandemic and its reported outcomes, and highlights the risks of bioaerosol dispersion associated with HFNC use.

Aerosol particle concentrations with different oxygen devices and interfaces for spontaneous breathing patients with tracheostomy: a randomised crossover trial

For stable spontaneously breathing tracheostomy patients with uncuffed airways, different humidification devices and interfaces did not generate clinically significant differences of aerosol particle concentrations https://bit.ly/2Y1HSO2.

Management of Adult Patients With Oxygen in the Acute Care Setting

Providing supplemental oxygen to hospitalized adults is a frequent practice and can be administered via a variety of devices. Oxygen therapy has evolved over the years, and clinicians should follow evidence-based practices to provide maximum benefit and avoid harm. This systematic review and subsequent clinical practice guidelines were developed to answer questions about oxygenation targets, monitoring, early initiation of high-flow oxygen (HFO), benefits of HFO compared to conventional oxygen therapy, and humidification of supplemental oxygen. Using a modification of the RAND/UCLA Appropriateness Method, 7 recommendations were developed to guide the delivery of supplemental oxygen to hospitalized adults: (1) aim for S_pO2 range of 94-98% for most hospitalized patients (88-92% for those with COPD), (2) the same S_pO2 range of 94-98% for critically ill patients, (3) promote early initiation of HFO, (4) consider HFO to avoid escalation to noninvasive ventilation, (5) consider HFO immediately postextubation to avoid re-intubation, (6) either HFO or conventional oxygen therapy may be used with patients who are immunocompromised, and (7) consider humidification for supplemental oxygen when flows > 4 L/min are used.

Hygrometric Performances of Different High-Flow Nasal Cannula Devices: Bench Evaluation and Clinical Tolerance

BACKGROUND

High-flow nasal cannula (HFNC) is increasingly used for the management of respiratory failure. Settings include [Formula: see text], total gas flow, and temperature target. Resulting absolute humidity (AH) at the nasal cannula may affect clinical tolerance, and optimal settings with respect to hygrometry remain poorly documented.

METHODS

A bench study was designed to assess AH delivered by 4 HFNC devices (Optiflow, Airvo 2, Precision Flow, and Hydrate) according to flow, ambient temperature, and other available settings. Clinical tolerance of different levels of hygrometry (20, 30, and 40 mg H₂O/L) was evaluated in 15 healthy volunteers.

RESULTS

With [Formula: see text] set at 1.0, normal ambient temperature, and settings made accordingly to the manufacturers' recommendations, mean ± SD AH was 42.2 ± 3.1, 39.5 ± 1.8, 35.7 ± 2.0, and 32.9 ± 2.7 mg H₂O/L for the Airvo 2, Optiflow, Hydrate, and Precision Flow, respectively, (P < .001). AH dropped from -3.5 to -10.7 mg H₂O/L (P <. 001) with high ambient temperature, except for the Precision Flow. Increasing flow did not significantly affect AH except for the Precision Flow (from 36.4 ± 1.6 to 29.8 ± 0.2 mg H₂O/L at 10 and 40 L/min, respectively, [P < .001]). The lowest AH was encountered with the Optiflow set with noninvasive ventilation (NIV) mode, without compensation algorithm, and at high ambient temperature (14.2 ± 1.5 mg H₂O/L). In studied subjects, AH significantly affected breathing comfort, reduced from 7.0 ± 1.0 to 3.0 ± 2.0 at 40 and 20 mg H₂O/L, respectively, (P < .001). Comfort was similar at 30 and 40 mg H₂O/L.

CONCLUSIONS

When used according to manufacturer's recommendations and at normal ambient temperature, all the HFNC devices evaluated achieved satisfactory hygrometric output with respect to breathing comfort evaluated in healthy subjects (≥ 30 mg H₂O/L). Substantial differences exist between devices, and optimal knowledge of their working principles is required as inappropriate usage may dramatically alter efficacy and clinical tolerance.

A Review of High Flow Nasal Cannula Oxygen Therapy in Human and Veterinary Medicine

Respiratory distress is a common ailment in small animal medicine. Oxygen supplementation is a mainstay of initial therapy. High Flow Nasal Cannula Oxygen Therapy (HFNCOT) has become increasingly popular as a treatment modality in human medicine, and more recently in canine patients. These devices deliver high flow rates of heated and humidified oxygen at an adjustable fraction of inspired oxygen (FiO₂). This article reviews current literature in human patients on HFNCOT as well as studies that have evaluated its use in veterinary patients. A discussion of the respiratory physiology that is associated with respiratory distress, in addition to an overview of currently available oxygen supplementation modalities is provided. The physiologic benefits of HFNCOT are explained, as are technical aspects associated with its use. Recommendations on initial settings, maintenance therapy, and weaning are also described.

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

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

Nasal High-Flow during Exercise in Patients with COPD: A Systematic Review and Meta-Analysis

Rationale Several studies have evaluated the effect of nasal high flow (NHF) to enhance exercise performance and tolerance in patients with COPD, however results are disparate. Objective The aim of this systematic review and meta-analysis was to assess the effect of NHF as an adjuvant to exercise training on functional exercise capacity in patients with COPD. Method An electronic search was carried out in the following databases: Pubmed, CENTRAL, PEDro, ScienceDirect, Web of Science, OpenGrey, ClinicalTrials.gov, European Respiratory Society and American Thoracic Society databases. Two authors independently selected relevant randomized trials (parallel group or cross-over design), extracted data, assessed the risk of bias and rated the quality of the evidence. Results Eleven studies were included, involving 408 participants (8 full papers and 3 conference abstracts). Most studies had a high risk of bias or other methodological limitations. The use of NHF during a single session increased functional exercise capacity (SMD 0.36 (95% CI 0.03 to 0.69) p=0.03, heterogeneity (I² 83 %)). When conference abstracts were included in the pooled analysis, the estimated effect did not change (p=0.006). The use of NHF throughout a pulmonary rehabilitation programme (parallel group RCTs) increased functional exercise capacity at 4 to 12 weeks compared with those who trained without NHF (SMD 0.34 (95% CI 0.00 to 0.68) p=0.05, heterogeneity (I² 18%)). Conclusion There is very low to low quality evidence that NHF improves functional exercise capacity. Patient responses to NHF therapy were highly variable and heterogeneous, with benefits ranging from clinically trivial to worthwhile. Registration (www.crd.york.ac.uk/prospero: CRD42021221550).

High-flow nasal oxygen reduces endotracheal intubation: a randomized clinical trial

Background:

The benefits of high-flow nasal cannula (HFNC) as primary intervention in patients with acute hypoxemic respiratory failure (AHRF) are still a matter in debate. Our objective was to compare HFNC therapy versus conventional oxygen therapy (COT) in the prevention of endotracheal intubation in this group of patients.

Methods:

An open-label, controlled and single-centre clinical trial was conducted in patients with severe AHRF, defined by a PaO₂/FIO₂ ratio ⩽200, to compare HFNC with a control group (CG) treated by COT delivered through a face mask, with the need to perform intubation as the primary outcome. The secondary outcomes included tolerance of the HFNC device and to look for the predictive factors for intubation in these patients.

Results:

A total of 46 patients were included (22 in the COT group and 24 in the HFNC group) 48% of whom needed intubation: 63% in the COT group and 33% in the HFNC group, with significant differences both in intention to treat [χ² = 4.2; p = 0.04, relative risk (RR) = 0.5; confidence interval (CI) 95%: 0.3–1.0] and also in treatment analysis (χ² = 4.7; p = 0.03; RR = 0.5; IC 95%: 0.3–0.9) We obtained a number needed to treat (NNT) = 3 patients treated to avoid an intubation. Intubation occurred significantly later in the HFNC group. Estimated PaO₂/FIO₂, respiratory rate and dyspnea were significantly better in the HFNC group. Patients treated with HFNC who required intubation presented significant worsening after the first 8 h, as compared with non-intubated HFNC group patients. Mortality was 22% with no differences. The HFNC group patients were hospitalized for almost half of the time in the intensive care unit (ICU) and in the ward, with significantly less hospital length of stay. A total of 14 patients in the HFNC group (58%) complained of excessive heat and 17% of noise; 3 patients did not tolerate HFNC.

Conclusion:

Patients with severe acute hypoxemic respiratory failure who tolerate HFNC present a significantly lower need for endotracheal intubation compared with conventional oxygen therapy.

Clinical Trial Register

EUDRA CT number: 2012-001671-36

The reviews of this paper are available via the supplemental material section.

The Role of Noninvasive Respiratory Management in Patients with Severe COVID-19 Pneumonia

Acute hypoxemic respiratory failure is the principal cause of hospitalization, invasive mechanical ventilation and death in severe COVID-19 infection. Nearly half of intubated patients with COVID-19 eventually die. High-Flow Nasal Oxygen (HFNO) and Noninvasive Ventilation (NIV) constitute valuable tools to avert endotracheal intubation in patients with severe COVID-19 pneumonia who do not respond to conventional oxygen treatment. Sparing Intensive Care Unit beds and reducing intubation-related complications may save lives in the pandemic era. The main drawback of HFNO and/or NIV is intubation delay. Cautious selection of patients with severe hypoxemia due to COVID-19 disease, close monitoring and appropriate employment and titration of HFNO and/or NIV can increase the rate of success and eliminate the risk of intubation delay. At the same time, all precautions to protect the healthcare personnel from viral transmission should be taken. In this review, we summarize the evidence supporting the application of HFNO and NIV in severe COVID-19 hypoxemic respiratory failure, analyse the risks associated with their use and provide a path for their proper implementation.

Protocolized Postextubation Respiratory Support to Prevent Reintubation: A Randomized Clinical Trial

Rationale: Respiratory support (noninvasive ventilation or high-flow nasal cannula) applied at the time of extubation has been reported to reduce reintubation rates, but concerns regarding effectiveness have limited uptake into practice.Objectives: To determine if providing postextubation respiratory support to all patients undergoing extubation in a medical ICU would decrease the incidence of reintubation.Methods: We conducted a pragmatic, two-armed, cluster-crossover trial of adults undergoing extubation from invasive mechanical ventilation between October 1, 2017, and March 31, 2019, in the medical ICU of an academic medical center. Patients were assigned to either protocolized postextubation respiratory support (a respiratory therapist-driven protocol in which patients with suspected hypercapnia received noninvasive ventilation and patients without suspected hypercapnia received high-flow nasal cannula) or usual care (postextubation management at the discretion of treating clinicians). The primary outcome was reintubation within 96 hours of extubation.Measurements and Main Results: A total of 751 patients were enrolled. Of the 359 patients assigned to protocolized support, 331 (92.2%) received postextubation respiratory support compared with 66 of 392 patients (16.8%) assigned to usual care, a difference driven by differential use of high-flow nasal cannula (74.7% vs. 2.8%). A total of 57 patients (15.9%) in the protocolized support group experienced reintubation compared with 52 patients (13.3%) in the usual care group (odds ratio, 1.23; 95% confidence interval, 0.82 to 1.84; P = 0.32).Conclusions: Among a broad population of critically ill adults undergoing extubation from invasive mechanical ventilation at an academic medical center, protocolized postextubation respiratory support, primarily characterized by an increase in the use of high-flow nasal cannula, did not prevent reintubation compared with usual care.Clinical trial registered with www.clinicaltrials.gov (NCT0328831).

Comparison of Actual Performance in the Flow and Fraction of Inspired O2 among Different High-Flow Nasal Cannula Devices: A Bench Study

Background

High-flow nasal cannula (HFNC) oxygen therapy has been recommended for use in coronavirus disease 2019 (COVID-19) patients with acute respiratory failure and many other clinical conditions. HFNC devices produced by different manufacturers may have varied performance. Whether there is a difference in these devices and the extent of the differences in performance remain unknown.

Methods

Four HFNC devices (AIRVO 2, TNI softFlow 50, HUMID-BH, and OH-70C) and a ventilator with an HFNC module (bellavista 1000) were evaluated. The flow was set at 20, 25, 30, 35, 40, 45, 50, 60, 70, and 80 L/min, and the FiO₂ was set at 21%, 26%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, and 90%. Then, one side of the cannulas was clipped to simulate the compression, bending, or blocking of the nasal cannulas. The flow and FiO₂ of the delivered gas were recorded and compared among settings and devices.

Results

The actual-flow and actual-FiO₂ delivered by different settings and devices varied. AIRVO 2 had superior performance in flow and FiO₂ accuracy. bellavista 1000 and OH-70C had good performance in the accuracy of actual-flows and actual-FiO_2, respectively. bellavista 1000 and HUMID-BH had a larger flow range from 10 to 80 L/min, but only bellavista 1000 could provide a stable flow with an excessive resistance up to 60 L/min. TNI softFlow 50 had the best flow compensation and could provide sufficient flow with excessive resistance at 20–50 L/min.

Conclusions

The variation in flow, FiO₂ settings, and devices could influence the actual-flow and actual-FiO₂ delivered. AIRVO 2 and OH-70C showed better FiO₂ accuracy. TNI softFlow 50, bellavista 1000, and HUMID-BH could lower the risk of insufficient flow support due to accidental compression or blocking of the cannulas. In addition, ventilators with HFNC modules provided comparable flow and FiO₂ and could be an alternative to standalone HFNC devices.

Predicting nasal high-flow therapy failure by pediatric respiratory rate-oxygenation index and pediatric respiratory rate-oxygenation index variation in children

The primary objective of this study was to evaluate whether pediatric respiratory rate-oxygenation index (p-ROXI) and variation in p-ROXI (p-ROXV) can serve as objective markers in children with high-flow nasal cannula (HFNC) failure. In this prospective, single-center observational study, all patients who received HFNC therapy in the general pediatrics ward, pediatric intensive care unit, and the pediatric emergency department were included. High-flow nasal cannula success was achieved for 116 (88.5%) patients. At 24 h, if both p-ROXI and p-ROXV values were above the cutoff point (≥ 66.7 and ≥ 24.0, respectively), HFNC failure was 1.9% and 40.6% if both were below their values (p < 0.001). At 48 h of HFNC initiation, if both p-ROXI and p-ROXV values were above the cutoff point (≥ 65.1 and ≥ 24.6, respectively), HFNC failure was 0.0%; if both were below these values, HFNC failure was 100% (p < 0.001).Conclusion: We observed that these parameters can be used as good markers in pediatric clinics to predict the risk of HFNC failure in patients with acute respiratory failure. What is Known: • Optimal timing for transitions between invasive and noninvasive ventilation strategies is of significant importance. • The complexity of data requires an objective marker that can be evaluated quickly and easily at the patient's bedside for predicting HFNC failure in children with acute respiratory failure. What is New: • Our data showed that combining p-ROXI and p-ROXV can be successful in predicting HFNC failure at 24 and 48 h of therapy.

Noninvasive ventilation and high-flow oxygen therapy for severe community-acquired pneumonia

PURPOSE OF REVIEW

We review the evidence on the use of noninvasive respiratory supports (noninvasive ventilation and high-flow nasal cannula oxygen therapy) in patients with acute respiratory failure because of severe community-acquired pneumonia.

RECENT FINDINGS

Noninvasive ventilation is strongly advised for the treatment of hypercapnic respiratory failure and recent evidence justifies its use in patients with hypoxemic respiratory failure when delivered by helmet. Indeed, such interface allows alveolar recruitment by providing high level of positive end-expiratory pressure, which improves hypoxemia. On the other hand, high-flow nasal cannula oxygen therapy is effective in patients with hypoxemic respiratory failure and some articles support its use in patients with hypercapnia. However, early identification of noninvasive respiratory supports treatment failure is crucial to prevent delayed orotracheal intubation and protective invasive mechanical ventilation.

SUMMARY

Noninvasive ventilation is the first-line therapy in patients with acute hypercapnic respiratory failure because of pneumonia. Although an increasing amount of evidence investigated the application of noninvasive respiratory support to hypoxemic respiratory failure, the optimal ventilatory strategy in this setting is uncertain. Noninvasive mechanical ventilation delivered by helmet and high-flow nasal cannula oxygen therapy appear as promising tools but their role needs to be confirmed by future research.

Initial setting of high-flow nasal oxygen post extubation based on mean inspiratory flow during a spontaneous breathing trial

PURPOSE

High flow nasal cannula (HFNC) is commonly used post-extubation in intensive care (ICU). Patients' comfort during HFNC is affected by flow rate. The study aims to describe the relationship between pre-extubation inspiratory flow requirements and the post-extubation flow rates on HFNC that maximises patient's comfort.

METHODS

This was an observational, retrospective study conducted in a university-affiliated ICU. We included patients extubated following successful spontaneous breathing trial (SBT). During the SBT we recorded variables including inspiratory flow. Patients who passed the SBT were extubated onto HFNC. HFNC was titrated from 20 L/min and increased in steps of 10 L/min, up to 60 L/min. At each step, patient's level of comfort was assessed. Fraction of inspired oxygen was titrated to maintain oxygen saturation 92-97%.

RESULTS

Nineteen participants were enrolled in the study. There was a significant positive correlation between mean inspiratory flow pre-extubation and the flow setting on HFNC which achieved the best comfort post-extubation (r² 0.88; p < 0.001). Overall, greatest comfort was observed for HFNC flows between 30 and 40 L/min but with individual variability.

CONCLUSION

Measuring mean inspiratory flow during an SBT allows for individualised setting of HFNC flow rate immediately post-extubation and achieves the greatest comfort and interface tolerance.

Impact of flow and temperature on non-dyspnoeic dogs' tolerance undergoing high-flow oxygen therapy

OBJECTIVES

To prospectively describe the impact of gas flow rate and temperature on dog's tolerance of high-flow nasal oxygen therapy during recovery from anaesthesia, hypothesizing that higher flow rates and temperatures will decrease tolerance.

MATERIALS AND METHODS

Twelve non-dyspnoeic client-owned dogs recovering from general anaesthesia were included in this study. After extubation, a nasal cannula was positioned and high-flow nasal oxygen therapy was initiated. Two flow rates (two or four time the theoretical minute ventilation: HF2 and HF4), each of them combined with two temperatures (31 and 37°C: T31 and T37), were randomly applied (four conditions per dog). For each condition, cardiovascular and respiratory parameters (heart rate, respiratory rate, systolic arterial blood pressure and pulse oximeter oxygen saturation), sedation score and tolerance score were recorded at initiation (T₀ ) and after 10 minutes of accommodation (T₁₀ ).

RESULTS

Sedation scores were not significantly different between the four conditions. Cardiovascular and respiratory parameters were not significantly different between any condition at both T₀ and T₁₀ . Tolerance scores were good and not significantly different between any flow rate or temperature (HF2-T31: 4 (2-4), HF4-T31: 4 (2-4), HF2-T37: 4 (2-4), HF4-T37: 4 (1-4)).

CLINICAL SIGNIFICANCE

The gas flow rates and temperatures studied have no impact on tolerance during the recovery period of non-dyspnoeic dogs, and high-flow nasal cannula is well tolerated. Further studies are required to confirm these results in dyspnoeic dogs.

High-Flow Nasal Cannula Therapy for Exertional Dyspnea in Patients with Cancer: A Pilot Randomized Clinical Trial

BACKGROUND

Exertional dyspnea is common in patients with cancer and limits their function. The impact of high-flow nasal cannula on exertional dyspnea in nonhypoxemic patients is unclear. In this double-blind, parallel-group, randomized trial, we assessed the effect of flow rate (high vs. low) and gas (oxygen vs. air) on exertional dyspnea in nonhypoxemic patients with cancer.

PATIENTS AND METHODS

Patients with cancer with oxygen saturation >90% at rest and exertion completed incremental and constant work (80% maximal) cycle ergometry while breathing low-flow air at 2 L/minute. They were then randomized to receive high-flow oxygen, high-flow air, low-flow oxygen, or low-flow air while performing symptom-limited endurance cycle ergometry at 80% maximal. The primary outcome was modified 0-10 Borg dyspnea intensity scale at isotime. Secondary outcomes included dyspnea unpleasantness, exercise time, and adverse events.

RESULTS

Seventy-four patients were enrolled, and 44 completed the study (mean age 63; 41% female). Compared with low-flow air at baseline, dyspnea intensity was significantly lower at isotime with high-flow oxygen (mean change, -1.1; 95% confidence interval [CI], -2.1, -0.12) and low-flow oxygen (-1.83; 95% CI, -2.7, -0.9), but not high-flow air (-0.2; 95% CI, -0.97, 0.6) or low-flow air (-0.5; 95% CI, -1.3, 0.4). Compared with low-flow air, high-flow oxygen also resulted in significantly longer exercise time (difference + 2.5 minutes, p = .009), but not low-flow oxygen (+0.39 minutes, p = .65) or high-flow air (+0.63 minutes, p = .48). The interventions were well tolerated without significant adverse effects.

CONCLUSION

Our preliminary findings support that high-flow oxygen improved both exertional dyspnea and exercise duration in nonhypoxemic patients with cancer. (ClinicalTrials.gov ID: NCT02357134).

IMPLICATIONS FOR PRACTICE

In this four-arm, double-blind, randomized clinical trial examining the role of high-flow nasal cannula on exertional dyspnea in patients with cancer without hypoxemia, high-flow oxygen, but not high-flow air, resulted in significantly lower dyspnea scores and longer exercise time. High-flow oxygen delivered by high-flow nasal cannula devices may improve clinically relevant outcomes even in patients without hypoxemia.

[Guideline for Long-Term Oxygen Therapy - S2k-Guideline Published by the German Respiratory Society]

Long-term oxygen therapy is of great importance both for reducing mortality and for improving performance in patients with chronic lung diseases. The prerequisites for Long-term oxygen therapy are adequate diagnostics and clearly defined indication. A causal distinction into chronic hypoxaemic and hypercapnic respiratory failure is reasonable, from which the differential indication for non-invasive ventilation results.The revised guideline covers the diagnostics and indication of chronic lung and heart diseases, the role of oxygen in terminal illness and gives a detailed description of available oxygen devices. The guideline is intended to help avoid undersupply, oversupply and false prescriptions. Furthermore, the chapter "Postacute Oxygen Therapy" discusses the procedure, relevant in everyday life, but not yet clearly defined, for prescribing oxygen therapy for the home at the end of an inpatient stay. Another important point, the correct prescription of mobile oxygen systems, is also presented in the guideline. This document is a revised version of the guideline for longterm oxygen therapy and replaces the version of 2008.

Nasal high flow higher than 60 L/min in patients with acute hypoxemic respiratory failure: a physiological study

Background

Nasal high flow delivered at flow rates higher than 60 L/min in patients with acute hypoxemic respiratory failure might be associated with improved physiological effects. However, poor comfort might limit feasibility of its clinical use.

Methods

We performed a prospective randomized cross-over physiological study on 12 ICU patients with acute hypoxemic respiratory failure. Patients underwent three steps at the following gas flow: 0.5 L/kg PBW/min, 1 L/kg PBW/min, and 1.5 L/kg PBW/min in random order for 20 min. Temperature and FiO₂ remained unchanged. Toward the end of each phase, we collected arterial blood gases, lung volumes, and regional distribution of ventilation assessed by electrical impedance tomography (EIT), and comfort.

Results

In five patients, the etiology was pulmonary; infective disease characterized seven patients; median PaO₂/FiO₂ at enrollment was 213 [IQR 136–232]. The range of flow rate during NHF 1.5 was 75–120 L/min. PaO₂/FiO₂ increased with flow, albeit non significantly (p = 0.064), PaCO₂ and arterial pH remained stable (p = 0.108 and p = 0.105). Respiratory rate decreased at higher flow rates (p = 0.014). Inhomogeneity of ventilation decreased significantly at higher flows (p = 0.004) and lung volume at end-expiration significantly increased (p = 0.007), but mostly in the non-dependent regions. Comfort was significantly poorer during the step performed at the highest flow (p < 0.001).

Conclusions

NHF delivered at rates higher than 60 L/min in critically ill patients with acute hypoxemic respiratory failure is associated with reduced respiratory rate, increased lung homogeneity, and additional positive pressure effect, but also with worse comfort.

Use of nasal high flow oxygen during acute respiratory failure

Nasal high flow (NHF) has gained popularity among intensivists to manage patients with acute respiratory failure. An important literature has accompanied this evolution. In this review, an international panel of experts assessed potential benefits of NHF in different areas of acute respiratory failure management. Analyses of the physiological effects of NHF indicate flow-dependent improvement in various respiratory function parameters. These beneficial effects allow some patients with severe acute hypoxemic respiratory failure to avoid intubation and improve their outcome. They require close monitoring to not delay intubation. Such a delay may worsen outcome. The ROX index may help clinicians decide when to intubate. In immunocompromised patients, NHF reduces the need for intubation but does not impact mortality. Beneficial physiological effects of NHF have also been reported in patients with chronic respiratory failure, suggesting a possible indication in acute hypercapnic respiratory failure. When intubation is required, NHF can be used to pre-oxygenate patients either alone or in combination with non-invasive ventilation (NIV). Similarly, NHF reduces reintubation alone in low-risk patients and in combination with NIV in high-risk patients. NHF may be used in the emergency department in patients who would not be offered intubation and can be better tolerated than NIV.