Subjective effects of humidification of oxygen for delivery by nasal cannula. A prospective study

Linear versus Turbulent Airflow Tracheostomy Heat and Moisture Exchangers: A Crossover Study

OBJECTIVE

This study aimed to evaluate the impact of two tracheostomy heat and moisture exchangers (HMEs), namely the Shikani Oxygen HME™ (S-O2 HME, ball type, turbulent airflow) and Mallinckrodt Tracheolife II DAR HME (M-O2 HME; flapper type, linear airflow) on tracheobronchial mucosal health, oxygenation, humidification, and patient preference.

METHODS

A randomized cross-over study was conducted with HME-naïve long-term tracheostomy subjects at two academic medical centers. Bronchoscopy assessments of mucosal health were performed at baseline and day 5 of HME application, along with oxygen saturation (SpO2 ) and breathed air humidity at four oxygen flow rates (1, 2, 3, and 5 lpm). Patient preference was assessed on study conclusion.

RESULTS

Both HMEs were associated with improved mucosal inflammation and decreased mucus production (p < 0.0002), with greater improvements in the S-O2 HME group (p < 0.007). Both HMEs improved humidity concentration at each oxygen flow rate (p < 0.0001), without significant differences between groups. SpO2 was greater for the S-O2 HME versus the M-O2 HME across all measured oxygen flow rates (p = 0.003). At low oxygen flow rates (1 or 2 lpm), the SpO2 in the S-O2 HME group was similar to that of the M-O2 HME at higher oxygen flow rates (3 or 5 lpm; p = 0.6). Ninety percent of subjects preferred the S-O2 HME.

CONCLUSION

Tracheostomy HME uses correlated with improved indicators of tracheobronchial mucosal health, humidity, and oxygenation. The S-O2 HME outperformed the M-O2 HME with respect to tracheobronchial inflammation, SpO2 , and patient preference. Regular HME use by tracheostomy patients is recommended to optimize pulmonary health. Newer ball-type speaking valve technology additionally allows concomitant HME and speaking valve application.

LEVEL OF EVIDENCE

2 Laryngoscope, 133:3422-3428, 2023.

Humidified versus nonhumidified low-flow oxygen therapy in children with Pierre-Robin syndrome: A randomized controlled trial

BACKGROUND

Humidification is an important process in clinical oxygen therapy. We aimed to evaluate the effects and safety of humidified versus nonhumidified low-flow oxygen therapy in children with Pierre-Robin syndrome.

METHODS

This study was an open-label, single-centered randomized controlled trial (RCT) with a parallel group design. The study protocol has been registered in Chinese Clinical Trial Registry (ChiCTR1900021584). The children were randomized to the humidified versus nonhumidified groups. Average arterial oxygen partial pressure (PaO2) and carbon dioxide partial pressure (PaCO2), incidence of ventilator-associated pneumonia (VAP), nasal cavity dryness, nasal mucosal bleeding and bacterial contamination of the humidified bottle, the cost of nasal oxygen therapy and duration of intensive care unit (ICU) stay were analyzed.

RESULTS

A total of 213 children with Pierre-Robin syndrome were included. There were no significant differences in the gender, age, weight, prematurity, duration of anesthesia and surgery duration of mandibular traction between humidified group and nonhumidified group (all P > .05). No significant differences in the average arterial PaO2 and PaCO2 level on the postoperative day 1, 2, and ICU discharge between humidified group and nonhumidified group were found (all P > .05). There were no significant differences in the incidence of nasal cavity dryness, nasal mucosal bleeding, bacterial contamination and VAP, the duration of ICU stay between humidified group and nonhumidified group (all P > .05). The cost of nasal oxygen therapy in the humidified group was significantly less than that of nonhumidified group (P = .013).

CONCLUSIONS

Humidifying the oxygen with cold sterile water in the low-flow oxygen therapy in children may be not necessary. Future RCTs with lager sample size and rigorous design are warranted to further elucidate the effects and safety of humidified versus nonhumidified low-flow oxygen therapy.

An On-Demand Oxygen Flow Meter for Enhanced Patient Comfort and Reduced Oxygen Cost in Hospitals

Background: Hypoxemia is currently treated in hospital wards with oxygen, released continuously by "conventional" flow meters. A new type of hybrid flow meter allows to switch between on-demand and continuous mode. The aim of this observational study was to assess whether this new device reduces oxygen expenditure, is well accepted in a hospital setting and improves patient comfort during oxygen therapy. Methods: Oxygen was administered in hypoxemic patients with conventional or hybrid flow meters to maintain an oxygen saturation of ≥ 92% over a 12-week period. Every two weeks conventional and hybrid flow meters were switched. The overall oxygen delivery to the ward was continuously measured with a data logging device installed in the main oxygen pipeline and corrected for multiple confounding factors. Humidity measurements, for which a sensor placed in front of one of the nostrils, and patient questionnaires, were used to assess patient comfort during continuous and on-demand flow. Results: Overall oxygen delivery decreased by 39% when switching from continuous flow to on-demand therapy after correction for confounding factors. Continuous flows significantly decreased relative humidity more than equivalent on-demand settings and the latter tended to increase comfort. Conclusions: Hybrid flow meters cause a significant reduction in oxygen delivery in a hospital ward, which may lead to financial savings. Using the on-demand technology also lowers the dryness of the upper airways (and may increase patient comfort), while maintaining an adequate oxygenation.

High-flow nasal cannula for respiratory failure in adult patients

The high-flow nasal cannula (HFNC) has been recently used in several clinical settings for oxygenation in adults. In particular, the advantages of HFNC compared with low-flow oxygen systems or non-invasive ventilation include enhanced comfort, increased humidification of secretions to facilitate expectoration, washout of nasopharyngeal dead space to improve the efficiency of ventilation, provision of a small positive end-inspiratory pressure effect, and fixed and rapid delivery of an accurate fraction of inspired oxygen (FiO₂) by minimizing the entrainment of room air. HFNC has been successfully used in critically ill patients with several conditions, such as hypoxemic respiratory failure, hypercapneic respiratory failure (exacerbation of chronic obstructive lung disease), post-extubation respiratory failure, pre-intubation oxygenation, and others. However, the indications are not absolute, and much of the proven benefit remains subjective and physiologic. This review discusses the practical application and clinical uses of HFNC in adults, including its unique respiratory physiologic effects, device settings, and clinical indications.

Treatment of acute respiratory failure: high-flow nasal cannula

Background: High-flow nasal cannulas (HFNCs) have recently been used for several conditions, such as hypoxemic respiratory failure, hypercapnic respiratory failure, post-extubation respiratory failure, and preintubation oxygenation, in critically ill patients.Current Concepts: The advantages of HFNC compared with those of low-flow oxygen systems or noninvasive ventilation include enhanced comfort, increased humidification of secretions to facilitate expectoration, washout of the nasopharyngeal dead space to improve ventilation efficiency, provisioning for low positive end-inspiratory pressure effect, and fixed and rapid delivery of accurate fraction of inspired oxygen by minimizing the entrainment of room air. However, the indications are not absolute, with much of the proven benefit being subjective and physiologic.Discussion and Conclusion: The goal of this review is to discuss the practical application and clinical uses of HFNCs in patients with acute respiratory failure, highlighting its unique respiratory and physiologic effects, device settings, and clinical indications.

High Flow Nasal Cannula Therapy in the Emergency Department: Main Benefits in Adults, Pediatric Population and against COVID-19: A Narrative Review

This review aims to summarize the literature’s main results about high flow nasal cannula therapy (HFNC) HFNC benefits in the Emergency Department (ED) in adults and pediatrics, including new Coronavirus Disease (COVID-19). HFNC has recently been established as the usual treatment in the ED to provide oxygen support. Its use has been generalized due to its advantages over traditional oxygen therapy devices, including decreased nasopharyngeal resistance, washing out of the nasopharyngeal dead space, generation of positive pressure, increasing alveolar recruitment, easy adaptation due to the humidification of the airways, increased fraction of inspired oxygen and improved mucociliary clearance. A wide range of pathologies has been studied to evaluate the potential benefits of HFNC; some examples are heart failure, pneumonia, chronic pulmonary obstructive disease, asthma, and bronchiolitis. The regular use of this oxygen treatment is not established yet due to the literature’s controversial results. However, several authors suggest that it could be useful in several pathologies that generate acute respiratory failure. Consequently, the COVID-19 irruption has generated the question of HFNC as a safety and effective treatment. Our results suggested that HFNC seems to be a useful tool in the ED, especially in patients affected by acute hypoxemic respiratory failure, acute heart failure, pneumonia, bronchiolitis, asthma and acute respiratory distress syndrome in patients affected by COVID-19. Its benefits in hypercapnic respiratory failure are more discussed, being only observed benefits in patients with mild-moderate disease. These results are based in clinical as well as cost-effectiveness outcomes. Future studies with largest populations are required to confirm these results as well as establish a practical guideline to use this device.

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.

Assessment of the Use of Humidified Nasal Cannulas for Oxygen Therapy in Patients with Epistaxis

INTRODUCTION

In China, nasal cannula oxygen therapy is typically humidified. However, it is difficult to decide whether to suspend nasal cannula oxygen inhalation after the nosebleed has temporarily stopped. Therefore, we conducted a preliminary investigation on whether the use of humidified nasal cannulas in our hospital increases the incidence of epistaxis.

METHODS

We conducted a survey of 176,058 inpatients in our hospital and other city branches of our hospital over the past 3 years and obtained information concerning their use of humidified nasal cannulas for oxygen inhalation, nonhumidified nasal cannulas, anticoagulant and antiplatelet drugs, and oxygen inhalation flow rates. This information was compared with the data collected at consultation for epistaxis during these 3 years.

RESULTS

No significant difference was found between inpatients with humidified nasal cannulas and those without nasal cannula oxygen therapy in the incidence of consultations due to epistaxis (χ2 = 1.007, p > 0.05). The same trend was observed among hospitalized patients using anticoagulant and antiplatelet drugs (χ2 = 2.082, p > 0.05). Among the patients with an inhaled oxygen flow rate ≥5 L/min, the incidence of ear-nose-throat (ENT) consultations due to epistaxis was 0. No statistically significant difference was found between inpatients with a humidified oxygen inhalation flow rate <5 L/min and those without nasal cannula oxygen therapy in the incidence of ENT consultations due to epistaxis (χ2 = 0.838, p > 0.05). A statistically significant difference was observed in the incidence of ENT consultations due to epistaxis between the low-flow nonhumidified nasal cannula and nonnasal cannula oxygen inhalation groups (χ2 = 18.428, p < 0.001). The same trend was observed between the 2 groups of low-flow humidified and low-flow nonhumidified nasal cannula oxygen inhalation (χ2 = 26.194, p < 0.001).

DISCUSSION/CONCLUSION

Neither high-flow humidified nasal cannula oxygen inhalation nor low-flow humidified nasal cannula oxygen inhalation will increase the incidence of recurrent or serious epistaxis complications; the same trend was observed for patients who use anticoagulant and antiplatelet drugs. Humidification during low-flow nasal cannula oxygen inhalation can prevent severe and repeated epistaxis to a certain extent.

Cold bubble humidification of low-flow oxygen does not prevent acute changes in inflammation and oxidative stress at nasal mucosa

Some clinical situations require the use of oxygen therapy for a few hours without hypoxemia. However, there are no literature reports on the effects of acute oxygen therapy on the nasal mucosa. This study aimed to evaluate the acute effects of cold bubble humidification or dry oxygen on nasal Inflammation, oxidative stress, mucociliary clearance, and nasal symptoms. This is a randomized controlled cross-sectional study in which healthy subjects were randomly allocated into four groups: (1) CA + DRY (n = 8): individuals receiving dry compressed air; (2) OX + DRY (n = 8): individuals receiving dry oxygen therapy; (3) CA + HUMID (n = 7): individuals receiving cold bubbled humidified compressed air; (4) OX + HUMID (n = 8): individuals receiving cold bubbled humidified oxygen therapy. All groups received 3 L per minute (LPM) of the oxygen or compressed air for 1 h and were evaluated: total and differential cells in the nasal lavage fluid (NLF), exhaled nitric oxide (eNO), 8-iso-PGF2α levels, saccharin transit test, nasal symptoms, and humidity of nasal cannula and mucosa. Cold bubble humidification is not able to reduced nasal inflammation, eNO, oxidative stress, mucociliary clearance, and nasal mucosa moisture. However, subjects report improvement of nasal dryness symptoms (P < 0.05). In the conclusion, cold bubble humidification of low flow oxygen therapy via a nasal cannula did not produce any effect on the nasal mucosa and did not attenuate the oxidative stress caused by oxygen. However, it was able to improve nasal symptoms arising from the use of oxygen therapy.

High Flow Oxygen Therapy at Two Initial Flow Settings versus Conventional Oxygen Therapy in Cardiac Surgery Patients with Postextubation Hypoxemia: A Single-Center, Unblinded, Randomized, Controlled Trial

In cardiac surgery patients with pre-extubation PaO₂/inspired oxygen fraction (FiO₂) < 200 mmHg, the possible benefits and optimal level of high-flow nasal cannula (HFNC) support are still unclear; therefore, we compared HFNC support with an initial gas flow of 60 or 40 L/min and conventional oxygen therapy. Ninety nine patients were randomly allocated (respective ratio: 1:1:1) to I = intervention group 1 (HFNC initial flow = 60 L/min, FiO₂ = 0.6), intervention group 2 (HFNC initial flow = 40 L/min, FiO₂ = 0.6), or control group (Venturi mask, FiO₂ = 0.6). The primary outcome was occurrence of treatment failure. The baseline characteristics were similar. The hazard for treatment failure was lower in intervention group 1 vs. control (hazard ratio (HR): 0.11, 95% CI: 0.03–0.34) and intervention group 2 vs. control (HR: 0.30, 95% CI: 0.12–0.77). During follow-up, the probability of peripheral oxygen saturation (SpO₂) > 92% and respiratory rate within 12–20 breaths/min was 2.4–3.9 times higher in intervention group 1 vs. the other 2 groups. There was no difference in PaO₂/FiO₂, patient comfort, intensive care unit or hospital stay, or clinical course complications or adverse events. In hypoxemic cardiac surgery patients, postextubation HFNC with an initial gas flow of 60 or 40 L/min resulted in less frequent treatment failure vs. conventional therapy. The results in terms of SpO₂/respiratory rate targets favored an initial HFNC flow of 60 L/min.

Effect on comfort of administering bubble-humidified or dry oxygen: the Oxyrea non-inferiority randomized study

BACKGROUND

The clinical interest of using bubble humidification of oxygen remains controversial. This study was designed to further explore whether delivering dry oxygen instead of bubble-moistened oxygen had an impact on discomfort of ICU patients.

METHODS

This randomized multicenter non-inferiority open trial included patients admitted in intensive care unit and receiving oxygen. Any patient receiving non-humidified oxygen (between 0 and 15 L/min) for less than 2 h could participate in the study. Randomization was stratified based on the flow rate at inclusion (less or more than 4 L/min). Discomfort was assessed 6-8 and 24 h after inclusion using a dedicated 15-item scale (quoted from 0 to 150).

RESULTS

Three hundred and fifty-four ICU patients receiving non-humidified oxygen were randomized either in the humidified (HO) (n = 172), using bubble humidifiers, or in the non-humidified (NHO) (n = 182) arms. In modified intention-to-treat analysis at H6-H8, the 15-item score was 26.6 ± 19.4 and 29.8 ± 23.4 in the HO and NHO groups, respectively. The absolute difference between scores in both groups was 3.2 [90% CI 0.0; + 6.5] for a non-inferiority margin of 5.3, meaning that the non-inferiority analysis was not conclusive. This was also true for the subgroups of patients receiving either less or more than 4 L/min of oxygen. At H24, using NHO was not inferior compared to HO in the general population and in the subgroup of patients receiving 4 L/min or less of oxygen. However, for patients receiving more than 4 L/min, a post hoc superiority analysis suggested that patients receiving dry oxygen were less comfortable.

CONCLUSIONS

Oxygen therapy-related discomfort was low. Dry oxygen could not be demonstrated as non-inferior compared to bubble-moistened oxygen after 6-8 h of oxygen administration. At 24 h, dry oxygen was non-inferior compared to bubble-humidified oxygen for flows below 4 L/min.

High-flow nasal oxygen vs. standard oxygen therapy in immunocompromised patients with acute respiratory failure: study protocol for a randomized controlled trial

Background

Acute respiratory failure (ARF) is the leading reason for intensive care unit (ICU) admission in immunocompromised patients. High-flow nasal oxygen (HFNO) therapy is an alternative to standard oxygen. By providing warmed and humidified gas, HFNO allows the delivery of higher flow rates via nasal cannula devices, with FiO₂ values of nearly 100%. Benefits include alleviation of dyspnea and discomfort, decreased respiratory distress and decreased mortality in unselected patients with acute hypoxemic respiratory failure. However, in preliminary reports, HFNO benefits are controversial in immunocompromised patients in whom it has never been properly evaluated.

Methods/design

This is a multicenter, open-label, randomized controlled superiority trial in 30 intensive care units, part of the Groupe de Recherche Respiratoire en Réanimation Onco-Hématologique (GRRR-OH). Inclusion criteria will be: (1) adults, (2) known immunosuppression, (3) ARF, (4) oxygen therapy ≥ 6 L/min, (5) written informed consent from patient or proxy. Exclusion criteria will be: (1) imminent death (moribund patient), (2) no informed consent, (3) hypercapnia (PaCO₂ ≥ 50 mmHg), (4) isolated cardiogenic pulmonary edema, (5) pregnancy or breastfeeding, (6) anatomical factors precluding insertion of a nasal cannula, (7) no coverage by the French statutory healthcare insurance system, and (8) post-surgical setting from day 1 to day 6 (patients with ARF occurring after day 6 of surgery can be included).

The primary outcome measure is day-28 mortality. Secondary outcomes are intubation rate, comfort, dyspnea, respiratory rate, oxygenation, ICU length of stay, and ICU-acquired infections.

Based on an expected 30% mortality rate in the standard oxygen group, and 20% in the HFNO group, error rate set at 5%, and a statistical power at 90%, 389 patients are required in each treatment group (778 patients overall). Recruitment period is estimated at 30 months, with 28 days of additional follow-up for the last included patient.

Discussion

The HIGH study will be the largest multicenter, randomized controlled trial seeking to demonstrate that survival benefits from HFNO reported in unselected patients also apply to a large immunocompromised population.

Trial registration

ClinicalTrials.gov, ID: NCT02739451. Registered on 15 April 2016.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2492-z) contains supplementary material, which is available to authorized users.

Humidification of Blow-By Oxygen During Recovery of Postoperative Pediatric Patients: One Unit's Journey

PURPOSE

To examine the practice of nebulizer cool mist blow-by oxygen administered to spontaneously breathing postanesthesia care unit (PACU) pediatric patients during Phase one recovery.

DESIGN

Existing evidence was evaluated. Informal benchmarking documented practices in peer organizations. An in vitro study was then conducted to simulate clinical practice and determine depth and amount of airway humidity delivery with blow-by oxygen.

METHODS

Informal benchmarking information was obtained by telephone interview. Using a three-dimensional printed simulation model of the head connected to a breathing lung simulator, depth and amount of moisture delivery in the respiratory tree were measured.

FINDINGS

Evidence specific to PACU administration of cool mist blow-by oxygen was limited. Informal benchmarking revealed that routine cool mist oxygenated blow-by administration was not widely practiced. The laboratory experiment revealed minimal moisture reaching the mid-tracheal area of the simulated airway model.

CONCLUSIONS

Routine use of oxygenated cool mist in spontaneously breathing pediatric PACU patients is not supported.

Is humidified better than non-humidified low-flow oxygen therapy? A systematic review and meta-analysis

AIMS

To determine the effects of low-flow oxygen therapy with humidified or non-humidified oxygen in adult patients.

BACKGROUND

Although non-humidified oxygen in low-flow oxygen therapy is recommended by many guidelines, humidifying oxygen regardless of oxygen flow has been routinely performed in China and Japan and further studies are needed to evaluate the evidence.

DESIGN

A systematic review and meta-analysis that comply with the recommendations of the Cochrane Collaboration were conducted.

DATA SOURCES

Studies (1980-2016) were identified by searching PUBMED, EMBASE, Science Direct, Cochrane library, CNKI and Wanfang Database.

METHODS

We performed a comprehensive, systematic meta-analysis of randomized controlled trials on the efficacy of humidified and non-humidified low-flow oxygen therapy. Summary risk ratios or weighted mean differences with 95% confidence intervals were calculated using a fixed- or random-effects model.

RESULTS

Twenty-seven randomized controlled trials with a total number of 8,876 patients were included. Non-humidified oxygen offers more benefits in reducing the bacterial contamination of humidifier bottles, as shown by the mean operating time for oxygen administration and the respiratory infections compared with humidified oxygen therapy. No significant differences were found in dry nose, dry nose and throat, nosebleed, chest discomfort, the smell of oxygen and SpO₂ changes.

CONCLUSIONS

The routine humidification of oxygen in low-flow oxygen therapy is not justifiable and non-humidified oxygen tends to be more beneficial. However, considering that the quality of most included studies is poor, rigorously designed, large-scale randomized controlled trials are still needed to identify the role of non-humidified oxygen therapy.

Oxygen With Cold Bubble Humidification Is No Better Than Dry Oxygen in Preventing Mucus Dehydration, Decreased Mucociliary Clearance, and Decline in Pulmonary Function

BACKGROUND

Little is known about the effects of long-term nasal low-flow oxygen (NLFO) on mucus and symptoms and how this variable is affected by dry or cold humidified gas. The aim of this study was to investigate the effects of dry-NLFO and cold bubble humidified-NLFO on nasal mucociliary clearance (MCC), mucus properties, inflammation, and symptoms in subjects with chronic hypoxemia requiring long-term domiciliary oxygen therapy.

METHODS

Eighteen subjects (mean age, 68 years; 7 male; 66% with COPD) initiating NLFO were randomized to receive dry-NLFO (n = 10) or humidified-NLFO (n = 8). Subjects were assessed at baseline, 12 h, 7 days, 30 days, 12 months, and 24 months by measuring nasal MCC using the saccharin transit test, mucus contact angle (surface tension), inflammation (cells and cytokine concentration in nasal lavage), and symptoms according to the Sino-Nasal Outcome Test-20.

RESULTS

Nasal MCC decreased significantly (40% longer saccharin transit times) and similarly in both groups over the study period. There was a significant association between impaired nasal MCC and decline in lung function. Nasal lavage revealed an increased proportion of macrophages, interleukin-8, and epidermal growth factor concentrations with decreased interleukin-10 during the study. No changes in the proportion of ciliated cells or contact angle were observed. Coughing and sleep symptoms decreased similarly in both groups. There were no outcome differences comparing dry vs cold bubble humidified NLFO.

CONCLUSIONS

In subjects receiving chronic NLFO, cold bubble humidification does not adequately humidify inspired oxygen to prevent deterioration of MCC, mucus hydration, and pulmonary function. The unheated bubble humidification performed no better than no humidification.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT02515786; URL: www.clinicaltrials.gov.

High-flow nasal cannula oxygen therapy in adults

High-flow nasal cannula (HFNC) oxygen therapy comprises an air/oxygen blender, an active humidifier, a single heated circuit, and a nasal cannula. It delivers adequately heated and humidified medical gas at up to 60 L/min of flow and is considered to have a number of physiological effects: reduction of anatomical dead space, PEEP effect, constant fraction of inspired oxygen, and good humidification. While there have been no big randomized clinical trials, it has been gaining attention as an innovative respiratory support for critically ill patients. Most of the available data has been published in the neonatal field. Evidence with critically ill adults are poor; however, physicians apply it to a variety of patients with diverse underlying diseases: hypoxemic respiratory failure, acute exacerbation of chronic obstructive pulmonary disease, post-extubation, pre-intubation oxygenation, sleep apnea, acute heart failure, patients with do-not-intubate order, and so on. Many published reports suggest that HFNC decreases breathing frequency and work of breathing and reduces needs of escalation of respiratory support in patients with diverse underlying diseases. Some important issues remain to be resolved, such as its indication, timing of starting and stopping HFNC, and escalating treatment. Despite these issues, HFNC oxygen therapy is an innovative and effective modality for the early treatment of adults with respiratory failure with diverse underlying diseases.

High-flow nasal cannula: recommendations for daily practice in pediatrics

High-flow nasal cannula (HFNC) is a relatively new device for respiratory support. In pediatrics, HFNC use continues to increase as the system is easily set up and is well tolerated by patients. The use of nasal cannula adapted to the infant’s nares size to deliver heated and humidified gas at high flow rates has been associated with improvements in washout of nasopharyngeal dead space, lung mucociliary clearance, and oxygen delivery compared with other oxygen delivery systems. HFNC may also create positive pharyngeal pressure to reduce the work of breathing, which positions the device midway between classical oxygen delivery systems, like the high-concentration face mask and continuous positive airway pressure (CPAP) generators. Currently, most of the studies in the pediatric literature suggest the benefits of HFNC therapy only for moderately severe acute viral bronchiolitis. But, the experience with this device in neonatology and adult intensive care may broaden the pediatric indications to include weaning from invasive ventilation and acute asthma. As for any form of respiratory support, HFNC initiation in patients requires close monitoring, whether it be for pre- or inter-hospital transport or in the emergency department or the pediatric intensive care unit.

Oxygen toxicity

Oxygen is one of the most widely available and used therapeutic agents in the world. However, it is all too easy forget that oxygen is a prescribable drug with specific biochemical and physiologic actions, a distinct range of effective doses and well-defined adverse effects at high doses. The human body is affected in different ways depending on the type of exposure. Short exposures to high partial pressures at greater than atmospheric pressure lead to central nervous system toxicity, most commonly seen in divers or in hyperbaric oxygen therapy. Pulmonary and ocular toxicity results from longer exposure to elevated oxygen levels at normal atmospheric pressure.

[High flow, humidified-reheated oxygen therapy: a new oxygenation technique for adults]

Currently conventional oxygen therapy is the first choice symptomatic treatment in the management of acute respiratory failure (ARF). However, conventional oxygen therapy has important limitations which have lead to the development of heated and humidified high-flow nasal oxygen therapy (HFNO). HFNO is an innovative technique that can deliver, through special nasal cannulae, up to 100% of the inspired fraction (FiO2) with heated and humidified oxygen at a maximum flow of 70L/min. The characteristics of this technique (overcoming the patient's spontaneous inspiratory flow, heated humidification,) and its physiological effects (no dilution of FiO2, positive end-expiratory pressure, pharyngeal dead-space washout, decrease in airway resistance), allow efficient optimization of oxygenation with better tolerance for patients. Current data, mainly observational, show that HFNO could be used particularly for the management of hypoxemic ARF, notably in the more severe forms. Indications for using HFNO, alone or in association with noninvasive ventilation, are potentially very broad and may involve different types of ARF (post-operative, post-extubation, palliative care) and even the practice of invasive technical procedures (bronchial fibroscopy). However, though current studies are very encouraging and promise a clinical benefit on patient outcomes, randomized trials are still needed to demonstrate that HFNO avoids the need for endotracheal intubation in the management of ARF.

The effects of gas humidification with high-flow nasal cannula on cultured human airway epithelial cells

Humidification of inspired gas is important for patients receiving respiratory support. High-flow nasal cannula (HFNC) effectively provides temperature and humidity-controlled gas to the airway. We hypothesized that various levels of gas humidification would have differential effects on airway epithelial monolayers. Calu-3 monolayers were placed in environmental chambers at 37°C with relative humidity (RH) < 20% (dry), 69% (noninterventional comparator), and >90% (HFNC) for 4 and 8 hours with 10 L/min of room air. At 4 and 8 hours, cell viability and transepithelial resistance measurements were performed, apical surface fluid was collected and assayed for indices of cell inflammation and function, and cells were harvested for histology (n = 6/condition). Transepithelial resistance and cell viability decreased over time (P < 0.001) between HFNC and dry groups (P < 0.001). Total protein secretion increased at 8 hours in the dry group (P < 0.001). Secretion of interleukin (IL)-6 and IL-8 in the dry group was greater than the other groups at 8 hours (P < 0.001). Histological analysis showed increasing injury over time for the dry group. These data demonstrate that exposure to low humidity results in reduced epithelial cell function and increased inflammation.

A simple, innovative way to reduce rhinitis symptoms after sedation during endoscopy

BACKGROUND

Supplmental oxygen is routinely given via nasal cannula (NC) to patients undergoing moderate sedation for endoscopy. Some patients complain of profuse rhinorrhea and⁄or sneezing after the procedure, which results in additional medical costs and patient dissatisfaction.

OBJECTIVES

To determine the causal relationship between the route of oxygen delivery and troublesome nasal symptoms, and to seek possible solutions.

METHODS

Patients (n=836) were randomly assigned to one of the three following groups: the NC group (n=294), the trimmed NC (TNC) group (n=268) and the nasal mask (NM) group (n=274). All received alfentanil 12.5 μg⁄kg and midazolam 0.06 mg⁄kg, and adjunct propofol for sedation. Supplemental oxygen at a flow rate of 4 L⁄min was used in the NC and TNC groups, and 6 L⁄min in the NM group. The incidence of nasal symptoms and hypoxia were assessed.

RESULTS

The incidence of rhinitis symptoms was significantly higher in the NC group (7.1%) than in the TNC (0.4%) and NM (0%) groups (P<0.001). The incidence of hypoxia was lower in the NC group (3.1%) (P=0.040). All hypoxia events were transient (ie, less than 30 s in duration). On spirometry, the mean value of the lowest saturation of peripheral oxygen was found to be significantly lower in the NM group (96.8%) than in the NC group (97.7%) (P=0.004).

CONCLUSIONS

Trimming the NC or using NMs reduced the incidence of rhinitis symptoms; however, the incidence of hypoxia was higher. Further investigation regarding the efficiency of oxygen supplementation is warranted in the design of novel oxygen delivery devices.

What is the evidence for the use of high flow nasal cannula oxygen in adult patients admitted to critical care units? A systematic review

BACKGROUND

Humidified high flow nasal cannula oxygen therapy is increasingly available in Australian adult intensive care units. Its use in paediatric populations has been extensively studied and has shown positive effects however its clinical effectiveness in adults has not been established.

PURPOSE

A systematic review of the literature was conducted to critique current evidence, inform nursing practice and make recommendations for nursing research.

METHODS

An extensive search strategy identified clinical studies comparing standard oxygen therapy with high flow therapy in critical care units. Two reviewers independently assessed articles for eligibility, methodological quality and inclusion. Outcomes of interest included oxygenation, ventilation, work of breathing, positive airway pressure, patient comfort and long term effect. A narrative synthesis was conducted to describe the emerging evidence.

FINDINGS

Eight studies were included for review. All were abstracts or poster presentations from scientific meetings therefore the quality of data available for analysis was poor. Findings indicated there was preliminary evidence to support the use of high flow therapy to optimise oxygenation in adults. This therapy may reduce the effort of breathing and provide augmented airway pressures. Patients described the therapy as comfortable. No definitive evidence supported the claim that ventilation is improved or conclusively demonstrated a long-term effect.

CONCLUSION

Humidified high flow nasal cannula may be used as an intermediate therapy to improve oxygenation in adult critical care patients. Further research is required to determine the duration of effect of the therapy, identify the patient population for whom it is most beneficial and evaluate long-term outcomes; to enable definitive recommendations for practice to be made.

Response to nasopharyngeal oxygen administration in horses with lung disease

REASONS FOR PERFORMING STUDY

Guidelines for administration of oxygen to standing horses are unavailable because previous investigations of the efficacy of oxygen administration to increase arterial oxygenation in standing horses have produced equivocal results.

OBJECTIVE

To determine the effect of nasal oxygen supplementation on inspired and arterial blood gas tensions in control horses and those with moderate to severe recurrent airway obstruction (RAO).

METHODS

Normal horses (n = 6) and horses during an attack of RAO induced by stabling (n = 6) were studied. Oxygen was administered through either one or 2 cannulae, passed via the nares into the nasopharynx to the level of the medial canthus of each eye. Intratracheal inspired oxygen and carbon dioxide concentration and arterial blood gas tensions were measured at baseline and during delivery of 5, 10, 15, 20 and 30 l/min oxygen.

RESULTS

Nasal cannulae and all but the highest oxygen flow rates were well tolerated. Fractional inspired oxygen concentration (F(I)O2) increased with flow but was significantly lower at all flow rates in horses with RAO compared with controls. Arterial oxygen tension (PaO2) was significantly increased (P < 0.001) by all flow rates, but was always lower in RAO-affected animals. At 30 l/min, PaO2 increased to 319 +/- 31 mmHg in control horses and 264 +/- 69 mmHg in horses with RAO. Additionally, a large arterial to end-tidal gradient for CO2 in RAO-affected horses was observed, indicating increased alveolar deadspace ventilation in these animals.

CONCLUSIONS

The use of nasal cannulae to deliver oxygen effectively increases both F(I)O2 and PaO2 in horses with moderate to severe RAO. Oxygen flow rates up to 20 l/min are well tolerated, but flow rates of 30 l/min produce occasional coughing or gagging.

POTENTIAL RELEVANCE

Oxygen therapy delivered by means of an intranasal cannula is a highly effective means of increasing arterial oxygen tension in horses with respiratory disease. Generally, flows of 10-20 l/min should be effective. If higher flows (20-30 l/min) are necessary, they should be delivered by means of 2 cannulae.

Discomfort associated with underhumidified high-flow oxygen therapy in critically ill patients

OBJECTIVE

To measure (1) the discomfort in non-intubated patients under high-flow oxygen therapy (HFOT) humidified with bubble (BH) or heated humidifiers (HH), and (2) the hygrometric properties of oxygen with a BH and an HH.

DESIGN AND SETTING

This was a randomized cross-over study in critically ill patients during a 3-day period. The humidification device used at days 1 and 3 was changed for the other at day 2. (2) It was also an experimental bench study using the psychrometric method with five randomized flows (3, 6, 9, 12 and 15 l/min) and different humidification techniques.

METHODS

Discomfort, particularly dryness of the mouth and throat, was measured for two humidification conditions (BH and HH) using a 0-10 numerical rating scale (NRS) by patients requiring HFOT with a face mask at a flow >/=5 l/min, in a double-blinded condition.

RESULTS

(1) In this clinical study, 30 patients treated by HFOT at a median flow of 7.8 l/min (5.1-10.9) were included. The global incidence of moderate (NRS = 4-6) and severe discomfort (NRS = 7-10) was 25 and 29%, respectively. The median intensities of both mouth and throat dryness were significantly lower with the HH than with the BH [7.8 (5.0-9.4) vs. 5.0 (3.1-7.0), P = 0.001 and 5.8 (2.3-8.5) vs. 4.3 (2.0-5.0), P = 0.005, respectively]. (2) In the bench study, the mean absolute humidity measured at an ambient temperature of 26 degrees C with the HH was two times greater than with the BH (30 +/- 1 vs. 16 +/- 2 mg/l, P < 0.05) regardless of the flow rate.

CONCLUSIONS

Compared to bubble humidifiers, the use of a heated-humidifier in patients with high-flow oxygen therapy is associated with a decrease of dryness symptoms mediated by increased humidity delivered to the patient.

Discomfort associated with underhumidified high-flow oxygen therapy in critically ill patients

OBJECTIVE

To measure (1) the discomfort in non-intubated patients under high-flow oxygen therapy (HFOT) humidified with bubble (BH) or heated humidifiers (HH), and (2) the hygrometric properties of oxygen with a BH and an HH.

DESIGN AND SETTING

This was a randomized cross-over study in critically ill patients during a 3-day period. The humidification device used at days 1 and 3 was changed for the other at day 2. (2) It was also an experimental bench study using the psychrometric method with five randomized flows (3, 6, 9, 12 and 15 l/min) and different humidification techniques.

METHODS

Discomfort, particularly dryness of the mouth and throat, was measured for two humidification conditions (BH and HH) using a 0-10 numerical rating scale (NRS) by patients requiring HFOT with a face mask at a flow >/=5 l/min, in a double-blinded condition.

RESULTS

(1) In this clinical study, 30 patients treated by HFOT at a median flow of 7.8 l/min (5.1-10.9) were included. The global incidence of moderate (NRS = 4-6) and severe discomfort (NRS = 7-10) was 25 and 29%, respectively. The median intensities of both mouth and throat dryness were significantly lower with the HH than with the BH [7.8 (5.0-9.4) vs. 5.0 (3.1-7.0), P = 0.001 and 5.8 (2.3-8.5) vs. 4.3 (2.0-5.0), P = 0.005, respectively]. (2) In the bench study, the mean absolute humidity measured at an ambient temperature of 26 degrees C with the HH was two times greater than with the BH (30 +/- 1 vs. 16 +/- 2 mg/l, P < 0.05) regardless of the flow rate.

CONCLUSIONS

Compared to bubble humidifiers, the use of a heated-humidifier in patients with high-flow oxygen therapy is associated with a decrease of dryness symptoms mediated by increased humidity delivered to the patient.

Oxygen administration in infants

The main methods of oxygen administration to infants are reviewed. Some methods are more economical and therefore more useful in developing countries. All the methods have potential complications and therefore need to be carefully supervised.

Clinical and in vitro evaluation of membrane humidifier that does not require addition of water

It is well known that conventional bubbling humidifiers are capable of producing micro-aerosols contaminated with bacteria. We developed a unique humidifier, named a membrane humidifier, that does not require an external water supply. This new system obtains moisture from room air. We investigated the clinical and in vitro evaluation of the membrane humidifier. Ten patients with chronic pulmonary disease participated in the study. We evaluated the partial pressure of oxygen in arterial blood (PaO2) of 10 patients who used the new device. We conducted an in vitro study to determine whether the device could prevent the bacterial contamination of humidified-oxygen. We passed compressed air contaminated with Pseudomonas aeruginosa outside the hollow fibres of the membrane humidifier, and the humidified-oxygen passed inside the hollow fibres was sampled into nutrient broth periodically for 10 days. We also compared the relative humidity of oxygen humidified by a membrane humidifier with that of oxygen humidified by a bubbling humidifier. There was no significant difference between measured PaO2 while breathing oxygen humidified using a membrane humidifier and that while breathing oxygen humidified using a bubbling humidifier. Cultures of the humidified-oxygen passed through the hollow fibres were negative for bacteria. The membrane humidifier could produce good humidification. The new device appeared to prevent bacterial contamination, and may help to reduce the risk of infection in patients at hospital and home.

Postoperative oxygen therapy

Much has been published in the medical literature concerning adverse events relating to the surgical patient. Among the notable disorders requiring the expertise of the postanesthesia care unit nurse are the diagnosis and management of respiratory dysfunction acutely attributable to the effects of surgery and anesthesia. Inhalational and/or intravenous anesthetic agents contribute to pathophysiological alterations that lend to the development of hypoxemia in the postoperative period. When patients present with preexisting respiratory disease, their care is frequently more complex and challenging. This review session will address the oxygenation component of respiration and the perioperative influences that alter it as well as treatment considerations for normalizing oxygenation.

Long-term oxygen therapy for COPD. Improving longevity and quality of life in hypoxemic patients

Long-term oxygen therapy can increase life expectancy in hypoxemic patients with COPD. Accurate identification of hypoxemia requires arterial blood gas measurements. Pulse oximetry can be used to measure trends in oxygenation, oxygen needs, and oxygen requirements during exercise and sleep. A detailed oxygen prescription indicates: (1) the oxygen dose (L/min), (2) the number of hours per day that oxygen therapy is required, (3) the dose required during exercise, (4) the oxygen supply system: concentrator, compressed gas cylinder, or liquid oxygen reservoir, and (5) the delivery device: nasal cannula, demand-flow device, reservoir cannula, or transtracheal oxygen catheter.

Disease management of COPD with pulmonary rehabilitation

Pulmonary rehabilitation is a set of tools and disciplines that attends to the multiple needs of the COPD patient. It extends beyond standard care by addressing the disabling features of chronic and progressive lung disease. It centers on self-management, exercise, functional training, psychosocial skills, and contributes to the optimization of medical management. Exercise enables other components by building strength, endurance, confidence, and reducing dyspnea. Patients who have undergone rehabilitation often enjoy a reduced need for health-care utilization. On the downside, rehabilitation is a one-time intervention, the benefits of which dissolve over time. The patient's physician is rarely a participant in the program; thus, the physician is at a disadvantage in being able to support a long-term response. Rehabilitation is available to a small percentage of a large patient population who could benefit. Optimal disease management would entail redesigning standard medical care to integrate rehabilitative elements into a system of patient self-management and regular exercise. It should emphasize physician involvement in self-management, which is essential in developing and maintaining an effective exacerbation protocol. Pulmonary rehabilitation should take its place in the mainstream of disease management through its integrative and reconciliative role in the multidisciplinary continuum of services, as defined by the National Institutes of Health, Pulmonary Rehabilitation Research, Workshop of 1994.

Assisting patients living with long-term oxygen therapy

The nurse has an important role in assisting chronically ill patients disabled by breathlessness to adjust to long-term oxygen therapy. This article provides a simplified summary of the changed physiology necessitating additional oxygen. The focus, however, is on nursing and the educational and rehabilitation strategies that may be used to support patients in living with long-term oxygen therapy.

Oxygen saturation in postoperative patients at low risk for hypoxemia: is oxygen therapy needed?

To evaluate the use of oxygen therapy in the immediate postoperative period, 293 postsurgical patients who had not had thoracic, upper abdominal, or neurologic surgery were randomly assigned upon admission to the postanesthesia care unit (PACU) to receive: 1) 4 L unhumidified O2 via nasal cannula, 2) 40% oxygen by face tent, 3) nurse-coached lung hyperinflations, or 4) no oxygen enhancing regimen. Oxygen saturation was measured on all patients at the time of arrival in the PACU, after 15 min, and after 30 min in the PACU. Only 11 patients in all groups (4%) had their O2 saturation decrease to less than 90% during this time. Ten of these had an initial O2 saturation of 92% or less. Significant differences in O2 saturation were found at 15 min and 30 min between Groups 1 and 2 which received O2 compared to Groups 3 and 4 which did not receive supplemental oxygen. The clinical significance of these differences is open to question. Complaints of dryness were most common in those receiving unhumidified oxygen by nasal cannula. Fourteen percent of patients receiving oxygen by face tent found it uncomfortable and complained of nausea. Supplemental oxygen is not essential in maintaining adequate oxygen saturation in these PACU patients when oxygen saturation levels are more than 92% upon admission to the PACU.