Effect of low flow and high flow oxygen delivery on exercise tolerance and sensation of dyspnea. A study comparing the transtracheal catheter and nasal prongs

Efficacy of prophylactic high-flow nasal cannula therapy for postoperative pulmonary complications after pediatric cardiac surgery: a prospective single-arm study

PURPOSE

This study investigated the incidence of postoperative pulmonary complications (PPC) when high-flow nasal cannula therapy (HFNC) is used prophylactically after pediatric cardiac surgery, and evaluated its efficacy.

METHODS

This was a single-arm prospective interventional study that was conducted in a tertiary teaching hospital with eight beds in the pediatric cardiac ICU after approval by the Ethics Committee. One-hundred children under the age of 48 months who were scheduled for cardiac surgery for congenital heart disease were recruited. HFNC was used for 24 h after extubation at a 2 L/kg/min flow rate. The primary outcome was the incidence of PPC within 48 h after extubation. PPC was defined as atelectasis and acute respiratory failure meeting certain criteria. We considered prophylactic HFNC as effective if the prevalence of PPC was < 10%, based on previous reports of reintubation rates of 6%-9% after pediatric cardiac surgery.

RESULTS

A total of 91 patients were finally included in the analysis. The incidence of PPC within 48 h after extubation was 18.7%, whereas atelectasis was observed in 13.2%, and acute respiratory failure in 8.8%. Reintubation rate within 48 h after extubation was 0%.

CONCLUSIONS

We found the incidence of PPC with prophylactic HFNC after planned extubation after pediatric cardiac surgery. However, the incidence was > 10%; therefore, we could not demonstrate its efficacy in this single-arm study. Further studies are needed to investigate whether the HFNC could be adapted as first-line oxygen therapy after pediatric cardiac surgery.

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

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

Use of high-flow nasal oxygen in spontaneously breathing pediatric patients undergoing tubeless airway surgery: A prospective observational study

The use of high-flow nasal oxygen is gaining popularity in apneic and spontaneously breathing adult patients during anesthesia. This prospective observational study evaluated the effect of high-flow nasal oxygen in maintaining adequate oxygenation and ventilation in spontaneously breathing pediatric patients with dynamic airway obstruction, undergoing tubeless airway surgery. Oxygenation was provided via an age-appropriate, high-flow nasal cannula at a flow rate of 2 L kg-1 min-1. Propofol and remifentanil were used to maintain anesthesia while preserving spontaneous respiration. We sought to determine the incidence and risk factors of rescue ventilation. Rescue ventilation with a face mask was performed when the pulse oximetry oxygen saturation was <90% or transcutaneous carbon dioxide was >80 mm Hg. In total, 27 patients were included in the final analysis. Median (interquartile range) of pulse oximetry and transcutaneous carbon dioxide were 100% (99%-100%) and 58.4 mm Hg (51.4-70.3 mm Hg), respectively. Altogether, 9 (33.3%) patients needed rescue ventilation during anesthesia. Of these, 7 patients (25.9%) developed oxygen desaturation (<90%) and 2 patients (7.4%) developed hypercarbia. Patients who required rescue ventilation were significantly younger (8.2 vs 28.8 months, P = .02) and required a longer anesthesia time (55.7 vs 41.0 minutes, P = .04) than those who did not. In conclusion, High-flow nasal oxygen is an alternative technique to maintain oxygenation in children undergoing airway surgeries. However, younger age and longer anesthesia time are significant risk factors leading to the requirement of rescue ventilation in these patients. Further studies with large sample size are required for clinical application of these techniques.

High-flow nasal cannula improves respiratory impedance evaluated by impulse oscillometry in chronic obstructive pulmonary disease patients: a randomised controlled trial

Non-pharmacological treatment with high-flow nasal cannula (HFNC) may play a vital role in treatment of patients with chronic obstructive pulmonary disease (COPD). To evaluate the efficacy of HFNC, impulse oscillation system (IOS) is a new noninvasive technique in measuring the impedance of different portions of lungs. It shows higher sensitivity in contrast to conventional pulmonary function tests (PFT). However, whether IOS is an appropriate technique to evaluate the efficacy of HFNC in improving the impedance of small airways or peripheral lung in patients with COPD is still unclear. We enrolled 26 stable COPD participants randomised into two groups receiving HFNC or nasal cannula (NC) for 10 min followed by a 4-week washout period and crossover alternatively. IOS was used to detect the difference of respiratory impedance after HFNC or NC interventions. IOS parameters, PFT results, transcutaneous partial pressure of carbon dioxide, peripheral oxygen saturation, body temperature, respiratory rate, pulse rate, and blood pressure at the time of pre-HFNC, post-HFNC, pre-NC, and post-NC, were collected and analysed using SPSS (version 25.0, IBM, Armonk, NY, USA). The IOS measurement indicated that HFNC significantly improved R5, R5% predicted, R5–R20, X5-predicted, and Fres compared with NC, whereas no significant difference was observed through the PFT measurement. The beneficial effect of HFNC in improving small airway resistance and peripheral lung reactance compared with that of NC in patients with stable COPD was confirmed through IOS measurement.

Trial registration: ClinicalTrials.gov NCT05130112 22/11/2021.

Effect of pressures and type of ventilation on aerosol delivery to chronic obstructive pulmonary disease patients

Background

Continuous Positive Airway Pressure (CPAP), BiPhasic Positive Airway Pressure (BiPAP), and high flow nasal cannula (HFNC) show some evidence to have efficacy in COVID-19 patients. Delivery during noninvasive mechanical ventilation (NIV) or HFNC gives faster and more enhanced clinical effects than when aerosols are given without assisted breath. The present work aimed to compare the effect of BiPhasic Positive Airway Pressure (BiPAP) mode at two different pressures; low BiPAP (Inspiratory Positive Airway Pressure (IPAP)/Expiratory Positive Airway Pressure (EPAP) of 10/5 cm water) and high BiPAP (IPAP/EPAP of 20/5 cm water), with HFNC system on pulmonary and systemic drug delivery of salbutamol. On the first day of the experiment, all patients received 2500 μg salbutamol using Aerogen Solo vibrating mesh nebulizer. Urine samples 30 min post-dose and cumulative urinary salbutamol during the next 24 h were collected on the next day. On the third day, the ex-vivo filter was inserted before the patient to collect the delivered dose to the patient of the 2500 μg salbutamol. Salbutamol was quantified using high-performance liquid chromatography (HPLC).

Results

Low-pressure BiPAP showed the highest amount delivered to the lung after 30 min followed by HFNC then high-pressure BiPAP. But the significant difference was only observed between low and high-pressure BiPAP modes (p = 0.012). Low-pressure BiPAP showed the highest delivered systemic delivery amount followed by HFNC then high-pressure BiPAP. Low-pressure BiPAP was significantly higher than HFNC (p = 0.017) and high-pressure BiPAP (p = 0.008). No significant difference was reported between HFNC and high-pressure BiPAP. The ex-vivo filter was the greatest in the case of low-pressure BiPAP followed by HFNC then high-pressure BiPAP. Low-pressure BiPAP was significantly higher than HFNC (p = 0.033) and high-pressure BiPAP (p = 0.008). Also, no significant difference was found between HFNC and high-pressure BiPAP.

Conclusions

Our results of pulmonary, systemic, and ex-vivo drug delivery were found to be consistent. The low BiPAP delivered the highest amount followed by the HFNC then the high BiPAP with the least amount. However, no significant difference was found between HFNC and high BiPAP.

Pressurized Metered Dose Inhaler Aerosol Delivery Within Nasal High-Flow Circuits: A Bench Study

Background: Obstructive patients may benefit from nasal high-flow (NHF) therapy, but the use of pressurized metered-dose inhalers (pMDIs) has not been evaluated in this situation. Methods: Using an adult circuit and medium-sized cannula, we have tested different NHF rates, pMDI positions, breathing patterns, spacers, and spacer orientation. First, we evaluated albuterol delivery at the nasal cannula outlet. The second set of experiments made use of a nasopharyngeal cast to estimate the mass of albuterol potentially reaching the lungs. Albuterol was caught on filters placed at the cannula outlet and downstream of the nasal cast, and albuterol was quantified by spectrophotometry. Results: The highest amounts of albuterol delivered at the cannula outlet were observed with a 30 L/min flow rate (vs. 45 and 60 L/min) and placing the device close to the nasal cannula (in comparison with a position on the dry side of the humidification chamber). The use of a spacer was associated with higher delivery. The highest albuterol delivery was observed placing the spacer close to the nasal cannula, oriented for aerosol delivery following the gas flow and a 30 L/min NHF rate. Using this optimal setting, activating the pMDI at the beginning of inspiration (compared to expiration) increased albuterol delivery downstream of the nasopharyngeal cast. Whether in a quiet- or distress-breathing pattern, our measurements showed an amount of albuterol potentially delivered to the lungs exceeding 10% of the actuated dose in optimal conditions. Conclusions: The use of pMDIs is feasible to deliver albuterol within a NHF circuit. Using a spacer placed just upstream from the nasal cannulas, a low NHF rate and activating the pMDI at the beginning of inspiration was associated with drug delivery susceptible to induce bronchodilation, which will require to be tested in the clinical setting.

High-flow nasal cannula and bilevel positive airway pressure for pediatric status asthmaticus: a single center, retrospective descriptive and comparative cohort study

INTRODUCTION

We aimed to describe patient characteristics and clinical outcomes for children hospitalized for status asthmaticus (SA) receiving high-flow nasal cannula (HFNC) or bilevel positive airway pressure (BiPAP).

METHODS

We performed a single center, retrospective cohort study among 39 children admitted for SA aged 5-17 years from January 2016 to May 2019 to a quaternary pediatric intensive care unit (PICU). Cohorts were defined by BiPAP versus HFNC exposure and assessed to determine if differences existed in demographics, anthropometrics, comorbidities, asthma severity indices, historical factors, duration of noninvasive ventilation, and asthma-related clinical outcomes (i.e. length of stay, mechanical ventilation rates, exposure to concurrent sedatives/anxiolysis, and rate of adjunctive therapy exposure).

RESULTS

Thirty-three percent (n = 13) received HFNC (33%) and 67% (n = 26) BiPAP. Children receiving BiPAP had greater age (10.9 ± 3.7 vs. 6.8 ± 2.2 years, P < 0.01), asthma severity (proportion with severe NHLBI classification: 38% vs. 0%, P < 0.01; median pediatric asthma severity score: 13[12,14] vs. 10[9,12], P < 0.01), previous PICU admissions (62% vs. 15%, P = 0.01), frequency of prescribed anxiolysis/sedation (42% vs. 8%, P = 0.02), and median duration of continuous albuterol (1.7[1,3.1] vs. 0.9[0.7,1.6] days, P = 0.03) compared to those on HFNC. Those on HFNC more commonly were treated comorbid bacterial pneumonia (69% vs. 19%, P < 0.01). No differences in NIV duration, mortality, mechanical ventilation rates, or LOS were observed.

CONCLUSIONS

Our data suggest a trial of BiPAP or HFNC appears well tolerated in children with SA. Prospective trials are needed to establish modality superiority and identify patient or clinical characteristics that prompt use of HFNC over BiPAP.

Is Structured Exercise Performed with Supplemental Oxygen a Promising Method of Personalized Medicine in the Therapy of Chronic Diseases?

Aim: This systematic review aimed to explore the literature to identify in which types of chronic diseases exercise with supplemental oxygen has previously been utilized and whether this type of personalized therapy leads to superior effects in physical fitness and well-being. Methods: Databases (PubMed/MEDLINE, CINHAL, EMBASE, Web of knowledge and Cochrane Library) were searched in accordance with PRISMA. Eligibility criteria included adult patients diagnosed with any type of chronic diseases engaging in supervised exercise training with supplemental oxygen compared to normoxia. A random-effects model was used to pool effect sizes by standardized mean differences (SMD). Results: Out of the identified 4038 studies, 12 articles were eligible. Eleven studies were conducted in chronic obstructive pulmonary disease (COPD), while one study included coronary artery disease (CAD) patients. No statistical differences were observed for markers of physical fitness and patient-reported outcomes on well-being between the two training conditions (SMD −0.10; 95% CI −0.27, 0.08; p = 0.26). Conclusions: We found that chronic exercise with supplemental oxygen has mainly been utilized for COPD patients. Moreover, no superior long-term adaptations on physical fitness, functional capacity or patient-reported well-being were found, questioning the role of this method as a personalized medicine approach. Prospero registration: CRD42018104649.

High-flow nasal cannula improves clinical efficacy of airway management in patients undergoing awake craniotomy

Background

Awake craniotomy requires specific sedation procedure in an awake patient who should be able to cooperate during the intraoperative neurological assessment. Currently, limited number of literatures on the application of high-flow nasal cannula (HFNC) in the anesthetic management for awake craniotomy has been reported. Hence, we carried out a prospective study to assess the safety and efficacy of humidified high-flow nasal cannula (HFNC) airway management in the patients undergoing awake craniotomy.

Methods

Sixty-five patients who underwent awake craniotomy were randomly assigned to use HFNC with oxygen flow rate at 40 L/min or 60 L/min, or nasopharynx airway (NPA) device in the anesthetic management. Data regarding airway management, intraoperative blood gas analysis, intracranial pressure, gastric antral volume, and adverse events were collected and analyzed.

Results

Patients using HFNC with oxygen flow rate at 40 or 60 L/min presented less airway obstruction and injuries. Patients with HFNC 60 L/min maintained longer awake time than the patients with NPA. While the intraoperative PaO₂ and SPO₂ were not significantly different between the HFNC and NPA groups, HFNC patients achieved higher PaO₂/FiO₂ than patients with NPA. There were no differences in Brain Relaxation Score and gastric antral volume among the three groups as well as before and after operation in any of the three groups.

Conclusion

HFNC was safe and effective for the patients during awake craniotomy.

Trial registration

Chinese Clinical Trial Registry, CHiCTR1800016621. Date of Registration: 12 June 2018.

Mechanistic Understanding of High Flow Nasal Cannula Therapy and Pressure Support with an In Vitro Infant Model

Despite the increased use of high flow nasal cannula therapy, little has been done to predict airway pressures for a full breath cycle. A 3-month-old infant in vitro model was developed, which included the entire upper airway and the first three bifurcations of the lungs. A breathing simulator was used to create a realistic breath pattern, and high flow was provided using a Vapotherm unit. Four cannulas of varying sizes were used to assess the effects of the inner diameter and nasal occlusion of the cannulas on airway pressures. At 8 L min^-1, end expiratory pressures of 0.821-1.306 cm H₂O and 0.828-1.133 cm H₂O were produced in the nasopharynx and trachea, respectively. Correlations were developed to predict full breath cycle airway pressures, based on the gas flow rate delivered, cannula dimensions, as well as the breathing flow rate, for the nasopharynx and trachea. Pearson correlation coefficients for the nasopharynx and trachea correlations were 0.991 and 0.992, respectively. The developed correlations could be used to determine the flow rate necessary for a cannula to produce pressures similar to CPAP settings. The proposed correlations accurately predict the regional airway pressure up to and including 7 cm H₂O of support for the entire breath cycle.

A high-flow nasal cannula system with relatively low flow effectively washes out CO2 from the anatomical dead space in a sophisticated respiratory model made by a 3D printer

Background

Although clinical studies of the high-flow nasal cannula (HFNC) and its effect on positive end-expiratory pressure (PEEP) have been done, the washout effect has not been well evaluated. Therefore, we made an experimental respiratory model to evaluate the respiratory physiological effect of HFNC.

Methods

An airway model was made by a 3D printer using the craniocervical 3D-CT data of a healthy 32-year-old male. CO₂ was infused into four respiratory lung models (normal-lung, open- and closed-mouth models; restrictive- and obstructive-lung, open-mouth models) to maintain the partial pressure of end-tidal CO₂ (P_ETCO₂) at 40 mmHg. HFNC flow was changed from 10 to 60 L/min. Capnograms were recorded at the upper pharynx, oral cavity, subglottic, and inlet sites of each lung model.

Results

With the normal-lung, open-mouth model, 10 L/min of HFNC flow decreased the subglottic P_ETCO₂ to 30 mmHg. Increasing the HFNC flow did not further decrease the subglottic P_ETCO₂. With the normal-lung, closed-mouth model, HFNC flow of 40 L/min was required to decrease the P_ETCO₂ at all sites. Subglottic P_ETCO₂ reached 30 mmHg with an HFNC flow of 60 L/min. In the obstructive-lung, open-mouth model, P_ETCO₂ at all sites had the same trend as in the normal-lung, open-mouth model. In the restrictive-lung, open-mouth model, 20 L/min of HFNC flow decreased the subglottic P_ETCO₂ to 25 mmHg, and it did not decrease further. As HFNC flow was increased, PEEP up to 7 cmH₂O was gradually generated in the open-mouth models and up to 17 cmH₂O in the normal-lung, closed-mouth model.

Conclusions

The washout effect of the HFNC was effective with relatively low flow in the open-mouth models. The closed-mouth model needed more flow to generate a washout effect. Therefore, HFNC flow should be considered based on the need for the washout effect or PEEP.

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.

Pilot Clinical Trial of High-Flow Oxygen Therapy in Children with Asthma in the Emergency Service

OBJECTIVES

To assess the efficacy of high-flow nasal cannula (HFNC) oxygen therapy and safety in children with asthma and moderate respiratory failure in the emergency department (ED).

STUDY DESIGN

This was a prospective randomized pilot trial of children (aged 1-14 years) presenting to a tertiary academic pediatric ED with moderate-to-severe asthma exacerbations between September 2012 and December 2015. Patients with a pulmonary score (PS) ≥6 or oxygen saturation <94% with a face mask despite initial treatment (salbutamol/ipratropium bromide and corticosteroids) were randomized to HFNC or to conventional oxygen therapy. Pharmacologic treatment was at the discretion of attending physicians. The primary outcome was a decrease in PS ≥2 in the first 2 hours. Secondary outcomes included disposition, length of stay, and need for additional therapies.

RESULTS

We randomly allocated 62 children to receive either HFNC (n = 30) or standard oxygen therapy (n = 32). Baseline patient characteristics were similar in the 2 groups. At 2 hours after the start of therapy, PS had decreased by ≥2 points in 16 patients in the HFNC group (53%) compared with 9 controls (28%) (P = .01). Between-group differences in disposition, length of stay, and need for additional therapies were not significant. No side effects were reported.

CONCLUSION

HFNC appears to be superior to conventional oxygen therapy for reducing respiratory distress within the first 2 hours of treatment in children with moderate-to-severe asthma exacerbation refractory to first-line treatment. Further studies are needed to demonstrate its overall efficacy in the management of asthma and respiratory failure in the ED.

TRIAL REGISTRATION

EudraCT: 2012-001771-36.

Effectiveness of high-flow nasal cannula oxygen therapy for acute respiratory failure with hypercapnia

Background

Heated and humidified high-flow nasal cannula (HFNC) oxygen therapy has recently been introduced for hypoxic respiratory failure. However, it has not been well-evaluated for acute respiratory failure with hypercapnia.

Methods

This retrospective study included acute respiratory failure patients with hypercapnia in the medical intensive care unit (MICU) from April 2011 to February 2013, who required HFNC oxygen therapy for hypoxemia. Respiratory parameters were recorded and arterial blood gas analyses conducted before, and at 1 and 24 h after initiation of HFNC oxygen therapy.

Results

Thirty-three patients were studied [median age, 72 years; range, 17-85 years; men, 24 (72.7%)]. Pneumonia (36.4%) and acute exacerbation of chronic obstructive pulmonary disease (33.4%) were the most common reasons for oxygen therapy. Most patients (60.6%) received oxygen therapy via nasal prong before HFNC application. The mean fraction of inspired oxygen (FiO₂) and HFNC flow rate were 0.45±0.2 and 41.1±7.1 L/min, respectively; mean duration of application was 3.6±4.1 days. The partial pressure of arterial carbon dioxide (PaCO₂) was 55.0±12.2 mmHg at admission, and increased by approximately 1.0±7.7 mmHg with conventional oxygen therapy. In contrast, with HFNC therapy, PaCO₂ decreased by 4.2±5.5 and 3.7±10.8 mmHg in 1 and 24 h, respectively, resulting in significant improvement in hypercapnia (P=0.006 and 0.062, respectively).

Conclusions

HFNC oxygen therapy with sufficient FiO₂ to maintain a normal partial pressure of arterial oxygen (PaO₂) significantly reduced PaCO₂ in acute respiratory failure with hypercapnia.

High-Velocity Nasal Insufflation in the Treatment of Respiratory Failure: A Randomized Clinical Trial

STUDY OBJECTIVE

We compare high-velocity nasal insufflation, a form of high-flow nasal cannula, with noninvasive positive-pressure ventilation in the treatment of undifferentiated respiratory failure with respect to therapy failure, as indicated by requirement for endotracheal intubation or cross over to the alternative therapy.

METHODS

This was a multicenter, randomized trial of adults presenting to the emergency department (ED) with respiratory failure requiring noninvasive positive-pressure ventilation. Patients were randomly assigned to high-velocity nasal insufflation (initial flow 35 L/min; temperature 35°C (95°F) to 37°C (98.6°F); FiO₂ 1.0) or noninvasive positive-pressure ventilation using an oronasal mask (inspiratory positive airway pressure 10 cm H₂O; expiratory positive airway pressure 5 cm H₂O). The primary outcome was therapy failure at 72 hours after enrollment. A subjective outcome of crossover was allowed as a risk mitigation to support deferment of informed consent. Noninferiority margins were set at 15 and 20 percentage points, respectively.

RESULTS

A total of 204 patients were enrolled and included in the analysis, randomized to high-velocity nasal insufflation (104) and noninvasive positive-pressure ventilation (100). The intubation rate (high-velocity nasal insufflation=7%; noninvasive positive-pressure ventilation=13%; risk difference=-6%; 95% confidence interval -14% to 2%) and any failure of the assigned arm (high-velocity nasal insufflation=26%; noninvasive positive-pressure ventilation=17%; risk difference 9%; confidence interval -2% to 20%) at 72 hours met noninferiority. The effect on PCO₂ over time was similar in the entire study population and in patients with baseline hypercapnia. Vital signs and blood gas analyses improved similarly over time. The primary limitation was the technical inability to blind the clinical team.

CONCLUSION

High-velocity nasal insufflation is noninferior to noninvasive positive-pressure ventilation for the treatment of undifferentiated respiratory failure in adult patients presenting to the ED.

Dual oxygen therapy in patient on bilevel positive airway pressure prevented invasive mechanical ventilation

During noninvasive bilevel positive airway pressure (BiPAP) ventilation it is found that several times patients are unable to maintain oxygen saturation and develop breathing difficulty despite its high setting and high oxygen flow, further management requires invasive positive pressure mechanical ventilation. Increasing oxygen concentration inside the BiPAP mask using nasal cannula with addition of another flow meter not only increase oxygen saturation but also make the patient more comfortable and prevent intubation and its complications. This dual oxygen therapy is particularly useful in patients where non invasive ventilation is required and avoiding the need invasive mechanical ventilation. High-flow nasal cannula oxygen therapy has many advantages over traditional oxygen delivery systems. Here, we are going to report two cases of patients on BiPAP in which invasive positive pressure ventilation was prevented using dual oxygen therapy using nasal cannula with flow meter and BiPAP mask with addition another flow meter in a single sitting.

Impact of Heated Humidified High Flow Air via Nasal Cannula on Respiratory Effort in Patients with Chronic Obstructive Pulmonary Disease

Background: High flow nasal cannula therapy (HFNC) has been widely adopted for respiratory distress, and evidence suggests that purging dead space of the upper airway improves gas fractions in the lung. This study tests the hypothesis that HFNC with room air could be as effective as low flow oxygen in chronic obstructive pulmonary disease (COPD). Methods: Thirty-two COPD patients prescribed 1 - 2 L/min of oxygen were studied. The conditions tested consisted of a control (CTRL; no therapy), then in random order HFNC and prescribed low flow oxygen (LFO). HFNC was the highest flow tolerated up to 35 L/min without supplemental oxygen. Arterial blood gases (ABGs), respiratory rate (RR), heart rate (HR) and tidal volume (V_T) were measured at the end of each condition. Results: Arterial oxygen (PaO₂) was greater (p < 0.001) for LFO than both HFNC and CTRL (CTRL=57.4±6.1mmHg, HFNC=58.6±8.3mmHg, LFO=72.6±10.2mmHg). HFNC reduced RR by 11% (p<0.05) from CTRL and LFO (CTRL=20.2±3.8br/min, HFNC=17.9±3.3br/min, LFO=20.2±3.7br/min) with no differences in V_T. There were no differences between arterial carbon dioxide (PaCO₂) (CTRL=45.5±4.9mmHg, HFNC=45.0±5.3mmHg, LFO=46.0±3.9mmHg). Conclusions: HFNC resulted in a clinically relevant reduction in ventilatory effort with no change in ABG indicating a gas equilibrium effect of purging anatomical dead space. Clinical Trial Registration: ClinicalTrials.gov ID: NCT00990210.

A Novel Weaning Protocol for High-Flow Nasal Cannula in the PICU

OBJECTIVE

High-flow nasal cannula use in the PICU continues to increase; however, a protocol for weaning patients has yet to be published. This study aimed to create an efficient and safe protocol for weaning high-flow nasal cannula.

DESIGN

A Respiratory Assessment Score was created using two validated scoring systems. A protocol was established for set "holidays" off high-flow nasal cannula, where nasal cannula flow was reduced to age-based low-flow nasal cannula rates if Respiratory Assessment Scores met certain criteria.

SETTING

The PICU at Children's Healthcare of Atlanta at Egleston, a quaternary level hospital affiliated with Emory University.

PATIENTS

Patients treated in the PICU with high-flow nasal cannula from August 2013 to March 2014. Exclusions included apnea, heliox therapy, oxygen saturations less than 92% with a FIO2 greater than 50%, admitted to PICU less than 6 hours, progression to intubation prior to scoring, or those ordered by physician to not receive holidays based on clinical status.

INTERVENTIONS

Patients who qualified for a "holiday" based on Respiratory Assessment Score were trialed off high-flow nasal cannula and rescored afterwards to assess tolerance.

MEASUREMENTS AND MAIN RESULTS

One hundred thirty-three patients were treated with high-flow nasal cannula, with the most common diagnosis being bronchiolitis (43%). Of these 133 patients, 119 (89.5%) successfully weaned to low-flow nasal cannula within four holiday attempts. Eighty-three patients (70%) weaned with only one attempt. Fourteen patients (10.5%) failed to wean. Reasons for failure were reintubation, increasing flow on high-flow nasal cannula, too high of Respiratory Assessment Score to meet weaning criteria, or slow weaning after failed attempts. Holidays did not precipitate clinical deterioration or lead to immediate intubation.

CONCLUSIONS

Our study suggests that a high-flow nasal cannula "holiday" protocol is a safe and effective way to successfully wean PICU patients off high-flow nasal cannula. Additional investigation including validation of the scoring system used is warranted.

Physiological impact of high-flow nasal cannula therapy on postextubation acute respiratory failure after pediatric cardiac surgery: a prospective observational study

Background

Reintubation after pediatric cardiac surgery is associated with a high rate of mortality. Therefore, adequate respiratory support for postextubation acute respiratory failure (ARF) is important. However, little is known about the physiological impact of high-flow nasal cannula (HFNC) therapy on ARF after pediatric cardiac surgery. Our working hypothesis was that HFNC therapy for postextubation ARF after pediatric cardiac surgery improves hemodynamic and respiratory parameters.

Methods

This was a prospective observational study conducted at a single university hospital. Children less than 48 months of age who had postextubation ARF after cardiac surgery were included in this study. HFNC therapy was started immediately after diagnosis of postextubation ARF.

Data obtained just before starting HFNC therapy were used for pre-HFNC analysis, and data obtained 1 h after starting HFNC therapy were used for post-HFNC analysis. We compared hemodynamic and respiratory parameters between pre-HFNC and post-HFNC periods. The Wilcoxon signed-rank test was used to analyze these indices.

Results

Twenty children were included in this study. The median age and body weight were 4.5 (2.3–14.0) months and 4.3 (3.1–7.1) kg, respectively. Respiratory rate (RR) significantly decreased from 43.5 (32.0–54.8) to 28.5 (21.0–40.5) breaths per minute (p = 0.0008) 1 h after the start of HFNC therapy. Systolic blood pressure also decreased from 87.5 (77.8–103.5) to 76.0 (70.3–85.0) mmHg (p = 0.003). Oxygen saturation, partial pressure of arterial carbon dioxide, heart rate, and lactate showed no remarkable changes. There was no adverse event caused by HFNC therapy.

Conclusions

HFNC therapy improves the RR of patients who have postextubation ARF after pediatric cardiac surgery without any adverse events.

The Effect of High-Flow Nasal Cannula Oxygen Therapy on Mortality and Intubation Rate in Acute Respiratory Failure: A Systematic Review and Meta-Analysis

OBJECTIVE

High-flow nasal cannulae are used in adults with or at risk of acute respiratory failure. We conducted a systematic review and meta-analysis to evaluate the evidence for their use in this setting.

DATA SOURCES

Ovid Medline, Embase, and Cochrane Database of Systematic Reviews.

STUDY SELECTION

Databases were searched for randomized controlled trials comparing administration of high-flow nasal cannulae with usual care (i.e., conventional oxygen therapy or noninvasive ventilation) in adults with respiratory failure. The primary outcome was hospital mortality; the rate of intubation and assessment of delirium and comfort were secondary outcomes.

DATA EXTRACTION

One hundred forty-seven nonduplicate citations were screened, 32 underwent full screening and data extraction, and 14 trials were eligible for inclusion in the review. Nine trials were used in the meta-analysis, including a total of 2,507 subjects.

DATA SYNTHESIS

When high-flow nasal cannulae were compared with usual care, there was no difference in mortality (high-flow nasal cannulae, 60/1,006 [6%] vs usual care, 90/1,106 [8.1%]) (n = 2,112; p = 0.29; I, 25%; fixed effect model: odds ratio, 0.83; 95% CI, 0.58-1.17) or rate of intubation (high-flow nasal cannulae, 119/1,207 [9.9%] vs usual care, 204/1,300 [15.7%]) (n = 2,507; p = 0.08; I, 53%; random effect model: odds ratio, 0.63; 95% CI, 0.37-1.06). A qualitative analysis of 13 studies on tolerability and comfort suggested that high-flow nasal cannulae are associated with improved patient comfort and dyspnea scores. Trial sequential analyses on primary and secondary outcomes suggested that required information size was not reached.

CONCLUSIONS

No difference in mortality or intubation was detected in patients with acute respiratory failure treated with high-flow nasal cannulae compared with usual care. High-flow nasal cannulae seem well tolerated by patients. Further large randomized controlled trials are required to evaluate their utility in this setting.

High-flow nasal cannula therapies for respiratory management in pediatric patients

High-flow nasal cannula (HFNC) oxygen therapy is a non-invasive form of respiratory support that is rapidly being taken up in pediatric intensive care units (PICU). For infants with bronchiolitis, who are the largest non-elective source of admissions to a PICU, there is some evidence that using HFNC therapy reduces the need for intubation and mechanical ventilation. The aim of this review article is to explore, describe, critique and add to the evidence surrounding the use of HFNC therapy in the pediatric population for the management of respiratory distress.

Physiologic Basis for Nasal Continuous Positive Airway Pressure, Heated and Humidified High-Flow Nasal Cannula, and Nasal Ventilation

Noninvasive support modalities have become ever more present in the care of newborns with a wide variety of disease processes. As clinicians have continued to avoid intubation and mechanical ventilation in preterm and term infants, the technologies available to support these groups have grown. Despite this rapid growth they can be broken down into 3 large categories of support, all attempting to deliver both flow and pressure to the nasopharynx supporting both phases of spontaneous breathing. The goal of all of the therapies is to stabilize a heterogeneous group of disorders with some common pathologies and avoid invasive support modalities.

High-flow nasal cannula therapy for adult patients

High-flow nasal cannula (HFNC) oxygen therapy has several physiological advantages over traditional oxygen therapy devices, including decreased nasopharyngeal resistance, washing out of the nasopharyngeal dead space, generation of positive pressure in the pharynx, increasing alveolar recruitment in the lungs, humidification of the airways, increased fraction of inspired oxygen and improved mucociliary clearance. Recently, the use of HFNC in treating adult critical illness patients has significantly increased, and it is now being used in many patients with a range of different disease conditions. However, there are no established guidelines to direct the safe and effective use of HFNC for these patients. This review article summarizes the available published literature on the positive physiological effects, mechanisms of action, and the clinical applications of HFNC, compared with traditional oxygen therapy devices. The available literature suggests that HFNC oxygen therapy is an effective modality for the early treatment of critically adult patients.

Retrospective evaluation of the effect of high flow oxygen therapy delivered by nasal cannula on PaO2 in dogs with moderate-to-severe hypoxemia

OBJECTIVE

To describe the effects of high flow oxygen therapy (HFOT) in canine patients failing traditional oxygen therapy (TOT).

DESIGN

Retrospective study.

SETTING

Private referral practice.

ANIMALS

Six client-owned dogs with primary pulmonary hypoxemia.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

High flow oxygen was delivered by high flow nasal prongs to dogs assessed clinically to be failing TOTs. HFOT was able to significantly improve PaO2 compared to TOT in severely hypoxemic dogs (median, 133.75 mm Hg; range, 109.2-304.8) versus median 61.85 mm Hg (range, 52.3-71.8; xsP = 0.0412). Flow rates were significantly higher with HFOT compared to TOT (median, 688 mL/kg/min; range, 523-1,667 mL/kg/min) versus median 122 mL/kg/min (range, 80-208; P = 0.0412). Complications included patient discomfort requiring light sedation in 1/6 dogs and persistence of a pneumothorax in 1 dog. Hypoxemia resolved in 4/6 dogs.

CONCLUSION

These data suggest HFOT is a viable clinical intervention for dogs with moderate-to-severe hypoxemia assessed to be failing TOT. Further studies are needed to determine if HFOT can be used as an alternative to mechanical ventilation in resource limited settings and to characterize the complications associated with this therapy.

Applications of Nasal High-Flow Oxygen Therapy in Critically ill Adult Patients

The use of nasal high-flow oxygen therapy (NHFOT) has become increasingly common in hospitals across Europe, Asia, and North America. These high utility devices provide an efficient and comfortable access points for providing supplemental oxygen to patients with variety of respiratory disorders. They are relatively easy to set up, and clinicians and patients alike give very positive feedback about their ease of use and comfort for patients in the hospital setting. However, it remains uncertain whether NHFOT improves patient survival or even reduces respiratory complications. Outcome data in adult populations are few and frequently underpowered to guide physicians for their widespread use in hospital setting. In this article, we present a review of the current technology and available studies pertinent to NHFOT.

The effects of a 2-h trial of high-flow oxygen by nasal cannula versus Venturi mask in immunocompromised patients with hypoxemic acute respiratory failure: a multicenter randomized trial

Introduction

In immunocompromised patients, acute respiratory failure (ARF) is associated with high mortality, particularly when invasive mechanical ventilation (IMV) is required. In patients with severe hypoxemia, high-flow nasal oxygen (HFNO) therapy has been used as an alternative to delivery of oxygen via a Venturi mask. Our objective in the present study was to compare HFNO and Venturi mask oxygen in immunocompromised patients with ARF.

Methods

We conducted a multicenter, parallel-group randomized controlled trial in four intensive care units. Inclusion criteria were hypoxemic ARF and immunosuppression, defined as at least one of the following: solid or hematological malignancy, steroid or other immunosuppressant drug therapy, and HIV infection. Exclusion criteria were hypercapnia, previous IMV, and immediate need for IMV or noninvasive ventilation (NIV). Patients were randomized to 2 h of HFNO or Venturi mask oxygen.

Results

The primary endpoint was a need for IMV or NIV during the 2-h oxygen therapy period. Secondary endpoints were comfort, dyspnea, and thirst, as assessed hourly using a 0–10 visual analogue scale. We randomized 100 consecutive patients, including 84 with malignancies, to HFNO (n = 52) or Venturi mask oxygen (n = 48). During the 2-h study treatment period, 12 patients required IMV or NIV, and we found no significant difference between the two groups (15 % with HFNO and 8 % with the Venturi mask, P = 0.36). None of the secondary endpoints differed significantly between the two groups.

Conclusions

In immunocompromised patients with hypoxemic ARF, a 2-h trial with HFNO improved neither mechanical ventilatory assistance nor patient comfort compared with oxygen delivered via a Venturi mask. However, the study was underpowered because of the low event rate and the one-sided hypothesis.

Trial registration

ClinicalTrials.gov identifier: NCT02424773. Registered 20 April 2015.

The role of high flow oxygen therapy in acute respiratory failure

Acute respiratory failure represents one of the most common causes of intensive care unit admission and oxygen therapy remains the first-line therapy in the management of these patients. In recent years, high-flow oxygen via nasal cannula has been described as a useful alternative to conventional oxygen therapy in patients with acute respiratory failure. High-flow oxygen via nasal cannula rapidly alleviates symptoms of acute respiratory failure and improves oxygenation by several mechanisms, including dead space washout, reduction in oxygen dilution and inspiratory nasopharyngeal resistance, a moderate positive airway pressure effect that may generate alveolar recruitment and an overall greater tolerance and comfort with the interface and the heated and humidified inspired gases. However, the experience in adults is still limited and there are no clinical guidelines to establish recommendations for their use. This article aims to review the existing evidence on the use of high-flow oxygen via nasal cannula in adults with acute respiratory failure and its possible applications, advantages and limitations.

Weaning preterm infants from continuous positive airway pressure: evidence for best practice

BACKGROUND

Nasal continuous positive airway pressure (NCPAP) is frequently used in preterm infants. However, there is no consensus on when and how to wean them from NCPAP.

DATA SOURCES

Based on recent publications, we have reviewed the criteria of readiness-to-wean and factors affecting weaning success. A special focus is placed on the methods of weaning from NCPAP in preterm infants.

RESULTS

Practical points of when and how to wean from NCPAP in preterm infants are explained. Preterm infants are ready to be weaned from NCPAP when they are stable on a low NCPAP pressure with no (or minimal) oxygen requirement. Methods used to wean from NCPAP include: sudden weaning of NCPAP, gradual decrease of NCPAP pressure, graded-timeoff NCPAP (cycling), weaning to high or low flow nasal cannula, and a combination of these methods. The best strategy for weaning is yet to be determined. Cyclingoff NCPAP increases the duration of NCPAP and length of hospital stay without beneficial effect on success of weaning. Gradual decrease of NCPAP pressure is more physiological and better tolerated than cycling-off NCPAP.

CONCLUSION

Further studies are needed to reach a consensus regarding the optimal timing and the best method for weaning from NCPAP in preterm infants.

[High flow nasal cannula in infants: Experience in a critical patient unit]

INTRODUCTION

The high flow nasal cannula (HFNC) is a method of respiratory support that is increasingly being used in paediatrics due to its results and safety.

OBJECTIVE

To determine the efficacy of HFNC, as well as to evaluate the factors related to its failure and complications associated with its use in infants.

PATIENTS AND METHOD

An analysis was performed on the demographic, clinical, blood gas, and radiological data, as well as the complications of patients connected to a HFNC in a critical care unit between June 2012 and September 2014. A comparison was made between the patients who failed and those who responded to HFNC. A failure was considered as the need for further respiratory support during the first 48hours of connection. The Kolmogorov Smirnov, Mann-Whitney U, chi squared and the Exact Fisher test were used, as well as correlations and a binary logistic regression model for P≤.05.

RESULTS

The study included 109 patients, with a median age and weight: 1 month (0.2-20 months) and 3.7kg (2-10kg); 95 percentile: 3.7 months and 5.7kg, respectively. The most frequent diagnosis and radiological pattern was bronchiolitis (53.2%) and interstitial infiltration (56%). Around 70.6% responded. There was a significant difference between failure and response in the diagnosis (P=.013), radiography (P=018), connection context (P<.0001), pCO2 (median 40.7mmHg [15.4-67 mmHg] versus 47.3mmHg [28.6-71.3mmHg], P=.004) and hours on HFNC (median 60.75hrs [5-621.5 hrs] versus 10.5hrs [1-29 hrs], P<.0001). The OR of the PCO2 ≥ 55mmHg for failure was 2.97 (95% CI; 1.08-8.17; P=.035). No patient died and no complications were recorded.

CONCLUSION

The percentage success observed was similar to that published. In this sample, the failure of HFNC was only associated with an initial pCO2 ≥ 55mmHg. On there being no complications reported as regards it use, it is considered safe, although a randomised, controlled, multicentre study is required to compare and contrast these results.

A randomized pilot study comparing heated humidified high-flow nasal cannulae with NIPPV for RDS

OBJECTIVE

To compare the requirement for endotracheal ventilation in preterm infants treated with heated, humidified high-flow nasal cannula (HHHFNC) with those treated with nasal intermittent positive pressure ventilation (NIPPV) for the primary treatment of respiratory distress syndrome (RDS).

STUDY DESIGN

Randomized, controlled, prospective, single-center pilot study. Infants (gestational age [GA] <35 weeks, birth weight [BW] >1,000 g) with RDS were randomly assigned to receive HHHFNC (38 infants) delivered by Vapotherm® device (Precision Flow™ or 2000 i, Vapotherm Inc., Stevensville, MD), at flows between 1.0 and 5.0 L/min, or NIPPV (38 infants) delivered by the SLE 2000 or 5000. Surfactant was administered as rescue therapy. Analysis was done by intention-to-treat.

RESULTS

Infant's characteristics ([mean ± SD] GA 31.8 ± 2.3 vs. 32.0 ± 2.3 weeks) and cardio-respiratory status at study entry (FiO2 0.25 ± 0.05 vs. 0.26 ± 0.07; SpO2 90 ± 6% vs. 87 ± 12; PCO2 54.4 ± 10.4 vs. 52.6 ± 8.0 mmHg) were comparable for the HHHFNC and NIPPV groups. There was no significant difference in the need for endotracheal ventilation (28.9% vs. 34.2%) between HHHFNC and NIPPV groups. One infant failed HHHFNC and succeeded on NIPPV. The rate of neonatal morbidities (pneumothorax, bronchopulmonary dysplasia, intra-ventricular hemorrhage, necrotizing enterocolitis, patent ductus arteriosus, and nasal trauma) was comparable in both groups. Duration of nasal support was longer with HHHFNC compared with NIPPV (5.4 ± 4.0 vs. 2.6 ± 1.9 days, P = 0.006) but the duration of endotracheal ventilation, time to full feeds, and length of stay were comparable.

CONCLUSIONS

Our pilot study suggests that HHHFNC maybe as effective as NIPPV in preventing endotracheal ventilation in the primary treatment of RDS in premature infants (<35 weeks GA and BW >1,000 g).

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, 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.

Improving pharmaceutical aerosol delivery during noninvasive ventilation: effects of streamlined components

Aerosol delivery efficiency during noninvasive ventilation (NIV) is known to be low (~10%) and is associated with poor outcomes of aerosol therapy. The objective of this study was to demonstrate the benefit of redesigning ventilation circuit components using a streamlining approach to improve aerosol delivery during nasal high flow therapy in adults with a conventional-sized aerosol from a mesh nebulizer. The ventilation circuit consisted of a humidifier, mesh nebulizer, mixing T-connector (with 90° angle), 10 mm tubing, and nasal cannula interface. In vitro experiments and computational fluid dynamics analyses were used to evaluate depositional losses in a system of existing components and a newly proposed streamlined T-connector and cannula at flow rates of 30 and 45 LPM. Streamlined designs reduced deposition in the T-connector by a factor of 4. In the nasal cannula, the streamlined designs reduced depositional losses by factors of 1.25-2.0. With the streamlined designs, the highest emitted dose achieved was >40% for a conventional-sized aerosol at 30 LPM. Streamlined geometries offer an effective method to significantly improve the delivery of aerosols through components of NIV systems. This increase in delivery efficiency is important for new inhaled medications with narrow therapeutic windows, increased costs, or long delivery times.

Use of high flow nasal cannula in critically ill infants, children, and adults: a critical review of the literature

BACKGROUND

High flow nasal cannula (HFNC) systems utilize higher gas flow rates than standard nasal cannulae. The use of HFNC as a respiratory support modality is increasing in the infant, pediatric, and adult populations as an alternative to non-invasive positive pressure ventilation.

OBJECTIVES

This critical review aims to: (1) appraise available evidence with regard to the utility of HFNC in neonatal, pediatric, and adult patients; (2) review the physiology of HFNC; (3) describe available HFNC systems (online supplement); and (4) review ongoing and planned trials studying the utility of HFNC in various clinical settings.

RESULTS

Clinical neonatal studies are limited to premature infants. Only a few pediatric studies have examined the use of HFNC, with most focusing on this modality for viral bronchiolitis. In critically ill adults, most studies have focused on acute respiratory parameters and short-term physiologic outcomes with limited investigations focusing on clinical outcomes such as duration of therapy and need for escalation of ventilatory support. Current evidence demonstrates that HFNC generates positive airway pressure in most circumstances; however, the predominant mechanism of action in relieving respiratory distress is not well established.

CONCLUSION

Current evidence suggests that HFNC is well tolerated and may be feasible in a subset of patients who require ventilatory support with non-invasive ventilation. However, HFNC has not been demonstrated to be equivalent or superior to non-invasive positive pressure ventilation, and further studies are needed to identify clinical indications for HFNC in patients with moderate to severe respiratory distress.

Improving the lung delivery of nasally administered aerosols during noninvasive ventilation-an application of enhanced condensational growth (ECG)

BACKGROUND

Aerosol drug delivery during noninvasive ventilation (NIV) is known to be inefficient due to high depositional losses. To improve drug delivery efficiency, the concept of enhanced condensational growth (ECG) was recently proposed in which a submicrometer or nanoaerosol reduces extrathoracic deposition and subsequent droplet size increase promotes lung retention. The objective of this study was to provide proof-of-concept that the ECG approach could improve lung delivery of nasally administered aerosols under conditions consistent with NIV.

METHODS

Aerosol deposition and size increase were evaluated in an adult nose-mouth-throat (NMT) replica geometry using both in vitro experiments and CFD simulations. For the ECG delivery approach, separate streams of a submicrometer aerosol and warm (39°C) saturated air were generated and delivered to the right and left nostril inlets, respectively. A control case was also considered in which an aerosol with a mass median aerodynamic diameter (MMAD) of 4.67 μm was delivered to the model.

RESULTS

In vitro experiments showed that the ECG approach significantly reduced the drug deposition fraction in the NMT geometry compared with the control case [14.8 (1.83)%-ECG vs. 72.6 (3.7)%-control]. Aerosol size increased from an initial MMAD of 900 nm to a size of approximately 2 μm at the exit of the NMT geometry. Results of the CFD model were generally in good agreement with the experimental findings. Based on CFD predictions, increasing the delivery temperature of the aerosol stream from 21 to 35°C under ECG conditions further reduced the total NMT drug deposition to 5% and maintained aerosol growth by ECG to approximately 2 μm.

CONCLUSIONS

Application of the ECG approach may significantly improve the delivery of pharmaceutical aerosols during NIV and may open the door for using the nasal route to routinely deliver pulmonary medications.

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.