In-Line Aerosol Therapy via Nasal Cannula during Adult and Paediatric Normal, Obstructive, and Restrictive Breathing

High-flow nasal oxygen therapy is being increasingly adopted in intensive and home care settings. The concurrent delivery of aerosolised therapeutics allows for the targeted treatment of respiratory illnesses. This study examined in-line aerosol therapy via a nasal cannula to simulated adult and paediatric models with healthy, obstructive and restrictive lung types. The Aerogen Solo vibrating mesh nebuliser was used in combination with the InspiredTM O2FLO high-flow therapy system. Representative adult and paediatric head models were connected to a breathing simulator, which replicated several different states of lung health. The aerosol delivery was quantified at the tracheal level using UV-spectrophotometry. Testing was performed at a range of supplemental gas flow rates applicable to both models. Positive end-expiratory pressure was measured pre-, during and post-nebulisation. The increases in supplemental gas flow rates resulted in a decrease in aerosol delivery, irrespective of lung health. Large tidal volumes and extended inspiratory phases were associated with the greatest aerosol delivery. Gas flow to inspiratory flow ratios of 0.29-0.5 were found to be optimum for aerosol delivery. To enhance aerosol delivery to patients receiving high-flow nasal oxygen therapy, respiratory therapists should keep supplemental gas-flow rates below the inspiratory flow of the patient.

Nocturnal High-Flow Nasal Cannula Therapy and Sinonasal Symptoms During Cystic Fibrosis Exacerbations

BACKGROUND

Both nasal obstruction and sleep disturbance are common in patients with cystic fibrosis (CF). In patients with obstructive sleep apnea (OSA), studies suggest that these conditions are related and that nasal congestion improves with CPAP therapy. We hypothesized that subjects admitted to hospital for therapy of an exacerbation of CF would have both nasal symptoms and sleep disturbance and that these would improve with the initiation of nocturnal high-flow nasal cannula therapy (HFNC).

METHODS

Twenty-five subjects with an exacerbation of CF were enrolled to randomly receive either 5 d of nocturnal HFNC at 20 L/min in the treatment group or 5 L/min of nocturnal nasal cannula air at ambient temperature and humidity in the low-flow group. On the first and last day of the study, the Sino-Nasal Outcome Test (SNOT-20) was administered to evaluate nasal symptoms, and sleep quality was measured using the Actiwatch 2.

RESULTS

Fifteen subjects completed the study (6 HFNC, 9 low flow). We confirmed that subjects had significant sleep disturbance that did not improve over the 5 d of the study. Subjects also had disturbing nasal symptoms that significantly improved only in those receiving HFNC (pre 14 [20] vs post 6 [13], P = .027).

CONCLUSIONS

Similar to what has been reported in older subjects with OSA, nocturnal HFNC improves sinonasal symptoms in subjects with an exacerbation of CF. There was no measurable effect on sleep quality, which may be due to the short duration of the study, or to subjects being evaluated while being treated in a hospital setting.

Effects of High-Flow Nasal Cannula on Right Heart Dysfunction in Patients with Acute-on-Chronic Respiratory Failure and Pulmonary Hypertension

High-flow nasal cannula (HFNC) has several benefits in patients affected by different forms of acute respiratory failure, based on its own mechanisms. We postulated that HFNC may have some advantages over conventional oxygen therapy (COT) on the heart function in patients with acute-on-chronic respiratory failure with concomitant pulmonary hypertension (PH). We therefore designed this retrospective observational study to assess if HFNC improves the right and left ventricle functions and morphologies, arterial blood gases (ABGs), and patients' dyspnea, compared to COT. We enrolled 17 hospitalized patients receiving HFNC, matched with 17 patients receiving COT. Echocardiographic evaluation was performed at the time of admission (baseline) and 10 days after (T10). HFNC showed significant improvements in right ventricular morphology and function, and a reduction in sPAP. However, there were no significant changes in the left heart measurements with HFNC application. Conversely, COT did not lead to any modifications in echocardiographic measurements. In both groups, oxygenation significantly improved from baseline to T10 (in the HFNC group, from 155 ± 47 to 204 ± 61 mmHg while in the COT group, from 157 ± 27 to 207 ± 27 mmHg; p < 0.0001 for both comparisons). In conclusion, these data suggest an improvement of oxygenation with both treatments; however, only HFNC was able to improve the right ventricular morphology and function after 10 days from the beginning of treatment in a small cohort of patients with acute-on-chronic respiratory failure with PH.

Long-Term Domiciliary High-Flow Nasal Therapy in Patients with Bronchiectasis: A Preliminary Retrospective Observational Case-Control Study

High-flow nasal therapy (HFNT) provides several pathophysiological benefits in chronic respiratory disorders. We aimed to evaluate the effectiveness of long-term HFNT in patients with bronchiectasis (BE).

METHODS

This is a retrospective bicentric case-control study of outpatients with BE on optimized medical treatment with a severe exacerbation requiring hospitalization in the previous year. Patients on long-term home HFNT (cases) and patients on optimized medical treatment alone (controls) were matched by age, sex, bronchiectasis severity index, and exacerbations in the previous year. Data on BE exacerbations, hospitalizations/year, mucus features, respiratory symptoms, and pulmonary function were collected. The primary outcome was the change from baseline in the exacerbation rates at 12 months between groups.

RESULTS

20 patients in the HFNT group and 20 controls were included. A significant reduction in exacerbations [-1.9 (-2.8 to -0.9), p = 0.0005] and hospitalizations [-0.7 (-1.1 to -0.3), p = 0.0006] was found in the HFNT group vs controls. A slight improvement in pulmonary function [FEV₁% +6,1% (+1% to +11.3%) (p = 0.0219), FVC% +4.6% (+0.8% to +8.3%) (p = 0.0188) and FEF_25-75% +13.4 (+11 to +15.9) (p = 0.0189) was also found in the HFNT group compared to controls.

CONCLUSIONS

In this preliminary study, long-term domiciliary HFNT improved the clinical course of patients with BE.

Nasal pillow noninvasive ventilation versus high-flow nasal therapy after extubation in surgical intensive care patients: A propensity-matched cohort study

Objective

To evaluate the tolerability and efficacy of nasal pillow-noninvasive ventilation (NP-NIV) compared with high-flow nasal therapy (HFNT) in postsurgical patients.

Methods

This propensity score-matched retrospective study enrolled postoperative patients that received NP-NIV (NP-NIV group) or HFNT (HFNT group) in the intensive care unit. Data were collected from their medical records and the tolerability and respiratory status before and after extubation were compared between the two groups.

Results

The study enrolled 83 patients in the NP-NIV group and 27 patients in the HFNT group. After propensity score matching, there were 19 patients in each group. After matching, there were no significant differences in the baseline demographic and clinical characteristics before extubation. The tolerability was similar in both groups. When the NP-NIV group was compared with the HFNT group, the respiratory rate was significantly lower (median 16 [interquartile range, 14–17] versus median 19 [interquartile range, 18–26], respectively) and the partial pressure of arterial oxygen/fraction of inspired oxygen ratio was significantly higher (median 205 [174–256] versus median 155 [130–192], respectively) at 1 h after extubation.

Conclusion

NP-NIV was equally well tolerated and provided better respiratory support than HFNT in postsurgical patients.

[High-flow nasal therapy in severe respiratory failure due to SARS-CoV-2]

The use of high-flow nasal therapy (HFNT) in patients with severe acute respiratory failure (SARF) due to COVID-19 pneumonia (NCOVID-19) is debated. Given the lack of beds in Intensive Care Units in the Public Health System of the Province of Neuquén, their use was implemented in general wards. This restrospective multicenter study was carried out to describe the experience of using HNFT in patients with SARF due to NCOVID-19. The primary outcome was the frequency of successful weaning from HFNT and in-hospital mortality (IHM). Two hundred ninety-nine patients were analyzed; 120 (40.1%) were successfully withdrawn from HFNT. This failed in 59.8% (179), 44.1% (132) required invasive mechanical ventilation (IMV), and 15.7% (47) was not candidates for intubation. A ROX index = 5 at 6 h after initiation was associated with the success of HFNT (OR 0.26 [IC 95% 0.15-0.46] p < 0.0001). The general IHM was 48.5% (145/299), 70.4% (93/132) in patients with IMV, 4.2% (5/120) died after successful weaning from HFNT and 100% (47/47) in the group not candidates for intubation. Patients with TNAFO had a statistically significant decrease in MIH and days of hospitalization. TNAFO in general wards achieved a decrease in the use of IMV, with a reduction in mortality and days of stay in hospitalized for NCOVID-19 with SARF.

Measurement of airway pressure during high-flow nasal therapy in apnoeic oxygenation: a randomised controlled crossover trial. Anaesthesia 2020;76:27-35. [PMID: 32776518 DOI: 10.1111/anae.15224]

It is recognised that high-flow nasal therapy can prevent desaturation during airway management. Studies in spontaneously breathing patients show an almost linear relationship between flow rate and positive airway pressure in the nasopharynx. Positive airway pressure has been suggested as one of the possible mechanisms explaining how high-flow nasal therapy works. However, data on pressures generated by high-flow nasal therapy in apnoeic adults under general anaesthesia are absent. This randomised controlled crossover trial investigated airway pressures generated by different flow rates during high-flow nasal therapy in anaesthetised and paralysed apnoeic patients, comparing pressures with closed and open mouths. Following induction of anaesthesia and neuromuscular blockade, a continuous jaw thrust was used to enable airway patency. Airway pressure was measured in the right main bronchus, the middle of the trachea and the pharynx, using a fibreoptically-placed catheter connected to a pressure transducer. Each measurement was randomised with respect to closed or open mouth and different flow rates. Twenty patients undergoing elective surgery were included (mean (SD) age 38 (18) years, BMI 25.0 (3.3) kg.m^-2 , nine women, ASA physical status 1 (35%), 2 (55%), 3 (10%). While closed mouths and increasing flow rates demonstrated non-linear increases in pressure, the pressure increase was negligible with an open mouth. Airway pressures remained below 10 cmH₂ O even with closed mouths and flow rates up to 80 l.min^-1 ; they were not influenced by catheter position. This study shows an increase in airway pressures with closed mouths that depends on flow rate. The generated pressure is negligible with an open mouth. These data question positive airway pressure as an important mechanism for maintenance of oxygenation during apnoea.

Effect of Very-High-Flow Nasal Therapy on Airway Pressure and End-Expiratory Lung Impedance in Healthy Volunteers

BACKGROUND

Previous research has demonstrated a positive linear correlation between flow delivered and airway pressure generated by high-flow nasal therapy. Current practice is to use flows over a range of 30-60 L/min; however, it is technically possible to apply higher flows. In this study, airway pressure measurements and electrical impedance tomography were used to assess the relationship between flows of up to 100 L/min and changes in lung physiology.

METHODS

Fifteen healthy volunteers were enrolled into this study. A high-flow nasal system capable of delivering a flow of 100 L/min was purpose-built using 2 Optiflow systems. Airway pressure was measured via the nasopharynx, and cumulative changes in end-expiratory lung impedance were recorded using the PulmoVista 500 system at gas flows of 30-100 L/min in increments of 10 L/min.

RESULTS

The mean age of study participants was 31 (range 22-44) y, the mean ± SD height was 171.8 ± 7.5 cm, the mean ± SD weight was 69.7 ± 10 kg, and 47% were males. Flows ranged from 30 to 100 L/min with resulting mean ± SD airway pressures of 2.7 ± 0.7 to 11.9 ± 2.7 cm H2O. A cumulative and linear increase in end-expiratory lung impedance was observed with increasing flows, as well as a decrease in breathing frequency.

CONCLUSIONS

Measured airway pressure and lung impedance increased linearly with increased gas flow. Observed airway pressures were in the range used clinically with face-mask noninvasive ventilation. Developments in delivery systems may result in this therapy being an acceptable alternative to face-mask noninvasive ventilation.