Humidification during oxygen therapy and non-invasive ventilation: do we need some and how much?

The nasal oxygen practice in intensive care units in China: A multi-centered survey

Background

Nurses frequently administer nasal oxygen therapy for patients in intensive care units (ICUs). However, little is known about the current status, nurses’ management and perception on the nasal oxygen therapy in China. Therefore, we aimed to investigate the nasal oxygen practice of ICUs in China to provide insights into future direction.

Methods

A cross-sectional survey on 10 hospitals was conducted. A self-designed questionnaire was administered to ICU nurses. Descriptive statistics, univariate, and multiple stepwise regression analyses were performed to analyze the respondents’ questionnaires.

Results

A total of 580 respondents with a response rate of 96.67% were included in this study. The average correct answer rate was 58.28%. The current status of nasal oxygen administration in ICUs in Chinese hospitals lagged behind the recommendations of related guidelines. Nurses in China were eager to learn about the updated knowledge on oxygen therapy. The gender, age, clinical experience, degree, job title, and classification of working hospitals were not related to the oxygen therapy-related knowledge scores (all P>0.05).

Conclusion

Many deficiencies are observed regarding the nasal oxygen practice in ICUs of Chinese hospitals. Increased efforts by authorities and medical staff are required to narrow the gap between the current status of oxygen practice and the recommendations from related guidelines.

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.

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.

High-Flow Nasal Cannula Therapy for Acute Hypoxemic Respiratory Failure in Adults: A Retrospective Analysis

OBJECTIVE

High-flow nasal cannula (HFNC) therapy is an oxygen delivery system. However, evidence regarding the clinical applications of HFNC is still emerging. We herein evaluated the clinical predictors of HFNC therapy success for adult patients with acute hypoxemic respiratory failure.

METHODS

We retrospectively reviewed the medical records of the subjects with acute hypoxemic respiratory failure supported by HFNC therapy in the medical intensive care unit between July 2011 and March 2013. Therapy success was defined as the avoidance of intubation. The patients' baseline characteristics and the serial changes in the respiratory parameters after HFNC therapy at 1 and 24 hours were measured.

RESULTS

Of the 75 eligible patients, 62.7% successfully avoided intubation. Overall, HFNC therapy significantly improved the physiologic parameters, such as partial pressure of arterial oxygen (PaO2), saturation of arterial oxygen (SaO2), respiratory rate (RR), and heart rate (HR), throughout the first 24 hours. After the adjustment for the other clinical variables, Acute Physiology and Chronic Health Evaluation II (APACHE II), Sequential Organ Failure Assessment (SOFA), cardiogenic pulmonary edema, and PaO2 improvement at 1 and 24 hours were associated with therapy success. The overall intensive care unit (ICU) mortality was 25.3%. However, out of 37.3% of the patients who required intubation, the ICU mortality in this proportion of patients was 67.9%. The ICU mortality in the therapy failure group was associated with the use of a vasopressor and a limited PaO2 improvement at 1 hour.

CONCLUSION

HFNC therapy showed a good compliance and the improvement of the physiologic parameters in an adult population. The failure to improve oxygenation within 24 hours was a useful predictor of intubation. Among the failure group, the vasopressor use and failed oxygenation improvement were associated with ICU mortality.

[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.

An in vitro assessment of aerosol delivery through patient breathing circuits used with medical air or a helium-oxygen mixture

BACKGROUND

The bench experiments presented herein were conducted in order to investigate the influence of carrier gas, either medical air or a helium-oxygen mixture (78% He, 22% O2), on the droplet size distribution and aerosol mass delivered from a vibrating mesh nebulizer through a patient breathing circuit.

METHODS

Droplet size distributions at the exit of the nebulizer T-piece and at the patient end of the breathing circuit were determined by laser diffraction. Additional experiments were performed to determine the effects on measured size distributions of gas humidity and of the droplet residence time during transport from the nebulizer to the laser diffraction measurement volume. Aerosol deposition in the nebulizer, breathing circuit, and on expiratory and patient filters was determined by photometry following nebulization of sodium fluoride solutions into the breathing circuit during simulated patient breathing.

RESULTS

With no humidification of the carrier gas, droplet volume median diameter (VMD) at the exit of the nebulizer T-piece was 5.5±0.1 μm for medical air, and 4.3±0.1 μm for helium-oxygen. Varying the aerosol residence time between the nebulizer and the measurement volume did not affect the measured size distributions; however, humidification of the carrier gases reduced differences in VMD at the nebulizer exit between medical air and helium-oxygen. At the patient end of the breathing circuit, droplet VMDs were 1.8±0.1 μm for medical air and 2.2±0.1 μm for helium-oxygen. The percentages of sodium fluoride recovered from the nebulizer, breathing circuit, patient filter, and expiratory filter were, respectively, 29.9±8.3, 40.4±5.6, 8.3±1.5, and 21.5±2.1% for air, and 32.6±2.2, 36.3±0.7, 12.0±1.4, and 19.1±1.1% for helium-oxygen.

CONCLUSIONS

Ventilation with helium-oxygen in place of air-oxygen mixtures can influence both the droplet size distribution and mass of nebulized aerosol delivered through patient breathing circuits. Assessment of these effects on aerosol delivery is important when incorporating helium-oxygen into patient ventilation strategies.

Small dead space heat and moisture exchangers do not impede gas exchange during noninvasive ventilation: a comparison with a heated humidifier

OBJECTIVE

Adverse respiratory and gasometrical effects have been described in patients with acute respiratory failure (ARF) undergoing noninvasive ventilation (NIV) with standard heat and moisture exchangers (HME). We decided to evaluate respiratory parameters and arterial blood gases (ABG) of patients during NIV with small dead space HME compared with heated humidifier (HH).

DESIGN

Prospective randomized crossover study.

SETTING

A 16-bed medical intensive care unit (ICU).

PATIENTS

Fifty patients receiving NIV for ARF.

MEASUREMENTS

The effects of HME and HH on respiratory rate, minute ventilation, EtCO(2), oxygen saturation, airway occlusion pressure at 0.1 s, ABG, and comfort perception were compared during two randomly determined NIV periods of 30 min. The relative impact of HME and HH on these parameters was successively compared with or without addition of a flex tube (40 and 10 patients, respectively).

MAIN RESULTS

No difference was observed between HME and HH regarding any of the studied parameters, whether or not a flex tube was added.

CONCLUSION

If one decides to humidify patients' airways during NIV, one may do so with small dead space HME or HH without altering respiratory parameters.