Effects of nasal mask leak and heated humidification on nasal mucosa in the therapy with nasal continuous positive airway pressure (nCPAP)

Nasal function and CPAP use in patients with obstructive sleep apnoea: a systematic review

PURPOSE

This systematic review was conducted to answer the following 3 questions: 'Does nasal pathology affect CPAP use?', 'What is the effect of CPAP on the nose?' and 'Does treatment of nasal pathology affect CPAP use?'.

METHODS

Pubmed and Scopus databases were searched for articles relevant to the study questions up to October 2020.

RESULTS

Sixty-three articles were selected, of which a majority were observational studies. Most studies identified a correlation between larger nasal cross-sectional area or lower nasal resistance and higher CPAP compliance or lower CPAP pressures; however, nasal symptoms at baseline did not appear to affect CPAP use. The effect of CPAP on the nose remains uncertain: while most studies suggested increased mucosal inflammation with CPAP, those investigating symptoms presented contradictory results, with some reporting an increase and others an improvement in nasal symptoms. Evidence is clearer for nasal surgery leading to an increase in CPAP compliance and a decrease in CPAP pressures, whereas there is little evidence available for the use of topical nasal steroids.

CONCLUSION

There appears to be a link between nasal volumes or nasal resistance and CPAP compliance, an increase in nasal inflammation caused by CPAP and a beneficial effect of nasal surgery on CPAP usage, but no significant effect of CPAP on nasal patency or effect of topical steroids on CPAP compliance. Results are more mitigated with regard to the effect of nasal symptoms on CPAP use and vice versa, and further research in this area would help identify patients who may benefit from additional support or treatment alongside CPAP.

Ventilator- and interface-related factors influencing patient-ventilator asynchrony during noninvasive ventilation

Patient-ventilator asynchrony (PVA) is common in patients receiving noninvasive ventilation (NIV). This occurs primarily when the triggering and cycling-off of ventilatory assistance are not synchronized with the patient's inspiratory efforts and could result in increased work of breathing and niv failure. In general, five types of asynchrony can occur during NIV: ineffective inspiratory efforts, double-triggering, auto-triggering, short-ventilatory cycling, and long-ventilatory cycling. Many factors that affect PVA are mostly related to the degree of air leakage, level of pressure support, and the type and properties of the interface used. Careful monitoring and adjustment of these factors are essential to reduce PVA and improve patient comfort. In this article, we discuss the machine and interface-related factors that influence PVA during NIV and its effect on the respiratory mechanics during pressure support ventilation, which is the ventilatory mode used most commonly during NIV. For that, we critically evaluated studies that assessed ventilator- and interface-related factors that influence PVA during NIV and proposed therapeutic solutions.

Mask humidity during CPAP: influence of ambient temperature, heated humidification and heated tubing

PURPOSE

Mucosal drying during continuous positive airway pressure (CPAP) therapy is problematic for many patients. This study assessed the influence of ambient relative humidity (rH) and air temperature (T) in winter and summer on mask humidity during CPAP, with and without mask leak, and with or without heated humidification ± heated tubing.

METHODS

CPAP (8 and 12 cmH₂O) without humidification (no humidity [nH]), with heated humidification controlled by ambient temperature and humidity (heated humidity [HH]) and HH plus heated tubing climate line (CL), with and without leakage, were compared in 18 subjects with OSA during summer and winter.

RESULTS

The absolute humidity (aH) and the T inside the mask during CPAP were significantly lower in winter versus summer under all applied conditions. Overall, absolute humidity differences between summer and winter were statistically significant in both HH and CL vs. nH (p < 0.05) in the presence and absence of mouth leak. There were no significant differences in aH between HH and CL. However, in-mask temperature during CL was higher (p < 0.05) and rH lower than during HH. In winter, CPAP with CL was more likely to keep rH constant at 80% than CPAP without humidification or with standard HH.

CONCLUSION

Clinically-relevant reductions in aH were documented during CPAP given under winter conditions. The addition of heated humidification, using a heated tube to avoid condensation is recommended to increase aH, which could be useful in CPAP users complaining of nose and throat symptoms.

Nasal airway responses to nasal continuous positive airway pressure breathing: An in-vivo pilot study

The nasal cycle, through variation in nasal airflow partitioning, allows the upper airway to accommodate the contrasting demands of air conditioning and removal of entrapped air contaminants. The purpose of this study was to investigate the influence of nasal continuous positive airway pressure (nCPAP) breathing has on both nasal airflow partitioning and nasal geometry. Using a custom-made nasal mask, twenty healthy participants had the airflow in each naris measured during normal nasal breathing followed by nCPAP breathing. Eight participants also underwent magnetic resonance imaging (MRI) of the nasal region during spontaneous nasal breathing, and then nCPAP breathing over a range of air pressures. During nCPAP breathing, a simultaneous reduction in airflow through the patent airway together with a corresponding increase in airway flow within the congested nasal airway were observed in sixteen of the twenty participants. Nasal airflow resistance is inversely proportional to airway cross-sectional area. MRI data analysis during nCPAP breathing confirmed airway cross-sectional area reduced along the patent airway while the congested airway experienced an increase in this parameter. During awake breathing, nCPAP disturbs the normal inter-nasal airflow partitioning. This could partially explain the adverse nasal drying symptoms frequently reported by many users of this therapy.

A pilot study of an in-vitro bovine trachea model of the effect of continuous positive airway pressure breathing on airway surface liquid

Background

Continuous positive air pressure (CPAP) users frequently report troublesome symptoms of airway dryness and nasal congestion. Clinical investigations have demonstrated that supplementary humidification reduces these symptoms but the reason for their occurrence remains unexplained. Investigations using human computational air-conditioning models are unable to reproduce or quantify the apparent airway drying experienced during CPAP therapy. The purpose of this study was to determine whether augmented air pressures change overall mucosal airway surface liquid (ASL) water supply and, if so, the extent of this effect.

Method

In an original in vitro experimental set up, maximal ASL supply was determined in whole bovine trachea when exposed to simulated tidal breathing stresses over a range of air pressures.

Results

At ambient pressure, the maximal supply of ASL was found to compare well to previously published data (31.2 μl/cm².hr). CPAP pressures from 5 cm H₂O above ambient were found to reduce ASL supply by 22%. Statistical analysis (n = 8) showed a significant difference existed between the ambient and CPAP results (p < 0.0001), and that there was no significant variation between all pressurized results (p = 0.716).

Conclusions

These findings provide preliminary data that ASL supply is reduced by CPAP therapy which may explain the airway drying symptoms associated with this therapy.

Clinical review: humidifiers during non-invasive ventilation--key topics and practical implications

Inadequate gas conditioning during non-invasive ventilation (NIV) can impair the anatomy and function of nasal mucosa. The resulting symptoms may have a negative effect on patients' adherence to ventilatory treatment, especially for chronic use. Several parameters, mostly technical aspects of NIV, contribute to inefficient gas conditioning. Factors affecting airway humidity during NIV include inspiratory flow, inspiratory oxygen fraction, leaks, type of ventilator, interface used to deliver NIV, temperature and pressure of inhaled gas, and type of humidifier. The correct application of a humidification system may avoid the effects of NIV-induced drying of the airway. This brief review analyses the consequences of airway dryness in patients receiving NIV and the technical tools necessary to guarantee adequate gas conditioning during ventilatory treatment. Open questions remain about the timing of gas conditioning for acute or chronic settings, the choice and type of humidification device, the interaction between the humidifier and the underlying disease, and the effects of individual humidification systems on delivered humidity.

The effects of heated humidifier in continuous positive airway pressure titration

BACKGROUND

Previous studies have shown that routine heated humidifier (HH) do not provide any benefit during continuous positive airway pressure (CPAP) titration if there are no significant naso-pharyngeal symptoms. In clinical practice, nasal diseases and upper airway symptoms are very common. This study investigates the effects of HH during CPAP titration in subjects with or without naso-pharyngeal symptoms.

METHODS

Fifty-two patients who received polysomnography with CPAP titration were randomly assigned to HH and non-HH groups. Their nasal cavity, pharynx, and naso-pharynx were evaluated before CPAP titration, and a questionnaire on subjective sensation, including naso-pharyngeal symptoms, willingness to further use CPAP, and sleep improvement, was used. Objective (e.g., leak, apnea-hypopnea index (AHI) reduction, and optimal CPAP pressure level) and subjective data were analyzed between the two groups.

RESULTS

In subjective sensation, the HH group did not have any benefit in further willingness to use CPAP and in sleep improvement, but had improved naso-pharyngeal symptoms (p = 0.043). There were no significant differences in leak, AHI reduction, and optimal CPAP pressure, even in patients with significant naso-pharyngeal symptoms.

CONCLUSION

Routine use of HH is not necessary during CPAP titration regardless of naso-pharyngeal symptoms.