Influence of mouth opening on oropharyngeal humidification and temperature in a bench model of neonatal continuous positive airway pressure

Alterations in Oral-Nasal-Pharyngeal Microbiota and Salivary Proteins in Mouth-Breathing Children

Mouth breathing induces a series of diseases, while the influence on microbiota of oral cavity and salivary proteins remains unknown. In this study, for the first time, profiles of oral-nasal-pharyngeal microbiota among mouth-breathing children (MB group, n = 10) were compared with paired nose-breathing children (NB group, n = 10) using 16S ribosomal DNA (rDNA) (V3-V4 region) high-throughput sequencing. The differentially expressed salivary proteins were revealed using label-free quantification (LFQ) method, and their associations with bacterial abundance were measured by canonical correspondence analysis (CCA). The overall bacterial profiles differed between the two groups, and the differences were related to the duration of mouth breathing. The diversity of oral-pharyngeal microbiota was significantly higher, and the nasal-pharyngeal species tended to be consistent (unweighted UniFrac, p = 0.38) in the MB group. Opportunistic pathogens were higher in relative abundance as follows: Acinetobacter in the anterior supragingival plaque, Neisseria in unstimulated saliva, Streptococcus pneumoniae in the pharynx, and Stenotrophomonas in the nostrils. The expression level of oxidative-stress-related salivary proteins (lactoylglutathione lyase and peroxiredoxin-5) were upregulated, while immune-related proteins (integrin alpha-M and proteasome subunit alpha type-1) were downregulated in MB group. The differentially expressed proteins were associated with specific bacteria, indicating their potentials as candidate biomarkers for the diagnosis, putatively early intervention, and therapeutic target of mouth breathing. This study showed that mouth breathing influences the oral-nasal-pharyngeal microbiota and enriches certain pathogens, accompanied with the alterations in the salivary environment. Further research on the pathological mechanisms and dynamic changes in longitudinal studies are warranted.

Temperature and Humidity Associated With Artificial Ventilation in the Premature Infant: An Integrative Review of the Literature

BACKGROUND

Approximately half of the 55,000 very low birth-weight infants (<1500 g) born in the United States each year develop bronchopulmonary dysplasia (BPD). Many etiologies have been associated with the development of BPD, including aberrant temperature/humidity levels of artificial ventilation.

PURPOSE

The purpose of this literature review is to explore what is known regarding inspired air temperature/humidity levels from artificial ventilation in very premature infants, focusing on what levels these infants actually receive, and what factors impact these levels.

METHODS/SEARCH STRATEGY

PubMed, CINAHL, Scopus, and Web of Science were searched. Of the 830 articles retrieved, 23 were synthesized for study purpose, sample/study design, and temperature/humidity findings.

FINDINGS/RESULTS

Heating and humidification practices studied in neonatal ventilation did not maintain recommended levels. In addition, human neonatal studies and noninvasive neonatal ventilation research were limited. Furthermore, ventilation settings, environmental temperatures, and mouth position (in noninvasive ventilation) were found to impact temperature/humidity levels.

IMPLICATIONS FOR PRACTICE

Environmental temperatures and ventilatory settings merit consideration during artificial ventilation. In addition, aberrant temperature/humidity levels may impact infant body temperature stability; thus, employing measures to ensure adequate thermoregulation while receiving artificial ventilation must be a priority.

IMPLICATIONS FOR RESEARCH

This review underscores the need for further research into current warming and humidification techniques for invasive and noninvasive neonatal ventilation. A focus on human studies and the impact of aberrant levels on infant body temperature are needed. Future research may provide management options for achieving and maintaining target temperature/humidity parameters, thus preventing the aberrant levels associated with BPD.

Differential impact of flow and mouth leak on oropharyngeal humidification during high-flow nasal cannula: a neonatal bench study

BACKGROUND

Heated humidification is paramount during neonatal high-flow nasal cannula (HFNC) therapy. However, there is little knowledge about the influence of flow rate and mouth leak on oropharyngeal humidification and temperature.

METHODS

The effect of the Optiflow HFNC on oropharyngeal gas conditioning was investigated at flow rates of 4, 6 and 8 L min^-1 with and without mouth leak in a bench model simulating physiological oropharyngeal air conditions during spontaneous breathing. Temperature and absolute humidity (AH) were measured using a digital thermo-hygrosensor.

RESULTS

Without mouth leak, oropharyngeal temperature and AH increased significantly with increasing flow (P < 0.001). Mouth leak did not affect this increase up to 6 L min^-1, but at 8 L min^-1, temperature and AH plateaued, and the effect of mouth leak became statistically significant (P < 0.001).

CONCLUSIONS

Mouth leak during HFNC had a negative impact on oropharyngeal gas conditioning when high flows were applied. However, temperature and AH always remained clinically acceptable.

Nasal high-frequency oscillatory ventilation impairs heated humidification: A neonatal bench study

OBJECTIVE

Nasal high-frequency oscillatory ventilation (nHFOV) is a novel mode of non-invasive ventilation used in neonates. However, upper airway obstructions due to viscous secretions have been described as specific adverse effects. We hypothesized that high-frequency oscillations reduce air humidity in the oropharynx, resulting in upper airway desiccation. Therefore, we aimed to investigate the effects of nHFOV ventilatory settings on oropharyngeal gas conditions.

METHODS

NHFOV or nasal continuous positive airway pressure (nCPAP) was applied, along with heated humidification, to a previously established neonatal bench model that simulates oropharyngeal gas conditions during spontaneous breathing through an open mouth. A digital thermo-hygro sensor measured oropharyngeal temperature (T) and humidity at various nHFOV frequencies (7, 10, 13 Hz), amplitudes (10, 20, 30 cmH₂ O), and inspiratory-to-expiratory (I:E) ratios (25:75, 33:66, 50:50), and also during nCPAP.

RESULTS

Relative humidity was always >99%, but nHFOV resulted in lower mean T and absolute humidity (AH) in comparison to nCPAP (P < 0.001). Specifically, decreasing the nHFOV frequency and increasing nHFOV amplitude caused a decline in T and AH (P < 0.001). Mean T and AH were highest during nCPAP (T 34.8 ± 0.6°C, AH 39.3 ± 1.3 g · m^-3 ) and lowest during nHFOV at a frequency of 7 Hz and an amplitude of 30 cmH₂ O (T 32.4 ± 0.3°C, AH 34.7 ± 0.5 g · m^-3 ). Increasing the I:E ratio also reduced T and AH (P = 0.03).

CONCLUSION

Intensified nHFOV settings with low frequencies, high amplitudes, and high I:E ratios may place infants at an increased risk of upper airway desiccation. Future studies should investigate strategies to optimize heated humidification during nHFOV.