Usefulness of rhinomanometry in the identification and treatment of patients with obstructive sleep apnoea: an algorithm for predicting the relationship between nasal resistance and continuous positive airway pressure. a retrospective study

Computational Rhinology: Unraveling Discrepancies between In Silico and In Vivo Nasal Airflow Assessments for Enhanced Clinical Decision Support

Computational rhinology is a specialized branch of biomechanics leveraging engineering techniques for mathematical modelling and simulation to complement the medical field of rhinology. Computational rhinology has already contributed significantly to advancing our understanding of the nasal function, including airflow patterns, mucosal cooling, particle deposition, and drug delivery, and is foreseen as a crucial element in, e.g., the development of virtual surgery as a clinical, patient-specific decision support tool. The current paper delves into the field of computational rhinology from a nasal airflow perspective, highlighting the use of computational fluid dynamics to enhance diagnostics and treatment of breathing disorders. This paper consists of three distinct parts-an introduction to and review of the field of computational rhinology, a review of the published literature on in vitro and in silico studies of nasal airflow, and the presentation and analysis of previously unpublished high-fidelity CFD simulation data of in silico rhinomanometry. While the two first parts of this paper summarize the current status and challenges in the application of computational tools in rhinology, the last part addresses the gross disagreement commonly observed when comparing in silico and in vivo rhinomanometry results. It is concluded that this discrepancy cannot readily be explained by CFD model deficiencies caused by poor choice of turbulence model, insufficient spatial or temporal resolution, or neglecting transient effects. Hence, alternative explanations such as nasal cavity compliance or drag effects due to nasal hair should be investigated.

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.

Nasal Obstruction as a Potential Factor Contributing to Hypoxemia in Obstructive Sleep Apnea

PURPOSE

This study aimed to evaluate the correlation between nasal resistance and oxygen desaturation to better elucidate the role of nasal obstruction in the pathophysiology of obstructive sleep apnea (OSA).

PATIENTS AND METHODS

Eighty-eight OSA patients aged between 22 and 77 years were enrolled in this study. Nasal resistance was measured at pressures of 75, 150, and 300 Pa, with the patients first in the seated position than in the supine position. Relationships between the oximetric variables and nasal resistance in the seated and supine positions were analyzed.

RESULTS

From seated to supine position, a statistically significant increase in nasal resistance was observed at pressures of 75 and 150 Pa (p=0.001 and p=0.006, respectively). Significant positive correlations were noted between nasal resistance in the supine position at 75 Pa (SupineNR75) and oximetry variables, including oxygen desaturation index (ODI, p=0.015) and the percentage of total time with oxygen saturation level lower than 90% (T < 90%, p=0.012). However, significant positive correlations existed only in moderate to severe OSA when the study group was further divided into two subgroups (mild vs moderate to severe OSA). Body mass index (β = 0.476, p<0.001) and SupineNR75 (β = 0.303, p=0.004) were identified as independent predictors for increased ODI.

CONCLUSION

Nasal resistance in the supine position measured at 75 Pa significantly correlated with the severity of oxygen desaturation. Therefore, nasal obstruction may play an important role in the pathophysiology of hypoxemia in OSA patients, especially in patients with moderate to severe OSA.

Total nasal airway resistance while sitting predicts airway collapse when lying down

BACKGROUND

Nasal obstruction when lying down is a common complaint in patients with chronic nasal obstruction, but rhinomanometry is typically performed in the sitting position. This study aimed to analyse whether adding rhinomanometry in a supine position is a useful examination.

METHOD

A total of 41 patients with chronic nasal obstruction underwent rhinomanometry and acoustic rhinometry, sitting and supine, before and after decongestion, as well as an over-night polygraphy.

RESULTS

Total airway resistance was measurable in a supine position in 48 per cent (14 of 29) of the patients with total airway resistance of equal to or less than 0.3 Pa/cm3/second when sitting and in none (0 of 12) of the patients with total nasal airway resistance of more than 0.3 Pa/cm3/second when sitting. After decongestion, this increased to 83 per cent and 58 per cent, respectively.

CONCLUSION

Increased nasal resistance when sitting predicts nasal breathing problems when supine. Rhinomanometry in a supine position should be performed to diagnose upper airway collapse when supine.

Role of rhinomanometry in the prediction of therapeutic positive airway pressure for obstructive sleep apnea

Background

This study was conducted to evaluate the relationship between nasal resistance in different posture and optimal positive airway pressure (PAP) level. Other potential factors were also assessed for possible influence on PAP pressure.

Methods

Forty- three patients diagnosed with obstructive sleep apnea (OSA) were prospectively recruited in this study. Nasal resistance was assessed by active anterior rhinomanometry in a seated position and then in a supine position at pressures of 75, 150, and 300 pascal. The factors correlating with PAP pressure were analyzed, including nasal resistance and patients’ clinical data.

Results

Univariate analysis revealed that PAP pressure was correlated to nasal resistance in the supine position at 75 and 150 pascal (SupineNR75 and SupineNR150) (P = 0.019 and P = 0.004 in Spearman’s correlation coefficient analysis), but not correlated to nasal resistance in the seated position at different pressures or in the supine position at 300 pascal. The multiple linear regression analysis revealed that both SupineNR150 and body mass index (BMI) significantly predicted PAP pressure (β = 0.308, p = 0.044; β = 0.727, p = 0.006). The final PAP pressure predictive model was:

PAP pressure = 0.29 BMI + 2.65 SupineNR150 + 2.11.

Conclusions

Nasal resistance in the supine position measured at 150 pascal may provide valuable information regarding optimal PAP pressure. Rhinomanometry should be included in the treatment algorithm of OSA patients when PAP therapy is considered.