Impact of nasal resistance on the distribution of apneas and hypopneas in obstructive sleep apnea

Correlation between Subjective Nasal Patency and Nasal Capacity in Young Adults: A Pilot Study with a Prototype Device-A Nasoorospirometer

Background: Nasal airway obstruction (NAO) is characterised by high resistance in the nasal cavity with a collapsible and narrowed upper airway and is an integral part of OSA pathophysiology. The literature demonstrates that the identification of high-risk OSA in the young adult population leads to the prevention of later health consequences. A nasoorospirometer is a prototype device that measures nasal capacity during inspiration. The basis for measurement is a Wheatstone bridge and a thermal anemometer. The parameters are recorded via hot wire anemometry (HTA) with velocity measurements in the airflow field. Therefore, this pilot study aimed to test the feasibility of the device by examining a young adult sample. The secondary aim was to determine whether subjective NAO correlates with nasal capacity and whether NAO corresponds with anthropometric parameters and individual risk of OSA. Methods: A group of 31 participants (mean age 24.9 years) underwent a thorough laryngological examination. The nasoorospirometer was used to measure objective NAO (nasal capacity), the NOSE scale was used to gain subjective NAO evaluation, and the Berlin Questionnaire for the risk of OSA. Results: A correlation analysis confirmed no significant associations between the subjective and objective measures (p > 0.05). Higher BMI and neck circumference are associated with lower NAO and higher nasal patency in the population of young adults (r: 0.32-0.45; p < 0.05). The risk of OSA showed no statistically significant association (p > 0.05). Conclusions: We presented three methods of NAO assessment: subjective participant evaluation, objective nasoosopirometry, and objective laryngological assessment. However, the use of a nasoorospirometer with anthropometric measures in young adults needs to be verified in future studies.

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.

Reliability and accuracy of a semi-automatic segmentation protocol of the nasal cavity using cone beam computed tomography in patients with sleep apnea

OBJECTIVES

The objectives of this study included using the cone beam computed tomography (CBCT) technology to assess: (1) intra- and inter-observer reliability of the volume measurement of the nasal cavity; (2) the accuracy of the segmentation protocol for evaluation of the nasal cavity.

MATERIALS AND METHODS

This study used test-retest reliability and accuracy methods within two different population sample groups, from Eastern Asia and North America. Thirty obstructive sleep apnea (OSA) patients were randomly selected from administrative and research oral health data archived at two dental faculties in China and Canada. To assess the reliability of the protocol, two observers performed nasal cavity volume measurement twice with a 10-day interval, using Amira software (v4.1, Visage Imaging Inc., Carlsbad, CA). The accuracy study used a computerized tomography (CT) scan of an OSA patient, who was not included in the study sample, to fabricate an anthropomorphic phantom of the nasal cavity volume with known dimensions (18.9 ml, gold standard). This phantom was scanned using one NewTom 5G (QR systems, Verona, Italy) CBCT scanner. The nasal cavity was segmented based on CBCT images and converted into standard tessellation language (STL) models. The volume of the nasal cavity was measured on the acquired STL models (18.99 ± 0.066 ml).

RESULTS

The intra-observer and inter-observer intraclass correlation coefficients for the volume measurement of the nasal cavity were 0.980-0.997 and 0.948-0.992 consecutively. The nasal cavity volume measurement was overestimated by 1.1%-3.1%, compared to the gold standard.

CONCLUSIONS

The semi-automatic segmentation protocol of the nasal cavity in patients with sleep apnea and by using cone beam computed tomography is reliable and accurate.

CLINICAL RELEVANCE

This study provides a reliable and accurate protocol for segmentation of nasal cavity, which will facilitate the clinician to analyze the images within nasoethmoidal region.

The independent role of nasal obstruction in resistant hypertension for uncontrolled hypertensive patients with obstructive sleep apnea

PURPOSE

To determine the independent predictive role of nasal obstruction in resistant hypertension (RH) in uncontrolled hypertensive patients with obstructive sleep apnea (OSA).

METHODS

This prospective cohort study comprised of 236 OSA patients with uncontrolled blood pressure (BP) using 1 or 2 classes of antihypertensive drugs visiting Sleep Medicine Center from April 2021 to March 2022. Information on demographic characteristics, comorbidities, BP control and classes of antihypertensive medication, sleep-related symptoms, Nasal Obstruction Symptom Evaluation (NOSE) Scale and sleep parameters was collected. RH incidence according to the BP control and classes of antihypertensive drugs data during the 5 month follow-up was collected.

RESULTS

After 5 month follow-up, 217 participants were included for final data analysis. Ninety-five subjects had nocturnal nasal obstruction with a higher proportion of RH (36.8% vs. 17.2%, p = 0.001) compared to those without nocturnal nasal obstruction. After adjustment for demographic characteristics, sleep-related symptoms and OSA severity, multinomial logistic regression models showed that nocturnal nasal obstruction (all ORs > 2.5, p < 0.05) or NOSE ≥ 8 (all ORs > 4.5, p < 0.05) was independently associated with a higher odds of RH. Nasal obstruction treatment improved NOSE score significantly, but did not reduce the incidence of RH significantly. Effective nasal obstruction treatment was associated with antihypertensive drugs reduction (OR 4.43; 95% CI 1.20-16.27).

CONCLUSIONS

Nasal obstruction is an independent predictor of RH in uncontrolled hypertensive patients with OSA. In addition to the treatment of OSA, assessment and treatment of nasal obstruction should be considered in the management of uncontrolled hypertensive patients with OSA.

Outcome of nasal measurements in patients with OSA - Mounting evidence of a nasal endotype

BACKGROUND

Increased nasal resistance as measured by 4-phase rhinomanometry is associated with a paucity of apneas relative to hypopneas in obstructive sleep apnea (OSA) patients. The ratio of hypopneas to apneas for a given apnea hypopnea index (AHI) may influence treatment choice. This study aimed to investigate if OSA patients with an elevated hypopnea apnea ratio are associated with differences in acoustic rhinometry measurements.

METHODS

One hundred and thirty-nine (n = 139) OSA patients (AHI >5) were enrolled in this prospective case-control study (all male). OSA Diagnosis was established through a type three sleep study. Both acoustic rhinometry and 4-phase rhinomanometry were performed on all patients at baseline and after decongestion. Possible associations between apnea-hypopnea index, oxygen desaturation index, nadir oxygen saturation, apnea index, hypopnea index, hypopnea to apnea ratio and body mass index and were analysed using multiple logistic and linear regression models.

RESULTS

The acoustic rhinometry measurements minimal cross-sectional area, total volume and minimal cross-sectional areas are significantly smaller in patients with increased nasal resistance as measured by 4-phase rhinomanometry (P < 0.01). No consistent statistically significant associations were found between the acoustic rhinometry variables, and the respiratory variables analysed in the sleep studies. OSA patients with an elevated hypopnea apnea ratio are more than 4 times more likely to present with increased nasal resistance measured by 4-phase rhinomanometry (OR = 4.4, 95% CI [1.5-13.2], P < 0.01).

CONCLUSIONS

Acoustic rhinometry is significantly associated with 4-phase rhinomanometry. However, acoustic rhinometry measurements are not associated with the respiratory indices routinely measured in OSA in a clinical setting. 4-phase rhinomanometry is a more suitable method for detecting clinically relevant nasal obstruction in obstructive sleep apnea patients.

Fraction of apnea is associated with the required continuous positive airway pressure level and reflects upper airway collapsibility in patients with obstructive sleep apnea

STUDY OBJECTIVES

We aimed to determine whether the fraction of apnea (Fapnea) could be used as an alternative index to reflect upper airway (UA) collapsibility.

METHODS

We retrospectively recruited 161 patients (16 women, mean age 47.8 years, body mass index [BMI] 28.0 kg/m², and apnea-hypopnea index [AHI] 46.4/h) with moderate to severe obstructive sleep apnea (OSA) who underwent nasal continuous positive airway pressure (CPAP) titration. The Fapnea was defined as the percentage of apneic events over the total apneic and hypopneic events during sleep in a supine position on diagnostic polysomnography. We randomly split the data (70/30) into the development and validation datasets. In the development dataset, we conducted a multiple regression analysis to assess the association of variables, including the age, sex, BMI, rapid eye movement (REM) supine AHI, and apnea with the CPAP level during supine REM sleep (REM_CPAP). Moreover, we developed an equation for predicting the CPAP level. Thereafter, we evaluated the correlation between the actual CPAP level and the value calculated using the model.

RESULTS

BMI and Fapnea were the only significant factors that predicted the REM_CPAP level (adjusted r=0.60, p<0.001) in the development dataset. The validation data revealed a significant correlation between the actual and predicted CPAP levels (r=0.69, p<0.0001). We observed similar associations during supine non-REM (NREM) sleep.

CONCLUSIONS

Fapnea could significantly predict the CPAP levels during both REM and NREM sleep, which likely reflects the UA collapsibility, independent of the BMI.

Independent Role of Nasal Congestion in Positive Airway Pressure Compliance for OSA Treatment

OBJECTIVE

To determine the independent role of nasal congestion in positive airway pressure (PAP) therapy compliance and factors associated with an unfavorable shift of PAP compliance.

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary care center.

METHODS

This follow-up study comprised 174 patients with newly diagnosed obstructive sleep apnea (OSA) who accepted PAP therapy from January 2017 to June 2019. Information was collected on basic demographics, comorbidities, sleep-related symptoms, nasal symptoms, and upper airway assessment. PAP adherence data were collected at the end of the first week and the third month.

RESULTS

After 3 months of follow-up, 147 participants were included for final data analysis. The proportion of nasal congestion (29.2% vs 52.0%, P = .005) and its severity (mean rank, 58.5 vs 75.1; P = .007) were significantly higher in the noncompliance group as compared with the compliance group. After adjustment for basic demographics, comorbidities, sleep-related symptoms or sleep study parameters, and Friedman clinical staging, multinomial logistic regression models showed that nasal congestion (all odds ratios >2.0, P < .05) was independently associated with a higher odds of PAP noncompliance. Patients with an unfavorable shift of PAP compliance were younger (mean ± SD, 47.5 ± 10.6 vs 53.1 ± 12.6 years; P = .021) and had a lower body mass index (27.2 ± 3.7 vs 29.3 ± 5.0, P = .027) than those who consistently complied. OSA severity was associated with PAP compliance, initially and in the long term.

CONCLUSION

Nasal congestion is an independent predictor of PAP noncompliance. Younger patients with lower BMI were more likely to have an unfavorable shift of PAP compliance. Initial and long-term adherence to PAP therapy was affected by OSA severity.

PAP Adherence and Nasal Resistance. A Randomized Controlled Trial of CPAPflex versus CPAP in World Trade Center Responders

Rationale: Continuous positive airway pressure (CPAP) adherence is often poor in obstructive sleep apnea (OSA) and may be influenced by nasal resistance. CPAP with a reduction of expiratory pressure (CPAPflex) may reduce discomfort in those with high nasal resistance and improve adherence in this subgroup.Objectives: To evaluate the association of positive airway pressure (PAP) treatment adherence to nasal resistance and examine if CPAPflex improves adherence over CPAP in subjects with high nasal resistance.Methods: A randomized double-blind crossover trial of 4 weeks each of CPAPflex versus CPAP in subjects exposed to World Trade Center dust with OSA stratified by nasal resistance, measured by 4-Phase Rhinomanometry.Results: Three hundred seventeen subjects with OSA (mean, apnea-hypopnea index with 4% O₂ desaturation for hypopnea = 17 ± 14/h) were randomized. Overall, PAP adherence was poor, but adherence to CPAP (n = 239; mean hours per night [95% confidence interval (CI)]), 1.97 h (1.68 to 2.26) was greater than adherence to CPAPflex (n = 249; 1.65 h [1.39 to 1.91]; difference of 0.31 h [0.03; 0.6]; P < 0.05). Contrary to our hypothesis there was no correlation between nasal resistance and adherence to CPAP (r = 0.098; P = not significant) or CPAPflex (r = 0.056; P = not significant). There was no difference in adherence between CPAP and CPAPflex (mean Δ hours [95% CI]) in subjects with low resistance (0.33 h [-0.10 to 0.76]) or high nasal resistance (0.26 h [-0.14 to 0.66]). No significant differences were observed in any of the secondary outcomes between PAP modes.Conclusions: Contrary to expectations, our data do not show better adherence to CPAPflex than to CPAP in subjects with high or low nasal resistance and do show clinically insignificant better adherence overall with CPAP.Clinical trial registered with www.clinicaltrials.gov (NCT01753999).