Effects on upper airway collapsibility of presence of a pharyngeal catheter

The Effect of Simulated Obstructive Apneas on Mechanical Characteristics of Lower Airways in Individuals with Asthma

Increased negative intrathoracic pressure that occurs during pharyngeal obstruction can increase thoracic fluid volume that may contribute to lower airway narrowing in individuals with obstructive sleep apnea (OSA) and asthma. Our previous study showed that fluid accumulation in the thorax induced by simulated OSA can increase total respiratory resistance. However, the effect of fluid shift on lower airway narrowing has not been investigated. To examine the effect of fluid accumulation in the thorax on the resistance of the lower airway. Non-asthma participants and individuals with (un)controlled asthma were recruited and underwent a single-day experiment. A catheter with six pressure sensors was inserted through the nose to continuously measure pressure at different sites of the airway, while a pneumotachograph was attached to a mouthpiece to record airflow. To simulate obstructive apneas, participants performed 25 Mueller maneuvers (MMs) while lying supine. Using the recordings of pressure sensor and airflow, total respiratory (RT), lower respiratory components (RL), and upper airway (RUA) resistances were calculated before and after MMs. Generalized estimation equation method was used to find the predictors of RL among variables including age, sex, body mass index, and the effect of MMs and asthma. Eighteen participants were included. Performing MMs significantly increased RT (2.23 ± 2.08 cmH2O/L/s, p = 0.003) and RL (1.52 ± 2.00 cmH2O/L/s, p = 0.023) in participants with asthma, while only RL was increased in non-asthma group (1.96 ± 1.73 cmH2O/L/s, p = 0.039). We found the model with age, and the effect of MMs and asthma severity generated the highest correlation (R2 = 0.69, p < 0.001). We provide evidence that fluid accumulation in the thorax caused by excessive intrathoracic pressure increases RL in both non-asthma and asthma groups. The changes in RL were related to age, having asthma and the effect of simulated OSA. This can explain the interrelationship between OSA and asthma.

Obstructive sleep apnea diagnosis and beyond using portable monitors

Obstructive sleep apnea (OSA) is a chronic sleep and breathing disorder with significant health complications, including cardiovascular disease and neurocognitive impairments. To ensure timely treatment, there is a need for a portable, accurate and rapid method of diagnosing OSA. This review examines the use of various physiological signals used in the detection of respiratory events and evaluates their effectiveness in portable monitors (PM) relative to gold standard polysomnography. The primary objective is to explore the relationship between these physiological parameters and OSA, their application in calculating the apnea hypopnea index (AHI), the standard metric for OSA diagnosis, and the derivation of non-AHI metrics that offer additional diagnostic value. It is found that increasing the number of parameters in PMs does not necessarily improve OSA detection. Several factors can cause performance variations among different PMs, even if they extract similar signals. The review also highlights the potential of PMs to be used beyond OSA diagnosis. These devices possess parameters that can be utilized to obtain endotypic and other non-AHI metrics, enabling improved characterization of the disorder and personalized treatment strategies. Advancements in PM technology, coupled with thorough evaluation and validation of these devices, have the potential to revolutionize OSA diagnosis, personalized treatment, and ultimately improve health outcomes for patients with OSA. By identifying the key factors influencing performance and exploring the application of PMs beyond OSA diagnosis, this review aims to contribute to the ongoing development and utilization of portable, efficient, and effective diagnostic tools for OSA.

Objective Pharyngeal Phenotyping in Obstructive Sleep Apnea With High-Resolution Manometry

OBJECTIVE

Drug-induced sleep endoscopy (DISE) is a commonly used diagnostic tool for surgical procedural selection in obstructive sleep apnea (OSA), but it is expensive, subjective, and requires sedation. Here we present an initial investigation of high-resolution pharyngeal manometry (HRM) for upper airway phenotyping in OSA, developing a software system that reliably predicts pharyngeal sites of collapse based solely on manometric recordings.

STUDY DESIGN

Prospective cross-sectional study.

SETTING

An academic sleep medicine and surgery practice.

METHODS

Forty participants underwent simultaneous HRM and DISE. A machine learning algorithm was constructed to estimate pharyngeal level-specific severity of collapse, as determined by an expert DISE reviewer. The primary outcome metrics for each level were model accuracy and F1-score, which balances model precision against recall.

RESULTS

During model training, the average F1-score across all categories was 0.86, with an average weighted accuracy of 0.91. Using a holdout test set of 9 participants, a K-nearest neighbor model trained on 31 participants attained an average F1-score of 0.96 and an average accuracy of 0.97. The F1-score for prediction of complete concentric palatal collapse was 0.86.

CONCLUSION

Our findings suggest that HRM may enable objective and dynamic mapping of the pharynx, opening new pathways toward reliable and reproducible assessment of this complex anatomy in sleep.

Critical to Know Pcrit: A Review on Pharyngeal Critical Closing Pressure in Obstructive Sleep Apnea

It is crucial to understand the underlying pathophysiology of obstructive sleep apnea (OSA). Upper airway collapsibility is an important pathophysiological factor that affects the upper airway in OSA. The aim of the current study was to review the existing body of knowledge on the pharyngeal collapsibility in OSA. After a thorough search through Medline, PubMed, Scopus, and Web of science, the relevant articles were found and used in this study. Critical closing pressure (Pcrit) is the gold standard measure for the degree of collapsibility of the pharyngeal airway. Various physiological factors and treatments affect upper airway collapsibility. Recently, it has been shown that the baseline value of Pcrit is helpful in the upfront selection of therapy options. The standard techniques to measure Pcrit are labor-intensive and time-consuming. Therefore, despite the importance of Pcrit, it is not routinely measured in clinical practice. New emerging surrogates, such as finite element (FE) modeling or the use of peak inspiratory flow measurements during a routine overnight polysomnography, may enable clinicians to have an estimate of the pharyngeal collapsibility. However, validation of these techniques is needed.

Comparison of Drug-Induced Sleep Endoscopy and Natural Sleep Endoscopy in the Assessment of Upper Airway Pathophysiology During Sleep: Protocol and Study Design

Study Objectives: Obstructive sleep apnea (OSA) is increasingly recognized as a complex and heterogenous disorder. As a result, a "one-size-fits-all" management approach should be avoided. Therefore, evaluation of pathophysiological endotyping in OSA patients is emphasized, with upper airway collapse during sleep as one of the main features. To assess the site(s) and pattern(s) of upper airway collapse, natural sleep endoscopy (NSE) is defined as the gold standard. As NSE is labor-intensive and time-consuming, it is not feasible in routine practice. Instead, drug-induced sleep endoscopy (DISE) is the most frequently used technique and can be considered as the clinical standard. Flow shape and snoring analysis are non-invasive measurement techniques, yet are still evolving. Although DISE is used as the clinical alternative to assess upper airway collapse, associations between DISE and NSE observations, and associated flow and snoring signals, have not been quantified satisfactorily. In the current project we aim to compare upper airway collapse identified in patients with OSA using endoscopic techniques as well as flow shape analysis and analysis of tracheal snoring sounds between natural and drug-induced sleep. Methods: This study is a blinded prospective comparative multicenter cohort study. The study population will consist of adult patients with a recent diagnosis of OSA. Eligible patients will undergo a polysomnography (PSG) with NSE overnight and a DISE within 3 months. During DISE the upper airway is assessed under sedation by an experienced ear, nose, throat (ENT) surgeon using a flexible fiberoptic endoscope in the operating theater. In contrast to DISE, NSE is performed during natural sleep using a pediatric bronchoscope. During research DISE and NSE, the standard set-up is expanded with additional PSG measurements, including gold standard flow and analysis of tracheal snoring sounds. Conclusions: This project will be one of the first studies to formally compare collapse patterns during natural and drug-induced sleep. Moreover, this will be, to the authors' best knowledge, the first comparative research in airflow shape and tracheal snoring sounds analysis between DISE and NSE. These novel and non-invasive diagnostic methods studying upper airway mechanics during sleep will be simultaneously validated against DISE and NSE. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT04729478.

Natural sleep endoscopy in obstructive sleep apnea: A systematic review

This study's objective is to systematically review the literature on natural sleep endoscopy (NSE), including the set-up, different scoring systems, visualized collapse patterns during natural sleep, additional measurements, and comparison of upper airway collapse between NSE and drug-induced sleep endoscopy (DISE). A computerized search on Medline, Web of Science and the Cochrane library was conducted, obtaining 39 hits. Ten prospective studies were included in which NSE was performed in adults with obstructive sleep apnea (OSA). This study's findings suggest the soft palate to be the most frequent site of obstruction (58.8 %), followed by the tongue base (43.2 %), lateral walls (29.9 %), and epiglottis (22.4 %), which is in line with previous findings during DISE. Based on this literature review, the authors conclude that at this stage high quality, comparative research between DISE and NSE is missing. To adequately compare findings between OSA patients, endoscopic classification of upper airway collapse should be standardized. Non-invasive predictive tools to determine pharyngeal collapse are currently under investigation and may obviate the need for invasive endoscopy. This review highlights the contribution of NSE in validating such novel diagnostic methods and in studying upper airway mechanics in a research setting, yet larger and adequately powered studies are needed.

Frequency of flow limitation using airflow shape

STUDY OBJECTIVES

The presence of flow limitation during sleep is associated with adverse health consequences independent of obstructive sleep apnea (OSA) severity (apnea-hypopnea index, AHI), but remains extremely challenging to quantify. Here we present a unique library and an accompanying automated method that we apply to investigate flow limitation during sleep.

METHODS

A library of 117,871 breaths (N=40 participants) were visually classified (certain flow limitation, possible flow limitation, normal) using airflow shape and physiological signals (ventilatory drive per intra-esophageal diaphragm EMG). An ordinal regression model was developed to quantify flow limitation certainty using flow-shape features (e.g. flattening, scooping); breath-by-breath agreement (Cohen's ƙ) and overnight flow limitation frequency (R 2, %breaths in certain or possible categories during sleep) were compared against visual scoring. Subsequent application examined flow limitation frequency during arousals and stable breathing, and associations with ventilatory drive.

RESULTS

The model (23 features) assessed flow limitation with good agreement (breath-by-breath ƙ=0.572, p<0.001) and minimal error (overnight flow limitation frequency R 2=0.86, error=7.2%). Flow limitation frequency was largely independent of AHI (R 2=0.16) and varied widely within individuals with OSA (74[32-95]%breaths, mean[range], AHI>15/hr, N=22). Flow limitation was unexpectedly frequent but variable during arousals (40[5-85]%breaths) and stable breathing (58[12-91]%breaths), and was associated with elevated ventilatory drive (R 2=0.26-0.29; R 2<0.01 AHI v. drive).

CONCLUSIONS

Our method enables quantification of flow limitation frequency, a key aspect of obstructive sleep-disordered breathing that is independent of the AHI and often unavailable. Flow limitation frequency varies widely between individuals, is prevalent during arousals and stable breathing, and reveals elevated ventilatory drive.

A validation study of an esophageal probe-based polygraph against polysomnography in obstructive sleep apnea

STUDY OBJECTIVES

The aim of this study was to validate the automatically scored results of an esophageal probe-based polygraph system (ApneaGraph® Spiro) against manually scored polysomnography (Nox A1, PSG) results. We compared the apnea-hypopnea index, oxygen saturation index, and respiratory disturbance index of the devices.

METHODS

Consenting patients, referred for obstructive sleep apnea workup, were tested simultaneously with the ApneaGraph® Spiro and Nox A1® polysomnograph. Each participant made one set of simultaneous registrations for one night. PSG results were scored independently. Apnea-hypopnea index, oxygen desaturation index, and respiratory disturbance index were compared using Pearson's correlation and scatter plots. Sensitivity, specificity, and positive likelihood ratio of all indices at 5, 15, and 30 were calculated.

RESULTS

A total of 83 participants had successful registrations. The apnea-hypopnea index showed sensitivity of 0.83, specificity of 0.95, and a positive likelihood ratio of 5.11 at an index cutoff of 15. At a cutoff of 30, the positive likelihood ratio rose to 31.43. The respiratory disturbance index showed high sensitivity (> 0.9) at all cutoffs, but specificity was below 0.5 at all cutoffs. Scatterplots revealed overestimation in mild OSA and underestimation in severe OSA for all three indices.

CONCLUSIONS

The ApneaGraph® Spiro performed acceptably when OSA was defined by an AHI of 15. The equipment overestimated mild OSA and underestimated severe OSA, compared to the PSG.

Myoelectric characteristics of tensor palatini and collapsibility of upper airway in OSA patients with different phenotypes under DISE

OBJECTIVE

This study aims to evaluate the combination of myoelectric characteristics of tensor palatini muscle (TP) and collapsibility of upper airway in obstructive sleep apnea (OSA) patients with different external phenotypes of collapse pattern at velum level under drug-induced sleep endoscopy (DISE).

STUDY DESIGN

Case series with planned data collection.

SETTING

Operation room.

SUBJECTS AND METHODS

36 mainly collapse pattern at velum level OSA subjects underwent DISE with synchronous tensor palatini electromyograms (TP EMG), and polysomnography (ALICE 6). According to the phenotype of collapse pattern at velum level in DISE, the subjects were divided into group 1 (concentric collapse), group 2 (anteroposterior collapse), and group 3 (lateral collapse). Each group consisted of 13, 14, and 9 subjects, respectively, and was observed the electromyographic indexes at awake, sleep onset, during apnea and the third respiratory cycle after apnea. The active and passive upper airway critical closing pressure (Pcrit) of each group were measured at the same time, and the difference of neuromuscular response between different groups was evaluated.

RESULTS

In tonic TPEMG, group 1 showed the highest value during awake and sleep onset, while group 2 was the highest during apnea and after apnea. In peak TPEMG, group 1 showed the highest value during awake. Group 2 showed the highest value during other states. In passive Pcrit and D value (difference between passive Pcrit and active Pcrit), group 2 was the highest, while group 1 was the highest in active Pcrit. Difference was statistically significant.

CONCLUSIONS

Under different states of awake, sleep onset, apnea and after apnea, the response force of tensor palatini muscle of OSA subjects with different phenotypes under DISE was different. Group 1 showed the highest EMG values only when awake and sleep onset, and it was most prone to collapse. Group 2 had the highest anatomical load (passive Pcrit) and the highest neuromuscular compensatory effect (D value).

Comparison of upper airway obstruction during zolpidem-induced sleep and propofol-induced sleep in patients with obstructive sleep apnea: a pilot study

STUDY OBJECTIVES

Drug-induced sleep endoscopy (DISE) using propofol is commonly used to identify the pharyngeal structure involved in collapse among patients with obstructive sleep apnea. DISE has never been compared with zolpidem-induced sleep endoscopy. We hypothesized that propofol at recommended sedation levels does not influence upper airway collapsibility nor the frequency of multilevel pharyngeal collapse as compared with zolpidem-induced sleep.

METHODS

Twenty-one patients with obstructive sleep apnea underwent polysomnography and sleep endoscopy during zolpidem-induced sleep and during DISE with propofol. A propofol target-controlled infusion was titrated to achieve a bispectral index between 50 and 70. Airway collapsibility was estimated and compared in both conditions by peak inspiratory flow and the magnitude of negative effort dependence. Respiratory drive was estimated by the difference between end-expiratory and peak-negative inspiratory pharyngeal pressure (driving pressure). Site and configuration of pharyngeal collapse during zolpidem-induced sleep and DISE with propofol were compared.

RESULTS

The frequency of multilevel collapse during zolpidem-induced sleep was similar to that observed during DISE with propofol (72% vs 86%, respectively; difference: 14%; 95% confidence interval: -12% to 40%; P = .453). The endoscopic classification of pharyngeal collapse during both conditions were similar. Peak inspiratory flow, respiratory drive (effect size: 0.05 and 0.03, respectively), and negative effort dependence (difference: -6%; 95% confidence interval: -16% to 4%) were also similar in both procedures.

CONCLUSIONS

In this pilot study, recommended propofol doses did not significantly increase multilevel pharyngeal collapse or affect upper airway collapsibility and respiratory drive as compared with zolpidem-induced sleep.

CLINICAL TRIAL REGISTRATION

Registry: clinicaltrials.gov; Name: Natural and Drug Sleep Endoscopy; URL: https://clinicaltrials.gov/ct2/show/study/NCT03004014; Identifier: NCT03004014.

An assessment of a simple clinical technique to estimate pharyngeal collapsibility in people with obstructive sleep apnea

Study Objectives

Quantification of upper airway collapsibility in obstructive sleep apnea (OSA) could help inform targeted therapy decisions. However, current techniques are clinically impractical. The primary aim of this study was to assess if a simple, novel technique could be implemented as part of a continuous positive airway pressure (CPAP) titration study to assess pharyngeal collapsibility.

Methods

A total of 35 participants (15 female) with OSA (mean ± SD apnea–hypopnea index = 35 ± 19 events/h) were studied. Participants first completed a simple clinical intervention during a routine CPAP titration, where CPAP was transiently turned off from the therapeutic pressure for ≤5 breaths/efforts on ≥5 occasions during stable non-rapid eye movement (non-REM) sleep for quantitative assessment of airflow responses (%peak inspiratory flow [PIF] from preceding 5 breaths). Participants then underwent an overnight physiology study to determine the pharyngeal critical closing pressure (Pcrit) and repeat transient drops to zero CPAP to assess airflow response reproducibility.

Results

Mean PIF of breaths 3–5 during zero CPAP on the simple clinical intervention versus the physiology night were similar (34 ± 29% vs. 28 ± 30% on therapeutic CPAP, p = 0.2; range 0%–90% vs. 0%–95%). Pcrit was −1.0 ± 2.5 cmH2O (range −6 to 5 cmH2O). Mean PIF during zero CPAP on the simple clinical intervention and the physiology night correlated with Pcrit (r = −0.7 and −0.9, respectively, p &lt; 0.0001). Receiver operating characteristic curve analysis indicated significant diagnostic utility for the simple intervention to predict Pcrit &lt; −2 and &lt; 0 cmH2O (AUC = 0.81 and 0.92), respectively.

Conclusions

A simple CPAP intervention can successfully discriminate between patients with and without mild to moderately collapsible pharyngeal airways. This scalable approach may help select individuals most likely to respond to non-CPAP therapies.

Upper Airway Collapsibility during Dexmedetomidine and Propofol Sedation in Healthy Volunteers: A Nonblinded Randomized Crossover Study

BACKGROUND

Dexmedetomidine is a sedative promoted as having minimal impact on ventilatory drive or upper airway muscle activity. However, a trial recently demonstrated impaired ventilatory drive and induction of apneas in sedated volunteers. The present study measured upper airway collapsibility during dexmedetomidine sedation and related it to propofol.

METHODS

Twelve volunteers (seven female) entered this nonblinded, randomized crossover study. Upper airway collapsibility (pharyngeal critical pressure) was measured during low and moderate infusion rates of propofol or dexmedetomidine. A bolus dose was followed by low (0.5 μg · kg · h or 42 μg · kg · min) and moderate (1.5 μg · kg · h or 83 μg · kg · min) rates of infusion of dexmedetomidine and propofol, respectively.

RESULTS

Complete data sets were obtained from nine volunteers (median age [range], 46 [23 to 66] yr; body mass index, 25.4 [20.3 to 32.4] kg/m). The Bispectral Index score at time of pharyngeal critical pressure measurements was 74 ± 10 and 65 ± 13 (mean difference, 9; 95% CI, 3 to 16; P = 0.011) during low infusion rates versus 57 ± 16 and 39 ± 12 (mean difference, 18; 95% CI, 8 to 28; P = 0.003) during moderate infusion rates of dexmedetomidine and propofol, respectively. A difference in pharyngeal critical pressure during sedation with dexmedetomidine or propofol could not be shown at either the low or moderate infusion rate. Median (interquartile range) pharyngeal critical pressure was -2.0 (less than -15 to 2.3) and 0.9 (less than -15 to 1.5) cm H2O (mean difference, 0.9; 95% CI, -4.7 to 3.1) during low infusion rates (P = 0. 595) versus 0.3 (-9.2 to 1.4) and -0.6 (-7.7 to 1.3) cm H2O (mean difference, 0.0; 95% CI, -2.1 to 2.1; P = 0.980) during moderate infusion of dexmedetomidine and propofol, respectively. A strong linear relationship between pharyngeal critical pressure during dexmedetomidine and propofol sedation was evident at low (r = 0.82; P = 0.007) and moderate (r = 0.90; P < 0.001) infusion rates.

CONCLUSIONS

These observations suggest that dexmedetomidine sedation does not inherently protect against upper airway obstruction.

Preoperative identification of children at high risk of obstructive sleep apnea

Obstructive sleep apnea is a common childhood disorder which can lead to serious health problems if left untreated. Enlarged adenoid and tonsils are the commonest causes, and adenotonsillectomy is the recommended first line of treatment. Obstructive sleep apnea poses as an anesthetic challenge, and it is a well-known risk factor for perioperative adverse events. The presence and severity of an obstructive sleep apnea diagnosis will influence anesthesia, pain management, and level of monitoring in recovery period. Preoperative obstructive sleep apnea assessment is necessary, and anesthetists are ideally placed to do so. Currently, there is no standardized approach to the best method of preoperative screening for obstructive sleep apnea. Focused history, clinical assessments, and knowledge regarding the strengths and limitations of available obstructive sleep apnea assessment tools will help recognize a child with obstructive sleep apnea in the preoperative setting.

Effect of Sleeping Position on Upper Airway Patency in Obstructive Sleep Apnea Is Determined by the Pharyngeal Structure Causing Collapse

Objectives

In some patients, obstructive sleep apnea (OSA) can be resolved with improvement in pharyngeal patency by sleeping lateral rather than supine, possibly as gravitational effects on the tongue are relieved. Here we tested the hypothesis that the improvement in pharyngeal patency depends on the anatomical structure causing collapse, with patients with tongue-related obstruction and epiglottic collapse exhibiting preferential improvements.

Methods

Twenty-four OSA patients underwent upper airway endoscopy during natural sleep to determine the pharyngeal structure associated with obstruction, with simultaneous recordings of airflow and pharyngeal pressure. Patients were grouped into three categories based on supine endoscopy: Tongue-related obstruction (posteriorly located tongue, N = 10), non-tongue related obstruction (collapse due to the palate or lateral walls, N = 8), and epiglottic collapse (N = 6). Improvement in pharyngeal obstruction was quantified using the change in peak inspiratory airflow and minute ventilation lateral versus supine.

Results

Contrary to our hypothesis, patients with tongue-related obstruction showed no improvement in airflow, and the tongue remained posteriorly located while lateral. Patients without tongue involvement showed modest improvement in airflow (peak flow increased 0.07 L/s and ventilation increased 1.5 L/min). Epiglottic collapse was virtually abolished with lateral positioning and ventilation increased by 45% compared to supine position.

Conclusions

Improvement in pharyngeal patency with sleeping position is structure specific, with profound improvements seen in patients with epiglottic collapse, modest effects in those without tongue involvement and-unexpectedly-no effect in those with tongue-related obstruction. Our data refute the notion that the tongue falls back into the airway during sleep via gravitational influences.

Airflow Shape Is Associated With the Pharyngeal Structure Causing OSA

BACKGROUND

OSA results from the collapse of different pharyngeal structures (soft palate, tongue, lateral walls, and epiglottis). The structure involved in collapse has been shown to impact non-CPAP OSA treatment. Different inspiratory airflow shapes are also observed among patients with OSA. We hypothesized that inspiratory flow shape reflects the underlying pharyngeal structure involved in airway collapse.

METHODS

Subjects with OSA were studied with a pediatric endoscope and simultaneous nasal flow and pharyngeal pressure recordings during natural sleep. The mechanism causing collapse was classified as tongue-related, isolated palatal, lateral walls, or epiglottis. Flow shape was classified according to the degree of negative effort dependence (NED), defined as the percent reduction in inspiratory flow from peak to plateau.

RESULTS

Thirty-one subjects with OSA (mean apnea-hypopnea index score ± SD, 54 ± 27 events/h) who were 50 ± 9 years of age were studied. NED was associated with the structure causing collapse (P < .001). Tongue-related obstruction (n = 13) was associated with a small amount of NED (median, 19; interquartile range [IQR], 14%-25%). Moderate NED was found among subjects with isolated palatal collapse (median, 45; IQR, 39%-52%; n = 8) and lateral wall collapse (median, 50; IQR, 44%-64%; n = 8). The epiglottis was associated with severe NED (median, 89; IQR, 78%-91%) and abrupt discontinuities in inspiratory flow (n = 9).

CONCLUSIONS

Inspiratory flow shape is influenced by the pharyngeal structure causing collapse. Flow shape analysis may be used as a noninvasive tool to help determine the pharyngeal structure causing collapse.

High nasal resistance is stable over time but poorly perceived in people with tetraplegia and obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is highly prevalent in people with tetraplegia. Nasal congestion, a risk factor for OSA, is common in people with tetraplegia. The purpose of this study was to quantify objective and perceived nasal resistance and its stability over four separate days in people with tetraplegia and OSA (n=8) compared to able-bodied controls (n=6). Awake nasal resistance was quantified using gold standard choanal pressure recordings (days 1 and 4) and anterior rhinomanometry (all visits). Nasal resistance (choanal pressure) was higher in people with tetraplegia versus controls (5.3[6.5] vs. 2.1[2.4] cmH₂O/L/s, p=0.02) yet perceived nasal congestion (modified Borg score) was similar (0.5[1.8] vs. 0.5[2.0], p=0.8). Nasal resistance was stable over time in both groups (CV=0.23±0.09 vs. 0.16±0.08, p=0.2). These findings are consistent with autonomic dysfunction in tetraplegia and adaptation of perception to high nasal resistance. Nasal resistance may be an important therapeutic target for OSA in this population but self-assessment cannot reliably identify those most at risk.

Upper Airway Collapsibility (Pcrit) and Pharyngeal Dilator Muscle Activity are Sleep Stage Dependent

STUDY OBJECTIVES

An anatomically narrow/highly collapsible upper airway is the main cause of obstructive sleep apnea (OSA). Upper airway muscle activity contributes to airway patency and, like apnea severity, can be sleep stage dependent. Conversely, existing data derived from a small number of participants suggest that upper airway collapsibility, measured by the passive pharyngeal critical closing pressure (Pcrit) technique, is not sleep stage dependent. This study aimed to determine the effect of sleep stage on Pcrit and upper airway muscle activity in a larger cohort than previously tested.

METHODS

Pcrit and/or muscle data were obtained from 72 adults aged 20-64 y with and without OSA.Pcrit was determined via transient reductions in continuous positive airway pressure (CPAP) during N2, slow wave sleep (SWS) and rapid eye movement (REM) sleep. Genioglossus and tensor palatini muscle activities were measured: (1) awake with and without CPAP, (2) during stable sleep on CPAP, and (3) in response to the CPAP reductions used to quantify Pcrit.

RESULTS

Pcrit was 4.9 ± 1.4 cmH2O higher (more collapsible) during REM versus SWS (P = 0.012), 2.3 ± 0.6 cmH2O higher during REM versus N2 (P < 0.001), and 1.6 ± 0.7 cmH2O higher in N2 versus SWS (P = 0.048). Muscle activity decreased from wakefulness to sleep and from SWS to N2 to REM sleep for genioglossus but not for tensor palatini. Pharyngeal muscle activity increased by ∼50% by breath 5 following CPAP reductions.

CONCLUSIONS

Upper airway collapsibility measured via the Pcrit technique and genioglossus muscle activity vary with sleep stage. These findings should be taken into account when performing and interpreting "passive" Pcrit measurements.