P028 The Nox A1 ambulatory system is reliable when self-applied

Background Home Sleep Apnea Tests (HSAT) increases access to SDB diagnostic testing (Safadi, 2014). A previous study defined a reliable HSAT if: ≥4hours total recording time, an intelligible position signal and respiratory effort, airflow and oximetry for at least 80% of the night were recorded, however, admits no standardized criteria in the literature (Domingo, 2010). Aim To test the reliability of a self-applied HSAT using the Nox-A1 ambulatory system (NOX Medical, Iceland). Method Patients self-applied the HSAT guided by industry produced video and written instructions. Signals for the HSAT included; two electro-occulagrams (EOG), two sub-mental electromyograms (EMG), a single modified frontal encephalogram (EEG), a lead I ECG, single leg anterior tibialis EMG, chest and abdominal inductance respiratory effort, nasal pressure airflow, WristOx 2 3150 SpO2 (Nonin Medical, Inc., USA) and 3-D accelerometer and body position sensor. Analysed with ProFusion PSG 4 (Compumedics Limited, Australia) after importing data into Nexus. 33 consecutive studies were recorded during lock-down. Recording satisfactory if SpO2 signal and EEG present >80% of study, it was considered a failure if doctor requested test repeat. Results 33 subjects, age 43.1 ± 13.7 years, BMI 27.4 ± 6.0 kg/m2, 66.6% male. 81.8% of studies satisfactory. 6% of studies needed a repeat in-lab PSG due to 1) loss of oximetry & EEG and 2) loss of EEG Discussion 6% doctor request repeat in-lab PSG is comparable to a study (Lloberes, 2001) of partially self-applied HSAT. Demonstrated good reliability with this self-applied COVID-safe method of HSAT.

P088 Presence versus absence of flow limitation during stable breathing in patients with obstructive sleep apnoea

Introduction Flow limitation is the distinguishing characteristic of obstructive sleep apnoea. Critically, periods of flow limitation can occur without overt reductions in airflow (e.g. disproportionate increase in ventilatory drive vs. achieved ventilation), however, such periods are ignored by clinical scoring. Here we investigate flow limitation during so-called “stable breathing”, i.e. periods of sleep without scored events, by applying our recently-validated model to estimate flow limitation from the airflow signal. Methods Flow limitation was visually-scored (N=117,871 breaths) from N=40 participants attending an overnight sleep study for suspected sleep apnoea. Scoring was aided by physiological signals (e.g. intra-oesophageal diaphragm EMG). Model flow limitation classification used features extracted from the pneumotach signal (cross-validated accuracy=92.4%). We applied this method to investigate the occurrence of flow limitation during stable breathing, defined as periods of sleep >3 min duration without scored arousals or respiratory events. Results Model predicted flow limitation frequency was strongly correlated with visual scoring (R²=0.84 p<0.001). The median flow limitation frequency during stable breathing ranged from 8–91%, with an overall median of 59% (IQR 37%-75%). Flow limitation frequency during stable breathing was only modestly associated with the apnoea-hypopnea index (R²=0.12 p<0.05). Discussion Flow limitation occurs surprisingly frequently during stable breathing. While some individuals achieve stable breathing with minimal flow limitation, others demonstrate substantial flow limitation. Heterogeneity in frequency of flow limitation (within and between individuals) may provide further insights into emergent phenotypic variability within sleep disordered breathing. Finally, this model performed similarly in nasal pressure (88.2% accuracy), indicating potential application to clinical studies.

O015 Upper airway collapsibility measurement under anaesthesia in children: feasibility and utility in predicting perioperative respiratory adverse events

Background Perioperative respiratory adverse events (PRAE) pose significant risk in paediatric anaesthesia, and identifying risk is vital. Perioperative measurement of pharyngeal closing pressure (PCLOSE) is a quick, objective method of assessing upper airway collapsibility that may identify PRAE risk. Aim To investigate if PCLOSE measurement is feasible and predictive of PRAE in children. Method Fifty-six children (1-8years, 34 male, without significant co-morbidities) underwent PCLOSE measurements immediately preceding (pre-PCLOSE) and following (post-PCLOSE) adenotonsillectomy. Measurement was performed under anaesthesia while breathing spontaneously in supine posture with head/jaw neutral. After application of a face mask, inspiratory flow was occluded with an associated decrease in mask/nasal pressure seen with each inspiratory effort. With airway collapse, a plateau developed in minimum pressure observed (= PCLOSE): less collapsible airways occluded at more negative pressures. PCLOSE was averaged over 5–6 sequential efforts, at least 3 times on each occasion. Results Both pre-and post-PCLOSE were successfully measured in 94.6% children without affecting procedure. Pre-PCLOSE and change in PCLOSE from pre- to post- were associated with an increased incidence of PRAE (Poisson regression coefficient 0.083(0.03) (mean, SE); p=0.0054 and 0.03(0.01); p=0.018, respectively). There was no significant association between post-PCLOSE and PRAE. The odd of PRAE occurrence during recovery was 1.5 times higher than in other phases. Conclusion This study demonstrated the feasibility of obtaining PCLOSE. A more collapsible airway before surgery and an increase in collapsibility with surgery were both associated with increased PRAE. PCLOSE measurement could be a valuable risk assessment tool for PRAE in children undergoing surgery.

Telemedicine Strategy to Rescue CPAP Therapy in Sleep Apnea Patients with Low Treatment Adherence: A Pilot Study

Patients with sleep apnea are usually treated with continuous positive airway pressure (CPAP). This therapy is very effective if the patient′s adherence is satisfactory. However, although CPAP adherence is usually acceptable during the first months of therapy, it progressively decreases, with a considerable number of patients accepting average treatment duration below the effectiveness threshold (4 h/night). Herein, our aim was to describe and evaluate a novel telemedicine strategy for rescuing CPAP treatment in patients with low adherence after several months/years of treatment. This two-week intervention includes (1) patient support using a smartphone application, phone and voice recorder messages to be answered by a nurse, and (2) daily transmission and analysis of signals from the CPAP device and potential variation of nasal pressure if required. On average, at the end of the intervention, median CPAP adherence considerably increased by 2.17 h/night (from 3.07 to 5.24 h/night). Interestingly, the procedure was able to markedly rescue CPAP adherence: the number of patients with poor adherence (<4 h/night) was considerably reduced from 38 to 7. After one month, adherence improvement was maintained (median 5.09 h/night), and only 13 patients had poor adherence (<4 h/night). This telemedicine intervention (103€ per included patient) is a cost-effective tool for substantially increasing the number of patients with CPAP adherence above the minimum threshold for achieving positive therapeutic effects.

Inhibitory Effect of Nasal Intermittent Positive Pressure Ventilation on Gastroesophageal Reflux

Non-invasive intermittent positive pressure ventilation can lead to esophageal insufflations and in turn to gastric distension. The fact that the latter induces transient relaxation of the lower esophageal sphincter implies that it may increase gastroesophageal refluxes. We previously reported that nasal Pressure Support Ventilation (nPSV), contrary to nasal Neurally-Adjusted Ventilatory Assist (nNAVA), triggers active inspiratory laryngeal closure. This suggests that esophageal insufflations are more frequent in nPSV than in nNAVA. The objectives of the present study were to test the hypotheses that: i) gastroesophageal refluxes are increased during nPSV compared to both control condition and nNAVA; ii) esophageal insufflations occur more frequently during nPSV than nNAVA. Polysomnographic recordings and esophageal multichannel intraluminal impedance pHmetry were performed in nine chronically instrumented newborn lambs to study gastroesophageal refluxes, esophageal insufflations, states of alertness, laryngeal closure and respiration. Recordings were repeated without sedation in control condition, nPSV (15/4 cmH2O) and nNAVA (~ 15/4 cmH2O). The number of gastroesophageal refluxes recorded over six hours, expressed as median (interquartile range), decreased during both nPSV (1 (0, 3)) and nNAVA [1 (0, 3)] compared to control condition (5 (3, 10)), (p < 0.05). Meanwhile, the esophageal insufflation index did not differ between nPSV (40 (11, 61) h-1) and nNAVA (10 (9, 56) h-1) (p = 0.8). In conclusion, nPSV and nNAVA similarly inhibit gastroesophageal refluxes in healthy newborn lambs at pressures that do not lead to gastric distension. In addition, the occurrence of esophageal insufflations is not significantly different between nPSV and nNAVA. The strong inhibitory effect of nIPPV on gastroesophageal refluxes appears identical to that reported with nasal continuous positive airway pressure.

Inhibitory Effect of Nasal Intermittent Positive Pressure Ventilation on Gastroesophageal Reflux

Non-invasive intermittent positive pressure ventilation can lead to esophageal insufflations and in turn to gastric distension. The fact that the latter induces transient relaxation of the lower esophageal sphincter implies that it may increase gastroesophageal refluxes. We previously reported that nasal Pressure Support Ventilation (nPSV), contrary to nasal Neurally-Adjusted Ventilatory Assist (nNAVA), triggers active inspiratory laryngeal closure. This suggests that esophageal insufflations are more frequent in nPSV than in nNAVA. The objectives of the present study were to test the hypotheses that: i) gastroesophageal refluxes are increased during nPSV compared to both control condition and nNAVA; ii) esophageal insufflations occur more frequently during nPSV than nNAVA. Polysomnographic recordings and esophageal multichannel intraluminal impedance pHmetry were performed in nine chronically instrumented newborn lambs to study gastroesophageal refluxes, esophageal insufflations, states of alertness, laryngeal closure and respiration. Recordings were repeated without sedation in control condition, nPSV (15/4 cmH2O) and nNAVA (~ 15/4 cmH2O). The number of gastroesophageal refluxes recorded over six hours, expressed as median (interquartile range), decreased during both nPSV (1 (0, 3)) and nNAVA [1 (0, 3)] compared to control condition (5 (3, 10)), (p < 0.05). Meanwhile, the esophageal insufflation index did not differ between nPSV (40 (11, 61) h-1) and nNAVA (10 (9, 56) h-1) (p = 0.8). In conclusion, nPSV and nNAVA similarly inhibit gastroesophageal refluxes in healthy newborn lambs at pressures that do not lead to gastric distension. In addition, the occurrence of esophageal insufflations is not significantly different between nPSV and nNAVA. The strong inhibitory effect of nIPPV on gastroesophageal refluxes appears identical to that reported with nasal continuous positive airway pressure.

Alternative Procedure to Individual Nasal Pressure Titration for Sleep Apnea

In the treatment of obstructive sleep apnea (OSA), the current standard of “CPAP titration” in the laboratory or at home is a resource demanding and costly approach that, in developed economies, markedly augments healthcare costs and in low resource economies precludes access to care altogether. Here, we discuss that current guidelines for titration of CPAP could be obviated by taking a different route that in many ways is similar to the institution of treatment in many other medical conditions. To this effect, we present novel population based data from 16,780 patients, showing that after individualized and labor-intensive and expensive CPAP titration, 86.4% of OSA patients are treated with nasal pressure settings within the range of 9 ± 2 cmH2O, and review the literature to justify the potential adoption of a standard therapeutic CPAP setting as the initial intervention which would be subsequently followed by any necessary adjustments in only a minority of patients who would not derive the necessary benefit from such standardized intervention. Assuming an 80–85% success rate as derived from our analyses, our personal view if extensively adopted could radically reduce healthcare costs and enable markedly improve access to diagnostics.

Computational Fluid Dynamics Analysis of Nasal Airway Changes after Treatment with C-Expander

The use of the C-expander is an effective treatment modality for maxillary skeletal deficiencies which can cause ailments and significantly reduce life expectancy in late adolescents and young adults. However, the morphological and dynamic effects on the nasal airway have not been reported. The main goal of this study was to evaluate the nasal airway changes after the implementation of a C-expander. A sample of nine patients (8 females, 1 male, age range from 15 to 29 years) was included. The morphology parameters and nasal airway ventilation parameters of pretreatment and posttreatment were measured. All study data were normally distributed. A paired t -test was used to evaluate the changes before and after treatment. After expansion, the mean and standard deviation values of intercanine maxillary width (CMW) and intermolar maxillary width (MMW) increased from 35.75 ± 2.48 mm and 54.20 ± 3.17 mm to 37.87 ± 2.26 mm ( P < 0.05 ) and 56.65 ± 3.10 mm ( P < 0.05 ), respectively. The nasal cavity volume increased from 20320.00 ± 3468.25 mm3 to 23134.70 ± 3918.84 mm3 ( P < 0.05 ). The nasal pressure drop decreased from 36.34 ± 3.99 Pa to 30.70 ± 3.17 Pa ( P < 0.05 ), while the value of the maximum velocity decreased from 6.50 ± 0.31 m/s to 5.85 ± 0.37 m/s ( P < 0.05 ). Nasal resistance dropped remarkably from 0.16 ± 0.14 Pa/ml/s to 0.08 ± 0.06 Pa/ml/s ( P < 0.05 ). The use of C-expander can effectively broaden the area and volume of the nasal airway, having a positive effect in the reduction of nasal resistance and improvement of nasal airway ventilation. For patients suffering from maxillary width deficiency and respiratory disorders, a C-expander may be an alternative method to treat the disease.