Detection Of Respiratory Events Research Articles

Pulse Transit Time Improves Detection of Sleep Respiratory Events and Microarousals in Children

To evaluate the additional information provided by pulse transit time (PTT), a noninvasive tool, when using during polysomnography for the diagnosis of sleep breathing disorders in a pediatric population. Respiratory and microarousals events were scored twice. The first scoring was performed using nasal pressure, thermistors, thoracic and abdominal movements, and oxygen saturation. The second scoring, blinded to the first scoring, was performed using PTT in combination with all the other signals. Microarousals were scored once visually on the EEG trace (cortical arousals [CAs]) and once using the PTT signal (autonomic arousals [AAs]) blinded to EEG. For the whole group of 16 children studied (mean age, 9.5 years), there was no significant difference between the respiratory disturbance index (RDI) with or without PTT analysis (22.4 +/- 13.5/h vs 20.4 +/- 14.3/h; not significant [mean +/- SD]). Among the children exhibiting a "without PTT" RDI < 30/h, 5 of 12 children (41.66%) showed a clinically significant >/= 5/h increase in RDI when using PTT. AAs detected by PTT were significantly more frequent than CAs during rapid eye movement (REM) sleep (7.4 +/- 3.9/h vs 3.2 +/- 2.3/h; p < 0.001) and slow wave sleep (SWS) [6.0 +/- 4.3/h vs 0.6 +/- 0.5/h; p < 0.0001]. The quantification of respiratory effort using PTT improves the detection of respiratory events in children. The detection of microarousals is improved particularly in REM and SWS.

Does perioperative pulse oximetry improve outcome? Seeking the best available evidence to answer the clinical question

The aim of this chapter is to clarify the effect of perioperative monitoring with pulse oximetry and to identify the adverse outcomes that might be prevented or improved by its use. Trials were identified by computerized searches of The Cochrane Library, MEDLINE and EMBASE, and by checking the reference lists of trials and review articles. All controlled trials that randomized patients to either pulse oximetry or no pulse oximetry during the perioperative period, including the operating and recovery room, were included in the search. Pulse oximetry monitoring was shown to substantially reduce the extent of perioperative hypoxaemia, enabling the detection and treatment of hypoxaemia and related respiratory events, and promoting several changes in patient care. The implementation of perioperative pulse oximetry monitoring does not significantly reduce the number of postoperative complications, but the question remains whether pulse oximetry can improve outcomes in other situations. Pulse oximetry has been adopted all over the world in clinical practice as a tool that guides anaesthesiologists in the daily management of patients: in teaching situations, in emergencies, and especially in the care of children. Given the relatively small number of patients studied in these trials and the rare events being sought, the studies of perioperative monitoring with pulse oximetry were not able to show an improvement in the outcomes studied.

Evaluation of Unattended Automated Titration To Determine Therapeutic Continuous Positive Airway Pressure in Patients With Obstructive Sleep Apnea

Determination of the therapeutic pressure during continuous positive airway pressure (CPAP) therapy is usually performed by a technician during polysomnography. In recent years, several devices for automated adjustment of the therapeutic pressure by the means of computerized algorithms were developed. The aims of the present study were to compare two different devices for automated titration and to verify if unattended automated titration is a feasible strategy to determine the therapeutic CPAP. We enrolled 16 consecutive patients with obstructive sleep apnea syndrome (OSAS) defined by an apnea-hypopnea index > 20/h. Automated titration was performed in the hospital using two CPAP devices (Autoset; Resmed; North Ryde, Australia; and Somnosmart; Weinmann; Hamburg, Germany) in random order for 2 consecutive nights, based on different signals for the detection of respiratory events. During titration, there was no direct supervision by a technician, and polysomnography was not recorded. We defined the therapeutic pressure as the 95th percentile of the airway pressure over time (P95). We observed significant differences of the P95 between the two devices, with an average of 7.0 +/- 2.5 cm H(2)O for the Somnosmart and 9.9 +/- 2.6 cm H(2)O for the Autoset (p = 0.005) [mean +/- SD]. There was a considerable lack of agreement between the two devices, with a bias of 3.0 cm H(2)O and limits of agreement ranging from + 9.3 to - 3.2 cm H(2)O. We found no significant correlation between the paired differences of P95 and either indexes of severity of OSAS or lung function variables. Automated titration based on the analyses of flow (Autoset) or forced oscillations (Somnosmart) predicted significant different therapeutic pressures for fixed CPAP therapy. Thus, unattended automated titration performed during 1 night of hospital stay with commercially available devices cannot be used to determine accurately the therapeutic CPAP in patients with OSAS.

Detection of Sleep Apnea with the Forced Oscillation Technique Compared to Three Standard Polysomnographic Signals

Background: The forced oscillation technique (FOT) allows analysis of the upper airway impedance and, hence, detection of obstructive sleep apnea. Objective: To evaluate FOT with respect to sensitivity and to specificity in online detection of sleep-disordered breathing patterns and to compare algorithmic onset detection time with manual onset time markers of staff physicians. Methods: We compared the absolute value ∣Z∣ of the impedance with three routinely obtained polysomnographic signals – nasal airflow v̇_nasal, thoracic excursion Thox and esophageal pressure P_es – by retrospective analysis of the diagnostic polysomnograms of 51 patients. For each signal we evaluated algorithms for online detection of respiratory events. For each out of five apnea classes, 50 respiratory events marked by staff physicians were drawn randomly from the 51 polysomnograms to optimize the online detection algorithms (learning set). The algorithm analyzes relative changes of signal baseline and amplitude. Again 50 respiratory events were drawn randomly for each apnea class to examine to what extent it is possible to detect event onsets with the algorithms (test set). Results: The sensitivity of the signals varied between 56 and 94% and was on average 74%. The specificity was 96 ± 1.5% on average. The onset was detected 4–6 s after the initially evaluated onset of the staff physicians. Conclusion: We conclude that nasal airflow and FOT are equivalent sensitive measurands for detection of respiratory events.

Respiratory arousals in mild obstructive sleep apnea syndrome.

The objective of the study is to identify patients with mild sleep apnea by counting not only apneas and hypopneas, but also mild respiratory events, which do not fulfill apnea or hypopnea criteria, but result in an arousal (Type-R arousal). Arousals related to body movements (Type-M arousal) were separately counted. The influence of nasal continuous positive airway pressure (nCPAP) on respiratory and movement arousals was analyzed. Daytime sleepiness before and after nCPAP and its relationship to arousal types was investigated using the Multiple Sleep Latency Test (MSLT) and a standardised questionnaire. Twenty-two patients with a mean age of 43.6 +/- 9.2 years underwent polysomnographic evaluation on a baseline night, and during three nights with nCPAP. On the baseline night, subjects presented with a mean RDI of 10.5 +/- 7.2/h, an apnea index (AI) of 1.2 +/- 1.5/h, a hypopnea index (HI) of 9.3 +/- 6.6/h, a R index of 5.2 +/- 5.9/h, and a M index of 9.7 +/- 5.6/h. Use of nCPAP lowered the RDI (p < 0.001) and the R index (p < 0.01). Mean sleep latency in the MSLT increased with nCPAP (p < 0.05) and the patient's subjective well being improved (p < 0.01). Correlation analysis revealed a relationship between Type-R arousals and RDI and HI (r = 0.5, p < 0.01) as well as between questionnaire scores and mean sleep latency. The decrease of Type-R indicates the positive effect of nCPAP. Arousal analysis and detection of mild respiratory events associated with arousals are helpful in investigating the sleep structure and in objectifying clinical symptoms and treatment success in patients with mild OSAS.

Early detection of upper airway obstructions by analysis of acoustical respiratory input impedance.

Repetitive occurrence of partial or total upper airway obstruction characterizes several respiratory dysfunctions such as the obstructive sleep apnea syndrome (OSAS). In OSAS patients, pharyngeal collapses are linked to a decrease in upper airway muscle activity during sleep which causes decreased upper airway wall stiffness. Continuous positive airway pressure (CPAP) is recommended as the treatment of choice. Advancements in CPAP therapy require early detection of respiratory events in real time to adapt the level of the applied pressure to airway collapsibility. The forced oscillation technique (FOT) is a noninvasive method which reflects patients' airway patency by measuring respiratory impedance. The aim of this study was to evaluate by a mathematical model of the respiratory system if FOT can provide an early detection index of total or partial upper airway obstruction. Furthermore, the simulation should suggest which characteristic features are relevant for early apnea detection in measured clinical data. The respiratory system has been treated as a series of cylindrical segments. The oropharynx analog of the model allows simulation of upper airway collapse, mimicking the situation in patients with OSAS. We calculated the input impedance for different degrees of upper airway obstruction ranging from unobstructed airways to total occlusion. Furthermore, we simulated different upper airway wall compliances. We compared the simulation with real data. The results of the study suggest that FOT is a valuable tool for assessing the degree of upper airway obstruction in patients with OSAS. Especially, the phase angle of the impedance seems to be a potentially useful tool for early apnea detection by assessing the upper airway wall collapsibility.

Detection of Respiratory Events During NPSG: Nasal Cannula/Pressure Sensor Versus Thermistor

Recording of respiratory airflow is an integral part of polysomnography (NPSG). It is conventionally monitored with a thermistor that measures temperature as a surrogate of flow. The subjectivity of interpreting hypopnea from this signal has prompted us to measure nasal airflow directly with a simple pneumotachograph consisting of a standard nasal cannula connected to a 2-cm H2O pressure transducer. We manually analyzed respiratory events using simultaneous thermistor and nasal cannula in 11 patients with obstructive sleep apnea syndrome (OSAS) and 9 with upper airway resistance syndrome (UARS). Definite events were scored separately for each signal when amplitude was <50% for >10 seconds. Events were also scored on the nasal cannula signal when the flattened shape of the signal suggested flow limitation, and these were tabulated separately. Definite events in one signal were tabulated by whether the other signal showed a definite event or not. In addition, nasal cannula events were compared to a more liberal thermistor criterion (any change in the signal for > or = 2 breaths). Visually, events were more easily recognized on the nasal cannula signal than on the thermistor signal. In OSAS, 1,873 definite thermistor events were detected. Of these, 99.1% were detected by nasal cannula, and 0.9% were missed. Of 3,541 definite nasal cannula events, 51.9% were detected by definite thermistor criteria; 75.0% were detected by liberal thermistor criteria; 25.0% were missed. In UARS, 123 definite thermistor events were detected. Of these, 89.4% were detected by nasal cannula and 10.6% were missed. Nine hundred and three nasal cannula events were detected. However, only 17.2% of these were detected by definite thermistor criteria; 38.6% were detected by liberal thermistor criteria; 61.4% were completely undetected by thermistor. When events identified on the nasal cannula by flow limitation alone were excluded, the thermistor detected 30.1% of events by definite criteria and 78.6% by liberal criteria, still leaving 21.4% completely undetected by the thermistor. We conclude that the nasal cannula reliably detects respiratory events seen by thermistor. Additional events (including some characterized only by flow limitation) that help define the UARS, were recognized by nasal cannula but often completely missed by thermistor. We propose that respiratory monitoring during NPSG with nasal cannula significantly improves event detection and classification over that with thermistor.

Computerized detection of respiratory events during sleep from rapid increases in oxyhemoglobin saturation

A computerized search for rapid resaturation (RES)--defined as increases in oxyhemoglobin saturation (SaO2) of 3% or more within 10 s--was used to detect apneas and hypopneas during sleep by the episodes of compensatory hyperventilation following them. Results were compared to those from computerized search for desaturations (DESAT)--defined as decreases in SaO2 of 4% or more within 40 s--and to simultaneous polysomnography. We studied 30 patients with obstructive sleep apnea (OSA) with an apnea plus hypopnea index (AHI) of 30.8 +/- 6.9 (median +/- SEM) and 23 habitual snorers (HSN) with an AHI of 7 +/- 1.5. Manual scoring of polysomnography revealed 7965 respiratory events (6192 apneas, 1773 hypopneas) in OSA patients and 940 events (411 apneas, 529 hypopneas) in the HSN group. In OSA patients, the computer found 96% of events by searching for RES and 87% by searching for DESAT. The percentage of computer-found events in OSA classified as true positive was 91% for RES and 97% for DESAT. In the HSN group, 83% of polysomnographically scored events were found by RES and 55% by DESAT, with 72% of RES and 84% of DESAT being true positive. The correlation of the number of computer-found RES with the number of events from polysomnography was better in OSA (r = 0.862, p less than 0.0001) than in HSN (r = 0.722, p less than 0.001). The same was true for DESAT (OSA: r = 0.896, p less than 0.0001; HSN: r = 0.637, p less than 0.01). In conclusion, computer-found rapid resaturations are more sensitive than desaturations for the detection of respiratory events during sleep from oximetry.(ABSTRACT TRUNCATED AT 250 WORDS)

Value of monitoring of tracheal respiratory sounds in the diagnosis of nocturnal respiratory dysrhythmias

Twenty-six patients underwent a polysomnigraphic study allowing sleep staging and respiratory events scoring with the use of the oronasal flow, abdominal, thoracic and total displacement (Respitracet), and ear oximetry. Moreover the patients were also equipped with a tracheal microphone giving a power rectified envelope (sonospirogram). Eleven patients showed abnormal respiratory events that were scored by visual lecture using all respiratory parameters (excluding the sonospirogram) and were classified as obstructive central and mixed apneas-hypopneas. Periodic breathing was also appreciated. Detection of the same events was tried with the sonospirogram alone. The sonospirogram could accurately detect snoring and periodic breathing and finally central obstructive mixed apnea (the apneic index being well correlated: p less than 0.001 as well as the mean apnea duration: p less than 0.005). In contrast hypopneic events related to snoring could not be accurately appreciated. We conclude that a sonospirogram may be useful for the detection of abnormal respiratory events when used alone (screening) as when added to other respiratory signals.