Portable Recording Device Research Articles

Screening for Sleep Disordered Breathing in Three Distinct Neurological Diseases in the Bulgarian Population

Sleep disordered breathing (SDB) is a common medical problem in the general population. Neurological disorders such as ischemic stroke (IS), myasthenia gravis (MG), or multiple sclerosis (MS) seem to be of higher risk of SDB. Nevertheless, the implementation of screening for SDB in such disorders has not been well studied. Therefore, the aim of this study was to explore screening parameters for SDB in IS, MG and MS, in our region. We included prospectively patients with diagnosed IS, MG and MS. Psychometric tools such as the Epworth Sleepiness Scale (ESS), the STOP-BANG, and the Berlin questionnaire were implemented. For the respiratory screening portable recording device was used. Seventy-two patients, 25 with IS (mean age 66.3 years), 24 with MG (mean age 47.9 years), and 23 with MS (mean age 40.1 years) were enrolled. Basic anthropometric parameters such as BMI, neck and waist circumference were higher in IS than in MG and MS ($$p<0.001$$). The ESS scores were 5.5±3.2 for IS, 5.6±3.3 for MG, and 5.9±4.5 for MS, but without significant difference between the groups. Contrariwise, STOP-BANG scores in IS were 4.8±1.3, significantly higher ($$p<0.0001$$) than both MG (2.1±1.4) and MS (1.2±0.9). A high risk for OSA in BQ was calculated in 68% of IS, much higher ($$p<0.0001$$) than in MG (33.3%) and in MS (13%). In the respiratory screening, the mean apnea-hypopnea index in the IS group (20±18.3) was statistically higher than in MG (8.1±12.7, $$p<0.005$$), and in MS patients (2.3±4.9, $$p<0.001$$). Oxygen desaturation index in IS (19.3±19) differed statistically from the one in MG (8.1±12.9, $$p<0.005$$), and in MS (2.6±5.5, $$p<0.001$$). The oxygen saturation (SO2) showed difference only between IS and MS in all three measured values – baseline SO2 ($$p<0.001$$), median SO2 ($$p<0.05$$) and lowest SO2 ($$p<0.05$$). IS, MG and MS, as distinct neurological entities, show different clinical profiles with respect to screening for SDB. These should be taken into consideration in the individual evaluation for sleep disordered breathing.

Robust Cough Detection With Out-of-Distribution Detection

Cough is an important defense mechanism of the respiratory system and is also a symptom of lung diseases, such as asthma. Acoustic cough detection collected by portable recording devices is a convenient way to track potential condition worsening for patients who have asthma. However, the data used in building current cough detection models are often clean, containing a limited set of sound categories, and thus perform poorly when they are exposed to a variety of real-world sounds which could be picked up by portable recording devices. The sounds that are not learned by the model are referred to as Out-of-Distribution (OOD) data. In this work, we propose two robust cough detection methods combined with an OOD detection module, that removes OOD data without sacrificing the cough detection performance of the original system. These methods include adding a learning confidence parameter and maximizing entropy loss. Our experiments show that 1) the OOD system can produce dependable In-Distribution (ID) and OOD results at a sampling rate above 750 Hz; 2) the OOD sample detection tends to perform better for larger audio window sizes; 3) the model's overall accuracy and precision get better as the proportion of OOD samples increase in the acoustic signals; 4) a higher percentage of OOD data is needed to realize performance gains at lower sampling rates. The incorporation of OOD detection techniques improves cough detection performance by a significant margin and provides a valuable solution to real-world acoustic cough detection problems.

A 1D CNN for high accuracy classification and transfer learning in motor imagery EEG-based brain-computer interface

Objective. Brain-computer interface (BCI) aims to establish communication paths between the brain processes and external devices. Different methods have been used to extract human intentions from electroencephalography (EEG) recordings. Those based on motor imagery (MI) seem to have a great potential for future applications. These approaches rely on the extraction of EEG distinctive patterns during imagined movements. Techniques able to extract patterns from raw signals represent an important target for BCI as they do not need labor-intensive data pre-processing. Approach. We propose a new approach based on a 10-layer one-dimensional convolution neural network (1D-CNN) to classify five brain states (four MI classes plus a ‘baseline’ class) using a data augmentation algorithm and a limited number of EEG channels. In addition, we present a transfer learning method used to extract critical features from the EEG group dataset and then to customize the model to the single individual by training its late layers with only 12-min individual-related data. Main results. The model tested with the ‘EEG Motor Movement/Imagery Dataset’ outperforms the current state-of-the-art models by achieving a accuracy at the group level. In addition, the transfer learning approach we present achieves an average accuracy of . Significance. The proposed methods could foster the development of future BCI applications relying on few-channel portable recording devices and individual-based training.

Heart sounds: a pilot randomised trial to determine the feasibility and acceptability of audio recordings to improve discharge communication for cardiology inpatients protocol

IntroductionIneffective hospital discharge communication can significantly impact patient understanding, safety and treatment adherence. This may be especially true for cardiology inpatients who leave the hospital with complex discharge plans delivered...

New Evaluation of the Electronically Activated Recorder (EAR): Obtrusiveness, Compliance, and Participant Self-selection Effects.

The Electronically Activated Recorder (EAR) is a method for collecting periodic brief audio snippets of participants’ daily lives using a portable recording device. The EAR can potentially intrude into people’s privacy, alter their natural behavior, and introduce self-selection biases greater than in other types of social science methods. Previous research (Mehl and Holleran, 2007, hereafter M&H) has shown that participant non-compliance with, and perceived obtrusiveness of, an EAR protocol are both low. However, these questions have not been addressed in jurisdictions that require the consent of all parties to recording conversations. This EAR study required participants to wear a button bearing a microphone icon and the words “This conversation may be recorded” to comply with California’s all-party consent law. Results revealed self-reported obtrusiveness and non-compliance were actually lower in the present study than in the M&H study. Behaviorally assessed non-compliance did not differ between the two studies. Participants in the present study talked more about being in the study than participants in the M&H study, but such talk still comprised <2% of sampled conversations. Another potential problem with the EAR, participant self-selection bias, was addressed by comparing the EAR volunteers’ HEXACO personality dimensions to a non-volunteer sample drawn from the same student population. EAR volunteers were significantly and moderately higher in Conscientiousness, and lower in Emotionality, than non-volunteers. In conclusion, the EAR method can be successfully implemented in at least one all-party consent state (California). Interested researchers are encouraged to review this procedure with their own legal counsel.

Detection of Double Compressed AMR Audio Using Stacked Autoencoder

The adaptive multi-rate (AMR) audio codec adopted by many portable recording devices is widely used in speech compression. The use of AMR speech recordings as evidence in court is growing. Nowadays, it is easy to tamper with digital speech recordings, which makes audio forensics increasingly important. The detection of double compressed audio is one of the key issues in audio forensics. In this paper, we propose a framework for detecting double compressed AMR audio based on the stacked autoencoder (SAE) network and the universal background model—Gaussian mixture model (UBM-GMM). Instead of hand-crafted features, we used the SAE to learn the optimal features automatically from the audio waveforms. Audio frames are used as network input and the last hidden layer’s output constitutes the features of a single frame. For an audio clip with many frames, the features of all the frames are aggregated and classified by UBM-GMM. Experimental results show that our method is effective in distinguishing single/double compressed AMR audio and outperforms the existing methods by achieving a detection accuracy of 98% on the TIMIT database. Exhaustive experiments demonstrate the effectiveness and robustness of the proposed method.

Circadian changes and sex-related differences in fetal heart rate parameters.

BackgroundPrevious researchers have studied circadian changes in the fetal heart rate (FHR) on small sample sizes and in a strictly controlled environment. This study was undertaken to investigate these changes during the late second and third trimesters, using a portable fetal electrocardiogram recording device (Monica AN24) in pregnant women in home and hospital environments with unrestricted mobility.MethodsThis was a prospective cohort study of 54 pregnant women with uncomplicated singleton pregnancies between 25 and 40 weeks gestation. FHR recordings were made up to 16 h at home or in the hospital setting in the United Kingdom. FHR data over 90 min periods were averaged and the day (7:00 am–11:00 pm) and night (11:00 pm–7:00 am) data from the same individual were compared. Data were examined for evidence of sex-related differences.ResultsDuring the night, there was a significant reduction in basal heart rate (bFHR) and a significant increase in short term variation (STV) and long term variation (LTV) (P < 0.05). Basal FHR decreased (P < 0.002), whereas LTV increased (P = 0.014) with advancing gestation. Male fetuses showed greater day: night variation than females regardless of gestation (P = 0.014). There was a higher bFHR in fetuses monitored during the day in hospital (P = 0.04).ConclusionThis study demonstrates that there are sex-, environment and time-related differences in the FHR parameters measured. These differences may need to be considered taken when interpreting FHR data.

Feasibility of Galaxy Smartphone Recording as Portable Recorder for Acoustic Analysis of Voice

Background and Objectives Acoustic analysis of voice could be influenced so much by the quality of voice files which were recorded by recording device. In clinical practice, voice files that were recorded by analysis program directly or portable digital recording device were analyzed mostly. This study examined the feasibility of using Galaxy smartphone recordings for acoustic analysis of voice. Materials and Methods Acoustic measures were compared between voice signals recorded from 30 normal speakers (15 males and 15 females) through Galaxy smartphone, portable digital recording device and CSL. Fo, jitter, shimmer, NHR (Noise-Harmony ratio) and Formant frequencies were analyzed by MDVP. Results Fo, Jitter, Shimmer, NHR and formant frequencies from 3 devices were no significantly difference. The intraclass correlation coefficient (ICC) was higher between each of the voice perturbation measures. Conclusion The findings indicated that Galaxy smartphone recording system was useful device for acoustic analysis of voice. Furthermore, Galaxy smartphone can be applied widely in various way for acoustic analysis of voice. Key words: Galaxy smartphone ㆍ Recording devices ㆍ Acoustic analysis 핵심용어: 갤럭시 스마트폰 ㆍ ë ¹ìŒìž¥ë¹„ ㆍ 음향분석

A study of Foley Sound based on analysis and compare of the bird’s chirping

This research verifies use value of Foley sound of bird‘s chirping used in Radio drama as sound contents by comparing and analyzing it with Actual sound. Radio drama utilizes sound of bird‘s chirping to show season, time, and place in various ways. Currently, this sound is used as sound effect in media by recording Actual sound of bird‘s chirping on site with portable recorder. Before when no portable recording device existed, they had to make Foley sound. To have comparative analysis of Actual and Foley sound of bird‘s chirping, production method of Foley sound tools and their usage were studied. To conclude, as Foley sound tools used for sound of bird‘s chirping are very unique and interesting there is a high possibility of developing them into Sound contents for Performance and Exhibition.

Diagnosis of obstructive sleep apnea with respiratory polygraph in hypercapnic ICU patients

The most frequent reasons for hypercapnic respiratory failure (HRF) in ICUs are COPD and in recent years obesity hypoventilation syndrome (OHS) and obstructive sleep apnea (OSA). Even 15 to 30% of COPD patients also have accompanying OSA. Due to increased upper airway resistance, those patients require higher expiratory pressures (EPAP) during noninvasive ventilation (NIV). In order to prescribe optimal mode and pressures during the ICU stay and at discharge, the intensivist should diagnose the underlying OSA. Portable recording devices have been developed and they were approved at least for the diagnosis in high pretest probability patients with results equal to in-laboratory polysomnography. The aim of this study is to assess whether respiratory polygraph (RPLG) can be used for obtaining diagnostic information of OSA in hypercapnic ICU patients.

The effect of intermittent use of occlusal splint devices on sleep bruxism: a 4-week observation with a portable electromyographic recording device.

This randomised controlled study investigated the effect of intermittent use of occlusal splints on sleep bruxism compared with that of continuous use by measuring masseter muscle electromyographic activity using a portable electromyographic recording system. Twenty bruxers were randomly allocated to the continuous group and intermittent group. Subjects in the continuous group wore stabilisation splints during sleep for 29 nights continuously, whereas those in the intermittent group wore splints during sleep every other week, that is they used splints on the 1st-7th, 15th-21st and 29th nights. Electromyographic activity of the masseter muscle during sleep was recorded for the following six time points: before (baseline), immediately after, and 1, 2, 3 and 4weeks after the insertion of a stabilisation splint. The number of nocturnal masseter electromyographic events, duration and the total activity of sleep bruxism were analysed. In the continuous group, nocturnal masseter electromyographic events were significantly reduced immediately and 1week after the insertion of the stabilisation splint, and duration was reduced immediately after the insertion (P<0·05, Dunnett's test), but no reduction was observed at 2, 3 and 4weeks after insertion. In the intermittent group, nocturnal masseter electromyographic events and duration were significantly reduced immediately after and also 4weeks after insertion of the stabilisation splint (P<0·05, Dunnett's test). The obtained results of the present exploratory trial indicate that the intermittent use of stabilisation splints may reduce sleep bruxism activity for a longer period compared with that of continuous use.

Multi-channel audio recording based on superdirective beamforming for portable multimedia recording devices

In this paper, an audio recording method using a near-coincident microphone array is proposed for a multichannel audio system. A coincident or near-coincident microphone recording method attempts to capture spatial images in a multi-channel audio system depending on directional-level differences or directivities. Thus, high directivity is required for good spatial quality in the multichannel audio system, and it is usually obtained using a directional microphone. However, the currently available microphones such as cardioid, hyper-cardioid, and figure-8 directional microphones have lower directivities. To overcome this problem, the proposed method forms a superdirective sound beam in each steered direction using closely spaced omni-microphones. It is shown from subjective listening tests that the proposed method provides higher spatial quality with lower timbral distortions than other conventional recording methods for stereo and 5.1-channel audio systems.

The value of home video with ambulatory EEG: A prospective service review

PurposeThe demand for long term EEG monitoring is increasing with the emphasis on recording patients’ attacks. Outpatient ambulatory EEG is relatively inexpensive and widely available. The main disadvantage of the technique is the lack of video which can make interpretation of an ictus difficult. We investigated whether patients, if offered home video equipment, would take it, if this resulted in simultaneous EEG-video capture of an ictus and if interpretation of the recording was facilitated by the video. MethodAll ambulatory EEG patients, adults and children, were offered a camcorder to take home during a 17-month study period. Results130 patients/carers were offered a camcorder (93 adults, 37 children), 45 patients (35%) accepted; the main reason for not accepting was that attacks were considered too brief to record. An ictal event occurred in 34 patients (76%) with a camcorder; in 17 (50%) of these an attack was captured successfully on video. The main reasons for failure to capture events were that attacks were too brief, or that the camcorder was not operated successfully. Attacks were captured with greater success in children (14/23, 61%) than adults (3/11, 27%). Of the 17 video recordings, 14 (82%) were helpful in aiding interpretation of the ambulatory EEG. ConclusionIn our study, home video facilities aided interpretation of ambulatory EEG recordings in approximately one third of patients. Technological advances and familiarity with portable recording devices will improve this figure and patients and their carers should be encouraged to use such facilities when available.

Ambulatory monitoring in the diagnosis and management of obstructive sleep apnoea syndrome

Obstructive sleep apnoea (OSA) is a highly prevalent disorder associated with complications such as arterial hypertension, cardiovascular diseases and traffic accidents. The resources allocated for OSA are insufficient and OSA is a significant public health problem. Portable recording devices have been developed for the detection of OSA syndrome and have proved capable of providing an equivalent diagnosis to in-laboratory polysomnography (PSG), at least in patients with a high pre-test probability of OSA syndrome. PSG becomes important in patients who have symptoms and certain comorbidities such as chronic obstructive pulmonary disease or stroke, as well as in patients with a clinical history suggesting a different sleep disorder. Continuous positive airway pressure is the most effective treatment in OSA. Ambulatory monitoring of the therapeutic modalities has been evaluated to enhance the care process and reduce costs compared to the conventional approach, without sacrificing efficiency. This review evaluates the role of portable monitoring devices in the diagnostic process of OSA and the search for alternative strategies based on ambulatory management protocols.

Evaluation of a biochemical process to minimize snoring with ambroxol & bromhexine in comparison with their performance in non OSA Bangladeshi patients

Snoring is an important sign of sleep-related breathing disorders (SRBD), of the upper airway resistance syndrome (UARS), and of the obstructive sleep apnea (OSA). Snoring is a symptom of nasal obstruction and is associated with cardiovascular diseases. Roommates or bed partners are also suffered by snorers. In-house monitoring of snoring is very useful for evaluation by bed partner or roommate as well as polysomnography in sleeping centre. Process to evaluate and monitoring snoring available in the country are mechanical process. Our objective is to evaluate a biochemical process to minimize snoring with two mucolytic expectorants Ambroxol & Bromhexine and compare their performance in non OSA Bangladeshi patients.32 snorers with no other respiratory disease like asthma , bronchitis etc. and who has ESS score 8-16 and SSS score 2-4,were taken from a Sleep Medicine Centre of Japan Bangladesh Friendship Hospital, 15 students from Bangabandhu Sheikh Mujibur Rahman Hall, Jahangirnagar University and another 15 from University of Development Alternative(UODA). The procedure and scoring were performed by help of roommates and bed partners. Snoring was measured on the basis of Frequency, Loudness, Snoring Index and day time sleepiness using Epworth Sleepiness Scale (ESS). A portable respiratory recording device (PRRD )was used to determine loudness, index and frequency of patient at home and snoring data was also collected from sleep medicine centre where polysomnogram was used. snoring severity objectively were also measured by using Snoring Severity Scale (SSS). excellent snoring suppressing effect was observed in both groups after treating separately with Ambroxol and Bromhexine 30 mg per night. Snoring Frequency, Loudness, Severity, Index and ESS score was reduced markedly in compared to placebo group.

The Utility of a Portable Recording Device for Screening of Obstructive Sleep Apnea in Obese Adolescents

The ApneaLink Plus is a portable recording device that measures air flow, respiratory effort, heart rate, and pulse oximetry. In the current study, we asked whether this device could be used to screen for obstructive sleep apnea in the pediatric population. Sleep-laboratory polysomnography (PSG) was performed simultaneously with measurements using the portable device on obese pediatric patients referred for snoring. The obstructive apnea hypopnea index (OAHI) was calculated automatically by the device (autoscore) and manually by the investigators. Sensitivity, specificity, correlation, and receiver operating curves (ROC) were used to compare the portable device to PSG. Twenty-five subjects (60% male, mean age 13.6 ± 3.0 years, OAHI on PSG 11.8 ± 27.1) were studied. We identified a significant correlation between the OAHI of the ApneaLink autoscore and PSG (Spearman Rho = 0.886 [p < 0.001]). Using the PSG results as standard, ROC curves comparing the ApneaLink OAHI with the PSG OAHI demonstrated high congruence. The autoscore agreement was very good at PSG OAHI > 1.5 (area under the receiver operating curve [AUC] 0.965, OAHI > 5 [AUC 0.937], and OAHI > 10 [AUC 1.00]). The agreement of the manual score and autoscore were essentially equivalent. The device's autoscore demonstrated high sensitivity at all cutoffs examined (100% at OAHI > 1.5, 85.7% at OAHI > 5, and 100% at OAHI > 10). The specificity increased with increasing cutoffs (46.2% at OAHI > 1.5, 83.3% at OAHI > 5, and 90.0% at OAHI > 10). he ApneaLink Plus is a sensitive screening tool for evaluation of suspected OSAS in obese pediatric patients aged 9-18 years. The specificity improves with increasing OAHI cutoffs. The device detects OSAS when tested in a sleep laboratory on obese adolescents referred for symptoms of sleep related breathing disorder.

Pseudoresistant Hypertension Attributed to White-Coat Effect

See related article, pp 564–571 An increase in blood pressure (BP) when taken in the office setting was recognized as early as 1940, when Ayman and Goldshine1 reported that BP readings measured in the clinic were higher than BP recorded in the home. The authors attributed the increase in clinic BP to “the excitement and tension associated with the visit to the clinic or doctor's office.” In 1966, Sokolow et al2 using a noninvasive portable BP recording device showed that readings taken during usual daily activities (ambulatory BP) were lower than casual office BP. Floras et al3 subsequently confirmed these findings with continuous intra-arterial BP recordings by observing higher BP in the clinic compared with the awake ambulatory BP. Advances in ambulatory BP monitoring led to several studies by Pickering and his colleagues4,5 in which home BP and ambulatory BP were noted to be similar and BP lower during sleep and higher in the office setting. Based on these observations, they proposed the term “white-coat hypertension” (WCH) to describe the phenomenon of higher office BP and lower awake ambulatory BP.6 Pickering et al7 then proceeded to report on a series of 292 patients with untreated, borderline hypertension, finding that 21% exhibited WCH defined as a high office diastolic BP of 90 to 104 …

Acceptability of and compliance to CPAP therapy in patients with obstructive sleep apnea syndrome

Summary. The study was aimed at determination of acceptability of and compliance to CPAP among Armenians with obstructive sleep apnea syndrome (OSAS). A portable recording device was used to diagnose OSAS. Snoring, nasal flow, oxygen saturation and pulse rate were recorded. Thirty nine patients with moderate to severe OSAS (AHI ≥ 15) were offered CPAP therapy, of them, 20 patients agreed to undergo a pressure titration and night trial with CPAP. A card embedded in the CPAP device electronically recorded compliance. After night trial, 14 males (35.6 %) were administered long-term CPAP therapy. Significant difference between “acceptors“ and “refusers“ was found in AHI (74.5 ± 22.6 vs 41.7 ± 28.4; p < 0.001), oxygen desaturation index (70.3 ± 22.6 vs 37.6 ± 24.5; p < 0.001) and Epworth Sleepiness Scale (20.7 ± 4.2 vs 14.7 ± 7.5; p < 0.01). The mean compliance to CPAP therapy was 83 %. The study revealed low acceptability of and high compliance to CPAP therapy among Armenians with OSAS.

Validation of a portable recording device (ApneaLink) for identifying patients with suspected obstructive sleep apnoea syndrome

Polysomnography (PSG) is currently the standard diagnostic procedure for sleep apnoea. This study evaluates the diagnostic accuracy of a portable recording device, ApneaLink (AL; ResMed, Poway, CA, USA) for detection of sleep apnoea in comparisons against PSG. The AL device is a three-channel screening tool that measures airflow through a nasal pressure transducer, oximetry and pulse, providing an apnoea-hypopnoea index (AHI) based on recording time. Nocturnal PSG (Alice 4; Healthdyne, Atlanta, GA, USA), with airflow measured by a nasal pressure transducer (ProTech PTAF2; ProTech, Woodinville, WA, USA) and AL recordings were carried out simultaneously in consecutive patients with suspected obstructive sleep apnoea syndrome (OSAS). The PSG recordings were analysed manually by a blinded investigator. The oxygen desaturation index of AL was also compared against the AHI based on PSG. Fifty consecutive subjects with symptoms of OSAS were recruited with mean age of 50 years and body mass index of 27.9 kg/m2. The AHI obtained by the AL device correlated closely to that obtained by PSG (Pearson correlation, r= 0.978, P < 0.001), whereas the correlation between PSG AHI and oxygen desaturation index by AL was also strong (r= 0.895, P < 0.001). Comparison of AHI based on the AL against the PSG demonstrated high sensitivity and specificity at AHI > or =10/h (sensitivity 0.977 and specificity 1.0) and at AHI > or =20/h (sensitivity 0.969 and specificity 1.0). The AL portable monitoring device is highly sensitive and specific in quantifying the apnoea-hypopnoea index when compared against hospital based polysomnography in patients with suspected OSAS. The simple device may be useful for screening and diagnostic purpose when access to PSG is limited.

Polygraphy of Sleep at Altitudes Between 5300 m and 7500 m During an Expedition to Mt. Everest (MedEx 2006)

Sleep at extreme altitudes is characterized by the repetitive occurrence of central apneas that in some cases may lead to a marked decrease in arterial oxygen saturation. During the Ludwig Maximilians University Expedition to Mt. Everest (MedEx 2006), nocturnal polygraphic recordings were made at different altitudes and included the first recordings ever made at 7500 m, which were completed on 8 separate occasions during the expedition. The study was performed on the author (K.M., 58 years, 181 cm, 75 kg), who is an experienced high-altitude mountaineer. The standard polygraphic parameters, such as nasal and oral airflow, thoracic and abdominal effort, oxygen saturation, heart rate, body position, movement, and snoring, were collected with a portable sleep recording device (AlphaScreen, SensorMedics, Germany, Hochberg) at different altitudes between 5300 m and 7500 m, and were compared with baseline assessments made in Munich, Germany (altitude 508 m). The daytime value of oxygen saturation at rest was measured at South Col (8000 m) and at the South Summit (8763 m) without breathing supplemental oxygen for at least 10 minutes. The number of apneas and hypopneas of central origin increased up to a maximum of 148/h with a minimal blood oxygen saturation of 48% at 7500 m, compared with <5/h at Munich. After 11 days of acclimatization, data recorded at 5300 m showed a marked reduction of disturbed sleep. The Apnea-Hypopnea-Index dropped from 138/h to 51/h, and the minimal blood oxygen saturation rose from 57% to 67%. At South Col (8000 m), the daytime value of oxygen saturation at rest ranged between 53% and 55%, and on South Summit (8673 m) without breathing supplemental oxygen for at least 10 minutes, it fluctuated around 50%. These data correlate well compared with those obtained in hypobaric chamber studies and show that regardless of physiologic adjustment to low oxygen conditions at Base Camp altitude, during the final summit attempt oxygen saturation drops further to 55% and even less. Thus recordings of nocturnal oxygen saturation at Camp 3 (7500 m) on Everest, where the night is spent before the summit attempt, may help to show the actual efficiency of hypoxic ventilatory response and to detect the individual hypoxic tolerance to altitudes above 8000 m.