Time-course of stepwise CPAP titration. Behavior of respiratory and neurological variables.

Montserrat, Josep M.; Ballester, Eugeni; Olivi, H; Reolid, Alejandra; Lloberes, Patrícia; Morelló, A; Rodríguez-Roisín, Robert

doi:10.1164/ajrccm.152.6.8520746

Cited by 116 publications

(61 citation statements)

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“…Although a recent study found that during nCPAP titration arousals stopped before oesophageal high swings [30], we do not know what happens when the initial sleep deprivation is less acute. After having completed their slow wave rebound, patients may become more arousable and, due to its excessively low pressure level, nCPAP may convert obstructive sleep apnoea to airway resistance syndrome.…”

Section: Discussionmentioning

confidence: 79%

Evaluation of an auto-nCPAP device based on snoring detection

Lofaso¹,

Lorino²,

Duizabo³

et al. 1996

Eur Respir J

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E Ev va al lu ua at ti io on n o of f a an n a au ut to o--n nC CP PA AP P d de ev vi ic ce e b ba as se ed d o onWe observed that a single night of auto-nCPAP improved the apnoea/hypnoea index (AHI) (12±21 vs 51±31 disordered breathing events·h -1 of sleep (mean±SD)), the awakening-arousal index (13±20 vs 40±26 arousals·h -1 of sleep), and duration of slow wave sleep (102±49 vs 71±56 min) but not of rapid eye movement (REM) sleep (55±31 vs 64±38 min). Auto-nCPAP was effective (apnoea/hypopnoea and arousal indices <10 events·h -1 ) in all but three patients. Auto-nCPAP was ineffective in one patient, whose obstructive respiratory events were not preceded by nasal mask pressure vibration detection, and in two patients who were quasi-permanent mouth breathers.Snoring detection may be effective in sleep apnoea syndrome with heavy snoring and without permanent mouth breathing, during the first night of nasal continuous positive airway pressure treatment.

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Section: Discussionmentioning

confidence: 79%

Evaluation of an auto-nCPAP device based on snoring detection

Lofaso¹,

Lorino²,

Duizabo³

et al. 1996

Eur Respir J

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“…2) by the fact that the nonlinear relationship V'th-V' depends on the frequency and on the waveform of the breathing flow. This may particularly affect the detection of obstructive hypopnoeas, since in this case the inspiratory flow tends to change from a quasisinusoidal (normal breathing) to an almost square-wave pattern [11], which, according to figure 4, tends to further underestimate hypopnoeas. As illustrated in the example in figure 2 (left and right), change from a sinusoidal pattern to a square-wave flow of 50% amplitude results in a change of only 5% in thermistor signal.…”

Section: Discussionmentioning

confidence: 99%

“…The thermistor/thermocouple was exposed to realistic flow amplitudes ranging from values typical of normal breathing (±0.8 L·s -1 ) to those of severe hypopnoeas (±0.05 L·s -1 ) and for frequencies (10,15 and 20 bpm) within the range of observed respiratory frequencies. Moreover, we tested two different airflow waveforms (sinusoidal and square-wave) to assess the response of the thermistor when subjected to changes of breathing pattern such as those found in patients from normal breathing to the typically flow-limited airflow during obstructive hypopnoeas [11].…”

Section: Discussionmentioning

confidence: 99%

Accuracy of thermistors and thermocouples as flow-measuring devices for detecting hypopnoeas

Farré¹,

Montserrat²,

Rotger³

et al. 1998

Eur Respir J

130

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aaBreathing airflow is a physiological variable commonly monitored for assessing respiratory patterns and nocturnal events in studies aimed at diagnosing sleep disorders [1][2][3]. Given that in sleep studies the use of a pneumotachograph, which is the reference transducer for measuring flow, is rather cumbersome, airflow is routinely assessed by means of thermally sensitive devices such as thermistors and thermocouples. The main advantage of these devices is that they are small and light and, consequently, their use causes a minimum amount of disturbance to the patient during sleep. However, thermistors and thermocouples are semiquantitative devices since the flow signal they provide is not a direct measure of actual flow [4][5][6]. This drawback, which does not pose major problems for detecting apnoeas, is however relevant to scoring hypopnoeas [7,8], given that the definition of these events is made in terms of quantitative reduction in airflow.Precise characterization of the performance of thermistor/thermocouples when used for measuring airflow in sleep studies requires a laboratory study under controlled conditions. Indeed, contrary to what happens when testing linear transducers, the analysis of a slow-response nonlinear system such as a thermistor/thermocouple [6] requires subjecting it to a variety of input airflows covering the ranges of amplitudes, frequencies and waveforms found in the particular application. Such a systematic study cannot be carried out in patients during sleep since it is not possible to modify the pattern of the breathing airflow in a selective and controlled way. Moreover, pneumo-tachographs, which may modify the thermal conditions in the thermistor/thermocouple, or thoracoabdominal bands, which may not be adequate during padoxical breathing, are not perfect reference flow transducers in this application. The aim of this study was to characterize the accuracy of thermistor/thermocouples as flow-measuring devices for detecting hypopnoeas. To this end, we set up a respiratory model to reproduce the measuring conditions of nasal airflow by means of thermally sensitive devices. Materials and methodsThe response of thermistors and thermocouples was studied with the respiratory system model shown in figure 1. The model was based on a 60 L methacrylate chamber which was used as a buffer of heated air at 37°C. The air temperature in the chamber was measured with a mercury-bulb thermometer and was maintained (±0.2°C) by means of a 120 W heating resistance supplied with the required voltage. Homogeneous distribution of air temperature in the chamber was achieved by means of mixing airflow generated by an internal fan. A flow generator based on a servocontrolled linear motor attached to rubber bellows [9,10] We concluded that thermistor/thermocouples are inaccurate flow-measuring devices when used at the airflow conditions typical of sleep studies. Their use for quantifying hypopnoeas may lead to considerable underdetection of these respiratory events.

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“…the lowest pressure that achieves a therapeutic result during an entire night), or "CPAP titration", has traditionally been conducted by a technician in the sleep laboratory during full polysomnography [2,3]. Although this procedure was initially exclusively directed towards eliminating only frank apnoeas and hypopnoeas, it is now common for the sleep technician to titrate CPAP first to the abolition of apnoeas and hypopnoeas, then to the elimination of snoring, intermittent oxygen desaturations and microarousals on electroencephalogram (EEG) [3,4]. Until recently, CPAP titration was always carried out in the sleep laboratory, but this is a costly and labour-intensive procedure.…”

Section: P Lévy J-l Pepinmentioning

confidence: 99%