Patient compliance and satisfaction with a new forehead device for positional obstructive sleep apnoea treatment: a post hoc analysis of a randomised controlled trial.

BACKGROUND: The influence of body position in obstructive sleep apnoea patients is well known. A positional therapy device placed at the forehead has proven to be effective in reducing the severity of positional obstructive sleep apnoea (POSA) symptoms. The aim of the study was to evaluate patients' therapy compliance and satisfaction in the short term and mid-term. METHODS: A post hoc analysis of a randomised controlled trial was conducted using an inactive device (ID) or an active device (AD) for 3 months. The primary outcomes were device usage and the percentage of patients with good compliance (defined as device use for more than 4 hours per night and more than 70% of nights per week). Secondary outcomes included time spent with head in the supine position, patient satisfaction and side effects. RESULTS: The median duration of using the device was 6.9 hours in the ID group and 6.7 hours in the AD group (p=0.309), and the durations were similar throughout the follow-up period and from the first day of use. The percentage of patients with good compliance was similar and greater than 60% in both groups. The median time spent with head in the supine position was significantly lower in the AD group (2.9%) than in the ID group (12.4%) since the first day of treatment. Both groups showed satisfaction scores values above 8.5 (out of 10) in all items, while side effects were scarcely reported. CONCLUSION: High device compliance was achieved in POSA patients, both in terms of device usage time and percentage of days used. Patients were highly satisfied, and the device effectively reduced the time spent with the head in the supine position from the first day of use.

Evaluation of upper airway patency during Cheyne-Stokes breathing in heart failure patients.

Little is known about the changes in upper airway calibre in Cheyne-Stokes respiration (CSR) during sleep in patients with congestive heart failure. This study aimed to test the hypothesis that upper airway closure occurs during central CSR events, by assessing upper airway calibre during sleep using the forced oscillation technique (FOT). Nine males with compensated heart failure (left ventricular ejection fraction mean ± sem 27.9 ± 5.1%) and predominant central CSR (apnoea/hypopnoea index 43.9 ± 4.2 events · h(-1)) were studied during overnight polysomnography, which included pneumotachography, inductance plethysmography or oesophageal pressure and FOT-derived impedance signal (|Z|). Baseline |Z| values during stable breathing in stage 2 sleep were 11.0 ± 1.3 cmH(2)O · s · L(-1). Mean |Z| increased to 31.9 ± 6.7 cmH(2)O · s · L(-1) during obstructive apnoeas (7% of events, n = 46). Increases in |Z| consistent with upper airway narrowing (more than two-fold baseline) were common during central apnoeas (50 ± 12% of events) occurring in the middle or end of apnoeas and occurred during some central hypopnoeas (16 ± 10% of events), typically in the expiratory phase. These findings indicate that in heart failure patients, reductions in upper airway calibre are common during CSR apnoeas, and may also occur during central hypopnoeas.

Surface respiratory electromyography and dyspnea in acute heart failure patients.

INTRODUCTION AND OBJECTIVES: Dyspnea is the most common symptom among hospitalized patients with heart failure (HF) but besides dyspnea questionnaires (which reflect the subjective patient sensation and are not fully validated in HF) there are no measurable physiological variables providing objective assessment of dyspnea in a setting of acute HF patients. Studies performed in respiratory patients suggest that the measurement of electromyographic (EMG) activity of the respiratory muscles with surface electrodes correlates well with dyspnea. Our aim was to test the hypothesis that respiratory muscles EMG activity is a potential marker of dyspnea severity in acute HF patients. METHODS: Prospective and descriptive pilot study carried out in 25 adult patients admitted for acute HF. Measurements were carried out with a cardio-respiratory portable polygraph including EMG surface electrodes for measuring the activity of main (diaphragm) and accessory (scalene and pectoralis minor) respiratory muscles. Dyspnea sensation was assessed by means of the Likert 5 questionnaire. Data were recorded during 3 min of spontaneous breathing and after breathing at maximum effort for several cycles for normalizing data. An index to quantify the activity of each respiratory muscle was computed. This assessment was carried out within the first 24 h of admission, and at day 2 and 5. RESULTS: Dyspnea score decreased along the three measured days. Diaphragm and scalene EMG index showed a positive and significant direct relationship with dyspnea score (p<0.001 and p = 0.003 respectively) whereas pectoralis minor muscle did not. CONCLUSION: In our pilot study, diaphragm and scalene EMG activity was associated with increasing severity of dyspnea. Surface respiratory EMG could be a useful objective tool to improve assessment of dyspnea in acute HF patients.

Bench model to simulate upper airway obstruction for analyzing automatic continuous positive airway pressure devices.

BACKGROUND: Automatic positive airway pressure (APAP) devices are increasingly being used in patients with obstructive sleep apnea. Some APAP devices present an unstable behavior when subjected to some events or artifacts. The aims were to develop a bench model capable of reproducing real flow, snoring, and obstructive patterns and to compare the response of APAP devices based on flow and snoring with other devices using, in addition, the forced oscillation technique (FOT). METHODS: The bench model subjected APAP devices to apneas with and without obstruction, obstructive hypopneas with and without snoring, periods of flow limitation, and artifacts such as leaks and mouth expiration. RESULTS: Almost all the devices increased the pressure when subjected to apneas with obstruction, but at different rates. The time required by each device to reach 10 cm H(2)O ranged from 2.5 to 13 min. In the presence of apneas without obstruction, all the devices based on flow and snoring increased the pressure at the same rate as during apneas with obstruction. However, the devices using FOT did not modify the pressure. Four devices did not modify the pressure in the presence of obstructive hypopneas, and all but one device increased the pressure in the presence of snoring. Mask leaks had little effect on the response of the devices, but four devices increased the pressure during mouth expiration artifacts. CONCLUSIONS: When, in addition to the flow and snoring signals, the measurement of the upper airway resistance is included, the accuracy of the event detection algorithms is improved.

Effect of using the flow or the volume signals on the measurement of nonapneic respiratory events.

STUDY OBJECTIVES: To assess whether the measurement of breathing reduction during obstructive sleep events depends on using the flow or the volume signals recorded with a pneumotachograph. DESIGN: Prospective observational study. SETTING: Sleep laboratory in a University Hospital. PATIENTS OR PARTICIPANTS: Data from 10 male patients with sleep apnea (54 +/- 11 years, apnea-hypopnea index: 43 +/- 21 events/hour, body mass index: 30 +/- 2 kg/m2). INTERVENTIONS: Slow modification of continuous positive airway pressure was performed during full-polysomnography continuous positive airway pressure titration. MEASUREMENTS AND RESULTS: Air flow was measured by a pneumotachograph, and volume was computed by numerical integration. Obstructive events of different magnitude were selected. In 500 breathing cycles analyzed, the reduction in tidal volume was greater than the reduction in the flow amplitude: mean difference of 0.091 (i.e., 9.1% amplitude) and limits of agreement of 0.095 and -0.277 (i.e., 9.5% and -27.7% amplitude). In 14% of the cycles, the reduction in flow was < 50%, whereas the reduction in volume was > 50%, resulting in discordant event classification. CONCLUSIONS: The quantification of breathing reduction depends on whether the flow or the volume signal is used to assess breathing during sleep.

Oscillometric assessment of airway obstruction in a mechanical model of vocal cord dysfunction.

Vocal cord dysfunction (VCD) is characterized by inappropriate adduction of the vocal cords, particularly during inspiration, resulting in obstruction and airflow limitation. Direct visualization of the vocal cords with laryngoscopy is the 'gold standard' for diagnosing VCD. However, it is an invasive technique that may induce airway irritation. The aim of this study was to determine whether the forced oscillation technique (FOT) is useful to estimate the degree of closure of a non-linear orifice under conditions mimicking those found in VCD. The FOT (5 Hz, +/-1 cm H(2)O) was applied to an airway model simultaneously with constant levels of flow in the normal breathing range (0-0.8l/s). Pressure-flow (P(0)-V'(0)) curves, quasi-static resistance (R(eff)) and oscillatory resistance (R(FOT)) were measured in orifices with different areas (0.15-1.12 cm2) and shapes and in an orifice with variable area. Their pressure-flow relationship followed a quadratic model. Changes in R(FOT) normalized by flow (DeltaR(FOT)/V'(0)) were related to changes in the area of the vocal cord model (1/A(VC2)(2)-1/A(VC1)(2)) from maximum aperture (A(VC1)) to different degrees of closure (A(VC2)): DeltaR(FOT)/V'(0)=1.93(1/A(VC2)(2)-1/A(VC1)(2))+2.08 cm H(2)Os(2)/l(2); r(2)=0.99. We conclude that FOT could be a useful tool for non-invasively assessing glottic closure in VCD diagnosis, obviating the need for other invasive techniques.

Spirometric standards and patient characteristics: an exploratory study of factors affecting fulfillment in routine clinical practice.

BACKGROUND: Spirometry is an apparently simple test, yet the recommended criteria for acceptability and reproducibility can be difficult to fulfill. This study aimed (1) to prospectively assess the number of tests that meet the American Thoracic Society/European Respiratory Society (ATS/ERS) 2005 acceptability and repeatability criteria in the routine practice of an experienced technician at a referral hospital's lung function laboratory, (2) to identify the most common errors, and (3) to explore patient characteristics possibly associated with failure to meet standards. METHODS: We prospectively evaluated 257 consecutive spirometries supervised by the same technician, who gave priority to achieving a minimum of 3 correct maneuvers within a maximum of 8 attempts. We recorded FVC, FEV1, expiratory time (TE), back-extrapolated volume (VE), end-of-test volume (VEOT), number of maneuvers with and without errors, and errors (VE > 0.15 L or 5% of FVC, TE < 6 s, and VEOT ≥ 0.025 L for ≥ 1 s). RESULTS: Two-hundred and fifteen spirometries (83.7%, 95% CI 78.6-87.7%) met the ATS/ERS 2005 criteria. Acceptability criteria were met in 73.9% (95% CI 71.2-76.3%) of the maneuvers and repeatability criteria in 90.7% (95% CI 86.5-93.6%). A mean ± SD of 3.3 ± 1.4 per subject was acceptable, and a mean ± SD of 4.5 ± 1.9 was obtained. TE and VEOT errors were the most common. CONCLUSIONS: Nearly 15% of the subjects failed to fulfill all the ATS/ERS 2005 criteria for spirometry performed even though they were coached by a qualified and regularly trained technician in a hospital lung function laboratory. The fact that the ATS/ERS 2005 criteria cannot be met by all patients in optimal technical conditions should be further considered and explored.

Static and dynamic upper airway obstruction in sleep apnea: role of the breathing gas properties.

Increased upper airway collapsibility in the sleep apnea/hypopnea syndrome (SAHS) is usually interpreted by a collapsible resistor model characterized by a critical pressure (Pcrit) and an upstream resistance (Rup). To investigate the role played by the upstream segment of the upper airway, we tested the hypothesis that breathing different gases would modify Rup but not Pcrit. The study was performed on 10 patients with severe SAHS (apnea-hypopnea index: 59 +/- 14 events/hour) when breathing air and helium-oxygen (He-O2) during non-REM sleep. The continuous positive airway pressure that normalized flow (CPAPopt) was measured. Rup and Pcrit were determined from the linear relationship between maximal inspiratory flow VImax and nasal pressure (PN):VImax = (PN - Pcrit)/Rup. Changing the breathing gas selectively modified the severity of dynamic (CPAPopt, Rup) and static (Pcrit) obstructions. CPAPopt was significantly (p = 0.0013) lower when breathing He-O2 (8.44 +/- 1.66 cm H2O; mean +/- SD) than air (10.18 +/- 2.34 cm H2O). Rup was markedly lower (p = 0.0001) when breathing He-O2 (9.21 +/- 3.93 cm H2O x s/L) than air (15.92 +/- 6.27 cm H2O x s/L). Pcrit was similar (p = 0.039) when breathing He-O2 (4.89 +/- 2.37 cm H2O) and air (4.19 +/- 2.93 cm H2O). The data demonstrate the role played by the upstream segment of the upper airway and suggest that different mechanisms determine static (Pcrit) and dynamic (Rup) upper airway obstructions in SAHS.

Response of automatic continuous positive airway pressure devices to different sleep breathing patterns: a bench study.

Evaluating the usefulness of automatic continuous positive airway pressure (CPAP) in treating the sleep apnea-hypopnea syndrome (SAHS) is not easy because the algorithms for automatic CPAP implemented in the devices available are not well known and are probably dependent on the device. In addition, at present it is not possible to test the behavior of automatic CPAP devices in response to well-defined breathing patterns. Our aim was to implement a bench test to characterize the responses of automatic CPAP devices by subjecting them to breathing patterns of patients with SAHS. To this end, a variety of typical breathing patterns (normal, apneas, hypopneas, flow limitation, snoring) previously recorded in patients with SAHS during sleep were reproduced by a breathing waveform generator. Five commercially available automatic CPAP devices were tested. The responses of the devices to apneas, hypopneas, flow limitation, and snoring were considerably different. In some devices, the response was modified by air leaks similar to the ones found in patients. Consequently, the effectiveness of automatic CPAP assessed in clinical tests performed by using particular devices has no general validity. Testing automatic CPAP devices in a bench study is a useful first step in evaluating the performance of this new type of device in adjusting nasal pressure for each patient.