K. H. Rühle

Efficiency of cold passover and heated humidification under continuous positive airway pressure

Cold passover and heated humidifiers are employed for the prevention of side-effects associated with continuous positive airway pressure (CPAP) treatment. However, to date, it has not been possible to separately measure the humidity of inspired and expired air. The aim of this study was to compare the relative humidity of the inspired air and the water loss during respiration between cold passover and heated humidifiers under CPAP. Humidity and temperature were determined separately for the respiratory phases, without humidification, with cold passover and heated humidifiers in 10 healthy subjects. Humidity was measured with a capacitive hygrometer, temperature with a “Type K” thermosensor, and impedance of the total respiratory system with impulse oscillometry. The relative humidity (rH) of the inspired air (mean±sd) increased significantly from 24.0±9.1% rH (34.8±1.0°C, no humidifier) to 34.5±10.1% rH (34.6±1.0°C) under cold humidification, and to 53.9±13.2% rH (35.0±1.1°C) under heated humidification. With heated humidification, water loss was reduced by 38% compared to cold humidification. The impedance increased from 5.7±1.8 cmH2O·L·s−1 (no humidifier) to 6.7±1.8 cmH2O·L·s−1 (heated humidifier). The authors conclude that the use of a heated humidifier during continuous positive airway pressure appreciably increases the relative humidity of the inspired air and reduces the water loss during respiration.

Prospective randomized comparison of impedance-controlled auto-continuous positive airway pressure (APAPFOT) with constant CPAP

Background: The measurement of impedance permits reliable detection of obstructive apneas, hypopneas and upper airways resistance syndrome. Objective: To establish whether impedance-controlled self-adjusting positive airway pressure therapy (APAPFOT) is equally as good as constant continuous positive airway pressure (CPAP) in the treatment of sleep apnea syndrome (OSAS). Methods: Twenty men and five women with OSAS (age 52.8±9.0 years, body mass index (BMI) 31.4±5.0 kg/m2, AHI 32.2±18.1/h (mean±SD)) underwent baseline polysomnography, manual CPAP titration and two nights of treatment, one with APAPFOT, one with constant CPAP. Results: With both modes, a significant reduction in respiratory disturbances was seen (apnea/hypopnea index (AHI) baseline 32.2±18.1/h, constant CPAP 6.6±8.7, APAPFOT 5.5±3.8/h, P<0.001 baseline vs. each treatment mode). Under APAPFOT, the sleep profile was normalized (S3/4 baseline 16.3±13.9% total sleep time (TST), APAPFOT 21.6±10.9% TST, P<0.05, rapid eye movement (REM) 14.2±6.7% TST vs. 20.3±7.3% TST, P<0.01), while with constant CPAP, a tendency towards improvement was found. The mean treatment pressure with APAPFOT was significantly lower than the constant CPAP (5.7±2.1 vs. 8.3±1.6 mbar, P<0.001). Conclusion: We conclude that APAPFOT is at least as effective as constant CPAP in normalizing sleep and breathing in OSAS.

Prospective controlled animal study on biopsy sampling with new flexible cryoprobes versus forceps: evaluation of biopsy size, histological quality and bleeding risk.

Background: Cryoextraction is a procedure used for the recanalization of obstructed airways caused by visible exophytic endobronchial tumor. Biopsy samples obtained by this technique have been shown to be useful for histological assessment. Objectives: The aim of the present animal study was to systematically evaluate biopsy size, histological quality and bleeding risk after cryobiopsy with new, flexible cryoprobes in comparison with forceps biopsy, serving as the gold standard. Methods: Biopsies were obtained from anesthetized pigs with the flexible bronchoscopy technique, and evaluated histologically with respect to their size and quality. Bleeding frequency, bleeding duration and histological changes in the biopsy bed were also recorded. Results: Cryobiopsies were significantly larger than forceps biopsies. The size of cryobiopsies was dependent on the freezing time. The histological quality of the cryobiopsy specimenswas not impaired by the freezing process, whereas forceps biopsies showed typical crush artifacts. Despite the larger defects left in the tracheobronchial system after cryobiopsy, bleeding frequency and duration were not higher compared to forceps biopsy. Conclusions: Since cryobiopsy sampling is not associated with a higher bleeding risk compared with forceps biopsy, this new biopsy technique offers – in addition to a good specimen quality – a safe and valuable tool with the potential of improving the outcome of diagnostic endoscopy.

Upper Airway Resistance Syndrome

Obstruction of the upper airway may cause arousals resulting in daytime sleepiness and cardiovascular disturbances. The upper airway resistance syndrome may easily be overlooked because conventional measurements of oronasal airflow and thoracic and abdominal efforts are not sensitive enough. By measuring esophageal pressure even small disturbances can be detected, but the esophageal gauge may disturb sleep. We conclude that other, less invasive methods like measurements of impedance by forced oscillation technique, or flattening of the inspiratory flow contour could be valid alternatives in the diagnosis of the upper airway resistance syndrome. Other methods, such as measurements of the pulse transit time, phase angle, or systolic blood pressure profile are promising, but need further evaluation.

Impact of a controlled heated breathing tube humidifier on sleep quality during CPAP therapy in a cool sleeping environment.

There are conflicting data on the effect of adding a heated humidifier to nasal continuous positive airway pressure (CPAP) therapy for patients with obstructive sleep apnoea syndrome (OSAS). The effects of heated humidification on sleep quality and treatment side-effects for patients who prefer a cold bedroom environment have not been studied. A randomised, controlled crossover trial involving 19 patients with a first-ever diagnosis of OSAS measured the effect of conventional heated humidification added to CPAP compared with a controlled heated breathing tube humidifier (ThermoSmart®; Fisher and Paykel Healthcare, Auckland, New Zealand) on sleep quality. During the night in the sleep laboratory at a mean room temperature of 14°C, less condensation formed with the controlled heated breathing tube humidifier (1.9 mL versus 35.3 mL) in the delivery system. In addition, the total sleep time, time spent in sleep stages 3 and 4, and rapid eye movement sleep phases were significantly longer and the overall side-effect score was lower than with conventional heated humidification. Patients on nasal continuous positive airway pressure desiring a cool bedroom temperature could benefit from controlled heated breathing tube humidification technology (with inputs from ambient temperature, set pressure and flow).

Bronchosparing properties of celiprolol, a new beta 1, alpha 2-blocker, in propranolol-sensitive asthmatic patients.

The bronchopulmonary effects of celiprolol were studied in 12 male asthmatic patients who showed mean maximum changes of -24% in forced one-second expiratory volume (FEV1) and 130% in airways resistance (Raw) following a single, 80 mg dose of propranolol. Celiprolol 200 and 400 mg and placebo were administered in double-blind, random fashion. Raw and FEV1 were determined by whole body plethysmography 1, 2, and 3 h post dose. For placebo and celiprolol 200 and 400 mg, mean maximum changes in FEV1 were 0.6, 2.8, and 2.4%, and for Raw, 11.3, -0.2, and -10.9%, respectively. Pulmonary effects of the three treatments were indistinguishable but differed significantly from propranolol. Five 0.5 mg doses of terbutaline aerosol, administered at 15-min intervals starting 3 h post drug or placebo, caused less bronchodilation after propranolol than after placebo, or celiprolol 200 or 400 mg; the responses after the latter three were indistinguishable. These results suggest that celiprolol is highly bronchosparing and does not block bronchodilation following the beta 2-agonist terbutaline in propranolol-sensitive asthmatics. In contrast to classical beta-adrenoceptor antagonists, celiprolol may afford a greater margin of safety in asthmatic patients with angina or hypertension.

A Test for the Determination of Sustained Attention in Patients with Obstructive Sleep Apnea Syndrome

Background and Objectives: To investigate the parameter daytime sleepiness in patients with the sleep apnea syndrome (SAS), a test for measurement of sustained attention was developed. The present studies were performed on volunteers undergoing preemployment medical examinations and SAS patients to determine the extent to which test results are in agreement with the symptoms of SAS and traffic accident reports, and also with daytime sleepiness, and whether learning or therapeutic effects can be seen with repeated tests prior to and following treatment with nasal continuous positive airway pressure (nCPAP). Methods: Participants: 125 healthy volunteers, and two groups of 28 SAS patients each. Design: Study A: The volunteers underwent a single attention test and completed a questionnaire concerned with traffic accidents and symptoms of sleep-related breathing disorders. Study B: SAS patients underwent two attention tests before treatment. Study C: SAS patients underwent one attention test before and one after nCPAP therapy. Results: Study A: The error rate in volunteers without symptoms of sleep-related breathing disorders (51 persons) was 4.7 ± 4.3% (number of errors 14.1 ± 12.9), 95% CI: 1.2 (number of errors 3.6). No dependence of the error rate on age, BMI or sex was found. In persons with a history of apneic events (n = 10), the error rate was 10.6 ± 10.0% (number of errors 31.8 ± 30), in those with more than two accidents during the last 5 years (n = 4), it was increased to 15.3 ± 9.7% (number of errors 45.9 ± 29.1). Study B: Among SAS patients, no significant learning effect was seen, and prolongation of the test duration beyond 30 min had no effect on the test results. Study C: The error rate improved significantly with nCPAP [10.6 ± 13.5 vs. 6.4 ± 8.9% (number of errors 31.8 ± 40.5 vs. 19.2 ± 26.7), p < 0.001]. Conclusions: The attention test can be helpful for the measurement of daytime sleepiness, and CPAP therapy can improve test performance.

Konsensuspapier zur Diagnostik und Therapie schlafbezogener Atmungsstörungen bei Erwachsenen

Diagnosis and treatment of sleep disordered breathing (SDB) undergo substantial changes, both in terms of increasing scientific knowledge and also in terms of patient provision and socio-economic aspects. Increasing evidence shows the relevance of SDB on morbidity and mortality of affected patients. The precise differentiation of different phenotypes of SDBs has improved substantially in recent years. These proceedings influence the approach to the patients suspected of suffering from SDB. The scientific advances on the one hand are facing intentions to simplify diagnostical processes and treatment initiation and intentions to translate duties of physicians to non-medical personnel on the other hand. This consensus paper presents the principals of diagnosis, treatment initiation and provision, including the role of different participants of the healthcare system, and compares different treatment options. Major aspects include the differentiation of the diagnostical process in screening, affirmation of diagnosis and differential diagnosis. In addition, it focusses on the relevance of the pretest probability and describes a therapeutical algorithm.

Removal of the tracheal tube after prolonged mechanical ventilation: assessment of risk by oscillatory impedance.

Background: Decannulation failure is usually due to tracheal obstruction. Prior to decannulation, inspection by the invasive procedure of bronchoscopy that permits morphological evaluation of a tracheal stenosis is standard practice. A non-invasive method enabling the quantification of the airway obstruction that requires little cooperation is measurement of the airway resistance by the forced oscillation technique. Objectives: The aim of the present study was to define oscillatory impedance thresholds which predict successful decannulation. Methods: A total of 131 patients were investigated prospectively. Step 1: Following probatory decannulation, measurement of the oscillatory impedance. Step 2: Blinded to the results of the impedance measurement, bronchoscopy-assisted decannulation attempt. The criteria for renewed cannulation were high-grade laryngeal or tracheal obstruction, dyspnea or stridor, or a drop in SaO2 <90% under O2 insufflation. Statistics: Determination of the ratio tracheal tube remains/tracheal tube removed (TT+/TT–) for every measured value of the oscillatory resistance at 5 Hz (Ros 5 Hz). Determination of specificity and positive predictive value for determined threshold values with respect to TT–. Results: The data of 126 patients were evaluated. TT+ n = 26, TT– n = 100. Decannulation on the basis of bronchoscopy criteria: Specificity and positive predictive value found out for Ros 5 Hz <0.35 kPa/l/s (n = 44) were 1.00 and 1.00, respectively, and for Ros 5 Hz <0.47 kPa/l/s (n = 71) 0.88 and 0.96, respectively. Conclusions: Measurement of the oscillatory airway resistance represents a practicable method prior to decannulation. Below a value of Ros 5 Hz <0.35 kPa/l/s, bronchoscopy would appear not to be necessary.

Regulationsverhalten von Auto-CPAP-Geräten während der Simulation von schlafbezogenen Atemflussmustern

INTRODUCTION The function of automatic CPAP devices is difficult to investigate using clinical examinations due to the high variability of breathing disorders. With a flow generator, however, identical breathing patterns can be reproduced so that comparative studies on the behaviour of pressure of APAP devices are possible. Because the algorithms of APAP devices based on the experience of users can be modified without much effort, also previously investigated devices should regularly be reviewed with regard to programme changes. QUESTIONS Had changes occurred in the algorithms of 3 selected devices--compared to the previously published benchmark studies? Do the current versions of these investigated devices differentiate between open and closed apnoeas? METHOD With a self-developed respiratory pump, sleep-related breathing patterns and, with the help of a computerised valve, resistances of the upper respiratory tract were simulated. Three different auto-CPAP devices were subjected to a bench test with and without feedback (open/closed loop). RESULTS Open loop: the 3 devices showed marked differences in the rate of pressure rise but did not differ from the earlier published results. From an initial pressure of 4 mbar the pressure increased to 10 mbar after a different number of apnoeas (1-6 repetitive apnoeas). Only one device differentiated between closed and open apnoeas. Closed loop: due to the pressure increase, the flow generator simulated reduced obstruction of the upper airways (apnoeas changed to hypopnoeas, hypopnoeas changed to flattening) but different patterns of pressure regulation could still be observed. CONCLUSION By applying bench-testing, the algorithms of auto-CPAP devices can regularly be reviewed to detect changes in the software. The differentiation between open and closed apnoeas should be improved in several APAP devices.