PubMed Health⌕ Search

Biomedical subjects

T Penzel

Publications and source records attributed to T Penzel.

At least 55 records · Page 3Linked to original sources
PubMed1999

Vigilance transitions in reaction time test: a method of describing the state of alertness more objectively.

Electrophysiological recordings are considered a reliable method of assessing a person's alertness. The aim of this study was to show, firstly, that changes in alertness during a Reaction Time Test (RTT) can be determined with certain adaptive scoring stages but not with R&K scoring and secondly, that the different adaptive stages can explain findings in reaction time. In 17 male patients (50.8+/-9.7 years, Body-Mass Index (BMI) 31.9+/-5.1 kg/m2) diagnosed with Obstructive Sleep Apnea Syndrome (OSAS) (Respiratory Disturbance Index (RDI) 53.3+/-24.1 /h sleep) a 90 min daytime vigilance test was performed twice, after the diagnostic polysomnographic investigation and after two nights spent with nCPAP. After a computerised adaptive segmentation analysis, a visual rule-defined classification system categorised alertness into one of 12 adaptive scoring stages. 6 of the 12 stages are described by the alertness conditions comparable to WAKE and NREM1.4 stages are nearly classified as NREM2-4, Rapid Eye Movement (REM) and Movement Time (MT), and one stage reflects the increase of alertness from drowsiness. The typical stage of an alert subject increased significantly from a median of 65.9% before therapy to 80.8% in the second investigation. The percentages of clearly drowsy stages decreased significantly. In contrast, there were no significant changes in the percentages of sleep stages according to R&K criteria for both investigations. According to R&K criteria 178 of 398 failed reactions (Reaction time >10 s) occurred in stage WAKE. According to adaptive scoring, only 12 failed reactions appeared in the alert stage. During the other failed reactions the electrophysiological recordings showed decreases in alertness. Neither the visual assessment nor the descriptive statistical results of R&K scoring were helpful to interpret the patient's alertness condition. In contrast, the patients' increases in alertness with nCPAP could be described by the adaptive scoring stages. This method could be a very useful procedure, when an expert opinion is necessary. It also has an actual context to the discussion of the effectiveness of CPAP in the treatment of OSAS.

Adult↗
PubMed1999

Quality control of polysomnographic sleep data by histogram and entropy analysis.

OBJECTIVE AND METHODS: Sixteen polysomnographic recordings from 8 European sleep laboratories were analyzed. The histogram analysis was used to introduce quality control of all-night EEG recordings. RESULTS: It was found that the header information does not always provide the real saturation values of the recording equipment. The entropy measure was used for the quantitative analysis of the dynamic range of routinely used polysomnographic recorders. It was found that the recording equipment provides EEG data with entropy in the range of 8-11 bits. CONCLUSION: In the all-night sleep EEG were observed non-linearities. It is recommended that the equipment provide the saturation values in order to apply automated overflow detection.

Humans↗
PubMed1999

Sleep-related breathing disorder is an independent risk factor for systemic hypertension.

The exact influence of sleep-related breathing disorder (SRBD) on blood pressure control remains unknown. We investigated the influence of different degrees of SRBD on daytime blood pressure and its association to documented hypertension by examining 1,190 consecutive patients referred for diagnosis of SRBD. The protocol includes clinical interview, physical examination, office blood pressure measurement, cholesterol, and blood gas analysis. Unattended home monitoring of nocturnal breathing was performed for assessment of SRBD activity (respiratory disturbance index [RDI]). RDI was independently and linearly associated with systolic blood pressure (unstandardized coefficient [B] = 0.07 +/- 0.03, p = 0.03), diastolic blood pressure (B = 0.07 +/- 0.02, p = 0 < 0.001), and heart rate (B = 0.10 +/- 0.02, p < 0.001) at rest. The relative risk for hypertension (blood pressure >/= 160/95 mm Hg) increased with SRBD severity (odds ratio [OR], 4.15 for RDI >/= 40 versus < 5 [95% CI, 2.7 to 6.5]). This relative risk was also elevated in younger (</= 50 yr) compared with older patients (> 50 yr) (OR, 7.15 versus 2.70 for RDI >/= 40 versus < 5). These cross-sectional clinical data suggest a relationship between SRBD severity and systolic blood pressure, diastolic blood pressure, and heart rate after control for confounders such as body mass index (BMI), age, alcohol/nicotine consumption, cholesterol level, and daytime PO(2) and PCO(2). SRBD is an independent risk factor for systemic hypertension with an increased likelihood in subjects </= 50 yr of age.

Age Factors↗
PubMed1999

Arousal in patients with gastro-oesophageal reflux and sleep apnoea.

Nocturnal gastro-oesophageal reflux has been observed in patients with obstructive sleep apnoea (OSA). Negative intrathoracic pressure during apnoeas and arousal have been suggested as the underlying mechanisms. In order to evaluate this hypothesis, the coincidence and sequence in time of arousal, apnoea and reflux events were analysed. Fifteen patients with OSA or heavy snoring were studied by means of standard polysomnograpy with parallel recording of 24-h oesophageal pH. Reflux events during the day were present in all patients, five of whom had symptoms of reflux. In three of these and in five other patients, a total of 69 nocturnal reflux events were found. In 68 events, arousal was found with the reflux event. Only one reflux without arousal was found (sleep stage 2). Seventeen events occurred during wakefulness after sleep onset. The percentage of time with a pH of <4 during wakefulness after sleep onset was significantly higher than the percentage of time with a pH of <4 during total sleep time (p<0.05). In 37 of the 52 reflux events which occurred during sleep, either an apnoea or a hypopnoea was found prior to the event. The investigation of sequence in time did not prove a causal relation between respiratory events and reflux events. The results indicate that gastro-oesophageal reflux and obstructive sleep apnoea are two separate disorders, which both have a high prevalence in obese patients.

Adult↗
PubMed1998

Sleep fragmentation and daytime vigilance in patients with OSA treated by surgical maxillomandibular advancement compared to CPAP therapy.

Impaired vigilance is a frequent daytime complaint of patients with obstructive sleep apnoea (OSA). To date, continuous positive airway pressure (CPAP) is a well established therapy for OSA. Nevertheless, in patients with certain craniofacial characteristics, maxillomandibular advancement osteotomy (MMO) is a promising surgical treatment. Twenty-four male patients with OSA (pretreatment respiratory disturbance index (RDI) 59.3 SD +/- 24.1 events/h) participated in this investigation. The mean age was 42.7 +/- 10.7 years and the mean body mass index was 26.7 +/- 2.9 kg/m2. According to cephalometric evaluation, all patients had a narrow posterior airway space, more or less due to severe maxillary and mandibular retrognathia. All patients except two were treated first with CPAP for at least 3 months and afterwards by MMO. Two patients only tolerated a CPAP trial for 2 nights. Polysomnographic investigation and daytime vigilance were assessed before therapy, with CPAP therapy and 3 months after surgical treatment. Patients' reports of impaired daytime performance were confirmed by a pretreatment vigilance test using a 90-min, four-choice reaction-time test. The test was repeated with effective CPAP therapy and postoperatively. Daytime vigilance was increased with CPAP and after surgical treatment in a similar manner. Respiratory and polysomnographic patterns clearly improved, both with CPAP and after surgery, and showed significant changes compared to the pretreatment investigation. The RDI decreased significantly, both with CPAP (5.3 +/- 6.0) and postoperatively (5.6 +/- 9.6 events/h). The percentages of non-rapid eye movement Stage 1 (NREM 1) sleep showed a marked decrease (with CPAP 8.2 +/- 3.6% and after MMO 8.2 +/- 4.4% vs. 13.3 +/- 7.4% before treatment), whereas percentages of slow wave sleep increased significantly from 8.0 +/- 6.1% before therapy to 18.2 +/- 12.8 with CPAP and 14.4 +/- 7.3% after MMO. The number of awakenings per hour time in bed (TIB) was significantly reduced after surgery (2.8 +/- 1.3), compared to both preoperative investigation (baseline 4.2 +/- 2.0 and CPAP 3.4 +/- 1.5). Brief arousals per hour TIB were reduced to half with CPAP (19.3 +/- 20.0) and after MMO (19.7 +/- 13.6), compared to baseline (54.3 +/- 20.0). We conclude that the treatment of OSA by MMO in carefully selected cases has positive effects on sleep, respiration and daytime vigilance, which are comparable to CPAP therapy.

Adult↗
PubMed1998

Expiratory flow limitation and intrinsic positive end-expiratory pressure in obesity.

Breathing at very low lung volumes might be affected by decreased expiratory airflow and air trapping. Our purpose was to detect expiratory flow limitation (EFL) and, as a consequence, intrinsic positive end-expiratory pressure (PEEPi) in grossly obese subjects (OS). Eight OS with a mean body mass index (BMI) of 44 +/- 5 kg/m2 and six age-matched normal-weight control subjects (CS) were studied in different body positions. Negative expiratory pressure (NEP) was used to determine EFL. In contrast to CS, EFL was found in two of eight OS in the upright position and in seven of eight OS in the supine position. Dynamic PEEPi and mean transdiaphragmatic pressure (mean Pdi) were measured in all six CS and in six of eight OS. In OS, PEEPi increased from 0.14 +/- 0.06 (SD) kPa in the upright position to 0.41 +/- 0.11 kPa in the supine position (P < 0.05) and decreased to 0.20 +/- 0.08 kPa in the right lateral position (P < 0.05, compared with supine), whereas, in CS, PEEPi was significantly smaller (<0.05 kPa) in each position. In OS, mean Pdi in each position was significantly larger compared with CS. Mean Pdi increased from 1.02 +/- 0.32 kPa in the upright position to 1.26 +/- 0.17 kPa in the supine position (not significant) and decreased to 1. 06 +/- 0.26 kPa in the right lateral position (P < 0.05, compared with supine), whereas there were no significant changes in CS. We conclude that in OS 1) tidal breathing can be affected by EFL and PEEPi; 2) EFL and PEEPi are promoted by the supine posture; and 3) the increased diaphragmatic load in the supine position is, in part, related to PEEPi.

Adult↗
PubMed1998

Circadian reactions to nCPAP treatment.

To determine possible effects of apnea attacks on the spontaneous behavior of the circadian system (body temperature, sleeping behavior, vigilance), 11 patients with obstructive sleep apnea (OSA) were observed before therapy over a 24 h period under a special constant routine (bed-rest study) and again during therapy with nCPAP (nasal continuous positive airway pressure). Clinical indicators (polysomnographical, subjective sleep quality, etc.) indicated successful therapy. During the bed-rest study with nCPAP therapy, the 24 h amplitude of core temperature was found to be greater than the amplitude measured before therapy. Also, therapy decreased sleep disturbances at night and reduced daytime sleeping times. Consequently, the level of subjective vigilance was higher during the daytime during therapy. OSA attacks do not only impair sleep; they disturb the whole circadian system. This may also impair recuperation and sleep. Further research should test whether measurements of the spontaneous circadian system could have additional diagnostic value and whether the stabilization of the circadian system has therapeutic value.

Adult↗
PubMed1997

[Effect of noninvasive ventilation on work of breathing in obesity].

BACKGROUND: Noninvasive ventilation with nose- or face-masks has been increasingly used in the past. The objective of mechanical ventilation is in addition to improve gas exchange to reduce breathing work. While improvement on breathing work has been shown mainly on normal-weight patients with different respiratory diseases, there is no existing data about the effect of noninvasive ventilation on the breathing work of patients with massive obesity. PATIENTS AND METHODS: Assisted mask-ventilation with bilevel positive airway pressure (BiPAP) was carried out on 5 overweight control subjects (overweight controls), 7 overweight patients with obstructive sleep apnea (OSA), 6 patients with obesitas-hypoventilation syndrome (OHS), and 7 overweight patients with chronic obstructive lung disease (COLD). Inspiratory pressure assist (IPAP) was set to 12 or 16 cm H2O, exspiratory pressure (EPAP) was set to 5 cm H2O. All, subjects were massive overweight (body mass index [BMI] 42.2 +/- 5.8; range 31.8 to 55.4 kg/m2). Respiratory muscle activity was measured as esophageal pressure change (delta Pes) and transdiaphragmatic pressure change (delta Pdi) and calculated as pressure time integral. RESULTS: With noninvasive ventilation respiratory muscle activity was significantly (p < 0.05) reduced in all groups at least 40% compared to baseline values during spontaneous respiration. CONCLUSIONS: Noninvasive ventilation via face masks can efficiently reduce work of breathing in subjects with massive obesity.

Adult↗
PubMed1997

Influence of noninvasive positive pressure ventilation on inspiratory muscle activity in obese subjects.

Noninvasive positive pressure ventilation (NPPV) can improve ventilation in obese subjects during the postoperative period after abdominal surgery. Compared to nasal continuous positive airway pressure (nCPAP), NPPV was superior in correcting blood gas abnormalities both during the night-time and during the daytime in a subgroup of patients with the obesity hypoventilation syndrome (OHS). However, as it is unknown, if and to what extent NPPV can unload the respiratory muscles in the face of the increased impedance of the respiratory system in obesity, this is what was investigated. Eighteen obese subjects with a body mass index > or = 40 kg x m(-2) were investigated during the daytime, which included five healthy controls (simple obesity (SO)), seven patients with obstructive sleep apnoea (OSA) and six patients with the obesity hypoventilation syndrome (OHS). Assisted PPV was performed with bi-level positive airway pressure (BiPAP), applied via a face mask. Inspiratory positive airway pressure (IPAP) was set to 1.2 or 1.6 kPa and expiratory positive airway pressure (EPAP) was set to 0.5 kPa. Inspiratory muscle activity was measured as diaphragmatic pressure time product (PTPdi). Comparison of spontaneous breathing with BiPAP ventilation showed no significant difference in breathing pattern, although there was a tendency towards an increase in tidal volume (VT) in all three groups and a decrease in respiratory frequency (fR) in patients with OSA and OHS. End-tidal carbon dioxide (PET,CO2) with BiPAP was unchanged in SO and OSA, but was decreased in OHS. In contrast, inspiratory muscle activity was reduced by at least 40% in each group. This was indicated by a decrease in PTPdi with BiPAP 1.2/0.5 kPa from mean+/-SD 39+/-5 to 20+/-9 kPa x s (p<0.05) in SO, from 42+/-7 to 21+/-8 kPa x s (p<0.05) in OSA, and from 64+/-20 to 38+/-17 kPa x s (p<0.05) in OHS. With BiPAP 1.6/0.5 kPa, PTPdi was further reduced to 17+/-6 kPa x s in SO, and to 17+/-6 kPa x s in OSA, but not in OHS (40+/-22 kPa x s). We conclude that noninvasive assisted ventilation unloads the inspiratory muscles in patients with gross obesity.

Adult↗
PubMed1997

Effect of angiotensin converting enzyme inhibition [Cilazapril] on blood pressure recording in hypertensive obstructive sleep apneic patients.

We investigated the efficacy of an Angiotensin Converting Enzyme [ACE] inhibitor on daytime and night-time blood pressure in 55 male hypertensive patients with moderately severe to severe obstructive sleep apnea. We resolved to determine if treatment oriented towards the reduction of hypertension would be successful, despite persistent repetitive hypoxemia and sleep-disordered breathing. The study was a randomized, double-blind, single daily dose, placebo-controlled protocol, with 8 days drug intake (placebo or 2.5 mg Cilazapril) and monitoring on the final day of drug administration. Subjects underwent continuous 24-h arterial blood pressure monitoring during baseline and treatment conditions. Polysomnography was performed at night during the 24-h arterial monitoring period. Cilazapril (2.5 mg) lowered systolic, diastolic and mean blood pressure, despite persistence of repetitive obstructive apneas during sleep and the associated repetitive hypoxemia. The lowering of blood pressure occurred without a significant change in heart rate, and was noted during nocturnal sleep, performance testing and graded exercise.

Adult↗
PubMed1997

[Cardiorespiratory coupling in obstructive sleep apnea (OSA)].

Even if different mechanisms of various interactions during sleep are known, it is still unsolved by which mechanisms physiological reactions during sleep may start a pathophysiological course. Hypoxia, Hypercapnia and repetitive sympathetic elevations are well known elements in the control of the arterial resistance. Furthermore investigations in patients with sleep apnea showed changes of the pulsatile secretion pattern within the renin-angiotensin-system and the antinatriuretic peptides. These changes were reversible under nasal CPAP-therapy, nycturia as a frequent symptom disappeared. Nevertheless neither hypoxia nor intrathoracic pressure changes nor the arousals can assert the longterm influence on the blood pressure alone, a multifactorial confluence must be assumed. Further it is unclear how a tonic increase of the arterial blood pressure may occur in dependence of the REM- and NREM-sleep cycle changes as well as during daytime. First investigations in sleeping man seem to indicate, that a disturbance of the physiological coupling of breathing and circulation may present a pathogenetic element. Finally it remains open, whether the changes of the cardiorespiratory coupling during sleep of control persons and of patients with OSA are comparable, and whether they may be procured for an explanation of the pathogenesis of arterial and pulmonary hypertension. Further investigations in the control mechanisms of breathing and circulation related to the circuits of chemo- and baroreception, thresholds during wakefulness and sleep may be of decisive help to process the question, to what extent clinical states find a correlate in a disturbed cardiorespiratory coupling and, much more significantly, whether a disturbance in the physiological cardiorespiratory coupling appears already in early states of a disease. Sleep with ist complex physiology as well as with its characteristic pathophysiological phenomenon of sleep related breathing disorders has opened a new interdisciplinary field where tools like the polysomnography and electronic data analysis are used by physiologists, pathophysiologists as well as by physicians.

Adult↗
PubMed1997

[Respiratory function diagnosis during sleep: possibilities and limitations].

Diagnosis of the respiratory function during sleep is based on a continuous recording of all necessary signals. These are basically respiratory flow, respiratory effort and blood gases. In addition, sleep stages, body position and cardiovascular function have to be monitored to distinguish the different forms of sleep related breathing disorders as there are obstructive, mixed and central apnea and hypoventilation. The main evaluation is a simple counting of events and the calculation of an index related to total sleep time. These indices are of limited value because all information about the duration of the events is lost and about the severity which depends on the actual blood gas values. A computer assisted evaluation of respiration can overcome these limitations and allows to evaluate sleep stage dependencies in addition. Based on the duration of respiratory events only it was possible to distinguish patient groups which also provided different blood gas values at daytime. Determination of the critical closing pressure of the upper airways during sleep can help to quantify effects of body weight loss and other therapeutic interventions beside ventilation therapy in patients with sleep related breathing disorders. Quantitative characterisation of respiration during sleep is limited by the fact that most methods available induce changes in sleep or respiration itself. A study on healthy subjects proved an increased number of arousals during cardiorespiratory polysomnography. Therefore the added value obtained by quantitative methodology (pneumotachograph and esophageal pressure) must be weighted against non-invasive technology (inductive plethysmography). Non-invasive methods can provide comprehensive information about the respiratory function, especially if extensive computer-assisted evaluation is used. These evaluations still need further improvements. Nevertheless they can help to clarify the different types of respiratory regulation present in NREM-, REM-sleep and awake state.

Carbon Dioxide↗
PubMed1997

[Increased daytime tiredness, nocturnal hypertension and sleep apnea: studies in rural general practice].

Studies in a Rural General Practice: Sleep-Related Breathing Disorders (SRBD) and altered circadian blood pressure profile are related to increased cardiovascular risk. We investigated the prevalence and coincidence of both diseases in male patients from a general practice in a small community of 2500 people. Out of 409 selected patients (using a questionnaire regarding symptoms and findings of SRBD), 185 were monitored in an outpatient setting with an apnoea-screening system Mesam IV. Ambulatory blood pressure monitoring (Spacelabs 90207). Holter-ECG and actigraphy were also measured. Sixty patients had a Respiratory Disturbance Index (RDI) > 10. An indication for further sleep studies was seen in 40 patients; 36.5% of daytime hypertensives were "Non-Dipper", and 47.6% of normotensives were also "Non-Dipper". Excessive daytime sleepiness (EDS) is an important symptom of SRBD, and in this investigation we noticed a large number of patients without this symptom suffering from relevant SRBD. Therefore, absence of EDS alone is not indicative for the use of ambulatory monitoring.

Adult↗
PubMed1996

Unattended continuous positive airway pressure titration. Clinical relevance and cardiorespiratory hazards of the method.

The high cost of in-laboratory sleep studies and the insufficiency of available nights in most sleep laboratories has prompted clinical trials in an attempt to find an effective and safe method for continuous positive airway pressure (CPAP) titration in the unsupervised home environment. Earlier publications focused on the effectiveness of this new method but did not indicate the potential hazard and the selection criteria of patients. We accomplished a prospective study to evaluate a machine-controlled CPAP titration method in an unselected group of 21 patients with obstructive sleep apnea (OSA) requiring CPAP therapy. Unattended CPAP titrations were completed in the sleep laboratory, followed by conventional CPAP titration night. The CPAP levels assessed through automatic titrations showed strong agreement with those from the control nights. Fifteen patients had no pathologic cardiorespiratory events during machine-controlled titration. Undesirable cardiorespiratory complications developed in six patients with underlying cardiorespiratory disorder. Two patients had to stop the procedure. Two patients needed a reset of the actual pressure to baseline because of central apneas and one patient because of high-grade arrhythmia. The machine-controlled CPAP titration enabled reliable assessment of an effective pressure and appeared to be safe in selected patients with OSA. However, because the method caused significant adverse effects in some patients, we recommend that unattended CPAP titration not be attempted in patients with underlying cardiorespiratory disease.

Arrhythmias, Cardiac↗
PubMed1996

Assessment of the nocturnal blood pressure relative to sleep stages in patients with obstructive sleep apnea.

To determine the mean blood pressure relative to sleep stages, two nocturnal cardiorespiratory polysomnographs were recorded in 60 male patients with hypertension and obstructive sleep apnea (OSA). The mean age was 50.2 years, the BMI 32.0 kg/m2, the respiratory disturbance index (RDI) 44, and the blood pressure by the WHO protocol 158/98 mm Hg. A new evaluation program was used to determine the invasively measured mean arterial pressure (mean +/- SEM) and heart rate (mean +/- SEM) during sleep (mean total sleep time 361 +/- 48 min) referred to sleep stages 1 (99.5 +/- 1.5 mm Hg/67.6 +/- 1.1 bpm), 2 (98.7 +/- 1.6 mm Hg/66.6 +/- 1.1 bpm), 3 (97.6 +/- 1.8 mm Hg/67.4 +/- 1.3 bpm), and 4 (97.6 +/- 2.2 mm Hg/66.3 +/- 1.6 bpm) and to REM sleep (103.3 +/- 1.7 mm Hg/68 +/- 1.2 bpm) as 1 s mean values and to compare them with the waking state (98.3 +/- 1.6 mm Hg/83.6 +/- 1.1 bpm). There was no physiological fall in blood pressure in patients with pronounced OSA. Sleep-stage-specific analysis of invasive continuous blood pressure signals is the gold standard. The sleep structure is disturbed less than with other methods.

Adult↗