Search PubMed⌕ Search

Biomedical subjects

T Penzel

Publications and source records attributed to T Penzel.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1996

[Spectral analysis of blood pressure in patients with sleep related respiratory disorders].

Spectral analysis is a helpful tool to investigate the interaction of blood pressure, respiration and sleep (6). The analysis of systolic pressure is most suitable for the documentation of compressed spectral arrays, since there are less disturbances than from the heart rate. The method used in this study allows the discrimination and quantitative evaluation of periodic blood pressure oscillations associated with apneic and breathing phases. It could be shown that the amplitude of the pulsus paradoxus increases during episodes of obstructive snoring. Heavy snore showed rather stable respiratory frequencies during the whole night which was not found that distinctly in patients with obstructive sleep apnea. The parallel analysis of blood pressure variations and sleep phases revealed different mechanisms in the regulation of REM- and non-REM sleep which transfer sleep related breathing disorders from a periodic pattern in a nonperiodic one and hereby influence at least the regulation of heart rate and blood pressure.

Adult↗
PubMed1996

[Long-term analysis of respiration in sleep].

We completed polysomnography and complementary measurement of the oesophageal pressure and airflow in 6 subjects (2 volunteers, 4 patients with sleep-related breathing disorder). The evaluation of the physiological parameters of the breathing over the whole night showed a strong correlation between the pressure-time product and the work of breathing. Our results revealed distinct differences between the parameters of the breathing mechanics in volunteers versus in patients. The continuous long-term analysis of respiration during sleep may contribute to reveal further pathological mechanisms of the respiratory system.

Adult↗
PubMed1996

Electrical stimulation of upper airway musculature.

Investigators have postulated that pharyngeal collapse during sleep in patients with obstructive sleep apnea (OSA) may be alleviated by stimulating the genioglossus. The effect of electrical stimulation (ES) of the genioglossus on pharyngeal patency was examined in an isolated feline upper airway preparation and in apneic humans during sleep. We found that stimulation of the genioglossus (n = 8) and of the hypoglossal nerve (n = 1) increased maximum airflow through the isolated feline upper airway in humans during sleep. Additional findings in the isolated feline upper airway suggest that such increases in airflow were due to decreases in pharyngeal collapsibility. The evidence suggests that improvements in airflow dynamics with electrical stimulation are due to selective recruitment of the genioglossus, rather than due to nonspecific activation of the pharyngeal musculature or arousal from sleep. The implications of these results for future therapy with ES are discussed.

Animals↗
PubMed1995

Blood pressure analysis.

Arterial blood pressure is influenced by sleep-related breathing disorders. As cardiovascular consequences can be diagnosed by an accurate recording and analysis of blood pressure, new recording methodologies and an approach to analysis are presented here. Invasive continuous blood pressure recording is the common reference for all methodologies. As blood pressure varies rapidly in parallel with sleep-related breathing disorders it is indispensible to record blood pressure continuously. To introduce non-invasive methodology the Finapres system was used during sleep studies; a validation study showed severe limitations. This study was followed by the validation of an improved system called Portapres, which is portable, has two finger cuffs and a hydrostatic height compensation. Analysis of continuous blood pressure in patients with sleep apnoea is carried out to detect mechanisms which influence the cardiovascular risk. Spectrum analysis of systolic blood pressure showed two different major oscillations present in patients with obstructive sleep apnoea. One oscillation (<0.06 Hz) occurs in parallel with each apnoeic episode and the other oscillation (0.2-0.4 Hz) occurs in parallel with the obstructive efforts during each apnoea and in parallel with respiration during periods of snoring. These two oscillations were so specific that the use of non-invasive continuous blood pressure recording allowed an estimation of the extent of underlying breathing disorders, and assessment of cardiovascular risk in a patient with obstructive apnoea in terms of hypertension and on the basis of ambulatory monitoring.

Journal Article↗