Detection of sleep apnea with the forced oscillation technique compared to three standard polysomnographic signals.

BACKGROUND: The forced oscillation technique (FOT) allows analysis of the upper airway impedance and, hence, detection of obstructive sleep apnea. OBJECTIVE: To evaluate FOT with respect to sensitivity and to specificity in online detection of sleep-disordered breathing patterns and to compare algorithmic onset detection time with manual onset time markers of staff physicians. METHODS: We compared the absolute value mid R:Zmid R: of the impedance with three routinely obtained polysomnographic signals - nasal airflow V(nasal), thoracic excursion Thox and esophageal pressure P(es) - by retrospective analysis of the diagnostic polysomnograms of 51 patients. For each signal we evaluated algorithms for online detection of respiratory events. For each out of five apnea classes, 50 respiratory events marked by staff physicians were drawn randomly from the 51 polysomnograms to optimize the online detection algorithms (learning set). The algorithm analyzes relative changes of signal baseline and amplitude. Again 50 respiratory events were drawn randomly for each apnea class to examine to what extent it is possible to detect event onsets with the algorithms (test set). RESULTS: The sensitivity of the signals varied between 56 and 94% and was on average 74%. The specificity was 96 +/- 1.5% on average. The onset was detected 4-6 s after the initially evaluated onset of the staff physicians. CONCLUSION: We conclude that nasal airflow and FOT are equivalent sensitive measurands for detection of respiratory events.

Detection of obstructive sleep apnea by analysis of phase angle using the forced oscillation signal.

Pharyngeal collapse in patients with obstructive sleep apnea syndrome (OSAS) is linked to decreased upper airway muscle activity. We hypothesised that decreased muscle activity causes decreased stiffness of the upper airway wall and assumed that a decrease in wall stiffness would result in a change point (CP) of the morphology of phase angle time series phi(t) obtained by forced oscillation technique (FOT). We developed an algorithm to detect CPs in φ(t) and investigated phi(t) data measured in parallel to all-night polysomnography in seven patients. A total of 2724 CPs were detected by algorithm. The CPs were marked on the polysomnograms and compared with polysomnogram scoring performed jointly by three sleep expert physicians. A total of 791 (67%) of the 1172 handscored respiratory events showed a CP in phi(t) within a time interval of 8 sec before and 6 sec after the marked onset. A total of 672 (57%) respiratory events were detected at an earlier time by algorithm, and 119 (10%) were algorithmically detected later. The average detection time by the CP algorithm was 4.0+/-1.1 sec earlier than the manual scoring. We conjecture that a CP in phi(t) indicates a change in upper airway collapsibility and that phi(t) might be a potentially useful parameter for detection of impending upper airway obstruction.

Early detection of upper airway obstructions by analysis of acoustical respiratory input impedance.

Repetitive occurrence of partial or total upper airway obstruction characterizes several respiratory dysfunctions such as the obstructive sleep apnea syndrome (OSAS). In OSAS patients, pharyngeal collapses are linked to a decrease in upper airway muscle activity during sleep which causes decreased upper airway wall stiffness. Continuous positive airway pressure (CPAP) is recommended as the treatment of choice. Advancements in CPAP therapy require early detection of respiratory events in real time to adapt the level of the applied pressure to airway collapsibility. The forced oscillation technique (FOT) is a noninvasive method which reflects patients' airway patency by measuring respiratory impedance. The aim of this study was to evaluate by a mathematical model of the respiratory system if FOT can provide an early detection index of total or partial upper airway obstruction. Furthermore, the simulation should suggest which characteristic features are relevant for early apnea detection in measured clinical data. The respiratory system has been treated as a series of cylindrical segments. The oropharynx analog of the model allows simulation of upper airway collapse, mimicking the situation in patients with OSAS. We calculated the input impedance for different degrees of upper airway obstruction ranging from unobstructed airways to total occlusion. Furthermore, we simulated different upper airway wall compliances. We compared the simulation with real data. The results of the study suggest that FOT is a valuable tool for assessing the degree of upper airway obstruction in patients with OSAS. Especially, the phase angle of the impedance seems to be a potentially useful tool for early apnea detection by assessing the upper airway wall collapsibility.

Suppressed activities of cathepsins and metalloproteinases in the chronic model of puromycin aminonucleoside nephrosis.

Glomerulosclerosis and tubulointerstitial fibrosis are the hallmarks of chronic renal diseases. In the present study, we have investigated the potential involvement of various proteinases in these alterations in the model of puromycin aminonucleoside (PAN) nephrosis. Two groups of male Wistar rats were given either three or seven injections of PAN (2.0 mg/100 g body weight) over a 4- and 12-week period, respectively. The two control groups received saline injections. Activities of cathepsins (B, H and L) were determined in isolated glomeruli and proximal tubules. Moreover, collagenase-like and gelatinase-like activities were analyzed in isolated glomeruli. Three weeks after weekly PAN injection, the rats developed heavy proteinuria (140.8+/-22.0 vs. 13.5+/-3.29 mg/day; p<0.001), and at week 11 protein excretion reached 606.6+/-23.00 vs. 22.8+/-1.5 mg/day. Renal morphology revealed minimal glomerular mesangial changes at the 4th week after PAN administration. At the 12th week a marked mesangial matrix accumulation as well as severe tubulointerstitial infiltration and fibrosis associated with tubular dilation and atrophy were observed. Glomerular cathepsins B, H, and L and gelatinase-like activities decreased at the 4th week after the first PAN injection and remained at this low level throughout the entire study period. Glomerular collagenase-like activity decreased at the 4th week (p<0.05) and was still mildly lower than that of the control group at the 12th week, but without significance. In the isolated proximal tubules, the activities of cathepsins B, H, and L showed the same pattern of decreases as those found in the glomeruli over the whole experimental period. Taken together, our data in the model of chronic PAN nephrosis suggest that the suppressed activities of cathepsins as well as the decreased gelatinase- and collagenase-like activities participate in the accumulation of extracellular matrix and thereby may contribute to the development of glomerulosclerosis and tubulointerstitial fibrosis.

Evaluation of forced oscillation technique for early detection of airway obstruction in sleep apnea: a model study.

The forced oscillation technique (FOT) is a non-invasive method which may be suitable for assessing upper airway obstruction in obstructive sleep apnea/hypopnea syndrome (OSAS) patients. The aim of this study was to determine in vitro if FOT can provide an early detection index of total or partial upper airway occlusion. A respiratory system analog was developed which includes an upper airway analog that allows simulation of upper airway collapse (thus mimicking the situation in patients with OSAS). We simulated different degrees of upper airway obstructions ranging from 0 (unobstructed airways) to 1 (total occlusion). Furthermore, we imitated the collapsible upper airway wall by means of elastic membranes with ten different wall compliances ranging from 3.3 x 10(-4) to 1 1/mbar. For the two stiffest rubber membranes (Cwall = 0.01 and 3.3 x 10(-4) l/mbar) the absolute value of the impedance (¿Z¿) showed a marked increase for obstructions greater than 0.6. For the two membranes with the highest wall compliances (Cwall = 0.03 and 1 1/mbar) obstructions with an increase in ¿Z¿ could not be detected before the obstruction reached 0.8. For degrees of obstruction less than 0.6 the phase angle of collapsible membranes with low compliance (stiff airway wall) were about 1.5pi which significantly differed from phase angles of 1.77pi measured in membranes with high compliance (elastic airway wall); p < 0.01. We hypothesized that stiffness of upper airway walls corresponds with their muscle tone, i.e., stiff airway walls are related with high muscle tone and vice versa. Thus, a decrease in upper airway muscle activity would cause an increase of upper airway wall elasticity that enables upper airway collapse. As a consequence the phase angle phi could be expected to change from values characterizing stiff membranes to values characterizing more elastic membranes which could be used as early indicator for obstructive respiratory events. We have frequently observed such changes in morphology of phi(t) data obtained from patients with OSAS.

Low-velocity gunshot wounds to the spine with an associated transperitoneal injury.

Twenty-nine patients who incurred a transperitoneal low-velocity gunshot wound to their spine were evaluated for the occurrence of spinal infectious complications. All patients underwent an exploratory laparotomy to determine the extent of viscera involvement. No attempt was made to debride the involved spinal area, and the bullet was not removed unless it was easily accessible. Of the 21 patients with a parenchymal and/or noncolonic viscous injury, 17 (77%) were treated with intravenous (i.v.) antibiotics for a minimum of 5 days the remainder received treatment for a maximum of 48 h. All 8 patients with colonic injuries received a minimum of > or = 5 days of antibiotic treatment. Follow-up averaged 44.9 months (range 3-144 months). Only 1 (4.7%) patient with either a noncolonic or parenchymal perforation developed an infectious complication (subdiaphragmatic abscess); two patients (25%) with colonic perforations developed a psoas abscess. No patient developed a spinal infection. This study suggests that patients who sustain a transperitoneal low-velocity gunshot wound to their spine do not need to undergo spinal debridement and may be treated with parenteral antibiotics. Any course of broad-spectrum antibiotics for 5 days appears to minimize infectious complications. Bullet removal and missile tract debridement of the spine is not routinely necessary.

Chemically defined structured lipids with omega-3 fatty acids maintain splanchnic blood flow in a low-dose continuous endotoxin model.

BACKGROUND: Disturbances of microcirculation and accompanying alterations of oxygen supply are central pathophysiological events in trauma and sepsis. There is evidence that omega-3 fatty acids can modulate prostaglandin formation and thereby regional blood flow. The aim of the study was to determine the effects of chemically defined structured lipids (SL) with omega-3 fatty acids in position sn-2 (MFM) compared to SL with omega-6 fatty acids in position sn-2 (MLM) on cardiac output (CO) and splanchnic blood flow in a low-dose endotoxin (E, 1 mg.kgBW-1.day-1) rat model. MATERIALS AND METHODS: 24 male Sprague Dawley rats, divided in 4 groups (n = 6; MLM, MLM+E, MFM, MFM+E) received for 48 h a total parenteral nutrition. CO and regional blood flow were measured with 85strontium-labelled microspheres (16.5 +/- 0.1 microns). RESULTS: There was a slight rise in CO in the E groups compared to the control groups. Application of E resulted in a marked decrease of intestinal perfusion in the MLM-fed animals, whereas the MFM-fed animals showed only a minimal reduction. This decrease of portal blood flow to the liver was accompanied by an elevation of arterial blood flow to the liver. This compensatory increase in arterial liver blood flow was more pronounced in the MFM-fed animals, resulting in a total liver blood flow which was not different from the control group. CONCLUSIONS: The results of this study implicate that 48 h of intravenous feeding with chemically defined SL with an omega-3 fatty acid in position sn-2 can significantly influence splanchnic bed perfusion in a low-dose endotoxin rat model. The better splanchnic perfusion may be mediated by a shift in prostaglandin production.

Parents' needs after ultrasound diagnosis of a fetal malformation: an empirical deficit analysis.

We studied 56 pregnant women and 24 partners after ultrasound examination in the 18-24h gestational week revealed a fetal malformation. The subjects were followed through the process of examination, information sharing and counselling about the option of terminating the pregnancy. Regardless of sociodemographic variables or attitude towards the pregnancy, the diagnosis was always traumatic. A detailed critique of the physician's behavior and function emphasized his important role in the process of coming to terms with the malformation and gave clear indications of the positive expectations parents had. The affected patients expected the role of the professionally competent expert to be combined with that of the empathetic approachable counsellor, whose ste-by-step explanation would allow them to decide for themselves whether to terminate the pregnancy. The partner's participant was an essential aid to adjustment. It remains to be seen to what extent the functions of the doctor are realistic and justified.

Effect of dietary protein on glomerular proteinase activities.

Recent studies suggest that proteolytic enzymes are involved in the degradation of extracellular matrix components of the renal glomerulus. In the present study, the effects of feeding 3 different protein diets on glomerular cysteine proteinase and metalloproteinase activities to healthy rats for 6 weeks were examined. The diets contained 5, 20, or 60% casein and were made isocaloric by starch. On sacrifice, the glomeruli were isolated by differential sieving. Proteolytic activities were measured using fluorogenic substrates and were expressed per glomerular DNA content. Body weight was virtually unchanged by the amount of protein ingested, whereas kidney weight was closely correlated with dietary protein content (5%: 1,625 +/- 324; 20%: 2,110 +/- 326; 60%: 2,705 +/- 910 mg). Activity of cathepsin B, the most abundant cysteine proteinase in the glomerulus, decreased with protein loading (5%: 1,498 +/- 110; 20%: 1,321 +/- 82; 60%: 914 +/- 84 pmol/min/micrograms DNA). The same pattern emerged with cathepsin L (5%: 869 +/- 71; 20%: 846 +/- 70; 60%: 517 +/- 83 pmol/min/micrograms DNA) and cathepsin H (5%: 498 +/- 45; 20%: 478 +/- 55; 60%: 330 +/- 39 pmol/min/micrograms DNA). The differences between the 20 and 60% groups were statistically significant for all 3 cathepsins measured. The intraglomerular activity of the metalloproteinase collagenase declined significantly with the amount of protein ingested (5%: 233 +/- 14; 20%: 189 +/- 13; 60%: 137 +/- 11 microU/micrograms DNA). Gelatinase activity also fell as protein intake increased (5%: 183 +/- 18; 20%: 115 +/- 10; 60%: 94 +/- 11 F/micrograms DNA).(ABSTRACT TRUNCATED AT 250 WORDS)