Short-term variability of blood pressure during sleep in snorers with or without apnea.

In normal subjects, the level and variability of blood pressure decrease during non-rapid eye movement (non-REM) sleep. In contrast, sleep apnea is associated with large swings in nocturnal pressure. In this study, we evaluated a computer-derived index of all-night blood pressure variability in normotensive snorers with or without sleep apnea. We also examined this index in snorers receiving medical treatment for coexistent ischemic heart disease. Beat-to-beat blood pressure was recorded with a photoplethysmographic device (Finapres) throughout polysomnography. Subjects were categorized into four groups: those without cardiovascular disease without or with sleep apnea (> or = 15 apnea plus hypopnea per hour of sleep), and those with ischemic heart disease without or with sleep apnea. A frequency distribution histogram of all increases and decreases of blood pressure according to their amplitudes was drawn and the SD of the distribution used as an estimation of variability. Mean systolic and diastolic pressures during the total sleep time were not different among the four groups. In contrast, the SD of the distribution of systolic and diastolic pressure variations that were higher in the apneic than in the nonapneic groups (P < .05) correlated with apnea plus hypopnea (P < .0001) and transient electroencephalographic arousal number per hour of sleep (P < .0001). In both apneic and nonapneic subjects, blood pressure variability as assessed by SD decreased during stages 3 and 4 of non-REM sleep compared with stages 1 and 2 and REM sleep (P < .001). Blood pressure variability was similarly increased in apneic subjects with or without ischemic heart disease. We speculate that in apneic individuals with coexistent ischemic heart disease, pressure variability that is increased despite treatment with beta-blockers or calcium antagonists may be a risk factor for acute coronary events.

Evaluation of an ambulatory device, CID 102, in the diagnosis of obstructive sleep apnoea syndrome.

Diagnosis of obstructive sleep apnoea syndrome (OSAS) is usually performed during overnight polysomnography in the sleep laboratory. In an attempt to simplify the diagnostic strategy, we compared an ambulatory device, CID 102, with polysomnography during the same night in the laboratory in 50 consecutive patients referred for polysomnography. The CID 102 device monitors oxygen saturation, heart rate, body position and tracheal breath sounds. An acoustic pressure sensor is placed on the suprasternal notch. Signals coming from this sensor are amplified and analysed in three different channels, according to their frequency and energy. CID respiratory disturbance index is defined as the number, per hour of analysis time, of apnoeas lasting more than 10 s plus episodes of desaturation by 4% or more associated with pauses lasting from 7-10 s or snores. The polysomnographic data were recorded on paper (Reega 2000, Alvar) and analysed manually. Polysomnographic apnoea-hypopnoea index (AHIp) was defined as the number of apnoeas plus hypopnoeas per hour of sleep. The sensitivity, specificity, positive predictive value and negative predictive value of various CID respiratory disturbance index (> or = 5, > or = 10, > or = 15 and > or = 20 per hour) in diagnosing obstructive sleep apnoea syndrome were determined. When OSAS was diagnosed as AHIp > or = 15, sensitivity and specificity of a CID respiratory disturbance index > or = 5 were 73 and 62%, respectively. Positive predictive value of CID respiratory disturbance index > or = 10 for AHIp > or = 10 was 94%. CID 102 false negative patients had only hypopnoeas without any desaturation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic method to estimate the longitudinal area profile of endotracheal tubes.

A problem in mechanical ventilation is the accumulation of mucus secretions in the endotracheal tube (ETT), which tends to reduce the patent cross-sectional area. Here we characterized the extent and locus of the ETT obstruction using an acoustic reflection method recently modified to be applied at bedside. Experiments were conducted both in vivo in 10 intubated patients and in vitro in ETT with or without known constrictions of 1 to 3 mm over 5 cm, located at various distances from the ETT entry: 5, 10, 15, and 20 cm. Acoustic results were compared with the results obtained by an hydraulic reference method, which was the only method available to measure ETT obstruction in mechanically ventilated patients. In vivo acoustic results showed that area reductions were maximal near the tracheal extremity of the ETT, with a range from 2 to 36% (mean value 13 +/- 10%), when estimated relative to the area measured in an unused ETT of the same inner diameter (7 to 9 mm). Statistical analysis of the differences between acoustic reflection data and hydraulic data showed that the two methods did not differ significantly. In vitro acoustic results obtained in constricted ETT showed a highly significant correlation with the actual area (r = 0.97, p = 0.0001). Thus, reductions in ETT area may be detected, quantified, and located by the present acoustic reflection method, which therefore provides a means to avoid emergency extubation because of ETT obstruction.

Effects of N-acetylcysteine on diaphragmatic function and malondialdehyde content in Escherichia coli endotoxemic rats.

We evaluated the effects of sublethal Escherichia coli endotoxemia with or without concomitant administration of N-acetylcysteine, an antioxidant agent, on diaphragmatic strength, endurance, and malondialdehyde (MDA) content in rats. One hundred ninety rats were inoculated subcutaneously on 2 successive days with 0.6 and 1.2 mg/100 g body weight of E. coli lipopolysaccharide respectively (E animals, n = 100) or saline (C group, n = 90). E and C animals were divided into two groups based on administration of endotoxin or saline alone (E group, n = 55; C group, n = 47, respectively) or endotoxin or saline plus N-acetylcysteine (1 g/kg body weight/day intraperitoneally) (E-NAC group, n = 45; C-NAC group, n = 43, respectively). Diaphragmatic strength was assessed in vivo 48 h after the first endotoxin or saline administration by measuring the transdiaphragmatic pressure (Pdl) generated during electrical stimulation of the phrenic nerves at 0.5, 10, 20, 30, 50, and 100 Hz. Endurance index was calculated as the percent ratio of Pdl generated after 30 s of phrenic stimulation at 10 Hz divided by the initial force. Diaphragmatic MDA (fluorometric technique) was measured 0, 6, 18, 30, 42, and 48 h after the first dose of endotoxin or saline. Pdl for 50 and 100 Hz was significantly reduced in Group E as compared with group C. This phenomenon was associated with a reduced endurance performance as assessed by a lower diaphragmatic endurance index in E as compared with C animals (90.9 +/- 4.2 versus 114.3 +/- 4.1 respectively; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)