Pressure stability of nasal CPAP and bilevel devices

Summary Question of the study   Nasal continuous positive airway pressure (CPAP) prevents collapse of the upper airway during sleep in patients with obstructive sleep apnea provided that a positive transmural pressure can be maintained during inspiration. We examined pressure-flow characteristics in seven CPAP and bilevel devices during spontaneous breathing.
Methods   The CPAP devices were set to a pressure level of 9.8  hPa (10  cm H₂O) and adapted to a pneumotachograph using a standard CPAP hose and an outlet valve. We continuously measured flow, volume and pressure during resting ventilation and increasing voluntary hyperventilation and analysed the dependence of the variables on a breath-to-breath basis.
Results   Mean CPAP pressures differed between the devices (9.9 – 10.6  hPa) despite the same settings. In all machines pressure fell during inspiration to 8.4 – 9.8  hPa and increased during expiration to 11.1 – 11.7  hPa. This effect increased with higher flow rates. Maximum expiratory pressures rose to 12 – 19  hPa at peak flow rates of 2 l/s, mean expiratory pressures to 9.5 – 16  hPa. Inspiratory pressures dropped to 8.5 – 4.5  hPa (minimum) and 10.5 – 6.0 (mean). Bilevel devices showed a higher stability than CPAP devices. Pressure swings during the respiratory cycle increased the additional work of breathing.
Conclusions   Due to differences in mean and effective CPAP levels CPAP devices are not simply exchangeable but should be individually adapted. Patients with higher minute ventilation might benefit from more stable CPAP machines. The impact on patients' compliance remains to be evaluated.     

Nocturnal hypoglycaemia in Type 1 diabetic patients,assessed with continuous glucose monitoring: frequency,duration and associations

Aims We quantified the occurrence and duration of nocturnal hypoglycaemia in individuals with Type 1 diabetes treated with continuous subcutaneous insulin infusion (CSII) or multiple‐injection therapy (MIT) using a continuous subcutaneous glucose sensor. Methods A microdialysis sensor was worn at home by 24 patients on CSII (mean HbA_1c 7.8 ± 0.9%) and 33 patients on MIT (HbA_1c 8.7 ± 1.3%) for 48 h. Occurrence and duration of nocturnal hypoglycaemia were assessed and using multivariate regression analysis, the association between HbA_1c, diabetes duration, treatment type (CSII vs. MIT), fasting and bedtime blood glucose values, total daily insulin dose and mean nocturnal glucose concentrations, and hypoglycaemia occurrence and duration was investigated. Results Nocturnal hypoglycaemia ≤ 3.9 mmol/l occurred in 33.3% of both the CSII‐ (8/24) and MIT‐treated patients (11/33). Mean (± sd ; median, interquartile range) duration of hypoglycaemia ≤ 3.9 mmol/l was 78 (± 76; 57, 23–120) min per night for the CSII‐ and 98 (± 80; 81, 32–158) min per night for the MIT‐treated group. Multivariate regression analysis showed that bedtime glucose value had the strongest association with the occurrence (P = 0.026) and duration (P = 0.032) of nocturnal hypoglycaemia. Conclusions Microdialysis continuous glucose monitoring has enabled more precise quantification of nocturnal hypoglycaemia occurrence and duration in Type 1 diabetic patients. Occurrence and duration of nocturnal hypoglycaemia were mainly associated with bedtime glucose value.     

Brain perfusion territory imaging applying oblique-plane arterial spin labeling with a standard send/receive head coil.

A new method for the selective spin labeling of left- or right-sided supplying arteries of the brain without the need for additional RF coils is demonstrated. A clinical 1.5 T scanner was used. The spatial selectivity of the labeling process is based on the limited coverage of the excitation field of a standard send/receive head coil together with an oblique positioning of the labeling plane. A computer simulation was used to optimize key labeling parameters under the condition of laminar flow. The validity of the computer model results was confirmed by MRI measurements with a flow model. For human studies, a double-inversion continuous arterial spin labeling (CASL) sequence was modified to allow for arbitrary positioning of the labeling plane. The obtained perfusion-weighted images showed a clear delineation of the perfusion territories of the selected arteries in the anterior circulation of the brain and good gray/white matter contrast.     

Efficacy of continuous subcutaneous insulin infusion in Type 1 diabetes: a 2-year perspective using the established criteria for funding from a National Health Service.

AIM: To determine the 2-year efficacy of continuous subcutaneous insulin infusion (CSII) following the current established criteria for funding of a National Health Service. METHODS: Longitudinal, prospective, observational unicentre study. Included in the study were 153 Type 1 diabetes (T1D) subjects, previously treated with multiple daily injections (MDI) of insulin, in whom CSII was started in accordance with the criteria for reimbursement of the Catalan National Health Service. At baseline, we recorded data on age, gender, duration of the disease, body mass index (BMI), insulin dose and indications for CSII. Glycated haemoglobin (HbA(1c)) and the frequency of hypoglycaemic events were used to assess glycaemic control. Quality of life was assessed using three different self-report questionnaires. After 24 months, these same items were remeasured in all subjects. Serious adverse events and injection-site complications were also recorded. RESULTS: In 96% of subjects, CSII indication included less than optimal glycaemic control using MDI. HbA(1c) fell from 7.9 +/- 1.3 to 7.3 +/- 1.1% (P < or = 0.001) after 24 months of CSII. Insulin requirements were significantly lower at the end of follow-up (0.55 +/- 0.21 U/kg body weight) in comparison with before use of CSII (0.70 +/- 0.20, P < or = 0.001). BMI increased from 24.0 +/- 3.1 to 24.4 +/- 3.2 kg/m(2) after 24 months (P < or = 0.025). The rate of episodes of diabetic ketoacidosis per year remained unchanged. Mild and severe hypoglycaemic episodes were significantly reduced. The scores in all subsets of the Diabetes Quality-of-Life (DQoL) questionnaire significantly improved after 24 months of CSII. CONCLUSIONS: CSII, commenced according to the criteria for a nationally funded clinical programme, improves glycaemic control and quality-of-life outcomes with fewer hypoglycaemic episodes in T1D subjects previously conventionally treated with MDI.     

Analysis of signal-to-noise behavior in Cartesian continuous sampling sequences: predictions and experimental validation of opportunities for improved image SNR.

Image signal-to-noise ratio (SNR) limits many MRI applications. Here we propose a method to improve SNR based on continuous sampling (CS) during each TR without significant increases in acquisition time. The general concept of CS is defined here as sampling the NMR signal immediately after slice excitation including ramp times, both the dephase and rephase lobes, the phase-encoding (PE) gradient application, and the slice refocusing gradient. This study analyzes several cases of CS and demonstrates a specific case where sampling occurs during an isolated and balanced readout gradient in order to increase SNR in a rectilinear Cartesian sequence without significantly increasing overall acquisition time. The noise correlation consequences of rectilinear CS are mathematically derived and proven through simulation. The SNR improvement of up to approximately 40% measured in both phantom and asymptomatic human volunteer images is comparable to theoretical prediction of increased SNR proportional to the increase in the square root of the sampling time.     

Continuous laser radiation effect at 1.06 microns on gastrointestinal tract

The thermal effect of 1.06 microns YAG:Nd laser irradiation at temperature conditions up to 100 degrees C without crater formation on gastrointestinal (GI) tissue samples was investigated. The theoretical and experimental data show that at an intensity of 160-400 W/cm2 laser-induced heating of the tissue with an initial temperature of 20 degrees C leads to coagulation lesions at a temperature no less than 60 degrees C and at a depth of 1.7-2.1 mm.     

Pharmacokinetics of ciprofloxacin and vancomycin in patients with acute renal failure treated by continuous haemodialysis.

To determine appropriate doses of ciprofloxacin and vancomycin for septic patients with acute renal failure (ARF) treated by continuous arteriovenous and venovenous haemodialysis, (CAVHD/CVVHD), we performed pharmacokinetic studies in patients receiving these antibiotics. All patients were treated by CAVHD/CVVHD using Hospal AN69S 0.43 m2 filters and Fresenius 1.5% peritoneal dialysis fluid at dialysate flow rates (Qd) of 1 and 2 l/h. Patients received ciprofloxacin 200 mg i.v. 12-hourly (n = 6) or 8-hourly (n = 5); vancomycin 1 g i.v. was administered to 10 patients approximately every 48 h to maintain therapeutic plasma levels. For ciprofloxacin, volume of distribution (Vdarea) was 136.5 +/- 9.81, terminal elimination half-life (t1/2) 6.4 +/- 0.8 h, and total body clearance (TBC) 264.3 +/- 22.9 ml/min (mean +/- SEM). Mean sieving coefficient (S/C) was 0.76 +/- 0.05 and filter clearances at Qd 1 and 2 l/h were 16.2 +/- 1.9 and 19.9 +/- 1.1 ml/min respectively. For vancomycin, Vdarea was 60.7 +/- 5.11, t1/2 24.7 +/- 2.6 h and TBC 31.0 +/- 4.6 ml/min. Mean S/C was 0.66 +/- 0.08 and filter clearances at Qd 1 and 2 l/h 12.1 +/- 2.0 and 16.6 +/- 2.0 ml/min. These data suggest that patients with ARF treated by CAVHD/CVVHD should be given ciprofloxacin 200 mg i.v. 8-12-hourly and vancomycin every 48 h.     

Haemodynamic changes during spinal anaesthesia with slow continuous infusion or single dose of plain bupivacaine

Forty elderly patients, scheduled for orthopaedic surgery of the hip or knee were studied. Twenty patients received a single-dose spinal anaesthesia with 3 ml of plain 0.5% bupivacaine (SDSA group). Twenty patients received continuous spinal anaesthesia using a 32- or 22-gauge catheter. A bolus of 1.0 ml of plain 0.5% bupivacaine was given to ten patients and 0.5 ml to another ten, continued by an infusion at a rate of 2 ml/h. The spread of analgesia and haemodynamic changes (central venous pressure, arterial pressures, need for sympathomimetic medication) were registered. The mean dose of bupivacaine was 2.9 ml (range 1.5-5 ml) in the CSA group (3.0 ml in the SDSA group). Eight patients in the CSA group needed medication for pain during surgery compared to five patients in the SDSA group (n.s.). The median level of pinprick analgesia at 60 min was T11 in the CSA and T6.5 in the SDSA group (P less than 0.01). The mean maximum decreases in CVP and MAP were quite similar in the CSA and SDSA group (2.1 vs 2.8 mmHg (0.3 vs 0.4 kPa) and 17 vs 21 mmHg (2.3 vs 2.8 kPa), respectively) (n.s.). Six patients in the SDSA group and four patients in the CSA group needed sympathomimetic medication. It is concluded that titration of bupivacaine for spinal anaesthesia caused only minor haemodynamic changes which were similar to those after single-dose spinal bupivacaine.