Numerical and experimental study of capillary-driven flow of PCR solution in hybrid hydrophobic microfluidic networks.

Capillary-driven microfluidics is essential for development of point-of-care diagnostic micro-devices. Polymerase chain reaction (PCR)-based micro-devices are widely developed and used in such point-of-care settings. It is imperative to characterize the fluid parameters of PCR solution for designing efficient capillary-driven microfluidic networks. Generally, for numeric modelling, the fluid parameters of PCR solution are approximated to that of water. This procedure leads to inaccurate results, which are discrepant to experimental data. This paper describes mathematical modeling and experimental validation of capillary-driven flow inside Poly-(dimethyl) siloxane (PDMS)-glass hybrid micro-channels. Using experimentally measured PCR fluid parameters, the capillary meniscus displacement in PDMS-glass microfluidic ladder network is simulated using computational fluid dynamic (CFD), and experimentally verified to match with the simulated data.

Effectiveness of microbubble removal in an airtrap with a free surface interface.

An end stage renal disease patient will undergo haemodialysis (HD) three or four times a week for four to five hours per session. Because of the chronic nature of the treatment, any minor imperfection in the extracorporeal system may become significant over time. Clinical studies have raised concerns relating to small microbubbles entering HD patients. These bubbles lead to further pathophysiological complications with the size of the bubble being a major factor. Microbubbles of different sizes can be generated throughout the extra-corporeal HD circuit. It is important to understand the possibility of these bubbles passing through the air trap or successfully being removed which indicates the performance of the air trap, the only mechanics of removing air bubbles. Chronic exposure to various sizes of microbubbles was analysed in detail for haemodialysis patients. However, smaller microbubbles are shown to be able to pass our modelled air trap. While studies have reported the presence of bubbles before and after the air trap, because these bubbles are only counted and not tracked, the performance of the air trap for removing different bubble sizes is not understood. Here, the performance of the air trap in filtering bubbles and the possibility of different bubble sizes passing through the air trap with the presence of the free surface interface have been evaluated. The modelled air trap is shown to be ineffective for filtering small micro bubbles.

Pulsatility Produced by the Hemodialysis Roller Pump as Measured by Doppler Ultrasound.

Microbubbles have previously been detected in the hemodialysis extracorporeal circuit and can enter the blood vessel leading to potential complications. A potential source of these microbubbles is highly pulsatile flow resulting in cavitation. This study quantified the pulsatility produced by the roller pump throughout the extracorporeal circuit. A Sonosite S-series ultrasound probe (FUJIFILM Sonosite Inc., Tokyo, Japan) was used on a single patient during normal hemodialysis treatment. The Doppler waveform showed highly pulsatile flow throughout the circuit with the greatest pulse occurring after the pump itself. The velocity pulse after the pump ranged from 57.6 ± 1.74 cm/s to -72 ± 4.13 cm/s. Flow reversal occurred when contact between the forward roller and tubing ended. The amplitude of the pulse was reduced from 129.6 cm/s to 16.25 cm/s and 6.87 cm/s following the dialyzer and venous air trap. This resulted in almost nonpulsatile, continuous flow returning to the patient through the venous needle. These results indicate that the roller pump may be a source of microbubble formation from cavitation due to the highly pulsatile blood flow. The venous air trap was identified as the most effective mechanism in reducing the pulsatility. The inclusion of multiple rollers is also recommended to offer an effective solution in dampening the pulse produced by the pump.

Two-dimensional computational analysis of microbubbles in hemodialysis.

On average, an end-stage renal disease patient will undergo hemodialysis (HD) three or four times a week for 4-5 h per session. Any minor imperfection in the extracorporeal system may become significant in the treatment of these patients due to the cumulative exposure time. Recently, air traps (a safety feature of dialysis systems) have been reported to be inadequate in detecting microbubbles and may even create them. Microbubbles have been linked to lung injuries and damage to the brain in chronic HD patients; therefore the significance of microbubbles has been revisited. Bubbles may originate at the vascular access sites, sites of local turbulent blood flow, the air trap, or in the bloodlines after priming with saline prior to use. In this paper, computational fluid dynamics is used to model blood flow in the air trap to determine the likely mechanisms of microbubble dynamics. The results indicate that almost all bubbles with diameters less than 50 µm and most of the bubbles of 50-200 µm pass through the air trap. Consequently, the common air traps are not effective in removing bubbles less than 200 µm in diameter.

Intravitreal bevacizumab with or without triamcinolone for refractory diabetic macular edema; a placebo-controlled, randomized clinical trial.

PURPOSE: To evaluate the effect of three intravitreal injections of bevacizumab (IVB) alone or combined with triamcinolone (IVT) in the first injection for treatment of refractory diabetic macular edema (DME). METHODS: In this prospective, placebo-controlled, randomized clinical trial, 115 eyes of 101 patients with refractory DME were included. Subjects were randomly assigned to one of the three study arms: 1) three injections of IVB (1.25 mg/0.05 ml) at 6-week intervals, 2) combined IVB and IVT (1.25 mg/0.05 ml and 2 mg/0.05 ml respectively) followed by two injections of IVB at 6-week intervals, and 3) sham injection (control group). The primary outcome measure was change in central macular thickness (CMT). Secondary outcome measures were change in best-corrected logMAR visual acuity (BCVA ) and incidence of potential adverse events. RESULTS: Central macular thickness was reduced significantly in both the IVB and IVB/IVT groups. At week 24, CMT change compared to the baseline was -95.7 microm (95% CI, -172.2 to -19.26) in the IVB group, -92.1 microm (95% CI, -154.4 to -29.7) in the IVB/IVT group, and 34.9 microm (95% CI, 7.9 to 61.9) in the control group. There was a significant difference between the IVB and control groups (P = 0.012) and between the IVB/IVT and control groups (P = 0.022). Improvement of BCVA was initiated at weeks 6 and 12 in the IVB/IVT and IVB groups respectively. In terms of BCVA change compared to the baseline at 24 weeks, the differences between the IVB and control groups (P = 0.01) and also between the IVB/IVT and control groups (P = 0.006) were significant. No significant differences were detected in the changes of CMT and BCVA between the IVB and IVB/IVT groups (P = 0.99). Anterior chamber reaction was noticed in eight (19.5%) and seven (18.9%) eyes respectively in the IVB and IVB/IVT groups the day after injection, and it resolved with no sequel. Elevation of IOP occurred in three eyes (8.1%) in the IVB/IVT group. CONCLUSION: Three consecutive intravitreal injections of bevacizumab had a beneficial effect on refractory DME in terms of CMT reduction and BCVA improvement. Addition of triamcinolone in the first injection seemed to induce earlier visual improvement; however, it did not show any significant additive effect later during follow-up.

Hyperprolactinemia after laparoscopic ovarian drilling: an unknown phenomenon.

BACKGROUND: The effects of ovarian drilling on the serum levels of gonadotropins and androgens have been studied previously. The aim of this study is to evaluate the effects of ovarian drilling on the serum prolactin levels and its relation to ovulation in women with polycystic ovary syndrome. METHODS: This is a prospective controlled study. Thirty-six women with PCOS underwent ovarian electrocauterization in university hospitals. Control group consisted of 35 ovulatory women with unexplained infertility. Hormonal assessment performed in early follicular phase of spontaneous or induced cycle before operation in the two groups and repeated one week after operation. Hormonal assay was also performed in the early follicular phase of the first post-operative menstruation, folliculometry and progesterone assay were also performed in the same cycle. Data were analyzed by "repeated measurement design, discriminant analysis, correlation coefficient, and Fisher exact test". RESULTS: Six to ten weeks after operation the serum mean +/- SD prolactin levels increased from 284.41 +/- 114.32 mIU/ml to 354.06 +/- 204.42 mIU/ml (P = 0.011). The same values for the control group were 277.73 +/- 114.65 to 277.4 +/- 111.4 (P = 0.981) respectively. Approximately 45% of subjects in PCOS group remained anovulatory in spite of decreased level of LH and testosterone. Prolactin level remained elevated in 73.2% of women who did not ovulate 6-10 weeks after the procedure. CONCLUSION: Hyperprolactinemia after ovarian cauterization may be considered as a possible cause of anovulation in women with polycystic ovaries and improved gonadotropin and androgen levels. The cause of hyperprolactinemia is unknown. Hormonal assay particularly PRL in anovulatory patients after ovarian cauterization is recommended.