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Biomedical subjects

Chun Zhan

Publications and source records attributed to Chun Zhan.

9 recordsLinked to original sources
PubMed2006

Multiple parameter vector bending and high-temperature sensors based on asymmetric multimode fiber Bragg gratings inscribed by an infrared femtosecond laser.

We present a multiple parameter integrated fiber sensor that can detect vector bending and ambient temperature simultaneously with a single asymmetric multimode fiber Bragg grating. Multimode Bragg gratings were fabricated in an all-silica core fiber by an infrared femtosecond laser, which showed multiple transmission dips in the transmission spectrum. Bending and ambient temperature fluctuations affect the shapes of multiple transmission dips in different ways. In bending, different dips have different sensitivities. On the other hand, temperature fluctuations tended to influence the dips uniformly across different dips. By analyzing the changing spectrum of dips, one can distinguish the changes induced by bending or temperature fluctuations. Furthermore, the high thermal stability of Bragg gratings inscribed by an infrared femtosecond laser can make this double parameter fiber sensor work in very harsh, high-temperature environments.

Journal Article↗
PubMed2006

Protective effects of isoliquiritigenin in transient middle cerebral artery occlusion-induced focal cerebral ischemia in rats.

Epidemiological studies indicate that the intake of flavonoids is inversely associated with risk of stroke, cardiovascular diseases and cancer. Isoliquiritigenin (ISL), a flavonoid constituent in the root of Glycyrrhiza glabra, is known to have vasorelaxant effect, antioxidant, anti-platelet, anti-tumor, anti-allergic, antiviral activities and estrogenic properties. However, there is no report on the effects of ISL in cerebral ischemia. Evidence demonstrate that the impaired energy metabolism and the excessive generation of reactive oxygen radicals (ROS) contribute to the brain injury associated with cerebral ischemia. In the present study, the protective effects of ISL were investigated in transient middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia-reperfusion injury in rats. Male Sprague-Dawley rats were divided into five groups: sham-operated group, vehicle-pretreated group, and three ISL-pretreated groups (5, 10 and 20 mg kg(-1), i.g.). ISL were administered once a day, for 7 days prior to ischemia. The rats were subjected to 2 h right MCAO via the intraluminal filament technique and 22 h reperfusion. Pretreatment with ISL significantly reduced the cerebral infarct volume and edema and produced significant reduction in neurological deficits. In this study, in order to clarify the mechanism of ISL's protection against cerebral ischemia damage, cerebral energy metabolism, brain Na+K+ATPase activity, malondialdehyde (MDA) content and antioxidant enzyme activities were measured. ISL pretreatment increased the brain ATP content, energy charge (EC) and total adenine nucleotides (TAN) in a dose-dependent manner. The brain Na+K+ATPase activity was protected significantly by pretreatment of ISL for 7 days. Pretreatment with ISL significantly inhibited the increases of brain MDA content and prevented the activities of brain superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) from declines caused by cerebral ischemia-reperfusion. All these findings indicate that ISL has the protective potential against cerebral ischemia injury and its protective effects may be due to the amelioration of cerebral energy metabolism and its antioxidant property.

Adenine Nucleotides↗
PubMed2006

[Clinical study of mechanical ventilation in acute cardiogenic pulmonary edema patients].

OBJECTIVE: To study the application of mechanical ventilation in acute cardiogenic pulmonary edema (ACPE), and compare the changes in hemodynamics between continuous positive airway pressure proportional pressure support (CPAP-PPS) with continuous positive airway pressure-pressure support ventilation (CPAP-PSV). METHODS: Non-invasive and invasive ventilation were performed in 77 ACPE patients. At the initiation of invasive ventilation and the phase of low assist ventilation in 61 patients who were treated with mechanical ventilation longer than 24 hours, hemodynamics was monitored by partial CO(2) rebreathing method (non-invasive cardiac output, NICO) cardiopulmonary management system, and then compared the changes in the two kinds of ventilation under medicinal intervention. RESULTS: Among 33 of 61 ACPE patients underwent non-invasive ventilation, 24 were successful, and the ratio was 72.7%. Among 33 patients with invasive ventilation (including 5 in whom ventilation was switched to non-invasive mode), 11 failed. Biphasic positive airway pressure/pressure support ventilation (BIPAP/PSV) was used in pressure controlled ventilation, with high pressure (Phigh) 16-24 cm H(2)O (1 cm H(2)O=0.098 kPa), time of high pressure (Thigh) 1.5 seconds, positive end expiratory pressure (PEEP) 6-15 cm H(2)O, fractional concentration of inspired oxygen (FiO(2)) 0.5, cardiac output (CO)/cardiac index (CI) was significantly improved compared with those of initial ventilation in successful ones in invasive group, and the improvement was more significant in PPS compared with PSV in low assist ventilation (all P<0.001). Those in whom invasive ventilation was failed had a low CI (<1.5 L.min(-1).m(-2)) even under drug intervention. CONCLUSION: Hemodynamic monitoring should be performed when medicinal intervention and non-invasive/invasive ventilation are given to ACPE patients. Pressure controlled ventilation is recommended, and PEEP should be individualized (normally 6-15 cm H(2)O). Spontaneous ventilation should be restored as soon as possible, CPAP-PPS mode is practicable in patients in whom weaning of mechanical ventilation is difficult.

Acute Disease↗
PubMed2006

[Study of continuous hemodynamics monitoring techniques in patients with mechanical ventilation].

OBJECTIVE: To elucidate the relativity among three kinds of continuous hemodynamics monitoring techniques: thermodilution via Swan-Ganz catheter, pulse contour analysis method (PiCCO), partial CO(2) rebreathing method (non invasive cardiac output, NICO), in patients with mechanical ventilation. METHODS: In 13 patients with respiratory failure due to different causes, hemodynamics were continuously monitored with Swan-Ganz catheterization, PiCCO, NICO simultaneously. The therapeutic measures and the type of ventilator were similar. Data were collected at the same time points to compare the relativity among these three kinds of monitor. RESULTS: Linear relative analysis showed a good relativity in PiCCO/Swan-Ganz (r=0.883), NICO/Swan-Ganz (r=0.853) and PiCCO/NICO (r=0.857) in cardiac index (CI). CONCLUSION: PiCCO and NICO can be used as reliable measure to monitor ventilated patients bedside in intensive care unit (ICU), thus offering an assistance to optimize therapeutic strategy.

Aged↗
PubMed2006

[Effect on hemodynamics during different modes of low assist ventilation].

OBJECTIVE: To observe the effect on mechanical ventilation with biphasic positive airway pressure (BIPAP), pressure support ventilation (PSV) and proportional pressure support (PPS) modes on hemodynamics in patients with either normal cardiac function or impaired cardiac function in order to optimize the time to wean mechanical ventilation in patients with severe cardiac dysfunction. METHODS: Non-invasive cardiac output (NICO) monitoring was instituted in patients 32 with respiratory failure due to different causes, when spontaneous respiration was restored, and they were separated into two groups depending on whether the cardiac index (CI) was normal (CI> or =2.0 L.min(-1).m(-2)) or not (CI<2.0 L.min(-1).m(-2)). The effects of BIPAP, PSV and PPS modes on changes in hemodynamics were compared between two groups. RESULTS: (1) In patients with normal cardiac function, CO, CI, stroke volume (SV), pulmonary capillary blood flow (PCBF) were significant higher in PSV and PPS modes than BIPAP mode, and they were highest with PPS mode, but no significant difference compared with PSV. Surround vascular resistance (SVR) was reduced significantly in PPS mode compared with BIPAP, but no significant difference was found compared with PSV. (2) In patients with cardiac dysfunction, CO, CI increased gradually when ventilated in BIPAP, PSV, PPS modes and significant difference was found among three groups. In PPS mode, CO and CI were highest. (3) The trends of peak airway pressure (Ppeak) and mean airway pressure (Pmean) were degressive in three groups. In both normal cardiac function group and cardiac dysfunction group, significant difference was found in PSV and PPS modes compared with BIPAP. Ppeak was lowest in PPS mode in cardiac dysfunction group, and there was significant difference compared with the other groups. (4) The ventilated time was significant reduced in PPS mode compared with PSV. (5) In normal cardiac function group, instinct positive end expiratory pressure (PEEPi) showed degressive trend among three different modes, and it was lowest in PPS mode, with significant difference compared with the other two groups. CONCLUSION: In PPS mode, the effect to hemodynamics in patients with severe cardiac dysfunction is minimal, so it is suitable as a weaning mode in this groups of patients.

Adult↗
PubMed2004

Measuring single cardiac myocyte contractile force via moving a magnetic bead.

One of the biggest problems of heart failure is the heart's inability to effectively pump blood to meet the body's demands, which may be caused by disease-induced alterations in contraction properties (such as contractile force and Young's modulus). Thus, it is very important to measure contractile properties at single cardiac myocyte level that can lay the foundation for quantitatively understanding the mechanism of heart failure and understanding molecular alterations in diseased heart cells. In this article, we report a novel single cardiac myocyte contractile force measurement technique based on moving a magnetic bead. The measuring system is mainly composed of 1), a high-power inverted microscope with video output and edge detection; and 2), a moving magnetic bead based magnetic force loading module. The main measurement procedures are as follows: 1), record maximal displacement of single cardiac myocyte during contraction; 2), attach a magnetic bead on one end of the myocyte that will move with myocyte during the contraction; 3), repeat step 1 and record contraction processes under different magnitudes of magnetic force loading by adjusting the magnetic field applied on the magnetic bead; and 4), derive the myocyte contractile force base on the maximal displacement of cell contraction and magnetic loading force. The major advantages of this unique approach are: 1), measuring the force without direct connections to the cell specimen (i.e., "remote sensing", a noninvasive/minimally invasive approach); 2), high sensitivity and large dynamic range (force measurement range: from pico Newton to micro Newton); 3), a convenient and cost-effective approach; and 4), more importantly, it can be used to study the contractile properties of heart cells under different levels of external loading forces by adjusting the magnitude of applied magnetic field, which is very important for studying disease induced alterations in contraction properties. Experimental results demonstrated the feasibility of proposed approach.

Animals↗
PubMed2004

[Adjustment methods of proportional pressure support on weaning during acute aggravation in chronic respiratory failure patients with chronic obstructive pulmonary disease].

OBJECTIVE: To study the effects of two adjustment methods of proportional pressure support (PPS) on patients with acute aggravation in chronic respiratory failure of chronic obstructive pulmonary disease. METHODS: Seventy-five patients were randomized to two groups, 30 in proportional adjustment group and 45 in target adjustment group, respectively. Suitable flow assist (FA) and volume assist (VA) were adjusted with proportional adjustment and target adjustment methods respectively according to the ventilation parameters until the weaning of ventilation. RESULTS: There were no significant differences in resistance, elastic, FA as well as VA on weaning point, duration of mechanical ventilation, and successful weaning rate between the two groups (all P>0.05). CONCLUSION: The same aim and successful weaning rate could be gained in the target adjustment group compared with the proportional adjustment group. More clinical experience and more intensive care would be needed in the target adjustment group.

Female↗