Hypobaric type oxygenators - physics and physiology.

Brain injury is still a serious complication after cardiac surgery. Gaseous microemboli (GME) are known to contribute to both short and longer-term brain injury after cardiac surgery. Hypobaric and novel dual-chamber oxygenators use the physical behaviors and properties of gases to reduce GME. The aim of this review was to present the basic physics of the gases, the mechanism in which the hypobaric and dual-chamber oxygenators reduce GME, their technical performance, the preclinical studies, and future directions. The gas laws are reviewed as an aid to understanding the mechanisms of action of oxygenators. Hypobaric-type oxygenators employ a high oxygen, no nitrogen environment creating a steep concentration gradient of nitrogen out of the blood and into the oxygenator, reducing the risk of GMEs forming. Adequately powered clinical studies have never been carried out with a hypobaric or dual-chamber oxygenator. These are required before such technology can be recommended for widespread clinical use.

Correlation between cardio-ankle vascular index and biomarkers of oxidative stress.

Arterial stiffness is a pathological event related to arteriosclerosis that is also closely related to oxidative stress. The cardio-ankle vascular index (CAVI) is a novel arteriosclerotic index that has been used to detect arterial stiffness. However, the association between CAVI and oxidative stress has not yet been elucidated, especially in patients with risk of metabolic disorders. The aim of this study was to investigate the correlation between arterial stiffness by CAVI and biomarkers of oxidative stress. A total of 83 participants were enrolled in this study. Venous blood samples were collected for measurement of plasma oxidative biomarkers. All participants were examined for CAVI score. The univariate analysis showed that age (p < 0.001), systolic blood pressure (SBP) (p = < 0.001), plasma triglyceride (p = 0.02), plasma glucose (p = 0.003) are related to CAVI value. However, the multivariate analysis showed that age was the only significant independent factor related to the CAVI value. In addition, the CAVI and plasma malondialdehyde (MDA) levels showed a positive correlation (r = 0.29, p < 0.01) while, the CAVI was negatively correlated with catalase (CAT) (r = -0.4, p < 0.001) and GPx (r = -0.60, p < 0.001). In conclusion, this study demonstrated that age is the most influential factor for assessing arterial stiffness by the CAVI method, which is possibly due to the increase in oxidative stress.

Cardiovascular and Ocular Parameter Alterations in Response to Cold Pressor Test in Young Adults.

The sympathetic nervous responses to cold stress are known; however, concurrent cardiovascular and ocular parameter alterations in the responses are poorly characterized. The aim of this study was to examine the influence of the cold pressor test (CPT) on cardiovascular and ocular parameters in young adult subjects. There was a total of 86 participants. The CPT was conducted by submerging each participant's left hand in cold water (3-5 °C) for 3 min. During the CPT, systolic blood pressure, diastolic blood pressure, mean arterial pressure (MAP), and heart rate were found to be significantly increased compared to the baseline and significantly decreased compared to recovery, including the mean of the standard deviations of all normal-to-normal intervals (SDNN). In the recovery phase, the SDNN continued to decrease statistically significantly compared to the baseline and the CPT. Furthermore, the findings of this study show that the CPT impacted intra-ocular pressure (IOP), ACD, and pupil size parameters. There was a positive correlation between the MAP and IOP in both eyes during the CPT. The cold stress stimulates a sympathetic response, leading to an increase in the MAP. The pupil size increased in response to the CPT in both eyes, indicating that ocular function was increased in response to the CPT in young adults compared to baseline. In conclusion, our results suggest that in young adults, cardiovascular and ocular parameters respond to the sympathetic nervous system during the CPT.

Cold Pressor Test Influences the Cardio-Ankle Vascular Index in Healthy Overweight Young Adults.

OBJECTIVE: The cold pressor test (CPT) has been shown a potential sympathoexcitatory stimulus which increases aortic pulse wave velocity and the aortic augmentation index, suggesting that noninvasively, arterial stiffness parameters are altered by the CPT. The cardio-ankle vascular index (CAVI) is widely used for reflecting arterial stiffness, and the ankle-brachial index (ABI) for evaluating peripheral artery disease in obesity. We aimed to assess CAVI and ABI in overweight young adults in the context of sympathetic activation by using the CPT. METHODS: 160 participants were divided into 2 groups: 86 normal-weight (body mass index [BMI] 18.50-22.99 kg/m2) and 74 overweight (BMI ≥23 kg/m2). The CPT was performed by immersing a participant's left hand into cold water (3-5°C) for 3 min, and CAVI and ABI assessment. RESULTS: At baseline, the CAVI in the overweight group was significantly less than that in the normal-weight group (5.79 ± 0.85 vs. 6.10 ± 0.85; p < 0.05). The mean arterial pressure (MAP) for overweight was significantly greater than that for normal-weight subjects (93.89 ± 7.31 vs. 91.10 ± 6.72; p < 0.05). During the CPT, the CAVI increased in both normal-weight and overweight subjects, the CAVI value was greater during the CPT in overweight subjects by 14.36% (6.62 ± 0.95 vs. 5.79 ± 0.85, p < 0.05) and in normal-weight subjects by 8.03% (6.59 ± 1.20 vs. 6.10 ± 0.85, p < 0.05) than those baseline values. The CPT evoked an increase in systolic blood pressure (SBP), diastolic BP (DBP), heart rate (HR,) and pulse pressure (PP) in both groups. After a 4-min CPT period, the CAVI returned values similar to the baseline values in both groups, and the SBP, DBP, MAP, and PP in overweight participants were significantly higher than those in normal-weight participants. However, there was no significant difference in the ABI at baseline, during CPT, and post-CPT in either group. CONCLUSIONS: Our results indicated that the CAVI was influenced by sympathetic activation response to the CPT in both normal-weight and overweight young adults. Specifically, during the CPT, the percentage change of the CAVI in overweight response was greater in normal-weight participants than baseline values in each group. The ABI was not found significantly associated with CPT. These findings suggesting that sympathoexcitatory stimulus by CPT influence CAVI results.

Correlation between body mass index and ocular parameters.

Purpose: To investigate the relationship between BMI and selected ocular parameters. Subjects and methods: Fifty-three left eyes of normal weight subjects and 67 age-sex matched overweight subjects were studied. Inclusion criteria for the normal weight and overweight groups included BMI between 18.5-22.9 and 23.0-29.9 kg/m2, respectively. Subjects with a history of systemic disease, ocular disease or surgery, or disability were excluded. All subjects underwent a medical history interview, arterial blood pressure, height, weight, waist circumference and hip circumference measurements, and BMI and waist-hip ratio calculation. The intraocular pressure (IOP) and anterior corneal curvature were measured by non-contact tonometry and corneal topography, respectively. Measurement of anterior and posterior segment parameters of the eye, including central corneal thickness, anterior chamber depth (ACD), anterior chamber angle, macular thickness (MT), ganglion cell thickness (GCT), retinal nerve fiber layer thickness, cup to disc ratio, and choroidal thickness was performed by enhanced depth-imaging optical coherence tomography. Results: There was a positive correlation between ACD and BMI (Univariate analysis; ß =0.198, P=0.030, Multivariate analysis; ß =0.410, P=0.005) and between BMI and IOP (Univariate analysis; ß =0.269, P=0.003). The IOP of the overweight group was found to be significantly higher than of the normal weight group (12.80±3.40 and 11.86±2.12 mm Hg, respectively, P=0.002). Also, there was a significant difference found between the GCT and the MT of the two groups (P=0.036 and 0.009, respectively). Conclusion: It was found that BMI strongly correlated with ACD and IOP. Also, the degree of obesity was found to be a significant factor; therefore, the relationship between these ocular parameters and the severity of obesity should be further investigated.