Study of Echocardiographic Measurements to Estimate the Physiological Cardiac Efficiency in Apparently Healthy Patients Visiting University Hospital for Cardiac Evaluation

Background Healthy cardiac function is evaluated by echocardiography in the non-invasive cardiology department. Cardiac functional and structural evaluation is assessed by cardiologists based on a physiologically defined normal range. We want to compute the physiological value of variables in the healthy population. Objective To compute and compare the recorded echocardiographic parameters among apparently healthy patients. Method This is a retrospective study and a total of 544 subjects whose standard reference range was within the normal limit are included for computational study. 268 males (52.8%) and 240 females (47.2%) were studied for the size of the aortic root, size of the left atrium, left ventricular internal diameter during diastole (LVIDd) and systole (LVIDs), interventricular septum during diastole and systole (IVSd and IVSs), left ventricular posterior wall during diastole (LVPWd) and systole (LVPWs) and ejection fraction (EF). Result Ejection fraction (EF) is not significantly different (p=0.14) between genders, Mean±SD; 70.45±6.7 for females and Mean±SD; 68.34±7.18 for males. The mean age of examined female patients is Mean±SD; 36.88±12.6 which is not significantly different with male patients age Mean±SD; 38.28±12.5. Males have larger left ventricular internal diameter in diastole, Mean±SD; 43.90±6.4 than females Mean±SD; 41.37±8.08. Ejection fraction for females is Mean±SD; 70.45±6.7, for males is Mean±SD; 68.34±7.18 with p=0.14. Conclusion Absolute echocardiographic measurements vary physiologically between apparently healthy genders yet the ejection fraction is not significantly different between both the genders in the examined Nepali population.

Skin Conductance and RR Interval for Regulated Discrete Physiological Stimuli: A Two Prong Strategy to Detect Sympathetic Activation

Background Several studies have found skin conductance a good indicator for detection of sympathetic response. But, valid and reliable tool for detection of sympathetic outflow in health and disease is still a quest. Thereby, comparison of superficial and, at core sympathetic effluence induced by deliberately supplied discrete external stimuli has been attempted in this study. Objective To assess the degree of sympathetic outflow for discrete cognitive and physical stimuli through perturbations in skin conductance and variations in heart rate in healthy adults. Method Quantitative and cross-sectional study was performed in 104 healthy subjects following random sampling method. Induction of sympathetic activity was realized by providing separate time bound cognitive exercises intervened with change in posture. Recordings to detect sympathetic responses at rest and, for supplied stimuli were made by electrocardiogram and galvanic skin response. Result Cognitive performance and postural change shifts baseline effluence and increases the sympathetic outflow significantly (p=0.000). There occurs no detectable rise in sympathetic effluence at the core (p=0.362) but, eventuate significantly appreciable sympathetic outflow to sweat glands in skin (p=0.000), when compared cognitive versus physical stimuli. Conclusion Sympathetic outflow induced by cognitive challenge and physical change in posture is readily assessable through sympathetic skin response yet core sympathetic effluence for latter stimuli is steady and unwavering. Differential effluence for sympathetic response called upon by discrete stimuli is operational for maintenance of steady state in healthy subjects.

Galvanic Skin Response as a Simple Physiology Lab Teaching Tool- An Alternative Indicator of Sympathetic Arousal

Background Sympathetic arousal response due to rewarding emotion may not be considered threat to the well-being but such arousal response evoked by fear or punishment can be stressful. When such changes are recorded in lab as biological signals, induced with appropriate stimulus, the observed response may serve as a good indicator of homeostatic alteration. In this study, skin conductance was utilized to record sympathetic response for cognitive load, by application of simple subtraction task. Objective To detect sympathetic arousal by utilization of galvanic skin response during mental arithmetic task. Method Total of eighty two subjects, forty two female and forty male participated in the study. Twenty two subjects were provided mental task to record skin conductance. In sixty subjects, galvanic skin response, pulse rate, respiratory rate and temperature were recorded by appropriate transducers to obtain baseline and task response to detect differential recordings. Subjects performed the mental exercise of arithmetic task (MAT) with transducer placed in upper limbs. Mean of averages for respective variables were statistically calculated from obtained recordings. Result For measured galvanic skin response, 57 subjects showed increased skin conductance (rise in amplitude) whereas, 25 subjects had no rise in amplitude ("A peak") while performing the mental arithmetic task, when compared to control recording. However, in 20 subjects, pulse rate and respiratory rate showed significant rise though, the change in the skin conductance was not significant. Conclusion Galvanic skin response is useful for demonstration of sympathetic activation induced by simple mental subtraction task, and can be utilized along with vital parameters mentioned in this study to discuss in vivo variation that exist as differential for core and superficial sympathetic outflow among individuals.

Thyroid hormone levels in highlanders- a comparison between residents of two altitudes in Nepal

BACKGROUND

The endocrine changes related to altitude adaptation in human have attracted physiologists around the globe for long. A number of high altitude studies to detect the physiological changes have been performed now and then. But, the study to see the hormonal changes to compare populations residing at different high altitudes is a scarce. Hence, we have performed a study in native populations of different high altitude comparing changes in thyroid hormones in western Nepal. The Jharkot population included in this study is at altitude of 3760 m and Jomsom population at 2800 m height from sea bed.

OBJECTIVE

The study is to compare changes in thyroid hormones at two different high altitude natives.

METHODS

To compare thyroid status between high altitude natives at two different altitudes a cross sectional study is performed by random sampling method. The blood sample was collected in a vacutainer from fifty eight individuals after obtaining the informed consent of participants. The blood collected from antecubital vein was centrifuged in an hour and the serum obtained was used for biochemical analysis of free triiodothyronine, free thyroxine and thyroid stimulating hormone.

RESULTS

Mean free thyroxine (fT₄) of Jharkot population is significantly larger (p = 0.001) than Jomsom population. Mean thyroid stimulating hormone (TSH) with p = 0.597, does not indicate the difference between this two population. There is no significant difference between mean free triiodothyronine (fT₃) of Jharkot and Jomsom population (p = 0.345).

CONCLUSION

The rise in free thyroid hormone at high altitude is not dependent on the thyroid stimulating hormone released from anterior pituitary. The rise in free thyroxine is found at higher altitude and no difference in fT₃ level is detected in population studied at high altitudes.

Relationship between arterial oxygen saturation and hematocrit, and effect of slow deep breathing on oxygen saturation in Himalayan high altitude populations

BACKGROUND

The oxygen saturation of haemoglobin is reduced in high altitude-living organisms. Increase in the hematocrit is responsible for rise in the hemoglobin concentration so that the oxygen carrying capacity in the hypobaric hypoxic subject is elevated.

OBJECTIVES

To compare two different high altitude populations, in order to study the relationship between arterial oxygen saturation and hematocrit.

METHODS

In the cross-sectional study of two populations residing at altitude of 2800 m and 3760 m are compared for the difference in hematocrit. The oxygen carrying capacity of arterial haemoglobin (SaO2) is determined by pulse oximetry. The sample is drawn from the natives of two small villages, Thini at Jomsom (2800 m) and Jharkot (3760 m) in Mustang district of Nepal. The natives at 2800 m are termed as lower high altitude population and local residents at 3760 m are said to be higher altitude population in this study. The sample blood was drawn by venipuncture and packed cell volume was determined by Wintrobe's method.

RESULTS

The hematocrit obtained from 3760 m altitude population and the lower high altitude population at altitude of 2800 m differ significantly with the p value < 0.0001and the SaO2 in both the population fails to show any difference with p value > 0.05. Deep breathing exercise in these populations however increased SaO2 significantly.

CONCLUSION

The higher altitude natives have greater arterial oxygen saturation than lower altitude population which is due to rise in red cell concentration. The slow deep breathing raises oxygen saturation irrespective of altitude.

Haemolytic effects of hypo-osmotic salt solutions on human erythrocytes

BACKGROUND

While it is well known that hypotonic solutions of sodium chloride induce hemolysis, the effects of other salt solutions on human erythrocytes have not been well documented.

OBJECTIVE

The study is to compare the effects of other salt solutions on human red cells.

METHODS

Iso-osmotic and hypo-osmotic solutions of various salts were prepared after taking into account their molecular weight and osmotic pressure. Five healthy volunteers between the age of 22-30 years were randomly selected and ten blood samples were collected from them. The study was conducted from January 2009 to February 2009. Blood was collected from subjects by venepuncture into heparinised tubes. 20 fl of blood was pipetted into 1 ml of each solution and incubated for one hour at 37°C in a water bath. The solutions were centrifuged and the colour of the supernatant was read in a spectrophotometer. Supernatant from blood added to distilled water was considered 100% hemolysed.

RESULTS

Iso-osmotic salt solutions were free of hemolysis. Among chloride salts, sodium chloride showed the least hemolysis and potassium chloride and nickel chloride resulted into greater hemolysis. Among potassium salts, potassium bromate caused highest amount of hemolysis whereas potassium sulphate showed the least.

CONCLUSION

The significant differences in hemolytic pattern in hypo-osmotic salts solutions suggest that the hypo-osmotic stress causes morphological changes in red cells that alter their permeability to various ions leading to hemolysis. This probably occurs through opening of volume sensitive channels.