Measurement of blood pressure in rats: Invasive or noninvasive methods?

Experiments should always be based on control values. This assumption fully applies to cardiovascular parameters, such as heart rate (HR) and blood pressure (BP), which are highly sensitive to various external and internal stimuli and can already be significantly altered when an experiment begins. Therefore, it is necessary to determine which values are defined as a starting point (i.e., control and baseline) or compare them with valid reference values if the goal is to evaluate the changes after experimental intervention. A generally accepted principle is a reciprocal relationship between BP and HR, in which one parameter affects the other and vice versa. BP can be measured using two methods-noninvasively (tail-cuff) and invasively (telemetry, direct measurements of BP after introducing the sensor directly into the artery), and HR directly or by extrapolation from BP recordings. This study does not aim to evaluate the results of individual studies, but to review whether there are differences in control (baseline) BP values in normotensive and hypertensive male rats using invasive versus noninvasive methods, and to investigate whether there is a causal relationship between BP and HR in in vivo experiments with male rats.

Heart rate variability in male rats.

The cardiovascular system is primarily controlled by the autonomic nervous system, and any changes in sympathetic or parasympathetic activity also have an impact on myocardial activity. Heart rate variability (HRV) is a readily available metric used to assess heart rate control by the autonomic nervous system. HRV can provide information about neural (parasympathetic, sympathetic, reflex) and humoral (hormones, thermoregulation) control of myocardial activity. Because there are no relevant reference values for HRV parameters in rats in the scientific literature, all experimental results are only interpreted on the basis of changes from currently measured control or baseline HRV values, which are, however, significantly different in individual studies. Considering the significant variability of published HRV data, the present study focused primarily on comparing control or baseline HRV values under different conditions in in vivo experiments involving rats. The aim of the study was therefore to assess whether there are differences in the starting values before the experiment itself.

Sex differences, chronobiology and general anaesthesia in activities of the autonomic nervous system in rats.

NEW FINDINGS: What is the topic of this review? Changes in heart rate variability in rats with sex differences and the use of different anaesthesia during light-dark cycles. What advances does it highlight? The review highlights and discusses synthesized current results in order to advance knowledge and understanding of sex differences with an emphasis on changes in the autonomic nervous system determined by heart rate variability. ABSTRACT: Heart rate variability (HRV) is commonly used in experimental studies to assess sympathetic and parasympathetic activities. The belief that HRV in rodents reflects similar cardiovascular regulations in humans is supported by evidence, and HRV in rats appears to be at least analogous to that in humans, although the degree of influence of the parasympathetic division of the autonomic nervous system (ANS) may be greater in rats than in humans. Experimental studies are based on control or baseline values, on the basis of which the change in ANS activity after a given experimental intervention is assessed, but it is known that the ANS in rats is very sensitive to various stress interventions, such as the manipulation itself, and ANS activity can also differ depending on sex, the time of measurement, and whether the animals are under general anaesthesia. Thus, for correct assessment, changes in ANS activity and their relationship to the observed parameter should be based on whether ANS activity does or does not change but also to what extent the activity is already changed at the start of the experiment. Since rats are considered to be the most suitable model animal for basic cardiovascular research, in this review we point out existing differences in individual HRV frequency parameters at the start of experiments (control, baseline values), taking into account sex in relation to time of measurement and anaesthesia.

Glycaemic Variability and Risk Factors of Pregnant Women with and without Gestational Diabetes Mellitus Measured by Continuous Glucose Monitoring.

Background: The aim of the study was to compare the continuous glucose monitoring (CGM)-determined glycaemic variability (GV) of pregnant women with gestational diabetes mellitus (GDM) and without GDM (CG; control group). The secondary aim was to evaluate the association between risk factors of diabetes in pregnancy and parameters of glyceamic control. Methods: Demographic, biometric and biochemical parameters were obtained for pregnant women (20-38 years old) who after an oral glucose tolerance test were examined by 7-day continuous glucose monitoring using a iPro®2 Professional CGM. Results: The differences in GV between women with GDM and CG compared by total area under glucose curve (total AUC, (mmol·day/L) was statistically significant (p = 0.006). Other parameters of glycaemic control such as mean glucose, standard deviation, coefficient of variation, J-index, % time-above target range 7.8 mmol/L (%TAR), % time-in range 3.5-7.8 mmol/L (%TIR), time-below target range 3.5 mmol/L (%TBR), glycated haemoglobin were not significantly different in the study groups. Risk factors (a family history of diabetes, pre-pregnancy BMI, higher weight gain and age) correlated with parameters of glycaemic control. Conclusions: We found a significant difference in GV of women with and without GDM by total AUC determined from CGM. TIR metrics were close to significance. Our work points at an increased GV in relation to the risk factors of GDM. Pregnant women with risk factors have higher probability of severe GV with its consequences on maternal and fetal health state.

EU questionnaire to screen for obstructive sleep apnoea validated in Slovakia.

OBJECTIVE: Obstructive sleep apnoea syndrome (OSAS) associated with daytime sleepiness (DS) contributes to a higher incidence of motor vehicle accidents. Validation of fitness to drive in driving license applicants, with special concern regarding OSAS accompanied by excessive DS, became mandatory under new EU legislation in January 2016. The aim of the study was to translate and validate the recommended questionnaire to screen for OSAS (Q-OSAS) in the Slovak population. No data on any Q-OSAS validation has previously been published. METHODS: The translated Q-OSAS was administered to 311 Slovak patients prior to a planned overnight polysomnography. The diagnostic accuracy of the Q-OSAS in OSAS with an apnoea-hypopnoea index of 15 or more/h of sleep was evaluated by calculating the area under the ROC curve. RESULTS: The sensitivity and specificity of the cut-off at 10 points for the Q-OSAS was 57% and 67%, respectively, with an increase of sensitivity and a decrease of specificity with a lowering of the cut-off values. Excluding the Epworth Sleepiness Scale (ESS) score from the final statistics yielded the best sensitivity (77%), specificity (50%), and an area under the ROC curve (0.637) for the cut-off value of 8 points (an equivalent of 10 points with the full version of the Q-OSAS). CONCLUSION: The Q-OSAS is an appropriate screening tool to facilitate the screening of subjects potentially at risk from moderate and severe OSAS. A modified two-step interpretation of the Q-OSAS in Slovakia yielded the best sensitivity, and in the future could promote evaluation of sleepiness in sleep and wake disorders other than OSAS for fitness to drive.

Resuscitation and auto resuscitation by airway reflexes in animals.

Various diseases often result in decompensation requiring resuscitation. In infants moderate hypoxia evokes a compensatory augmented breath - sigh and more severe hypoxia results in a solitary gasp. Progressive asphyxia provokes gasping respiration saving the healthy infant - autoresuscitation by gasping. A neonate with sudden infant death syndrome, however, usually will not survive. Our systematic research in animals indicated that airway reflexes have similar resuscitation potential as gasping respiration. Nasopharyngeal stimulation in cats and most mammals evokes the aspiration reflex, characterized by spasmodic inspiration followed by passive expiration. On the contrary, expiration reflex from the larynx, or cough reflex from the pharynx and lower airways manifest by a forced expiration, which in cough is preceded by deep inspiration. These reflexes of distinct character activate the brainstem rhythm generators for inspiration and expiration strongly, but differently. They secondarily modulate the control mechanisms of various vital functions of the organism. During severe asphyxia the progressive respiratory insufficiency may induce a life-threatening cardio-respiratory failure. The sniff- and gasp-like aspiration reflex and similar spasmodic inspirations, accompanied by strong sympatho-adrenergic activation, can interrupt a severe asphyxia and reverse the developing dangerous cardiovascular and vasomotor dysfunctions, threatening with imminent loss of consciousness and death. During progressive asphyxia the reversal of gradually developing bradycardia and excessive hypotension by airway reflexes starts with reflex tachycardia and vasoconstriction, resulting in prompt hypertensive reaction, followed by renewal of cortical activity and gradual normalization of breathing. A combination of the aspiration reflex supporting venous return and the expiration or cough reflex increasing the cerebral perfusion by strong expirations, provides a powerful resuscitation and autoresuscitation potential, proved in animal experiments. They represent a simple but unique model tested in animal experiments.

Reversal of functional disorders by aspiration, expiration, and cough reflexes and their voluntary counterparts.

Agonal gasping provoked by asphyxia can save ~15% of mammals even from untreated ventricular fibrillation (VF), but it fails to revive infants with sudden infant death syndrome (SIDS). Our systematic study of airway reflexes in cats and other animals indicated that in addition to cough, there are two distinct airway reflexes that may contribute to auto-resuscitation. Gasp- and sniff-like spasmodic inspirations (SIs) can be elicited by nasopharyngeal stimulation, strongly activating the brainstem generator for inspiration, which is also involved in the control of gasping. This "aspiration reflex" (AspR) is characterized by SI without subsequent active expiration and can be elicited during agonal gasping, caused by brainstem trans-sections in cats. Stimulation of the larynx can activate the generator for expiration to evoke the expiration reflex (ExpR), manifesting with prompt expiration without preceding inspiration. Stimulation of the oropharynx and lower airways provokes the cough reflex (CR) which results from activating of both generators. The powerful potential of the AspR resembling auto-resuscitation by gasping can influence the control mechanisms of vital functions, mediating reversal of various functional disorders. The AspR in cats interrupted hypoxic apnea, laryngo- and bronchospasm, apneusis and even transient asphyxic coma, and can normalize various hypo- and hyper-functional disorders. Introduction of a nasogastric catheter evoked similar SIs in premature infants and interrupted hiccough attacks in adults. Coughing on demand can prevent anaphylactic shock and resuscitate the pertinent subject. Sniff representing nasal inspiratory pressure and maximal inspiratory and expiratory pressures (MIP and MEP) are voluntary counterparts of airway reflexes, and are useful for diagnosis and therapy of various cardio-respiratory and neuromuscular disorders.

Do differences in sleep architecture exist between persons with type 2 diabetes and nondiabetic controls?

BACKGROUND: It has been shown previously that the suppression of slow-wave sleep (SWS) markedly reduced insulin sensitivity and led to an impairment of glucose tolerance. We hypothesized that a decreased amount of SWS is a feature peculiar to subjects with type 2 diabetes. METHOD: A retrospective case-control study analyzed polysomnographic recordings and covariate data of 22 type 2 diabetic and 22 nondiabetic subjects [n = 44; 8 women, 36 men, aged 57.5 +/- 5.5 years, body mass index (BMI) 33.8 +/- 5.9 kg/m(2), apnea-hypopnea index (AHI) 29.6 +/- 22.2 episodes/hr] matched individually for sex, race, age, BMI, and severity of sleep-related breathing disorders (SRBD). We assessed differences in sleep architecture between the study group and the control group. Primary end points included the percentage of total sleep time spent in each sleep stage. RESULTS: Despite similar age and severity of SRBD, subjects with type 2 diabetes demonstrated a significantly decreased amount of SWS (3.9 +/- 5.95% vs 8.4 +/- 4.57%; p = 0.012), increased percentage time in rapid eye movement sleep (24.1 +/- 12.14% vs 13.8 +/- 6.96%; p = 0.005), and higher arousal index (44.3 +/- 19.53/hr vs 35.7 +/- 12.67/hr; p = 0.037) compared to nondiabetic controls. After adjustment for sex, BMI, AHI, and smoking, age and presence of type 2 diabetes were independent predictors of the decreased SWS percentage (p = 0.001). Variables in this model accounted for 34% of the variance in the SWS percentage in our cohort. CONCLUSIONS: Results demonstrated distinct differences in sleep architecture in our cohort with decreased amounts of SWS in type 2 diabetes. These findings suggest that polysomnographic recognition of altered sleep architecture may be partially implicated in the early detection of persons with type 2 diabetes.