Efectos beneficiosos de la respiración manejada a voluntad sobre la frecuencia cardíaca y temperatura periférica / Beneficial effects of controlled breathing on cardiac frecuency and peripheral temperature

Este estudio trató de mostrar los efectos que tenía la respiración manejada a voluntad en forma de inspiraciones cortas y espiraciones largas. El estudio se realizó con 14 sujetos, empleando 8 sesiones de tratamiento. Los resultados mostraron diferencias significativas en el descenso de la frecuencia cardíaca y en el aumento de la temperatura periférica a la finalización del tratamiento, en relación con los valores previos al tratamiento (AU)

Efecto del diámetro interno del tubo endotraqueal sobre el consumo de oxígeno durante la respiración espontánea / Effect of the inner diameter of the endotracheal tube on oxygen consumption during spontaneous respiration

Objetivo. Valorar, en pacientes con respiración espontánea, el efecto de la reducción simulada del diámetro interno del tubo endotraqueal (TET) desde 8 a 7 mm sobre el consumo de oxígeno (V.O2) y la frecuencia respiratoria. Métodos. Durante la desconexión de la ventilación mecánica, en doce pacientes que mantenían una correcta respiración espontánea a través de un TET, medimos el V.O2 y la producción de CO2 (V.CO2) en dos ocasiones, una con un TET de 8 mm de diámetro interno ( ) y otra con un conector de un TET de 6 mm de , que simula la resistencia al flujo de aire de un TET de 7 mm de . Medimos el V.O2 y la V.CO2 con el método del circuito abierto mediante un espirómetro Wright y un analizador de gases IL-1312 (Izasa, España). Se ha utilizado la prueba de la "t" de Student para datos pareados. Se consideró significativo un valor de p < 0,05.Resultados. La reducción del del TET de 8 a 7 mm se acompañó de un incremento en el V.O2 de 8 (DE 13) ml/min (límites de -12 a 27 ml/min, 95 por ciento IC de -1 a 16 ml/min; p = 0,07) y en la V.CO2 de 9 (DE 8) ml/min (límites de -6 a 16 ml/min, 95 por ciento IC de 4 a 14 ml/min; p = 0,002). La frecuencia respiratoria disminuyó de 26 a 25 rpm (p = 0,07). Conclusión. Durante la desconexión de la ventilación mecánica, en pacientes con buena tolerancia a la respiración espontánea en "tubo en T", la reducción del diámetro interno del tubo endotraqueal de 8 a 7 mm no modifica el consumo de O2, ni la frecuencia respiratoria, de forma clínicamente relevante. (AU)

Venipuncture in the medical physiology laboratory.

Medical physiology laboratories, traditionally devoted to animal experimentation, face unprecedented difficulties linked to cost, staffing, instrumentation, and the use of animals. At the same time, laboratory experiences with living creatures play a unique role in medical education. In this article we describe the use of venipuncture and subsequent blood analysis, with medical students serving as both subjects and experimenters, in a sequence of first-year physiology laboratories. These experiments are safe, robust, inexpensive, and time efficient, and they teach the principles of cardiovascular, respiratory, renal, nutritional, and gastrointestinal physiology. In addition, they enhance medical education in several other important dimensions. First, they teach safe venous blood collection and handling, a training appropriate for students at this level. Second, by serving each week as subjects as well as experimenters, students experience aspects of both sides of the doctor-patient relationship. Third, the laboratories can be used to teach fundamentals of research design and analysis. Finally, because blood analysis is central to medicine, and because the student's own blood data are discussed, students are enthusiastic and cooperative, and the clinical relevance of the data is clear.

Students' misconceptions about perceived physiological responses.

Students' misconceptions about scientific phenomena can arise from at least two possible sources, the students' personal experience with those phenomena and things learned in the classroom. Misconceptions have been studied in a variety of science disciplines, but little attention has been given to the faulty models that students have for physiological processes. In this study 393 undergraduates in three different research universities were asked to predict the changes in heart rate and strength of cardiac contraction and breathing frequency and depth of breathing (physiological parameters that can be directly and personally perceived) under conditions that result in predicted that heart rate would increase but that the strength of contraction would decrease or stay unchanged. Approximately one-half of the students predicted that breathing frequency would increase but depth of breathing would decrease (also erroneous). Explanations for these erroneous predictions were elicited, and the reasons offered revealed significant misconceptions about cardiac and respiratory mechanics. The persistence of such misconceptions was demonstrated in a small group of first-year medical students. A general approach to detecting and remediating misconceptions is discussed.

Changing central nervous system control following intercostal nerve transfer.

OBJECT: The goal of this study was to find which central nervous system (CNS) pathways are involved in volitional control over reinnervated biceps or pectoral muscles. METHODS: Intercostal nerves (ICNs) were coapted to the musculocutaneous nerve (MCN) or the medial pectoral nerve (MPN) in 23 patients with root avulsions of the brachial plexus to restore biceps or pectoral muscle function. The facilitatory effects of respiration and voluntary contraction on cortical motor-evoked potentials of biceps or pectoral muscles were used to study CNS control over the reinnervated muscles. The time course of the facilitatory effect of respiration and voluntary contraction differed significantly. In the end stage of nerve regeneration, the facilitatory effect of voluntary contraction was significantly larger than that of respiration, indicating that the CNS control network over the muscle comes to resemble that of the recipient nerve (MCN or MPN) rather than that of the donor nerve (ICN). CONCLUSIONS: The strengthening of previously subthreshold synaptic connections in a CNS network connecting ICN to MCN or MPN neurons may underlie changing excitability.

[Participation of rostral ventral medullary neuron structures in the regulation of the respiratory rhythm mechanism in rats]. / Uchastie rostral'nykh ventromedulliarnykh neironnykh struktur v reguliatsii mekhanizma formirovaniia dykhatel'nogo ritma u krys.

The role of neuronal structures of the rostral ventromedullary area in regulation of central inspiratory activity, was studied. The data obtained suggests that the structures of subretrofacial area are important for the respiratory rhythm generation due to regulation of excitability of the inspiratory neurons.

[Pre-Bötzinger complex participates in respiratory effects of thyroliberin]. / Kompleks pre-Betzingera uchastvuet v realizatsii respiratornykh éffektov tiroliberina.

Responses of the TRH microinjections into the pre-Bötzinger complex of adult anesthetised rats involved a dose-dependent increase in respiratory rate as well as shortening of inspiratory and expiratory duration. The tidal volume and inspiratory muscles' activity decreased following high concentrations of the TRH. The heart rate did not change. The findings suggest that the pre-Bötzinger complex is at least partly responsible for the TRH tachypnoic effect.

[Participation of reticular neurons of the cat medulla oblongata in the integration of the respiration center activity]. / Uchastie retikuliarnykh neironov prodolgovatogo mozga koshki v integrativnoi deiatel'nosti dykhatel'nogo tsentra.

Reticular neurons of the respiratory centre are divided into three groups. The 1st one is located in the medial areas and accepts afferents from chemoreceptors. The 2nd one is located in inspiratory and expiratory areas of the centre and take part in integration of afferent signals and activation of the effector mechanism. The 3rd group is present in both areas and organizes the effector activity of the centre. Electrical stimulation of the brain stem nuclei can modify reticular neurons in lateral areas.

[Comparative analysis of changes in respiration and systemic hemodynamics during activation of GABA receptors in cats and rats]. / Sravnitel'nyi analiz izmenenii dykhaniia i sistemnogo krovoobrashcheniia u koshek i krys pri aktivirovanii GAMK-retseptorov.

Effects of alpha-hydroxybutyrate (GHB) involved a decrease in the respiration rate and subsequent periodic breathing in anesthetised cats and rats. No considerable changes occurred in systemic circulation. There were, however, some differences between the species in the patterns of respiratory arrest. Possible mechanisms of the similarity and difference are discussed.

[The role of pharyngeal muscles in the regulation of airway resistance during inspiration resistive load in rabbits]. / Rol' faringeal'nykh myshts v reguliatsii soprotivleniia dykhatel'nykh putei pri intspiratornoi rezistivnoi nagruzke u krolikov.

In anesthetised spontaneously breathing rabbits, an increase in the inspiratoryactivity m.genioglossus was greater than a simultaneous increase in the respiratory activity of the diaphragm cluring loaded breathing. A bypass of the air flow via tracheostoma did not affect the response of the m.genioglossus to a resistive load. The difference seems to be due to different functional inputs from the lung mechanoreceptors to phrenic and hypoglossal neuronal pools.

[Effects of the local stimulation of the insular cortex on respiration in rats]. / Respiratornye éffekty lokal'nogo razdrazheniia insuliarnoi kory golovnogo mozga krysy.

Two distinct patterns of respiratory responses to electrical microstimulation were elicited from the rat insular cortex: a decrease in respiratory airflow and tidal volume with no alteration of the respiratory rate (the inhibition response) and an increase in respiratory rate and inspiratory airflow (the excitation response). Gastric motility changes could also be elicited from the anterior insular cortex simultaneously with the inhibition response. The data suggests overlapping of the inhibition response area in the anterior insular cortex with a gastrointestinal representation there, and of the excitation response area in the posterior insular cortex with a cardiovascular representation.

[Comparative analysis of responses of the thoracic and abdominal respiration components to hypercapnia and muscular work]. / Sravnitel'nyi analiz reaktsii torakal'nogo i abdominal'nogo komponentov dykhaniia na giperkapniiu i myshechnuiu rabotu.

The ratio of thoracic and abdominal contribution to ventilatory responses to hypercapnia in humans was found to depend on the initial ratio of thoracic and abdominal breathing reserves as determined by the body position in space. In muscular work, participation of the respiratory muscles in locomotor loads becomes a factor affecting the ratio of thoracic and abdominal components of ventilatory response.

Recording from afferents in the intact recurrent laryngeal nerve during respiration and vocalization.

The goal of this study was to determine whether sensory fibers in an intact recurrent laryngeal nerve (RLN) are influenced by respiration or vocalization. Patterns of RLN afferent activity were examined during respiration and evoked vocalization by means of midbrain electrical stimulation in cats anesthetized with alpha-chloralose. Nerve bundles were dissected from an intact RLN, with motor function preserved. The bundles were cut and the laryngeal end was placed on floating bipolar electrodes. Fifteen right RLNs were examined. A total of 9 single and multiunit afferent fibers from 4 cats were isolated and examined during respiration. Four units, analyzed from 3 fibers, showed respiratory phase modulation. Eight units, analyzed from 4 fibers in 1 cat, were observed during vocalization and showed no vocalization phase modulation. The RLN afferents could contribute to reflex modulation of the respiratory cycle, but more extensive sampling would be necessary to preclude effects from vocalization.

Importance of neurokinin-1 receptors in the nucleus tractus solitarii of mice for the integration of cardiac vagal inputs.

Unmyelinated vagal afferents from the heart terminate within the nucleus tractus solitarii (NTS) located in the dorsomedial medulla. The neurotransmitter and postsynaptic receptors mediating information from cardiac vagal receptors to the NTS are unknown. This study determined the effects of neurokinin-1 (NK1) receptor blockade on: (i) the reflex response evoked following aortic root injection of either veratridine (1-3 microg/kg) or bradykinin (80-300 ng/kg) to stimulate cardiac receptors in in vivo anaesthetized mice; and (ii) the evoked synaptic response of cardioreceptive NTS neurons following both intraleft-ventricular injection of veratridine or bradykinin, and electrical stimulation of the ipsilateral vagus nerve in an arterially perfused working heart-brainstem preparation of mouse. Administration of CP-99,994 (0.75-1.5 mg/kg i.v.), a specific NK1 antagonist, attenuated significantly the evoked reflex bradycardia and depressor response following cardiac receptor (n = 6), but not pulmonary chemoreflex stimulation in vivo. From extracellular recordings of cardioreceptive NTS neurons, CP-99,994 reduced reversibly the total number of evoked spikes, peak firing frequency and response duration evoked by intraventricular injections of veratridine (n = 5) or bradykinin (n = 5). The number of evoked action potentials following electrical stimulation of the vagus nerve was also reduced. In five whole cell recordings of NTS neurons, both the evoked depolarization following cardiac receptor stimulation, and the peak amplitude and duration of vagus nerve-evoked EPSPs were reduced by CP-99,994; synaptic inputs from both peripheral chemoreceptors or pulmonary C-fibres were unaffected. These data support a selective involvement of NK1 receptors in the transmission of cardiac vagal afferent inputs to NTS neurons integrating cardiorespiratory information.

Gastric ulcer presenting as gastroesophageal reflux and apnea in a term neonate.

Apnea in the neonatal period frequently is associated with prematurity. Full-term infants who develop apnea usually have associated clinical conditions such as infection, shock, metabolic disorders, neonatal abstinence syndrome, intracranial pathology, and gastroesophageal reflux. Gastric ulcer also is a rare phenomenon in the neonatal period. We describe a full-term infant presenting with apnea. Upon investigation, a 6-channel pneumocardiogram revealed central apnea and multiple episodes of low esophageal pH (< 4), which is suggestive of gastroesophageal reflux. This was confirmed by an upper gastrointestinal series. A small antral ulcer crater also was demonstrated. When assessing the etiology of apnea in a full-term infant, gastroesophageal reflux and gastric ulcer should be considered.

[The current methodological approaches in assessing nasal breathing function]. / Sovremennye metodicheskie podkhody pri otsenke funktsii nosovogo dykhaniia.

The techniques currently used in assessment of nasal respiration with classification and comparative analysis, own experience with maintenance of ATMOS-200 rhinomanometer are outlined. Nasal respiration is best to assess objectively with devices estimating aerodynamic resistance of the nose. The techniques of the anterior and posterior active rhinomanometry (rhinoresistometry) are effective. Acoustic rhinometry is a good adjuvant.

Long-term within-subject variability of inspiratory neural drive response to hypoxia.

STUDY OBJECTIVE: We analyze the within-subject variation of mouth occlusion pressure (P0.1) response to progressive isocapnic hypoxic stimulation over long time periods in normal subjects. PATIENTS AND INTERVENTIONS: We studied 21 healthy subjects (14 male and 7 female; aged 40+/-12 yrs) (mean+/-SD). Lung volumes, basal P0.1, and P0.1 response to hypoxia were measured on two separate occasions 2 months apart, under similar ambient and clinical conditions. RESULTS: There was no significant change in clinical condition, FVC, FEV1, arterial oxygenation saturation, end-tidal and mixed venous PCO2 levels, or P0.1 between the two visits. The mean P0.1 responses to hypoxia in the two explorations were 0.032+/-0.022 and 0.034+/-0.022 kPa/%, respectively. There was a moderate intrasubject variability of P0.1 response to hypoxia, with a coefficient of reproducibility of 0.01 kPa/%. Power calculations to establish the optimal sample size required for hypoxic stimulation are presented. CONCLUSION: Long term within-subject variability of P0.1 response to hypoxia is moderate. This intrinsic variability needs to be emphasized when interpreting the effects of experimental interventions on hypoxic sensitivity.

Influence of mechanical stretch on thrombin regulation by fetal mixed lung cells.

Respiratory distress syndrome (RDS) is characterized by intrapulmonary fibrin deposition, which can adversely affect surfactant function, and stimulate fibroblast proliferation, which may contribute to the development of bronchopulmonary dysplasia (BPD). We speculated that the premature lung may have impaired regulation of thrombin, thus making preterm infants susceptible to fibrin formation within the lung. Therefore, we studied the effect of stretch, which simulates fetal breathing movements (FBMs), on the generation and inhibition of a key hemostatic enzyme-thrombin-by rat fetal mixed lung cells (FMLCs). Our results showed that stretch induced glycosaminoglycan production with increased antithrombin activity due to an increase in the concentration of active chondroitin sulfate. Stretch downregulated secretion of tissue factor procoagulant activity, which may lead to decreased thrombin generation on the surface of FMLCs. Overall, stretch enhanced the local control of thrombin by FMLCs. These results suggest that premature infants, who will have experienced less FBM, may have impaired thrombin regulation. Impaired thrombin regulation likely contributes to increased fibrin deposition and, potentially, the development of BPD.