External respiration response of trained skiers to intermittent normobaric hypoxia

As part of a study on the resistance of subjects adapted to aerobic physical activity to hypoxia, the ventilatory response of trained skiers whose regular physical training is associated with hyperventilation to intermittent normobaric hypoxia has been analyzed. A test session consisted of three cycles of breathing alternately a hypoxic gas mixture (10 vol % O₂) for 5 min and normal air for 5 min. The skiers have a lower oxygen consumption rate as compared with untrained subjects, i.e., a reduced resistance to hypoxia. Therefore, the efficiency of respiration during hypoxia is lower in atheltes, which is caused by a rapid decrease in blood oxygenation, whereas during breathing normal atmospheric air, the efficiency of respiration is lower in untrained subjects.     

Extension of the Functional Range of Respiratory and Gas Exchange Responses in Repetitive Hypoxia

External respiration and gas exchange were studied in healthy volunteers during a session of intermittent normobaric hypoxia (INH) consisting of three cycles of breathing alternately a hypoxic mixture (10.7% O₂) for 5 min and normal air for 5 min. The ventilatory response increased in the successive cycles of hypoxia and gradually decreased during the normoxic intervals. These changes were accompanied by an increase in carbon dioxide in lung air, which was not eliminated by the increased pulmonary ventilation during the hypoxic intervals. However, the mean oxygen consumption did not change during the INH session because the ventilatory reactivity and breathing depth, as well as the efficiency of oxygen utilization, increased from cycle to cycle.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 3, 2005, pp. 100–107.Original Russian Text Copyright © 2005 by Krivoshchekov, G. Divert, V. Divert.     

Compensatory and adaptive rearrangement in the human respiratory system under acute hypoxic conditions

Relationships between the parameters of external respiration (minute volume and respiration rate) and those of internal, tissue respiration (oxygen consumption, arteriovenous oxygen difference and efficiency of oxygen uptake) were studied during a period of acute hypoxia and upon its completion. The subjects were exposed to hypoxia for 25 min using oxygen-nitrogen hypoxic gas mixtures (HGMs) differing in oxygen content (8 and 12%, HGM-8 and HGM-12, respectively). From the third to the fifth minutes of exposure to HGM-8, the respiration minute volume (RMV) was found to increase by 51 ± 33% as compared to the background value; however, the body’s oxygen consumption (OC) was 35 ± 22% reduced. Afterwards, OC grew to reach, from the 20th to the 25th min of hypoxia, 108 ± 21% of the background value and 181% of the value determined from the third to the fifth minutes of hypoxia. OC growth was accompanied by an insignificant RMV increase (by 12%) as compared to the level determined from the third to the fifth minutes of hypoxia, whereas the efficiency of oxygen uptake from the arterial blood increased by 75% for the same period. RMV growth from the third to the fifth minutes of hypoxia occurred as expense result of a higher breathing depth; at the same time, the respiration rate decreased as compared to the background value. By the period from the 20th to the 25th min of exposure to HGM-8, the respiration rate increased by 21% as compared to the period from the third to the fifth minutes of hypoxia. The efficiency of oxygen uptake from the arterial blood remained higher than the background value for at least 5 min after completion of the exposure to HGM-8. During the same period, the ventilation equivalent, an indicator of the efficiency of external respiration, i.e., of oxygen supply to the body, was significantly lower than the background value. During the exposure to HGM-12, RMV increased to a lesser extent than on exposure to HGM-8, however, the efficiency of oxygen uptake was higher during exposure to HGM-12; therefore, OC was also higher in the latter case. Therefore, the assumption that, during hypoxia, intensified external respiration (ventilatory response) itself compensates oxygen deficiency in inhaled air is revised. Ventilatory response is only a portion of the entire functional system of respiration (both external and tissue respiration). The role of ventilatory response is important for conditioning the tissue respiration rearrangement to eliminate deficiency of oxygen consumption during hypoxia. The retained higher oxygen uptake from the arterial blood during the period after completion of hypoxic treatment testifies to the adaptive implication of changes in tissue respiration; the same is confirmed by a reduced ventilation equivalent after hypoxia, which is indicative of the growing efficiency of external respiration, i.e., of an improved oxygen supply to the body.     

Regulation of External Respiration and Gas Exchange during a 20-Day Exposure to Sessions of Intermittent Normobaric Hypoxia

A study was made of the effects of a 20-day course of intermittent normobaric hypoxia (INH) on the parameters of gas exchange and the regulation of respiration in healthy volunteers. A phasic change in oxygen consumption at rest was observed: it decreased on the 10th day of the INH course and increased on the 20th day, with a parallel increase in the efficiency of pulmonary ventilation. According to the hypercapnic test, the ventilatory response threshold decreased, whereas ventilatory sensitivity increased; these effects were most pronounced during the first ten days of INH training and still detectable in recovery. It was assumed that the first phase of training (up to the tenth day) is associated with compensatory activation of pulmonary ventilation owing to an increase in peripheral and central chemosensitivity to the CO₂ stimulus. In the second phase, which was associated with further slight changes in the parameters of external respiration, the gas exchange level is restored owing to an adaptive increase in efficiency of oxygen utilization in cells and tissues.     

Changes in pCO<Subscript>2</Subscript>, Symptoms,and Lung Function of Asthma Patients During Capnometry-assisted Breathing Training

In a recent pilot study with asthma patients we demonstrated beneficial outcomes of a breathing training using capnometry biofeedback and paced breathing assistance to increase pCO₂ levels and reduce hyperventilation. Here we explored the time course changes in pCO₂, respiration rate, symptoms and lung function across treatment weeks, in order to determine how long training needs to continue. We analyzed in eight asthma patients whether gains in pCO₂ and reductions in respiration rate achieved in home exercises with paced breathing tapes followed a linear trend across the 4-week treatment period. We also explored the extent to which gains at home were manifest in weekly training sessions in the clinic, in terms of improvement in symptoms and spirometric lung function. The increases in pCO₂ and respiration rate were linear across treatment weeks for home exercises. Similar increases were seen for in-session measurements, together with gradual decreases in symptoms from week to week. Basal lung function remained stable throughout treatment. With our current protocol of paced breathing and capnometry-assisted biofeedback at least 4 weeks are needed to achieve a normalization of pCO₂ levels and reduction in symptoms in asthma patients.     

Effect of intermittent hypoxic hypoxia on energy supply of rat skeletal muscle during adaptation to physical load

The experiment, on Wistar male rats was carried out to investigate influence of endurance training (swimming with load 7.0 +/- 1.3% body weight, 30 min a day, during 4 weeks) and additional intermittent hypoxic training (12% O2 in N2 - 15 min, 21% O2 - 15 min, 5 sessions a day, during the first 2 weeks) on the following parameters: ADF-stimulated mitochondrial respiration, lactate/pyruvate ratio, succinate dehydrogenase activity, and lipid peroxidation in skeletal muscle. The next oxidation substrates were used: 1 mmol/l succinate and 1 mmol/l alpha-ketoglutarate as well as the next inhibitor succinate dehydrogenase 2 mmol/l malonate. It was shown that physical work combined with intermittent hypoxic training led to the increase of mitochondrial respiration effectiveness in muscle energy supply under alpha-ketoglutarate oxidation in comparison with succinate oxidation as well as to the decrease of succinate dehydrogenase activity and lipid peroxidation. The study suggested that these changes may correct mitochondrial dysfunction under intensive muscular work.     

Effect of anxiety on the function of the cardiorespiratory system

The effects of anxiety on the external respiration system and respiratory sinus arrhythmia (RSA) were studied in healthy subjects in real-life conditions. Changes in external respiration parameters and heart rate variability (HRV) in students going to take their end-of-term exams were assessed relative to a midterm period, and the cardiorespiratory system was monitored in a longitudinal study for 50 days. The function of the cardiorespiratory system was characterized by measuring external respiration parameters and calculating HRV parameters. State anxiety (SA) was assessed using Spielberger’s scale. An increase in SA before an exam was accompanied by a higher breathing rate, a higher tidal volume, and lower HRV indices, especially those related to respiratory sinus arrhythmia (HF and HF _norm). The changes in the parameters depended on the increase in SA. A negative correlation was observed between midterm HF and pre-exam SA. The longitudinal study revealed a distinct negative correlation between respiratory sinus arrhythmia parameters and peak expiratory flow (PEF) and a positive correlation between SA and PEF in the majority of subjects. Changes in cardiorespiratory parameters depended on the changes in SA in the longitudinal study. An increase in SA was accompanied by substantial changes in respiratory sinus arrhythmia (RAS) and external respiration parameters, and their correlation was assumed to indicate that modification of parasympathetic activity plays a leading role in increasing PEF.     

Regulation of mitochondrial uncoupling respiration during exercise in rat heart: role of reactive oxygen species (ROS) and uncoupling protein 2

The physiological significance of cardiac mitochondrial uncoupling protein 2 (UCP2)-mediated uncoupling respiration in exercise is unknown. In the current study, mitochondrial respiratory function, UCP2 mRNA level, UCP2-mediated respiration (UCR), and reactive oxygen species (ROS) generation, as well as manganese superoxide dismutase (MnSOD) activity were determined in rat heart with or without endurance training after an acute bout of exercise of different duration. In the untrained rats, state 4 respiration and UCR-independent respiration rates were progressively increased with exercise time and were 64 and 70% higher, respectively, than resting rate at 150 min, whereas UCR was elevated by 86% with no significant change in state 3 respiration. UCP2 mRNA level showed a 5- and 4-fold increase, respectively, after 45 and 90 min of exercise, but returned to resting level at 120 and 150 min. Mitochondrial ROS production and membrane potential (Deltapsi) increased progressively until 120 min, followed by a decrease to the resting level at 150 min. MnSOD mRNA abundance showed a 2-fold increase at 120 min but MnSOD activity did not change with exercise. Training significantly increased mitochondrial ATP synthetase activity, ADP to oxygen consumption (P/O) ratio, respiratory control ratio, and MnSOD activity, whereas exercise-induced state 4 respiration, UCR, ROS production, and Deltapsi were attenuated in the trained rats. We conclude that (1) UCP2 mRNA expression and activity in rat heart can be upregulated during prolonged exercise, which may reduce cross-membrane Deltapsi and thus ROS production; and (2) endurance training can blunt exercise-induced UCP2 and UCR, and improve mitochondrial efficiency of oxidative phosphorylation due to increased removal of ROS.     

Respiratory responses to short term hypoxia in the snapping turtle, Chelydra serpentina

Among vertebrates, turtles are able to tolerate exceptionally low oxygen tensions. We have investigated the compensatory mechanisms that regulate respiration and blood oxygen transport in snapping turtles during short exposure to hypoxia. Snapping turtles started to hyperventilate when oxygen levels dropped below 10% O(2). Total ventilation increased 1.75-fold, essentially related to an increase in respiration frequency. During normoxia, respiration occurred in bouts of four to five breaths, whereas at 5% O(2), the ventilation pattern was more regular with breathing bouts consisting of a single breath. The increase in the heart rate between breaths during hypoxia suggests that a high pulmonary blood flow may be maintained during non-ventilatory periods to improve arterial blood oxygenation. After 4 days of hypoxia at 5% O(2), hematocrit, hemoglobin concentration and multiplicity and intraerythrocytic organic phosphate concentration remained unaltered. Accordingly, oxygen binding curves at constant P(CO(2)) showed no changes in oxygen affinity and cooperativity. However, blood pH increased significantly from 7.50+/-0.05 under normoxia to 7.72+/-0.03 under hypoxia. The respiratory alkalosis will produce a pronounced in vivo left-shift of the blood oxygen dissociation curve due to the large Bohr effect and this is shown to be critical for arterial oxygen saturation.     

Effect of inspired oxygen on periodic breathing in methy-CpG-binding protein 2 (Mecp2) deficient mice.

Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in the X-linked gene methyl-CpG-binding protein 2 (Mecp2) that encodes a DNA binding protein involved in gene silencing. Periodic breathing (Cheyne-Stokes respiration) is commonly seen in RTT. Freely moving mice were studied with continuous recording of pleural pressure by telemetry. Episodes of periodic breathing in heterozygous Mecp2 deficient (Mecp2(+/-)) female mice (9.4 +/- 2.2 h(-1)) exceeded those in wild-type (Mecp2(+/+)) animals (2.5 +/- 0.4 h(-1)) (P = 0.010). Exposing Mecp2(+/-) animals to 40% oxygen increased the amount of periodic breathing from 118 +/- 25 s/30 min in air to 242 +/- 57 s/30 min (P = 0.001), and 12% oxygen tended to decrease it (67 +/- 29 s/30 min, P = 0.14). Relative hyperoxia and hypoxia did not affect the incidence of periodic breathing in Mecp2(+/+) animals. The ventilation/apnea ratio (V/A) was less at all levels of oxygen in heterozygous Mecp2(+/-) females compare with wild type (P = 0.003 to P < 0.001), indicating that their loop gain is larger. V/A in Mecp2(+/-) fell from 2.42 +/- 0.18 in normoxia to 1.82 +/- 0.17 in hyperoxia (P = 0.05) indicating an increase in loop gain with increased oxygen. Hyperoxia did not affect V/A in Mecp2(+/+) mice (3.73 +/- 0.28 vs. 3.5 +/- 0.28). These results show that periodic breathing in this mouse model of RTT is not dependent on enhanced peripheral chemoreceptor oxygen sensitivity. Rather, the breathing instability is of central origin.     

Oxygen Consumption Stimulated by δ-Aminolevulinic Acid in Darkness and during Irradiation of Dark Grown Wheat Leaves

Dark grown wheat leaves (Triticum aestivum L. cv. Starke II Weibull), treated with δ-aminolevulinic acid in darkness, showed an increased oxygen uptake as measured by a Warburg method. The production of CO₂ was also increased in darkness, giving an RQ ? 1. The increased respiration was dependent on the treatment time as well as on the concentration of the δ-aminolevulinic acid. Potassium cyanide suppressed both the normal and the increased respiration. The treatment with δ-aminolevulinic acid caused accumulation of high amounts of protochlorophyllide. Levulinic acid suppressed the increased oxygen uptake as well as the protochlorophyllide accumulation in δ-aminolevulinic acid treated leaves. Irradiation rapidly decreased the protochlorophyllide content with a simultaneous increase in oxygen uptake over the dark value. The peak value of the increase in oxygen uptake was reached after about 5 min. The light induced oxygen uptake was dependent on the amount of PChlide present at the onset of irradiation. Also the CO₂ production was increased during the first minutes of irradiation but soon fell under the buffer control value. Neither potassium cyanide nor heat denaturation affected the oxygen uptake in light in contrast to the effect on the CO₂ production, which was blocked by heat denaturation. The increased oxygen uptake in light initially seems to be a purely photochemical process leading to a release of CO₂, which release is probably an enzymatic process induced by the photo-oxidative decomposition of pigment.     

A model for control of breathing in mammals: coupling neural dynamics to peripheral gas exchange and transport

A new model for aspects of the control of respiration in mammals has been developed. The model integrates a reduced representation of the brainstem respiratory neural controller together with peripheral gas exchange and transport mechanisms. The neural controller consists of two components. One component represents the inspiratory oscillator in the pre-Bötzinger complex (pre-BötC) incorporating biophysical mechanisms for rhythm generation. The other component represents the ventral respiratory group (VRG), which is driven by the pre-BötC for generation of inspiratory (pre)motor output. The neural model was coupled to simplified models of the lungs incorporating oxygen and carbon dioxide transport. The simplified representation of the brainstem neural circuitry has regulation of both frequency and amplitude of respiration and is done in response to partial pressures of oxygen and carbon dioxide in the blood using proportional (P) and proportional plus integral (PI) controllers. We have studied the coupled system under open and closed loop control. We show that two breathing regimes can exist in the model. In one regime an increase in the inspiratory frequency is accompanied by an increase in amplitude. In the second regime an increase in frequency is accompanied by a decrease in amplitude. The dynamic response of the model to changes in the concentration of inspired O₂ or inspired CO₂ was compared qualitatively with experimental data reported in the physiological literature. We show that the dynamic response with a PI-controller fits the experimental data better but suggests that when high levels of CO₂ are inspired the respiratory system cannot reach steady state. Our model also predicts that there could be two possible mechanisms for apnea appearance when 100% O₂ is inspired following a period of 5% inspired O₂. This paper represents a novel attempt to link neural control and gas transport mechanisms, highlights important issues in amplitude and frequency control and sets the stage for more complete neurophysiological control models.     

Individual characteristics of external respiration during intermittent normobaric hypoxia

Correlation and regression relationships between the indices of the body responsiveness to hypoxic impacts and initial individual values of indices of the respiratory system and heart activity were studied in a group of subjects during three repeated cycles of breathing alternately a hypoxic gas mixture (11 vol % O₂) for 5 min and normal air for 5 min. A steady negative correlation between the most important regulatory indicator, the increase in the CO₂ content of the lungs, and its initial level in individual subjects was found. This may determine the known “normalizing” curative and prophylactic effects of intermittent normobaric hypoxia on the gas transport system of the body. A correlation between the individual increase in the CO₂ content of the lungs in response to hypoxia and changes in the heart rate and initial inhalation rate and depth, rather than oxygen consumption by the body, was found.     

Standardized estimation of external respiration function

External respiration in healthy males has, in addition to eupnea, six functionally active variants with one or several indices deviating from the normal values. Hyperpnea and hypopnea are determined by deviations in general oxygen consumption accompanied by adequate changes in pulmonary ventilation and gas exchange. Inhibition of gas exchange in the respiratory parts of the lungs is a typical primary event of hyperventilation, a fact indicated by a decrease in the coefficient of oxygen consumption and a compensatory increase in the minute respiratory volume during hyperventilation. Tension of the respiratory system is especially pronounced during enhanced oxygen consumption (O₂C). Highly effective bradypnea is characterized by infrequent and deep breathing. No tension of the respiratory system is observed even for increased O₂C. This state may be considered a genotypic and phenotypic variant of normal respiration. The data obtained may be used to automate the assessment of gas exchange in the respiratory parts of the lungs.     

The effects of Efaproxyn (efaproxiral) on subcutaneous RIF-1 tumor oxygenation and enhancement of radiotherapy-mediated inhibition of tumor growth in mice

Efaproxiral, an allosteric modifier of hemoglobin, reduces hemoglobin-oxygen binding affinity, facilitating oxygen release from hemoglobin, which is likely to increase tissue pO(2). The purpose of this study was to determine the effect of efaproxiral on tumor oxygenation and growth inhibition of RIF-1 tumors that received X radiation (4 Gy) plus oxygen breathing compared to radiation plus oxygen plus efaproxiral daily for 5 days. Two lithium phthalocyanine (LiPc) deposits were implanted in RIF-1 tumors in C3H mice for tumor pO(2) measurements using EPR oximetry. Efaproxiral significantly increased tumor oxygenation by 8.4 to 43.4 mmHg within 5 days, with maximum increases at 22-31 min after treatment. Oxygen breathing alone did not affect tumor pO(2). Radiation plus oxygen plus efaproxiral produced tumor growth inhibition throughout the treatment duration, and inhibition was significantly different from radiation plus oxygen from day 3 to day 5. The results of this study provide unambiguous quantitative information on the effectiveness of efaproxiral to consistently and reproducibly increase tumor oxygenation over the course of 5 days of treatment, modeling the clinical use of efaproxiral. Also, based on the tumor growth inhibition, the study shows the efaproxiral-enhanced tumor oxygenation was radiobiologically significant. This is the first study to demonstrate the ability of efaproxiral to increase tumor oxygenation and to increase the tumor growth inhibition of radiotherapy over 5 days of treatment.     

Aquatic surface respiration,a widespread adaptation to hypoxia in tropical freshwater fishes

Synopsis Use of the surface water for aquatic respiration (aquatic surface respiration, ASR) is one of the few alternatives to aerial respiration which allow fish to survive extreme hypoxia, yet it has received very little attention. This report examines three generalizations concerning ASR on a phylogenetically and geographically diverse range of tropical freshwater fishes. It demonstrates that ASR greatly enhances survival in hypoxic water, even in fish not morphologically specialized to use the surface film, that ASR is initiated at a distinct threshold oxygen concentration, with time spent at the surface increasing rapidly as O₂ declines, and that with extreme deoxygenation fish perform ASR over 90% of the time. Ninety-four percent of the 31 species of non-air breathing fish tested showed ASR., with the threshold oxygen concentration ranging from 6 to 40 torr.Present address correspondence and reprint requests to D.L. Kramer.     

Positive Expiratory Pressure Improves Oxygenation in Healthy Subjects Exposed to Hypoxia

Introduction

Positive end-expiratory pressure (PEEP) is commonly used in critical care medicine to improve gas exchange. Altitude sickness is associated with exaggerated reduction in arterial oxygenation. We assessed the effect of PEEP and pursed lips breathing (PLB) on arterial and tissue oxygenation under normobaric and hypobaric hypoxic conditions.

Methods

Sixteen healthy volunteers were exposed to acute normobaric hypoxia (Laboratory study, FiO₂=0.12). The protocol consisted in 3-min phases with PEEPs of 0, 5 or 10 cmH₂O, PLB or similar ventilation than with PEEP-10, interspaced with 3-min phases of free breathing. Arterial (pulse oximetry) and quadriceps (near-infrared spectroscopy) oxygenation, ventilation, cardiac function, esophageal and gastric pressures and subjects’ subjective perceptions were recorded continuously. In addition, the effect of PEEP on arterial oxygenation was tested at 4,350 m of altitude in 9 volunteers breathing for 20 min with PEEP-10 (Field study).

Results

During the laboratory study, PEEP-10 increased arterial and quadriceps oxygenation (arterial oxygen saturation +5.6±5.0% and quadriceps oxyhemoglobin +58±73 µmol.cm compared to free breathing; p<0.05). Conversely, PLB did not increase oxygenation. Oxygenation improvement with PEEP-10 was accompanied by an increase in expiratory esophageal and gastric pressures (esophageal pressure swing +5.4±3.2 cmH₂O, p<0.05) but no change in minute ventilation, breathing pattern, end-tidal CO₂ or cardiac function (all p>0.05) compared to PEEP-0. During the field study, PEEP-10 increased arterial oxygen saturation by +6.7±6.0% after the 3^rd minute with PEEP-10 without further significant increase until the 20^th minute with PEEP-10. Subjects did not report any significant discomfort with PEEP.

Conclusions

These data indicate that 10-cmH₂O PEEP significantly improves arterial and muscle oxygenation under both normobaric and hypobaric hypoxic conditions in healthy subjects. PEEP-10 could be an attractive non-pharmacological tool to limit blood oxygen desaturation and possibly symptoms at altitude.     

The respiratory system as an exercise limiting factor in normal trained subjects

Recently, we have shown that an untrained respiratory system does limit the endurance of submaximal exercise (64% peak oxygen consumption) in normal sedentary subjects. These subjects were able to increase breathing endurance by almost 300% and cycle endurance by 50% after isolated respiratory training. The aim of the present study was to find out if normal, endurance trained subjects would also benefit from respiratory training. Breathing and cycle endurance as well as maximal oxygen consumption (VO2max) and anaerobic threshold were measured in eight subjects. Subsequently, the subjects trained their respiratory muscles for 4 weeks by breathing 85-160 l.min-1 for 30 min daily. Otherwise they continued their habitual endurance training. After respiratory training, the performance tests made at the beginning of the study were repeated. Respiratory training increased breathing endurance from 6.1 (SD 1.8) min to about 40 min. Cycle endurance at the anaerobic threshold [77 (SD 6) %VO2max] was improved from 22.8 (SD 8.3) min to 31.5 (SD 12.6) min while VO2max and the anaerobic threshold remained essentially the same. Therefore, the endurance of respiratory muscles can be improved remarkably even in trained subjects. Respiratory muscle fatigue induced hyperventilation which limited cycle performance at the anaerobic threshold. After respiratory training, minute ventilation for a given exercise intensity was reduced and cycle performance at the anaerobic threshold was prolonged. These results would indicate the respiratory system to be an exercise limiting factor in normal, endurance trained subjects.     

Investigation of the breathing pattern structure in competitive exercises of kettlebell lifters

The goal of the research was to determine the characteristics of the breathing pattern in kettlebell lifters. The following main indicators of external respiration were recorded during exercise performance: respiratory rate (RR, f), tidal volume (TV, V _T ), and respiratory minute volume (RMV, V _E ). The dependence of these parameters on the qualification of athletes and competitive exercise intensity was estimated. An SMP-21/01-“R-D” spirograph was used for qualitative and quantitative assessment of the main indicators of breathing patterns in kettlebell lifters. The characteristic changes in breathing of masters of sports (MS) and candidate masters of sport (CMS) were shown mainly for the three parameters, respiratory rate and tidal volume, as well as in the number of breathing cycles per cycle of exercise. Respiratory rate increases and tidal volume decreases at a high-intensity exercise. In international masters of sports (MSIC), the number of breathing cycles per cycle of competitive exercise and, consequently, respiratory rate remain constant independent of physical load. They show the predominance of only one index, tidal volume, which increases from 0.7 ± 0.1 L to 1.2 ± 0.1 L (p < 0.01) with increasing intensity of exercise. We have found transitional forms of breathing patterns in the competitive exercises of kettlebell lifting. The results lay the basis for the development of a novel concept of training and improvement of breathing technique in kettlebell lifting.     

Pulmonary ventilation and cardiac activity in hibernating and arousing golden-mantled ground squirrels (Spermophilus lateralis)

Pulmonary ventilation was assessed in the hibernating and arousing golden-mantled ground squirrel by plethysmography and end-tidal gas analysis. The heart rate and electrocardiogram were monitored simultaneously with ventilation. The hibernating squirrels displayed a periodic respiratory pattern characterized by a variable breathing frequency and tidal volume and often exhibited characteristics of Cheyne-Stokes respiration. Apneic periods averaging 8 to 9 min resulted in a low overall breathing frequency. Cardiac activity in the hibernating ground squirrel was characterized by arrhythmias which correlated with ventilation and by alterations in the electrocardiogram typically seen in hibernating animals. Arousal from hibernation was accompanied by: (i) a replacement of periodic by continuous ventilation, (ii) a 25-fold increase in V_E in the first hour which was accounted for by the increment in breathing frequency, and (iii) a marked decrease in the ratio of heart beats to breaths. The techniques developed in the present study will permit further quantitative investigations of pulmonary ventilation and its control in hibernating animals.