An increased carbon dioxide production in transient hypoxia in healthy subjects at rest

Indices of pulmonary gas exchange and heart rate (HR) have been measured in 24 healthy subjects not adapted to hypoxia after hypoxic aerial mixture (HAM) (17, 15, 13 vol % of oxygen) respiration for 15 min. Using group data analysis, it has been shown that hypoxia under the conditions of inhalation of 17 and 15 vol % of O₂ caused no significant changes. Hypoxia under the conditions of 13 vol % of O₂ inhalation is a threshold one, when ventilation (SpO₂) drops below 85%. A significant increase in the lung ventilation (Ve) (10–14%, p < 0.05) and HR (11–15%, p < 0.05) have been observed in this case. Hyperpnea was accompanied by an increase in the oxygen uptake rate by 10% and carbon dioxide release rate (10–18%, p < 0.05). On the contrary, individual data analysis showed changes in the pulmonary gas exchange indices in 90% of subjects in the case of inhalation of 17 vol % of O₂ HAM. Four response types have been found: ventilation (increase in lung ventilation), hypoxic hypometabolism (decrease in oxygen consumption rate), and mobilization response (increase in oxygen utilization in the lungs), and anaerobic response, which is expressed in an increase in the carbon dioxide release rate along with an increase in the respiratory quotient. All these responses are of an individual type, but the ventilation response is developed in response to hypoxia caused by inhalation of 13 vol % of O₂ HAM and a decrease in SpO₂ below 85% in more than 60% of cases.     

Generation of recombinant Orf virus using an enhanced green fluorescent protein reporter gene as a selectable marker

Background

The purpose of this study was to compare the effects of 0.5 fraction of inspired oxygen (FiO₂) and >0.95 FiO₂ on pulmonary gas exchange, shunt fraction and oxygen delivery (DO₂) in dorsally recumbent horses during inhalant anesthesia. The use of 0.5 FiO₂ has the potential to reduce absorption atelectasis (compared to maximal FiO₂) and augment alveolar oxygen (O₂) tensions (compared to ambient air) thereby improving gas exchange and DO₂. Our hypothesis was that 0.5 FiO₂ would reduce ventilation-perfusion mismatching and increase the fraction of pulmonary blood flow that is oxygenated, thus improving arterial oxygen content and DO₂.

Results

Arterial partial pressures of O₂ were significantly higher than preanesthetic levels at all times during anesthesia in the >0.95 FiO₂ group. Arterial partial pressures of O₂ did not change from preanesthetic levels in the 0.5 FiO₂ group but were significantly lower than in the >0.95 FiO₂ group from 15 to 90 min of anesthesia. Alveolar to arterial O₂ tension difference was increased significantly in both groups during anesthesia compared to preanesthetic values. The alveolar to arterial O₂ tension difference was significantly higher at all times in the >0.95 FiO₂ group compared to the 0.5 FiO₂ group. Oxygen delivery did not change from preanesthetic values in either group during anesthesia but was significantly lower than preanesthetic values 10 min after anesthesia in the 0.5 FiO₂ group. Shunt fraction increased in both groups during anesthesia attaining statistical significance at varying times. Shunt fraction was significantly increased in both groups 10 min after anesthesia but was not different between groups. Alveolar dead space ventilation increased after 3 hr of anesthesia in both groups.

Conclusions

Reducing FiO₂ did not change alveolar dead space ventilation or shunt fraction in dorsally recumbent, mechanically ventilated horses during 3 hr of isoflurane anesthesia. Reducing FiO₂ in dorsally recumbent isoflurane anesthetized horses does not improve oxygenation or oxygen delivery.     

Ventilatory responses to temperature variation in the fresh water turtle,Mauremys caspica leprosa

A study of lung gas exchange in the fresh water turtle Mauremys caspica leprosa at normal physiological body temperatures (15, 25 and 35 °C) was extended to extreme temperatures (5 and 40 °C) to determine whether the direct relationship between body temperature and ventilatory response found in many lung-breathing ectotherms including other chelonian species was maintained. From 5 to 35 °C the lung ventilation per unit of O₂ uptake and CO₂ removed declined with temperature. Consequently, lung CO₂ partial pressure increased with temperature. Its value was maintained within narrow limits at each thermal constant, suggesting a suitable control throughout the complete ventilatory cycle. At 40 °C the ventilatory response showed the opposite trend. The ratios of ventilation to lung gas exchange increased compared to their values at 35 °C. The impact of this increased breathing-lowering the estimated mean alveolar CO₂ partial pressure-was nevertheless less than expected due to an increase in calculated physiological dead space. This suggests that the relative hyperventilation in response to hyperthermia found in Mauremys caspica leprosa is related to evaporative heat loss.Abbreviations BTPS body temperature, ambient pressure, saturated with water vapour - CTM critical thermal maximum - F_N2 fractional concentration of nitrogen - PA _CO2or PL _CO2 alveolar or lung CO₂ pressure - PA_O2or PL_O2 alveolar or lung O₂ pressure - PI_O2 inspired O₂ pressure - R respiratory exchange ratio - STPD standard temperature, standard pressure, dry - T _a ambient temperature - T _b body temperature - VA alveolar ventilation - VA/VCO₂ relative alveolar ventilation (alveolar ventilation per unit of CO₂ removed) - VO₂ O₂ uptake - VCO₂ CO₂ output - V _D anatomical dead space volume - V _D physiological dead space volume - VE/VO₂ ventilatory equivalent for O₂ - VE pulmonary ventilation or expiratory minute volume - VE/VCO₂ ventilatory equivalent for CO₂ - V _T tidal volume     

Systemic oxygen extraction during incremental exercise in patients with severe chronic obstructive pulmonary disease

To determine if decreased systemic oxygen (O₂) extraction contributes to the exercise limit in severe chronic obstructive pulmonary disease (COPD), 40 consecutive incremental cycle ergometer exercise tests performed by such patients, from which a “log-log” lactate threshold (LT) was identified, were compared to those of 8 patients with left ventricular failure (LVF) and 10 normal controls. Pulmonary gas exchange and minute ventilation were measured continuously and arterial blood gas tensions, pH, and lactate concentrations were sampled each minute. Cardiac output (Q˙ _c) was measured by first-pass radionuclide ventriculography. The systemic O₂ extraction ratio (O₂ER) was calculated as arterial − mixed venous O₂ content difference (C _aO₂ − C _vO₂)/C _aO₂. Peak exercise O₂ uptake (V˙O_2peak) was markedly reduced in both COPD and LVF [41 (3) and 42 (3)% predicted, respectively], compared to controls [89 (2)% predicted, P < 0.0001 for each]. Similarly, the LT occurred at a low percentage of predicted maximal oxygen consumption in both COPD and LVF [25 (2) and 27 (3)%] compared to normals [46 (3)%, P < 0.0001 for each]. The systemic O₂ER at peak exercise was severely reduced in COPD [0.36 (0.02)] compared to the other groups [P < 0.0001 for each], for whom it was nearly identical [0.58 (0.03) vs 0.63 (0.04), LVF vs control, P > 0.05]. In the COPD group, an early LT correlated with reduced systemic O₂ER at peak exercise (r = 0.64, P < 0.0001), but not with any index of systemic O₂ delivery. These data suggest that lactic acidemia during exercise in patients with severe COPD is better related to abnormal systemic O₂ extraction than to its delivery and contributes to the exercise limit. Accepted: 10 March 1998     

Comparison of CO<Subscript>2</Subscript> and H<Subscript>2</Subscript>O fluxes over grassland vegetations measured by the eddy-covariance technique and by open system chamber

Measurements of CO₂ and H₂O fluxes were carried out using two different techniques—eddy-covariance (EC) and open system gas exchange chamber (OC)—during two-years’ period (2003–2004) at three different grassland sites. OC measurements were made during fourteen measurement campaigns. We found good agreement between the OC and EC CO₂ flux values (n = 63, r ² = 0.5323, OC F_CO2 = −0.6408+0.9508 EC F_CO2). The OC F_H2O values were consistently lower than those measured by the EC technique, probably caused by the air stream difference inside and outside the chamber. Adjusting flow rate within the chamber to the natural conditions would be necessary in future OC measurements. In comparison with EC, the OC proved to be a good tool for gas exchange measurements in grassland ecosystems.     

A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species

Various aspects of the biochemistry of photosynthetic carbon assimilation in C₃ plants are integrated into a form compatible with studies of gas exchange in leaves. These aspects include the kinetic properties of ribulose bisphosphate carboxylase-oxygenase; the requirements of the photosynthetic carbon reduction and photorespiratory carbon oxidation cycles for reduced pyridine nucleotides; the dependence of electron transport on photon flux and the presence of a temperature dependent upper limit to electron transport. The measurements of gas exchange with which the model outputs may be compared include those of the temperature and partial pressure of CO₂(p(CO₂)) dependencies of quantum yield, the variation of compensation point with temperature and partial pressure of O₂(p(O₂)), the dependence of net CO₂ assimilation rate on p(CO₂) and irradiance, and the influence of p(CO₂) and irradiance on the temperature dependence of assimilation rate.Abbreviations RuP₂ ribulose bisphosphate - PGA 3-phosphoglycerate - C=p(CO₂) partial pressure of CO₂ - O=p(O₂) partial pressure of O₂ - PCR photosynthetic carbon reduction - PCO photorespiratory carbon oxidation     

Mixed arterial concentration of O2 in a global pulmonary gas exchange model

In a global pulmonary gas exchange model where global diffusion and ventilation are given, the effects of variations of local conductance?perfusion and ventilation?perfusion ratios on O₂ concentration in arterial blood are studied. We give a special regard to the ability to get local maxima for this O₂ concentration when the repartition of our parameters is heterogeneous.     

An estimation of CO<Subscript>2</Subscript> fixation capacity in mangrove forest using two methods of CO<Subscript>2</Subscript> gas exchange and growth curve analysis

In many coastal areas of South-East Asia, attempts have been made to revive coastal ecosystem by initiating projects that encourage planting of mangrove trees. Compared to the terrestrial trees, mangrove trees possess a higher carbon fixation capacity. It becomes a very significant option for clean development mechanism (CDM) program. However, a reliable method to estimate CO₂ fixation capacity of mangrove trees has not been established. Acknowledging the above fact, we decided to set up an estimation method for the CDM program, using gas exchange analysis to estimate mangrove productivity, we put into consideration the net CO₂ fixation of reforested Kandelia candel (5-, 10-, and 15-year-old stand). This was estimated by gas exchange analysis and growth curve analysis. In growth curve analysis, we drew a growth curve of a single stand using data of above- and below-ground biomass. In the gas exchange analysis, we calculated CO₂ fixation capacity by (1) measuring respiration rate of each organ of stand and calculating respiratory CO₂ emission from above- to below-ground biomass. (2) Measuring the single-leaf photosynthetic rate in response to light intensity and calculating the photosynthetic CO₂ absorption. (3) We also developed a model for the diurnal changes in temperature, and monthly averages based on one-day estimation of CO₂ absorption and emission, which we corrected by this model in order to estimate the net CO₂ fixation capacity in response to temperature. Comparing the biomass accumulation of the two methods constructed for the same forest, the above-ground biomass accumulation of 10-year-old forest (34.3 ton ha⁻¹ yr⁻¹) estimated by gas exchange analysis was closely compared to those of growth curve analysis (26.6 ton ha⁻¹ yr⁻¹), suggesting that the gas exchange analysis was capable of estimating mangrove productivity. The validity of the estimated CO₂ fixation capacity by the gas exchange analysis and the growth curve analysis was also discussed.     

A system to simulate gas exchange in humans to control quality of metabolic measurements

We have developed a gas exchange simulation system (GESS) to assess the quality control in measurements of metabolic gas exchange. The GESS simulates human breathing from rest to maximal exercise. It approximates breath-by-breath waveforms, ventilatory output, gas concentrations, temperature and humidity during inspiration and expiration. A programmable motion control driving two syringes allows the ventilation to be set at any tidal volume (V _T), respiratory frequency (f), flow waveform and period of inspiration and expiration. The GESS was tested at various combinations of V _T (0.5–2.5 l) and f (10–60 stroke · min⁻¹) and at various fractional concentrations of expired oxygen (0.1294–0.1795); and carbon dioxide (0.0210–0.0690) for a pre-set flow waveform and for expired gases at the same temperature and humidity as room air. Expired gases were collected in a polyethylene bag for measurement of volume and gas concentrations. Accuracy was assessed by calculating the absolute and relative errors on parameters (error = measured−predicted). The overall error in the gas exchange values averaged less than 2% for oxygen uptake and carbon dioxide output, which is within the accuracy of the Douglas bag method. Accepted: 4 June 1998     

Post-illumination burst of carbon dioxide inPhaseolus vulgaris L. as affected by leaf temperature

The effect of leaf temperature on the post-illumination burst of CO₂ (PIB) in 15 day-old primary bean leaves (Phaseolus vulgaris L.) was studied by means of infrared gas analysis in a closed gas exchange system. The amplitude and kinetic of PIB was different with its own characteristic course for different temperature steps. The temperature optimum for the PIB at 21% O₂ near the carbon dioxide compensation concentration Λ (150 mg m^-3) was 33 °C while that for net photosynthetic rate (P _N) at 21% O₂ and 600 mg m^-3 CO₂ was 24.5 °C. The PIB was observed to 12…33 s after the darkening of leaves. No PIB was observed at 2% O₂. The applicability of PIB as an estimate of photorespiration rateR _p has been proved by comparing it with extrapolation of the relationship betweenP _n and CO₂ concentration to zero.     

Flooding tolerance of Carex species. II. Root gas-exchange capacity

Root CO₂ and O₂ gas exchange were measured in young Carex extensa Good. (flooding sensitive), C. remota L. and C. pseudocyperus L. (both flooding tolerant) plants, precultured either aerobically or anaerobically. Temperature changes form 21 to 11 °C had small effects on root CO₂ release from respiration. In C. extensa, root respiration rates decreased when plants were precultured anaerobically, while in C. pseudocyperus preculture conditions had no effect on root CO₂ release. In contrast to CO₂, temperature decrease significantly enhanced radial oxygen loss from the roots during the light phase, indicating that at 20 °C the O₂ transported form the shoot to the root met the demand for root respiration quite well, while at 11 °C excess O₂ entered the root and was released into the anaerobic nutrient solution. In C. remota and C. pseudocyperus, the maximal O₂ concentration of a previously anaerobic nutrient solution was attained after several days of equilibration with the atmosphere through the plant body and was approximately one-third of that found in C. extensa, indicating that the diffusion resistance of the root/rhizosphere interface to O₂ is much lower in the C. extensa root than in the flooding-tolerant Carex species. A calculation of the maximal attainable root length that can be sustained by pure O₂ diffusion from CO₂ exchange, and anatomical data obtained earlier, revealed that longitudinal diffusion of O₂ through the root is sufficient for the oxygen supply of the root. It is concluded that the postulate of a gas mass-flow into the root is not necessary for the understanding of flooding tolerance of Carex species. Received: 10 February 1998 / Accepted: 2 July 1998     

Influence of stem lacunar structure on gas transport: relation to the oxygen transport potential of submersed vascular plants

The influence of stem lacunar structure on the potential of diffusion and mass flow to meet estimated root O₂ demands was evaluated and compared in four submersed aquatic plant species. Internodal lacunae formed large continuous gas canals which were constricted at the nodes by thin, perforated diaphragms. Gas transport studies showed that nodes had little effect on diffusion, but significantly reduced mass flow. Measured diffusive resistances approximated those predicted by Fick's first law, ranged from 203 to 5107 × 10⁸ s m⁻⁴ and increased as lacunar area decreased in Potamogeton praelongus, two Myriophyllum species and Elodea canadensis. Our analysis suggested that diffusion could satisfy estimated root O₂ demands given the development of relatively steep O₂ gradients (0.15–0.35 mol O₂ mor⁻¹ per 0.5 m stem) between shoots and roots. Plants with high resistances (e.g. > 750 × 10⁸ s m⁻⁴) and long lacunar pathlengths may be unable, even during active photosynthesis, to support the O₂ demands of a large root system by diffusion alone. Measured nodal resistances to mass flow approximated those predicted by Hagen-Poiseuille law and ranged from 46 to 2029 × 10⁸ Pa s m⁻³. Our analysis suggested that these resistances were quite low and that relatively small pressure differentials (< 150 Pa per 0.5 m stem) could drive mass flow at rates which would support root O₂ demands. Possible mechanisms whereby plant architecture may serve to maintain these pressure differentials are proposed.     

Respiratory and cardiovascular responses to acute hypoxia and hyperoxia in internally pipped chicken embryos

During the first day of hatching, the developing chicken embryo internally pips the air cell and relies on both the lungs and chorioallantoic membrane (CAM) for gas exchange. Our objective in this study was to examine respiratory and cardiovascular responses to acute changes in oxygen at the air cell or the rest of the egg during internal pipping. We measured lung (V·_O2lung) and CAM (V·_O2CAM) oxygen consumption independently before and after 60 min exposure to combinations of hypoxia, hyperoxia, and normoxia to the air cell and the remaining egg. Significant changes in V·_O2total were only observed with combined egg and air cell hypoxia (decreased V·_O2total) or egg hyperoxia and air cell hypoxia (increased V·_O2total). In response to the different O₂ treatments, a change in V·_O2lung was compensated by an inverse change in V·_O2CAM of similar magnitude. To test for the underlying mechanism, we focused on ventilation and cardiovascular responses during hypoxic and hyperoxic air cell exposure. Ventilation frequency and minute ventilation (V_E) were unaffected by changes in air cell O₂, but tidal volume (V_T) increased during hypoxia. Both V_T and V_E decreased significantly in response to decreased P_CO2. The right-to-left shunt of blood away from the lungs increased significantly during hypoxic air cell exposure and decreased significantly during hyperoxic exposure. These results demonstrate the internally pipped embryo's ability to control the site of gas exchange by means of altering blood flow between the lungs and CAM.     

Über den Einfluß niedriger und hoher O2-Partialdrucke auf den Sauerstoff- und Kohlendioxidumsatz von Amaranthus und Phaseolus während der Lichtphase

Summary Carbon dioxide and oxygen gas exchange of illuminated Amaranthus and Phaseolus leaves was measured from 0–600 ppm of CO₂ in an open system.At low oxygen concentration (2% O₂) the ratio of CO₂ uptake to O₂ evolution came close to 1.At high oxygen partial pressure (42% O₂) the O₂ compensation point of an Amaranthus leaf was increased and oxygen evolution was depressed. Accordingly the CO₂/O₂ quotients were variable; the lowest value of 1,9 differed significantly from 1,0.The oxygen and carbon dioxide compensation points of a Phaseolus leaf were increased at high oxygen concentration (42% O₂) and oxygen evolution as well as carbon dioxide uptake were reduced. Therefore the ratios CO₂ over O₂ varied and differed greatly from 1,0.It was concluded that the nature of photosynthates is regulated by the gas composition around the leaves.     

A mathematical study of non-equimolar ternary gas diffusion

In view of the increasing evidence that multicomponent diffusion effects could be significant in biological gas exchange systems, a non-equimolar film model of multicomponent diffusion was derived. “Osmotic” ternary diffusion was studied for the gas systems He−N₂−O₂, He−SF₆−O₂, and N₂−SF₆−O₂. Diffusional fluxes and concentration profiles were calculated under both the “square-root” and the “product” flux conditions. Results were also compared with those obtained using the equimolar flux condition. It was found that the greater the difference of the diffusibilities between the two active components in a system, the greater the osmotic fluxes, and also the more alinear the concentration profiles. These results support the suggestion that the “product” condition applies to molecular diffusion in free space, the “square-root” condition to molecular diffusion in pores, and the equimolar flux condition to closed diffusion systems.     

A Mathematical Model of the Controlled Plant of the Réspiratory System

Ability to predict the dynamic response of oxygen, carbon dioxide tensions, and pH in blood and tissues to abrupt changes in ventilation is important in the mathematical modeling of the respiratory system. In this study, the controlled plant (the amount and distribution of O₂ and CO₂) of the respiratory system is modeled. Although the body tissues are divided into a finite number of “compartments” (three tissue groups), in contrast to earlier models, the blood and tissue gas tensions within each compartment are considered to be continuously distributed in time and in one spatial coordinate. The mass conservation equations for oxygen and carbon dioxide involved in the blood-tissue gas exchange are described by a set of partial differential equations which take into account convection of O₂ and CO₂ caused by the flow of blood as well as diffusion due to local tension gradients. Nonlinear algebraic equations for the dissociation curves, which take into account the Haldane and Bohr effects in blood, are used to obtain the relationships between concentrations and partial pressures. Time-variable delays caused by the arterial and venous transport of the respiratory gases are also included. The model so constructed successfully reproduced actual O₂ and CO₂ tensions in arterial blood, and in muscle venous and mixed venous blood when ventilation was abruptly changed.     

Sensitivity of Metasequoia glyptostroboides to ozone stress

2-year-old seedlings of Metasequoia glyptostroboides were grown in open top chambers and exposed to four ozone concentrations [O₃] (charcoal-filtered air, CF; 50, 100, and 200 mm³ m⁻³) for 25 d. Measurements of growth, leaf chlorophyll (Chl) content, and gas exchange parameters were made before and/or after O₃ exposure. Leaf length, crown width, Chl a/b, net photosynthetic rate, stomatal conductance, and transpiration rate were significantly reduced at 100 and 200 mm³(O₃) m⁻³. A remarkable decrease in stomatal conductance also occurred at 50 mm³(O₃) m⁻³.     

The protective effects of hypoxia-induced hypometabolism in the Nautilus

Specimens of Nautilus pompilius were trapped at depths of 225–300 m off the sunken barrier reef south-east of Port Moresby, Papua New Guinea. Animals transported to the Motupore Island laboratory were acclimated to normal habitat temperatures of 18 °C and then cannulated for arterial and venous blood sampling. When animals were forced to undergo a period of progressive hypoxia eventually to encounter ambient partial pressure of oxygen (PO₂) levels of ∼10 mmHg (and corresponding arterial PO₂'s of ∼5 mmHg), they responded by lowering their aerobic metabolic rates to 5–10% of those seen in resting normoxic animals. Coincident with this profound metabolic suppression was an overall decrease in activity, with brief periods of jet propulsion punctuating long periods of rest. Below ambient PO₂ levels of 30–40 mmHg, ventilatory movements became highly periodic and at the lowest PO₂ levels encountered, ventilation occasionally ceased altogether. Cardiac output estimated by the Fick equation decreased during progressive hypoxia by as much as 75–80%, and in the deepest hypometabolic states heart rates slowed to one to two cycles of very low amplitude per minute. By the end of 500 min exposure to ambient PO₂ levels of 10 mmHg or less, the anaerobic end products octopine and succinate had increased significantly in adductor muscle and heart, respectively. Increased concentrations of octopine in adductor muscle apparently contributed to a small intracellular acidosis and to the development of a combined respiratory and metabolic acidosis in the extracellular compartment. On the other hand, increases in succinate in heart muscle occurred in the absence of any change in cardiac pHi. Taken together, we estimate that these anaerobic end products would make up less than 2% of the energy deficit arising from the decrease in aerobic metabolism. Thus, metabolic suppression is combined with a massive downregulation of systemic O₂ delivery to match metabolic supply to demand. Accepted: 26 January 2000     

Responses of aerial ventilation to hypoxia and hypercapnia inChanna argus,an air-breathing fish

Summary The snake-head fish (Channa argus) is an obligate air-breather inhabiting fresh waters in the temperate zone of East Asia.Ventilation of the air-breathing organ and aerial gas exchange were measured in 1 to 2 kg specimens at 15 and 25°C. Additionally, the ventilatory responses to hypoxia and hypercapnia were studied. Aerial ventilation increased from 1.1 to 2.9 mlbtps·kg^–1·min^–1 when temperature rose from 15 to 25°C. Concomitantly, O₂-uptake through airbreathing increased from 0.1 mlstpd·kg^–1·min^–1 (15°C) to 0.28 mlstpd·kg^–1·min^–1 (25°C), whereas aerial gas exchange was less important for CO₂-climination as evident from low gas exchange ratios (0.16 at 15°C, 0.29 at 25°C).Ventilation increases only slightly in response to inspiration of hypercapnic gas mixtures or to hypoxic conditions in water. By contrast, inspiration of hypoxic gas mixtures caused marked increases of ventilation in particular at the higher temperature.Aerial ventilation inChanna is low compared to values for ectothermic pulmonary breathers. However, its ventilatory responses to hypoxia strikingly resemble those of reptiles: The most marked ventilatory response to hypoxia occurs at the higher temperature where the demands for O₂ are greatest.     

The variability of pulmonary gas exchange and respiratory pattern

Very-low-frequency (VLF) fluctuations, whose nature is probably determined by rhythms of energy processes, are known to determine the variability of respiratory and heart rates. It is still unclear to which type of wave processes (chaotic or regular) these rhythm patterns belong. The goal of this study was to investigate the rhythms of pulmonary gas exchange and the variability of the respiratory pattern, as well as to find their possible relation. To analyze the variability of ventilation indices in the VLF band, pneumograms were recorded for 30 min and then the pulmonary gas exchange indices (Ve, pulmonary ventilation; V_O2 V_{O_2 }, oxygen consumption; V_CO2 V_{CO_2 }, carbon dioxide release) were recorded for 30 min using the breath-by-breath method in ten healthy subjects. Spectral analysis carried out using the fast Fourier transform revealed two groups of major peaks: the first one was in the range from 0.2 to 0.3 Hz (the time interval of 3–5 s), which was in good agreement with the respiratory rate varied from 12 to 20 per min in tested subjects; the second was from 0.002 to 0.0075 Hz, which corresponded to the VLF band. The data make it possible to draw a conclusion about the stability of the wave processes found. Apparently, the slow-wave pattern of the pulmonary gas exchange indices belongs to the quasi-periodic oscillation type, reflecting synchronization of oscillators with incommensurable frequencies when the two-frequency pattern dominates. The first oscillator is the chemoreceptor mechanism of the regulation of ventilation, the nature of the second one is still unclear. Taking into consideration that V_O2 V_{O_2 } and V_CO2 V_{CO_2 } depend on energy demand, one can suppose that energy processes form (an)other oscillator(s) of periodic processes.