Oxygen cost of voluntary hyperventilation

1959 ◽  
Vol 14 (2) ◽  
pp. 187-190 ◽  
Author(s):  
John F. Murray
Keyword(s):  
Carbon Dioxide ◽  
Technical Assistance ◽  
Respiratory Exchange Ratio ◽  
Minute Volume ◽  
Open Circuit ◽  
Oxygen Cost ◽  
Voluntary Hyperventilation ◽  
The Mean ◽  
The Difference ◽  
Circuit Technique

The oxygen cost of voluntary hyperventilation was measured using an open circuit technique with three variations, unaided hyperventilation of air, breathing through an increased dead space and adding carbon dioxide to the inspired air. After a given minute volume had been maintained for 10 minutes, the oxygen consumption was the same with the three methods, in spite of marked differences in the respiratory exchange ratio and volume of carbon dioxide produced. The mean oxygen cost for all three methods was 3.2 ml/l. of ventilation. The amount of nonmetabolic oxygen stored during the first minute of hyperventilation was estimated by finding the difference between the oxygen uptake during the 1st minute and the amount utilized when a steady state is reached. It is concluded that the effects of changing oxygen stores are minimal after 10 minutes of hyperventilation and probably after 5 minutes, at a constant minute volume. Note: (With the Technical Assistance of Liana Nebel) Submitted on June 27, 1958

Effect of alterations in end-tidal CO2 tension on flow resistance

1964 ◽  
Vol 19 (4) ◽  
pp. 745-749 ◽  
Author(s):  
Michael T. Newhouse ◽  
Margaret R. Becklake ◽  
Peter T. Macklem ◽  
Maurice McGregor
Keyword(s):  
Flow Resistance ◽  
Work Of Breathing ◽  
Normal Subjects ◽  
Minute Volume ◽  
Oxygen Cost ◽  
Voluntary Hyperventilation ◽  
Consistent Increase ◽  
The Mean ◽  
End Tidal ◽  
End Tidal Co2

The effect of PaCOCO2 on flow resistance and on the mechanical work of ventilating the lung was studied in five normal subjects during sustained voluntary hyperventilation. Hypocapnia caused a consistent increase in flow resistance. Thus, for a minute volume of approximately 30 liters/ min the mean inspiratory flow resistance was 133% greater and the mean respiratory work of ventilating the lungs 68% greater at PaCOCO2 20–25 mm Hg compared to values at 45–50 mm Hg. End-expiratory pressure and compliance were unaffected. Atropine and isoproterenol each markedly diminished the responsiveness of the airways to low PaCOCO2 levels and, given together, blocked the effect completely. These findings could largely account for the increase in oxygen cost of breathing, and in cardiac output associated with voluntary (i.e., hypocapneic) hyperventilation. PaCOCO2; work of breathing; mechanical properties Submitted on June 24, 1963

A New Equal Area Method to Calculate and Represent Physiologic, Anatomical, and Alveolar Dead Spaces

2006 ◽  
Vol 104 (4) ◽  
pp. 696-700 ◽  
Author(s):  
Yongquan Tang ◽  
Martin J. Turner ◽  
A Barry Baker
Keyword(s):  
Carbon Dioxide ◽  
Dead Space ◽  
Graphical Method ◽  
Mean Difference ◽  
Equal Area ◽  
Area Method ◽  
Physiologic Dead Space ◽  
Anatomical Dead Space ◽  
The Mean ◽  
The Difference

Background Physiologic dead space is usually estimated by the Bohr-Enghoff equation or the Fletcher method. Alveolar dead space is calculated as the difference between anatomical dead space estimated by the Fowler equal area method and physiologic dead space. This study introduces a graphical method that uses similar principles for measuring and displaying anatomical, physiologic, and alveolar dead spaces. Methods A new graphical equal area method for estimating physiologic dead space is derived. Physiologic dead spaces of 1,200 carbon dioxide expirograms obtained from 10 ventilated patients were calculated by the Bohr-Enghoff equation, the Fletcher area method, and the new graphical equal area method and were compared by Bland-Altman analysis. Dead space was varied by varying tidal volume, end-expiratory pressure, inspiratory-to-expiratory ratio, and inspiratory hold in each patient. Results The new graphical equal area method for calculating physiologic dead space is shown analytically to be identical to the Bohr-Enghoff calculation. The mean difference (limits of agreement) between the physiologic dead spaces calculated by the new equal area method and Bohr-Enghoff equation was -0.07 ml (-1.27 to 1.13 ml). The mean difference between new equal area method and the Fletcher area method was -0.09 ml (-1.52 to 1.34 ml). Conclusions The authors' equal area method for calculating, displaying, and visualizing physiologic dead space is easy to understand and yields the same results as the classic Bohr-Enghoff equation and Fletcher area method. All three dead spaces--physiologic, anatomical, and alveolar--together with their relations to expired volume, can be displayed conveniently on the x-axis of a carbon dioxide expirogram.

Breathing in brief exercise

1960 ◽  
Vol 15 (4) ◽  
pp. 583-588 ◽  
Author(s):  
F. N. Craig ◽  
E. G. Cummings
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Respiratory Exchange Ratio ◽  
Metabolic Cost ◽  
Carbon Dioxide Tension ◽  
Minute Volume ◽  
Carbon Dioxide Output ◽  
Respiratory Minute Volume ◽  
Before And After

Two men ran for 20 or 60 seconds while inhaling air, oxygen or 4% carbon dioxide. Inspired respiratory minute volume was determined for each breath. Ventilation increased suddenly in the first breath with minimal changes in end-expiratory carbon dioxide tension and respiratory exchange ratio to a rate that remained constant for 20 seconds before increasing further. The rate of carbon dioxide output was uniform during the first 20 seconds. A 12% grade did not increase ventilation or oxygen uptake during runs of 20 seconds, but in the first minute of recovery, ventilation was 64% greater than after level runs. Inhalation of oxygen inhibited ventilation by 24% in the 20-second periods before and after the end of a 60-second run. Inhalation of carbon dioxide begun at rest produced increments in ventilation and end-expiratory carbon dioxide tension that varied little during running and recovery. In the 20-second runs ventilation varied with speed but appeared independent of ultimate metabolic cost. Submitted on January 21, 1960

Some effects of carbon dioxide on foreign gas uptake

1959 ◽  
Vol 14 (3) ◽  
pp. 333-338 ◽  
Author(s):  
Roy J. Shephard
Keyword(s):  
Carbon Dioxide ◽  
Normal Subjects ◽  
Minute Volume ◽  
Breath Holding ◽  
Analogue Computer ◽  
Diffusing Capacity ◽  
Gas Uptake ◽  
Consistent Change ◽  
The Mean ◽  
Nonuniform System

Partitional respirometry in normal subjects breathing 1-5% CO2 indicates a large increase of alveolar dead space, but in the steady state there is no consistent change of diffusing capacity or effective pulmonary blood flow. An apparent early decrease of diffusing capacity is probably an artefact due to difficulties in measuring acetylene uptake with a changing respiratory minute volume, and if Dco is measured by the breath-holding technique, carbon dioxide produces no immediate effect. Hypercapnic hyperventilation does not help in making acetylene uptake conform to a single exponential curve. The ventilatory efficiency indicated by partitional respirometry in a nonuniform system is dependent on both solubility of the test gases and the mean Va/Q ratio. An analogue computer for the solution of Va/Q problems is described. Submitted on August 18, 1958

Energy cost of eating long hay, straw and pelleted food in sport horses

1995 ◽  
Vol 61 (3) ◽  
pp. 581-588 ◽  
Author(s):  
J. Vernet ◽  
M. Vermorel ◽  
W. Martin-Rosset
Keyword(s):  
Wheat Straw ◽  
Energy Cost ◽  
Dry Matter ◽  
Energy Requirement ◽  
Ingestion Rate ◽  
Open Circuit ◽  
Metabolizable Energy ◽  
Long Form ◽  
The Mean ◽  
The Difference

AbstractSix sport horses were given 1·26 times the measured maintenance energy requirement (MEm) from each of the four following diets: H1, meadow hay in the long form (organic matter digestibility OMD = 0·541); HMI, 700g/kg the same hay and 300 g/kg pelleted maize; HSBPI, 600g/kg hay and 400g/kg pelleted dehydrated sugar-beet pulp; SCFI, 500g/kg wheat straw and 500g/kg pelleted compound food (experiment 1). In experiment 2, eight sport horses were equipped with a portable device for recording feeding behaviour and fed at 1·31 MEm diet HI (meadow hay in the long form: OMD = 0·574).Circadian energy expenditure (EE) of horses was determined by indirect calorimetry using two large open-circuit respiration chambers. Horses were continuously standing. Increase in metabolic rate (IMR) during eating was calculated from the difference between the mean EE obtained during each eatingperiod and the corresponding resting EE. The mean daily ingestion rate of hay H2 amounted to 148 (s.d. 27)mg dry matter per kg metabolic body weight per min. IMR during the two main meals averaged 0·388 (s.d. 0·059) and was not significantly different between diets H1, H2, HM1 and SCF1. Expressed per kg dry matter intake, energy cost of eating (ECE) was similar for diets H2, H1 and SCF1 but significantly lower for HSBP1 and HM1 (P<0·05). ECE of simple foods was calculated from those of the diets and of hay: proportionately 0·010, 0·042, 0·102 and 0·285 metabolizable energy intake for pelleted maize, pelleted SBP, long hay and wheat straw, respectively.

Pulmonary gas transport as influenced by a hypergravitational environment

1961 ◽  
Vol 16 (4) ◽  
pp. 641-643 ◽  
Author(s):  
Sheldon H. Steiner ◽  
Gustave C. E. Mueller ◽  
Neil S. Cherniack
Keyword(s):  
Blood Flow ◽  
Technical Assistance ◽  
Respiratory Exchange Ratio ◽  
Pulmonary Ventilation ◽  
Minute Volume ◽  
Alveolar Ventilation ◽  
Inertial Effects ◽  
Diffusing Capacity ◽  
Peripheral Arterial ◽  
Co2 Excretion

Inertial effects on pulmonary gas exchange were measured during forward acceleration at 6 and 8 g. During the 3-min-acceleration plateau, O2 uptake decreased a mean of 16 ml/min at 6 g and 71 ml/min at 8 g. CO2 excretion increased 62 ml/min at 6 g and only 30 ml/min at 8 g. The respiratory exchange ratio increased from 0.83 to 1.17 at 6 g and 1.24 at 8 g. There was a marked increase in the minute volume of ventilation. During the recovery periods, an additional 470 ml O2 was consumed; 360 ml CO2 was excreted above control values for 6 g; 650 ml O 2 was consumed; and 580 ml CO 2 was excreted for 8 g. The increased metabolic work at the g levels studied was small, representing approximately 150 ml/min O 2. The respiratory exchange ratio was well above 1.00, and a large O 2 debt accumulated. Exercise at 8 g resulted in a marked increase in O 2 uptake, which eliminated the possibility that the observed effects were caused by impaired alveolar ventilation or diffusing capacity. Cardiac output has been reported essentially unchanged or slightly increased during forward acceleration and, therefore, the response cannot be explained by a decrease in pulmonary blood flow. The evidence suggests that the diminution in O 2 exchange and impairment in CO 2 excretion represents a combination of alteration in the pulmonary ventilation to blood flow ratios and peripheral arterial shunting. Note:(With the Technical Assistance of Justin L. Taylor) Submitted on February 8, 1961

Establishing a gradient between partial pressure of arterial carbon dioxide and end-tidal carbon dioxide in patients with acute respiratory distress syndrome

2016 ◽  
Vol 65 (2) ◽  
pp. 338-341 ◽  
Author(s):  
Tariq Yousuf ◽  
Taylor Brinton ◽  
Ghulam Murtaza ◽  
Daniel Wozniczka ◽  
Khansa Ahmad ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Acute Respiratory Distress Syndrome ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Distress Syndrome ◽  
Statistical Significance ◽  
End Tidal Carbon Dioxide ◽  
The Mean ◽  
The Difference ◽  
End Tidal

End-tidal carbon dioxide (ETCO2) monitoring is useful in many situations. However, ETCO2 monitoring is unreliable in patients with acute respiratory distress syndrome (ARDS) due to widespread lung inflammation. In our study, we attempt to establish the gradient between the arterial pressure of carbon dioxide (PaCO2) and ETCO2 in patients with ARDS, which we defined as the PaETCO2 gradient. The main objective of the study was to establish a PaETCO2 gradient in each severity of ARDS. We analyzed 35 patients with ARDS and a total of 88 arterial blood gases were included. PaCO2, PaO2/FiO2 and ETCO2 were measured. Patients were stratified into mild, moderate and severe ARDS as classified by the Berlin ARDS criteria. PaCO2 and ETCO2 were compared at each severity stratification. The mean PaCO2 was 50.0, the mean ETCO2 was 26.6 and the gradient among all samples was 23.24 (±12.02). The mean gradient for each severity is as follows: mild: 19.3 (±9.9), moderate: 27.9 (±13.2) and severe: 23.9 (±7.8). The difference between the PaETCO2 gradient of the mild to moderate (p=0.001) and mild to severe groups (p=0.01) reached statistical significance. However, the difference between the moderate to severe groups did not reach statistical significance (p=0.48). We found the gradient between PaCO2 and ETCO2 in patients with ARDS is vast and tends to worsen with increasing severity of ARDS. This indicates that the gradient between the 2 may be used as an indicator of increasing severity of ARDS.

Further studies on the heat production and effective lower critical temperature of early-weaned pigs under commercial conditions of feeding and management

1984 ◽  
Vol 39 (2) ◽  
pp. 283-290 ◽  
Author(s):  
K. J. McCracken ◽  
R. Gray
Keyword(s):  
Critical Temperature ◽  
Heat Production ◽  
Thermal Conductance ◽  
Open Circuit ◽  
Weaned Pigs ◽  
Respiration Chamber ◽  
Lower Critical Temperature ◽  
The Mean ◽  
The Difference ◽  
Practical Implications

ABSTRACTIn two separate experiments pigs were weaned at 14 or 28 days and heat production was determined in an open-circuit respiration chamber at temperatures above and below the lower critical temperature (Tcl) at intervals during the post-weaning period.With 14-day weaned pigs the mean 24 h heat production above Tc1 averaged 267, 328, 474 and 554 kJ/h per m2 at 3, 9, 15 and 21 days post weaning respectively. The mean thermal conductance (H/AT, kJ/h per m2 per °ΔT, where H is total heat production, m2 is the surface area calculated as 0·097 M kg0·633 and °Δ is the difference between rectal temperature, taken at 39°, and air temperature) below TC1 was calculated as 20·5, 20·1, 23·1 and 24·2 at 17, 23, 29 and 35 days of age respectively and the corresponding values for Tc1 were 25·9, 23·0, 18·4 and 16·0°C.With 28-day weaned pigs the mean 24 h heat production above Tc1 averaged 280, 361 and 445 kJ/h per m2 at 3, 9 and 15 days post weaning. The calculated values for H/ΔT were 19·7, 20·8 and 21·6 and the corresponding values of Tcl were 24·8, 21·7, and 18·8°C at 31, 37 and 43 days of age respectively.The results are discussed in relation to previous studies on 10-day and 28-day weaned pigs and in relation to the practical implications for pigs weaned into controlled-environment accommodation.

scholarly journals The respiratory quotient in the newborn pig

1969 ◽  
Vol 23 (2) ◽  
pp. 407-413 ◽  
Author(s):  
L. E. Mount
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Consumption ◽  
Energy Metabolism ◽  
Respiratory Quotient ◽  
Carbon Dioxide Production ◽  
Mean Value ◽  
Open Circuit ◽  
Mean Values ◽  
The Mean ◽  
Environmental Temperatures

1. Rates of oxygen consumption and carbon dioxide production were measured in pigs from birth to 3 days of age in an open-circuit system.2. The mean respiratory quotient (RQ) during the first 6 h following birth was 0.95 in fasted pigs and 0.91 in pigs which were allowed to feed.3. The RQ fell during the remainder of the first postnatal day to mean values close to 0.85, whether the pigs were allowed to feed from birth or were fasted.4. From 1 to 3 days of age the RQ had a mean value of 0.79.5. There was little difference in the RQ of pigs exposed to environmental temperatures of either 32 or 16°.6. It is concluded that the baby pig is not exclusively dependent on carbohydrate for its energy metabolism.

scholarly journals Studies on diurnal variations of heat production and the effective lower critical temperature of early-weaned pigs under commercial conditions of feeding and management

1980 ◽  
Vol 43 (2) ◽  
pp. 321-328 ◽  
Author(s):  
K. J. McCracken ◽  
B. J. Caldwell
Keyword(s):  
Critical Temperature ◽  
Heat Production ◽  
Thermal Conductance ◽  
Open Circuit ◽  
Respiration Chamber ◽  
Mean Values ◽  
Maximum Value ◽  
Lower Critical Temperature ◽  
The Mean ◽  
The Difference

1. The heat production of groups of pigs, weaned at 10 d of age, was determined in an open-circuit respiration chamber at various ages between 10 and 33 d at temperatures above and below the lower critical temperature (Tcl).2. The heat production was lowest on the second or third day post weaning when pigs were given feed increasing by 25 g/pig per d from day 2. There was a marked diurnal pattern in heat production, the lowest values being recorded between 24.00 and 08.00 h.3. The mean thermal conductance (H/ΔT, kJ/h per m2 per °ΔT, where His total heat production, m2 is the surface area calculated as 0.097 W kg0.633 (Brody, 1945) and °ΔTis the difference between rectal temperature, taken as 39°, and air temperature) below Tcl was calculated as 18.0, 16.9, 18.5 and 21.2 respectively at 10, 17, 24 and 31 d of age. Maximum values of H/ΔT obtained during feeding periods were. on average, 4.5 kJ/h per me per °ΔT higher than the mean values.4. The maximum value for Tcl during the immediate post-weaning period was 25.9°. The mean Tcl at 17, 24 and 31 d were respectively 21.7, 18.4 and 18.6° for pigs fed almost to appetite.

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