Effects of elevated oxygen and carbon dioxide partial pressures on respiratory function and cognitive performance

2014 ◽  
Vol 117 (4) ◽  
pp. 406-412 ◽  
Author(s):  
Matthew Gill ◽  
Michael J. Natoli ◽  
Charles Vacchiano ◽  
David B. MacLeod ◽  
Keita Ikeda ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Respiratory Function ◽  
Vision Loss ◽  
Minute Ventilation ◽  
Cycle Ergometer ◽  
Hyperbaric Chamber ◽  
Tunnel Vision ◽  
Partial Pressures ◽  
Ergometer Exercise ◽  
End Tidal

Hyperoxia during diving has been suggested to exacerbate hypercapnic narcosis and promote unconsciousness. We tested this hypothesis in male volunteers (12 at rest, 10 at 75 W cycle ergometer exercise) breathing each of four gases in a hyperbaric chamber. Inspired Po2 (PiO2) was 0.21 and 1.3 atmospheres (atm) without or with an individual subject's maximum tolerable inspired CO2 (PiO2 = 0.055–0.085 atm). Measurements included end-tidal CO2 partial pressure (PetCO2), rating of perceived discomfort (RPD), expired minute ventilation (V̇e), and cognitive function assessed by auditory n-back test. The most prominent finding was, irrespective of PetCO2, that minute ventilation was 8–9 l/min greater for rest or exercise with a PiO2 of 1.3 atm compared with 0.21 atm ( P < 0.0001). For hyperoxic gases, PetCO2 was consistently less than for normoxic gases ( P < 0.01). For hyperoxic hypercapnic gases, n-back scores were higher than for normoxic gases ( P < 0.01), and RPD was lower for exercise but not rest ( P < 0.02). Subjects completed 66 hyperoxic hypercapnic trials without incident, but five stopped prematurely because of serious symptoms (tunnel vision, vision loss, dizziness, panic, exhaustion, or near syncope) during 69 normoxic hypercapnic trials ( P = 0.0582). Serious symptoms during hypercapnic trials occurred only during normoxia. We conclude serious symptoms with hyperoxic hypercapnia were absent because of decreased PetCO2 consequent to increased ventilation.

Validation of a new mixing chamber system for breath-by-breath indirect calorimetry

2012 ◽  
Vol 37 (1) ◽  
pp. 157-166 ◽  
Author(s):  
Do-yeon Kim ◽  
Robert Andrew Robergs
Keyword(s):  
Carbon Dioxide ◽  
Indirect Calorimetry ◽  
Human Subjects ◽  
Minute Ventilation ◽  
Cycle Ergometer ◽  
Gas Analysis ◽  
Single Subject ◽  
Ergometer Exercise ◽  
Calibration Gas ◽  
Gas Fractions

Limited validation research exists for applications of breath-by-breath systems of expired gas analysis indirect calorimetry (EGAIC) during exercise. We developed improved hardware and software for breath-by-breath indirect calorimetry (NEW) and validated this system as well as a commercial system (COM) against 2 methods: (i) mechanical ventilation with known calibration gas, and (ii) human subjects testing for 5 min each at rest and cycle ergometer exercise at 100 and 175 W. Mechanical calibration consisted of medical grade and certified calibration gas ((4.95% CO2, 12.01% O2, balance N2), room air (20.95% O2, 0.03% CO2, balance N2), and 100% nitrogen), and an air flow turbine calibrated with a 3-L calibration syringe. Ventilation was mimicked manually using complete 3-L calibration syringe manouvres at a rate of 10·min–1 from a Douglas bag reservoir of calibration gas. The testing of human subjects was completed in a counterbalanced sequence based on 5 repeated tests of all conditions for a single subject. Rest periods of 5 and 10 min followed the 100 and 175 W conditions, respectively. COM and NEW had similar accuracy when tested with known ventilation and gas fractions. However, during human subjects testing COM significantly under-measured carbon dioxide gas fractions, over-measured oxygen gas fractions and minute ventilation, and resulted in errors to each of oxygen uptake, carbon dioxide output, and respiratory exchange ratio. These discrepant findings reveal that controlled ventilation and gas fractions are insufficient to validate breath-by-breath, and perhaps even time-averaged, systems of EGAIC. The errors of the COM system reveal the need for concern over the validity of commercial systems of EGAIC.

Ventilatory and gas exchange responses to cycling with sinusoidally varying pedal rate

1978 ◽  
Vol 44 (1) ◽  
pp. 97-103 ◽  
Author(s):  
R. Casaburi ◽  
B. J. Whipp ◽  
K. Wasserman ◽  
S. N. Koyal
Keyword(s):  
Carbon Dioxide ◽  
Minute Ventilation ◽  
Small Variation ◽  
Work Load ◽  
Cycle Ergometer ◽  
Carbon Dioxide Tension ◽  
Ventilatory Responses ◽  
Constant Work Rate ◽  
Co2 Flow ◽  
End Tidal

To investigate factors controlling ventilation under conditions where the applied work load remains constant, but where hypothesized proprioceptive influences would be expected to vary, five subjects exercised at a constant work rate of 50 W on a cycle ergometer at pedaling rates which varied sinusoidally between 40 and 80 rpm. Each subject exercised continuously for 30 min at each of five sinusoidal periods. Minute ventilation (VE), carbon dioxide output (VCO2), oxygen uptake (VO2), and heart rate were computed breath-by-breath and amplitude and phase relations were extracted. We observed small fluctuations in VCO2 and VO2 engendered by varying metabolic requirements of moving the legs at varying rates. VE fluctuations were closely in phase with VCO2 and the amplitudes of the fluctuations were highly significantly correlated (r = 0.83, P less than 0.001); consequently end-tidal carbon dioxide tension fluctuations were small. Variation of pedaling rate, therefore, did not produce a ventilatory response independent of the effect of VCO2. The ventilatory responses to these forcings are inconsistent with an appreciable role for neurally mediated influences from the exercising limbs and provide further evidence that the exercise hyperpnea is linked to CO2 flow to the central circulation.

Decreased Carbon Dioxide Sensitivity in Infants of Substance-Abusing Mothers

PEDIATRICS ◽  
1995 ◽  
Vol 95 (6) ◽  
pp. 864-867
Author(s):  
Janet G. Wingkun ◽  
Janet S. Knisely ◽  
Sidney H. Schnoll ◽  
Gary R. Gutcher
Keyword(s):  
Carbon Dioxide ◽  
Tidal Volume ◽  
Minute Ventilation ◽  
Demographic Data ◽  
Substance Abusing ◽  
Quiet Sleep ◽  
Co2 Level ◽  
The Difference ◽  
End Tidal ◽  
Drug Free

Objective. To determine whether there is a demonstrable abnormality in control of breathing in infants of substance-abusing mothers during the first few days of life. Methods. We enrolled 12 drug-free control infants and 12 infants of substance abusing mothers (ISAMs). These infants experienced otherwise uncomplicated term pregnancies and deliveries. The infants were assigned to a group based on the results of maternal histories and maternal and infant urine toxicology screens. Studies were performed during quiet sleep during the first few days of life. We measured heart rate, oxygen saturations via a pulse oximeter, end-tidal carbon dioxide (ET-CO2) level, respiratory rate, tidal volume, and airflow. The chemoreceptor response was assessed by measuring minute ventilation and the ET-CO2 level after 5 minutes of breathing either room air or 4% carbon dioxide. Results. The gestational ages by obstetrical dating and examination of the infants were not different, although birth weights and birth lengths were lower in the group of ISAMs. Other demographic data were not different, and there were no differences in the infants' median ages at the time of study or in maternal use of tobacco and alcohol. The two groups had comparable baseline (room air) ET-CO2 levels, respiratory rates, tidal volumes, and minute ventilation. When compared with the group of ISAMs, the drug-free group had markedly increased tidal volume and minute ventilation on exposure to 4% carbon dioxide. These increases accounted for the difference in sensitivity to carbon dioxide, calculated as the change in minute ventilation per unit change in ET-CO2 (milliliters per kg/min per mm Hg). The sensitivity to carbon dioxide of control infants was 48.66 ± 7.14 (mean ± SE), whereas that of ISAMs was 16.28 ± 3.14. Conclusions. These data suggest that ISAMs are relatively insensitive to challenge by carbon dioxide during the first few days of life. We speculate that this reflects an impairment of the chemoreceptor response.

Ventilatory responses to carbon dioxide at low and high levels of oxygen are elevated after episodic hypoxia in men compared with women

2004 ◽  
Vol 97 (5) ◽  
pp. 1673-1680 ◽  
Author(s):  
Chris Morelli ◽  
M. Safwan Badr ◽  
Jason H. Mateika
Keyword(s):  
Carbon Dioxide ◽  
Ventilatory Response ◽  
Minute Ventilation ◽  
High Oxygen ◽  
Set Point ◽  
Ventilatory Responses ◽  
Episodic Hypoxia ◽  
Before And After ◽  
Oxygen Gas ◽  
End Tidal

We hypothesized that the acute ventilatory response to carbon dioxide in the presence of low and high levels of oxygen would increase to a greater extent in men compared with women after exposure to episodic hypoxia. Eleven healthy men and women of similar race, age, and body mass index completed a series of rebreathing trials before and after exposure to eight 4-min episodes of hypoxia. During the rebreathing trials, subjects initially hyperventilated to reduce the end-tidal partial pressure of carbon dioxide (PetCO2) below 25 Torr. Subjects then rebreathed from a bag containing a normocapnic (42 Torr), low (50 Torr), or high oxygen gas mixture (150 Torr). During the trials, PetCO2 increased while the selected level of oxygen was maintained. The point at which minute ventilation began to rise in a linear fashion as PetCO2 increased was considered to be the carbon dioxide set point. The ventilatory response below and above this point was determined. The results showed that the ventilatory response to carbon dioxide above the set point was increased in men compared with women before exposure to episodic hypoxia, independent of the oxygen level that was maintained during the rebreathing trials (50 Torr: men, 5.19 ± 0.82 vs. women, 4.70 ± 0.77 l·min−1·Torr−1; 150 Torr: men, 4.33 ± 1.15 vs. women, 3.21 ± 0.58 l·min−1·Torr−1). Moreover, relative to baseline measures, the ventilatory response to carbon dioxide in the presence of low and high oxygen levels increased to a greater extent in men compared with women after exposure to episodic hypoxia (50 Torr: men, 9.52 ± 1.40 vs. women, 5.97 ± 0.71 l·min−1·Torr−1; 150 Torr: men, 5.73 ± 0.81 vs. women, 3.83 ± 0.56 l·min−1·Torr−1). Thus we conclude that enhancement of the acute ventilatory response to carbon dioxide after episodic hypoxia is sex dependent.

Peripheral Chemoreflex Drive in Moderate-Intensity Exercise

1996 ◽  
Vol 21 (4) ◽  
pp. 285-300 ◽  
Author(s):  
Claudette M. St. Croix ◽  
David A. Cunningham ◽  
Donald H. Paterson ◽  
John M. Kowalchuk
Keyword(s):  
Peak Level ◽  
Cycle Ergometer ◽  
Open Loop ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Peripheral Chemoreceptor ◽  
Carotid Bodies ◽  
Ergometer Exercise ◽  
End Tidal ◽  
Peripheral Chemoreflex

The purpose of this study was to measure the contribution of the peripheral chemoreceptor (pRc) to [Formula: see text] during the steady-state of moderate-intensity cycle ergometer exercise using continuous hyperoxic suppression of pRc drive, while stabilizing the drive from the central chemoreceptor by clamping end-tidal PCO2 (PETCO2) at the peak level attained during the hyperoxic period of a poikilocapnic ride. In the isocapnic protocol, the PETCO2 was maintained at a constant level by a negative feedback, open loop system. Five subjects completed four repetitions of each of the poikilocapnic and isocapnic protocols. In the poikilocapnic protocol, [Formula: see text] declined following the step into hyperoxia and then began to increase, whereas the decline in [Formula: see text] was maintained in the isocapnic protocol. However, the mean decrease in [Formula: see text] was not significantly different between the poikilocapnic (16.1 ± 5.0%) and isocapnic (14.9 ± 4.4%) protocols. These results suggest that the declining phase of [Formula: see text] is fully complete before the secondary central stimulating actions of hyperoxia on [Formula: see text] and that the pRc contributes about 15% of the drive to breathe in moderate intensity exercise. Key words: ventilatory control, carotid bodies, hyperoxia

scholarly journals Dynamic Forcing of End-Tidal Carbon Dioxide and Oxygen Applied to Functional Magnetic Resonance Imaging

2007 ◽  
Vol 27 (8) ◽  
pp. 1521-1532 ◽  
Author(s):  
Richard G Wise ◽  
Kyle TS Pattinson ◽  
Daniel P Bulte ◽  
Peter A Chiarelli ◽  
Stephen D Mayhew ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Blood Oxygenation ◽  
Dynamic Responses ◽  
Bold Signal ◽  
Tidal Forcing ◽  
Partial Pressures ◽  
Oxygenation Level ◽  
Mri Environment ◽  
Dynamic Forcing ◽  
End Tidal

Investigations into the blood oxygenation level-dependent (BOLD) functional MRI signal have used respiratory challenges with the aim of probing cerebrovascular physiology. Such challenges have altered the inspired partial pressures of either carbon dioxide or oxygen, typically to a fixed and constant level (fixed inspired challenge (FIC)). The resulting end-tidal gas partial pressures then depend on the subject's metabolism and ventilatory responses. In contrast, dynamic end-tidal forcing (DEF) rapidly and independently sets end-tidal oxygen and carbon dioxide to desired levels by altering the inspired gas partial pressures on a breath-by-breath basis using computer-controlled feedback. This study implements DEF in the MRI environment to map BOLD signal reactivity to CO2. We performed BOLD (T2*) contrast FMRI in four healthy male volunteers, while using DEF to provide a cyclic normocapnichypercapnic challenge, with each cycle lasting 4 mins (PetCO2 mean±s.d., from 40.9 ± 1.8 to 46.4 ± 1.6 mm Hg). This was compared with a traditional fixed-inspired (FiCO2 = 5%) hypercapnic challenge (PetCO2 mean±s.d., from 38.2 ± 2.1 to 45.6 ± 1.4 mm Hg). Dynamic end-tidal forcing achieved the desired target PetCO2 for each subject while maintaining PetCO2 constant. As a result of CO2-induced increases in ventilation, the FIC showed a greater cyclic fluctuation in PetCO2. These were associated with spatially widespread fluctuations in BOLD signal that were eliminated largely by the control of PetCO2 during DEF. The DEF system can provide flexible, convenient, and physiologically well-controlled respiratory challenges in the MRI environment for mapping dynamic responses of the cerebrovasculature.

Computer-based system for analysis of respiratory responses to exercise

1977 ◽  
Vol 42 (6) ◽  
pp. 968-975 ◽  
Author(s):  
D. H. Pearce ◽  
H. T. Milhorn ◽  
G. H. Holloman ◽  
W. J. Reynolds
Keyword(s):  
Carbon Dioxide ◽  
Respiratory Exchange Ratio ◽  
Minute Ventilation ◽  
Type System ◽  
Work Load ◽  
Magnetic Type ◽  
Computer Based ◽  
End Tidal ◽  
Good Agreement

A computer-based system for the determination of tidal volume, respiratory frequency, minute ventilation, oxygen transfer, carbon dioxide transfer, respiratory exchange ratio, end-tidal oxygen, end-tidal carbon dioxide, and heart rate is presented. These variables are first determined on a breath-by-breath basis from data (expired carbon dioxide and oxygen fractions, airflow, and ECG) prerecorded on an FM magnetic type system. The breath-by-breath data are then averaged for each experimental run in 5-s increments. The 5-s increment data from a group of subjects can then be averaged and the SEM determined at prescribed periods of time. For the study of individual respiratory transient we found the 5-s increment data to be more useful than the breath-by-breath data because it has a lesser degree of fluctuation. The system is especially adapted to careful observation of the responses within the first few seconds of a change in work load. Appropriate computer programs are discussed. The results of several experiments are compared with data from other sources and found to be in good agreement.

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