scholarly journals The pattern of breathing following step changes of alveolar partial pressures of carbon dioxide and oxygen in man

1980 ◽  
Vol 300 (1) ◽  
pp. 55-73 ◽  
Author(s):  
W. N. Gardner
Keyword(s):  
Carbon Dioxide ◽  
Partial Pressures

Inspiratory Speech as a Management Option for Spastic Dysphonia

1992 ◽  
Vol 101 (5) ◽  
pp. 375-382 ◽  
Author(s):  
Gordon A. Harrison ◽  
Richard H. Troughear ◽  
Pamela J. Davis ◽  
Alison L. Winkworth
Keyword(s):  
Carbon Dioxide ◽  
Gas Exchange ◽  
Voice Quality ◽  
Management Option ◽  
Communication Problems ◽  
Partial Pressures ◽  
The Subject ◽  
And Control ◽  
Laryngeal Resistance

A case study is reported of a subject who has used inspiratory speech (IS) for 6 years as a means of overcoming the communication problems of long-standing adductor spastic dysphonia (ASD). The subject was studied to confirm his use of IS, determine the mechanisms of its production, investigate its effects on ventilatory gas exchange, and confirm that it was perceptually preferable to ASD expiratory speech (ES). Results showed that the production and control of a high laryngeal resistance to airflow were necessary for usable IS. Voice quality was quantitatively and perceptually poor; however, the improved fluency and absence of phonatory spasm made IS the preferred speaking mode for both the listener and the speaker. Transcutaneous measurements of the partial pressures of oxygen and carbon dioxide in the subject's blood were made during extended speaking periods. These measurements indicated that ventilation was unchanged during IS, and that ventilation during ES was similar to the “hyperventilation” state of normal speakers. The reasons for the absence of phonatory spasm during IS are discussed, and the possibility of its use as a noninvasive management option for other ASD sufferers is addressed.

scholarly journals The Active Transport of Oxygen and Carbon Dioxide into the Swim-Bladder of Fish

1966 ◽  
Vol 49 (6) ◽  
pp. 1209-1220 ◽  
Author(s):  
H.J. KUHN ◽  
E. MARTI
Keyword(s):  
Carbon Dioxide ◽  
Lactic Acid ◽  
Active Transport ◽  
Bladder Pressure ◽  
Swim Bladder ◽  
Rete Mirabile ◽  
Partial Pressures ◽  
Gas Gland ◽  
Counter Current ◽  
Good Agreement

The active transport of oxygen and carbon dioxide into the swim-bladder of fish is discussed. The rete mirabile is a capillary network which is involved in the gas secretion into the bladder. The rete is regarded as a counter-current multiplier. Lactic acid which is produced in the gas gland generates in the rete single concentrating effects for oxygen and carbon dioxide; i.e., for equal partial pressures the concentrations of the gases in the afferent rete capillaries are higher than those in the efferent ones. The single concentrating effects were calculated from measurements of sea robin blood (Root, 1931). The multiplication of these effects within the rete for different rete lengths and different transport rates was numerically evaluated. The calculated O2 and CO2 pressures in the bladder are in good agreement with the experimental results of Scholander and van Dam (1953). The descent velocities at equilibrium between bladder pressure and hydrostatic pressure are discussed for fishes with different rete lengths.

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.

Gas Exchange

2017 ◽  
Author(s):  
John W. Kreit
Keyword(s):  
Carbon Dioxide ◽  
Gas Exchange ◽  
Partial Pressure ◽  
Capillary Blood ◽  
Pressure Gradients ◽  
Arterial Blood ◽  
Pulmonary Capillary ◽  
Partial Pressures ◽  
Pulmonary Capillary Blood ◽  
And Diffusion

Gas Exchange explains how four processes—delivery of oxygen, excretion of carbon dioxide, matching of ventilation and perfusion, and diffusion—allow the respiratory system to maintain normal partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) in the arterial blood. Partial pressure is important because O2 and CO2 molecules diffuse between alveolar gas and pulmonary capillary blood and between systemic capillary blood and the tissues along their partial pressure gradients, and diffusion continues until the partial pressures are equal. Ventilation is an essential part of gas exchange because it delivers O2, eliminates CO2, and determines ventilation–perfusion ratios. This chapter also explains how and why abnormalities in each of these processes may reduce PaO2, increase PaCO2, or both.

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