Pulmonary gas exchange in diving

2009 ◽  
Vol 106 (2) ◽  
pp. 668-677 ◽  
Author(s):  
R. E. Moon ◽  
A. D. Cherry ◽  
B. W. Stolp ◽  
E. M. Camporesi
Keyword(s):  
Gas Phase ◽  
Mechanical Load ◽  
Work Of Breathing ◽  
Volume Ratio ◽  
Inert Gas ◽  
Respiratory Drive ◽  
Gas Density ◽  
Airways Resistance ◽  
Per Se ◽  
Related Increase

Diving-related pulmonary effects are due mostly to increased gas density, immersion-related increase in pulmonary blood volume, and (usually) a higher inspired Po2. Higher gas density produces an increase in airways resistance and work of breathing, and a reduced maximum breathing capacity. An additional mechanical load is due to immersion, which can impose a static transrespiratory pressure load as well as a decrease in pulmonary compliance. The combination of resistive and elastic loads is largely responsible for the reduction in ventilation during underwater exercise. Additionally, there is a density-related increase in dead space/tidal volume ratio (Vd/Vt), possibly due to impairment of intrapulmonary gas phase diffusion and distribution of ventilation. The net result of relative hypoventilation and increased Vd/Vt is hypercapnia. The effect of high inspired Po2 and inert gas narcosis on respiratory drive appear to be minimal. Exchange of oxygen by the lung is not impaired, at least up to a gas density of 25 g/l. There are few effects of pressure per se, other than a reduction in the P50 of hemoglobin, probably due to either a conformational change or an effect of inert gas binding.

scholarly journals The effect of inert gas choice on multiple breath washout in healthy infants: differences in lung function outcomes and breathing pattern

2017 ◽  
Vol 123 (6) ◽  
pp. 1545-1554 ◽  
Author(s):  
Per M. Gustafsson ◽  
Lovisa Bengtsson ◽  
Anders Lindblad ◽  
Paul D. Robinson
Keyword(s):  
Functional Residual Capacity ◽  
Sulfur Hexafluoride ◽  
Breathing Pattern ◽  
Inert Gas ◽  
Respiratory Drive ◽  
Quiet Sleep ◽  
Lung Clearance ◽  
Healthy Infants ◽  
Lung Clearance Index ◽  
Residual Capacity

The detrimental effects on breathing pattern during multiple breath inert gas washout (MBW) have been described with different inhaled gases [100% oxygen (O2) and sulfur hexafluoride (SF6)] but detailed comparisons are lacking. N2- and SF6-based tests were performed during spontaneous quiet sleep in 10 healthy infants aged 0.7–1.3 yr using identical hardware. Differences in breathing pattern pre and post 100% O2 and 4% SF6 exposure were investigated, and the results obtained were compared [functional residual capacity (FRC) and lung clearance index (LCI)]. During 100% O2 exposure. mean inspiratory flow (“respiratory drive”) decreased transiently by mean (SD) 28 (9)% ( P < 0.001), and end-tidal CO2 (carbon dioxide) increased by mean (SD) 0.3 (0.4)% units ( P < 0.05) vs. air breathing prephase. During subsequent N2 washin (i.e., recovery phase), the pattern of change reversed. No significant effect on breathing pattern was observed during SF6 testing. In vitro testing confirmed that technical artifacts did not explain these changes. Mean (SD) FRC and LCI in vivo were significantly higher with N2 vs. SF6 washout: 216 (33) vs. 186 (22) ml ( P < 0.001) and 8.25 (0.85) vs. 7.55 (0.57) turnovers ( P = 0.021). Based on these results, SF6 based MBW is the preferred methodology for tests in this age range. NEW & NOTEWORTHY Inert gas choice for multiple breath inert gas washout (MBW) in infants has important consequences on both breathing pattern during test performance and the functional residual capacity and lung clearance index values obtained. Data suggest the detrimental effect of breathing pattern of 100% O2 and movement of O2 across the alveolar capillary membrane, with direct effects on MBW outcomes. SF6 MBW during infancy avoids this and can be further optimized by addressing the sources of technical artifact identified in this work.

scholarly journals Mechanisms of exercise intolerance in Global Initiative for Chronic Obstructive Lung Disease grade 1 COPD

2014 ◽  
Vol 44 (5) ◽  
pp. 1177-1187 ◽  
Author(s):  
Jordan A. Guenette ◽  
Roberto C. Chin ◽  
Sicheng Cheng ◽  
Paolo B. Dominelli ◽  
Natya Raghavan ◽  
...  
Keyword(s):  
Work Of Breathing ◽  
Pressure Ratio ◽  
Chronic Obstructive Lung Disease ◽  
Exercise Intolerance ◽  
Chronic Obstructive ◽  
Respiratory Drive ◽  
Obstructive Pulmonary Disease ◽  
Transdiaphragmatic Pressure ◽  
Generating Capacity ◽  
Neuromuscular Abnormalities

The purpose of this study was to determine if a dissociation existed between respiratory drive, as estimated by diaphragmatic electromyography (EMGdi), and its pressure-generating capacity during exercise in mild chronic obstructive pulmonary disease (COPD) and whether this, if present, had negative sensory consequences.Subjects meeting spirometric criteria for mild COPD (n=16) and age and sex-matched controls (n=16) underwent detailed pulmonary function testing and a symptom limited cycle test while detailed ventilatory, sensory and respiratory mechanical responses were measured.Compared with controls, subjects with mild COPD had greater ventilatory requirements throughout submaximal exercise. At the highest equivalent work rate of 60 W, they had a significantly higher: total work of breathing (32±17 versus 16±7 J·min−1; p<0.01); EMGdi (37.3±17.3 versus 17.9±11.7% of maximum; p<0.001); and EMGdi to transdiaphragmatic pressure ratio (0.87±0.38 versus 0.52±0.27; p<0.01). Dyspnoea–ventilation slopes were significantly higher in mild COPD than controls (0.17±0.12 versus 0.10±0.05; p<0.05). However, absolute dyspnoea ratings reached significant levels only at high levels of ventilation.Increased respiratory effort and work of breathing, and a wider dissociation between diaphragmatic activation and pressure-generating capacity were found at standardised work rates in subjects with mild COPD compared with controls. Despite these mechanical and neuromuscular abnormalities, significant dyspnoea was only experienced at higher work rates.

The thermal decompositions of carbamates. I. Ethyl N-Methyl-N-phenylcarbamate

1971 ◽  
Vol 24 (12) ◽  
pp. 2541 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Rate Constants ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
First Order ◽  
Order Rate

Ethyl N-methyl-N-phenylcarbamate decomposes in the gas phase over the range 329-380� to give N-methylaniline, carbon dioxide, and ethylene. The reaction is quantitative, and is first order in the carbamate. First-order rate constants are described by the equation ������������������� k1 = 1012.44 exp(-45,380/RT) (s-1) and are unaffected by the addition of cyclohexene or by increase in the surface to volume ratio of the reaction vessel. The reaction is considered to be unimolecular and likely to proceed by means of a mechanism of the type represented by the pyrolyses of acetates, xanthates, and carbonates.

Pulmonary Effects of Sustained Periods of High-G Acceleration Relevant to Suborbital Spaceflight

2021 ◽  
Vol 92 (8) ◽  
pp. 633-641
Author(s):  
Ross D. Pollock ◽  
Caroline J. Jolley ◽  
Nadia Abid ◽  
John H. Couper ◽  
Luis Estrada-Petrocelli ◽  
...  
Keyword(s):  
Work Of Breathing ◽  
Arterial Oxygen Saturation ◽  
Regional Distribution ◽  
Blood Gases ◽  
Respiratory Physiology ◽  
Arterial Oxygen ◽  
Relative Distribution ◽  
Respiratory Drive ◽  
Impedance Tomography ◽  
Arterial Blood

AbstractBACKGROUND: Members of the public will soon be taking commercial suborbital spaceflights with significant Gx (chest-to-back) acceleration potentially reaching up to 6 Gx. Pulmonary physiology is gravity-dependent and is likely to be affected, which may have clinical implications for medically susceptible individuals.METHODS: During 2-min centrifuge exposures ranging up to 6 Gx, 11 healthy subjects were studied using advanced respiratory techniques. These sustained exposures were intended to allow characterization of the underlying pulmonary response and did not replicate actual suborbital G profiles. Regional distribution of ventilation in the lungs was determined using electrical impedance tomography. Neural respiratory drive (from diaphragm electromyography) and work of breathing (from transdiaphragmatic pressures) were obtained via nasoesophageal catheters. Arterial blood gases were measured in a subset of subjects. Measurements were conducted while breathing air and breathing 15 oxygen to simulate anticipated cabin pressurization conditions.RESULTS: Acceleration caused hypoxemia that worsened with increasing magnitude and duration of Gx. Minimum arterial oxygen saturation at 6 Gx was 86 1 breathing air and 79 1 breathing 15 oxygen. With increasing Gx the alveolar-arterial (A-a) oxygen gradient widened progressively and the relative distribution of ventilation reversed from posterior to anterior lung regions with substantial gas-trapping anteriorly. Severe breathlessness accompanied large progressive increases in work of breathing and neural respiratory drive.DISCUSSION: Sustained high-G acceleration at magnitudes relevant to suborbital flight profoundly affects respiratory physiology. These effects may become clinically important in the most medically susceptible passengers, in whom the potential role of centrifuge-based preflight evaluation requires further investigation.Pollock RD, Jolley CJ, Abid N, Couper JH, Estrada-Petrocelli L, Hodkinson PD, Leonhardt S, Mago-Elliott S, Menden T, Rafferty G, Richmond G, Robbins PA, Ritchie GAD, Segal MJ, Stevenson AT, Tank HD, Smith TG. Pulmonary effects of sustained periods of high-G acceleration relevant to suborbital spaceflight. Aerosp Med Hum Perform. 2021; 92(7):633641.

Subcutaneous tissue gas space pressure during superficial isobaric counterdiffusion

1979 ◽  
Vol 47 (1) ◽  
pp. 224-227 ◽  
Author(s):  
J. R. Cowley ◽  
C. Allegra ◽  
C. J. Lambertsen
Keyword(s):  
Gas Phase ◽  
Subcutaneous Tissue ◽  
Inert Gas ◽  
Maximum Pressure ◽  
Tissue Pressure ◽  
Phase Development ◽  
New Zealand White Rabbits ◽  
Gas Space ◽  
Pressure Changes ◽  
Mean Time

Changes in subcutaneous tissue pressure caused by N2O-He, 1-ATA isobaric counterdiffusion gas phase development were measured. Only the ears of New Zealand White rabbits were subjected to counterdiffusion. The rabbits breathed a mixture of 80% N2O-20% O2 while their ears alone were surrounded by He and the rest of their bodies continued to be surrounded by air. Subcutaneous pressure changes were transmitted to the transducer-recorded system via a fluid-filled subcutaneous needle. When the gas phase developed in subcutaneous tissue, pressure rose and a maximum pressure (Pmax) was reached. Pmax in the counterdiffused ear was 48 +/- 10 (SD) Torr, and mean time to reach Pmax was 75 +/- 10 (SD) min. The findings are discussed in relation to the pathological processes of isobaric inert gas counterdiffusion.

Diminishing airways resistance and work of breathing by a novel design of the paediatric endotracheal tube

2006 ◽  
Vol 39 ◽  
pp. S589 ◽  
Author(s):  
B. Stankiewicz ◽  
M. Darowski ◽  
J. Glapinski ◽  
M. Rawicz ◽  
M. Michnikowski ◽  
...  
Keyword(s):  
Endotracheal Tube ◽  
Work Of Breathing ◽  
Airways Resistance ◽  
Novel Design

Effect of surface on the gas-phase oxidation of methanol catalysed by nitric oxide

1964 ◽  
Vol 17 (5) ◽  
pp. 539
Author(s):  
JJ Batten
Keyword(s):  
Nitric Oxide ◽  
Gas Phase ◽  
Marked Effect ◽  
Volume Ratio ◽  
Oxidation Of Methanol ◽  
Inorganic Substances ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Kinetics Of ◽  
Effect Of Surface

A study has been made of the effect of the surface-to-volume ratio of the reaction vessel and of coatings of various inorganic substances on the vessel walls on the gas-phase oxidation of methanol catalysed by nitric oxide. The results show that, whereas packing the vessel does not have a marked effect on the rate, the kinetics of the reaction are profoundly influenced by the nature of the surface. The results suggest that the methanol-oxidation chains are initiated at the surface by reaction between methanol and nitrogen dioxide, and that HO2 radicals play an important role in the subsequent chain reaction.

Einfluß der Strömungsform des Gases auf die chemischen Transportprozesse in Halogenglühlampen

1974 ◽  
Vol 29 (10) ◽  
pp. 1471-1477
Author(s):  
Gerhard M. Neumann
Keyword(s):  
High Pressure ◽  
Laminar Flow ◽  
Gas Phase ◽  
Flow Separation ◽  
Gas Flow ◽  
Chemical Transport ◽  
Transport Processes ◽  
Inert Gas ◽  
Good Accord ◽  
Incandescent Lamps

Abstract By raising the inert gas pressure and thus changing the type of gas flow chemical transport processes in tubular halogen incandescent lamps may be influenced. At medium pressures in the region of laminar flow separation of halogen and inert gas due to thermodiffusion occurs, the halogen cycle breaks down, and bulb blackening of the lamp is observed. At low and high pressure, where the streaming behaviour of the gas phase is dominated by diffusion or turbulence, separation of halogen and inert gas is overcome and the lamps stay clean. Observed pressures for changing from laminar to turbulent flow are 3.5 atm in xenon, 5.5 atm in krypton, and > 8 atm in argon in good accord with the well-known Reynolds' criterion.

The Langmuir-Hinshelwood Reaction between Oxygen and CO at Ir(111) Surfaces

1979 ◽  
Vol 34 (1) ◽  
pp. 81-88 ◽  
Author(s):  
J. Küppers ◽  
A. Plagge
Keyword(s):  
Activation Energy ◽  
Computer Program ◽  
Apparent Activation Energy ◽  
Gas Phase ◽  
Close Agreement ◽  
Reaction Path ◽  
Kcal Mole ◽  
Reaction Step ◽  
Per Se ◽  
Reaction Processes

Abstract The reaction of oxygen and CO to form CO2 has been investigated using an Ir (111) surface as an acting catalyst. Both instationary and stationary reaction processes have been established via separate gas exposing techniques. The instationary reaction process, achieved from coadsorbed CO and O which per se is an LH reaction is found to be controlled by an apparent activation energy of 10.7 kcal/mole. The stationary reaction with both CO and O2 continuously present in the gas phase has been simulated using a proper computer program, involving both LH and ER reaction steps. By comparison with experimental results, close agreement is found when ruling out any ER reaction step from the reaction path.

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