Specific ventilation distribution in microgravity

1996 ◽  
Vol 80 (5) ◽  
pp. 1458-1465 ◽  
Author(s):  
S. Verbanck ◽  
D. Linnarsson ◽  
G. K. Prisk ◽  
M. Paiva
Keyword(s):  
Functional Residual Capacity ◽  
Compartmental Model ◽  
Gas Mixtures ◽  
Inert Gas ◽  
Ventilation Distribution ◽  
Model Simulations ◽  
Test Gas ◽  
Residual Capacity

We studied the contribution of inter- and intraregional inhomogeneities of specific ventilation (delta V/Vo) from the rebreathing inert gas trace in microgravity and on Earth. The rebreathing tests were carried out by four astronauts before, during, and after the 10-day Spacelab D-2 mission. Starting from functional residual capacity, the rebreathing maneuver consisted of eight reinspirations from a bag filled with 1.8-2.2 liters of test gas mixtures containing approximately 5% argon. The rate of argon equilibration in the rebreathing bag, termed RBeq, was quantified by determining the logarithm of the actual minus the equilibrated argon concentrations normalized to the inspired minus the equilibrated argon concentrations. A compartmental model of the lung (S. Verbanck and M. Paiva. J. Appl. Physiol. 76: 445-454, 1994) was used to validate the method for determining RBeq and to simulate the influence of intra- and interregional delta V/Vo inhomogeneities on the RBeq curve. The comparison between the experimental Earth-based and microgravity RBeq curves and model simulations shows that gravity-independent delta V/Vo inhomogeneity is at least as large as gravity-dependent delta V/Vo inhomogeneity.

Inter- and intraregional ventilation inhomogeneity in hypergravity and after pressurization of an anti-G suit

2003 ◽  
Vol 94 (4) ◽  
pp. 1353-1364 ◽  
Author(s):  
Mikael Grönkvist ◽  
Eddie Bergsten ◽  
Ola Eiken ◽  
Per M. Gustafsson
Keyword(s):  
Functional Residual Capacity ◽  
Inert Gas ◽  
Phase Iii ◽  
Ventilation Distribution ◽  
Ventilation Inhomogeneity ◽  
Gas Trapping ◽  
Residual Capacity ◽  
Trapped Gas ◽  
Phase Iii Slope

This study assessed the effects of increased gravity in the head-to-foot direction (+Gz) and anti-G suit (AGS) pressurization on functional residual capacity (FRC), the volume of trapped gas (VTG), and ventilation distribution by using inert- gas washout. Normalized phase III slope ( SnIII) analysis was used to determine the effects on inter- and intraregional ventilation inhomogeneity. Twelve men performed multiple-breath washouts of SF6 and He in a human centrifuge at +1 to +3 Gzwearing an AGS pressurized to 0, 6, or 12 kPa. Hypergravity produced moderately increased FRC, VTG, and overall and inter- and intraregional inhomogeneities. In normogravity, AGS pressurization resulted in reduced FRC and increased VTG, overall, and inter- and intraregional inhomogeneities. Inflation of the AGS to 12 kPa at +3 Gz reduced FRC markedly and caused marked gas trapping and intraregional inhomogeneity, whereas interregional inhomogeneity decreased. In conclusion, increased +Gzimpairs ventilation distribution not only between widely separated lung regions, but also within small lung units. Pressurizing an AGS in hypergravity causes extensive gas trapping accompanied by reduced interregional inhomogeneity and, apparently, results in greater intraregional inhomogeneity.

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.

A deeper level of ketamine anesthesia does not affect functional residual capacity and ventilation distribution in healthy preschool children

2007 ◽  
Vol 17 (12) ◽  
pp. 1150-1155 ◽  
Author(s):  
BRITTA S VON UNGERN-STERNBERG ◽  
ADRIAN REGLI ◽  
FRANZ J. FREI ◽  
EVA-MARIA JORDI RITZ ◽  
JÜRG HAMMER ◽  
...  
Keyword(s):  
Preschool Children ◽  
Functional Residual Capacity ◽  
Ventilation Distribution ◽  
Ketamine Anesthesia ◽  
Residual Capacity

scholarly journals Effect of cardiopulmonary bypass and aortic clamping on functional residual capacity and ventilation distribution in children

2007 ◽  
Vol 134 (5) ◽  
pp. 1193-1198 ◽  
Author(s):  
Britta S. von Ungern-Sternberg ◽  
Ferenc Petak ◽  
Sonja Saudan ◽  
Michel Pellegrini ◽  
Thomas O. Erb ◽  
...  
Keyword(s):  
Cardiopulmonary Bypass ◽  
Functional Residual Capacity ◽  
Ventilation Distribution ◽  
Aortic Clamping ◽  
Residual Capacity

Decrease of Functional Residual Capacity and Ventilation Homogeneity after Meeting Abstracts in Anesthetized Young Infants and Preschool Children

2006 ◽  
Vol 105 (4) ◽  
pp. 670-675 ◽  
Author(s):  
Britta S. von Ungern-Sternberg ◽  
Jürg Hammer ◽  
Andreas Schibler ◽  
Franz J. Frei ◽  
Thomas O. Erb
Keyword(s):  
Preschool Children ◽  
Neuromuscular Blockade ◽  
Functional Residual Capacity ◽  
Pulmonary Mechanics ◽  
Ventilation Distribution ◽  
Lung Clearance ◽  
Young Infants ◽  
Lung Clearance Index ◽  
Residual Capacity ◽  
The Impact

Background Based on age-dependent differences in pulmonary mechanics, the effect of neuromuscular blockade may differ in infants compared with older children. The aim of this study was to determine the impact of neuromuscular blockade and its reversal by positive end-expiratory pressure (PEEP) on functional residual capacity (FRC) and ventilation distribution in young infants and preschool children. Methods The authors studied 14 infants (aged 0-6 months) and 25 preschool children (aged 2-6 yr). FRC and lung clearance index were calculated. Measurements were taken (1) after intubation, (2) during neuromuscular blockade, and (3) during neuromuscular blockade plus application of PEEP (3 cm H2O). Results Functional residual capacity (mean +/- SD) decreased from 21.3 +/- 4.7 ml/kg to 12.2 +/- 4.8 ml/kg (P &lt; 0.001) during neuromuscular blockade in infants and from 25.6 +/- 5.9 ml/kg to 23.0 +/- 5.3 ml/kg (P &lt; 0.001) in preschool children. With the application of PEEP, FRC increased to 22.3 +/- 5.9 ml/kg (P = 0.4829, compared with baseline) in infants and 28.2 +/- 5.8 ml/kg (P &lt; 0.001) in children. The lung clearance index increased after neuromuscular blockade, whereas baseline values were regained after the application of PEEP. The changes induced by neuromuscular blockade were significantly greater in infants compared with preschool children (P &lt; 0.001). Conclusions Although the use of neuromuscular blockade decreased FRC and ventilation distribution substantially in both groups, the changes were more pronounced in young infants. With PEEP, FRC increased and ventilation homogeneity was restored. These results provide a rationale to use PEEP in anesthetized, paralyzed infants and children.

Decrease in functional residual capacity during sleep in normal humans

1984 ◽  
Vol 57 (5) ◽  
pp. 1319-1322 ◽  
Author(s):  
D. W. Hudgel ◽  
P. Devadatta
Keyword(s):  
Functional Residual Capacity ◽  
Closed System ◽  
Rem Sleep ◽  
Airflow Limitation ◽  
Ventilation Distribution ◽  
Stage 2 Sleep ◽  
Residual Capacity ◽  
Helium Dilution ◽  
Normal Humans ◽  
Healthy Males

A decrease in functional residual capacity (FRC) during sleep could result in worsening of ventilation distribution contributing to sleep hypoxemia. Therefore the purpose of this study was to determine whether FRC does decrease and to what extent it decreases in normal humans during sleep. Using helium dilution in a closed system we measured FRC in 10 healthy males during wakefulness, stage 2, stages 3–4, and rapid-eye-movement (REM) sleep. Mean FRC decreased from 3.14 +/- 0.01 (SE) liters during wakefulness to 2.95 +/- 0.01 liters in stage 2 sleep. Lowest sleep values were 2.86 +/- 0.01 liters in stages 3–4 and 2.83 +/- 0.01 liters in REM sleep (P less than 0.05 from wakefulness). Although the amount of the decrease in FRC identified during sleep was surely not large enough to impair ventilation distribution in normal humans, this degree of decrease might contribute to the hypoxemia seen in patients with severe airflow limitation.

scholarly journals Validation of a Photoacoustic Gas Analyser for the Measurement of Functional Residual Capacity Using Multiple-Breath Inert Gas Washout

Respiration ◽  
2014 ◽  
Vol 87 (6) ◽  
pp. 462-468 ◽  
Author(s):  
Sherif Gonem ◽  
Florian Singer ◽  
Steven Corkill ◽  
Amisha Singapuri ◽  
Salman Siddiqui ◽  
...  
Keyword(s):  
Functional Residual Capacity ◽  
Inert Gas ◽  
Residual Capacity
Sign in / Sign up

Export Citation Format

Share Document