Effect of catheter flow direction on CO2 removal during tracheal gas insufflation in dogs

1993 ◽  
Vol 75 (3) ◽  
pp. 1238-1246 ◽  
Author(s):  
A. Nahum ◽  
S. A. Ravenscraft ◽  
G. Nakos ◽  
A. B. Adams ◽  
W. C. Burke ◽  
...  
Keyword(s):  
Dead Space ◽  
Flow Direction ◽  
Co2 Removal ◽  
Arterial Pco2 ◽  
Mechanically Ventilated ◽  
Tracheal Gas Insufflation ◽  
Catheter Tip ◽  
A Minor ◽  
Conducting Airways ◽  
Co2 Elimination

Tracheal gas insufflation (TGI) improves the efficiency of CO2 elimination by replacing CO2 in the anatomic dead space proximal to the catheter tip with fresh gas during expiration. Turbulence generated by gas exiting the catheter tip may also contribute to alveolar ventilation. To separate distal (turbulence-related) and proximal (washout of dead space) effects of TGI, we compared the efficacy of a straight and an inverted catheter during continuous and expiratory TGI in six mechanically ventilated dogs. We reasoned that the inverted catheter cannot improve CO2 elimination from more distal conducting airways. During continuous TGI with the straight catheter, arterial PCO2 (PaCO2) decreased significantly from baseline (without TGI) of 56 +/- 10 Torr to 38 +/- 8, 36 +/- 8, and 35 +/- 8 Torr at catheter flow rates (Vcath) of 5, 10, and 15 l/min, respectively. For the same conditions, PaCO2 was always higher (P < 0.001) with the inverted catheter (42 +/- 10, 41 +/- 10, and 41 +/- 10 Torr). PaCO2 was lower with the straight (40 +/- 9 Torr) than with the inverted catheter (44 +/- 10 Torr, P < 0.001) during TGI delivered only during expiration at a Vcath of 10 l/min. End-expiratory lung volume relative to baseline increased during continuous, but not during expiratory, TGI and was significantly greater with the straight than with the inverted catheter (P < 0.0001). Our data confirm that the primary mechanism of TGI is expiratory washout of the proximal anatomic dead space but also suggest a minor contribution of turbulence beyond the tip of the straight catheter.

Distal effects of tracheal gas insufflation: changes with catheter position and oleic acid lung injury

1996 ◽  
Vol 81 (3) ◽  
pp. 1121-1127 ◽  
Author(s):  
A. Nahum ◽  
S. A. Ravenscraft ◽  
A. B. Adams ◽  
J. J. Marini
Keyword(s):  
Oleic Acid ◽  
Lung Injury ◽  
Dead Space ◽  
Minute Ventilation ◽  
Catheter Position ◽  
Tracheal Gas Insufflation ◽  
Before And After ◽  
Dead Space Volume ◽  
Catheter Tip ◽  
Conducting Airways

We separated distal (turbulence-related) and proximal (dead space washout-related) effects of tracheal gas insufflation (TGI) by comparing the effects of straight and inverted catheters. We reasoned that the inverted catheter was unlikely to remove CO2 from conducting airways distal to its orifice. In six normal dogs during TGI at 10 l/min, advancing the catheters from 10 to 1 cm above the main carina decreased dead space volume by 29 +/- 12 and 12 +/- 6 ml (P < 0.04) with the straight and inverted catheters, respectively. By comparison, the tracheal volume between 10 and 1 cm above the carina was 15 +/- 2 ml. In another set of dogs (n = 5), we examined the distal effects of TGI before and after oleic acid-induced lung injury. During TGI at 10 l/min before and after oleic acid injury, the differences in arterial PCO2 between the straight and inverted catheters were 5 +/- and 9 +/- 6 Torr (P < 0.18), respectively. Our data suggest that distal effects of TGI become more pronounced as the catheter tip is positioned closer to the main carina. The distal effects of TGI were not diminished after oleic acid injury when minute ventilation was maintained constant.

Convective and diffusive gas transport in canine intrapulmonary airways

1992 ◽  
Vol 72 (4) ◽  
pp. 1557-1562 ◽  
Author(s):  
H. Schulz ◽  
P. Heilmann ◽  
A. Hillebrecht ◽  
J. Gebhart ◽  
M. Meyer ◽  
...  
Keyword(s):  
Dead Space ◽  
Gas Transport ◽  
Inert Gases ◽  
Differential Analysis ◽  
Mechanically Ventilated ◽  
Convective Mixing ◽  
Conducting Airways ◽  
And Diffusion ◽  
Residual Air ◽  
Space Dispersion

The significance of convective and diffusive gas transport in the respiratory system was assessed from the response of combined inert gas and particle boluses inhaled into the conducting airways. Particles, considered as “nondiffusing gas,” served as tracers for convection and two inert gases with widely different diffusive characteristics (He and SF6) as tracers for convection and diffusion. Six-milliliter boluses labeled with monodisperse di-2-ethylhexyl sebacate droplets of 0.86-microns aerodynamic diameter, 2% He, and 2% SF6 were inspired by three anesthetized mechanically ventilated beagle dogs to volumetric lung depths up to 170 ml. Mixing between inspired and residual air caused dispersion of the inspired bolus, which was quantified in terms of the bolus half-width. Dispersion of particles increased with increasing lung depth to which the boluses were inhaled. The increase followed a power law with exponents less than 0.5 (mean 0.39), indicating that the effect of convective mixing per unit volume was reduced with depth. Within the pulmonary dead space, the behavior of the inert gases He and SF6 was similar to that of the particles, suggesting that gas transport was almost solely due to convection. Beyond the dead space, dispersion of He and SF6 increased more rapidly than dispersion of particles, indicating that diffusion became significant. The gas and particle bolus technique offers a suitable approach to differential analysis of gas transport in intrapulmonary airways of lungs.

scholarly journals Effects of inspiratory pause on CO2 elimination and arterial Pco2 in acute lung injury

2008 ◽  
Vol 105 (6) ◽  
pp. 1944-1949 ◽  
Author(s):  
Jérôme Devaquet ◽  
Björn Jonson ◽  
Lisbet Niklason ◽  
Anne-Gaëlle Si Larbi ◽  
Leif Uttman ◽  
...  
Keyword(s):  
Acute Lung Injury ◽  
Lung Injury ◽  
Dead Space ◽  
Gas Diffusion ◽  
Arterial Pco2 ◽  
Mechanically Ventilated ◽  
Alveolar Plateau ◽  
Single Breath ◽  
Single Breath Test ◽  
Airway Dead Space

A high respiratory rate associated with the use of small tidal volumes, recommended for acute lung injury (ALI), shortens time for gas diffusion in the alveoli. This may decrease CO2 elimination. We hypothesized that a postinspiratory pause could enhance CO2 elimination and reduce PaCO2 by reducing dead space in ALI. In 15 mechanically ventilated patients with ALI and hypercapnia, a 20% postinspiratory pause (Tp20) was applied during a period of 30 min between two ventilation periods without postinspiratory pause (Tp0). Other parameters were kept unchanged. The single breath test for CO2 was recorded every 5 min to measure tidal CO2 elimination (VtCO2), airway dead space (VDaw), and slope of the alveolar plateau. PaO2, PaCO2, and physiological and alveolar dead space (VDphys, VDalv) were determined at the end of each 30-min period. The postinspiratory pause, 0.7 ± 0.2 s, induced on average <0.5 cmH2O of intrinsic positive end-expiratory pressure (PEEP). During Tp20, VtCO2 increased immediately by 28 ± 10% (14 ± 5 ml per breath compared with 11 ± 4 for Tp0) and then decreased without reaching the initial value within 30 min. The addition of a postinspiratory pause significantly decreased VDaw by 14% and VDphys by 11% with no change in VDalv. During Tp20, the slope of the alveolar plateau initially fell to 65 ± 10% of baseline value and continued to decrease. Tp20 induced a 10 ± 3% decrease in PaCO2 at 30 min (from 55 ± 10 to 49 ± 9 mmHg, P < 0.001) with no significant variation in PaO2. Postinspiratory pause has a significant influence on CO2 elimination when small tidal volumes are used during mechanical ventilation for ALI.

scholarly journals Aspiration of airway dead space (ASPIDS) in mechanically ventilated patients

Critical Care ◽  
10.1186/cc213 ◽  
1998 ◽  
Vol 2 (Suppl 1) ◽  
pp. P083
Author(s):  
E De Robertis ◽  
G Servillo ◽  
F Rossano ◽  
B Jonson ◽  
R Tufano
Keyword(s):  
Dead Space ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Airway Dead Space ◽  
Ventilated Patients

scholarly journals Management of hypercapnia in critically ill mechanically ventilated patients—A narrative review of literature

2020 ◽  
Vol 21 (4) ◽  
pp. 327-333
Author(s):  
Ravindranath Tiruvoipati ◽  
Sachin Gupta ◽  
David Pilcher ◽  
Michael Bailey
Keyword(s):  
Mechanical Ventilation ◽  
Tidal Volume ◽  
Dead Space ◽  
Hypercapnic Acidosis ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Low Tidal Volume ◽  
Volume Ventilation ◽  
Low Volume ◽  
Ventilated Patients

The use of lower tidal volume ventilation was shown to improve survival in mechanically ventilated patients with acute lung injury. In some patients this strategy may cause hypercapnic acidosis. A significant body of recent clinical data suggest that hypercapnic acidosis is associated with adverse clinical outcomes including increased hospital mortality. We aimed to review the available treatment options that may be used to manage acute hypercapnic acidosis that may be seen with low tidal volume ventilation. The databases of MEDLINE and EMBASE were searched. Studies including animals or tissues were excluded. We also searched bibliographic references of relevant studies, irrespective of study design with the intention of finding relevant studies to be included in this review. The possible options to treat hypercapnia included optimising the use of low tidal volume mechanical ventilation to enhance carbon dioxide elimination. These include techniques to reduce dead space ventilation, and physiological dead space, use of buffers, airway pressure release ventilation and prone positon ventilation. In patients where hypercapnic acidosis could not be managed with lung protective mechanical ventilation, extracorporeal techniques may be used. Newer, minimally invasive low volume venovenous extracorporeal devices are currently being investigated for managing hypercapnia associated with low and ultra-low volume mechanical ventilation.

Longitudinal distribution of O3 absorption in the lung: gender differences and intersubject variability

1996 ◽  
Vol 81 (4) ◽  
pp. 1651-1657 ◽  
Author(s):  
Michele L. Bush ◽  
Patrick T. Asplund ◽  
Kristen A. Miles ◽  
Abdellaziz Ben-Jebria ◽  
James S. Ultman
Keyword(s):  
Gender Differences ◽  
Dead Space ◽  
Ambient Air ◽  
Exposure Dose ◽  
Longitudinal Distribution ◽  
Exposure Condition ◽  
Intersubject Variability ◽  
Quiet Breathing ◽  
Mass Transfer Parameter ◽  
Conducting Airways

Bush, Michele L., Patrick T. Asplund, Kristen A. Miles, Abdellaziz Ben-Jebria, and James S. Ultman. Longitudinal distribution of O3 absorption in the lung: gender differences and intersubject variability. J. Appl. Physiol. 81(4): 1651–1657, 1996.—Because the National Ambient Air Quality Standard for ozone (O3) is intended to protect the most sensitive individuals in the general population, it is necessary to identify sources of intersubject variation in the exposure-dose-response cascade. We hypothesize that differences in lung anatomy can modulate exposure-dose relationships between individuals, and this results in differences between their responsiveness to O3 at a fixed exposure condition. During quiet breathing, the conducting airways remove the majority of inhaled O3, so the volume of this region should have an important impact on O3 dose distribution. Employing the bolus inhalation method, we measured the distribution of O3 absorption with respect to penetration volume (VP), and using the Fowler single-breath N2washout method, we determined the dead space volume (Vd) in the lungs of 10 men and 10 women at a fixed respiratory flow of 250 ml/s. On average, the women absorbed O3 at smaller VP than the men, and the women had smaller Vd than the men. When expressed in terms of VP/ Vd, the absorption distribution of the men and women was indistinguishable. Moreover, an interpretation of the O3 distribution in terms of an intrinsic mass transfer parameter ( Ka) indicated that differences between the O3 dosimetry in all subjects, whether men or women, could be explained by a unique correlation with anatomic dead space: Ka (in s−1) = 610 Vd −1.05(in ml). Application of this result to measurements of O3 exposure response indicated that previously reported gender differences may be due to a failure in properly accounting for tissue surface within the conducting airways.

CO2-controlled sampling of alveolar gas in mechanically ventilated patients

2001 ◽  
Vol 90 (2) ◽  
pp. 486-492 ◽  
Author(s):  
Jochen K. Schubert ◽  
Karl-Heinz Spittler ◽  
Guenther Braun ◽  
Klaus Geiger ◽  
Josef Guttmann
Keyword(s):  
Dead Space ◽  
Coefficient Of Variation ◽  
Sampling Technique ◽  
Sampling Device ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Selective Enrichment ◽  
Gas Sampling ◽  
End Tidal ◽  
Ventilated Patients

A newly designed gas-sampling device using end-tidal CO2to separate dead space gas from alveolar gas was evaluated in 12 mechanically ventilated patients. For that purpose, CO2-controlled sampling was compared with mixed expiratory sampling. Alveolar sampling valves were easily controlled via CO2concentration. Concentrations of four volatile substances were determined in the expired and inspired gas. Isoflurane and isoprene, which did not occur in the inspired air, had ratios of end-tidal to mixed expired concentrations of 1.75 and 1.81, respectively. Acetone and pentane, found in both the inspired and expired air, showed ratios of 0.96 and 1.0, respectively. Precision of concentration measurements was between 2.4% (isoprene) and 11.2% (isoflurane); reproducibility (as coefficient of variation) was 5%. Because the only possible source of isoflurane and isoprene in this setting was patients' blood, selective enrichment of alveolar gas was demonstrated. By using the new sampling technique, sensitivity of breath analysis was nearly doubled.

scholarly journals In vitro experiments of cerebral blood flow during aspiration thrombectomy: potential effects on cerebral perfusion pressure and collateral flow

2015 ◽  
Vol 8 (9) ◽  
pp. 969-972 ◽  
Author(s):  
Frank Lally ◽  
Mitra Soorani ◽  
Timothy Woo ◽  
Sanjeev Nayak ◽  
Changez Jadun ◽  
...  
Keyword(s):  
Direct Contact ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Collateral Flow ◽  
In Vitro Experiments ◽  
Aspiration Thrombectomy ◽  
Flow Solver ◽  
Catheter Tip

BackgroundMechanical thrombectomy with stent retriever devices is associated with significantly better outcomes than thrombolysis alone in the treatment of acute ischemic stroke. Thrombus aspiration achieves high patency rates, but clinical outcomes are variable. The aim of this study was to examine the effect of different suction conditions on perfusate flow during aspiration thrombectomy.MethodsA computational fluid dynamics model of an aspiration device within a patent and occluded blood vessel was used to simulate flow characteristics using fluid flow solver software. A physical particulate flow model of a patent vessel and a vessel occluded by thrombus was then used to visualize flow direction and measure flow rates with the aspiration catheter placed 1–10 mm proximal of the thrombus, and recorded on video.ResultsThe mathematical model predicted that, in a patent vessel, perfusate is drawn from upstream of the catheter tip while, in an occluded system, perfusate is drawn from the vessel proximal to the device tip with no traction on the occlusion distal of the tip. The in vitro experiments confirmed the predictions of this model. In the occluded vessel aspiration had no effect on the thrombus unless the tip of the catheter was in direct contact with the thrombus.ConclusionsThese experiments suggest that aspiration is only effective if the catheter tip is in direct contact with the thrombus. If the catheter tip is not in contact with the thrombus, aspirate is drawn from the vessels proximal of the occlusion. This could affect collateral flow in vivo.

Sign in / Sign up

Export Citation Format

Share Document