Effect of desflurane-gas mixtures density on airway resistance in a laboratory lung model

2004 ◽  
Vol 21 (Supplement 32) ◽  
pp. 74
Author(s):  
V. Nyktari ◽  
A. Papaioannou ◽  
G. Prinianakis ◽  
E. Mamidakis ◽  
D. Georgopoulos ◽  
...  
Keyword(s):  
Airway Resistance ◽  
Gas Mixtures ◽  
Lung Model

Deposition of aerosol particles and flow resistance in mathematical and experimental airway models

1983 ◽  
Vol 55 (1) ◽  
pp. 154-163 ◽  
Author(s):  
C. S. Kim ◽  
L. K. Brown ◽  
G. G. Lewars ◽  
M. A. Sackner
Keyword(s):  
Flow Resistance ◽  
Airway Resistance ◽  
Flow Distribution ◽  
Aerosol Deposition ◽  
Lung Model ◽  
Straight Tube ◽  
Small Airways ◽  
Two Phase ◽  
Gas Liquid Flow ◽  
Airway Walls

Aerosol deposition and flow resistance in obstructed airways were determined from five mathematical and experimental airway models. The first three models were theoretical and based upon Weibel's symmetrical lung model with 1) uniform reduction of airway diameter in various groups of airway generations; 2) obstruction of a few major airways such that a severe uneven flow distribution occurs in the lung; 3) focal constriction of selected large airways. In model 3, an empirical formula was utilized to assess deposition and resistance in the constricted airways. The remaining two models were tested experimentally; 4) oscillation of a compliant wall in a straight tube and 5) two-phase gas-liquid flow utilizing human sputum in a rigid branching tube. In models 1, 2, and 3, airway resistance increased to a greater extent than did the increase of aerosol deposition except when small airways were obstructed in model 1. Here, the increase of aerosol deposition was slightly higher than the rise in airway resistance. A sharp increase of aerosol deposition with a minimal increase of flow resistance was demonstrated in models 4 and 5. These data indicate that aerosol deposition may be a more sensitive indicator of airway abnormalities than overall airway resistance in small airways obstruction, during oscillation of large and medium airway walls, and when excessive secretions within the airways move with a wave or slug motion.

Interaction of sulfur dioxide and dry cold air in causing bronchoconstriction in asthmatic subjects

1984 ◽  
Vol 57 (2) ◽  
pp. 419-423 ◽  
Author(s):  
R. A. Bethel ◽  
D. Sheppard ◽  
J. Epstein ◽  
E. Tam ◽  
J. A. Nadel ◽  
...  
Keyword(s):  
Sulfur Dioxide ◽  
Room Temperature ◽  
Airway Resistance ◽  
Random Order ◽  
Gas Mixtures ◽  
Cold Air ◽  
Dry Air ◽  
Specific Airway Resistance ◽  
Blinded Study ◽  
Before And After

To determine whether sulfur dioxide and airway cooling and drying interact in causing bronchoconstriction in persons who have asthma, we measured specific airway resistance in seven asthmatic subjects before and after they performed voluntary eucapnic hyperpnea for 3 min breathing four different gas mixtures. The mixtures, which the subjects breathed through a mouthpiece in random order on 4 different days, were 1) humidified room-temperature air, 2) humidified room-temperature air containing 0.5 ppm SO2, 3) cold dry air, and 4) cold dry air containing 0.5 ppm SO2. Each subject breathed at a rate and depth known from preliminary studies to cause little or no bronchoconstriction when that subject inhaled 0.5 ppm SO2 in humidified room-temperature air or cold dry air. When given independently in the blinded study, 0.5 ppm SO2 or cold dry air again caused insignificant bronchoconstriction, but when given together the two stimuli caused significant bronchoconstriction, as indicated by an increase in specific airway resistance from 6.94 +/- 2.85 to 22.35 +/- 10.28 l X cmH2O X l–1 X s (mean +/- SD) (P less than 0.001). thus airway cooling and/or drying increases the bronchoconstriction induced by inhaled SO2 in persons who have asthma. This increase suggests that persons who have asthma may be more sensitive to the bronchoconstrictor effects of ambient SO2 in cold dry environments than in warm moist environments.

scholarly journals Heat and moisture exchanger used in a cardiothoracic surgery intensive care unit: Airway resistance and changing interval

2020 ◽  
Vol 28 (4) ◽  
pp. 593-600
Author(s):  
Huan Liu
Keyword(s):  
Intensive Care Unit ◽  
Intensive Care ◽  
Airway Resistance ◽  
Cardiothoracic Surgery ◽  
Lung Model ◽  
Heat And Moisture Exchanger ◽  
Moisture Exchanger ◽  
Heat And Moisture Exchangers ◽  
Heat And Moisture

Background: This study aims to investigate the efficacy and safety of heat and moisture exchanger on airway resistance in a cardiothoracic surgery intensive care unit. Methods: A total of 31 patients (18 males, 13 females; mean age 51.5 years; range, 39 to 61 years) who were treated with long-term mechanical ventilation due to low cardiac output syndrome after cardiopulmonary bypass and cardiac surgery were retrospectively analyzed between December 2014 and December 2018. In addition, an in vitro lung model and different doses of hydroxyethyl starch in the heat and moisture exchangers to mimic the airway secretions were used and the proper interval to change heat and moisture exchangers was evaluated. Results: In the in vitro lung model, the mean airway resistance was 19.4±0.2 cmH2O/L/sec in the 5 mL group (p=0.060), 20.3±1.0 cmH2O/L/sec in the 10 mL group (p=0.065), and 30.2±1.7 cmH2O/L/sec in the 15 mL group (p<0.001). The airway resistance of heat and moisture exchangers, and total hospital stay and ventilation duration significantly increased in the seven-day group compared to the one-day and three-day groups. The positive culture of bacteria was also significantly higher in the seven-day group. Conclusion: Our study results suggest that heat and moisture exchangers can be safely used for an efficient and timely removal of airway secretions. Volume of approximately 15 mL of liquid in the airflow can dramatically increase the airway resistance. The three-day interval of changing heat and moisture exchangers is ideal in a cardiothoracic surgery intensive care unit where patients have more airway secretions than patients in the general intensive care unit.

Effect of the Physical Properties of Isoflurane, Sevoflurane, and Desflurane on Pulmonary Resistance in a Laboratory Lung Model

2006 ◽  
Vol 104 (6) ◽  
pp. 1202-1207 ◽  
Author(s):  
Vasilia G. Nyktari ◽  
Alexandra A. Papaioannou ◽  
George Prinianakis ◽  
Eytichis G. Mamidakis ◽  
Dimitris Georgopoulos ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Airway Resistance ◽  
Anesthesia Machine ◽  
Lung Model ◽  
Control Mode ◽  
Volume Control ◽  
Pulmonary Resistance ◽  
Test Lung ◽  
Significant Difference ◽  
Volatile Agents

Background Airway resistance depends not only on an airway's geometry but also on flow rate, and gas density and viscosity. A recent study showed that at clinically relevant concentrations, the mixtures of volatile agents with air and oxygen and oxygen-nitrogen affected the density of the mixture. The goal of the current study was to investigate the effect of different minimum alveolar concentrations (MACs) of three commonly used volatile agents, isoflurane, sevoflurane, and desflurane, on the measurements of airway resistance. Methods A two-chamber fixed-resistance test lung was connected to an anesthesia machine using the volume control mode of ventilation. Pulmonary resistance was calculated at baseline (25% oxygen in air); at 1.0, 1.5, and 2.0 MAC; and also at the same concentrations, 1.2% and 4%, of isoflurane, sevoflurane, and desflurane mixtures with 25% oxygen in air. The analysis of variance test for repeated measures and probabilities for post hoc Tukey and least significant difference tests were used. Results Isoflurane affected pulmonary resistance only at 2 MAC. Sevoflurane caused a significant increase of pulmonary resistance at 1.5 and 2 MAC, whereas desflurane caused the greatest increase in pulmonary resistance at all MAC values used. At 1.2% concentration, no difference from the baseline resistance was observed, whereas at 4%, the three agents produced similar increases of pulmonary resistance. Conclusion High concentrations of volatile agents in 25% oxygen in air increased the density of the gas mixture and the calculated resistance of a test lung model with fixed resistance.

scholarly journals Impact of endotracheal tube biofilm and respiratory secretions on airway resistance and mechanics of breathing in a neonatal lung model

2018 ◽  
Vol 125 (4) ◽  
pp. 1227-1231 ◽  
Author(s):  
Kaitlin M. Kenaley ◽  
Tom Blackson ◽  
Lori Boylan ◽  
Joseph Ciarlo ◽  
Michael Antunes ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Endotracheal Tube ◽  
Flow Rate ◽  
Airway Resistance ◽  
Minute Ventilation ◽  
Clinical Impact ◽  
Lung Model ◽  
Study Group ◽  
Neonatal Lung ◽  
The Impact

Endotracheal tube (ETT) obstruction from biofilm formation is a theoretical risk for intubated preterm neonates. The objective of this study is to determine the impact of ETT biofilm on ETT resistance and minute ventilation in a neonatal respiratory model. Postextubation 2.5- and 3.0-mm ETTs from ventilated preterm infants were matched with unused control ETTs. The pressure gradient across the ETT was measured at set flow rates and converted to airway resistance. Spontaneous breathing tests (SBTs) were performed using a virtual patient model and were considered “passed” if minute ventilation of patient ETTs was greater than 60% of control ETTs. Twenty-four 2.5-mm ETTs and sixteen 3.0-mm ETTs were analyzed. In both patient and control ETTs, as flow rate increases, the pressure gradient across the ETT also increases in a linear fashion. Resistance to flow in patient ETTs was statistically different from matched control ETTs ( P < 0.001), and patient ETTs had 19.9 cmH2O·l−1·sec−1 greater resistance than control ETTs. SBTs were performed in 27 of 40 ETTs. Twenty-six ETTs “passed” an SBT. In one obstructed 3.0-mm ETT, SBT measurements were unobtainable. The clinical impact of ETT biofilm as measured by a SBT appears to be minimal for the majority of patients in our study group. In 1 out of 27 ETTs, the presence of a biofilm significantly altered resistance to airflow and resulted in a failed SBT. Gas flow rate and ETT size had a greater impact on resistance to airflow and minute ventilation than ETT biofilm in this study sample. NEW & NOTEWORTHY This is the first study to our knowledge to characterize the impact of endotracheal tube (ETT) biofilm and respiratory secretions on resistance to airflow in a neonatal ETT using a simulation neonatal lung model. Results show that the clinical impact of ETT biofilm is minimal for the majority of patients in our study group, and ETT obstruction from biofilm is an uncommon cause of respiratory decompensation in a preterm neonate.

scholarly journals Whole-body plethysmography revisited

2021 ◽  
Author(s):  
Swen Hülsmann ◽  
Amara Khan ◽  
Liya Hagos ◽  
Martin Hindermann ◽  
Torsten Nägel ◽  
...  
Keyword(s):  
Airway Resistance ◽  
Pressure Profile ◽  
Lung Model ◽  
Whole Body ◽  
Chamber Pressure ◽  
Body Plethysmography ◽  
Relative Contribution ◽  
Pressure Peak ◽  
Temporal Pressure ◽  
Whole Body Plethysmography

AbstractWhole-body plethysmography (WBP) is an established method to determine physiological parameters and pathophysiological alteration of breathing in animals and animal models of a variety of diseases, reaching from pulmonary diseases to complex neurological syndromes. Although frequently used, there is ongoing debate about what exactly is measured by whole-body-plethysmography and how reliable the data derived from this method are? Here, we designed a simple device that can serve as an artificial lung model that enables a thorough evaluation of different predictions about and around whole-body plethysmography. Using our lung model, we confirmed that during WBP two components contribute to the pressure changes detected in the chamber: 1) the increase of the pressure due to heating and moistening of the air, termed as conditioning, during inspiration; 2) changes of chamber pressure that depend on airway resistance. Both components overlap and contribute to the temporal pressure-profile measured in the chamber or across the wall of the chamber. Our data showed that a precise measurement of the breathing volume appears to be hindered by at least two factors: 1) the unknown relative contribution of each of these components; 2) not only the air in the inspired volume is conditioned during inspiration, but also air within the residual volume and death space that is recruited during inspiration. Moreover, our data suggest that the expiratory negative pressure peak that is used to determine the so called “enhanced pause” (Penh) parameter is not a measure for airway resistance as such but rather a consequence of the animal’s response to the airway resistance, using active expiration to overcome the resistance by a higher thoracic pressure.

Effect of hypercapnia on laryngeal airway resistance in normal adult humans

1994 ◽  
Vol 77 (6) ◽  
pp. 2797-2803 ◽  
Author(s):  
S. T. Kuna ◽  
C. R. Vanoye ◽  
J. R. Griffin ◽  
J. D. Updegrove
Keyword(s):  
Airway Resistance ◽  
Face Mask ◽  
Gas Mixtures ◽  
Normal Adult ◽  
Pressure Flow ◽  
Adult Humans ◽  
Series Of Experiments ◽  
End Tidal ◽  
End Tidal Co2 ◽  
Laryngeal Airway

Laryngeal airway resistance (Rlar) was measured in eight normal adult humans during progressive hyperoxic hypercapnia. In most subjects, the translaryngeal pressure-flow relationship appeared linear under normocapnic conditions. During hypercapnia, the pressure-flow relationship on inspiration and expiration was curvilinear with increasing translaryngeal pressure associated with progressively smaller increments in flow. Translaryngeal pressure-flow relationships at different CO2 levels were compared over their common flow ranges by performing a least-squares linear regression on data throughout inspiration and expiration. During normocapnia, the mean slope, i.e., mean Rlar, was 0.50 +/- 0.21 (SD) cmH2O.l-1.s. A moderately significant decrease in Rlar was present at 9% end-tidal CO2 (P = 0.08). In a separate series of experiments, subjects breathed oxygen- and helium-based gas mixtures through a face mask attached to a pneumotachograph. Data analysis over the flow range present during normocapnia revealed no difference in Rlar between nose and mouth breathing and similar decreases in Rlar under hypercapnic conditions with the oxygen- and helium-based gas mixtures. The decrease in Rlar from normocapnic to hypercapnic conditions found over common, but relatively low, ranges of flow predicts that even greater increases in Rlar would occur at high flow rates in the absence of increasing glottic aperture.

Response of Nasal Airway Resistance to Hypercapnia and Hypoxia in Man

1979 ◽  
Vol 88 (2) ◽  
pp. 247-252 ◽  
Author(s):  
Thomas V. McCaffrey ◽  
Eugene B. Kern
Keyword(s):  
Carbon Dioxide ◽  
Airway Resistance ◽  
Gas Mixtures ◽  
Rank Test ◽  
Nasal Airway ◽  
Respiratory Response ◽  
Nasal Airway Resistance ◽  
Signed Rank ◽  
Wilcoxon Signed Rank Test ◽  
Signed Rank Test

The response of nasal airway resistance (Rn) to various degrees of hypoxia and hypercapnia was measured in six subjects using active posterior mask rhinomanometry. All resistances were computed during expiration at the flow rate of 0.5 liter/sec. Hypercapnia, induced by breathing gas mixtures of various contents of carbon dioxide, significantly decreased Rn ( P < 0.05, Wilcoxon signed rank test). The reduction in Rn was proportional to the inspired partial pressure of carbon dioxide over a range of 0 to 50 torr. Breathing gas mixtures of high and low contents of oxygen produced no significant change in Rn ( P > 0.05, Wilcoxon signed rank test). These results indicate that the nasal airway is actively involved in the respiratory response to hypercapnia but not to moderate hypoxia.

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