scholarly journals Volumetric Сapnography As a Tool for Evaluation of Alveolar Ventilation Effectiveness in Clinical Practice

2018 ◽  
Vol 14 (5) ◽  
pp. 16-24 ◽  
Author(s):  
P. Török ◽  
F. Depta ◽  
V. Donic ◽  
M. Nosál’ ◽  
S. Imrecze ◽  
...  
Keyword(s):  
Minute Ventilation ◽  
Artery Bypass ◽  
Lung Ventilation ◽  
Co2 Exchange ◽  
Alveolar Ventilation ◽  
Co2 Production ◽  
Dead Space Volume ◽  
The Relationship ◽  
Pressure Controlled ◽  
Space Volume

The purpose of the study was to compare the relationship between the dead space volume and tidal volume (VD/VT) using volumetric capnography (VCap) during pressure controlled (PCV) and pressure supported (PSV) ventilation mode in the postoperative period.Materials and methods. 30 randomly assigned cardiac surgical patients undergoing CABG (coronary artery bypass grafting) using ECC (extracorporeal circuit) were included in an observational, prospective study. Patients were connected to the ventilator immediately after ICU admission. After that, monitoring VD/VT, CO2 production (VECO2) as well as ventilation parameters was carried out. The parameters during PCV and PSV mode were statistically evaluated using t-test.Results. Expiratory CO2 (ETCO2) concentration were not significantly different in both PCV or PSV (p=NS), although both VECO2 and minute ventilation (MV) increased during PSV mode (p<0.01). VD/VT in PSV mode was lower than in PCV. Gas exchange represented by alveolar ventilation (VA) was better during PSV (p<0.01). VA was also higher during PSV (p<0.05). The calculated VD/VT ratio differed between PCV and PSV mode (p<0.01).Conclusion. VCap represents a tool for monitoring of CO2 exchange effectivness. We registered a decrease in VD/VT with improved alveolar ventilation (VA) in PSV mode. VCap seems to be a suitable instrument for adjustment of protective lung ventilation.

scholarly journals Computations of State Ventilation and Respiratory Parameters

2021 ◽  
Author(s):  
Quangang Yang
Keyword(s):  
Dead Space ◽  
Minute Ventilation ◽  
Alveolar Ventilation ◽  
Co2 Production ◽  
Target Variable ◽  
Respiratory Parameters ◽  
Ventilation Support ◽  
Dead Space Volume ◽  
The Impact ◽  
Space Volume

Background: In mechanical ventilation, there are still some challenges to turn a modern ventilator into a fully reactive device, such as lack of a comprehensive target variable and the unbridged gap between input parameters and output results. This paper aims to present a state ventilation which can provide a measure of two primary, but heterogenous, ventilation support goals. The paper also tries to develop a method to compute, rather than estimate, respiratory parameters to obtain the underlying causal information. Methods: This paper presents a state ventilation, which is calculated based on minute ventilation and blood gas partial pressures, to evaluate the efficacy of ventilation support and indicate disease progression. Through mathematical analysis, formulae are derived to compute dead space volume/ventilation, alveolar ventilation, and CO2 production. Results: Measurements from a reported clinical study are used to verify the analysis and demonstrate the application of derived formulae. The state ventilation gives the expected trend to show patient status, and the calculated mean values of dead space volume, alveolar ventilation, and CO2 production are 158mL, 8.8L/m, and 0.45L/m respectively for a group of patients. Discussions and Conclusions: State ventilation can be used as a target variable since it reflects patient respiratory effort and gas exchange. The derived formulas provide a means to accurately and continuously compute respiratory parameters using routinely available measurements to characterize the impact of different contributing factors.

Effect of centrally administered gamma-aminobutyric acid on metabolic function

1986 ◽  
Vol 61 (2) ◽  
pp. 472-476 ◽  
Author(s):  
M. P. Kneussl ◽  
P. Pappagianopoulos ◽  
B. Hoop ◽  
H. Kazemi
Keyword(s):  
Minute Ventilation ◽  
Aminobutyric Acid ◽  
Co2 Production ◽  
Metabolic Function ◽  
Gamma Aminobutyric Acid ◽  
Dead Space Volume ◽  
Anesthetized Dogs ◽  
Gaba Content ◽  
The Brain ◽  
Space Volume

gamma-Aminobutyric acid (GABA) content of the brain increases during hypoxia and hypercapnia and GABA by itself is a central ventilatory depressant and may depress metabolism as well. Therefore the effect of centrally administered GABA by ventriculocisternal perfusion on O2 consumption (VO2) and CO2 production (VCO2) was studied in pentobarbital-anesthetized dogs. GABA (30 mM) in mock cerebrospinal fluid (CSF) was perfused for 15 min at the rate of 1.0 ml/min followed by perfusion with mock CSF alone. Body temperature, perfusion pressure, and CSF pH were kept constant. Minute ventilation (VE) was kept constant mechanically. Under these conditions, VO2, VCO2, alveolar ventilation (VA), and relative pulmonary dead space volume (VD/VT) were measured. During perfusion with 30 mM GABA, mean VO2 (+/- SE) decreased from 96.5 +/- 3.3 to 81.9 +/- 5.1 ml/min, VCO2 from 72.1 +/- 3.8 to 60.7 +/- 3.0 ml/min, and VA from 1.7 +/- 0.1 to 1.3 +/- 0.1 l/min. VD/VT increased from 0.55 +/- 0.02 to 0.65 +/- 0.01. Perfusion with mock CSF alone restored these parameters to initial levels within 15 min. We conclude that centrally administered GABA depresses VO2 and VCO2. This reduction in metabolic function is independent of the central modulatory effects of GABA on respiration.

scholarly journals Reductions in dead space ventilation with nasal high flow depend on physiological dead space volume: metabolic hood measurements during sleep in patients with COPD and controls

2018 ◽  
Vol 51 (5) ◽  
pp. 1702251 ◽  
Author(s):  
Paolo Biselli ◽  
Kathrin Fricke ◽  
Ludger Grote ◽  
Andrew T. Braun ◽  
Jason Kirkness ◽  
...  
Keyword(s):  
Respiratory Rate ◽  
Dead Space ◽  
Minute Ventilation ◽  
High Flow ◽  
Physiological Dead Space ◽  
Copd Patients ◽  
Dead Space Volume ◽  
Anatomical Dead Space ◽  
Dead Space Ventilation ◽  
Space Volume

Nasal high flow (NHF) reduces minute ventilation and ventilatory loads during sleep but the mechanisms are not clear. We hypothesised NHF reduces ventilation in proportion to physiological but not anatomical dead space.11 subjects (five controls and six chronic obstructive pulmonary disease (COPD) patients) underwent polysomnography with transcutaneous carbon dioxide (CO2) monitoring under a metabolic hood. During stable non-rapid eye movement stage 2 sleep, subjects received NHF (20 L·min−1) intermittently for periods of 5–10 min. We measured CO2 production and calculated dead space ventilation.Controls and COPD patients responded similarly to NHF. NHF reduced minute ventilation (from 5.6±0.4 to 4.8±0.4 L·min−1; p<0.05) and tidal volume (from 0.34±0.03 to 0.3±0.03 L; p<0.05) without a change in energy expenditure, transcutaneous CO2 or alveolar ventilation. There was a significant decrease in dead space ventilation (from 2.5±0.4 to 1.6±0.4 L·min−1; p<0.05), but not in respiratory rate. The reduction in dead space ventilation correlated with baseline physiological dead space fraction (r2=0.36; p<0.05), but not with respiratory rate or anatomical dead space volume.During sleep, NHF decreases minute ventilation due to an overall reduction in dead space ventilation in proportion to the extent of baseline physiological dead space fraction.

Voluntary changes in breathing pattern and N2 clearance from lungs

1961 ◽  
Vol 16 (6) ◽  
pp. 1039-1042 ◽  
Author(s):  
Arend Bouhuys ◽  
Stefan Lichtneckert ◽  
Claes Lundgren ◽  
Gunnar Lundin
Keyword(s):  
Breathing Pattern ◽  
Practical Importance ◽  
Lung Ventilation ◽  
Breathing Rate ◽  
Gas Distribution ◽  
Lung Clearance ◽  
Lung Clearance Index ◽  
Dead Space Volume ◽  
Active Substances ◽  
Space Volume

Lung N2 clearance curves were recorded in three normal and two symptom-free asthmatic subjects at breathing rates of 10—60/min and tidal volumes of 350—1,950 ml. A change toward more uniform gas distribution at larger tidal volumes was found in one subject. Changes in breathing rate did not affect gas distribution demonstrably. The washout ventilation per liter lung volume (lung clearance index) did not show significant changes with either breathing rate or tidal volume except for an increase at tidal volumes of less than 450 ml. These findings agree with the assumption of a constant dead space volume at tidal volumes within the range studied. The results are of practical importance for the use of the lung clearance index as a measure of the effect of broncho-active substances on the lung ventilation in man. Submitted on April 28, 1961

Effect of aging on ventilatory response to exercise and CO2

1984 ◽  
Vol 56 (5) ◽  
pp. 1143-1150 ◽  
Author(s):  
M. J. Brischetto ◽  
R. P. Millman ◽  
D. D. Peterson ◽  
D. A. Silage ◽  
A. I. Pack
Keyword(s):  
Ventilatory Response ◽  
Minute Ventilation ◽  
Work Load ◽  
The Elderly ◽  
Co2 Production ◽  
Elderly Subjects ◽  
Control Group ◽  
Effects Of Aging ◽  
Response To Exercise ◽  
The Relationship

Studies were performed to determine the effects of aging on the ventilatory responsiveness to two known respiratory stimulants, inhaled CO2 and exercise. Although explanation of the physiological mechanisms underlying development of exercise hyperpnea remains elusive, there is much circumstantial evidence that during exercise, however mediated, ventilation is coupled to CO2 production. Thus matched groups of young and elderly subjects were studied to determine the relationship between increasing ventilation and increasing CO2 production (VCO2) during steady-state exercise and the change in their minute ventilation in response to progressive hypercapnia during CO2 rebreathing. We found that the slope of the ventilatory response to hypercapnia was depressed in elderly subjects when compared with the younger control group (delta VE/delta PCO2 = 1.64 +/- 0.21 vs. 2.44 +/- 0.40 l X min-1 X mmHg-1, means +/- SE, respectively). In contrast, the slope of the relationship between ventilation and CO2 production during exercise in the elderly was greater than that of younger subjects (delta VE/delta VCO2 = 29.7 +/- 1.19 vs. 25.3 +/- 1.54, means +/- SE, respectively), as was minute ventilation at a single work load (50 W) (32.4 +/- 2.3 vs. 25.7 +/- 1.54 l/min, means +/- SE, respectively). This increased ventilation during exercise in the elderly was not produced by arterial O2 desaturation, and increased anaerobiasis did not play a role. Instead, the increased ventilation during exercise seems to compensate for increased inefficiency of gas exchange such that exercise remains essentially isocapnic. In conclusion, in the elderly the ventilatory response to hypercapnia is less than in young subjects, whereas the ventilatory response to exercise is greater.

Metabolic and respiratory effects of infused sodium acetate in healthy human subjects

1992 ◽  
Vol 263 (6) ◽  
pp. R1271-R1276 ◽  
Author(s):  
P. Burnier ◽  
L. Tappy ◽  
E. Jequier ◽  
D. Schneeberger ◽  
R. Chiolero
Keyword(s):  
Sodium Acetate ◽  
Human Subjects ◽  
Minute Ventilation ◽  
Open Circuit ◽  
Alveolar Ventilation ◽  
Co2 Production ◽  
Healthy Human ◽  
Respiratory Effects ◽  
Normal Human ◽  
Arterial Po2

The metabolic and respiratory effects of intravenous 0.5 M sodium acetate (at a rate of 2.5 mmol/min during 120 min) were studied in nine normal human subjects. O2 consumption (VO2) and CO2 production (VCO2) were measured continuously by open-circuit indirect calorimetry. VO2 increased from 251 +/- 9 to 281 +/- 9 ml/min (P < 0.001), energy expenditure increased from 4.95 +/- 0.17 kJ/min baseline to 5.58 +/- 0.16 kJ/min (P < 0.001), and VCO2 decreased nonsignificantly (211 +/- 7 ml/min vs. 202 +/- 7 ml/min, NS). The extrapulmonary CO2 loss (i.e., bicarbonate generation and excretion) was estimated at 48 +/- 5 ml/min. This observation is consistent with 1 mol of bicarbonate generated from 1 mol of acetate metabolized. Alveolar ventilation decreased from 3.5 +/- 0.2 l/min basal to 3.1 +/- 0.2 l/min (P < 0.001). The minute ventilation (VE) to VO2 ratio decreased from 22.9 +/- 1.3 to 17.6 +/- 0.9 l/l (P < 0.005), arterial PO2 decreased from 93.2 +/- 1.9 to 78.7 +/- 1.6 mmHg (P < 0.0001), arterial PCO2 increased from 39.2 +/- 0.7 to 42.1 +/- 1.1 mmHg (P < 0.0001), pH from 7.40 +/- 0.005 to 7.50 +/- 0.007 (P < 0.005), and arterial bicarbonate concentration from 24.2 +/- 0.7 to 32.9 +/- 1.1 (P < 0.0001). These observations indicate that sodium acetate infusion results in substantial extrapulmonary CO2 loss, which leads to a relative decrease of total and alveolar ventilation.

Respiration

2021 ◽  
pp. 261-291
Author(s):  
Graham Mitchell
Keyword(s):  
Carbon Dioxide ◽  
Gas Exchange ◽  
Respiratory System ◽  
Dead Space ◽  
Ventilation Rate ◽  
Alveolar Ventilation ◽  
Laryngeal Muscles ◽  
Dead Space Volume ◽  
Recurrent Laryngeal Nerves ◽  
Space Volume

This chapter discusses the respiratory system of giraffes. The respiratory system supplies oxygen, removes of carbon dioxide and produces the airflow needed to make sounds. Giraffes do not have the velocity of airflow through the airways to vibrate vocal cords sufficiently to generate sounds able to be heard by humans but can produce sounds able to be heard by giraffes. Air reaches alveoli for gas exchange through a long trachea, which is relatively narrow (~4 cm in diameter). Dead space volume is large. A short trunk and rigid chest wall reduce the capacity of the thorax and consequently lung volume is small. Respiratory rate is low (~10 min-1), but tidal volume is relatively big, and alveolar ventilation rate (VA; ~60 L min-1) delivers sufficient air despite the large dead space volume. Laryngeal muscles act to prevent food from entering the trachea a process controlled by the (short) superior and (long) inferior (recurrent) laryngeal nerves. Air that has been delivered to alveoli comes into contact with pulmonary artery blood (=cardiac output, Q; ~40 L min-1). The VA: Q ratio is ~1.5 (cf 0.8 in humans). Gas exchange occurs by diffusion. The surface area for diffusion is related to the number of alveoli which increase in number during growth from ~1 billion in a newborn giraffe to 11 billion in an adult. Gas carriage of oxygen and carbon dioxide is a function of erythrocytes which are small (MCV = 12 fL) but numerous (12 × 1012 L-1) and each liter of blood contains ~150 g of hemoglobin.

scholarly journals Comparison of Volume-Guaranteed or -Targeted, Pressure-Controlled Ventilation with Volume-Controlled Ventilation during Elective Surgery: A Systematic Review and Meta-Analysis

2021 ◽  
Vol 10 (6) ◽  
pp. 1276
Author(s):  
Volker Schick ◽  
Fabian Dusse ◽  
Ronny Eckardt ◽  
Steffen Kerkhoff ◽  
Simone Commotio ◽  
...  
Keyword(s):  
Systematic Review ◽  
Elective Surgery ◽  
Meta Analysis ◽  
Lung Ventilation ◽  
One Lung Ventilation ◽  
Controlled Ventilation ◽  
Pressure Controlled Ventilation ◽  
Volume Controlled Ventilation ◽  
Volume Controlled ◽  
Pressure Controlled

For perioperative mechanical ventilation under general anesthesia, modern respirators aim at combining the benefits of pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV) in modes typically named “volume-guaranteed” or “volume-targeted” pressure-controlled ventilation (PCV-VG). This systematic review and meta-analysis tested the hypothesis that PCV-VG modes of ventilation could be beneficial in terms of improved airway pressures (Ppeak, Pplateau, Pmean), dynamic compliance (Cdyn), or arterial blood gases (PaO2, PaCO2) in adults undergoing elective surgery under general anesthesia. Three major medical electronic databases were searched with predefined search strategies and publications were systematically evaluated according to the Cochrane Review Methods. Continuous variables were tested for mean differences using the inverse variance method and 95% confidence intervals (CI) were calculated. Based on the assumption that intervention effects across studies were not identical, a random effects model was chosen. Assessment for heterogeneity was performed with the χ2 test and the I2 statistic. As primary endpoints, Ppeak, Pplateau, Pmean, Cdyn, PaO2, and PaCO2 were evaluated. Of the 725 publications identified, 17 finally met eligibility criteria, with a total of 929 patients recruited. Under supine two-lung ventilation, PCV-VG resulted in significantly reduced Ppeak (15 studies) and Pplateau (9 studies) as well as higher Cdyn (9 studies), compared with VCV [random effects models; Ppeak: CI −3.26 to −1.47; p < 0.001; I2 = 82%; Pplateau: −3.12 to −0.12; p = 0.03; I2 = 90%; Cdyn: CI 3.42 to 8.65; p < 0.001; I2 = 90%]. For one-lung ventilation (8 studies), PCV-VG allowed for significantly lower Ppeak and higher PaO2 compared with VCV. In Trendelenburg position (5 studies), this effect was significant for Ppeak only. This systematic review and meta-analysis demonstrates that volume-targeting, pressure-controlled ventilation modes may provide benefits with respect to the improved airway dynamics in two- and one-lung ventilation, and improved oxygenation in one-lung ventilation in adults undergoing elective surgery.

Ventilatory and hyperkalemic responses to incremental exercise after propranolol treatment

1994 ◽  
Vol 77 (4) ◽  
pp. 1907-1912 ◽  
Author(s):  
D. A. Schneider ◽  
M. T. McEniery ◽  
C. Solomon ◽  
J. Jurimae ◽  
M. S. Wehr
Keyword(s):  
Minute Ventilation ◽  
Plasma Potassium ◽  
Muscle Afferents ◽  
Incremental Exercise ◽  
Co2 Production ◽  
Beta Blockade ◽  
Adrenergic Blockade ◽  
Propranolol Treatment ◽  
Positive Correlations ◽  
And Control

The purpose of the present study was to examine the relationship of plasma potassium (K+) and minute ventilation (VE) during incremental cycling (20 W/2 min) under conditions of beta-adrenergic blockade (80 mg of propranolol) and placebo in six untrained male subjects. No significant differences existed between treatments in O2 uptake, CO2 production, blood lactate, pH, or VE during the submaximal work stages of incremental exercise common to both treatments (20–220 W). During exercise with beta-blockade, plasma K+ concentrations were found to be significantly elevated compared with control levels at every work stage except 20 W. Significant positive correlations between VE and plasma K+ were found during both beta-blockade (r = 0.99) and control conditions (r = 1.00). Although the high correlation between VE and K+ was not altered with beta-blockade, propranolol treatment resulted in a significant reduction in the slope of this relationship during incremental exercise (P < 0.01). These findings suggest that 1) beta-blockade decreases the VE-K+ relationship observed during exercise and 2) K+ stimulation of muscle afferents is not an important signal in the control of exercise ventilation.

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