Linear programming analysis of VA/Q distributions: limits on central moments

1986 ◽  
Vol 60 (5) ◽  
pp. 1772-1781 ◽  
Author(s):  
K. S. Kapitan ◽  
P. D. Wagner
Keyword(s):  
Linear Programming ◽  
Confidence Intervals ◽  
Infinite Family ◽  
Blood Gases ◽  
Basic Structure ◽  
Inert Gas ◽  
Retention Data ◽  
Arterial Blood Gases ◽  
Central Moments ◽  
Arterial Blood

Linear programming examines the boundaries of infinite sets. We used this method with the multiple-inert gas-elimination technique to examine the central moments and arterial blood gases of the infinite family of ventilation perfusion (VA/Q) distributions that are compatible with a measured inert gas-retention set. A linear program was applied with Monte-Carlo error simulation to theoretical retention data, and 95% confidence intervals were constructed for the first three moments (mean, dispersion, and skew) and the arterial PO2 and PCO2 of all compatible blood flow distributions. Six typical cases were studied. Results demonstrate narrow confidence intervals for both the lower moments and predicted arterial blood gases of all test cases, which widen as moment number or error increase. We conclude that the blood gas composition and basic structure of all compatible VA/Q distributions are tightly constrained and that even subtle changes in this structure, as may occur experimentally, can be identified.

Validation of measurements of ventilation-to-perfusion ratio inequality in the lung from expired gas

2003 ◽  
Vol 94 (3) ◽  
pp. 1186-1192 ◽  
Author(s):  
G. Kim Prisk ◽  
Harold J. B. Guy ◽  
John B. West ◽  
James W. Reed
Keyword(s):  
Gas Exchange ◽  
Respiratory Exchange Ratio ◽  
Blood Gases ◽  
Inert Gas ◽  
Phase Iii ◽  
Strongly Correlated ◽  
Arterial Blood Gases ◽  
Arterial Blood ◽  
Expired Gas ◽  
The Relationship

The analysis of the gas in a single expirate has long been used to estimate the degree of ventilation-perfusion (V˙a/Q˙) inequality in the lung. To further validate this estimate, we examined three measures ofV˙a/Q˙ inhomogeneity calculated from a single full exhalation in nine anesthetized mongrel dogs under control conditions and after exposure to aerosolized methacholine. These measurements were then compared with arterial blood gases and with measurements of V˙a/Q˙ inhomogeneity obtained using the multiple inert gas elimination technique. The slope of the instantaneous respiratory exchange ratio (R slope) vs. expired volume was poorly correlated with independent measures, probably because of the curvilinear nature of the relationship due to continuing gas exchange. When R was converted to the intrabreathV˙a/Q˙ (iV˙/Q˙), the best index was the slope of iV˙/Q˙ vs. volume over phase III (iV˙/Q˙slope). This was strongly correlated with independent measures, especially those relating to inhomogeneity of perfusion. The correlations for iV˙/Q˙ slope and R slope considerably improved when only the first half of phase III was considered. We conclude that a useful noninvasive measurement ofV˙a/Q˙ inhomogeneity can be derived from the intrabreath respiratory exchange ratio.

Arterial blood gases in man during inert gas narcosis.

1974 ◽  
Vol 36 (1) ◽  
pp. 45-48 ◽  
Author(s):  
P B Bennett ◽  
G D Blenkarn
Keyword(s):  
Blood Gases ◽  
Inert Gas ◽  
Arterial Blood Gases ◽  
Arterial Blood

scholarly journals Pathophysiology and clinical consequences of arterial blood gases and pH after cardiac arrest

2020 ◽  
Vol 8 (S1) ◽  
Author(s):  
Chiara Robba ◽  
Dorota Siwicka-Gieroba ◽  
Andras Sikter ◽  
Denise Battaglini ◽  
Wojciech Dąbrowski ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Mechanical Ventilation ◽  
Cardiac Arrest ◽  
Oxygen Demand ◽  
Blood Gases ◽  
Metabolic Energy ◽  
High Morbidity ◽  
Arterial Blood Gases ◽  
Arterial Blood ◽  
Clinical Consequences

AbstractPost cardiac arrest syndrome is associated with high morbidity and mortality, which is related not only to a poor neurological outcome but also to respiratory and cardiovascular dysfunctions. The control of gas exchange, and in particular oxygenation and carbon dioxide levels, is fundamental in mechanically ventilated patients after resuscitation, as arterial blood gases derangement might have important effects on the cerebral blood flow and systemic physiology.In particular, the pathophysiological role of carbon dioxide (CO2) levels is strongly underestimated, as its alterations quickly affect also the changes of intracellular pH, and consequently influence metabolic energy and oxygen demand. Hypo/hypercapnia, as well as mechanical ventilation during and after resuscitation, can affect CO2 levels and trigger a dangerous pathophysiological vicious circle related to the relationship between pH, cellular demand, and catecholamine levels. The developing hypocapnia can nullify the beneficial effects of the hypothermia. The aim of this review was to describe the pathophysiology and clinical consequences of arterial blood gases and pH after cardiac arrest.According to our findings, the optimal ventilator strategies in post cardiac arrest patients are not fully understood, and oxygen and carbon dioxide targets should take in consideration a complex pattern of pathophysiological factors. Further studies are warranted to define the optimal settings of mechanical ventilation in patients after cardiac arrest.

Arterial Blood Gases in Pranayama Practice

1978 ◽  
Vol 46 (1) ◽  
pp. 171-174 ◽  
Author(s):  
V. Pratap ◽  
W. H. Berrettini ◽  
C. Smith
Keyword(s):  
Blood Gases ◽  
Neural Mechanism ◽  
Arterial Blood Gases ◽  
Arterial Blood ◽  
Yogic Breathing ◽  
The Mind ◽  
Calming Effect

Pranayama is a Yogic breathing practice which is known experientially to produce a profound calming effect on the mind. In an experiment designed to determine whether the mental effects of this practice were accompanied by changes in the arterial blood gases, arterial blood was drawn from 10 trained individuals prior to and immediately after Pranayama practice. No significant changes in arterial blood gases were noted after Pranayama. A neural mechanism for the mental effects of this practice is proposed.

Respiratory syncytial virus infection in anesthetized weanling rather than adult rats prolongs the apneic responses to right atrial injection of capsaicin

2007 ◽  
Vol 102 (6) ◽  
pp. 2201-2206 ◽  
Author(s):  
Wenhong Peng ◽  
Jianguo Zhuang ◽  
Kevin S. Harrod ◽  
Fadi Xu
Keyword(s):  
Respiratory Syncytial Virus ◽  
Blood Gases ◽  
Respiratory Frequency ◽  
Right Atrial ◽  
Arterial Blood Gases ◽  
Adult Rats ◽  
Intranasal Inoculation ◽  
Arterial Blood ◽  
Rsv Infection ◽  
Syncytial Virus

Apnea is a common complication in infants infected by respiratory syncytial virus (RSV). A recent study has shown that intranasal inoculation of RSV in conscious weanling rats strengthens the apneic responses to right atrial injection of capsaicin (CAP), leading to 66% mortality. The objectives of the present study were to determine 1) whether RSV infection changes baseline minute ventilation (V̇e) and arterial blood gases in anesthetized rats; 2) what the effects of RSV infection are on the respiratory responses to CAP; and 3) whether the RSV-strengthened apneic responses are age dependent. Our experiments were conducted in anesthetized and spontaneously breathing rats divided into four groups of weanling and adult rats that received either intranasal inoculation of RSV or virus-free medium. Two days after RSV infection (0.7 ml/kg), animal blood gases, baseline V̇e, and V̇e responses to right atrial injection of three doses of CAP (4, 16, and 64 μg/kg) were measured and compared among the four groups. Our results showed that RSV infection increased respiratory frequency (∼25%, P < 0.05) in weanling but not adult rats, with little effect on arterial blood gases. RSV infection amplified the apneic responses to CAP in weanling but not adult rats, characterized by increases in the initial (40%) and the longest apneic duration (650%), the number of apneic episodes (139%), and the total duration of apneas (60%). These amplifications led to 50% mortality ( P < 0.05). We conclude that RSV infection increases respiratory frequency and strengthens the apneic responses to CAP only in anesthetized weanling but not adult rats.

Fetal cardiac bypass alters regional blood flows, arterial blood gases, and hemodynamics in sheep

1992 ◽  
Vol 263 (3) ◽  
pp. H919-H928 ◽  
Author(s):  
S. M. Bradley ◽  
F. L. Hanley ◽  
B. W. Duncan ◽  
R. W. Jennings ◽  
J. A. Jester ◽  
...  
Keyword(s):  
Blood Flow ◽  
Blood Gases ◽  
Arterial Blood Gases ◽  
Blood Flows ◽  
Arterial Blood ◽  
Cardiac Bypass ◽  
Regional Blood Flows ◽  
Placental Blood ◽  
Fetal Organs ◽  
Placental Blood Flow

Successful fetal cardiac bypass might allow prenatal correction of some congenital heart defects. However, previous studies have shown that fetal cardiac bypass may result in impaired fetal gas exchange after bypass. To investigate the etiology of this impairment, we determined whether fetal cardiac bypass causes a redistribution of fetal regional blood flows and, if so, whether a vasodilator (sodium nitroprusside) can prevent this redistribution. We also determined the effects of fetal cardiac bypass with and without nitroprusside on fetal arterial blood gases and hemodynamics. Eighteen fetal sheep were studied in utero under general anesthesia. Seven fetuses underwent bypass without nitroprusside, six underwent bypass with nitroprusside, and five were no-bypass controls. Blood flows were determined using radionuclide-labeled microspheres. After bypass without nitroprusside, placental blood flow decreased by 25–60%, whereas cardiac output increased by 15–25%. Flow to all other fetal organs increased or remained unchanged. Decreased placental blood flow after bypass was accompanied by a fall in PO2 and a rise in PCO2. Nitroprusside improved placental blood flow, cardiac output, and arterial blood gases after bypass. Thus fetal cardiac bypass causes a redistribution of regional blood flow away from the placenta and toward the other fetal organs. Nitroprusside partially prevents this redistribution. Methods of improving placental blood flow in the postbypass period may prove critical to the success of fetal cardiac bypass.

Ventilatory responses of hamsters and rats to hypoxia and hypercapnia

1985 ◽  
Vol 59 (6) ◽  
pp. 1955-1960 ◽  
Author(s):  
B. R. Walker ◽  
E. M. Adams ◽  
N. F. Voelkel
Keyword(s):  
Duty Cycle ◽  
Minute Ventilation ◽  
Natural Habitat ◽  
Blood Gases ◽  
Atmospheric Conditions ◽  
Arterial Blood Gases ◽  
Ventilatory Responses ◽  
Arterial Blood ◽  
Rat Experiments ◽  
Fossorial Species

As a fossorial species the hamster differs in its natural habitat from the rat. Experiments were performed to determine possible differences between the ventilatory responses of awake hamsters and rats to acute exposure to hypoxic and hypercapnic environments. Ventilation was measured with the barometric method while the animals were conscious and unrestrained in a sealed plethysmograph. Tidal volume (VT), respiratory frequency (f), and inspiratory (TI) and expiratory (TE) time measurements were made while the animals breathed normoxic (30% O2), hypercapnic (5% CO2), or hypoxic (10% O2) gases. Arterial blood gases were also measured in both species while exposed to each of these atmospheric conditions. During inhalation of normoxic gas, the VT/100 g was greater and f was lower in the hamster than in the rat. Overall minute ventilation (VE/100 g) in the hamster was less than in the rat, which was reflected in the lower PO2 and higher PCO2 of the hamster arterial blood. When exposed to hypercapnia, the hamster increased VE/100 g solely through VT; however, the VE/100 g increase was significantly less than in the rat. In response to hypoxia, the hamster and rat increased VE/100 g by similar amounts; however, the hamster VE/100 g increase was through f alone, whereas the rat increased both VT/100 g and f. Mean airflow rates (VT/TI) were no different in the hamster or rat in each gas environment; therefore most of the ventilatory responses were the result of changes in TI and TE and respiratory duty cycle (TI/TT).

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