Digital Simulation of the Chemical Control of Ventilation

1973 ◽  
Vol 95 (3) ◽  
pp. 335-339
Author(s):  
H. T. Milhorn ◽  
W. J. Reynolds
Keyword(s):  
Computer Model ◽  
Respiratory System ◽  
Digital Computer ◽  
Chemical Control ◽  
Minute Ventilation ◽  
Digital Simulation ◽  
Transient Responses ◽  
O2 Concentration ◽  
Lower Oxygen ◽  
Series Of Experiments

Experimental human data, obtained for the development and evaluation of a digital computer model of the human respiratory system, are presented. The data are from two series of experiments. In the first series the transient responses of tidal volume, respiratory frequency, minute ventilation, alveolar Pco2 and alveolar Po2 were obtained for several inspired CO2 concentrations (3, 5, 6, and 7 percent). In the second series, transient responses of the same variables were obtained for steps of inspired O2 concentration from room air to several lower oxygen levels (9, 8, and 7 percent). An example of the use of the data for the development and evaluation of a model is indicated.

Diffusion limitation in normal humans during exercise at sea level and simulated altitude

1985 ◽  
Vol 58 (3) ◽  
pp. 989-995 ◽  
Author(s):  
J. R. Torre-Bueno ◽  
P. D. Wagner ◽  
H. A. Saltzman ◽  
G. E. Gale ◽  
R. E. Moon
Keyword(s):  
Sea Level ◽  
Minute Ventilation ◽  
Inert Gas ◽  
Diffusion Resistance ◽  
Diffusion Limitation ◽  
O2 Concentration ◽  
Normal Humans ◽  
Respiratory Gases ◽  
Arterial Po2 ◽  
Alveolar Capillary

The relative roles of ventilation-perfusion (VA/Q) inequality, alveolar-capillary diffusion resistance, postpulmonary shunt, and gas phase diffusion limitation in determining arterial PO2 (PaO2) were assessed in nine normal unacclimatized men at rest and during bicycle exercise at sea level and three simulated altitudes (5,000, 10,000, and 15,000 ft; barometric pressures = 632, 523, and 429 Torr). We measured mixed expired and arterial inert and respiratory gases, minute ventilation, and cardiac output. Using the multiple inert gas elimination technique, PaO2 and the arterial O2 concentration expected from VA/Q inequality alone were compared with actual values, lower measured PaO2 indicating alveolar-capillary diffusion disequilibrium for O2. At sea level, alveolar-arterial PO2 differences were approximately 10 Torr at rest, increasing to approximately 20 Torr at a metabolic consumption of O2 (VO2) of 3 l/min. There was no evidence for diffusion disequilibrium, similar results being obtained at 5,000 ft. At 10 and 15,000 ft, resting alveolar-arterial PO2 difference was less than at sea level with no diffusion disequilibrium. During exercise, alveolar-arterial PO2 difference increased considerably more than expected from VA/Q mismatch alone. For example, at VO2 of 2.5 l/min at 10,000 ft, total alveolar-arterial PO2 difference was 30 Torr and that due to VA/Q mismatch alone was 15 Torr. At 15,000 ft and VO2 of 1.5 l/min, these values were 25 and 10 Torr, respectively. Expected and actual PaO2 agreed during 100% O2 breathing at 15,000 ft, excluding postpulmonary shunt as a cause of the larger alveolar-arterial O2 difference than accountable by inert gas exchange.

Mechanics of the respiratory system in the newborn tammar wallaby

2002 ◽  
Vol 205 (4) ◽  
pp. 533-538 ◽  
Author(s):  
P. M. MacFarlane ◽  
P. B. Frappell ◽  
J. P. Mortola
Keyword(s):  
Respiratory System ◽  
Spontaneous Breathing ◽  
Minute Ventilation ◽  
Pulmonary Ventilation ◽  
Age Groups ◽  
Mechanical Efficiency ◽  
Tammar Wallaby ◽  
Ventilatory Equivalent ◽  
Rate Of Oxygen Consumption ◽  
Respiratory System Resistance

SUMMARY We investigated whether the mechanical properties of the respiratory system represent a major constraint to spontaneous breathing in the newborn tammar wallaby Macropus eugenii, which is born after a very short gestation (approximately 28 days, birth mass approximately 380 mg). The rate of oxygen consumption (V̇O2) through the skin was approximately 33 % of the total V̇O2 at day 1 and approximately 14 % at day 6. The mass-specific resting minute ventilation (V̇e) and the ventilatory equivalent (V̇e/V̇O2) were approximately the same at the two ages, with a breathing pattern significantly deeper and slower at day 1. The mass-specific compliance of the respiratory system (Crs) did not differ significantly between the two age groups and was close to the values predicted from measurements in eutherian newborns. Mass-specific respiratory system resistance (Rrs) at day 1 was higher than at day 6, and also higher than in eutherian newborns. Chest distortion, quantified as the degree of abdominal motion during spontaneous breathing compared with that required to inflate the lungs passively, at day 1 was very large, whereas it was modest at day 6. We conclude that, in the tammar wallaby at birth, the high resistance of the respiratory system and the distortion of the chest wall greatly reduce the mechanical efficiency of breathing. At this age, gas exchange through the skin is therefore an important complement to pulmonary ventilation.

Closure to “Urban Runoff Digital Computer Model”

1978 ◽  
Vol 104 (11) ◽  
pp. 1554-1555
Author(s):  
Sanguan Phamwon ◽  
Yu-Si Fok
Keyword(s):  
Computer Model ◽  
Digital Computer ◽  
Urban Runoff

Ventilatory afterdischarge and central respiratory drive interactions in the awake goat

1994 ◽  
Vol 76 (1) ◽  
pp. 416-423 ◽  
Author(s):  
M. J. Engwall ◽  
C. A. Smith ◽  
J. A. Dempsey ◽  
G. E. Bisgard
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Time Constant ◽  
Minute Ventilation ◽  
Respiratory Drive ◽  
Arterial Pco2 ◽  
Expiratory Muscle ◽  
Series Of Experiments ◽  
Short Time ◽  
Animal Preparation

We have previously established the existence of ventilatory afterdischarge (VAD) in the awake goat by means of an isolated perfused carotid body (CB) technique. In the present series of experiments we used this animal preparation to examine the effects of systemic (central nervous system) hypoxia, mild hypercapnia, and hypocapnia on the manifestation of VAD in ventilatory variables and respiratory muscle electromyogram activity after hypoxic stimulation of the isolated CB. With systemic isocapnic normoxia, inspired minute ventilation remains above control for 30–40 s (time constant = 16.8 s) after termination of CB hypoxia; however, with systemic hypocapnia, VAD is short (time constant = 5.5 s) and hypoventilation is common after removal of CB stimulation. During mild systemic hypercapnia, VAD is prolonged (time constant = 39.9 s). However, systemic (central nervous system) hypoxia did not decrease VAD (time constant = 17.0 s). These results indicate that the manifestation of VAD is more sensitive to the level of arterial PCO2 and central chemoreceptor activity than it is to the state of central oxygenation. Inspiratory and expiratory muscle electromyogram activities qualitatively tracked ventilation during CB stimulation and during the VAD period in all conditions.

Ontogeny of dry gas hyperpnea-induced bronchoconstriction in guinea pigs

1994 ◽  
Vol 76 (3) ◽  
pp. 1150-1155 ◽  
Author(s):  
T. M. Murphy ◽  
D. W. Ray ◽  
L. E. Alger ◽  
I. J. Phillips ◽  
J. C. Roach ◽  
...  
Keyword(s):  
Respiratory System ◽  
Guinea Pigs ◽  
Minute Ventilation ◽  
Similar Degree ◽  
Fractional Increase ◽  
Respiratory System Resistance ◽  
Key Features

Adolescent guinea pigs (AGPs) demonstrate dry gas hyperpnea-induced bronchoconstriction (HIB) that shares key features with HIB in humans with asthma. The airways of immature animals exhibit enhanced reactivity to diverse types of stimulation. We tested whether dry gas HIB is also increased in newborn guinea pigs (NGPs). We quantified HIB as the fractional increase of respiratory system resistance (Rrs) over baseline (BL) in five 4- to 7-day-old NGPs after 10 min of hyperpnea, as well as changes in Rrs elicited by intravenous methacholine or capsaicin, and compared these responses with those of AGPs. During hyperpnea, analogous stimuli were delivered by mechanically imposing hyperpnea at 3.0, 4.5, and 6.0 times quiet eucapnic minute ventilation (VE). In AGPs, hyperpnea caused significant bronchoconstriction that increased with VE; peak fractional increase of Rrs was 7.6 +/- 2.0 times BL. In contrast, hyperpnea caused insignificant bronchoconstriction in NGPs (1.4 +/- 0.2 times BL after the largest VE; P < 0.05 vs. AGP). Responses elicited by methacholine (10(-10)-10(-7) mol/kg) or capsaicin (0.01–10.0 microgram/kg) were similar in NGPs and AGPs. In AGPs, hyperpnea suppressed HIB until posthyperpnea. To determine whether the reduced HIB of NGPs was caused by enhanced suppression, NGPs and AGPs were administered acetylcholine (10(-10)-10(-7) mol/kg i.v.) during BL eucapnic ventilation and during eucapnic hyperpnea with warm humidified gas. Responses to acetylcholine were suppressed in AGPs and NGPs to a similar degree. We conclude that HIB is markedly diminished shortly after birth in guinea pigs and that it increases substantially during maturation.(ABSTRACT TRUNCATED AT 250 WORDS)

Ontogeny of respiratory control and pulmonary mechanics in newborn rabbits

1985 ◽  
Vol 59 (5) ◽  
pp. 1477-1486 ◽  
Author(s):  
M. M. Grunstein ◽  
D. T. Tanaka
Keyword(s):  
Mechanical Properties ◽  
Tidal Volume ◽  
Respiratory System ◽  
Minute Ventilation ◽  
Work Of Breathing ◽  
Relative Volume ◽  
Respiratory Pattern ◽  
Pulmonary Mechanics ◽  
Volume Loss ◽  
Age Related

Maturation of the respiratory pattern and the active and passive mechanical properties of the respiratory system were assessed in 19 tracheotomized rabbits (postnatal age range: 1–26 days) placed in a body plethysmograph. With maturation both minute ventilation and tidal volume significantly increased, whereas respiratory frequency decreased. When normalized for body weight (kg) both the passive (Rrs X kg) and active (R'rs X kg) resistances of the respiratory system significantly increased with age, whereas the corresponding passive (Crs X kg-1) and active (C'rs X kg-1) compliances significantly decreased. At any given age R'rs X kg only slightly exceeded Rrs X kg, whereas C'rs X kg-1 was significantly lower than Crs X kg-1. Moreover, the maturational increases in Rrs X kg and R'rs X kg exceeded the corresponding decreases in Crs X kg-1 and C'rs X kg-1, resulting in significant age-related increases in both the passive (tau rs) and active (tau'rs) time constants of the respiratory system. Due to the age-related increases in tau'rs, producing a delayed volume response to any given inspiratory driving pressure, the relative volume loss obtained at any time during inspiration was greater in the maturing rabbit. On the other hand, because of concomitant compensatory changes in respiratory pattern, evidenced by increases in inspiratory duration with age, the end-inspiratory tidal volume loss in the maturing animal was maintained generally less than 10% at all postnatal ages. Thus maturational changes in respiratory pattern appear coupled to changes in the active mechanical properties of the respiratory system. The latter coupling serves to optimize the transduction of inspiratory pressure into volume change in a manner consistent with establishing the minimum inspiratory work of breathing during postnatal development.

Analysis of perfluorochemical elimination from the respiratory system

1997 ◽  
Vol 83 (3) ◽  
pp. 1033-1033 ◽  
Author(s):  
Thomas H. Shaffer ◽  
Raymond Foust ◽  
Marla R. Wolfson ◽  
Thomas F. Miller
Keyword(s):  
Respiratory System ◽  
Minute Ventilation ◽  
In Vivo Studies ◽  
In Vitro Tests ◽  
Volume Loss ◽  
Concentration Data ◽  
Expired Gas ◽  
Respiratory Gases

Shaffer, Thomas H., Raymond Foust IIII, Marla R. Wolfson, and Thomas F. Miller, Jr. Analysis of perfluorochemical elimination from the respiratory system. J. Appl. Physiol. 83(3): 1033–1040, 1997.—We describe a simple apparatus for analysis of perfluorochemicals (PFC) in expired gas and thus a means for determining PFC vapor and liquid elimination from the respiratory system. The apparatus and data analysis are based on thermal conduction and mass transfer principles of gases. In vitro studies were conducted with the PFC vapor analyzer to determine calibration curves for output voltage as a function of individual respiratory gases, respiratory gases saturated with PFC vapor, and volume percent standards for percent PFC saturation (%PFC-Sat) in air. Voltage-concentration data for %PFC-Sat of the vapor from the in vitro tests were accurate to within 2.0% from 0 to 100% PFC-Sat, linear ( r = 0.99, P < 0.001), and highly reproducible. Calculated volume loss of PFC liquid over time correlated well with actual loss by weight ( r = 0.99, P < 0.001). In vivo studies with neonatal lambs demonstrated that PFC volume loss and evaporation rates decreased nonlinearly as a function of time. These relationships were modulated by changes in PFC physical properties, minute ventilation, and postural repositioning. The results of this study demonstrate the sensitivity and accuracy of an on-line method for PFC analysis of expired gas and describe how it may be useful in liquid-assisted ventilation procedures for determining PFC volume loss, evaporation rate, and optimum dosing and ventilation strategy.

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