A theoretical analysis of the barometric method for measurement of tidal volume

Epstein, Miles L.; Epstein, Robert

doi:10.1016/0034-5687(78)90103-2

Cited by 121 publications

(93 citation statements)

References 8 publications

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“…In fact, expired air more closely approaches nasal rather than chamber conditions, depending on nasal temperature, the temperature and humidity of the chamber, and TI/T Tot . Overlooking these factors could lead to a substantial underestimation of VT that worsens as TI /T Tot and/or the expired temperature at the nares increases (9,14). The question is whether these factors could have affected the daily pattern of hypercapnic hyperventilation.…”

Section: Discussionmentioning

confidence: 99%

Circadian pattern of ventilation during acute and chronic hypercapnia in conscious adult rats

Seifert

Mortola

2002

American Journal of Physiology-Regulatory, Integrative and Comp

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Seifert, Erin L., and Jacopo P. Mortola. Circadian pattern of ventilation during acute and chronic hypercapnia in conscious adult rats. Am J Physiol Regulatory Integrative Comp Physiol 282: R244-R251, 2002; 10.1152/ajpregu. 00290.2001.-Because metabolism is a determinant of the ventilatory chemosensitivity, we tested the hypothesis that the ventilatory response to acute and prolonged hypercapnia is adjusted to the circadian oscillations in oxygen consumption (V O2). Adult rats were instrumented for measurements of body temperature (Tb) and activity by telemetry. Pulmonary ventilation (V E) was measured by the barometric method and V O2 by the flow-through method. In the acute experiments, 16 conscious rats entrained to a 12:12-h light (L)-dark (D) cycle (lights on 7:00 AM) were exposed to air, 2%, and then 5% CO2 in normoxia (30-45 min each) at 11:00 AM and 11:00 PM. In a separate group of seven rats, simultaneous recordings of all variables were made continuously for 3 consecutive days in air followed by 3 days in 2% CO2 in normoxia, in a 12:12-h L-D cycle (lights on 7:00 AM). In air, all variables were significantly higher at night, whether rats were studied acutely or chronically. Acute CO2 exposure had similar significant effects at 11:00 AM and 11:00 PM on V E (ϳ25 and 100% increase with 2 and 5% CO2, respectively) and V O2 (ϳ8% drop with 5% CO2), such that the hyperventilatory response (% increase in V E/V O2 from air) was similar at both times. Chronic CO2 breathing increased V E at all times of the day, but less so during the L phase (ϳ15 vs. 22% increase in L and D, respectively), when activity was lower. However, V O2 was reduced from the air level (ϳ10% drop) in the L, such that the V E/V O2 response was similar between L and D. The same result was obtained when the V E/V O2 response was compared between the L and D phases for the same level of activity. These results suggest that, throughout the day, the hypercapnic hyperpnea, whether during acute or prolonged CO2, is perfectly adjusted to the metabolic level.control of breathing; chemosensitivity; barometric method; oxygen consumption IN MAMMALS AND BIRDS, blood gas homeostasis depends on the matching of pulmonary ventilation (V E) to metabolism. Indeed, a close coupling between V E and oxygen consumption (V O 2 ) has been found under a variety of conditions where V O 2 is either raised or lowered (20). Variations in metabolism are also associated with changes in V E chemosensitivity (19). A higher V O 2 , as during muscular exercise (35) or cold exposure (12), is accompanied by a greater absolute increase in V E in response to acute hypoxia or hypercapnia, whereas reflex hyperpnea is lower whenVO 2 is reduced, such as with myxedema (36) or semi-starvation (6). Hence, the V E chemoreflex response seems to track V O 2 . This would tend to minimize fluctuations in blood gases in normoxia and when chemosensory drive is elevated.Oxygen consumption presents a circadian oscillation. Although the daily high values of V O 2 generally occur when an animal i...

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Section: Discussionmentioning

confidence: 99%

Circadian pattern of ventilation during acute and chronic hypercapnia in conscious adult rats

Seifert

Mortola

2002

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Third, we used the method of Drorbaugh and Fenn (7) to measure V t in the unrestrained conscious mice from the box pressure excursions at room temperature. No corrections were made for nasal temperature (9,12), and these errors have been estimated to be less than 30%. An underestimate of V t by 30% would produce an overestimate of R aw by ϳ30%.…”

Section: Methodsmentioning

confidence: 99%

“…[6][7][8][9]. If only turbulent flow conditions were to exist, the alveolar driving pressure would be proportional to Q 2 with a constant of proportionality Rt:…”

Section: Assumption Of Turbulent Flow Conditionsmentioning

confidence: 99%

“…Drorbaugh and Fenn (7) showed that tidal volume (V t ) is related to excursions in box pressure caused by changes in temperature and humidity of the airflow from the box to the alveolar space. This method for measuring V t has been validated in studies of newborn infants (7), monkeys (12), and mice (22); however, its accuracy has been questioned (9). The measurement of airway responsiveness from the cyclic variations of box pressure (17,19) has been criticized because of the compounding effects of alveolar gas compression and the effects of temperature and humidity (gas conditioning).…”

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confidence: 99%

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Airway resistance due to alveolar gas compression measured by barometric plethysmography in mice

Lai-Fook¹,

Lai²

2005

Journal of Applied Physiology

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. Airway resistance due to alveolar gas compression measured by barometric plethysmography in mice. J Appl Physiol 98: 2204 -2218, 2005. First published January 27, 2005 doi:10.1152/japplphysiol.00869.2004.-We developed a method for measuring airway resistance (R aw) in mice that does not require a measurement of airway flow. An analysis of R aw induced by alveolar gas compression showed the following relationship for an animal breathing spontaneously in a closed box: R aw ϭ A btVb/[Vt (Ve ϩ 0.5Vt)]. Here Abt is the area under the box pressuretime curve during inspiration or expiration, V b is box volume, Vt is tidal volume, and V e is functional residual capacity (FRC). In anesthetized and conscious unrestrained mice, from experiments with both room temperature box air and body temperature humidified box air, the contributions of gas compression to the box pressure amplitude were 15 and 31% of those due to the temperature-humidity difference between box and alveolar gas. We corrected the measured Abt and Vt for temperature-humidity and gas compression effects, respectively, using a sinusoidal analysis. In anesthetized mice, Raw averaged 4.3 cmH 2O ⅐ ml Ϫ1 ⅐ s, fourfold greater than pulmonary resistance measured by conventional methods. In conscious mice with an assumed FRC equal to that measured in the anesthetized mice, the corrected R aw at room temperature averaged 1.9 cmH 2O ⅐ ml Ϫ1 ⅐ s. In both conscious mice and anesthetized mice, exposure to aerosolized methacholine with room temperature box air significantly increased R aw by around eightfold. Here we assumed that in the conscious mice both V t and FRC remained constant. In both conscious and anesthetized mice, body temperature humidified box air reduced the methacholine-induced increase in Raw observed at room temperature. The method using the increase in A bt with bronchoconstriction provides a conservative estimate for the increase in Raw in conscious mice. bronchoconstriction; methacholine; tidal volume; gas conditioning; conscious mice; anesthetized mice AIRWAY RESISTANCE (R aw ) in small animals is used to evaluate the efficacy of pharmacological agents in the treatment of allergic airway disease. In particular, the use of barometric plethysmography with conscious unrestrained mice in a closed box is particularly appealing because of its noninvasiveness and technical simplicity. Drorbaugh and Fenn (7) showed that tidal volume (V t ) is related to excursions in box pressure caused by changes in temperature and humidity of the airflow from the box to the alveolar space. This method for measuring V t has been validated in studies of newborn infants (7), monkeys (12), and mice (22); however, its accuracy has been questioned (9). The measurement of airway responsiveness from the cyclic variations of box pressure (17, 19) has been criticized because of the compounding effects of alveolar gas compression and the effects of temperature and humidity (gas conditioning). Lundblad et al. (17) from experiments in anesthetized mice concluded that the contribu...

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“…The ambient temperature inside the measurement chamber during ventilatory measurements was 25.0 Ϯ 2.3°C. The mean temperature increase inside the measurement chamber was Ͻ0.6°C, a value that has been shown to cause a Ͻ1% error in VT measurements (9). The water partial pressure in the barometric chamber (which entered into Drorbaugh and Fenn's equation for VT calculation) was assumed to be kept at zero by the dry gas flushing the plethysmograph.…”

Section: Ventilatory Measurementsmentioning

confidence: 99%

Impaired Ventilatory Responses to Hypoxia in Mice Deficient in Endothelin-Converting-Enzyme-1

et al. 2001

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Endothelin-converting-enzyme (ECE-1) catalyzes the proteolytic activation of big endothelin-1 to mature endothelin-1. Most homozygous ECE-1Ϫ/Ϫ embryos die in utero and show severe craniofacial, enteric, and cardiac malformations precluding ventilatory function assessment. In contrast, heterozygous ECE-1ϩ/Ϫ embryos develop normally. Their respiratory function at birth has not been studied. Taking into account previous respiratory investigations in mice with endothelin-1 gene disruption, we hypothesized that ECE-1-deficient mice may have impaired ventilatory control. We analyzed ventilatory responses to hypercapnia (8% CO 2 ) and hypoxia (10% O 2 ) in newborn and adult mice heterozygous for ECE-1 deficiency (ECE-1ϩ/Ϫ) and in their wild-type littermates (ECE-1ϩ/ϩ). Ventilation, breath duration, and tidal volume were measured using whole-body plethysmography. Ventilatory responses to hypoxia were significantly weaker in ECE-1ϩ/Ϫ than in ECE-1ϩ/ϩ newborn mice (percentage ventilation increase: 1 Ϯ 25% versus 33 Ϯ 29%, p ϭ 0.010). Baseline breathing variables and ventilatory responses to hypercapnia were normal in the ECE-1ϩ/Ϫ newborn mice. No differences were observed between adult ECE-1ϩ/Ϫ and ECE-1ϩ/ϩ mice. We conclude that ECE-1 is required for normal ventilatory response to hypoxia at birth. Abbreviations CCHS, congenital central hypoventilation syndrome ECE-1, endothelin-converting-enzyme-1 ET-1, endothelin-1 GDNF, glial-cell-line-derived neurotrophic factor HSCR, Hirschsprung's disease NTS, nucleus tractus solitarius RET, rearranged during transfection TTOT, breath duration VE, ventilation VT, tidal volume ECE-1 catalyzes the proteolytic activation of big ET-1 to mature ET-1 (1, 2). Targeted ECE-1 gene disruption, which has recently been achieved in mice, has important effects on embryonic development and autonomic functions (3). Among homozygous ECE-1Ϫ/Ϫ embryos, most die in utero (about 75% in a C57BL/6 -129SvEv hybrid background) and all exhibit craniofacial, enteric, and cardiac malformations (3) that preclude valid ventilatory function assessment. In contrast, heterozygous ECE-1ϩ/Ϫ newborns are apparently healthy and develop normally. In a recent study, the differences in respiratory function between adult heterozygous ECE-1ϩ/Ϫ and wild-type ECE-1ϩ/ϩ adult mice were found to be not significant (4). Newborn mice were not studied. In the present study, we tested the ventilatory responses to chemical stimuli in heterozygous ECE-1ϩ/Ϫ newborn mice, and we reexamined the normality of adult heterozygous ECE-1ϩ/Ϫ mice in a larger sample of mice than previously done (4).Our working hypothesis was based on previous data showing that ET-1 is required for normal ventilatory control. First, in anesthetized rats, topical applications of ET-1 in the chemosensitive area of the ventral medulla oblongata and other areas involved in respiratory control cause changes in phrenic nerve activity (2). Specifically, applications of ET-1 in regions extending between the caudal end of the trapezoid body and the rootlets of the XIIth ...

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A theoretical analysis of the barometric method for measurement of tidal volume

Cited by 121 publications

References 8 publications

Circadian pattern of ventilation during acute and chronic hypercapnia in conscious adult rats

Circadian pattern of ventilation during acute and chronic hypercapnia in conscious adult rats

Airway resistance due to alveolar gas compression measured by barometric plethysmography in mice

Impaired Ventilatory Responses to Hypoxia in Mice Deficient in Endothelin-Converting-Enzyme-1

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