Studies of alveolar-mixed venous CO2 and O2 gradients in the rebreathing dog lung

Guyatt, A. R.; Yu, Chuangqi; Lutherer, Berta; Otis, Arthur B.

doi:10.1016/0034-5687(73)90060-1

Cited by 13 publications

(1 citation statement)

References 4 publications

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“…Although this P

_{ET,CO_{2}}

– P

_{a,CO_{2}}

overestimation was present at comparable time points to the current study, Laszlo et al (1971) considered this to be a transient phenomenon since the P

_{ET,CO_{2}}

and P

_{a,CO_{2}}

were similar after 10 min. Also, in animals P

_{ET,CO_{2}}

overestimates P

_{a,CO_{2}}

during rebreathing (Guyatt et al 1973) and steady‐state methods (Jennings & Chen, 1975; Tojima et al 1988) of CO 2 administration. Whilst it appears that a definitive mechanism for the P

_{ET,CO_{2}}

– P

_{a,CO_{2}}

gradient has not been established, Gurtner & Traystman (1979) proposed the ‘charged membrane hypothesis’, which ultimately results in the production of CO 2 in the region of the negatively charged alveolar capillary wall and in turn creates a positive gradient for CO 2 between the alveolar gas and pulmonary arterial blood.…”

Section: Discussionmentioning

confidence: 93%

Human cerebrovascular and ventilatory CO₂ reactivity to end‐tidal, arterial and internal jugular vein P_CO2

Peebles¹,

Celi²,

McGrattan³

et al. 2007

The Journal of Physiology

134

146

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This study examined cerebrovascular reactivity and ventilation during step changes in CO 2 in humans. We hypothesized that: (1) end-tidal P CO 2 (P ET,CO 2 ) would overestimate arterial P CO 2 (P a,CO 2 ) during step variations in P ET,CO 2 and thus underestimate cerebrovascular CO 2 reactivity; and (2) sinceP CO 2 from the internal jugular vein (P jv,CO 2 ) better represents brain tissueP CO 2 , cerebrovascular CO 2 reactivity would be higher when expressed against P jv,CO 2 than with P a,CO 2 , and would be related to the degree of ventilatory change during hypercapnia. Incremental hypercapnia was achieved through 4 min administrations of 4% and 8% CO 2 . Incremental hypocapnia involved two 4 min steps of hyperventilation to changeP ET,CO 2 , in an equal and opposite direction, to that incurred during hypercapnia. Arterial and internal jugular venous blood was sampled simultaneously at baseline and during each CO 2 step. Cerebrovascular reactivity to CO 2 was expressed as the percentage change in blood flow velocity in the middle cerebral artery (MCAv) per mmHg change in P a,CO 2 and P jv,CO 2 . During hypercapnia, but not hypocapnia, P ET,CO 2 overestimated P a,CO 2 by +2.4 ± 3.4 mmHg and underestimated MCAv-CO 2 reactivity (P < 0.05). The hypercapnic and hypocapnic MCAv-CO 2 reactivity was higher (∼97% and ∼24%, respectively) when expressed with P jv,CO 2 than P a,CO 2 (P < 0.05). The hypercapnic MCAv-P jv,CO 2 reactivity was inversely related to the increase in ventilatory change (R 2 = 0.43; P < 0.05), indicating that a reduced reactivity results in less central CO 2 washout and greater ventilatory stimulus. Differences in the P ET,CO 2 , P a,CO 2 and P jv,CO 2 -MCAv relationships have implications for the true representation and physiological interpretation of cerebrovascular CO 2 reactivity.

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“…Although this P

_{ET,CO_{2}}

– P

_{a,CO_{2}}

overestimation was present at comparable time points to the current study, Laszlo et al (1971) considered this to be a transient phenomenon since the P

_{ET,CO_{2}}

and P

_{a,CO_{2}}

were similar after 10 min. Also, in animals P

_{ET,CO_{2}}

overestimates P

_{a,CO_{2}}

during rebreathing (Guyatt et al 1973) and steady‐state methods (Jennings & Chen, 1975; Tojima et al 1988) of CO 2 administration. Whilst it appears that a definitive mechanism for the P

_{ET,CO_{2}}

– P

_{a,CO_{2}}

Section: Discussionmentioning

confidence: 93%

Human cerebrovascular and ventilatory CO₂ reactivity to end‐tidal, arterial and internal jugular vein P_CO2

Peebles¹,

Celi²,

McGrattan³

et al. 2007

The Journal of Physiology

134

146

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Ventilation: Total, Alveolar, and Dead Space

Anthonisen

Fleetham

1987

Comprehensive Physiology

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Relationships between Blood and Extravascular Pco2, [H+] and [HCO3 −] in Lung, Cerebrospinal Fluid, and Brain

Gurtner

Burns

Sciuto

et al. 1974

Topics in Environmental Physiology and Medicine

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Studies of alveolar-mixed venous CO2 and O2 gradients in the rebreathing dog lung

Cited by 13 publications

References 4 publications

Human cerebrovascular and ventilatory CO₂ reactivity to end‐tidal, arterial and internal jugular vein P_CO2

Human cerebrovascular and ventilatory CO₂ reactivity to end‐tidal, arterial and internal jugular vein P_CO2

Ventilation: Total, Alveolar, and Dead Space

Relationships between Blood and Extravascular Pco2, [H+] and [HCO3 −] in Lung, Cerebrospinal Fluid, and Brain

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Studies of alveolar-mixed venous CO2 and O2 gradients in the rebreathing dog lung

Cited by 13 publications

References 4 publications

Human cerebrovascular and ventilatory CO2 reactivity to end‐tidal, arterial and internal jugular vein PCO2

Human cerebrovascular and ventilatory CO2 reactivity to end‐tidal, arterial and internal jugular vein PCO2

Ventilation: Total, Alveolar, and Dead Space

Relationships between Blood and Extravascular Pco2, [H+] and [HCO3 −] in Lung, Cerebrospinal Fluid, and Brain

Contact Info

Product

Resources

About

Human cerebrovascular and ventilatory CO₂ reactivity to end‐tidal, arterial and internal jugular vein P_CO2

Human cerebrovascular and ventilatory CO₂ reactivity to end‐tidal, arterial and internal jugular vein P_CO2