A-a difference in O<sub>2</sub> tension and physiological dead space in normal man

Raine, June; Bishop, Jonathan

doi:10.1152/jappl.1963.18.2.284

Cited by 203 publications

(93 citation statements)

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“…Breathing room air, PA−aO 2 is usually 5-10 mmHg in young healthy subjects, but it increases a little with age to up to 20 mmHg or so [21,22]. Unfortunately, PA−aO 2 is a noisy variable because it represents the usually small difference between two large numbers (alveolar and arterial PO 2 ).…”

Section: Assessment and Interpretation Of Arterial Blood Gasesmentioning

confidence: 99%

The physiological basis of pulmonary gas exchange: implications for clinical interpretation of arterial blood gases

Wagner

2014

Eur Respir J

124

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Number 8 in the series "Physiology in respiratory medicine" Edited by R. Naeije, D. Chemla, A. Vonk-Noordegraaf and A.T. Dinh-Xuan Affiliation: Dept of Medicine, University of California, San Diego, La Jolla, CA, USA.Correspondence: Peter D. Wagner, Dept of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA. E-mail: pdwagner@ucsd.edu ABSTRACT The field of pulmonary gas exchange is mature, with the basic principles developed more than 60 years ago. Arterial blood gas measurements (tensions and concentrations of O 2 and CO 2 ) constitute a mainstay of clinical care to assess the degree of pulmonary gas exchange abnormality. However, the factors that dictate arterial blood gas values are often multifactorial and complex, with six different causes of hypoxaemia (inspiratory hypoxia, hypoventilation, ventilation/perfusion inequality, diffusion limitation, shunting and reduced mixed venous oxygenation) contributing variably to the arterial O 2 and CO 2 tension in any given patient. Blood gas values are then usually further affected by the body's abilities to compensate for gas exchange disturbances by three tactics (greater O 2 extraction, increasing ventilation and increasing cardiac output). This article explains the basic principles of gas exchange in health, mechanisms of altered gas exchange in disease, how the body compensates for abnormal gas exchange, and based on these principles, the tools available to interpret blood gas data and, quantitatively, to best understand the physiological state of each patient. This understanding is important because therapeutic intervention to improve abnormal gas exchange in any given patient needs to be based on the particular physiological mechanisms affecting gas exchange in that patient. @ERSpublications Understanding the physiological basis of pulmonary gas exchange can help guide therapeutic approaches to patients

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Section: Assessment and Interpretation Of Arterial Blood Gasesmentioning

confidence: 99%

The physiological basis of pulmonary gas exchange: implications for clinical interpretation of arterial blood gases

Wagner

2014

Eur Respir J

124

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“…There was a statistically significant difference in age between the subject and control groups, but it seems unlikely that this difference influenced ventilatory responses, as might be expected from the higher VD/VT associated with more advanced age, as age-associated increases have been estimated at < 0.1%/year. 45 …”

Section: Study Limitationsmentioning

confidence: 99%

Exercise Oscillatory Ventilation

Olson

Arruda‐Olson

Somers

et al. 2008

Chest

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Background-Instability of breathing control due to heart failure (HF) manifests as exercise oscillatory ventilation (EOV). Prior descriptions of patients with EOV have not been controlled and have been limited to subjects with left ventricular ejection fraction (LVEF) of ≤ 0.40. The aim of this study was to compare clinical characteristics including ventilatory responses of subjects with EOV to those of control subjects with HF matched for LVEF.

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“…25 The latter is due at least in part to a decline in CO 2 production associated with a decrease in basal metabolic rate. Several equations have been proposed to predict the PaO 2 as a function of age.…”

Section: Gas Exchangementioning

confidence: 99%

Review article: Age related alterations in respiratory function — anesthetic considerations

Šprung

Gajic

Warner

2006

Can J Anesth/J Can Anesth

143

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Purpose: This review examines the effect of aging on pulmonary reserve. Special emphasis is placed on how anesthetic and surgical factors may impose substantial stresses on the respiratory system of elderly patients, leading to increased risk for postoperative pulmonary complications including respiratory failure.Source: A MEDLINE-based English-language literature search was undertaken for the period 1966-2006, and an EMBASE search covered the overlapping period 1988-2006. Selected articles were limited to those applying to elderly subjects/patients. Principal findings:Age-related loss of the lung static recoil forces, stiffening of the chest wall and diminished alveolar surface area lead to a decrease in vital capacity, an increase in residual volume, decrease in expiratory flows and increased ventilation-perfusion heterogeneity. Respiratory muscle strength consistently declines with age further increasing the work of breathing. While gas exchange may be well preserved at rest and during exertion, pulmonary reserve is diminished, and under conditions of positive fluid balance, positioning for surgery, and increased metabolic demand, postoperative respiratory failure can occur. Increased sensitivity to respiratory depressants and muscle weakness pose additional risks for the development of postoperative respiratory complications in elderly patients. Regional anesthetic techniques provide for superior postoperative analgesia, without necessarily altering the frequency of postoperative pulmonary complications in the older surgical population. Conclusion:Alterations in respiratory physiology associated with aging must be appreciated to anticipate and minimize potential complications associated with surgery and anesthesia in the elderly. Individualized care to optimize preoperative cardiorespiratory function, minimize intraoperative respiratory pertubations, and to gently restore postoperative pulmonary function are essential anesthetic goals for elderly patients who require surgery. Objectif

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A-a difference in O₂ tension and physiological dead space in normal man

Cited by 203 publications

References 0 publications

The physiological basis of pulmonary gas exchange: implications for clinical interpretation of arterial blood gases

The physiological basis of pulmonary gas exchange: implications for clinical interpretation of arterial blood gases

Exercise Oscillatory Ventilation

Review article: Age related alterations in respiratory function — anesthetic considerations

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A-a difference in O2 tension and physiological dead space in normal man

Cited by 203 publications

References 0 publications

The physiological basis of pulmonary gas exchange: implications for clinical interpretation of arterial blood gases

The physiological basis of pulmonary gas exchange: implications for clinical interpretation of arterial blood gases

Exercise Oscillatory Ventilation

Review article: Age related alterations in respiratory function — anesthetic considerations

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A-a difference in O₂ tension and physiological dead space in normal man