Cardiopulmonary response to exercise in patients with intrapulmonary vascular shunts

M. K B Whyte, J. M B Hughes, J. E. Jackson, A. M. Peters, Steven C Hempleman, D. P. Moore, H. A. Jones

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Abstract

The majority of patients with intrapulmonary right-to-left shunting due to pulmonary arteriovenous malformations exhibit good maximum exercise capacity (>70% predicted) despite profound arterial oxygen desaturation. We studied seven such patients to assess tissue oxygen delivery during steady-state exercise. From rest to exercise [50 ± 7 (SE) W] arterial saturation fell from 80 ± 3 to 74 ± 3%, and mean right-to-left shunt increased slightly from 31 ± 4 to 34 ± 5% (P = NS). Minute ventilation was high for oxygen uptake, and the ventilatory equivalent was raised (174 ± 19% predicted) and was correlated with shunt size (r = 0.93). The majority of the patients maintained pulmonary alveolar blood flow within the predicted range for their power output, but total cardiac output was increased to 142 ± 11% predicted due to flow through the shunt. Consequently, on exercise, oxygen delivery per unit oxygen consumption [2.3-3.3 (normal range 1.6-2.4)] and calculated mixed venous oxygen tension (27.0 ± 0.8 Torr) were preserved. Arterial PCO2 rose on exercise by 2.8 ± 1.2 Torr, in proportion to the ratio of flow through the shunt to total cardiac output (r = 0.73), but remained low (33.1 ± 1.4 Torr) in absolute terms. The high cardiac output on exercise may be facilitated by a low pulmonary vascular resistance (0.33 ± 0.08 mmHg · l- 1 · min, measured at rest), which may explain why exercise performance is better in these patients than in patients with equivalent hypoxemia from other causes.

Original languageEnglish (US)
Pages (from-to)321-328
Number of pages8
JournalJournal of Applied Physiology
Volume75
Issue number1
StatePublished - 1993
Externally publishedYes

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Keywords

  • exercise hypoxemia
  • pulmonary arteriovenous malformations
  • right-to-left shunt

ASJC Scopus subject areas

  • Endocrinology
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Whyte, M. K. B., Hughes, J. M. B., Jackson, J. E., Peters, A. M., Hempleman, S. C., Moore, D. P., & Jones, H. A. (1993). Cardiopulmonary response to exercise in patients with intrapulmonary vascular shunts. Journal of Applied Physiology, 75(1), 321-328.