Cardiovascular responses to local hindlimb hypoxia: Relation to the exercise reflex

J. Longhurst, Robert Zelis

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19 Citations (Scopus)

Abstract

Although reflex cardiovascular responses from skeletal muscle are thought to play a role in cardiovascular regulation during exercise, the mechanism of somatic efferent nerve stimulation is unknown. To evaluate the possibility that regional skeletal muscle hypoxemia or hypercapnia-acidosis might play a role in this response, the hindlimbs of 13 chloralose-urethan-anesthetized dogs were vascularly isolated below the renal vessels and perfused at a constant flow via an extracorporeal disk oxygenator pump while the systemic cardiovascular system was monitored separately. When the oxygenator gas mixture was changed to create regional hindlimb hypoxemia (Po2, 290 to 27 mmHg, P<0.001) there was an increase in heart rate (160 to 179 beats/min, P<0.001), systemic mean blood pressure (99 to 111 mmHg, P< 0.001), systemic vascular resistance (95 to 194 mmHg.min/l, P <0.01), and brachial arterial resistance (19 to 38 mmHg.min/ml, P<0.02), but a decrease in aortic flow (1163 to 793 ml/min, P<0.001) and brachial arterial flow (6.6 to 3.9 ml/min, P < 0.001). When the oxygenator gas mixture was changed to create regional hindlimb hypercapnia and acidosis (PCO2, 43 to 115 mmHg, P<0.001; pH 7.39 to 7.05, P< 0.001), there were no significant changes in any systemic cardiovascular parameters. Therefore, only hindlimb hypoxemia of the degree present during severe exercise and/or metabolite(s) secondary to hypoxemia can elicit cardiovascular adjustments similar to those observed during exercise.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume6
Issue number3
StatePublished - Jan 1 1979

Fingerprint

Hindlimb
Oxygenators
Reflex
Hypercapnia
Acidosis
Skeletal Muscle
Arm
Gases
Chloralose
Urethane
Cardiovascular System
Vascular Resistance
Heart Rate
Dogs
Blood Pressure
Kidney
Hypoxia

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

Cite this

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abstract = "Although reflex cardiovascular responses from skeletal muscle are thought to play a role in cardiovascular regulation during exercise, the mechanism of somatic efferent nerve stimulation is unknown. To evaluate the possibility that regional skeletal muscle hypoxemia or hypercapnia-acidosis might play a role in this response, the hindlimbs of 13 chloralose-urethan-anesthetized dogs were vascularly isolated below the renal vessels and perfused at a constant flow via an extracorporeal disk oxygenator pump while the systemic cardiovascular system was monitored separately. When the oxygenator gas mixture was changed to create regional hindlimb hypoxemia (Po2, 290 to 27 mmHg, P<0.001) there was an increase in heart rate (160 to 179 beats/min, P<0.001), systemic mean blood pressure (99 to 111 mmHg, P< 0.001), systemic vascular resistance (95 to 194 mmHg.min/l, P <0.01), and brachial arterial resistance (19 to 38 mmHg.min/ml, P<0.02), but a decrease in aortic flow (1163 to 793 ml/min, P<0.001) and brachial arterial flow (6.6 to 3.9 ml/min, P < 0.001). When the oxygenator gas mixture was changed to create regional hindlimb hypercapnia and acidosis (PCO2, 43 to 115 mmHg, P<0.001; pH 7.39 to 7.05, P< 0.001), there were no significant changes in any systemic cardiovascular parameters. Therefore, only hindlimb hypoxemia of the degree present during severe exercise and/or metabolite(s) secondary to hypoxemia can elicit cardiovascular adjustments similar to those observed during exercise.",
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N2 - Although reflex cardiovascular responses from skeletal muscle are thought to play a role in cardiovascular regulation during exercise, the mechanism of somatic efferent nerve stimulation is unknown. To evaluate the possibility that regional skeletal muscle hypoxemia or hypercapnia-acidosis might play a role in this response, the hindlimbs of 13 chloralose-urethan-anesthetized dogs were vascularly isolated below the renal vessels and perfused at a constant flow via an extracorporeal disk oxygenator pump while the systemic cardiovascular system was monitored separately. When the oxygenator gas mixture was changed to create regional hindlimb hypoxemia (Po2, 290 to 27 mmHg, P<0.001) there was an increase in heart rate (160 to 179 beats/min, P<0.001), systemic mean blood pressure (99 to 111 mmHg, P< 0.001), systemic vascular resistance (95 to 194 mmHg.min/l, P <0.01), and brachial arterial resistance (19 to 38 mmHg.min/ml, P<0.02), but a decrease in aortic flow (1163 to 793 ml/min, P<0.001) and brachial arterial flow (6.6 to 3.9 ml/min, P < 0.001). When the oxygenator gas mixture was changed to create regional hindlimb hypercapnia and acidosis (PCO2, 43 to 115 mmHg, P<0.001; pH 7.39 to 7.05, P< 0.001), there were no significant changes in any systemic cardiovascular parameters. Therefore, only hindlimb hypoxemia of the degree present during severe exercise and/or metabolite(s) secondary to hypoxemia can elicit cardiovascular adjustments similar to those observed during exercise.

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