Key result
Hypercapnia (pCO2 60-75 mm Hg) reduced stroke work to 73.6% of control values when heart rate and left atrial pressure were constant, whereas hypocapnia had no consistent effect.
Why the study?
Does hypercapnia or hypocapnia affect myocardial contractility in an experimental preparation?
Does hypercapnia or hypocapnia affect myocardial contractility in an experimental preparation?
Hypercapnia, but not hypocapnia, depresses myocardial contractility when heart rate and left atrial pressure are held constant.
Answers are grounded in this paper and cite their sources.
Hypercapnia may impair myocardial contractility independently of HR and LAP in animals; leaves open clinical relevance during ventilation or in patients.
Moderate elevations of pCO2 (61–75 mm Hg) did not consistently depress myocardial contractility as determined by standard ventricular function curves. With an altered preparation in which heart rate and left atrial pressure were held constant, a pCO2 of 60–75 mm Hg was accompanied by an average reduction in stroke work to 73.6% of its control value, while hypocapnia with an alveolar pCO2 of 6–13 mm Hg was unaccompanied by any consistent reduction in stroke work.
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MONROE et al. (1960) studied Myocardial contractility. Hypercapnia and hypocapnia vs. Control value was evaluated on Stroke work. Hypercapnia (pCO2 60-75 mm Hg) reduced stroke work to 73.6% of control values when heart rate and left atrial pressure were constant, whereas hypocapnia had no consistent effect.
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