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Open Access Research

Minute ventilation and heart rate relationship for estimation of the ventilatory compensation point at high altitude: a pilot study

Gabriele Valli1*, Mattia Internullo1, Alessandro M Ferrazza1, Paolo Onorati1, Annalisa Cogo2 and Paolo Palange13

Author Affiliations

1 Lung Function Unit, Department of Public Health and Infectious Diseases, University of Rome “La Sapienza”, viale Università 37, Rome, 00185, Italy

2 Biomedical Sport Studies Center, University of Ferrara, Via Gramicia 35, Ferrara, 44123, Italy

3 Eleonora Lorillard Spencer Cenci Foundation, Piazzale Aldo Moro n. 5, Rome, 00185, Italy

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Extreme Physiology & Medicine 2013, 2:7  doi:10.1186/2046-7648-2-7

Published: 1 March 2013

Abstract

Background

The ventilatory compensation point (VCP) is an exercise threshold which has been used in the design of training programs in sports medicine and rehabilitation. We recently demonstrated that changes in the slope of the minute ventilation to heart rate relationship (<a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M1','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M1">View MathML</a>) can be utilized for estimation of the VCP during incremental exercise at sea level (SL). We hypothesized that in hypoxic conditions, such as high altitude (HA), VCP can be also reliably estimated by <a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M2','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M2">View MathML</a>.

Methods

At SL and on immediate ascent to HA (5,050 m), six healthy subjects (42 ± 14 SD years) performed a maximal incremental exercise test on a cycle ergometer; O2 uptake (<a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M3','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M3">View MathML</a>), CO2 output (<a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M4','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M4">View MathML</a>), <a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M5','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M5">View MathML</a>, and HR were measured breath-by-breath. The <a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M6','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M6">View MathML</a> method for VCP estimation was compared to the standard method using the ventilatory equivalent for CO2 (<a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M7','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M7">View MathML</a>) and end-tidal PCO2 (PETCO2). The <a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M8','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M8">View MathML</a> slope values below (S1) and above (S2) VCP were computed by linear regression analysis.

Results

A significant difference between S1 and S2 was observed, at SL and HA, for both the <a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M9','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M9">View MathML</a> and <a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M10','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M10">View MathML</a> methods for VCP estimation. A good agreement between the two methods (<a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M11','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M11">View MathML</a> vs. <a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M12','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M12">View MathML</a>) was found for both environmental conditions; the mean difference ± 2 SD of <a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M13','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M13">View MathML</a> at VCP (VCP-<a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M14','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M14">View MathML</a>) was −22 ± 112 ml/min at SL and 39 ± 81 ml/min at HA. The VCP-<a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M15','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M15">View MathML</a> was significantly lower at HA compared to SL; in addition, S1 and S2 mean values were significantly higher at HA compared to SL.

Conclusion

At HA, VCP may be reliably estimated by the <a onClick="popup('http://www.extremephysiolmed.com/content/2/1/7/mathml/M16','MathML',630,470);return false;" target="_blank" href="http://www.extremephysiolmed.com/content/2/1/7/mathml/M16">View MathML</a> method.

Keywords:
High altitude; Ventilatory compensation point; Exercise; Ventilation; Heart rate