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A final message from Prof. Paolo Palange at the end of his mandate as ERS School Chair 2008-2011
A non invasive estimate of dead space ventilation from exercise measurements
During exercise, heart failure patients (HF) show an out-of-proportion ventilation increase, which in patients with COPD is blunted. When HF and COPD coexist, the ventilatory response to exercise is unpredictable.
OBJECTIVES:
We evaluated a human model of respiratory impairment in 10 COPD-free HF patients and in 10 healthy subjects, tested with a progressive workload exercise with different added dead space. We hypothesized that increased serial dead space upshifts the VE vs. VCO2 relationship and that the VE-axis intercept might be an index of dead space ventilation.
MEASUREMENTS:
All participants performed a cardiopulmonary exercise test with 0, 250 and 500 mL of additional dead space. Since DS does not contribute to gas exchange, ventilation relative to dead space is ventilation at VCO2 = 0, i.e. VE-axis intercept. We compared dead space volume, estimated dividing VE-axis intercept by the intercept on respiratory rate axis of the respiratory rate vs. VCO2 relationship with standard method measured DS.
MAIN RESULTS:
In HF, adding dead space increased VE-axis intercept (+0 mL = 4.98±1.63 L; +250 mL = 9.69±2.91 L; +500 mL = 13.26±3.18 L; p<0.001) and upshifted the VE vs.VCO2 relationship, with a minor slope rise (+0 mL = 27±4 L; +250 = 28±5; +500 = 29±4; p<0.05). In healthy, adding dead space increased VE-axis intercept (+0 mL = 4.9±1.4 L; +250 = 9.3±2.4; +500 = 13.1±3.04; p<0.001) without slope changes. Measured and estimated dead space volumes were similar both in HF and healthy subjects.
CONCLUSIONS:
VE-axis intercept is related to dead space ventilation and dead space volume can be non-invasively estimated
The major limitation to exercise performance in COPD is inadequate energy supply to the respiratory and locomotor muscles vs. lower limb muscle dysfunction vs. dynamic hyperinflation. "In medio stat virtus."
Management of COPD: surgical options
Dyspnoea on exertion and exercise intolerance are the hallmarks of chronic obstructive pulmonary disease (COPD); the primary causes appear to be respectively, increased airway resistance with reduced maximal ventilatory capacity and peripheral skeletal muscle dysfunction with early onset of anaerobic metabolism. Patients with end-stage COPD usually show little or no benefit from conventional medical treatment. Physical training is capable of ameliorating exercise tolerance, but improvement is usually modest in the advanced disease state. Two surgical options are generally accepted for carefully selected patients with emphysema: resection of large bullae, when identified, and lung transplantation. Transplantation, the only effective cure for advanced COPD, is of limited use primarily because of age, comorbidity, limited availability of organs and cost. A different approach for severe emphysema, lung volume reduction surgery (LVRS), has been increasingly utilized during the past several years. In carefully selected emphysematous patients, LVRS improves lung volumes and mechanics, and reduces exertional dyspnoea. Unfortunately, surgical mortality still remains high and some patients show no measurable improvement after surgery. There is an urgent need for data on long-term effects of LVRS; the results of large, randomized trials will soon be forthcoming. The aim of this brief review is to summarize the available knowledge on the effects of LVRS, the criteria for patient selection, short- versus long-term effects and, finally, to propose future directions in this field
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