A non invasive estimate of dead space ventilation from exercise measurements

PLoS One. 2014 Jan 30;9(1):e87395. doi: 10.1371/journal.pone.0087395. eCollection 2014.

Abstract

Rationale: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon Dioxide / metabolism
  • Exercise / physiology*
  • Exercise Test / methods
  • Female
  • Healthy Volunteers
  • Heart Failure / physiopathology
  • Humans
  • Male
  • Middle Aged
  • Pulmonary Gas Exchange / physiology*
  • Respiration
  • Ventilation / methods

Substances

  • Carbon Dioxide

Grant support

Dr. Paola Gargiulo was supported by an educational grant of Italian Society of Cardiology (SIC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.