Volumetric capnography and chronic obstructive pulmonary disease staging
Authors Pablo V Romero, Benigno Rodriguez, Daniela de Oliveira, L Blanch, Federico Manresa
Published 15 October 2007 Volume 2007:2(3) Pages 381—391
Pablo V Romero1, Benigno Rodriguez1, Daniela de Oliveira1, L Blanch2, Federico Manresa1
1Laboratorio de Función Pulmonar, Servicio de Neumologia, Hospital Universitario de Bellvitge, IDIBELL, Hospitalet de Llobregat, Barcelona, Spain; 2Critical Care Center, Hospital de Sabadell, Institut Universitari Fundació Parc Taulí, Sabadell, Spain
Abstract: Spirometry is difficult for some COPD patient to perform. Volumetric capnography could be a second choice test to evaluate the severity of functional disturbances. The aim of this work is to test this hypothesis. A total number of 98 subjects were classified either as normal ex-smokers (N = 14) or COPD patients. The latter were staged following GOLD recommendations. Spirometry and volumetric capnography recordings were obtained from each patient. Spirometry parameters, Bohr Dead Space (VD Bohr), Airways Dead Space from the pre-interface expirate corrected curve (VD aw), Phase III slope (SlIII) and Volume of alveolar ejection (VAE) were measured. Index of Ventilatory Efficiency (IVE), and Index of Airways Heterogeneity (IAH) were calculated as: IVE = VAE/(VT – VD aw) and IAH = 1 – [(VT – VD Bohr)/(VT – VD aw)]. In ANOCOVA analysis IAH showed the greatest association with stage (F > 40), with no significant covariant dependence on VT. A receiver operating characteristics curve analysis showed values of the area under the curve greater than 0.9 for IAH and IVE at all stage levels, with a sensitivity = specificity value greater than 80%. We conclude that IAH and IVE can be used when spirometry cannot be reliably performed, as an alternative test to evaluate the degree of functional involvement in COPD patients.
Keywords: capnography, chronic obstructive pulmonary disease, dead space, pulmonary heterogeneity, receiver operating characteristics curve, spirometry