The Lower Limit of Normal in the evaluation of pulmonary function

Abstract

Pulmonary function tests (PFTs) are widely used in the clinical evaluation of patients with pulmonary and cardiovascular disease. The underlying premise is that lung volumes and air flow through the airways are correlated with measurements of body size and are influenced by age. The result is a set of equations that have lung volume and airway flow as dependent variables of height, age, sex, race and weight and their appropriate coefficients as independent predictors. Higher order exponential relationships are accommodated using logarithms. 1 Quanjer P.H. Stanojevic D. Stocks J. Cole C.G. GAMLSS in Action. 2012http://www.lungfunction.org/gamlss.html Google Scholar The assumption that measurements of body size determine lung size and airway flow is derived form basic biological observations that establish that organ size in mammals scales with the square of the length and that measurements of body size determine metabolic rate, heat losses and the mechanical energy necessary for distribution of oxygen through the tissues. 2 Apell S.P. Wahlsten O. Gawlitza H. Body Mass Index – A Physics Perspective. ArXiv e-prints, 2011: 296 Google Scholar , 3 West G.B. Brown J.H. Enquist B.J. A general model for the origin of allometric scaling laws in biology. Science. 1997; 276: 122-126 Crossref PubMed Scopus (3466) Google Scholar , 4 McMahon T. Size and shape in biology. Science. 1973; 179: 1201-1204 Crossref PubMed Scopus (844) Google Scholar Reference equations that establish expected or predicted values for lung volume and for spirometry based on age and height derived from datasets of healthy individuals are widely used. 5 Pulmonary Function Predicted Values. Johns Hopkins Pulmonary Function Laboratory, Baltimore, Maryland, USA2001http://www.hopkinsmedicine.org/pftlab/pfpred.htm Google Scholar , 6 Quanjer P.H. Stocks J. Cole T.J. Hall G.L. Stanojevic S. Influence of secular trends and sample size on reference equations for lung function tests. Eur Respir J. 2011; 37: 658-664 Crossref PubMed Scopus (134) Google Scholar Pulmonary function impairment in patients with chronic heart failure: Lower limit of normal versus conventional cutoff valuesHeart & Lung: The Journal of Cardiopulmonary and Acute CareVol. 43Issue 4PreviewTo determine the prevalence of pulmonary function abnormalities in patients with chronic heart failure (HF) according to recent American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines using the lower limit of normal (LLN) compared to conventional cutoff values. Full-Text PDF