PH Quanjer

Lung volumes are subdivided into static and dynamic lung volumes. Static lung volumes are measured by methods which are based on the completeness of respiratory manoeuvres, so that the velocity of the manoeuvres should be adjusted accordingly. The measurements taken during fast breathing movements are described as dynamic lung volumes and as forced inspiratory and expiratory flows. ### 1.1 Static lung volumes and capacities The volume of gas in the lung and intrathoracic airways is determined by the properties of lung parenchyma and surrounding organs and tissues, surface tension, the force exerted by respiratory muscles, by lung reflexes and by the properties of airways. The gas volumes of thorax and lung are the same except in the case of a pneumothorax. If two or more subdivisions of the total lung capacity are taken together, the sum of the constituent volumes is described as a lung capacity. Lung volumes and capacities are described in more detail in § 2. #### 1.1.1 Determinants Factors which determine the size of the normal lung include stature, age, sex, body mass, posture, habitus, ethnic group, reflex factors and daily activity pattern. The level of maximal inspiration (total lung capacity, TLC) is influenced by the force developed by the inspiratory muscles (disorders include e.g. muscular dystrophy), the elastic recoil of the lung (disorders include e.g. pulmonary fibrosis and emphysema) and the elastic properties of the thorax and adjacent structures (disorders include e.g. ankylosis of joints). The level of maximal expiration (residual volume, RV) is determined by the force exerted by respiratory muscles (disorders include e.g. muscle paralysis), obstruction, occlusion and compression of small airways (disorders include e.g. emphysema) and by the mechanical properties of lung and thorax (disorders include diffuse fibrosis, kyphoscoliosis). Assessing the total lung capacity is indispensable in establishing a restrictive ventilatory defect or in diagnosing abnormal lung distensibility, as may occur in patients …

Review

Reference values play an important role in establish-ing whether, in an individual, measured volumes fall within a range to be expected for a healthy person of the same sex, similar stature, age, and other characteristics. Hence, reference values should be chosen that are appro-priate to the person being investigated. Ideally, the refe-rence values should be consistent; in the context of this paper, it implies that predictions for the various lung vol-umes have been derived from the same reference popu-lation, with the same techniques. Comparing measured with reference values is fraught with difficulties, as it may lead to disease going undetected. This is because the scatter in predicted values is sufficiently large to allow a sick person to lose, e.g. much of his total lung capacity (TLC), whilst still remaining in the range observed

Interstitial lung diseases (ILDs) are a set of heterogeneous lung diseases characterised by inflammation and, in some cases, fibrosis. These lung conditions lead to dyspnoea, cough, abnormalities in gas exchange, restrictive physiology (characterised by decreased lung volumes), hypoxaemia and, if progressive, respiratory failure. In some cases, ILDs can be caused by systemic diseases or environmental exposures. The ability to treat or cure these ILDs varies based on the subtype and in many cases lung transplantation remains the only curative therapy. There is a growing body of evidence that both common and rare genetic variants contribute to the development and clinical manifestation of many of the ILDs. Here, we review the current understanding of genetic risk and ILD.

The use of peak flow meters has been widely adopt-ed for monitoring patients with asthma. The Working Party of the European Respiratory Society (ERS) has solely addressed technical and physiological issues rel-ating to peak expiratory flow (PEF) (flow describes the rate of change of volume (volume rate), so that flow rate is equivalent to volume acceleration. Hence, PEF should be used in preference to peak expiratory flow rate (PEFR)). Monitoring schemes, or comparison of PEF with other indices, such as the forced expiratory volume in one second (FEV1), do not form part of these recommendations. Measurements of PEF are of value in identifying air-flow limitation. The correlation between airflow and symptoms is variable, some patients being poor per-