Tidal breathing at all ages.

Measurement of lung function during tidal breathing may be performed regardless of the age and respiratory state of the patient. This is particularly advantageous in young children in whom forced respiratory manoeuvres cannot be performed, but has also been found useful in adults with various chest diseases. The most frequently reported tidal breathing parameters are mathematical expressions of the shape of the tidal flow/volume (TFV) loop or tidal flow/time traces, as the ratio of the time or volume taken to reach peak expiratory flow to total expiratory time or volume (tPTEF/tE or VPTEF/VE, respectively). However, new parameters have been suggested, focusing on the shape of the latter portion of the curve. Standardization of measurements is important, and more studies are required to settle some of the issues regarding, for instance, how many curves to evaluate, which parameter to report and how to perform challenge or reversibility tests. Intra-individual variation should be kept to a minimum, preferably performing measurements under the same conditions on each occasion. The issue of whether to sedate is a subject of debate. However, with experience, reproducible TFV measurements may be obtained in most subjects in the awake state, regardless of age, provided the setting is friendly and calm. TFV measurements have provided important information in research as well as clinical settings. Reduced tPTEF/tE has been demonstrated in newborn term and premature babies born to smoking mothers, and is a risk factor for recurrent wheeze within the first 3 yrs of life. Also, tPTEF/tE is clearly reduced in subjects with acute bronchial obstruction (BO) (such as occur in bronchiolitis), but also in asymptomatic children with BO for other reasons, such as asthma. Significant response to histamine and methacholine as well as to bronchodilator has been demonstrated in preschool children, adults and animals (horses, dogs and cats). The present paper discusses various practical issues concerning and possible uses of tidal flow/volume measurements. In conclusion, tidal flow/volume measurements may be important supplementary tools in the investigation of respiratory disease in both research and clinical work in subjects who for any reason cannot cooperate with more conventional lung function measurements.