Characteristics of tidal expiratory flow pattern in healthy people and patient with chronic obstructive pulmonary disease

According to data reported in literature tidal breathing parameters and especially tidal expiratory flow pattern parameters can be useful in distinguishing airflow obstruction. The purpose of the present study was to investigate the parameters of the tidal breathing in healthy people and patients with chronic obstructive pulmonary disease. The study sample included 158 patients with COPD in clinically stable condition and different degree of functional disturbances (FEV1% pred. = 42% +/- 15%; ATS dyspnea scale = 2.5 +/- 0.9; mean +/- SD). The control group of healthy subjects consisted of 43 men and 37 women. The obtained results show that TPTEF/TE (the time necessary to reach the peak expiratory flow in tidal breathing over the total expiratory time) and VPTEF/VE (the volume necessary to reach the peak expiratory flow in tidal breathing over the total expiratory volume) are an independent aspect of tidal breathing. In healthy people these parameters show weak negative correlation with age and high variability. In COPD they are statistically significantly lower than those of healthy people but, since they are highly variable, they cannot be used for an individual assessment. The increase of the mean inspiratory flow (TV/Tin) and the shortening of VPTEF/VE, TPTEF/TE and Tin/Ttot, are indicative of the lung mechanics changes which have a bearing on dyspnea, too. According to factor analysis the parameters of tidal breathing are four separate dimensions: 1. Breathing frequency and respiratory times; 2. Relationship between the respiratory times; 3. Minute ventilation, mean expiratory flow, mean inspiratory flow and tidal volume; 4. Parameters of the expiratory flow VPTEF/VE and TPTEF/TE. The parameters of forced expiration and those of tidal breathing are separate dimensions of the functional profile of patients with COPD.