Impact of pulmonary ventilatory function of patients with stable chronic obstructive pulmonary disease on simultaneous suspended prone position

Abstract

Objective To investigate the impact of pulmonary ventilatory function of patients with stable chronic obstructive pulmonary disease (COPD) on simultaneous suspended prone position. Methods Twelve patients with stable COPD, who visited our clinic between June and October of 2009, were recruited in a series of assessments on a ventilation table using the supine position, suspended prone position, flat prone position and simultaneous suspended prone position in a randomized order, each position lasting 10minutes. Non-invasive NICO cardiopulmonary monitoring system was used for continuous recording of vital signs (heart rate, arterial oxygen saturation, end- tidal pressure of CO2) and respiratory mechanical parameters [respiratory rate, tidal volume, tidal volume of alveolus, physiological dead space(Vd/Vt), peak inspiratory flow (PIF) and peak expiratory flow (PEF)]with each position. The patients were stratified by severity of airway obstruction based on ATS-ERS pulmonary function standards guidelines. Moreover, the changes in pulmonary function (such as tidal volume and respiratory rate) in patients with ventilatory dysfunction were analyzed. Results The four types of patient positioning did not obviously affect heart rate,arterial oxygen saturation and end-tidal pressure of CO2. Respiratory rate in the 4 positions varied following the sequence of simultaneous suspended prone position ＜ supine position ＜ flat prone position ＜ suspended prone position [( 14.8±3.2)/min ＜ ( 17.6±4.5)/min ＜ ( 18.4±3.4)/min ＜ ( 19.5±3.4)/min; all P＜0.05]. Tidal volume and that of alveolus varied following the sequence of simultaneous suspended prone position ＞ supine position ＞ flat prone position ＞ suspended prone position. There were no statistical differences in physiological dead space, PIF and PEF among groups. In 3 severe and 5 extremely severe cases with obstructive ventilatory dysfunction, the tidal volume did not vary significantly among these 4 positions, while the respiratory rate was lowest in simultaneous suspended prone position [(15.3± 1.8)/min in severe cases and (16.6± 1.8)/min in extremely severe cases]as compared to that in suspended prone position [(19.4±3.4)/min in severe cases and (21.4±3.6)/min in extremely severe cases, all P＜0.05]. Conclusions As with other types of prone positioning, simultaneous suspended prone position is safe and stable within the shortterm period, but may reduce respiratory rate and increase the tidal volume significantly. In patients with obstructive ventilatory impairment, simultaneous suspended prone position may have no conspicuous impacts on tidal volume but remain effective in reducing the respiratory rate. Key words: Pulmonary disease, chronic obstructive; Pulmonary ventilation; Posture; Tidal volume; Breathing frequency