Evaluation of Cough Assist on the Differences of Rheological Property and Lung Mechanics

Abstract

Background: We compared and studied the movement distance of mucus simulants (MS) with different viscoelasticity with different lung mechanics, driving pressure, ventilation mode and presence or absence of PEEP using by the cough assist function of VOCSN ventilator. Methods: We measured the movement distance of the MS under the following conditions. 1) Four types of lung mechanics: compliance (Cst) 50mL/cm H₂O and airway resistance (Raw) 5cm H₂O/L/s in normal lung, restrictive lung (Cst30 and Raw 5), obstructive lung (Cst50 and Raw 20) and mixed lung(Cst30 and Raw 20). 2) 3 types of insufflation and exsufflation driving pressure were 30/-30, 40/-40 and 50/-50 cm H₂O. 3) 2 types of ventilation mode were VCV A/C and PCV A/C. 4) PEEP was 0 or 5 cm H₂O. Under the above conditions, the movement distance was measured using two types of MS. A 1% lysis of MS is potage-like, corresponding to the secretion of chronic bronchitis, and a 4% lysis MS is jelly-like, close to the viscoelasticity of a mucus plug during an asthmatic attack. The analysis of the ventilatory dynamics was measured 5 times under each condition using flow analyzer PF300, and the average value was compared. Data analysis used software SPSS version 17 and JMP version 12 and P values < .05 were considered statistically significant. This research is conducted after obtaining approval from Showa University Ethics Review Board. Results: With regard to the viscoelastic properties of MS, the movement distance was larger for 1% MS than for 4% MS (P < .05). In addition, as the cough assist drive pressure increased, the movement distance of the MS increased (P < .05). With regard to the difference in lung mechanics, there was almost no difference in the movement distance of the MS regarding the difference in compliance, but the movement distance of the MS became smaller as the airway resistance became higher (P < .05). As for the ventilation mode, the movement distance of the MS tended to be larger in PCV A/C than in VCV A/C. The migration distance of PEEP with 5 cm H₂O added was larger (P < .05). Conclusions: From these results, the effective setting method sets PEEP and the high driving pressure for restrictive lung. PCV mode and high driving pressure appeared to be more effective in cases of obstructive lung and high viscoelasticity secretions. In the future, further comparisons under different setting conditions are needed.