Study On The Selection Of Subglottic Suction Pressures With Different Secretion Viscosity

Objective:According to the poiseuille’s law of physical and mechanical property, In fluid dynamics the flow resistance is proportional to the liquid viscosity coefficient, the viscous coefficient of liquid will increase when the flow resistance increases, if change the running direction of the liquid, negative pressure will increase when the viscous coefficient of liquid increases. This study draw lessons from sputum viscosity index to explore subglottic suction pressure with different viscosity secretion. To supply safe and effective negative pressure for patients and reference basis for clinical practice of subglottic negative pressure.Contents and methods:these subjects of study are69patients with tracheal intubation or trachea incision who come from ICU in Tianjin third central hospital in July2011to October2012. The study is divided into two parts because of two different ways of suctioning. In July2011to February2012,33cases of patients adopting adopt continuous aspiration subglottic secretion(CASS).Everyday classify patients according to the different viscosity, the same viscosity of secretions are sorted into pressure groups in order of bed number. In March2012to October2012,36cases of patients adopt intermittent subglottic drainage(IASS). As CASS, everyday classify patients into different viscosities, and then randomly sort the same viscosity of patients into different pressure groups. The baseline data (age, gender, disease types and APACHE Ⅱ score) of all patients in the study are collected and compared. Subglottic drainage device can be used in two kinds of way:CASS, maintain a constant negative pressure; IASS, On time cycle-15seconds, Off time cycle-8seconds; subglottic secretion index adapting from sputum viscosity index standard is divided into Ⅰ,Ⅱ and Ⅲ.The group of negative pressure is sorted according to the clinical research literature. CASS has four pressure groups, they are respectively use below20mmHg,20～39mmHg,40～59mmHg and60～80mmHg. IASS has three pressure groups, they are60～89mmHg,89～119mmHg and120～150mmHg. In the same viscosity of secretion under different negative pressure compare the frequency of cough, residue, mucosa injury and change of blood oxygen saturation, heart rate. Finally compare the outcome of two suction ways in the same viscosity of secretion and get the best way and best pressure for subglottic secretion drainage.Results:(1) compare the baseline data of CASS and IASS:the differences of age, sex, disease types, APACHE Ⅱ score have no statistical significance (P>0.05).(2) CASS: all the viscosities of secretion under four negative pressure groups, the differences of residual frequency cough frequency and heart rate changes have obvious statistical significant (P<0.05); The difference between frequency of mucosa injury has statistically significant in Ⅰ,Ⅱ degree secretions (P<0.05); The difference between residual amount between Ⅱ,Ⅲ degree secretions has obvious statistical significance (P<0.05).(3)IASS:the differences of frequency of cough and injury, heart rate changes have obvious statistical significant in I degree secretion (P<0.05); the differences of residue frequency, residual amount, cough frequency have obvious statistical significant in Ⅱ,Ⅲ secretion (P<0.05); the difference of heart rate change also has statistically significant in Ⅲ degree secretion.(4) comparison of CASS and IASS:the differences of cough frequency, blood oxygen saturation and heart rate change have statistically significant in Ⅰ degree secretion (P<0.05);the differences of all the evaluation indexes have obvious statistical significant in Ⅱ secretion (P<0.05);the differences of blood oxygen saturation changes and residual frequency, cough frequency have statistical significant in Ⅲ degree secretion (P<0.05)Conclusion:At present the range of pressure of subglottic suction drainage is wide in the clinical practice,so we study the outcome of different negative pressure in three kind of secretion sand conclude that:(1) CASS:20-39mmHg is good for I degree secretion and40-59mmHg negative pressure for Ⅱ,Ⅲ degree secretions to max the residual amount and min the lesion (2) IASS:60～89mmHg is good for I degree secretion and90～119mmHg negative pressure for Ⅱ,Ⅲ degree secretions to max the residual amount and min the lesion.(3) comparison of CASS and IASS:combined with outcomes of two ways, under20mmHg negative pressure in CASS is good for I degree secretion,40～59mmHg negative pressure in CASS for II degree secretion and90-119mmHg negative pressure in CASS for III degree secretions to max the residual amount and min the lesion.