| Objective To investigate the viscosity difference of subglottic secretion and airway s Putum based on the quantitative research and rheology experiment; to explore the suction efficiency of subglottic secretion with various viscosity on different suction pressures in vitro; to look into the appropriate suction pressure for intermittent aspiration of thick subglottic secretion, thus provide evidence for the choose of suitable suction pressure in clinical practice.Methods The study was consisted of three parts.PartⅠ:Endotracheal intubation and tracheostomy patients were collected subglottic secretion and airway sputum each of 60 specimens, including watery, thick, gel-like subglottic secretion each of 20 specimens and Ⅰ °, Ⅱ °, Ⅲ ° sputum each of 20 specimens. Samples were analyzed by observing the variations of sputum ingredients including Ca2+, p H value and secretion rheology.Part Ⅱ:63 fresh tracheas(lung saved) of pigs were used to construct the model of subglottic suction. 360 subglottic secretions with different viscosity specimens were collected from 162 patients who has undergone the endotracheal intubation or tracheostomy, 6ml for each specimen. Based on the literature review and pre-experiment,different suction pressures were chosen in line according to the different subglottic secretions viscosity, namely 20 mm Hg to 70 mm Hg for watery secretions, 70 mm Hg to 120 mm Hg for thick secretions and 120 mm Hg to 170 mm Hg for gel-like secretions, with 10 mm Hg difference between groups.Recovery rate and evacuation time of intermittent aspiration subglottic secretions were observed in vitro.Part Ⅲ :This subjects of study were 71 patients with endotracheal intubation or trachea incision whose subglottic secretions were defined as thick.On the basis of ballots patients were sorted into grou P A, B, C, D and E in which correspondingly 80 mm Hg,90 mm Hg, 100 mm Hg, 110 mm Hg and 120 mm Hg.In the same viscosity of secretion under different negative pressure compare 24 h volume of the suctions,residue, evacuation time,the frequency of cough,mucosa injury and the change of vital signs before and 1min,3min,5min after suction.ResultPartⅠ:Compared with Ⅰ °, Ⅱ °, Ⅲ ° airway sputum, watery, thick, gel-like subglottic secretion obtained lower Ca2+ content, higher p H value and shorter secretion flow rate with the most significant statistical effect(P<0.05).Part Ⅱ:In vitro experiments showed:recovery rate of watery secretions reach highest in 60 mm Hg, no statistical significance was found when compared to 40 mm Hg(P>0.05)with the control of suction time less than 20s; recovery rate of thick secretions reach the highest in 120 mm Hg, no statistical significance was found when compared to 110 mm Hg(P>0.05) with the control of suction time less than 30 s, recovery rate of gel-like secretions reach the highest in 160 mm Hg, no statistical significance was found when compared to150 mm Hg(P>0.05) with the control of suction time around 30 s.Part Ⅲ :Thick secretions were used to undertake intermittent suction with five pressure groups, and paired comparisons were made respectively for the suction volumes,residual volumes and evacuation time, there was no statistical significance on the comparison of group D and E(P>0.05),but statistical significance was found on the rest comparisons(P<0.05).For the frequency of cough,there was no statistical significance on the comparison respectively between group A and B, group B and C, group C and D(P>0.05),but statistical significance was found on the rest comparisons(P<0.05).For the paired comparisons of mucosal injury, no statistical significance was found(P>0.05).Different pressure on heart rate, blood pressure, respiration had no statistically significant(P>0.05), the impact of the oxygen saturation in contrast(P<0.05).The changes of vital signs had statistical significance when comparisons were made between before and1 min, 3min and 5min respectively after suction on group D and E(P<0.05).Conclusion1. The viscosity of watery, thick, and gel-like subglottic secretion are all lower than the correspondinglyⅠ°,Ⅱ°,Ⅲ°airway sputum.2. 40 mm Hg,110 mm Hg,160 mm Hg are recommended respectively for watery, thick andgel-like subglottic secretion suction in the model of subglottic suction,thus can achievemaximum recovery with minimum negative pressure.3. 110 mm Hg are recommended for thick subglottic secretions suction to ensure thepatient safety and maximum the suction efficiency for the patients with endotrachealintubation or trachea incision in ICU. |
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