Study On Optimizing Endotracheal Suctioning Of Mechanically Ventilated Neonates With Artificial Airways

Background:Neonatal asphyxia, neonatal pneumonia, neonatal respiratory distress syndrome and infectious diseases are main respiratory diseases for neonatal death. Operating artificial airway for mechanical ventilation is an important treatment for neonatal respiratory distress syndrome and respiratory failure caused by a variety of respiratory diseases.A patient with respiratory insufficiency may not be able to maintain spontaneous respiration and may require an artificial airway. Since artificial airway changes the structure of the original airway, and warm and wet effect of upper respiratory tract are damaged, sputum tends to accumulate in the bottom of the endotracheal tube. Endotracheal suction is implemented as a way to remove the secretions,to maintain a patent airway and to prevent complications of secretion retention such as ventilator-associated pneumonia. Normal saline instillation is always utilized by nurses during endotracheal suction as a traditional nursing method. But the efficacy and safety of saline instillation have been doubted since 1970's.According to Roberts FE's delphy study on the use of normal saline instillation prior to endotracheal suction in the UK, NSI would be appropriate to use on situations as following:when sputum retention due to thick or tenacious secretions is affecting.or is likely to affect,ventilatory status and "available treatment techniques" are not clearing the secretions; when atelectasis due to mucous plugging occurs and "available techniques" are unable to clear it; and when ETT/tracheostomy obstrucion or partial obstruction due to sputum occurs.In fact, saline instillation was delivered under different dose and concentrations of saline solution, which is from 0.5 to 1 ml or from 0.45% to 0.9%.Traditional endotracheal suctioning requires infusion of saline into artificial airway prior to suctioning. This method may sound feasible, but it merely centers on clinical knowledge and practical experience, and has no adequate scientific evidence to support.Moreover, airway of the newborn is relatively narrow, and the cough reflex has not yet been mature. Positive pressure mechanical ventilation can lead to mucociliary impairment, at the same time, tracheal intubation may weaken and deprive function of the epiglottis, giving rise to retention of airway secretions. Therefore, it is necessary to strengthen respiratory tract care during mechanical ventilation.Open endotracheal suctioning is a double-edged sword in the process of neonatal mechanical ventilation. On one hand, it is an important nursing intervention to clear respiratory secretions so as to maintain airway unobstructed; on the other hand, it can cause alveolar collapse and oxygenation obstacles.In recent years, more and more studies focused on effects of endotracheal suction of lung recruitment on respiratory function. Among the methods of lung recruitment, controlling lung inflation and prolonged sigh are commonly used in clinic.Clinical scholars have ever used simple ventilator to operate lung recruitment after suctioning. This treatment may have the following weak points:the lung pressure cannot be monitored; management cannot be quantified; the effect is not stable and influenced by many factors such as experience of operators. Thus, it is imperative to find a safe and effective approach that can be quantified to operate lung recruitment suction.However, open airway suction may cause changes of respiratory function including decreased intra-airway pressure and lung volume, bronchoconstriction, increased respiratory resistance, decreased lung compliance and arterial partial pressure of oxygen and increased partial pressure of carbon dioxide. Lung recruitment maneuver has been the research hot point for its effect of improving hypoxemia. The reasons are as follows. High airway pressure may recruit more collapsed pulmonary alveolus, increase the number of pulmonary alveolus with the function of gas exchange and effective lung volume, improve gas distribution and reduce the pulmonary shunt and, thus improving ventilation/perfusion ratio; High airway pressure lasting a certain period of time contributes to gradually opening up of pulmonary alveolus in different time points, and extend the time period of gas exchange and, thus improving oxygenation. Operation strategies and effect evaluation relevant to lung recruitment suction are still to be further studied.The study is composed of the following two parts to optimize endotracheal suctioning of mechanically ventilated neonates with artificial airways,effects of saline instillation on the sputum andcardiopulmonary functions in neonates with mechanical ventilation and effects of endotracheal suction of lung recruitment on hemodynamics and respiratory mechanics in canine model of ARDS.Objectives:1. During the procedure of open suction in neonates with mechanical ventilation, we dripped different concentrations and doses of sodium chloride solution into the airway, then analyzed indicators of cardiopulmonary function including amount of sputum excretion, peripheral oxygen saturation, airway peak pressure, heart rate, systolic and diastolic blood pressure, etc, in different time points before and after suction, so as to explore safety and efficacy of wet fluid infusion into airway before suction in neonates with mechanical ventilation, and provide basis for clinical and basic research.2. By means of animal experiments of canine model of ARDS, we explored the effects of different methods of lung recruitment suction on hemodynamics and respiratory mechanics, to provide basis for clinical nursing care in respect to airway care in lung recruitment suction for neonates with mechanical ventilation Methods:Part 1:effects of saline instillation on the sputum andcardiopulmonary functions in neonates with mechanical ventilation1.Participants were recruited from neonates with mechanical ventilation in the paediatric ICU of the Third Affiliated Hospital of Guangzhou Medical College.2. The order of saline instillantion using different dose and concentrations of of saline solutions were randomly assigned.3.The timing of sucion was defined by respiratoy assessment.4.Patients were preoxygenated at 100% oxygen for 1 minute before suction.5. According to the order of the experimental design, the following five kinds of saline instillation were implemented in the neonates before endotracheal suction under different dose and concentrations of of saline solutions:①no saline was used;②0.9% NaCl solution,0.5ml;③0.9% NaCl solution, 1ml;④0.45% NaCl solution,0.5ml;⑤0.45% NaCl solution, 1ml.6. Cardiopulmonary parameters were recorded, including SpO2, PIP, HR, SBP and DBP.7..Aspirations were performed at a negative pressure of 80～100mmHg for less than 10 seconds during which the catheter was gently rotated and withdrawn.8. Patients were post-oxygenated at 100% oxygen for 1 minute and then the FiO2 was adusted to baseline.9. Sputum and cardiopulmonary parameters were recorded in 1 minute,2 minutes and,10 minutes after suctioning, including SpO2, PIP, HR, SBP and DBP.Part 2:effects of endotracheal suction of lung recruitment on hemodynamics and respiratory mechanics in canine model of ARDS.1. Exogenous canine model of ARDS was established.2. Open endotracheal suctioning was implemented in the canine model of ARDS with mechanical ventilation.3. According to the order of the experimental design, the following six kinds of lung recruitment were implemented in the canine model of ARDS after open endotracheal suctioning according to different mechanical ventilation methods and different FiO2(fractional concentration of inspired oxygen).①Lung recruitment was not implemented after suctioning, and FiO2 remained unchanged.②Lung recruitment was not implemented after suctioning, and FiO2 changed from 60% to 100% for 2 minutes.③Extended sigh recruitment was given after suctioning with no change in FiO2, e.g. increasing PEEP from 10 cmH2O to 15 cmH2O after suctioning,2 breaths later, decreasing VT from 10 ml/kg to 8 ml/kg for 30 seconds of ventilation; then increasing PEEP by 5 cmH2O after each 30 seconds of ventilation, and decreasing VT by 2ml/kg after each 2 breaths; finally, PEEP increasing to 30 cmH2O, and VT decreasing to 50 ml,60 seconds of ventilation later, adjusting PEEP to 10 cmH20 and VT to 10 ml/k.④Extended sigh recruitment was given after suctioning with FiO2 changing to 100%,e.g. increasing PEEP from 10 cmH20 to 15 cmH2O after suctioning,2 breaths later, decreasing VT from 10 ml/kg to 8 ml/kg for 30 seconds of ventilation; then increasing PEEP by 5 cmH2O after each 30 seconds of ventilation, and decreasing VT by 2ml/kg after each 2 breaths; finally, PEEP increasing to 30 cmH2O, and VT decreasing to 50 ml,60 seconds of ventilation later, adjusting PEEP to 10 cmH2O and VT to 10 ml/k.⑤Sustained inflation was implemented with FiO2 unchanged, e.g. increasing PEEP from 10 cmH20 to 30 cmH2O after suctioning,2 breaths later, decreasing VT from 10 ml/kg to 50 ml for 120 seconds of ventilation; then adjusting PEEP to 10 cmH20 and VT to 10 ml/k.⑥Sustained inflation was implemented and FiO2 was increased to 100%, e.g. increasing FiO2 to 100% and PEEP from 10 cmH2O to 30 cmH20 after suctioning,2 breaths later, decreasing VT from 10 ml/kg to 50 ml for 120 seconds of ventilation; then adjusting PEEP to 10 cmH20 and VT to 10 ml/k. The interval of two kinds of lung recruitment suction methods is 60 minutes to ensure hemodynamic parameters and indices of respiratory mechanics to return to baseline levels.4. Hemodynamic parameters were observed in 1 minute before suctioning,1 minute,3 minutes,8 minutes,15 minutes and,30 minutes after suctioning, including heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), pulmonary artery pressure (PAP), pulmonary artery wedge pressure (PAWP) and cardiac output (CO), peak airway pressure (PIP), plateau pressure (Pplat) and tidal volume (VT) were read from the ventilator, to calculate pulmonary static compliance (Cst) and other indices of respiratory mechanics.Results:Part 1:effects of saline instillation on the sputum andcardiopulmonary functions in neonates with mechanical ventilation1. The 0.5 ml saline instillation group has more sputum than no saline instillation group, F (P) value was 4.269(0.017).There was no effect of different dose and concentration of saline instillation on sputum of the neonates.2. Cardiopulmonary parameters such as SpO2, HR and SBP changed over time;the F (P) values were 41.567(0.000),39.688(0.000),6.715(0.000), respectively. SpO2 in the points of 2 minute and 10 minute after suctioning were higer than that in the points of saline instillation and 1 minute after sucion.HR in the points of 1 minute and 2 minute after suctioning were higer than that in the point of saline instillation. There was no effect of dose and concentration of saline instillation on the cardiopulmonary parameters; the F (P) values were 0.664(0.725),0.510(0.821), 6.715(0.588), respectively.3. Cardiopulmonary parameters such as PIP and DBP did not change over time; the F (P) values were 2.440(0.077),1.121(0.341), respectively.Part 2:effects of endotracheal suction of lung recruitment on hemodynamics and respiratory mechanics in canine model of ARDS.1.8 healthy hybrid dogs were successfully made into canine model of ARDS by intravenous injection of oleic acid.2. Hemodynamic indexes such as HR, MAP, CVP, PAP, PAWP, and CO changed over time and returned to the level before suctioning within 30 minutes after suctioning; the F (P) values were 44.554 (0.000),69.551 (0.000),52.192 (0.000), 73.222 (0.000),73.564 (0.000) and 8.313 (0.000), respectively. Hemodynamic parameters in the 1 minute after suctioning (T2 time point) and 3 minutes after suctioning (T3 point) were higher than the other time points. PAWP in controlled lung expansion suction (method 5 and 6) was higher than simple open suction, and the F (P) value of 3.849 (0.006).3. PIP, Pplat and Cst and other respiratory mechanics changed over time, and returned to the level before suctioning within 30 minutes after suctioning; the F (P) values were 250.928 (0.000),167.550 (0.000), and 78.921 (0.000). The changes of respiratory mechanics over time were relevant to different of lung recruitment suction methods; the F (P) values of PIP, Pplat and Cst were 30.334 (0.000),20.286 (0.000) and 12.032 (0.000). While in the open suction method with no lung recruitment implemented, PIP and Pplat increased and Cst decreased, in the open suction method with lung recruitment implemented, PIP and Pplat decreased and Cst increased.1 minute after suctioning, lung recruitment suction with extended sigh improved lung ventilation better than lung recruitment suction with continued aeration.Conclusion:The study on optimizing endotracheal suctioning of mechanically ventilated neonates with artificial airways is composed the following two parts, the usage of saline instillation and lung recruitment maneuver during endotracheal suctioning. 0.5ml saline instillation mqy be tried in clinical when sputum retention due to thick or tenacious secretions and "available treatment techniques" are not clearing the secretions. When the tracheal is "cleaned", the implementation of lung recruitment suction with extended sigh in the canine model of ARDS with mechanical ventilation may lead to slight changes in hemodynamics, but the duration time lasts no longer than 30 minutes, suggesting it is a relatively safe nursing intervention. And it may decrease the PIP and Pplat, increase the Cst. We believe that the study may apply the evidence and support for the further clinical research on scientic endotracheal suctioning of mechanically ventilated neonates with artificial airways.