Application Effect Analysis of Three Methods of Heating and Humidication for Weaning Patients in ICU

Objectives To investigate the effects of articial nose, Venturi device+thermostatic humidication T-tube, Venturi device+thermostatic humidication T-tube+PEEP valve in patients with tracheotomy in ICU. Design: Cohort study. Setting: Tertiary academic medical center. Patients: A total of 215 patients were engaged in this study. Clinical and laboratory examination data were used to determine the heating and humidication eciency of 3 different methods. Methods: We conducted randomized controlled trial. Patients who successfully weaned from mechanical ventilation were enrolled, and every patient was randomized to receive one of the above three interventions. Three groups of patients were compared in terms of vital signs, the effect of articial airway heating and humidication, and blood gas indicators. Basic patient data (age, gender, mechanical ventilation duration, ICU stay, disease type) were recorded. Vital signs include heart rate, blood pressure, respiratory rate, oxygen saturation; The effect of heating and humidifying the articial airway were dened as the number of sputum suction and coughing within 24 hours, sputum characteristics, whether there is bloody sputum formation, whether there is phlegm callus formation; Blood gas indicators include pH, oxygen partial pressure, carbon dioxide partial pressure, lactic acid, residual base, and bicarbonate. Results: In terms of the heating and humidication effect of patients in ICU, the heating and humidication effect of the Venturi device+T-tube method and the Venturi device+the T-tube +PEEP valve method were signicantly superior to those of articial nasal method (sputum suction number: P =0.0001; sputum scab: P =0.03; Number of cough: P =0.007). SpO 2 was signicantly higher (P =0.004) in the Venturi device+T tube+PEEP valve than that in the Venturi device+T tube. Conclusion: Compared with the articial nose method, the T-piece+venturi device and thermostatic heating and humidifying T-tube +PEEP valve method is better. In terms of improving oxygenation, the Venturi device and the thermostatic humidication T tube +PEEP valve could improve the patient's oxygen sum more than the Venturi device and the thermostatic humidication T tube.


Introduction
For patients weaning from mechanical ventilation, airway management is the key to keep the airway open and prevent pulmonary infection. After the establishment of the arti cial airway, the upper airway loses its function of warming and humidifying the inhaled air during inhalation, resulting in increased water loss of the lower respiratory tract, mucosal drying, secretion drying and phlegm excretion obstruction, etc. Heating and humidi cation can make the cilia of the tube wall move actively and push up the mucus attached to the cilia continuously, which is conducive to discharge. Therefore, it is very important to humidify the airway of patients while weaning. 1 2 According to the "2012 Guidelines of American College of Respiratory Therapy for Airway Humidi cation" 2 , the air inhaled through arti cial airways must be at the normal temperature (37˚C) in order to ensure the normal movement of mucosal cilia. It is suggested that long-term oxygen treatment is needed (100% relative humidity, absolute humidity (44 mg/L). It was also recommended that oxygen humidi er should be used in patients with poor secretion discharge. 3 Arti cial nose is routinely used to prevent airway exposure in patients undergoing tracheotomy after weaning. However, its heating and humidifying effect is not ideal, and it is easy to be blocked by sputum. 4 Recent years other humidifying methods were used by physicians. Corley et al. used nasal cannulation for high-ow oxygen therapy and t-tube for low-ow tracheotomy for oxygen therapy. 5,6 Hypermobile oxygen therapy improves oxygen balance by providing an exogenous positive pressure. Clinical researchers have also used respiratory humidi cation therapy devices with active humidi ers and heating pipes, venturi mass ow humidi cation oxygen therapy devices to treat patients undergoing tracheotomy. In recent clinical studies, the application of respiratory humidi cation therapy in tracheotomy is limited 7 . Venturi humidi cation oxygen therapy system regulates gas ow oxygen ow and oxygen concentration by regulating gas ow standard Venturi air oxygen mixer. However, the precise mechanism and its operation are still controversial 8 .
The purpose of this paper is to explore the application effects of three heating and humidi cation methods for weaning patients in ICU: arti cial nose method, Venturi device and thermostatic heating and humidi cation + T-tube method, Venturi device and thermostatic heating and humidi cation T-tube +PEEP valve method.

Ethical
The study was conducted in the intensive care unit and the study agreement was approved by the local ethics committee. Informed consent is obtained from each patient or relative. Arti cial nose method: Oxygen is the humidifying bottle of central oxygen supply and bubble owmeter. The oxygen tube is connected to the arti cial nose, and the arti cial nose is connected to the arti cial airway.
Venturi device and T-tube method: the central oxygen supply device is connected with the bubble owmeter humidi cation bottle, Venturi device, electric thermostatic steam generator (humidi cation tank), disposable threaded pipeline (with heating guide wire inside), T-tube, connected in accordance with the ventilation sequence. One end of the T-tube is connected to the patient's arti cial airway. The humidifying liquid in the humidifying tank is used for sterilizing injection. The schematic model was shown in Fig.1.
The Venturi device + the T-tube +PEEP valve method: the central oxygen supply device is connected with the bubble owmeter humidi cation bottle, the Venturi device, the Venturi device, the electric thermostatic steam generator (the humidi cation tank), the disposable threaded pipeline (with heating guide wire inside the pipeline), the T-tube, which are connected in accordance with the ventilation sequence. One end of the T-tube is connected to the opening of the patient's arti cial airway. Connect the other end of the T tube to the PEEP valve. The humidifying liquid in the humidifying tank is water for sterilizing injection. As shown in Fig.2.

Determination of sputum viscosity and humidi cation effect
Nurses were trained in the management of tracheotomy in the ICU, including oral hygiene. The suction program is based on current knowledge. The catheter is gently inserted into the endotracheal tube for a maximum of 15 cm or until resistance is detected; The time limit of dural suction procedure was & LT;For 15 seconds. When secretions are present, suction is performed as required according to clinical conditions. Sputum viscosity was measured by trained nurses. The sputum viscosity is divided into three grades: rst grade: dilute or foam like soup; no sputum remains on the inner wall of the pipe; second grade: medium adhesion; lower sputum suction; a small amount of sputum remains on the inner wall of the pipe, but it can be easily removed by ushing with water. Level III: Viscous and yellow, large amounts of adhesive remain on the inner wall of the straw, rather than being easily removed by washing with water. 6 Formation of phlegm scab: to observe whether the patient cough or phlegm scab when cough or suction, or the patients manifested as a rapid breathing, blood oxygen saturation or restlessness.
1.3.2 Comparison of arterial blood gas indexes after 2h and airway heating and humidi cation effects within 24h by the three methods. Blood gas extraction was performed for 2h after inclusion. The nurse applied pressure to the artery in the patient's wrist for a few seconds before performing an arterial blood gas test. The program, called the Modi ed Allen test, evaluates whether blood ow to the hand is normal. Once an artery is found, a needle is inserted into the artery and blood is drawn. When obtaining a sample, take care to eliminate visible bubbles, as these bubbles can dissolve into the sample and cause inaccurate results. Sealed, the syringe is brought to the blood gas analyzer for analysis within 30 minutes.

Statistical Methods
SPSS 22.0 statistical software was used. The count data were presented by case number and per cent. Chi-square test and analysis of variance were performed, with P < 0.05 was considered statistically signi cant.

Results
Of the 215 patients screened, 180 cases were included. 6 cases were excluded for age lower than 18 years, 4 cases were excluded for pregnancy, and 25 were excluded for mechanical ventilation time less than 48 hours. Finally, 180 patients (84%) were included for further analyzation.
The baseline statistics of patients are shown in Table 1, and no signi cant difference was found between the 3 groups.
We rst compared the vital signs of patients treated with different methods. As shown in Table 2, there was no signi cant difference in the vital signs.
We further analyzed the humidi cation effect of 3 humidifying ways (de ned as the sputum suction frequency (times/hour), sputum scab and cough times), and we found that the venturi device+ T-tube method, the Venturi device + T-tube +PEEP valve method were signi cantly superior than the arti cial nasal method (Number of sputum aspiration: P =0.0001; Sputum callus: P =0.03; Number of cough: P =0.007).
The blood gas indexes were also analyzed. As shown in Table 2. We found SpO 2 of patients treated with venturi device+T tube +PEEP valve were signi cantly improved compared with that of patients treated with the Venturi device+T tube (P =0.004). There was no signi cant difference in other indexes. Table 3, our data showed that the humidifying effect (de ned as sputum viscosity) of venturi device +T tube method and venturi device + T tube + PEEP valve method was superior to that of arti cial nose method (P < 0.001).

Discussion
When the patient weaned from mechanical ventilation, it is not only disuse of the nasal cavity, secondary infection, and nasal mucosal ciliary dysfunction, but more importantly, inhaled gas is all warmed and humidi ed by the trachea and the respiratory tract below, which is di cult to achieve the desired effect, and the loss of exhaled air and water is signi cantly increased. 9 Therefore, for patients with arti cial airways, the humidi cation process of inhaled gas should be accompanied by heating and tempering. No matter what kind of humidi cation, the gas temperature in the proximal airway should reach 37℃ and the relative humidity should reach 100%.It is an important nursing measure to ensure the effect of airway humidi cation and temperature.
The Venturi device uses the negative pressure generated by the oxygen jet to bring a certain amount of air from the side hole 10 , in order to dilute the oxygen to achieve the required inhalation oxygen concentration, so as to achieve the purpose of controlled oxygen therapy. Its advantage is that the air oxygen mixture has a large ow rate and a fast ow rate. Theoretically, the upper oxygen mixture ow rate can reach 45L/min, which can better meet the patient's inspiratory ow rate, reduce repeated breathing, and thus prevent CO2 retention. Venturi devices can precisely control oxygen concentration, especially in patients with chronic obstructive pulmonary disease. Combining the venturis with the heating and humidifying device and T tube can better approach to human physiological conditions, so as to achieve the optimal heating and humidifying.
In terms of the heating and humidifying effect, the Venturi device and the thermostatic heating and humidifying T tube +PEEP valve were obviously superior to the traditional arti cial nasal method, as shown in Table 2 and 3: The number of sputum suction (times/hour), sputum scab and cough were all less than that of the arti cial nasal method. Sputum viscosity is arti cial nose method degree of phlegm accounted for more than (46.7%).This is due to the arti cial nasal method, for patients to use their own exhaled gas to actively heat and humidify, and more prone to sputum obstruction, resulting in frequent replacement. The Venturi device and the thermostatic heating and humidi cation +T tube method, the Venturi device and the thermostatic heating and humidi cation T tube +PEEP valve method can not only make use of the precise oxygen concentration of Venturi, but also passively heat and humidify, which is more effective and closer to the physiological needs of patients, and can be widely used in clinical practice.
For example, in patients with poor performance of PEEP, the PEEP valve can be connected to the end of the T tube, so as to give the patient an exogenous PEEP to improve the patient's dead cavity, thereby improving the risk of oxygen and carbon dioxide retention, which is a great deal. As shown in Table 2, SPO2 was signi cantly higher in the Venturi device and the thermostatically heated humidifying T tube +PEEP valve than in the Venturi device and the thermostatically heated humidifying T tube.
In addition, the connection between Venturi and the humidi cation device is simple, convenient, easy to grasp, and does not increase the workload of nurses, nor is it as frequent as the replacement of arti cial nose, which reduces the pain and economic burden of patients.
It is also interesting to note that the venturi device and the thermostatically heated humidifying T-tube, and the Venturi device and the thermostatically heated humidifying T-tube +PEEP valve have less lactic acid (LAC) than the arti cial nose method. We speculate that the reason is that the venturi device and the thermostatic heating and humidifying T-tube method, and the Venturi device and the thermostatic heating and humidifying T-tube +PEEP valve method have more arti cial nasal method for patients with neurological diseases, such patients have strong central driving force, and respiratory excitement leads to the decrease of lactic acid.
However, this study is not without limitations. The study did not consider the effect of different diseases on the results. For example, patients with neurological and non-neurological diseases. In addition, latency, nutritional status (such as albumin), immunosuppressive status (such as diabetes), and antibiotic use are all taken into account and should be observed in further studies.

Conclusion
To sum up, due to the clinical situation, a large number of patients need long-term indweling tracheotomy catheter for oxygen therapy. It is particularly important for patients to humidify the respiratory airway by heating. In this study, three methods of heating and humidifying oxygen therapy were compared, and the e cacy of heating and humidifying oxygen therapy in patients undergoing tracheotomy was compared. The conclusion is as follows: compared with the traditional arti cial nose method, the humidi cation effect of venturi device and thermostatic heating humidi cation T-tube method, venturi device and thermostatic heating humidi cation T-tube +PEEP valve method is better. In addition, compared with the Venturi device and the thermostatic humidifying T tube +PEEP valve, the Venturi device and the thermostatic humidifying T tube +PEEP valve can better improve the patient's oxygen and do not cause carbon dioxide retention. More patient populations will need to be studied in the future to observe the effects of the three methods of heating and wetting in patients with different diseases.

Declarations
Ethical Approval and Consent to participate Ethical Approval is not applicable.
All datasets analyzed during the study are available from the corresponding author on reasonable request.

Contributions
ZJZ designed the study and is accountable for all aspects of the work. JYB and XQZ performed the statistical analyses, interpreted the results. YXW compiled the manuscript, interpreted the results and provided critical revisions for the manuscript. CY and YG performed statistical analyses and provided critical revisions for the manuscript. CY, YG, SYJ, QW and MMT performed the experiments.