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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 33  |  Issue : 2  |  Page : 74-80

T-tube ventilation should be rationalized in pediatric intensive care unit: a comparative study between T-tube and pressure support ventilation during spontaneous breathing trial


1 Department of Pediatrics, Zagazig University, Zagazig, Egypt
2 Department of Anesthesia, Zagazig University, Zagazig, Egypt
3 Department of Chest Diseases, Zagazig University, Zagazig, Egypt

Date of Submission08-Apr-2020
Date of Acceptance21-Aug-2020
Date of Web Publication5-Oct-2020

Correspondence Address:
Dalia A Abdelrahman
Department of Pediatrics, Faculty of Medicine, Zagazig University, Zagazig, 11865
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/AJOP.AJOP_21_20

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  Abstract 


Background Shifting from mechanical ventilation to spontaneous breathing during weaning phase is very critically challenging, and its success depends on many factors including the adopted weaning strategy in each center. Few studies have compared the used weaning procedures in pediatric age groups and their effect on the vital signs as stress predictors during spontaneous breathing trial (SBT).
Aim The aim was to compare between t-piece weaning tool and pressure support ventilation (PSV) during SBT in mechanically ventilated pediatric patients to assess patients’ suffering.
Patients and methods This prospective cohort study was carried out in the pediatric chest and anesthesia ICUs, Zagazig University Hospitals, Egypt, over a 6-month period (from May to October 2018). A total of 104 ventilated patients aged from 2 months to 18 years were enrolled in this study. All patients were subjected to full clinical assessment, as well as comparative methods between PSV and T-tube (TT) ventilation during weaning process.
Results It was found that cardiac arrhythmias accounted for 71.2% of the patients weaned on TT in the form of sinus tachycardia compared with 9.6% of the patients on PSV, with significant difference between the two groups (P<0.001). Moreover, there was a significance increase in the mean arterial blood pressure among patients on TT during weaning process, with increase in the work of breathing (P<0.001). PSV mode had significantly lower PCO2 than TT during weaning (P<0.001). The failure rate was higher when using TT during SBT in comparison with PSV, with more exposure to another weaning trials.
Conclusion The authors concluded that PSV has less stressful effects on patients during SBT process. TT weaning procedure has higher failure rate than PSV.

Keywords: mechanical ventilation, pressure support ventilation, SBT, T-tube


How to cite this article:
Abdelrahman DA, Tawfik AM, Walaa M, Abbas A. T-tube ventilation should be rationalized in pediatric intensive care unit: a comparative study between T-tube and pressure support ventilation during spontaneous breathing trial. Alex J Pediatr 2020;33:74-80

How to cite this URL:
Abdelrahman DA, Tawfik AM, Walaa M, Abbas A. T-tube ventilation should be rationalized in pediatric intensive care unit: a comparative study between T-tube and pressure support ventilation during spontaneous breathing trial. Alex J Pediatr [serial online] 2020 [cited 2020 Oct 20];33:74-80. Available from: http://www.ajp.eg.net/text.asp?2020/33/2/74/297242




  Introduction Top


Mechanical ventilation (MV) is considered as an integral treatment option in the ICU. Its primary objective is to decrease the work of breathing (WOB) and to reverse the life-threatening hypoxemia or hypercarbia.

Weaning off MV was described as ‘the shift from ventilation assistance to complete spontaneous respiration while preserving an efficient exchange of gas.’ It accounts for ∼40% of the complete length of MV in children on average since the start of spontaneous breathing trial (SBT) [1].

Pressure support ventilation (PSV) is a pressure-targeted, flow-cycled ventilation mode in which each breath needs to be triggered by the patient. It is mainly intended to help with spontaneous breathing; therefore, the patient must have an intact respiratory drive [2]. T-tube (TT) is a well-established technique of attaching the end of the endotracheal tube to a piece of pipe that acts as a reservoir and a link to the fresh humidified gas flow [3].

The transition from MV to spontaneous ventilation during the weaning process results in hemodynamic alterations and changes in the autonomous nervous system control, reflected by reduced heart rate variability (HRV) and modulation of autonomic cardiovascular functions [4].


  Aim Top


The aim is to compare between t-piece weaning tool and PSV during SBT in MV pediatric patients.


  Patients and methods Top


Methods

Study design

This was a prospective cohort comparative study carried out in ICUs, Zagazig University Hospitals, Egypt, in the period from May 2018 to October 2018. The study included all mechanically ventilated critically ill pediatric patients, who met the inclusion criteria and were candidate for weaning process from MV and fulfilling the readiness of weaning criteria. The study was approved by Ethics Committee, Faculty of Medicine, Zagazig University, Egypt. Approval no.#3739 March 2017. Well-informed verbal and written consents were obtained from parents or caregivers.

Patients

A total of 104 pediatric patients who had been admitted to ICUs, connected to MV and met the criteria for weaning and start of SBT were enrolled in the study and divided into two groups alternatively. The patients who fulfilled the inclusion criteria were randomly selected one to one, as all the even number patients started the SBT using TT, and the odd number patients started SBT on PSV mode. A total of 52 patients started SBT on TT (group I) and the other 52 on PSV (group II).

All patients enrolled in this study fulfilled the eligibility criteria for SBT: Glasgow coma scale greater than or equal to 11, normothermic, PaO2 greater than or equal to 60 and PaCO2 less than or equal to 45 mmHg, no significant respiratory acidosis (pH≥7.30).

Patients with tidal volume greater than 5 ml/kg ideal body weight and O2 saturation greater than 93% on FIO2 less than or equal to 0.4 (or PaO2/FIO2 ≥200), hemodynamically stable with no vasoactive drugs (dopamine, dobutamine, and noradrenaline) and no sedative agents, reversal of the underlying cause of MV, and the Rapid Shallow Breathing Index (this index must be in capital) (respiratory frequency/tidal volume) less than or equal to 8 breath/min/ml/kg were candidates for SBT.

Patients out of the age range or did not meet the previous criteria of weaning readiness, hemodynamically unstable, with brain stem affection or with cardiovascular diseases or dysrhythmias, or who had complications of MV were excluded from the study.

All patients included in this study were subjected to detailed history taking, full clinical assessment, laboratory investigations including complete blood count and arterial blood gases (ABG), mainly with other systemic laboratory assessments, and radiological investigations, including chest radiography, echocardiography, and ECG.

Study technique

Before starting the SBT, the traditional weaning readiness parameters were measured, such as ventilatory rate (f), tidal volume (VT), minute ventilation (VE), and rapid shallow breathing index (f/VT), to ensure that the patient is fit to start the trial.

The SBT was commenced if the patient is fit for weaning. We used Bellavista 1000 ventilator, IMT medical company, Switzerland, and Vela ventilator, Viasys (Carefusion Company, San Diego, California, USA), to complete this work. During PSV technique, the patient took breaths spontaneously, and at each respiratory cycle, the ventilator supported the patient’s breath by positive pressure synchronized with the inspiratory effort of the patient with initial slope 0.20 s. The pressure level is maintained until the ventilator detects a drop at the end of the patient’s inspiratory pressure. Patients were ventilated with pressure 5–7 cmH2O to overcome tubal resistance of ∼6–8 ml/kg with 4 cmH2O of PEEP; fraction of inspired oxygen concentration (FiO2) was set as 40% as the lowest level we can extubate on, and pressure triggering sensitivity was set as −2 cmH2O during 30–120 min. observation period [5].

During TT trial, patients spontaneously breathed, with oxygen flow of 5 l/min with FiO2: 40% during 30–120 min observation period. It consists of removing the patient from ventilator and leaving the patient to breathe spontaneously on a TT connected to a humidified oxygen source. TT connects O2 source to the airway.

SBT is aborted when the heart rate exceeded the normal range for age, increased WOB with abnormal increase in the respiratory rate (RR) for the patient’s age with obvious distress, sustained increase in systolic blood pressure out of the normal range for age, increase in end tidal CO2 (ETCO2) greater than 50 or greater than or equal to 10 mmHg increase from the level before the SBT, and peripheral SpO2 less than 85%. Whenever there were changes in one of those parameters, immediate intervention was done to reset the settings of MV according to the patient’s condition, and this SBT was considered a failed trial.

The considered vital signs according to patient’s age are as follows[3]:
  1. RR:
    • Infant (1–12 months): 30–60 breaths/min.
    • Toddler (1–2 years): 24–40 breaths/min.
    • Pre-schooler (3–5 years): 22–34 breaths/min.
    • School-age child (6–12 years): 18–30 breaths/min.
    • Adolescent (13–17 years): 12–16 breaths/min.
  2. Heart rate [3]:
    • Infant (1–12 months): 80–160 beats/min.
    • Toddler (1–2 years): 80–130 beats/min.
    • Preschool (3–5 years): 80–120 beats/min.
    • School age child (6–9 years): 70–115 beats/min.
    • Children (10–18 years): 60–100 beats/min.
  3. Blood pressure [3]: [Inline 1]


Statistical analysis

Data were statistically analyzed by the Statistical Package for the Social Sciences program, version 24 (SPSS version 26, IBM, New York, USA). The continuous data were described by mean±SD, whereas the categorical data were described by number and percentage. We use independent t test to determine if a difference is present between the independent groups. Mann–Whitney U test is a nonparametric alternative test for t-test. χ2 test is used in relation of categorical data. P value less than 0.05 is statistically significant, P value less than 0.01 is highly significant, and P value less than 0.001 is very highly significant. We use Fisher’s exact test as an alternative for χ2 test when the expected cell count is less than 5.

Ethics

The study was performed in accordance with the ethical standards of the 1964 Declaration of Helsinki, as revised in 2000, and it was approved by the ethics committee of Zagazig University (Zagazig, Egypt), Approval no.#3739, March 2017.


  Results Top


Male patients represented 51.9% in TT group and 65.4% in PSV group. Chest infection was the main cause of ventilation in both groups, as it represented 38.5% of the study cases on TT, and 46.2% on PSV, with non-statistically significant difference between both groups (P>0.05) in baseline characteristics, which were obtained just after inclusion of the patient in the study according to eligibility criteria and before the start of SBT ([Table 1]).
Table 1 Baseline characteristics and demographic data of the studied patients

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[Table 2] shows that there was a significant difference in clinical assessment of TT mode vs PSV mode patients regarding cardiac and chest examination (P<0.001), as there were significant increases in the heart rate in the form of sinus tachycardia in patients on TT (71.2%) compared with those on with PSV (9.6%), with significant difference between the two groups (P<0.001). Moreover, there were significant accumulations of secretions during SBT on TT, which demanded frequent suctioning; the chest secretions were obviously heard during auscultation of the chest of those patients, especially after we noticed increased WOB in the form of chest retractions with tachypnea and working alae nasi. Excessive chest secretion accumulation accounted for 76.9% of patients on TT compared with 15.4% from all patients on PSV.
Table 2 Clinical assessment of the studied patients on spontaneous breathing trial using TT mode and PSV mode

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By observing our patients during the SBT and compare their data with the recorded cardiovascular functions and respiratory effort before starting the trial, we found a significant alteration in the systolic blood pressure and elevation of the mean arterial blood pressure (MBP) (P<0.05) when using the TT accompanied with an increase in the WOB and increase in the heart rate, whereas no statistically significant changes were recorded in PSV group (P=0.009) ([Table 3]).
Table 3 Comparison between the autonomic cardiac functions change before and during weaning process in studied groups

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When comparing between TT and PSV modes throughout the time of the trial, there were nonsignificant changes in the HR, RR, and the blood pressure during SBT on PSV compared with significant alteration of those vital signs in TT group (P<0.05) ([Table 4]).
Table 4 Comparison between the two groups regarding autonomic cardiovascular function changes during weaning process

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PSV mode had significantly lower PCO2 and higher SaPO2 than TT mode during SBT (P<0.001 and P=0.007, respectively) ([Table 5]). The failure rate of the trial was higher with use of the TT (69.2%). It showed also that 76.9% of patients on PSV had passed the trial and were ready for extubation, in comparison with 30.8% on TT.
Table 5 Respiratory parameters during spontaneous breathing trial using TT mode vs PSV mode in the studied patients

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  Discussion Top


The study of the effect of the used mode of weaning from MV on the cardiovascular system and WOB is very important to ensure the intensivist decision on choosing a trustable, safe, less problematic, and less stressful weaning mode, which increases the probability of weaning success as all intensivists wish.

This study was carried on children with critical diseases who were admitted to PICU, Chest Intensive Care Unit, and Anesthesia Intensive Care Unit in Zagazig University Hospitals, Egypt, for a 6-month period. Patients were connected to MV and met the criteria for start of weaning and SBT. They were divided randomly into two groups based on the used mode for SBT. Group I included children started SBT using TT, and group II included children on PSV. This study compared between TT and PSV modes when used in the SBT before extubation.

The discontinuation of MV promotes a gradual increase in the WOB, and subsequently a great change in the intrathoracic pressure, leading to an increase in the venous return and the cardiac functions [6],[7]. Therefore, there are probabilities of hemodynamic instability, which may be held responsible for a higher incidence of stress and distress during this period, with subsequent weaning failure [8].

Cardiorespiratory assessment of our patients during SBT showed that sinus tachycardia accounted for 71.2% from all patients on TT compared with 9.6% from all patients on PSV with significant difference between the two groups (P<0.001). The observed sinus tachycardia made us abort the trial when exceeded the acceptable upper limit of heart rate according to patient’s age, especially, when accompanied with tachypnea and desaturation for a significant period of time that may affect the patient’s consciousness or the blood gases levels. Gentzel Chiappa et al. [3] stated that the TT mode may result in the highest acute cardiorespiratory stress, directly affecting HR.

By looking backward in the cardiovascular and respiratory parameters in each group before starting and throughout the SBT, the readings revealed a significant elevation of the heart rate, RR, systolic blood pressure, and MBP out of the normal range for age in group I (P<0.05). These findings were reported also by Gentzel Chiappa et al. [3], who detected a significant increase in MBP during TT SBT. This response denotes that the weaning procedure using TT is a stressful situation that causes an augmented sympathetic response, which can promote unfavorable HR alteration [9].

Regarding group II, there were nonsignificant alterations in the cardiovascular and respiratory parameters before and throughout the trial.

The relevance of this information lies in the fact that weaning failure usually occurs in parallel with decreased VT and elevated RR by increased WOB. Studies have suggested that patients failing the attempt of spontaneous ventilation with TT present a higher burden of the accessory inspiratory and expiratory muscles, combined with the decrease in inspiratory musculature strength needed to produce enough pressure to maintain ventilation. This finding suggested that during weaning from MV there is increased mechanical work, which may provide a higher capacity of peripheral extraction owing to a greater activity of these muscles [10]. Several studies showed that WOB is significantly higher during TT trials compared with PSV trials [10-12]. This could be explained as the TT adds to the tubal resistance more resistance and more dead space which demanded more WOB and more effort of the peripheral respiratory drive to maintain adequate gas exchange, but in some patients, this unfavorable burden cannot be overcome for a long period of time. as it is away from the physiological passage of breathing through the nose and also adds on the stress of off ventilation.

PSV makes up for the extra work imposed by the endotracheal tube and the demand valve of the ventilator [13]. This task can be accomplished with a level of pressure support of 5–7 cmH2O. PSV also amplifies the efficacy of spontaneous breathing and reduces respiratory muscles work and its oxygen consumption during spontaneous breathing after a period of support. This pressure also is just enough to overcome the resistance of ventilator circuit and imbalance between workload and muscle strength in our patients on their way for extubation [7].

Moreover, PSV mode had significantly lower PCO2 and higher SaO2 than TT mode during SBT (P<0.001). This agreed with Alexandre Doval da et al. [11], and Chatila et al. [14], who detected that the total SaO2 values were significantly more elevated during PSV, whereas Karthika et al. [7], who tested three weaning modes, namely, PSV, CPAP, and T-piece during SBT, found that there was no difference between them regarding PO2, PCO2, and pH (P>0.05). Gentzel Chiappa et al. [3] also stated that SpO2 values were maintained in both weaning modalities, but they found that there was significant increase in PETCO2 during TT, which may be associated with higher ventilator inefficiency and may stimulate chemoreceptors in the brain stem affecting HRV spectrum. There is evidence that arterial CO2 can modulate HRV by decreasing the firing rate of the autonomic nervous system.

This study reported that chest secretions were significantly higher in patients on TT mode group (76.9%) than in patients on PSV mode (15.4%) group (P<0.05), and this frequently observed significant finding made us think a lot about the source of O2 supply, which is connected to the end of the TT, as it passes through the flowmeter, which is usually not optimally humidified and its temperature is not adjustable. More than that, it is usually cold water as the compressed O2 passing through it is cold, and this may irritate the airways and stimulate more coughing and secretions and lead to distress, and so may increase the WOB and also may contribute to CO2 retention to some extent, leading to abortion of the trial [12].

Trial success represented 30.8% of patients on TT whereas failure rate was 69.2% on the same mode. In PSV mode was 76.9 and 23.1%, respectively, with significant differences in the outcome between the two groups (P<0.05). This agreed with Cabello et al. [12], who found that the outcome of weaning from MV in patients with weaning difficulties was better with PSV at initial positive pressure of 8 cmH2O during SBT than with a TT. Moreover, Ezingeard observed that the intubated patients who failed the SBT through the TT can pass it on PS of 7 or 10 cmH2O and were successfully extubated [15].

Brochard et al. [13] reported successful extubation with TT and PSV in 57.1 and 77.4% of their patients, respectively.

The cause and duration of MV before SBT process was not different statistically between the two groups (median=14 days and range from 3 to 28 days in TT group compared with median=5 days and range of 2–120 days in PSV group).

Moreover, it was found that chest diseases were the main reason of MV in both groups with nonsignificant differences between them [20 out of 52 patients weaned using TT (38.5%) compared with 24 of 52 patients weaned on PSV (46.2%)]. In addition, there were nonsignificant differences between the two groups regarding the demographic data and initial clinical assessment that set up the same basic data of both groups in the study.

We conclude from this study that PSV has less effect on the cardiovascular functions, and the WOB, in addition to increased probability of safe, smooth, and successful weaning.

Limitations of the study are as follows: first, during the TT mode, it was difficult to assess the tidal volume and minute ventilation, and so, there was no accurate monitoring of the changes in the lung volume in comparison with PSV. Second, the number of the study population was small. Third, the results might be limited because this study included only children who were admitted in Zagazig University Hospitals in Egypt.

Acknowledgements

The research was supported by Zagazig Faculty of Medicine.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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