Value of Automatic Tube Compensation In Weaning of Mechanically Ventilated Patients in Medical Intensive Care Unit
Mohamed Abouzeid.1, Ahmed E. Kabil.2 and Ahmed Al-Ashkar 1
1Department of Internal Medicine , Al-Azhar University, Cairo, Egypt
2Department of Chest diseases, Al-Azhar University, Cairo, Egypt
muhamedabozeid@gmail.com , a_ka_81@ hotmail.com,dr_alashkar@yahoo.com
Abstract: Background: Automatic tube compensation (ATC) has been recently introduced to compensate for artificial airway resistance that may be beneficial during spontaneous breathing trials. It has been used as a mode of mechanical ventilation in some newer mechanical ventilators and as an add-on feature for existing ventilation modes in some other ventilators. Objective: To assess the expected value of ATC in the weaning process . Patients and methods: A prospective randomized controlled study was conducted at Medical Intensive Care Unit of Al-Hussein University Hospital, Cairo. 60 mechanically ventilated patients were included during the period from September 2016 to June 2017 .Patients were randomly divided into three groups, 20 patients weaned by pressure support ventilation (PSV) plus ATC, 20 patients weaned by pressure support ventilation (PSV) alone and 20 patients weaned by ATC alone. The primary outcome measure was comparison between different groups in weaning outcomes and duration of weaning. Results: There was no significant difference between the three groups as regard demographic data, cause of admission or baseline characters at the start of randomization. The weaning duration of PSV plus ATC group was significantly lower than other groups. The duration of weaning in ATC group was lower than PSV group. There was a higher trend towards Successful extubation in PSV plus ATC group than other groups but without statistically significant difference. Mortality and morbidity were lower in PSV plus ATC group than other groups and were lower in ATC group than PSV group but without statistically significant difference. Conclusion: In Medical ICU patients, the weaning process can be successfully performed by ATC as an add-on feature to existing modes or as a separate mode. Duration of weaning, total duration of mechanical ventilation and duration of ICU stay were significantly lower with ATC .
Keywords: automatic tube compensation, pressure support ventilation, medical ICU, weaning.
1. Introduction
Weaning is the process of withdrawing mechanical ventilatory support and thus transferring the work of breathing from the ventilator to the patient himself. Weaning is a very critical step in the process of mechanical ventilation and still a great challenge. Weaning prolongation is related to increased mortality and morbidity (1).Recently, with the great advances in technology, new features on ventilators have been developed as automatic tube compensation (ATC) which may be a separate mode or as an add-on to other modes. Small trials have been done to evaluate weaning outcome using either this new mode or add-on feature to traditional modes with a promising results (2’5). With the passage of air through the artificial tube there will be a difference in pressure between the two ends of the tube and the patients respiratory system have to compensate for this pressure difference especially with spontaneous breathing trials and weaning. ATC acts by continuous calculations of the pressure difference between the two ends of the tube. This calculation is based on regular measurement of air ‘ow, airway pressure difference ( between both ends of the tube) and tube specific co-efficient (6). ATC works to compensate automatically for the pressure difference across the tube and delivering the exact amount of pressure needed to overcome this resistive load (7). On the other hand, tube obstructions as a result of secretions or kinking may cause under compensated tube resistance with this feature (8.9). In recent studies ATC has been shown to decrease the work of breathing(WOB) used to overcome the resistive load of artificial airways more effectively than traditional methods of weaning . It is assumed that it can mimic spontaneous breathing without the artificial airways, so it can be called (electronic extubation) (10). It is believed that ATC may decrease the weaning period and increase the probability of successful extubation (11).
The aim of the study was to evaluate the value of ATC either as a mode ventilation or as an add-on feature to other modes in the process of weaning.
2. Patients and methods
This prospective randomized controlled study was conducted from September 2016 to June 2017, in the Medical Intensive Care Unit of Al-Hussein University Hospital , Cairo. The study included 60 mechanically ventilated patients. An informed written consent was taken from the first degree relative of every patient included in the study & the study was approved by the Ethics Committee For Research Of Faculty Of Medicine, Al-Azhar University.
Inclusion criteria:
Adult patients who were endotracheally intubated, undergoing mechanical ventilation for at least 24 h and ready for weaning, according to our MICU’s ventilator weaning protocol that follows the current statement of ERS, ATS, ESICM, SCCM and SRLF (12).
Exclusion criteria: Age > 18 years, Pregnancy, Unplanned extubation either during or before the weaning process, Death before becoming ready to wean or patients who completed 7 days of mechanical ventilation without fulfilling weaning criteria .
Initiation of mechanical ventilation
All included patients were intubated with endotracheal tube size 7 to 8. Mechanical ventilation performed using Dr”ger Evita V 300. Patients were adjusted on Synchronized Intermittent Mandatory Ventilation (SIMV), volume controlled mode except for cases with Adult Respiratory Distress Syndrome (ARDS) where pressure controlled ventilation was used with lung protective strategy.
All patients were receiving standard medical therapy . Sedation was achieved with midazolam and adjusted for each patient according to his or her need and stopped when the patient was ready for the weaning.
Patients randomization and weaning
Weaning was decided after achievement of the weaning criteria of the guidelines of ERS, ATS, ESICM, SCCM and SRLF (12).patients were randomly divided into three groups; Group (I) included 20 patients who were weaned by automatic tube compensation with pressure support (PSV+ATC),Group (II) included 20 patients who were weaned by pressure support ventilation alone (PSV) , Group (III) included 20 patients who were weaned by automatic tube compensation (ATC) alone .
The weaning protocol for the three groups:
weaning from MV was decided as early as possible with a daily screen for assessment of readiness to wean. Spntanous breathing trial (SBT) was performed early in the morning . The SBT was performed with either PSV, ATC or PSV plus ATC. In all groups, the ventilator parameters were adjusted as the following: the peak end expiratory pressure at 0’5 cmH2O with FiO2 less than or equal to 0.4. In the PSV plus ATC group (20 patient), initial positive pressure support (PS) was set at 15 cmH2O. Patients were extubated at PS of 8 cmH2O and in the same situation the size of the tube was entered into the ventilator software and inspiratory ATC set at 100%. For the patients weaned by PSV only (20 patients), initial positive pressure support (PS) was set at 15 cmH2O. PS was gradually lowered by 2’4 cmH2O.Extubation was done at PS of 8 cmH2O (which is suggested to be equal to tube resistance). In the ATC group (20 patients), the size of the tube was entered into the ventilator software and inspiratory ATC set at 100%.Pressure support was adjusted at zero (The type of ventilators used in current study has only ATC as add-on feature to other modes, so we used PS with ATC and set PS at zero to equal ATC mode only in other types of ventilators). If the first SBT failed, all subsequent SBTs were done with the same SBT method.
Patients were observed for dyspnea, fatigue, anxiety, and distress during SBT. The criteria for successful SBT include good respiratory pattern, efficient gas exchange, hemodynamic stability, and patient comfort (12).
Mechanical ventilation (by the same mode) was returned with any of the following:
Tachypnoeic (Respiratory rate ‘ 35 breaths/min), Desaturation (oxygen saturation < 90%.), Heart rate >140 beats/min or a sustained increase or decrease in the heart rate of more than 20% of that before starting weaning. Systolic blood pressure < 90 mmHg or > 180 mmHg, Agitation or diaphoresis, Hypercapnia with increased level of PaCO2 ‘ 20% from the previous value. deterioration of the neurological status , including psychomotor agitation (13).
Weaning success: defined as independence from mechanical ventilation ( either invasive or non-invasive) ‘ 48 hours after extubation., Weaning failure: was considered with any one of the following: Failure of spontaneous breathing trials, Re-intubation and/or resumption of MV within 48 hours of extubation, Death within 48 hours of extubation(13) .
Length of ICU or hospital stay: the time from admission to the ICU or the hospital until discharge or death., Complications related to MV: such as, VAP, pneumothorax & tracheostomy
The following data were collected from all groups to be statistically analyzed and compared: Demographic data (age, sex & BMI) ,APACHII, Hemodynamic parameters (heart rate, respiratory rate and mean
arterial blood pressure) before randomization & before successful extubation, Ventilator parameters 1 hour after randomization & before successful extubation (FIO2, peak airway pressure, VT, RR, minute ventilation & auto-PEEP)which were considered as the mean of three successive breath cycles at least,
Arterial blood gases (ABGs) before randomization, one hour after randomization & before successful extubation, Duration of weaning, Duration of mechanical ventilation, Length of ICU stay, Length of hospital stay, Complications: including VAP, pneumothorax, arrhythmia, tracheostomy, re-intubation & deaths.
Statistical Analysis The collected data was organized, tabulated and statistically analysed using SPSS software statistical computer package version 16. For qualitative data, frequency and percent of distribution were calculated and for comparison between groups, chi-square test was used. For quantitative data, mean, standard deviation (SD) and sometimes, median, minimum and maximum were calculated. The (one way Anova test) was used for comparison between normally distributed quantitative variables, and when P-value ‘ 0.05 (Tukey-Kramer test) was used for multiple comparison between groups., (Kruskal-Wallis non-parametric test) was used for comparison between abnormally distributed quantitative variables, and when P-value ‘0.05, (Dunn's multiple comparisons test) was used for multiple comparisons between groups. For interpretation of results, p-value ‘ 0.05 was considered statistically significant
3. Results
Table (1): Demographic data and baseline difference between the studied groups:
ANOVA ATC PSV PSV+ATC Groups
P-value
.779 59.500”3.9537 60.500”4.5480 59.800”5.1667 Age
.918 15
34.1% 14
31.8% 15
34.1% Male
. 918 5
31.3% 6
37.5% 5
31.3% Female
.046 24.400”1.7592 24.700”1.8093 23.250”2.0995 BMI
0.38 24.14”4.22 21.14”2.89 23.14”4.89 APACHE II
Continuous data are presented as mean ” SD, whereas categorical variables are presented as frequency and %; APHCHE II, *Significant difference.
Table (2) Diagnosis of patients on ICU admission
Total ATC PSV PSV+ATC Diagnosis
16
100.0% 5
31.3% 4
25.0% 7
43.8% Pneumonia
10
100.0% 3
30.0% 4
40.0% 3
30.0% Sepsis
12
100.0% 4
33.3% 3
25.0% 5
41.7% COPD exacerbation
15
100.0% 5
33.3% 6
40.0% 4
26.7% CNS CAUSE
7
100.0% 3
42.9% 3
42.9% 1
14.3% Pulmonary edema
.927 P-value
Table ( 3): Vital signs and blood gases at the start of weaning trial
ANOVA ATC PSV PSV+ATC Groups
P-value
.080 87.000”5.6382 83.000”7.4763 82.900”6.0689 Heart rate
.401 92.500”6.0654 92.000”6.4400 89.950”6.3035 Mean
arterial BP
.057 20.350”2.0844 18.400”2.7415 19.050”2.7810 Respiratory
Rate
.875 .4100”.04757 .4125”.04552 .4175”.04667 FIO2
.116 7.4145”.04371 7.3890”.03782 7.3865”.05575 PH
.281 73.250”5.0667 73.450”4.9148 75.350”3.4985 PO2
.656 48.150”4.6597 49.050”5.6798 47.600”4.6611 PCO2
.241 30.700”3.4808 31.500”4.0717 32.600”2.9451 HCO3
ATC, automatic tube compensation; BP, blood pressure; PSV, pressure support ventilation.
Table ( 4 ): Comparison between the ventilatory parameters of studied groups one hour after weaning trial:
ANOVA ATC PSV PSV+ATC Parameter
P-value
.122 .3950”.02763 .3750”.03804 .3825”.02447 FIO2
.066 21.650”2.4121 22.550”2.5438 20.700”2.3864 Respiratory rate
(RR)
.013 .5795”.06863 .5860”.05124 .5280”.07431 Tidal volume
(VT)
.006 21.550”1.9861 19.700”2.2029 19.550”2.1637 Peak inspiratory
pressure (PIP)
.954 8.955”1.5497 8.850”1.2185 8.825”1.4920 Minute
ventilation (MV)
Table ( 5): Comparison between the ABG parameters of studied groups one hour after weaning trial:
ANOVA ATC PSV PSV+ATC Parameter
P-value
.034 .3950”.02763 .3725”.03432 .3675”.04064 FIO2
.108 7.4025 ”.03127 7.4145” .03561 7.3930”.02774 PH
.025 80.100”2.7701 80.550” 3.0689 82.800” 3.8471 PO2
.266 51.100”4.6215 50.350” 5.0915 52.750” 4.4114 PCO2
.106 30.100 ”2.5526 32.000” 3.2767 31.050” 2.4382 HCO3
4. Discussion
Automatic tube compensation (ATC) is a recently developed mechanical ventilatory support method to overcome the endotracheal tube resistance. It is used as a mode of ventilation in some ventilators while in others it is used as an add-on feature to other modes. Pressure support ventilation (PSV) is a common mode for providing support during weaning from mechanical ventilation. It generates a constant pressure that
complements patient effort throughout the inspiratory period (14,15),.In this prospective controlled trial, 60 patients were recruited in with the aim of the comparing automatic tube compensation with pressure support (PSV) in weaning of different diseases, patients were divided into 3 groups: group (I) included 20 patients who were weaned by automatic tube compensation with pressure support. (PSV+ATC), group (II) included 20 patients who were weaned by pressure support alone (PSV), group (III) included 20 patients who were weaned by automatic tube compensation alone (ATC), All patients were ready for weaning after improvement of general conditions, gas exchange & respiratory acidosis. In the present study, there was no statistically significant difference in the age of the studied groups .Also, there was no statistically significant difference in gender distribution & BMI between studied groups, with predominant male gender in each group .
Table (6): Weaning course and outcome
ANOVA Total ATC
(n=20) PSV
(n=20) PSV+ATC
(n=20) Parameter
P-value N=60
.573 3.050”.5356 3.125” 1.0867 2.875”.5350 Duration of MV (Days) before
Weaning trial
.004 54.000” 29.0631 83.500” 47.3142 36.714” 21.5779 Duration of weaning (hours)
.482 1.750”.5620 2.000”.5620 1.800”.8944 Number of spontaneous breathing trials
.803 13
65% 12
60% 14
70% successful extubation after weaning trials
1.000 4
20 % 5
25% 4
20% Complications during weaning process(VAP)
.906 13 4 5 4 ICU mortality
.005* 5.538” 1.2659 6.750” 1.3568 4.464”.7712 Total duration of MV (Days)
.041* 8.462” 1.1080 9.208” 1.7511 7.821” 1.1026 Duration of ICU stay (Days)
.076 13.000” 1.6833 13.500” 1.4460 12.071” 1.5915 Duration of hospital stay (Days)
.121 1.7000”.47016 1.8500”.36635 1.5500”.51042 Failure of first spontaneous breathing trials
.482 1.750”.5620 2.000”.5620 1.800”.8944 Number of spontaneous breathing trials
Moreover, there was no significant difference between the studied groups in mean APACHE II score at time of ICU admission or cause of mechanical ventilation.
In addition, there was no statistically significant difference in vital signs and arterial blood gases of the studied groups before starting weaning trial and randomization.
So, there were no significant differences in baseline characteristics between the studied groups . and we can suggest that the three methods of weaning ((PSV+ATC, PSV & ATC) ) can be conveniently compared with each other in terms of weaning
progress and outcome and also length of stay, the occurrence of
complications, and mortality rate(5).
In the current study the ventilatory parameters of the studied groups one hour after randomization showed, statistically significant decrease in the peak inspiratory pressure (PIP) & the tidal volume (VT) of the PSV+ATC group than other groups. Apart from the peak inspiratory pressure and tidal volume, there was no statistically significant difference between the studied groups of the current study in other ventilatory parameters one hour after randomization. Also, The ABG parameters in the current study showed a statistically insignificant difference between studied groups one hour after randomization. These results are consistent with Figueroa-Casas et al. (2010) who posted that RR/TV ratio and Pao2/Fio2 had no significant difference between ATC group and CPAP group. Selek et al. (2014) reported that no significant difference as regard respiratory rat and SaO2 over the course of the study period between ATC and T-piece. On the other hand, Haberthur et al. (2002) stated that there were significant difference between both groups in respiratory rate, tidal volume and RR/TV ratio.
Before starting weaning in the current study, there was no statistically significant difference between the studied groups in the duration of mechanical ventilation . the weaning duration of PSV+ATC group was significantly lower than ATC group and that of ATC group was lower than PSV group (but statistically insignificant) .
In agreement with our results, Aggarwal et al. (2009) concluded that duration of weaning was significantly shorter in the PSV plus ATC group than in the PSV group in patients with severe neuroparalytic snake envenomation.
In addition ,Figueroa-Casas et al. (2010)reported non-significant trend toward shorter duration of weaning trials with ATC than PSV.
Also, Selek et al. (2014) found weaning duration was significantly shorter in ATC versus T-piece.
Despite significant shortening in the duration of mechanical ventilation of PSV+ATC group than ATC & PSV groups in the current study, the length of ICU stay & the duration of hospital stay did not differ
significantly among studied groups
. In the current study, weaning success was achieved in 14 patients
(70%) of PSV+ATC group, 13 patients (65%) of ATC group & 12 patients (60%) of PSV group, without statistically significant difference among studied groups in the outcome of weaning.
Comparable to the results of the present study, El-Shahat, et al., 2014 who studied 166 mechanically ventilated patients ready for weaning, Comparing ATC mode with PSV mode: was no statistically significant difference between studied groups in weaning success where was achieved in 69 patients (78.4%) of PSV & 69 patients (88.5%) of ATC group, without statistically significant difference among studied groups in the outcome of weaning. Also these results were consistent with Haberthur and colleagues, and Figueroa-Casas and colleagues,
who concluded nearly the same result with different numbers.
Mortality and morbidity were lower in PSV plus ATC group than other groups and were lower in ATC group than PSV group. However, there was no statistically significant difference among studied groups of the current study in the rate of mortality and the complications related to mechanical ventilation. These results are consistent with El-Shahat and colleagues who concluded a non-significant decrease in mortality and complications with ATC.
The main limitations of our study are low number of patients included and it was a single center study.
So large multi-centers studies are recommended for further evaluation of ATC either add-no feature or a separate mode in the process of weaning of mechanically ventilated patients.
Conclusion:
According to the current study results, we can conclude that in a medical ICU population, ATC (either as add-on feature or as a separate mode ) was safe , efficient, and can be successfully used for weaning. It has a potential benefit in weaning duration, extubation outcome, ICU length of stay, complications, and mortality rate . So, ATC may be a valuable add-on feature or mode for use during the process of weaning of mechanically ventilated patients.
Financial support and sponsorship
Nil.
Con’icts of interest
There are no con’icts of interest
References
1- Chang DW & Hiers JH. (2013b): Weaning from mechanical ventilation. In: Clinical applications of mechanical ventilation fourth Edition. Chang DW, United States of America. Delmar Cengage learning, Chapt. 16, p. 516-536
2- Cohen JD, Shapiro M, Grozovski E, Singer P. Automatic tube
compensation-assisted respiratory rate to tidal volume ratio improves the
prediction of weaning outcome. Chest 2002; 122:980’984.
3- Cohen JD, Shapiro M, Grozovski E, Lev S, Fisher H, Singer P. Extubation
outcome following a spontaneous breathing trial with automatic tube
compensation versus continuous positive airway pressure. Crit Care Med
2006; 34:682’686.
4- Cohen J, Shapiro M, Grozovski E, Fox B, Lev S, Singer P. Prediction
of extubation outcome: a randomised, controlled trial with automatic
tube compensation vs. pressure support ventilation. Crit Care 2009;
13:R21.
5- Selek C, Ozcan PE, Orhun G, ”enturk E, Akinci IO, Cakar N The
comparison of automatic tube compensation (ATC) and T-piece during
weaning. Turk J Anaesth Reanim 2014; 42:91’95.
6- Haberthur C, Mols G, Elsasser S, Bingisser R, Stocker R, Guttmann J.
Extubation after breathing trials with automatic tube compensation,
T-tube, or pressure support ventilation. Acta Anaesthesiol Scand 2002;
46:973’979.
7- Frutos-Vivar F, Esteban A. Weaning from mechanical ventilation:
why are we still looking for alternative methods? Med Intensiva 2013;
37:605’617.
8- Haberthur C, Mols G, Elsasser S, Bingisser R, Stocker R, Guttmann J.
Extubation after breathing trials with automatic tube compensation,
T-tube, or pressure support ventilation. Acta Anaesthesiol Scand 2002;
46:973’979.
9- Oto J, Imanaka H, Nakataki E, Ono R, Nishimura M. Potential inadequacy
of automatic tube compensation to decrease inspiratory work load after at
least 48 hours of endotracheal tube use in the clinical setting. Respir Care
2012; 57:697’703.
10- Eskandar N, Apostolakos MJ. Weaning from mechanical ventilation. Crit
Care Clin 2007; 23:263’274.
11- Aggarwal AN, Agarwal R, Gupta D. Automatic tube compensation as
an adjunct for weaning in patients with severe neuroparalytic snake
envenomation requiring mechanical ventilation: a pilot randomized study.
Respir Care 2009; 54:1697’1702.
12- Boles JM, Bion J, Connors A, Herridge M, Marsh B, Melot C, Pearl R & Silverman H. (2007): Weaning from mechanical ventilation. Eur Respir J 2; 29:1033’56
13- Boles JM, Bion J, Connors A, et al. Weaning from mechanical ventilation. Eur Respir J. 2007;29(5):1033-1056.
14- Prakash P, Krishna K & Singh P. (2007): Weaning Modes in Mechanical Ventilation. JIACM; 8(3): 222-5.
15- Prakash P, Krishna K, & Bhatia D. (2006): Complications of Mechanical Ventilation. Journal, Indian Academy of Clinical Medicine, 7(3).’
16- Figueroa-Casas JB, Montoya R, Arzabala A, Connery SM. Comparison
between automatic tube compensation and continuous positive airway
pressure during spontaneous breathing trials. Respir Care 2010; 55:549 ‘554.
17- El-Shahat H, Salama S, Wafy S, Bayoumi H.(2015): Automatic tube compensation versus pressure support ventilation as a weaning mode: does it make a difference?. Egypt J Broncho 2015 9:253’260.