Adherence Rate to Lung Protective Mechanical Ventilation in Patients Admitted to Surgical Intensive Care Units and Associated Clinical Outcomes
Conditions: Adult, Guideline Adherence, Humans, Intensive Care Units, Perioperative/Postoperative Complications, Respiration, Artificial, Tidal Volume
Sponsor: Mahidol University

 
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Official Title: Adherence rate to lung protective mechanical ventilation in 
patients admitted to surgical intensive care units and 
associated clinical outcomes 
Brief Title: 
Adherence to LPV in SICU and Associated Clinical 
Outcomes 
 
Principal Investigator: Annop Piriyapatsom, MD 
Affiliation: 
Department of Anesthesiology, Faculty of Medicine Siriraj 
Hospital, Mahidol University, Thailand 
 
NCT Number: N/A 
 
Updated: 
March 10, 2018 
 
 
 
 

 
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Adherence rate to lung protective mechanical ventilation in patients 
admitted to surgical intensive care units and associated clinical outcomes 
 
Introduction 
Mechanical ventilation (MV) is one of the one organ support most 
frequently applied to patients admitted to intensive care units (ICUs). Despite 
considering as a life-saving intervention, MV may have detrimental effects, 
namely ventilator-induced lung injury (VILI)(1). A mechanical breath with 
positive airway pressure may overstretch alveoli, especially in the non-
dependent part of the lungs, and subsequently result in barotrauma and 
volutrauma. While cyclic opening and closing of alveoli during mechanical 
breath due to alveolar collapse at the end of expiration can cause atelectrauma 
or cyclic atelectasis. All of these can lead to the activation of respiratory and 
systemic inflammatory response, so-called biotrauma. To minimize the effects 
of MV on VILI, the lung protective mechanical ventilation (LPV) strategy have 
been proposed and now generally accepted as a standard practice in 
mechanically ventilated patients(1-3). The LPV strategy is basically consisted of 
ventilation with low tidal volume of 6-8 mL/kg of predicted body weight 
(PBW) with limited plateau pressure of less than 30 cm H2O plus applying 
sufficient amount of positive end-expiratory pressure (PEEP) to prevent 
atelectasis(1-3). The LPV strategy has been clearly demonstrated benefits not 
only in patients with acute respiratory distress syndrome (ARDS)(4, 5) but also in 

 
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those with normal lungs(1, 6, 7) including lessened respiratory and systemic 
inflammatory response and injured lungs, decreased duration of MV and length 
of stay (LOS), improved organ failure, and decreased pulmonary and other 
complications as well as mortality. Nevertheless, the adherence rate to the LPV 
strategy reported in the literatures is only approximately 40% in mechanically 
ventilated patients(8) and patients with ARDS(9-11). For surgical patients, 
approximately 65% of those admitted to ICU require MV support either 
following operation or during their stay in ICU(12). To date, there is limited data 
regarding MV management in surgical patients who required MV support 
perioperatively. Similarly, the difference in perioperative MV practices and 
their associated clinical outcomes has been not well determined in this setting. 
Therefore, the aim of this study is to explore the current practice of MV 
according to the LPV strategy applied to surgical patient admitted to surgical 
ICU (SICU) and their associated clinical outcome.  
 
 
 

 
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Methods 
Study design and patient population. This is a prospective observational 
cohort study conducted in two SICUs at Siriraj Hospital. Generally, patients 
undergoing vascular, abdominal, urological, head and neck, orthopedic, plastic, 
otorhinolaryngologic, gynecologic, obstetric, and ophthalmologic surgeries who 
require perioperative care in ICU are admitted to these two SICUs and are 
eligible for inclusion. Patients undergoing cardiothoracic, neurological, trauma 
surgery and pediatric patients are admitted to other specific ICUs and are not 
included in this study. All patients whose age of 18 years old or more admitted 
to these two SICU and requiring MV support, either at SICU admission or 
during stay in SICU, via either endotracheal or tracheostomy tube with 
anticipated duration of 12 hours or more are included. Patients not requiring 
MV support during SICU stay, those requiring MV support for less than 12 
hours in SICU, those requiring MV support for more than 24 hours prior to 
SICU admission, those included in this study once and re-admitted to the SICU, 
those requiring non-invasive MV support, moribund or terminal cases, and 
those who refuse to participate in the study are excluded from this study. 
Writing informed consents are obtained from all included patients or their 
relatives prior to inclusion or as soon as possible.  
Study procedure. The inclusion is started on the day of the initiation of 
MV support, which is labeled as the index day. All included patients receive all 
medical care including resuscitation, medication, and MV support based on the 

 
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discretion of the primary care team. They are daily evaluated for 7 consecutive 
days following the index day or until they are discharged form the SICU or are 
deceased, whichever comes first. Ventilator parameters are recorded on the 
index day and then once a day between 06:00 and 09:00 in the morning for 3 
consecutive days following the index day or until MV is liberated or patients are 
discharged form the SICU or are deceased, whichever comes first. The day of 
the liberation from MV is recorded. Pulmonary and other complications 
occurred during 7 days of the observation, SICU and hospital discharge status 
as well as status at 90 days following the index day are also documented. At 90 
days following the index day, patients are followed up in the hospital if they are 
still admitted or by phone call if they have been discharged from the hospital. 
Data collection. Demographic and baseline data recoded on the index day 
include age, gender, weight, height, comorbidities, smoking status and alcohol 
use (either never, stopped, current, or unknown), diagnosis at SICU admission, 
operation, type (either elective or emergency), site (thoracoabdominal, upper 
abdominal, lower abdominal, vascular, urological, head and neck, orthopedic, 
gynecologic and obstetric), and duration of surgery, intraoperative fluid balance, 
reasons for SICU admission (either planned SICU admission following elective 
or emergency surgery, unplanned SICU admission following elective or 
emergency surgery, or admission due to medical condition), reasons for MV 
support (after general anesthesia for surgery, respiratory failure, hemodynamic 
instability, or post-cardiac arrest), laboratory values, arterial blood gas, chest 

 
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radiograph, requirement of inotrope/vasopressor, presence of sepsis, ARDS, and 
acute kidney injury (AKI), Acute Physiology and Chronic Health Evaluation 
(APACHE) II score, Sequential Organ Failure Assessment (SOFA) score, 
predictive score for postoperative pulmonary complications (PCCs)(13), and lung 
injury prediction score (LIPS)(14). Daily evaluations include hemodynamic and 
clinical parameters, SOFA score, and fluid balance. Ventilator parameters 
include modes of MV, expired tidal volume, level of PEEP, measured 
respiratory rate, peak and plateau pressure or maximal airway pressure, fraction 
of inspired oxygen (FiO2), inspiration to expiration ration (I:E), minute 
ventilation, use of neuromuscular blocking agents, and arterial blood gas 
corresponding to the setting of MV. Pulmonary complications include 
pneumonia, ARDS, atelectasis, restoration of MV support after liberation from 
MV, pleural effusion, cardiogenic pulmonary edema, pneumothorax and new 
pulmonary infiltration. Other complications include stroke, myocardial 
ischemia/infarction, arrhythmias, AKI, sepsis, new infection other than 
pneumonia, and re-admission to the SICU. Duration of MV support, LOS in 
SICU and in hospital, SICU and hospital discharge status and status at 90 days 
either alive or death as well as activities of daily living measured by the Thai 
version of the Barthel index(15) are also collected.  
Study outcomes and sample size calculation. The primary outcome of this 
study is to determine the adherence rate to the LPV strategy at the initiation of 
MV support in mechanically ventilated patients in SICU. The LVP strategy in 

 
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this study is defined as ventilation with tidal volume of <8 mL/kg of PBW plus 
applying PEEP of at least 5 cm H2O. Based on the previously reported 
adherence rate to the LPV strategy in mechanically ventilated patients of 
approximately 40%(8-11) with 80% power and 95% confidence interval, a sample 
size of 213 subjects is required. After 10% inflation for possible missing data, 
235 subjects are planned to include. The secondary outcomes are factors 
associated with the adherence to the LPV strategy, incidences of pulmonary and 
other complications, LOS in SICU and in hospital, SICU and hospital discharge 
status, and status at 28 and 90 days following the initiation of MV support.  
Statistical analysis. Data are expressed as mean with standard deviation, 
median with interquartile range (IQR) or number with percentage as 
appropriate. Student’s t-test or Mann-Whitney U test is used to compare 
continuous variables, and chi-squared test or Fisher’s exact test is used for 
categorical variables as appropriate. Univariate analyses are performed to 
identify potential factors associated with the adherence to the LPV strategy. A 
multivariate logistic regression model is used to identify the independent factors 
using stepwise approach to enter new variables with p-value of less than 0.2 into 
the model. Time-to-event variables are analyzed using Cox regression and are 
visualized by Kaplan–Meier curve. All statistical analyses are 2-tailed and p-
value of less than 0.05 is considered as statistical significance. Data are 
prepared and analyzed using PASW Statistics 18 (SPSS Inc., Chicago, IL, 
USA). 

 
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