|Year : 2018 | Volume
| Issue : 3 | Page : 35-41
Pressure-regulated volume control mode versus synchronized intermittent mandatory ventilation mode in management of acute respiratory failure complicating advanced liver disease
Rafik Yousset Atalla, Dalia Fahmy Emam, Wail Ahmed Abdelaal
Department of Anesthesia and Intensive Care, Ain Shams University, Cairo, Egypt
|Date of Submission||09-May-2018|
|Date of Acceptance||24-Dec-2018|
|Date of Web Publication||24-May-2019|
Wail Ahmed Abdelaal
Assistant Professure of Anesthesia and Intensive Care, Ain Shams University, Cairo
Source of Support: None, Conflict of Interest: None
Background A common cause of death in the ICUs is advanced liver disease and its complications. Respiratory complications are common in patients with advanced liver disease. Management of patients with advanced hepatic disease having acute respiratory failure mandates the use of lung-protective ventilation strategies to achieve adequate oxygenation.
Objectives The aim of this study was to compare and evaluate the superiority of either pressure-regulated volume control (PRVC) mode versus synchronized intermittent mandatory ventilation (SIMV) mode in management of acute respiratory failure complicating advanced hepatic disease.
Patients and methods A total of 80 patients were included in this study, who were randomized into two equal groups of 40 patients each, namely. group S and group PV. Group S was ventilated using SIMV mode, whereas group PV was ventilated using PRVC mode.
Results There was a statistically significant difference between group PV and group S during the mechanical ventilation period regarding the PO2/FiO2 ratio, static compliance, and dynamic compliance values, with higher values in group PV than group S providing better oxygenation. There was a statistically significant difference in the duration of mechanical ventilation and the ICU stay between the two groups, with significantly lower values in the PV group than the S group.
Conclusion We concluded that PRVC mode of mechanical ventilation is superior to SIMV in acute respiratory failure complicating advanced liver disease, as it resulted in improved oxygenation at lower inflation pressures.
Keywords: advanced liver disease, pressure-regulated volume control mode, synchronized intermittent mandatory ventilation mode
|How to cite this article:|
Atalla RY, Emam DF, Abdelaal WA. Pressure-regulated volume control mode versus synchronized intermittent mandatory ventilation mode in management of acute respiratory failure complicating advanced liver disease. Egypt J Cardiothorac Anesth 2018;12:35-41
|How to cite this URL:|
Atalla RY, Emam DF, Abdelaal WA. Pressure-regulated volume control mode versus synchronized intermittent mandatory ventilation mode in management of acute respiratory failure complicating advanced liver disease. Egypt J Cardiothorac Anesth [serial online] 2018 [cited 2019 Sep 16];12:35-41. Available from: http://www.ejca.eg.net/text.asp?2018/12/3/35/258996
| Introduction|| |
Advanced liver disease is a common cause of death in ICU patients, as it leads to systemic vascular resistance reduction, sodium retention, hyperdynamic circulation, and intravascular volume expansion , with subsequent hepatic decompensation and its complications, including the development of spontaneous bacterial peritonitis, ascites, variceal hemorrhage, and/or hepatic encephalopathy .
Respiratory complications are common in patients with advanced liver disease, and it is mandatory to evaluate respiratory functions in these patients . Limited pulmonary reserve may result from muscle wasting  and elevation of diaphragm from ascites and hepatomegaly, or effusion leading to reduction in lung compliance . This alteration has a limited response to high FiO2 and only positive end-expiratory pressure (PEEP) may be beneficial . The hallmark is acute respiratory distress syndrome (ARDS), which is radiologically manifested as pulmonary infiltrates on chest radiography and computed tomography chest .
Although the optimal mechanical ventilation strategy for critically ill patients with acute lung injury (ALI) or ARDS is uncertain , lung-protective strategies with low tidal volume ventilation and PEEP are the main therapy to avoid ventilator-induced lung injury .
The relationship between hepatic disease and hypoxemia cannot be explained by simple mechanism , but ascites, severe anemia, hepatopulmonary syndrome, low albumin levels, respiratory muscle weakness, and hepatomegaly are factors leading to hypoxemia in patients with advanced liver disease .
Hepatopulmonary syndrome is classically manifested by evidence of portal hypertension or liver disease, in addition to an elevated age-adjusted alveolar-arterial oxygen gradient (AaPO2) and evidence of intrapulmonary vasodilatation ,,.
Precapillary pulmonary hypertension in patients having advanced hepatic disease or portal hypertension can be related to hyperdynamic circulation resulting in shear stress in pulmonary vascular bed in addition to the increased pulmonary vascular volume and vasoactive substances such as endothelin ,.
Airway control with endotracheal intubation is a must inpatients advanced hepatic disease with a Glasgow coma scale score of less than 8 and/or in the presence of active upper gastrointestinal bleeding . Management of patients with advanced hepatic disease having acute respiratory failure mandates the use of lung-protective ventilation strategies to achieve adequate oxygenation, and plateau pressures less than 30 cmH2O to avoid further lung injury . To decrease discomfort resulting from intubation, sedatives are rarely used as they delay weaning and affect conscious level, and patients can also be managed with intermittent narcotic administration with extubation as they are able to protect their airway .
Pressure-regulated volume targeted (PRVC) mode is used during lung-protective ventilation, as the variable, high, peak inspiratory flow rate reduces the work of breathing, where all patient breaths are mandatory, the rate is fixed, and the inspiratory pressure is varied maintaining a preset tidal volume .
The aim of this study was to compare and evaluate the superiority of either PRVC mode versus synchronized intermittent mandatory ventilation (SIMV) mode in management of acute respiratory failure complicating advanced hepatic disease, regarding improvement of oxygenation, need for vasopressor support, and sedation as well as incidence of complication and mechanical ventilation days.
| Patients and methods|| |
This study was conducted on adults with advanced liver disease after informed written consent was obtained from all patients or their legal guardians. It was done between January and November 2017 at the Ain Shams University Hospital. The study protocol was approved by the Research and Review Board and Ethical Committee of the Anesthesia and Intensive Care Department, Ain Shams University.
The diagnosis of liver disease was done by clinical examination, laboratory investigations, and abdominal ultrasound assessment. Adult patients with advanced liver disease and diagnosed with respiratory failure (acute onset of new or worsening respiratory symptoms within 1 week, bilateral chest opacities, and respiratory failure not fully explained by cardiac failure) were included.
Oxygenation index (OI) or hypoxic index was used as a measure of oxygenation using the PO2/FiO2 (P/F) ratio: in mild cases − (P/F), 201–300 mmHg; moderate cases − (P/F), 101–200 mmHg; and severe cases − (P/F) less than or equal to 100 mmHg.
Exclusion criteria included patient refusal, ages less than or equal to 18 years or more than or equal to 65 years, coexisting primary pulmonary pathology or penetrating chest injury, septicemia, pregnancy, congestive heart failure, third-degree burns with or without inhalational injury, and patients presenting with any form of barotraumas (subcutaneous emphysema, pneumothorax, pneumoperitoneum, pneumopericardium, and pneumomediastinum).
Patients who fulfilled all the inclusion/exclusion criteria were randomized into two equal groups, namely, group S and group PV. Group S was ventilated using SIMV mechanical ventilation mode, whereas group PV was ventilated using PRVC mode.
Settings of the mechanical ventilation were adjusted according to individual patient response to keep SpO2 more than or equal to 89–93%, and plateau inspiratory pressure was limited to less than or equal to 35 cmH2O. PEEP and FiO2 were titrated to maintain an oxygen saturation of 89–93% with the least FiO2 and a PEEP level never less than 5 cmH2O.
Respiratory rate, ratio of inspiration to expiration, and either the targeted volume in the PV group or the S group were adjusted to keep PaCO2 at 35–45 mmHg, but hypercapnia was accepted if this target could not be achieved with a plateau pressure less than 36 cmH2O.
For both groups, when the arterial pH was less than 7.20, intravenous sodium bicarbonate was given, and if the pH remained less than 7.20 despite bicarbonate sodium infusion, the targeted volume in the PV group or the inspiratory pressure in the S group was increased until the pH reached more than or equal to 7.20.
In any patient when the hypoxic index PO2/FIiO2 (P/F) ratio reached alevel of less than 100 mmHg, patient was mechanically ventilated using Newport e 360 mechanical ventilator (Medtronic, Minnesota, USA). For both groups, adjustments of the ventilation settings were the responsibility of the attending physician according to the clinical condition, and the data were collected from each patient.
All patients were thoroughly evaluated with full history taking and clinical examination. Special attention was given for abdominal, chest, and heart examinations. Laboratory investigations included complete blood count, fasting blood sugar, erythrocyte sedimentation rate, liver function tests (total and direct bilirubin, serum albumin, aspartate aminotransferase, alanine aminotransferase, gamma glutamyl transferase, alkaline phosphatase, and prothrombin time), kidney function tests, HBsAg, HCV antibody, and serum alpha-fetoprotein.
Radiological investigations included plain chest radiography (both lateral and posteroanterior views) and abdominal ultrasonography (with convex probe 5 MHz of a GE logic 9 machine) to examine liver morphology, portal vein diameter, ascites, and splenomegaly.
Arterial blood gas analysis was obtained by puncture of radial artery and then analyzed using the blood gas analyzer.
The diagnosis of porto pulmonary hypertention was based on the bedside cardiological assessment and confirmed by previous patients echocardiogram reports ,defined as mean pulmonary artery pressure more than 25 mm Hg at rest and more than 30 mmHg during excercise in patients with coexisting portal hypertention Pulmonary artery systolic pressure (PASP) was measured by echocardiogram using a simplified Bernoulli equation.
Portal hypertension was suspected clinically by the presence of splenomegaly, ascites, and/or abdominal wall collaterals and confirmed radiologically by Doppler ultrasound to demonstrate the presence of collateral vessels, alterations in portal venous flow, splenomegaly, and ascites, thereby supporting the diagnosis of portal hypertension.
All patients were closely monitored. ECG, SpO2, arterial blood pressure, and respiratory rate, were continuously monitored by electronic monitors. Body temperature and urine output were checked. Central venous pressure was assessed every 1 h. Arterial blood gases were measured every 8 h. Chest radiography, static, and dynamic compliance were repeated every 24 h.
End points of the study included duration of mechanical ventilation, and ICU stay, mortality rates, need for vasopressor support, and sedation and the appearance of any form of barotrauma (pneumothorax, pneumopericardium, pneumomediastinum, pneumoperitoneum, or subcutaneous emphysema).
Successful weaning off mechanical ventilation was started upon the presence of spontaneous breathing on room air with oxygen saturation 93% or more without signs of respiratory distress for more than or equal to 48 h.
All the data collected were entered, tabulated, and statistically analyzed using statistical program for social science, version 20.0.Qualitative data were expressed as frequency and percentage whereas quantitative data were expressed as mean±SD. One-way analysis of variance was used to compare between more than two means, whereas independent sample t test was used to compare between two means. χ2 test was used to compare proportions between two qualitative parameters. P value less than 0.05 was considered statistically significant.
| Results|| |
In the study, 80 patients were included in the final analysis, with 40 in each group. The baseline characteristics of patients including age and sex showed no significant statistical difference ([Table 1] and [Table 2]).
The postventilatory data were compared 3 days after starting the mechanical ventilation. There was a statistically significant difference between group PV and group S during the mechanical ventilation period regarding the PO2/FiO2 ratio, static compliance, and dynamic compliance values, with higher values in group PV than group S, providing better oxygenation ([Table 3],[Table 4],[Table 5]).
|Table 3 Comparison between the two groups according to preventilatory and postventilatory PO2/FiO2 ratio|
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|Table 4 Comparison between the two groups according the dynamic compliance values|
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|Table 5 Comparison between the two groups according the static compliance values|
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However, there was no statistical significance between the two groups regarding the PCO2 values ([Table 6]).
Moreover, there was no statistical significance between the two groups according to the need for vasopressor support ([Table 7]).
There was a statistically significant difference between the two groups regarding the need for intravenous sedation, with more in the S group than in the PV group ([Table 8]).
|Table 8 Need for sedation during mechanical ventilation in the two groups|
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There was a statistically significant difference in the duration of mechanical ventilation and the ICU stay between the two groups, with significantly lower values in the PV group than the S group, as shown in [Table 9] and [Table 10].
|Table 9 Comparison between the two groups regarding the mechanical ventilation duration in days|
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|Table 10 Comparison between the two groups regarding the ICU stay in days|
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There was no statistically significant difference between both groups regarding the occurrence of complications of mechanical ventilation, as shown in [Table 11].
|Table 11 Comparison between the two groups regarding complications during mechanical ventilation|
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There was no statistically significant difference between the two groups regarding the mortality during the study, as shown in [Table 12].
| Discussion|| |
Abnormalities in pulmonary function and impaired gas exchange may occur in as many as 45–50% of patients with advanced liver disease in the absence of cardiopulmonary disease. Although mechanisms of hypoxemia include an intra or extrapulmonary shunt, ventilation–perfusion, and alveolar capillary diffusion abnormalities, there is a lack of agreement on which factors are most important.
Several studies were performed over the past few years trying to maximize the benefit and minimize the harm from mechanical ventilation in this category of patients, as the most important parameter for the clinician early during mechanical ventilation is choosing a suitable mode for the patient . Modes of mechanical ventilation differ markedly between each other regarding their mechanism of generating positive pressure within the patient lungs with many subsequent effects .
This study was performed to compare the effects of SIMV and PRVC ventilation on patients with advanced liver disease having acute respiratory failure, irrespective of cause. It aimed to evaluate the role of each of the two modes on the pulmonary gas exchange and patient hemodynamics. It also compares the effects of both modes on the duration of mechanical ventilation days and ICU stay, thus predicting the superiority of each over the other during the management of respiratory failure.
No statistically significant difference between the two groups regarding their demographic data, namely, age and sex, was found. Group S had 40 patients (24 males and 16 females) with mean age of 37.45±3.67 years, whereas group PV also consisted of 40 patients (27 males and 13 females), with mean age of 38.12±3.29 years.
In this study, a statistically significant difference between the two groups in oxygenation was found, with a P value less than 0.001. OI or hypoxic index was used as a measure of oxygenation with the PV group showing higher values of PO2/FiO2 ratio, implying better oxygenation than the S group.
Our results are similar to the results obtained by Samantaray and Hemanth  who compared pressure-controlled ventilation to pressure-regulated volume targeted ventilation in postcardiac surgical patients. They found PRVC provided better oxygenation in the form of higher OI which they attributed to better ventilation of atelectatic areas of the lungs and through the guaranteed volume provided with lower mean airway pressure.
However, these results are different from those obtained by Guldager et al.  in which PRVC did not improve oxygenation when compared with volume controlled ventilation (VCV) in the management of acute respiratory failure, despite a statistically significant difference in peak pressures in mild respiratory failure patients, which was their primary aim.
Kocis et al.  compared PRVC with VCV in postcardiac surgical infants undergoing correction of congenital heart disease. They found that PRVC only provided significantly lower levels of peak inspiratory pressure but failed to improve oxygenation.
Song et al.  on comparing VCV to PRVC during one lung ventilation found that PRVC provided higher tidal volume at a lower pressure inspiratory pressure (PIP) and increased PaO2 in 63% of patients. The study found PRVC provided higher exhaled tidal volume, and oxygenation improved in 66% of patients.
Our study found comparable alveolar ventilation between the two groups, where group S showed a mean PCO2 of 51.29±5.78, whereas group PV had a mean of 49.77±4.33, with P value of 0.187.
However, different results were found by Ali et al. . In their study, they found that PRVC did in fact reduce PaCO2 and hence improved alveolar ventilation when compared with SIMV mode in patients with chronic obstructive pulmonary disease having acute respiratory failure. Similarly, Chang et al.  found marked improvement in alveolar ventilation and statistically significant reductions in PaCO2 when they compared PRVC with SIMV mode in elderly patients having acute respiratory failure, resulting from acute exacerbations of chronic obstructive pulmonary disease.
This study revealed highly statistically significant rise in both the static and dynamic compliance in the PV group when compared with the S group, with P value less than 0.001 denoting ventilation at a lower pulmonary pressure.
Dion et al.  compared VCV, Pressure controlled ventilation (PCV), and PRVC for ventilation during laparoscopic bariatric surgery. This study measured the parameters of airway pressure, exhaled tidal volume, respiratory rate, ventilation, and oxygenation by ventilation mode. Compliance was not their primary point of study. They found variations in exhaled tidal volumes in various stages of the surgery, and it was favorably managed with PRVC. Lung compliance was better in the PRVC group of patients when compared with the PCV group. However, both groups had better statistically significant pulmonary compliance when compared with the VCV group.
Moreover, Song et al.  found significant reductions in the pulmonary compliance when they compared VCV with PRVC during one lung ventilation in favor of the PRVC group.
Our results revealed that there was no statistically significant difference between the two groups regarding the need for vasopressor support or the need for sedation.In agreement with our results, Gang et al.  found no significant difference or advantage regarding hemodynamics when comparing PRVC with SIMV in acute lung injury.
In 2016, different findings were obtained by Aghadavoudi et al.  in their study that compared the hemodynamic and respiratory effects of PRVC and SIMV. They found better hemodynamic stability with less sympathetic stimulation in the PRVC group.
This study revealed shorter duration of mechanical ventilation days and ICU stay in the PV group than the S group, with statistically significant P value of less than 0.001 for both variables.
Mechanical ventilation days in the PV group had a mean of 3.97±1.57 days, whereas in the S group had a mean of 7.15±1.24 days. ICU stay in the PV group had a mean of 5.87±1.36 days, whereas in the S group had a mean of 12.22±1.08 days.
No statistical significance difference was found in our study between the two modes of mechanical ventilation with respect to occurrence of complications of mechanical ventilation.
Wang et al.  obtained different results in their work of systemic review and network meta-analysis comparing 16 modes of mechanical ventilation in ARDS. They found that compared with SIMV mode, volume-guarantee modes were associated with significantly lower mortality rates.
Limitations of the present study
The outcomes of this study have not been adjusted for some confounders, such as the degree of severity and comorbidities associated with the advanced liver disease. Another point that can be criticized in the current study is that, apart from PO2/FiO2 ratio, the preventilation values were not presented. Actually, all our patients presented with acute respiratory failure on top of advanced liver disease, and there was no chance to measure other preventilation parameters.
Our results needed to be confirmed in larger study population. Future studies should compare PRVC mode with newer modes of mechanical ventilation, like airway pressure release ventilation and biphasic positive airway pressure (BIPAP) modes for management of respiratory failure and ARDS.
| Conclusion|| |
Finally, it can be concluded that PRVC mode of mechanical ventilation is superior to SIMV in acute respiratory failure complicating advanced liver disease, as it resulted in improved oxygenation at lower inflation pressures.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10], [Table 11], [Table 12], [Table 4]EgyptJCardiothoracAnesth_2018_12_3_35_258996_t13.jpg, [Table 5]EgyptJCardiothoracAnesth_2018_12_3_35_258996_t14.jpg, [Table 5]EgyptJCardiothoracAnesth_2018_12_3_35_258996_t15.jpg