EFFECTS OF PRESSURE-CONTROLLED AND VOLUME-CONTROLLED VENTILATION ON HEMODYNAMIC AND RESPIRATORY PARAMETERS IN PATIENTS DURING LAPAROSCOPIC CHOLECYSTECTOMY.
General anesthesia causes decline in vital lung capacity, functional residual capacity and lung compliance, especially during laparoscopic cholecystectomy due to patient positioning (Trendelenburg position) and creation of pneumoperitoneum, which causes increased intra-abdominal and intrathoracic pressure. This can lead to repeated closure of small airways and occurrence of atelectases. The majority of otherwise healthy patients are capable to successfully compensate for these changes, but obese patients and those with chronic respiratory diseases are susceptible to development of numerous complications such as intraoperative hypoxia, barotrauma and volutrauma during laparoscopic procedures (1).
In addition, in recent years, many papers have been published investigating the effects of intraoperative mechanical ventilation on the incidence of perioperative and postoperative respiratory complications (2). Alveolar collapse can be prevented by applying continuous positive end-expiratory pressure and tidal volume should be decreased to limit pulmonary overdistention. This concept is known as protective mechanical ventilation and is now used in the treatment of respiratory disorders requiring mechanical ventilation (3). By using protective volume- or pressure-controlled mechanical ventilation, it is possible to optimize respiratory and hemodynamic functions during surgery (4).
Volume-controlled ventilation (VCV) is considered to be the most popular mode for intraoperative use. It is a mode of ventilation controlled by tidal volume and respiratory frequency as constant parameters, with variable inspiratory pressures. Although popular, VCV is not without drawbacks because high peak pressures (Ppeak) can sometimes force anesthesiologists to change the preset tidal volume and frequency values.
Pressure-controlled ventilation (PCV) has inspiratory pressure and respiratory frequency as constant parameters, while the tidal volume achieved depends on lung compliance and resistance. Decelerating inspiratory flow pattern in PCV ventilation is associated with a lower incidence of airway barotrauma with high peak pressures, while the increased mean inspiratory pressure (Pmean) has positive effects on oxygenation. However, tidal volume can vary greatly during surgery.
The aim of this clinical trial was to compare the effects of the VCV and PCV protective modes of mechanical ventilation on pulmonary mechanics, gas exchange, and hemodynamic parameters of patients during laparoscopic cholecystectomy.
Patients and Methods
The study included 60 patients aged between 18 and 70, with the American Society of Anesthesiologists (ASA) physical status 1-3 and body mass index (BMI) <35 kg/[m.sup.2], who were scheduled for laparoscopic cholecystectomy under general anesthesia at the Mostar University Hospital. All patients were without prior history of chronic respiratory diseases. Exclusion criteria were intraoperative usage of an airway device other than tracheal tube and a requirement for mechanical ventilation in the postoperative period.
Patients were assigned randomly to two groups, VCV or PCV, using pre-sealed opaque envelopes prepared and drawn by an independent observer. Patients assigned to the first group were ventilated with protective VCV with tidal volume set at 7 mL/kg. In the second, PCV group, the ventilator was adjusted so that the preset pressure attained the desired tidal volume of 7 mL/kg with a variation of 5%. The ratio of inspiratory to expiratory time (1:2), fraction of inspired oxygen FIO2 (0.4) and positive end-expiratory pressure of 7 cm [H.sub.2]O were the same in both groups. Variations in respiratory rate were allowed to maintain the values of end-tidal carbon dioxide in a range of 28-40 mm Hg.
Induction in general anesthesia consisted of midazolam 0.04 mg/kg, followed by fentanyl 1 [micro]g/kg, propofol 1-2 mg/kg until adequate depth of anesthesia achieved bispectral index (BIS) score [less than or equal to]60. Tracheal intubation was performed after administration of 0.4 mg/kg atracurium. Anesthesia was maintained with a mixture of O2 (40%) and N2O (60%), along with minimal alveolar concentration (MAC) sevoflurane =1. Intravenous fluids in the form of 0.9% NaCl, 20 mL/min were administered.
During surgery, the abdominal cavity was insufflated with CO2 with patients in the supine position, to maximum intra-abdominal pressure of 12 mm Hg, and then patients were tilted in anti-Trendelenburg position by 20[degrees] and the same position was maintained throughout the procedure.
We recorded heart rate (HR), mean arterial pressure (MAP) and arterial oxygen saturation (SaO2) at 4 time intervals: before induction of general anesthesia (baseline measurements), and at 15, 30 and 45 minutes after tracheal intubation. We also recorded end-tidal CO2, Ppeak and Pmean inspiratory pressure at 3 time intervals: at 15, 30 and 45 minutes after tracheal intubation.
Drager Primus (Dragerwerk AG & Co. KGaA, Lubeck, Germany) was used as anesthesia workstation. All patients were continuously monitored using electrocardiography (ECG), pulse oximetry and noninvasive arterial pressure (Drager Infinity Delta monitor, Dragerwerk AG & Co. KGaA, Lubeck, Germany). BIS was used to monitor the level of consciousness (BIS technology, Aspect Medical Systems, Meern, The Netherlands).
Data analysis was performed using SPSS for Windows (version 17.0, SPSS Inc., Chicago, Illinois, SAD). Results were expressed as mean and standard deviation (M [+ or -] SD). T-test for independent samples was used to test statistically significant differences between the groups. The level of p<0.05 was considered significant. The results were first presented by comparing original groups of 30 patients regardless of body mass and then we compared only patients with BMI >25 in each group. All patients were informed about the nature of the study and data to be collected. All patients signed an informed consent.
The two groups were well matched according to patient characteristics (gender, age and BMI) and baseline data (Table 1). Table 2 shows the values of HR, MAP, Ppeak and plateau inspiratory pressure (Pplateau), end-tidal CO2 and SaO2 recorded at three time intervals. There were no major differences in the values of lung mechanics, gas exchange and hemodynamic parameters between the groups. The only significant yet not statistically significant (p=0.065) difference was found in Pmean 15 min after tracheal intubation, which was higher in the PCV group of patients. When we compared patients with BMI >25 (Table 3), we found significantly higher Ppeak at all time intervals (T1, T2 and T3) in the VCV group. Other measured parameters were of similar characteristics.
Because of the widespread prevalence of laparoscopic surgeries and the specific conditions they create in human body (development of pneumoperitoneum with negative effects on respiratory mechanics), it is extremely important to find an appropriate mode of mechanical ventilation for this type of surgery.
In this study, we decided to include all patients regardless of body weight or existing chronic diseases, with the history of chronic respiratory diseases as the only exception. Doing so, we hoped to get a representative sample that could be applied to almost the entire population, in contrast to the studies that targeted strictly specific groups of patients (1,5,6).
In addition to studies involving laparoscopic abdominal surgery, PCV was the subject of research in thoracic surgery as well (8-12). In all of these studies, PCV has been reported to be more or less superior to VCV. The results recorded in our study showed no significant benefits of PCV over VCV (Table 2), but revealed no shortcomings either. MAP was slightly higher in the PCV group at all three time intervals (T1, T2 and T3), but the difference was not statistically significant. On the other hand, HR was continuously higher in VCV, but without statistical significance, which was consistent with the findings reported in other studies. Creating a pneumoperitoneum can cause hemodynamic changes, which according to Mercat et al. (13) are potentiated by higher mean inspiratory pressure of PCV. However, we observed no significant differences, which according to Balick-Weber et al. (14) could be due to the small magnitude of those changes. Respiratory parameters measured in this study showed no significant differences either. Ppeak and end-tidal CO2 concentration were slightly higher in the VCV group at all three measurements, whereas Pplateau was higher in the PCV group. These results are somewhat different from the study by Tyagi et al., which addressed the same topic (4). The measured SaO2 varied among intervals and these results were not quite in line with the analysis of other authors (5), especially when it comes to specific groups of patients (1). The values of all these parameters were within the normal range.
Given that CO2 insufflation into the abdominal cavity (creation of pneumoperitoneum) leads to caudal displacement of the diaphragm, lowers functional residual capacity and lung compliance, and increases resistance of the lung tissue, which is especially pronounced in obese and those with chronic respiratory diseases, we decided to establish a subgroup of patients with BMI >25 kg/[m.sup.2] and compare their data as well (Table 3). The patients with BMI >25 kg/[m.sup.2] are particularly interesting in this case because obesity is associated with reduced functional residual capacity of the lungs, lung compliance and oxygenation index, while increasing the overall resistance of the respiratory system (16).
When we included the above criterion (BMI >25 kg/[m.sup.2]), 19 patients remained in PCV group and 12 patients in VCV group. Hemodynamic parameters remained without significant changes. There was slightly higher HR on all three measurements in VCV group and higher MAP in PCV group, with almost identical dynamics in comparison with the original groups. Accordingly, there were no significant effects of pressure or volume ventilation on hemodynamic parameters in obese patients, which is consistent with the existing literature (6,16,18-19).
Comparing respiratory parameters, we found that Ppeak was significantly higher in VCV group, especially on T2 and T3 measurements (p[less than or equal to]0.01). This is important because lower inspiratory pressures have a favorable effect on patient hemodynamics and reduce the incidence of barotrauma (13). It should be noted that most authors state just this variable as one of the main strengths of PCV (1,4,5,7,17,19), although there are examples in the literature that deny this advantage (14,16,18). Pplateau was also, although not significantly lower in PCV group at all three measurements, and it is inconsistent with the findings obtained in the initial processing of data which involved all patients regardless of BMI. Although available studies do not indicate statistically significant differences in Pplateau values (5,14), the dynamics obtained here raises the question of whether the results are just a matter of pure coincidence or there really is a link with BMI values. According to these results, we can theorize that the increase in BMI leads to lower Ppeak and possibly Pplateau values with PCV, which is somewhat different compared to similar studies.
End-tidal CO2 (etCO2) results showed similar dynamics. In the original groups, etCO2 was slightly lower, but not significantly, in the PCV group at all measuring intervals, and a comparable pattern was also recorded in the groups with BMI >25 kg/[m.sup.2]. Yet, it should be noted that the difference between the observed groups increased without reaching statistical significance. Some authors confirmed lower etCO2 values in PCV patients (1), although there are studies in which there was no significant difference (5,7,12,19) and studies that favor VCV (18).
Arterial oxygen saturation measured by pulse oximetry showed no significant between-group difference. It was to be expected, since all patients were without previous history of chronic respiratory diseases, with good preoperative values. Also, most previous studies found no significant differences either (1,18,19). The only exception to the above is the study by Lin et al., who report on better intraoperative and postoperative oxygenation with PCV in elderly patients with poor pulmonary function (11).
Based on the results, we conclude that PCV and VCV were equally effective in maintaining adequate ventilation, oxygenation and hemodynamic stability in the study groups of patients. However, comparison of obese patients (BMI >25) showed particular advantages of PCV (lower peak pressure, lower end-tidal C[O.sub.2]) which, given the present pace of change, should be additionally investigated. It would also be interesting to see how chronic respiratory diseases affect this issue, which, we believe, is still insufficiently investigated.
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(4.) Tyagi A, Kumar R, Sethi AK, Mohta M. A comparison of pressure-controlled and volume-controlled ventilation for laparoscopic cholecystectomy. Anaesthesia. 2011;66:503-8, doi:10.1111/j.1365-2044.2011.06713.x.
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UTJECAJI TLAKOM I VOLUMENOM KONTROLIRANE STROJNE VENTILACIJE NA HEMODINAMSKE I RESPIRACIJSKE PARAMETRE BOLESNIKA TIJEKOM LAPAROSKOPSKE KOLECISTEKTOMIJE
M. Mihalj, D. Vladic, Z. Karlovic, Z. Zadro i V. Majeric Kogler
Ucinak intraoperacijske strojne ventilacije na pojavu poslijeoperacijskih plucnih komplikacija se intenzivno istrazuje posljednjih nekoliko godina. Potencijalne prednosti tlacno kontrolirane (PCV) u odnosu na volumnu (VCV) strojnu ventilaciju tijekom laparoskopskih operacija jos uvijek nisu u potpunosti dokazane. U istrazivanje je bilo ukljuceno 60 bolesnika u dobi od 18 do 70 godina, planiranih za laparoskopsko odstranjenje zucnog mjehura. Svi bolesnici su imali indeks tjelesne mase [less than or equal to]35, ASA I.-III., bez povijesti kronicnih respiracijskih bolesti. Slucajnim su odabirom podijeljeni u skupine s tlacnom odnosno volumnom ventilacijom. Dobiveni rezultati nisu pokazali znacajnih razlika u respiracijskim i hemodinamskim parametrima izmedu skupina. Kada su izdvojeni i usporedeni bolesnici s indeksom tjelesne mase [greater than or equal to]25 zabiljezen je znacajno nizi vrsni tlak u bolesnika s tlacno kontroliranom ventilacijom u 15. (18,52 prema 21,83 cm H2O, p=0,022), 30. (18,73 prema 21,83 cm H2O, p=0,009) i 45. (18,94 prema 22,667 cm H2O, p=0,010) minuti nakon trahealne intubacije. Ostale vrijednosti su bile bez statisticke znacajnosti. Moze se zakljuciti da izmedu PCV i VCV ne postoje znacajnije razlike u odrzavanju odgovarajuce ventilacije i oksigenacije bolesnika te hemodinamske stabilnosti u promatranim skupinama bolesnika. Medutim, usporedba bolesnika s prekomjernom tjelesnom tezinom je pokazala odredene prednosti PCV-a koje bi s obzirom na prisutnu dinamiku promjena trebalo podrobnije istraziti.
Kljucne rijeci: Respiracija, umjetna; Laparoskopija; Anestezija, opca; Intubacija, endotrahealna; Respiracija; Pretilost; Prikazi slucaja
Mirko Mihalj (1), Dajana Vladic (1), Zoran Karlovic (1), Zeljka Zadro (1) and Visnja Majeric Kogler (2)
(1) Mostar University Hospital, Department of Anesthesia, Resuscitation and Intensive Care, Mostar, Bosnia and Herzegovina; (2) University of Zagreb, School of Medicine, Zagreb, Croatia
Correspondence to: Mirko Mihalj, MD, Mostar University Hospital, Department of Anesthesia, Resuscitation and Intensive Care, Kneza Trpimira 14, Mostar, Bosnia and Herzegovina E-mail: email@example.com
Received January 11, 2016, accepted October 24, 2016
Table 1. Patient characteristics and baseline data PCV VCV (n=30) (n=30) Age (years) 44[+ or -]14 48[+ or -]14 Gender: male 15 15 female 15 15 Weight (kg) 81[+ or -]13 78[+ or -]16 Height (cm) 175[+ or -]11 174[+ or -]9 BMI (kg/[m.sup.2]) 26[+ or -]3 25[+ or -]4 HR (beats/min) 84[+ or -]15 85[+ or -]14 MAP (mm Hg) 108[+ or -]14 107[+ or -]12 SpO2 (%) 98[+ or -]1 98[+ or -]1 Values are mean [+ or -] standard deviation (SD); HR = heart rate; MAP = mean arterial pressure; PCV = pressure-controlled mechanical ventilation; VCV = volume-controlled mechanical ventilation; BMI = body mass index; SpO2 = arterial oxygen saturation Table 2. Hemodynamic and respiratory data recorded at three time intervals: T1--15 minutes after tracheal intubation; T2--30 minutes after tracheal intubation; and T3--45 minutes after tracheal intubation T1 T2 PCV VCV PCV (n=30) (n=30) (n=30) HR (beats/min) 77[+ or -]16 78[+ or -]17 73[+ or -]13 MAP (mm Hg) 97[+ or -]15 91[+ or -]10 103[+ or -]14 Ppeak (cm [H.sub.2]O) 17[+ or -]3 18[+ or -]4 17[+ or -]3 Pplateau (cm [H.sub.2]O) 16[+ or -]4 16[+ or -]3 17[+ or -]4 etCO2 (mm Hg) 32[+ or -]3 33[+ or -]3 32[+ or -]3 SpO2 (%) 99[+ or -]1 99[+ or -]1 99[+ or -]1 T3 VCV PCV VCV (n=30) (n=30) (n=30) HR (beats/min) 78[+ or -]12 72[+ or -]13 76[+ or -]11 MAP (mm Hg) 100[+ or -]16 100[+ or -]15 98[+ or -]12 Ppeak (cm [H.sub.2]O) 18[+ or -]4 17[+ or -]4 18[+ or -]4 Pplateau (cm [H.sub.2]O) 16[+ or -]4 17[+ or -]4 16[+ or -]4 etCO2 (mm Hg) 33[+ or -]4 32[+ or -]3 32[+ or -]4 SpO2 (%) 99[+ or -]1 99[+ or -]1 99[+ or -]1 Values are shown as mean [+ or -] standard deviation (SD); PCV = pressure-controlled mechanical ventilation; VCV = volume-controlled mechanical ventilation; HR = heart rate; MAP = mean arterial pressure; Ppeak = peak inspiratory pressure; Pplateau = plateau inspiratory pressure; etCO2 = end-tidal CO2; SpO2 = arterial oxygen saturation Table 3. Hemodynamic and respiratory data of patients with BMI >25 obtained at three time intervals: T1--15 minutes after tracheal intubation; T2--30 minutes after tracheal intubation; and T3--45 minutes after tracheal intubation T1 T2 PCV VCV PCV (n=30) (n=30) (n=30) HR, (beats/min) 76[+ or -]15 79[+ or -]16 73[+ or -]14 MAP (mm Hg) 98[+ or -]17 93[+ or -]12 103[+ or -]13 Ppeak (cm [H.sub.2]O) 18[+ or -]4 21[+ or -]3 (*) 18[+ or -]4 Pplateau (cm [H.sub.2]O) 18[+ or -]4 19[+ or -]2 18[+ or -]4 etCO2 (mm Hg) 31[+ or -]2 32[+ or -]4 30[+ or -]2 SpO2 (%) 99[+ or -]1 99[+ or -]1 99[+ or -]1 T3 VCV PCV (n=30) (n=30) HR, (beats/min) 78[+ or -]11 72[+ or -]14 MAP (mm Hg) 106[+ or -]20 102[+ or -]13 Ppeak (cm [H.sub.2]O) 22[+ or -]2 (*) 19[+ or -]4 Pplateau (cm [H.sub.2]O) 20[+ or -]3 18[+ or -]4 etCO2 (mm Hg) 32[+ or -]4 30[+ or -]2 SpO2 (%) 99[+ or -]1 99[+ or -]1 VCV (n=30) HR, (beats/min) 75[+ or -]10 MAP (mm Hg) 99[+ or -]11 Ppeak (cm [H.sub.2]O) 22[+ or -]2 (*) Pplateau (cm [H.sub.2]O) 20[+ or -]2 etCO2 (mm Hg) 31[+ or -]4 SpO2 (%) 99[+ or -]1 Values are shown as mean [+ or -] standard deviation (SD); PCV = pressure-controlled mechanical ventilation; VCV = volume-controlled mechanical ventilation; HR = heart rate; MAP = mean arterial pressure; Ppeak = peak inspiratory pressure; Pplateau = plateau inspiratory pressure; etCO2 = end-tidal CO2; SpO2 = arterial oxygen saturation; (*) statistically significant differences between the groups
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|Title Annotation:||Case Report|
|Author:||Mihalj, Mirko; Vladic, Dajana; Karlovic, Zoran; Zadro, Zeljka; Kogler, Visnja Majeric|
|Publication:||Acta Clinica Croatica|
|Date:||Sep 1, 2017|
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