Patient effort at a glance

A: Patient with little effort. Top: Volume Controlled Ventilation: airway pressure in cmH2O in yellow, constant flow in L/min in pink. Middle: Pressure controlled ventilation: airway pressure in cmH2O in yellow, decelerating flow in L/min in pink. Bottom: Esophageal pressure in cmH2O. B: Patient with high effort. Top: Volume Controlled Ventilation: airway pressure with convex negative deflection during trigger and first half of inspiration (blue arrow). Middle: Pressure controlled ventilation: airway pressure with negative deflection during the trigger (yellow arrow) and slight convex deflection (green arrow), concave deflection in the flow (orange arrow). Bottom: Convex deflection in esophageal pressure (grey arrow).

Different Inspiratory Flow Waveform during Volume-Controlled Ventilation in ARDS Patients

The most used types of mechanical ventilation are volume- and pressure-controlled ventilation, respectively characterized by a square and a decelerating flow waveform. Nowadays, the clinical utility of different inspiratory flow waveforms remains unclear. The aim of this study was to assess the effects of four different inspiratory flow waveforms in ARDS patients. Twenty-eight ARDS patients (PaO2/FiO2 182 ± 40 and PEEP 11.3 ± 2.5 cmH2O) were ventilated in volume-controlled ventilation with four inspiratory flow waveforms: square (SQ), decelerating (DE), sinusoidal (SIN), and trunk descending (TDE). After 30 min in each condition, partitioned respiratory mechanics and gas exchange were collected. The inspiratory peak flow was higher in the DE waveform compared to the other three waveforms, and in SIN compared to the SQ and TDE waveforms, respectively. The mean inspiratory flow was higher in the DE and SIN waveforms compared with TDE and SQ. The inspiratory peak pressure was higher in the SIN and SQ compared to the TDE waveform. Partitioned elastance was similar in the four groups; mechanical power was lower in the TDE waveform, while PaCO2 in DE. No major effect on oxygenation was found. The explored flow waveforms did not provide relevant changes in oxygenation and respiratory mechanics.

Effect of Mechanical Ventilation Mode Type on Prioperative Blood Loss in Patients Undergoing Posterior Lumbar Inter body Fusion Surgery: A Randomized Controlled Trial

Background this study has examined modes of mechanical ventilation, pressure or volume-controlled ventilation (PCV or VCV) on intra- and post-operative surgical bleeding in posterior lumbar inter body fusion (PLIF) surgery Methods This research was a randomized, single-blinded, and parallel study, that 78 patients were selected. They mechanically ventilated using either PCV or VCV in PLIF surgery. In this regard, a permuted block randomization was used with a computer-generated list. After induction of anesthesia in supine position, the hemodynamic and respiratory parameters were measured Results The mean bleeding was 431.281 ± 361.04cc in the PCV group and 465.26 ± 338.16 cc in the VCV group (p = 0.669). Moreover, blood transfusion rates in the PCV and VCV groups were 0.40 ± 0.74 and 0.43±78 0.78 pack cell (p = 0.836), respectively. Notably, surgeon satisfaction was more observed in the PCV group (82.1% vs. 74.4%, p = 0.548). In addition, the other variables were similar in these two groups. Conclusions The mean bleeding volume was higher in the VCV group compared to the PCV group; however, no significant difference was observed between these two groups. Hemoglobin levels in the patients included before and after surgery showed that the two groups were in a similar condition.

Effects of pressure- and volume-controlled ventilation on the work of breathing in cats using a cuffed endotracheal tube

Background and Aim: Mechanical ventilation is essential for supporting patients' respiratory function when they are under general anesthesia. For cats with limited lung capacity, the different effects of volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) on respiratory function remain elusive. The objective of the present study was to compare the efficacy of VCV and PCV in cats under general anesthesia using a cuffed endotracheal tube (ETT). Materials and Methods: Twelve healthy cats were randomly allocated to either a VCV or PCV group. Five tidal volumes (6, 8, 10, 12, and 14 mL/kg) were randomly applied to assess the efficacy of VCV, and respiratory rates were adjusted to achieve a minute ventilation of 100 mL/kg/min. Peak inspiratory pressures (4, 5, 6, 7, and 8 mmHg) were randomly applied to assess the efficacy of PCV, and respiratory rates were adjusted to achieve a minute ventilation of 100 mL/kg/min. Blood pressure, gas leakages, and end-tidal CO2 were recorded from 60 trials for airway control during the use of VCV or PCV. Data were compared using Fisher's exact test with a significance level of p<0.05. Results: Leakages did not differ between VCV (1/60 events) and PCV (0/60 events; p=0.500). Hypercapnia was identified when using VCV (6/60 events) less frequently than when using PCV (7/60 events; p=0.762), but did not reach statistical significance. Hypotension (mean arterial blood pressure <60 mmHg) occurred less frequently with VCV (0/60 events) than with PCV (9/60 events; p=0.003). Moreover, VCV provided a significantly lower work of breathing (151.10±65.40 cmH2O mL) compared with PCV (187.84±89.72 cmH2O mL; p<0.05). Conclusion: VCV in cats using a cuffed ETT causes less hypotension than PCV. It should be noted that VCV provides a more stable tidal volume compared with PCV, resulting in a more stable minute volume. Nonetheless, VCV should not be used in patients with an airway obstruction because higher peak airway pressure may occur and lead to lung injury.

COMPARATIVE ANALYSIS OF PRESSURE CONTROLLED AND VOLUME CONTROLLED VENTILATION ON RESPIRATORY MECHANICS, HAEMODYNAMICS AND SYSTEMIC STRESS RESPONSE IN PATIENTS UNDERGOING SURGERY IN PRONE POSITION.

BACKGROUND: General Anaesthesia in prone position is related with increased airway pressure, decreased pulmonary and thoracic compliance. AIM: Comparision of pressure controlled and volume controlled ventilation in patients undergoing lumbar spine surgery in prone position.METHODS: After ethics committee approval & written informed consent, a comparative randomized interventional study was conducted from July-December 2017. Randomization was done using random number tables. Patients of either sex, ASA grade I&II, age 25-55 yrs were included while those with severe pulmonary ,cardiovascular, endocrine disease & BMI> 30kg/m2 were excluded. Patients were randomly assigned to VCV group (n = 30), or PCV group (n = 30). Haemodynamic (HR,SBP,DBP,MAP), Respiratory (P-Peak,P-mean,C-dyn) variables,blood glucose,S.cortisol were measured and ABG analysis was done 10 minutes after intubation (T1), 30 minutes after prone positioning(T2) and 60 minuts after extubation(T3). RESULTS: Demographic parameters , perioperative hemodynamic values were comparable with no significant statistical difference.The P-Peak levels were lower and dynamic compliance was higher in PCV group during both T1 and T2 with p value of less than 0.05 Postoperative PaO2 level was significantly higher in Group PCV compared with Group VCV.The difference between post operative and preoperative serum cortisol and blood glucose levels was significantly less in patients ventilated with PCV mode.CONCLUSION: According to our study,PCV mode is associated with lower P-peak levels during prone position, better oxygenation postoperatively and lesser systemic stress response.We concluded that PCV mode might be more appropriate in prone position surgeries.

Comparison of the effects of volume-controlled ventilation and pressure-controlled ventilation modes on hemodynamics, respiratory mechanics and blood gas parameters in patients undergoing laparoscopic cholecystectomy

Background: This study aimed to compare the changes induced by VCV and PCV modes in hemodynamics, respiration (airway pressures, gas exchange parameters) and metabolism (acid-base balance) in patients undergoing laparoscopic cholecystectomy.Methods: Patients were divided into two randomised groups as volume-controlled ventilation (VCV) group (VC) and pressure-controlled ventilation (PCV) group (PC). The following parameters were recorded at 3 different time points: T1: in supine position 10 minutes after induction of anaesthesia, T2: 15 minutes after CO2 insufflation in inverted Trendelenburg position (head 30 degrees up), T3: 10 minutes after CO2 desufflation. HR, SpO2, SAP (systolic arterial pressure), DAP (diastolic arterial pressure), MAP (mean arterial pressure), PetCO2 (end-tidal carbon dioxide pressure), Ppeak, Pplateau, Pmean, Vt (tidal volume) and compliance with the available data, the cases in both groups Vd, Vd/Vt ratios and P(A-a)O2 were calculated. Arterial blood gas parameters (pH, PaO2, PaCO2, SaO2, P(a-et)CO2) values were recorded.Results: It was found that Ppeak and Pplateau values were significantly higher in the VC group (p<0.05). It was found that compliance was significantly higher in the PC group (p<0.05) (p<0.01). In the postoperative period, it was found that PaO2 values were significantly higher in the PC group compared to the VC group (p<0.05). It was found that the P(A-a)O2 values of the PC group were significantly higher than those of the VC group during the desufflation phase (p<0.05).Conclusions: We think that PCV mode can be a good alternative for the prevention and correction of physiopathological changes due to laparoscopic surgery.

Evaluation and Characteristic of Modified Ventilator Under Hyperbaric Conditions During Volume-controlled Ventilation

Purpose：The stability of the modified ventilator (Shangrila590, Beijing Aeonmed Company, Beijing, China) was evaluated under hyperbaric conditions during volume-controlled ventilation in this study by Michigan test lung (5601i, Grand Rapids, MI, US).Methods：Experiments were performed inside the multiplace hyperbaric chamber at 1.0, 1.5 and 2.0 atmospheres absolute (ATA). The modified ventilator placed inside the hyperbaric chamber was connected to the test lung. During volume-controlled ventilation (VCV), data for the test lung were collected by a personal computer outside the hyperbaric chamber. The preset tide volume (VTset) of the ventilator (400-1000 ml) and the resistance and compliance of the testing lung were adjusted before the experiments at every ambient pressure. With every test setting, the tide volume (VT), inspiratory airway peak pressure (Ppeak) and minute volume (MV) displayed by the ventilator and the test lung were recorded by the computer. We compared the ventilator and test lung data under 1.0, 1.5 and 2.0 ATA to evaluate the stability of the modified ventilator.Results：The variation in VT in the test lung and the ventilator at different ambient pressures changed within a narrow range, and the differences were statistically significant. In every test setting, changes in the MV of the ventilator were limited and acceptable, with significant differences at different ambient pressures. However, Ppeak increased obviously, as detected by the ventilator and test lung at higher ambient pressure during VCV.Conclusions：The modified Shangrila590 ventilator can work well in a hyperbaric chamber. It can provide relatively stable VT and MV during VCV with VTset from 400 ml to 1000 ml when the ambient pressure increases from 1.0 ATA to 2.0 ATA. The raised ambient pressure will lead to increased gas density, which may result in more airway resistance and higher Ppeak during VCV.

Simple, Accurate Calculation of Mechanical Power in Pressure Controlled Ventilation (PCV)

Power is a promising new metric to assess energy transfer from a ventilator to a patient, as it combines the effects of multiple different parameters into a single comprehensive value. For volume-controlled ventilation (VCV), excellent equations exist for calculating power from basic ventilator parameters, but for pressure-controlled ventilation (PCV), an accurate, easy-to-use equation has been elusive. Here, we present a new power equation and evaluate its accuracy compared to the three published PCV power equations. When applied to a sample of 50 patients on PCV with a non-zero rise time, we found that our equation estimated power within an average of 8.4% ± 5.9% (mean ± standard deviation) of the reference value. This new equation is accurate and simple to use, making it an attractive option to estimate power in PCV cases at the bedside.

Comparison of volume guarantee and volume-controlled ventilation both using closed loop inspired oxygen in preterm infants: a randomised crossover study (CLIO-VG study)

ObjectiveThe objective of this study was to compare two different modes of ventilation in maintaining oxygen saturation (SpO2) in target range (90%–95%) in ventilated preterm infants cared for with automatic control of oxygen delivery (A-FiO2).DesignA single-centre randomised crossover study.SettingsA level III neonatal intensive care unit.PatientsPreterm infants receiving mechanical ventilation and oxygen requirement >21%.InterventionsVolume guarantee (VG) vs volume controlled ventilation (VCV) modes with automatic oxygen control (A-FiO2).OutcomesThe primary outcome of this study was the proportion of time spent with oxygen saturations in the target range (90%–95%) .ResultsNineteen preterm infants with a median gestation age 25 weeks (IQR: 24–28) and birth weight 685 g (IQR: 595–980) were enrolled in the study. There was no significant difference in primary outcome of median proportion of time spent in target saturation between the two arms (72% (57–81) in VG vs 75% (58–83) in VCV; p=0.98). There was no significant difference in the secondary outcomes of time spent in SpO2 <80% (0.03% vs 0.14%; p=0.51), time spent in SpO2 >98% (0.50% vs 0.08%; p=0.54), the median FiO2 (31% vs 29%; p=0.51) or manual adjustments carried out between VG and VCV, respectively. The number of episodes of prolonged hypoxaemia and hyperoxaemia were similar in the two groups.ConclusionThere was no significant difference in time spent in target SpO2 range between VG and VCV when A-FiO2 was used as the FiO2 controller in this crossover randomised control study.Trial registration numberNCT03865069.