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).

Effects on Lung Gas Volume, Respiratory Mechanics and Gas Exchange of a Closed-Circuit Suctioning System during Volume- and Pressure-Controlled Ventilation in ARDS Patients

Mechanically ventilated patients periodically require endotracheal suctioning. There are conflicting data regarding the loss of lung gas volume caused by the application of a negative pressure by closed-circuit suctioning. The aim of this study was to evaluate the effects of suctioning performed by a closed-circuit system in ARDS patients during volume- or pressure-controlled ventilation. In this prospective crossover-design study, 18 ARDS patients were ventilated under volume and pressure control applied in random order. Gas exchange, respiratory mechanics and EIT-derived end-expiratory lung volume (EELV) before the suctioning manoeuvre and after 5, 15 and 30 min were recorded. The tidal volume and respiratory rate were similar in both ventilation modes; in volume control, the EELV decreased by 31 ± 23 mL, 5 min after the suctioning, but it remained similar after 15 and 30 min; the oxygenation, PaCO2 and respiratory system elastance did not change. In the pressure control, 5 min after suctioning, EELV decreased by 35 (26–46) mL, the PaO2/FiO2 did not change, while PaCO2 increased by 5 and 30 min after suctioning (45 (40–51) vs. 48 (43–52) and 47 (42–54) mmHg, respectively). Our results suggest minimal clinical advantages when a closed system is used in volume-controlled compared to pressure-controlled ventilation.

Simulated Ventilation of Two Patients With a Single Ventilator in a Pandemic Setting

Background: Simultaneous ventilation of two patients, e.g., due to a shortage of ventilators in a pandemic, may result in hypoventilation in one patient and hyperinflation in the other patient. Methods: In a simulation of double patient ventilation using artificial lungs with equal compliances (70mL∙mbar-1), we tried to voluntarily direct gas flow to one patient by using 3D-printed y-adapters and stenosis adapters during volume-, and pressure-controlled ventilation. Subsequently, we modified the model using a special one-way valve on the limited flow side and measured in pressure-controlled ventilation with the flow sensor adjusted on either side in a second and third setup. In the last setup, we also measured with different lung compliances.Results: Volume- or pressure-controlled ventilation using standard connection tubes with the same compliance in each lung resulted in comparable minute volumes in both lungs, even if one side was obstructed to 3mm (6.6±0.2vs.6.5±0.1L for volume-controlled ventilation, p=.25 continuous severe alarm and 7.4±0.1vs.6.1±0.1L for pressure-controlled ventilation, p=.02 no alarm). In the second setup, pressure-controlled ventilation resulted at a 3mm flow limitation in minute ventilation of 9.4±0.3vs3.5±0.1L∙min-1, p=.001. In a third setup using the special one-way valve and the flow sensor on the unobstructed side, pressure-controlled ventilation resulted at a 3mm flow limitation in minute ventilation of 7.4±0.2vs3±0L∙min-1, at the compliance of 70mL∙mbar-1 for both lungs, 7.2±0vs4.1±0L∙ min-1, at the compliances of 50 vs. 70mL∙mbar-1, and 7.2±0.2vs5.7±0L∙ min-1, at the compliance of 30 vs. 70mL∙mbar-1 (all p=.001).Conclusions: Overriding a modern intensive care ventilator's safety features are possible, thereby ventilating two lungs with one ventilator simultaneously in a laboratory simulation using 3D-printed y-adapters. Directing tidal volumes in different pulmonary conditions towards one lung using 3D-printed flow limiters with diameters <6mm was also possible. While this ventilation setting was technically feasible in a bench model, it would be volatile, if not dangerous in a clinical situation.

Using exhalation dynamics to evaluate PEEP levels in COVID-19 related ARDS

Background We hypothesized that measured expiratory time constant (TauE) could be a bedside parameter for evaluation of PEEP settings in mechanically ventilated COVID-19 patients during pressure-controlled ventilation (PCV) mode. TauE is an easily measured parameter to assess lung physiology, even in non-homogeneous lungs including COVID-19 ARDS. Methods A prospective study was conducted including consecutively admitted adults (n = 16) with COVID-19 related ARDS requiring mechanical ventilation. Ventilator settings for all patients included: PCV, RR 18/min, constant inspiratory pressure 14 cmH2O, I:E ratio 1:1.5 and FiO2 1.0. Escalating levels of PEEP (0 to 18 cmH2O) were applied and measured TauE and expiratory tidal volume (Vte) recorded. Next, a new parameter, TauE Index (TEI) was calculated (TEI = TauE * Vte) at each PEEP level in prone (n = 29) or supine (n = 24) positions. TEI maps were created to graphically show changes in individual physiology with PEEP. The PEEP setting with the highest TEI corresponded to the highest product of TauE and Vte and was considered the most suitable PEEP. Most suitable PEEP range was calculated as ± 10% from highest TEI. Results Two groups of patterns were observed in the TEI maps, recruitable (R) (75%) and non-recruitable (NR) (25%). In R group, the most suitable PEEP and PEEP range was 9±3 cmH2O and 6-12 cmH2O for prone position and 11±3 cmH2O and 7-13 cmH2O for supine position. In NR group, the most suitable PEEP and PEEP range was 7±3 cmH2O and 0-8 cmH2O for prone position and 4±2 cmH2O and 0-7 cmH2O for supine position, respectively. The R group showed significantly higher suitable PEEP (p<0.01) and PEEP ranges (p<0.01) than NR group. 45% of measurements resulted in most suitable PEEP being significantly different between the positions (p < 0.01). Conclusions Based on TEI mapping, responses to PEEP were easily measured. There was wide variation in patient responses to PEEP that indicate the need for personalized evaluation.

Changes of Physiological parameters of the patient during laparoscopic gynaecology

Analysing and fusing data from the medical devices of different disciplines (anaesthesiology and surgery) inside the operating rooms may promote awareness during surgical procedures. In this work, the changes of physiological parameters of patients undergoing laparoscopic gynaecology procedures were analysed. The statistical relationship between the intra-abdominal pressure and airway peak pressure was evaluated. Patients ventilated with pressure-controlled ventilation (PCV) and intermittent mandatory ventilation (IMV) were included. The results demonstrated that increasing the intra-abdominal pressure (IAP) resulted in increasing the airway peak pressure and decreasing the lung compliance. The Pearson correlation coefficient between the IAP and the airway peak pressure was 0.910 in PCV-patients and 0.952 in IMV-patients when changes of the ventilation settings were considered. Additionally, major hemodynamic changes included alterations in the mean blood pressure (MBP), where the MBP increased after insufflating the abdomen and decreased after abdomen deflation.

Effect of pressure-controlled ventilation-volume guaranteed mode combined with individualized positive end-expiratory pressure on respiratory mechanics, oxygenation and lung injury in patients undergoing laparoscopic surgery in Trendelenburg position

The study aimed to investigate the efficacy of PCV-VG combined with individual PEEP during laparoscopic surgery in the Trendelenburg position. 120 patients were randomly divided into four groups: VF group (VCV plus 5cmH2O PEEP), PF group (PCV-VG plus 5cmH2O PEEP), VI group (VCV plus individual PEEP), and PI group (PCV-VG plus individual PEEP). Pmean, Ppeak, Cdyn, PaO2/FiO2, VD/VT, A-aDO2 and Qs/Qt were recorded at T1 (15 min after the induction of anesthesia), T2 (60 min after pneumoperitoneum), and T3 (5 min at the end of anesthesia). The CC16 and IL-6 were measured at T1 and T3. Our results showed that the Pmean was increased in VI and PI group, and the Ppeak was lower in PI group at T2. At T2 and T3, the Cdyn of PI group was higher than that in other groups, and PaO2/FiO2 was increased in PI group compared with VF and VI group. At T2 and T3, A-aDO2 of PI and PF group was reduced than that in other groups. The Qs/Qt was decreased in PI group compared with VF and VI group at T2 and T3. At T2, VD/VT in PI group was decreased than other groups. At T3, the concentration of CC16 in PI group was lower compared with other groups, and IL-6 level of PI group was decreased than that in VF and VI group. In conclusion, the patients who underwent laparoscopic surgery, PCV-VG combined with individual PEEP produced favorable lung mechanics and oxygenation, and thus reducing inflammatory response and lung injury.Clinical Trial registry: chictr.org. identifier: ChiCTR-2100044928