Invasive Ventilation Modes Research Articles

Effects of jet nebulization on ventilator performance with different invasive ventilation modes: A bench study.

The effects of jet nebulization on ventilator performance in the volume control mode (VC) and pressure control mode (PC) of ventilation have not been determined. The present study investigated the impact of jet nebulization on ventilator performance in different modes in vitro. Two types of jet nebulizer (ventilator-integrated jet nebulizers, external jet nebulizer) and six types of ventilator were connected with a simulated lung to simulate aerosol therapy during mechanical ventilation. The ventilation modes were set to VC and PC, and the driving flows of external jet nebulizer were set at 4 L/min and 8 L/min, respectively. Jet nebulizers were placed between patient airway and Y-piece or at 15 cm from the Y-piece in the inspiratory limb. The effects of jet nebulization were compared with the baseline of triggering performance, control performance, and tidal volume under different experimental conditions. Ventilator-integrated jet nebulizers had no effect on ventilator performance in different modes (all P > 0.05). However, the effects of external jet nebulizers on ventilator performance varied widely: for triggering performance, all parameters were increased in different modes and nebulization positions (all P < 0.05), including the time from the beginning of the inspiratory effort to the lowest value of airway pressure needed to trigger the ventilator (TPmin), the time to trigger (Ttrig), and the magnitude of airway pressure drop needed to trigger (Ptrig); for control performance, peak inspiratory pressure (Ppeak) and peak inspiratory flow(Pflow) were increased in the VC mode (P < 0.05), but not significantly changed in the PC mode (P > 0.05);the actual tidal volume (VT) and expiratory tidal volume monitored (VTe) were significantly increased (P < 0.05), however, the inspiratory tidal volume monitored (VTi) was not affected by jet nebulization in the VC mode. In the PC mode, there were no significant changes in VT, whereas VTi decreased and VTe increased (P < 0.05). The higher the driving flow of external jet nebulizers, the stronger the impact on ventilator performance (all P < 0.05). Triggering performance was decreased in both the VC and PC modes when using an external jet nebulizer, while the effects of nebulization on control performance and tidal volume varied significantly.

Quantifying ventilator unloading in CPAP ventilation

BackgroundThe intrinsic (muscular) patient effort driving inspiration in non-invasive ventilation modes, such as continuous positive airway pressure (CPAP) therapy, has not been identified from non-invasive data. Current CPAP settings are based on clinical judgment and assessment of symptoms of respiratory distress. Non-optimal settings, including too much positive end expiratory pressure (PEEP) can cause unintended lung injury and ventilator unloading, where patient effort drops and the CPAP device enables too much work being imposed on the injured lung. Currently, there is no non-invasive means of quantifying or identifying these effects. MethodsA novel model-based method of ascertaining intrinsic patient work of breathing (WOB) in CPAP is developed based on linear single compartment and 2nd order b-spline models previously used in invasive ventilation modes. Results are compared to current clinical indications, such as total Imposed WOB from the CPAP device and beak length, the latter of which is the clinical metric used to indicate alveolar overdistension. Intrinsic and Imposed WOB are compared.The hypothesis is that ventilator unloading can be assessed as a decrease in Intrinsic WOB relative to Imposed WOB, as PEEP and associated ventilator unloading rise. This hypothesis is tested using 14 subjects from a CPAP trial of several breathing rates at two PEEP levels. ResultsThe ratio of Intrinsic to Imposed WOB, normalised per unit tidal volume, decreased with increasing PEEP (4–7 cm H2O), capturing the expected trend of ventilator unloading. Ventilator unloading was observed across all breathing rates. Beak length measurements showed no conclusive evidence of capturing overdistension at higher PEEP or ventilator unloading. ConclusionsPatient Intrinsic WOB in CPAP was non-invasively quantified using model-based methods, based on pressure and flow measurements. The ratio of Intrinsic to Imposed WOB per unit tidal volume clearly and consistently showed ventilator unloading across all patients and breathing rates, with Intrinsic WOB decreasing with increasing PEEP. This trend was not observed in the current clinical metric of beak length. Non-invasively quantifying Intrinsic WOB and ventilator unloading is the critical first step to objectively optimising clinical CPAP settings, patient care, and outcomes.

Velocity-based target flow rate for high-flow nasal cannula oxygen therapy.

The aim of this study was to assess retrospectively whether the average inspiratory flow velocity-based initial flow rate in high-flow nasal cannula (HFNC) therapy could be well tolerated and safely used for infants and children hospitalized with moderate to severe respiratory failure. Thirty-three patients without underlying diseases (22 males; 67%), hospitalized to receive HFNC therapy for infection-related respiratory failure, were analyzed. The median age was 2months (interquartile range, 1month to 1year). Patients with dyspnea and carbon dioxide partial pressure (pCO2 ) >50mmHg or venous blood pH <7.320, combined with pulse oximetry arterial oxygen saturation <92%, were included. We set target flow rates calculated from the average inspiratory flow velocity, starting at the actual initial flow rates, and these were subsequently adjusted if necessary. One patient could not tolerate the cannula. Of the remaining 32 patients, 81% (n = 26) had an actual initial flow rate within 1 L of the target flow rate; these patients were evaluated for changes in the fraction of inspired oxygen (FITarget flow rate tableO2 ), pH, and pCO2 values after 24h. Three patients required a higher fraction of inspired oxygen, one showed a persistent pH < 7.320, and seven exhibited pCO2 >50mmHg. No patient required non-invasive positive-pressure ventilation, and one required intubation. Pneumothorax was not reported in any patient. The average inspiratory flow velocity-based initial flow rate was well-tolerated without sedation, and there were no severe complications. Starting at this flow rate would improve the use of HFNC therapy in the pediatric ward, possibly reducing the need for more invasive modes of ventilation.

Critical Obstetric Patients During the Coronavirus Disease 2019 Pandemic: Operationalizing an Obstetric Intensive Care Unit.

Critical Obstetric Patients During the Coronavirus Disease 2019 Pandemic: Operationalizing an Obstetric Intensive Care Unit.

Influence of invasive ventilation modes on weaning and extubation evolution of critical patients

The aim of this research was to analyze the influence of invasive ventilation modes on weaning and extubation process. It is a prospective cohort study that assessed patients admitted to the Intensive Care Unit (ICU) using Invasive Mechanical Ventilation (IMV). The following aspects were considered: ventilation mode used, days until evolution to weaning and extubation, its success/failure, hospitalization period, and ICU outcome (discharge/death). Sixty patients were assessed, 48 of which were admitted on volume-controlled ventilation (VCV), three on pressure-controlled ventilation (PCV), and nine on spontaneous mode. A total of 79% of VCV individuals and 67% of PCV went into spontaneous mode. There was no significant difference between modes for time until evolution to spontaneous breathing, neither between that and weaning and extubation. Among possible factors responsible for weaning and extubation success, only days on spontaneous mode influenced these outcomes, so individuals who breathed spontaneously for more days were 1.5% more likely to succeed at weaning and 1.3% more likely to succeed at extubation. The ventilation mode used at admission did not influence weaning and extubation process. Longer time on spontaneous breathing mode predicted the patients’ greater chances of weaning and extubation success.

Accuracy of Reported Tidal Volume During Neonatal Ventilation With Airway Leak: A Lung Model Study.

To determine the accuracy of tidal volume reported by neonatal ventilators, with and without leak compensation, in invasive and noninvasive ventilation modes in the presence of airway leak; and, to determine what factors have a significant effect on the accuracy of tidal volume reported by ventilators with leak compensation in the presence of airway leak. We hypothesized that ventilators with a leak compensation function that includes estimation of tidal volume could accurately report tidal volume in the presence of airway leak, but that the accuracy of reported tidal volume may be affected by variables such as the identity of the ventilator, lung mechanics, leak size, positive end-expiratory pressure level, and body size. In vitro assessment of ventilator volume delivery was conducted for seven acute care ventilators using a passive lung simulator. Laboratory-based measurements. The error of reported tidal volume was calculated under three ventilation modes (noninvasive-pressure-control, invasive-pressure-control, and invasive-dual-control ventilation), three models of lung mechanics (normal and restrictive and obstructive lung disease), a range of airway leak values, two positive end-expiratory pressure values, and two body weights for each ventilator. Ventilators with and without leak compensation were studied. In the absence of airway leak, all ventilators reported tidal volume accurately. In the presence of airway leak, the error of reported tidal volume increased for all ventilators without a leak compensation algorithm while ventilators with leak compensation that included estimation of tidal volume accurately reported tidal volume. In the presence of airway leak, clinically significant effects on the error of reported tidal volume by ventilators with leak compensation were associated with the choice of ventilator in all modes and with lung mechanics in invasive ventilation modes. Reported tidal volume is affected by the presence of airway leak, but in many ventilators a leak compensation algorithm that includes estimation of tidal volume can correct for the discrepancy between actual and reported tidal volume. However, even in ventilators with leak compensation, choice of ventilator and lung mechanics in invasive ventilation modes have a significant effect on error of reported tidal volume.

Invasive ventilation modes in children: a systematic review and meta-analysis

IntroductionThe purpose of the present study was to critically review the existing body of evidence on ventilation modes for infants and children up to the age of 18 years.MethodsThe PubMed and EMBASE databases were searched using the search terms 'artificial respiration', 'instrumentation', 'device', 'devices', 'mode', and 'modes'. The review included only studies comparing two ventilation modes in a randomized controlled study and reporting one of the following outcome measures: length of ventilation (LOV), oxygenation, mortality, chronic lung disease and weaning. We quantitatively pooled the results of trials where suitable.ResultsFive trials met the inclusion criteria. They addressed six different ventilation modes in 421 children: high-frequency oscillation (HFO), pressure control (PC), pressure support (PS), volume support (VS), volume diffusive respirator (VDR) and biphasic positive airway pressure. Overall there were no significant differences in LOV and mortality or survival rate associated with the different ventilation modes. Two trials compared HFO versus conventional ventilation. In the pooled analysis, the mortality rate did not differ between these modes (odds ratio = 0.83, 95% confidence interval = 0.30 to 1.91). High-frequency ventilation (HFO and VDR) was associated with a better oxygenation after 72 hours than was conventional ventilation. One study found a significantly higher PaO2/FiO2 ratio with the use of VDR versus PC ventilation in children with burns. Weaning was studied in 182 children assigned to either a PS protocol, a VS protocol or no protocol. Most children could be weaned within 2 days and the weaning time did not significantly differ between the groups.ConclusionsThe literature provides scarce data for the best ventilation mode in critically ill children beyond the newborn period. There is no evidence, however, that high-frequency ventilation reduced mortality and LOV. Longer-term outcome measures such as pulmonary function, neurocognitive development, and cost-effectiveness should be considered in future studies.

Ventilatory Support

Critically ill patients in respiratory failure often require mechanical respiratory support to treat hypoxaemia, ventilatory failure or both. Non-invasive ventilation (NIV) using an airtight facemask (rather than an endotracheal tube) has been shown to improve survival in suitable groups of patients who require respiratory support. In acute respiratory distress syndrome (ARDS) and acute lung injury (see Gunning, page 66), invasive ventilation modes and strategies have been developed to protect the delicate lung tissue and some have been shown to decrease mortality. This contribution will focus on ventilatory support in the critically ill patient in an ICU, but mechanical ventilatory support can also be provided in the following locations: • home: usually intermittently (e.g. at night) and non-invasively • hospital wards: via the non-invasive route, if appropriate facilities and staff are available • hospital theatres: during anaesthesia and immediately postoperatively. The goals of mechanical ventilation are summarized in Figure 1. These goals change as the condition of the patient changes.

New tools in ventilatory support: High frequency ventilation, nitric oxide, tracheal gas insufflation, non-invasive ventilation

Protection of the lungs against ventilator-induced lung injury is becoming one of the main concerns in pediatric and neonatal intensive care. High frequency ventilation using a constant distending pressure with small variations during respiratory cycles allows adequate recruitment. High frequency oscillation is the most promising HFV mode especially in premature neonates but clinical studies are contradictory. Nitric oxide, an inhaled gas with specific pulmonary vasodilating effects, has become a powerful tool in the treatment of pulmonary arterial hypertension alone or in combination with HFO, but studies have failed to show improvement in survival in neonates as well as in children with ARDS. Tracheal gas insufflation, in addition to conventional ventilation, by washing dead space during exhalation, improves gas exchange while lowering tidal volume. It is however still experimental. Maintenance of spontaneous ventilation during conventional ventilation improves gas exchange, hemodynamic functions, mobilization, active coughing, and avoids prolonged muscle weakness. Non invasive modes of ventilation like BiPAP have certain indications in pediatrics but need to become more familiar to the pediatric intensivist.