The Use of Intermittent Non-Invasive Ventilation as an Alveolar Recruitment Method for Patient with Severe COVID 19 Pneumonia

Background: The use of non-invasive ventilation (NIV) as a therapy for acute respiratory distress syndrome (ARDS) secondary to COVID 19 pneumonia has been controversial. NIV is an aerosol generating procedure which may increase the risk of viral transmission amongst patients and staff. Because of fear of aerosolizing the virus and transmitting the disease, initial expert recommendation was to avoid NIV and proceed with early intubation. With further experience of the virus, this recommendation has been challenged and NIV has been used widely with some retrospective studies quoting between 11 to 56 percent of COVID 19 related respiratory failures being treated with NIV. Objective: The objective of this study is to assess the efficacy and safety of using non-invasive mechanical ventilation as an alveolar recruitment method for patients with severe COVID 19 pneumonia. This method was used by our respiratory team on selected patients during the early phase of the COVID 19 pandemic. Methods: We reviewed the charts of patients that were admitted to the American Hospital Dubai intensive care unit, or our medical step-down unit who had diffuse bilateral infiltrates requiring oxygen supplementation between March and October 2020. We identified patients who were on intermittent BiPAP in addition to standard care. We also monitored the rate of infection among staff taking care of these patients. Results: Average length of stay after starting BIPAP therapy was 6.8 days, while the average total length of stay was 13.6 days. Only one patient was transferred to the ICU after being on the BIPAP protocol and did not need intubation. All patients were discharged home either without oxygen or with their chronic baseline home oxygen requirement. Radiological improvement in aeration was seen in 100% of patients at follow-up x-ray post-intervention. There were no reported pulmonary complications from barotrauma, such as pneumothorax or pneumomediastinum. There were no reported cases of staff infection to the health care workers that were taking care of these patients Conclusion: Our first of its kind observational study showed clearly that using BIPAP therapy for one hour three times daily during nebulization therapy in addition to standard care resulted in a significant reduction in hospital length of stay and hastened the clinical and radiological improvement of patients with severe COVID 19 pneumonia.

High-flow oxygen therapy versus non-invasive ventilation: a randomised physiological cross-over study of alveolar recruitment in acute respiratory failure

High-flow nasal cannula (HFNC) oxygen therapy has recently shown clinical benefits in hypoxemic acute respiratory failure (ARF) patients, while the interest of non-invasive ventilation (NIV) remains debated. The primary endpoint was to compare alveolar recruitment using global end-expiratory electrical lung impedance (EELI) between HFNC and NIV. Secondary endpoints compared regional EELI, lung volumes (global and regional tidal volume variation (TV)), respiratory parameters, hemodynamic tolerance, dyspnea and patient comfort between HFNC and NIV, relative to face mask (FM).A prospective randomised cross-over physiological study was conducted in patients with hypoxemic ARF due to pneumonia. They received alternately HFNC, NIV and FM.Sixteen patients were included. Global EELI was 4083 with NIV and 2921 with HFNC (p=0.4). Compared to FM, NIV and HFNC significantly increased global EELI by 1810.5 (95%CI: (857; 2646)) and 826 (95%CI: (399.5; 2361)) respectively. Global and regional TV increased significantly with NIV compared to HFNC or FM, but not between HFNC and FM. NIV yielded a significantly higher SpO2/ FiO2 ratio compared to HFNC (p=0.03). No significant difference was observed between HFNC, NIV and FM for dyspnea. Patient comfort score with FM was not significantly different than with HFNC (p=0.1) but was lower with NIV (p=0.001).This study suggests a potential benefit of HFNC and NIV on alveolar recruitment in patients with hypoxemic ARF. In contrast with HFNC, NIV increased lung volumes which may contribute to overdistension and its potentially deleterious effect in these patients.

Validation of a novel system to assess end-expiratory lung volume and alveolar recruitment in an ARDS model

Background Personalizing mechanical ventilation requires the development of reliable bedside monitoring techniques. The multiple-breaths nitrogen washin–washout (MBNW) technique is currently available to measure end-expiratory lung volume (EELVMBNW), but the precision of the technique may be poor, with percentage errors ranging from 28 to 57%. The primary aim of the study was to evaluate the reliability of a novel MBNW bedside system using fast mainstream sensors to assess EELV in an experimental acute respiratory distress syndrome (ARDS) model, using computed tomography (CT) as the gold standard. The secondary aims of the study were: (1) to evaluate trending ability of the novel system to assess EELV; (2) to evaluate the reliability of estimated alveolar recruitment induced by positive end-expiratory pressure (PEEP) changes computed from EELVMBNW, using CT as the gold standard. Results Seven pigs were studied in 6 experimental conditions: at baseline, after experimental ARDS and during a decremental PEEP trial at PEEP 16, 12, 6 and 2 cmH2O. EELV was computed at each PEEP step by both the MBNW technique (EELVMBNW) and CT (EELVCT). Repeatability was assessed by performing replicate measurements. Alveolar recruitment between two consecutive PEEP levels after lung injury was measured with CT (VrecCT), and computed from EELV measurements (VrecMBNW) as ΔEELV minus the product of ΔPEEP by static compliance. EELVMBNW and EELVCT were significantly correlated (R2 = 0.97). An acceptable non-constant bias between methods was identified, slightly decreasing toward more negative values as EELV increased. The conversion equation between EELVMBNW and EELVCT was: EELVMBNW = 0.92 × EELVCT + 36. The 95% prediction interval of the bias amounted to ± 86 mL and the percentage error between both methods amounted to 13.7%. The median least significant change between repeated measurements amounted to 8% [CI95%: 4–10%]. EELVMBNW adequately tracked EELVCT changes over time (concordance rate amounting to 100% [CI95%: 87%–100%] and angular bias amounting to − 2° ± 10°). VrecMBNW and VrecCT were significantly correlated (R2 = 0.92). A non-constant bias between methods was identified, slightly increasing toward more positive values as Vrec increased. Conclusions We report a new bedside MBNW technique that reliably assesses EELV in an experimental ARDS model with high precision and excellent trending ability.

Comparison of Positive End-Expiratory Pressure versus Tidal Volume-Induced Ventilator-Driven Alveolar Recruitment Maneuver in Robotic Prostatectomy: A Randomized Controlled Study

Background: We evaluated the pulmonary effects of two ventilator-driven alveolar recruitment maneuver (ARM) methods during laparoscopic surgery. Methods: Sixty-four patients undergoing robotic prostatectomy were randomized into two groups: incrementally increasing positive end-expiratory pressure in a stepwise manner (PEEP group) versus tidal volume (VT group). We performed each ARM after induction of anesthesia in the supine position (T1), after pneumoperitoneum in the Trendelenburg position (T2), and after peritoneum desufflation in the supine position (T3). The primary outcome was change in end-expiratory lung impedance (EELI) before and 5 min after ARM at T3, measured by electrical impedance tomography. Results: The PEEP group showed significantly higher increasing EELI 5 min after ARM than the VT group at T1 and T3 (median [IQR] 460 [180,800] vs. 200 [80,315], p = 0.002 and 280 [170,420] vs. 95 [55,175], p = 0.004, respectively; PEEP group vs. VT group). The PEEP group showed significantly higher lung compliance and lower driving pressure at T1 and T3. However, there was no significant difference in EELI change, lung compliance, or driving pressure after ARM at T2. Conclusions: The ventilator-driven ARM by the increasing PEEP method led to greater improvements in lung compliance at the end of laparoscopic surgery than the increasing VT method.

Practical Review of Mechanical Ventilation in Adults and Children in The Operating Room and Emergency Department

Background: During general anesthesia, mechanical ventilation can cause pulmonary damage through mechanism of ventilator-induced lung injury which is a major cause of postoperative pulmonary complications, which varies between 5 and 33% and increases significantly the 30-day mortality of the surgical patient. Objective: The aim of this review is to analyze different variables which played key role in safe application of mechanical ventilation in the operating room and emergency setting. Method: Also, we wanted to analyze different types of population that underwent intraoperative mechanical ventilation like obese patients, pediatric and adult population and different strategies such as one lung ventilation and ventilation in trendelemburg position. The peer-reviewed articles analyzed were selected according to PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) from Pubmed/Medline, Ovid/Wiley and Cochrane Library, combining key terms such as: “pulmonary post-operative complications”, “protective ventilation”, “alveolar recruitment maneuvers”, “respiratory compliance”, “intraoperative paediatric ventilation”, “best peep”, “types of ventilation”. Among the 230 papers identified, 150 articles were selected, after title - abstract examination and removing the duplicates, resulting in 94 articles related to mechanical ventilation in operating room and emergency setting that were analyzed. Results: Careful preoperative patient’s evaluation and protective ventilation (i.e. use of low tidal volumes, adequate PEEP and alveolar recruitment maneuvers) has been shown to be effective not only in limiting alveolar de-recruitment, alveolar overdistension and lung damage, but also in reducing the onset of pulmonary post-operative complications (PPCs). Conclusion: Mechanical ventilation is like “Janus Bi-front” because it is essential for surgical procedures, for the care of critical care patients and in life-threatening conditions but it can be harmful to the patient if continued for a long time and where an excessive dose of oxygen is administered into the lungs. Low tidal volume is associated with minor rate of PPCs and other complications and every complication can increase length of Stay, adding cost to NHS between 1580 € and 1650 € per day in Europe and currently the prevention of PPCS is only weapon that we possess.