Unconventional approaches to mechanical ventilation-step-by-step through the COVID-19 crisis

The Transport of Respiratory Distress Syndrome Twin Newborns: The 27-Year-Long Experience of Gaslini Neonatal Emergency Transport Service Using Both Single and Double Ventilators

OBJECTIVE

Twin pregnancy rates have increased in the past 30 years. We describe the experience of the Neonatal Emergency Transport Service of the Gaslini Hospital, Genoa, Italy, in the transport of twin newborns.

METHODS

This was a retrospective study (1996-2021); 7,852 medical charts from the Neonatal Emergency Transport Service were reviewed. We included all twin newborns who were transported with respiratory distress syndrome in the study. We split the included patients into 2 groups (group A and group B) based on if they were simultaneously ventilated by a single ventilator or by 2 different ventilators, and then each group was split by the different types of ventilation (nasal continuous positive airway pressure or intermittent positive pressure ventilation). The pH level, base excess, O₂ saturation, Pco₂, body temperature, plasma glucose, and Transport Risk Index of Physiologic Stability score were recorded at departure and arrival.

RESULTS

One hundred thirty-six patients were included (68 pairs of twins); group A consisted of 92 newborns and group B 44 newborns. Although some significant differences were observed (statistic), none of these had real clinical significance.

CONCLUSION

Transporting respiratory distress syndrome twin newborns is challenging. Our study provided a 27-year experience in the field. Transporting twins by a single ventilator is possible, but, in our opinion, using 2 ventilators mounted on the same transport module is the best possible choice in terms of clinical performance, logistics, and cost.

COVID-19 Lessons Learned: Response to the Anticipated Ventilator Shortage

Early in the COVID-19 pandemic predictions of a worldwide ventilator shortage prompted a worldwide search for solutions. The impetus for the scramble for ventilators was spurred on by inaccurate and often unrealistic predictions of ventilator requirements. Initial efforts looked simply at acquiring as many ventilators as possible from national and international sources. Ventilators from the Strategic National Stockpile were distributed to early hotspots in the Northeast and Northwest United States. In a triumph of emotion over logic, well-intended experts from other industries turned their time, talent, and treasure toward making a ventilator for the first time. Interest in shared ventilation (more than one patient per ventilator) was ignited by an ill-advised video on social media that ignored the principles of gas delivery in deference to social media notoriety. With shared ventilation, a number of groups mistook a physiologic problem for a plumbing problem. The United States government invoked the Defense Production Act to push automotive manufacturers to partner with existing ventilator manufacturers to speed production. The FDA granted emergency use authorization for "splitters" to allow shared ventilation as well as for ventilators and ancillary equipment. Rationing of ventilators was discussed in the lay press and medical literature but was never necessary in the US. Finally, planners realized that staff with expertise in providing mechanical ventilation were the most important shortage. Over 200,000 ventilators were purchased by the United States government, states, cities, health systems, and individuals. Most had little value in caring for patients with COVID-19 ARDS. This paper attempts to look at where miscalculations were made, with an eye toward what we can do better in the future.

Multiplex Ventilation: Solutions for Four Main Safety Problems

BACKGROUND

The COVID-19 pandemic has led to an increased demand for mechanical ventilators and concerns of a ventilator shortage. Several groups have advocated for 1 ventilator to ventilate 2 or more patients in the event of such a shortage. However, differences in patient lung mechanics could make sharing a ventilator detrimental to both patients. Our previous study indicated failure to ventilate in 67% of simulations. The safety problems that must be solved include individual control of tidal volume (V_T), individual measurement of V_T, individualization of PEEP settings, and individual PEEP measurement. The purpose of this study was to evaluate potential solutions developed at our institution.

METHODS

Two separate lung simulators were ventilated with a modified multiplex circuit using pressure control ventilation. Parameters of the lung models used for simulations (resistance and compliance) were evidence-based from published studies. Individual circuit-modification devices were first evaluated for accuracy. Devices were an adjustable flow diverter valve, a prototype dual volume display, a PEEP valve, and a disposable PEEP display. Then the full modified multiplex circuit was assessed by ventilating 6 pairs of simulated patients with different lung models and attempting to equalize ventilation. Ventilation was considered equalized when V_T and end-expiratory lung volume were within 10% for each simulation.

RESULTS

The adjustable flow diverter valve allowed volume adjustment to 1 patient without affecting the other. The average error of the dual volume display was -17%. The PEEP valves individualized PEEP, but the PEEP gauge error ranged from 17% to 41%. Using the multiplex circuit, ventilation was equalized regardless of differences in resistance or compliance, reversing the "failure modes" of our previous study.

CONCLUSIONS

The results of this simulation-based study indicate that devices for individual control and display of V_T and PEEP are effective in extending the usability and potential patient safety of multiplex ventilation.

Comparing Ventilation Parameters for COVID-19 Patients Using Both Long-Term ICU and Anesthetic Ventilators in Times of Shortage

In the first months of the COVID-19 pandemic in Europe, many patients were treated in hospitals using mechanical ventilation. However, due to a shortage of ICU ventilators, hospitals worldwide needed to deploy anesthesia machines for ICU ventilation (which is off-label use). A joint guidance was written to apply anesthesia machines for long-term ventilation. The goal of this research is to retrospectively evaluate the differences in measurable ventilation parameters between the ICU ventilator and the anesthesia machine as used for COVID-19 patients. In this study, we included 32 patients treated in March and April 2020, who had more than 3 days of mechanical ventilation, either in the regular ICU with ICU ventilators (Hamilton S1), or in the temporary emergency ICU with anesthetic ventilators (Aisys, GE). The data acquired during regular clinical treatment was collected from the Patient Data Management Systems. Available ventilation parameters (pressures and volumes: PEEP, P_peak, P_insp, V_tidal), monitored parameters EtCO₂, SpO₂, derived compliance C, and resistance R were processed and analyzed. A sub-analysis was performed to compare closed-loop ventilation (INTELLiVENT-ASV) to other ventilation modes. The results showed no major differences in the compared parameters, except for P_insp. PEEP was reduced over time in the with Hamilton treated patients. This is most likely attributed to changing clinical protocol as more clinical experience and literature became available. A comparison of compliance between the 2 ventilators could not be made due to variances in the measurement of compliance. Closed loop ventilation could be used in 79% of the time, resulting in more stable EtCO₂. From the analysis it can be concluded that the off-label usage of the anesthetic ventilator in our hospital did not result in differences in ventilation parameters compared to the ICU treatment in the first 4 days of ventilation.

Pragmatic Recommendations for the Management of Acute Respiratory Failure and Mechanical Ventilation in Patients with COVID-19 in Low- and Middle-Income Countries

Management of patients with severe or critical COVID-19 is mainly modeled after care for patients with severe pneumonia or acute respiratory distress syndrome (ARDS) from other causes, and these recommendations are based on evidence that often originates from investigations in resource-rich intensive care units located in high-income countries. Often, it is impractical to apply these recommendations to resource-restricted settings, particularly in low- and middle-income countries (LMICs). We report on a set of pragmatic recommendations for acute respiratory failure and mechanical ventilation management in patients with severe/critical COVID-19 in LMICs. We suggest starting supplementary oxygen when SpO2 is persistently lower than 94%. We recommend supplemental oxygen to keep SpO2 at 88-95% and suggest higher targets in settings where continuous pulse oximetry is not available but intermittent pulse oximetry is. We suggest a trial of awake prone positioning in patients who remain hypoxemic; however, this requires close monitoring, and clear failure and escalation criteria. In places with an adequate number and trained staff, the strategy seems safe. We recommend to intubate based on signs of respiratory distress more than on refractory hypoxemia alone, and we recommend close monitoring for respiratory worsening and early intubation if worsening occurs. We recommend low-tidal volume ventilation combined with FiO2 and positive end-expiratory pressure (PEEP) management based on a high FiO2/low PEEP table. We recommend against using routine recruitment maneuvers, unless as a rescue therapy in refractory hypoxemia, and we recommend using prone positioning for 12-16 hours in case of refractory hypoxemia (PaO2/FiO2 < 150 mmHg, FiO2 ≥ 0.6 and PEEP ≥ 10 cmH2O) in intubated patients as standard in ARDS patients. We also recommend against sharing one ventilator for multiple patients. We recommend daily assessments for readiness for weaning by a low-level pressure support and recommend against using a T-piece trial because of aerosolization risk.

The principle of salvage in the context of COVID-19

The prioritisation of scarce resources has a particular urgency within the context of the COVID-19 pandemic crisis. This paper sets out a hypothetical case of Patient X (who is a nurse) and Patient Y (who is a non-health care worker). They are both in need of a ventilator due to COVID-19 with the same clinical situation and expected outcomes. However, there is only one ventilator available. In addressing the question of who should get priority, the proposal is made that the answer may lie in how the pandemic is metaphorically described using military terms. If nursing is understood to take place at the 'frontline' in the 'battle' against COVID-19, a principle of military medical ethics-namely the principle of salvage-can offer guidance on how to prioritise access to a life-saving resource in such a situation. This principle of salvage purports a moral direction to return wounded soldiers back to duty on the battlefield. Applying this principle to the hypothetical case, this paper proposes that Patient X (who is a nurse) should get priority of access to the ventilator so that he/she can return to the 'frontline' in the fight against COVID-19.