A quantitative evaluation of aerosol generation during tracheal intubation and extubation: a reply

A quantitative evaluation of aerosol generation during cardiopulmonary resuscitation

It is unclear if cardiopulmonary resuscitation is an aerosol-generating procedure and whether this poses a risk of airborne disease transmission to healthcare workers and bystanders. Use of airborne transmission precautions during cardiopulmonary resuscitation may confer rescuer protection but risks patient harm due to delays in commencing treatment. To quantify the risk of respiratory aerosol generation during cardiopulmonary resuscitation in humans, we conducted an aerosol monitoring study during out-of-hospital cardiac arrests. Exhaled aerosol was recorded using an optical particle sizer spectrometer connected to the breathing system. Aerosol produced during resuscitation was compared with that produced by control participants under general anaesthesia ventilated with an equivalent respiratory pattern to cardiopulmonary resuscitation. A porcine cardiac arrest model was used to determine the independent contributions of ventilatory breaths, chest compressions and external cardiac defibrillation to aerosol generation. Time-series analysis of participants with cardiac arrest (n = 18) demonstrated a repeating waveform of respiratory aerosol that mapped to specific components of resuscitation. Very high peak aerosol concentrations were generated during ventilation of participants with cardiac arrest with median (IQR [range]) 17,926 (5546-59,209 [1523-242,648]) particles.l-1 , which were 24-fold greater than in control participants under general anaesthesia (744 (309-2106 [23-9099]) particles.l-1 , p < 0.001, n = 16). A substantial rise in aerosol also occurred with cardiac defibrillation and chest compressions. In a complimentary porcine model of cardiac arrest, aerosol recordings showed a strikingly similar profile to the human data. Time-averaged aerosol concentrations during ventilation were approximately 270-fold higher than before cardiac arrest (19,410 (2307-41,017 [104-136,025]) vs. 72 (41-136 [23-268]) particles.l-1 , p = 0.008). The porcine model also confirmed that both defibrillation and chest compressions generate high concentrations of aerosol independent of, but synergistic with, ventilation. In conclusion, multiple components of cardiopulmonary resuscitation generate high concentrations of respiratory aerosol. We recommend that airborne transmission precautions are warranted in the setting of high-risk pathogens, until the airway is secured with an airway device and breathing system with a filter.

Identification of the source events for aerosol generation during oesophago-gastro-duodenoscopy

OBJECTIVE

To determine if oesophago-gastro-duodenoscopy (OGD) generates increased levels of aerosol in conscious patients and identify the source events.

DESIGN

A prospective, environmental aerosol monitoring study, undertaken in an ultraclean environment, on patients undergoing OGD. Sampling was performed 20 cm away from the patient's mouth using an optical particle sizer. Aerosol levels during OGD were compared with tidal breathing and voluntary coughs within subject.

RESULTS

Patients undergoing bariatric surgical assessment were recruited (mean body mass index 44 and mean age 40 years, n=15). A low background particle concentration in theatres (3 L-1) enabled detection of aerosol generation by tidal breathing (mean particle concentration 118 L-1). Aerosol recording during OGD showed an average particle number concentration of 595 L-1 with a wide range (3-4320 L-1). Bioaerosol-generating events, namely, coughing or burping, were common. Coughing was evoked in 60% of the endoscopies, with a greater peak concentration and a greater total number of sampled particles than the patient's reference voluntary coughs (11 710 vs 2320 L-1 and 780 vs 191 particles, n=9 and p=0.008). Endoscopies with coughs generated a higher level of aerosol than tidal breathing, whereas those without coughs were not different to the background. Burps also generated increased aerosol concentration, similar to those recorded during voluntary coughs. The insertion and removal of the endoscope were not aerosol generating unless a cough was triggered.

CONCLUSION

Coughing evoked during OGD is the main source of the increased aerosol levels, and therefore, OGD should be regarded as a procedure with high risk of producing respiratory aerosols. OGD should be conducted with airborne personal protective equipment and appropriate precautions in those patients who are at risk of having COVID-19 or other respiratory pathogens.

Quantitative evaluation of aerosol generation during manual facemask ventilation

Manual facemask ventilation, a core component of elective and emergency airway management, is classified as an aerosol-generating procedure. This designation is based on one epidemiological study suggesting an association between facemask ventilation and transmission during the SARS-CoV-1 outbreak in 2003. There is no direct evidence to indicate whether facemask ventilation is a high-risk procedure for aerosol generation. We conducted aerosol monitoring during routine facemask ventilation and facemask ventilation with an intentionally generated leak in anaesthetised patients. Recordings were made in ultraclean operating theatres and compared against the aerosol generated by tidal breathing and cough manoeuvres. Respiratory aerosol from tidal breathing in 11 patients was reliably detected above the very low background particle concentrations with median [IQR (range)] particle counts of 191 (77-486 [4-1313]) and 2 (1-5 [0-13]) particles.l-1 , respectively, p = 0.002. The median (IQR [range]) aerosol concentration detected during facemask ventilation without a leak (3 (0-9 [0-43]) particles.l-1 ) and with an intentional leak (11 (7-26 [1-62]) particles.l-1 ) was 64-fold (p = 0.001) and 17-fold (p = 0.002) lower than that of tidal breathing, respectively. Median (IQR [range]) peak particle concentration during facemask ventilation both without a leak (60 (0-60 [0-120]) particles.l-1 ) and with a leak (120 (60-180 [60-480]) particles.l-1 ) were 20-fold (p = 0.002) and 10-fold (0.001) lower than a cough (1260 (800-3242 [100-3682]) particles.l-1 ), respectively. This study demonstrates that facemask ventilation, even when performed with an intentional leak, does not generate high levels of bioaerosol. On the basis of this evidence, we argue facemask ventilation should not be considered an aerosol-generating procedure.

A quantitative evaluation of aerosol generation during supraglottic airway insertion and removal

Many guidelines consider supraglottic airway use to be an aerosol-generating procedure. This status requires increased levels of personal protective equipment, fallow time between cases and results in reduced operating theatre efficiency. Aerosol generation has never been quantitated during supraglottic airway use. To address this evidence gap, we conducted real-time aerosol monitoring (0.3-10-µm diameter) in ultraclean operating theatres during supraglottic airway insertion and removal. This showed very low background particle concentrations (median (IQR [range]) 1.6 (0-3.1 [0-4.0]) particles.l-1 ) against which the patient's tidal breathing produced a higher concentration of aerosol (4.0 (1.3-11.0 [0-44]) particles.l-1 , p = 0.048). The average aerosol concentration detected during supraglottic airway insertion (1.3 (1.0-4.2 [0-6.2]) particles.l-1 , n = 11), and removal (2.1 (0-17.5 [0-26.2]) particles.l-1 , n = 12) was no different to tidal breathing (p = 0.31 and p = 0.84, respectively). Comparison of supraglottic airway insertion and removal with a volitional cough (104 (66-169 [33-326]), n = 27), demonstrated that supraglottic airway insertion/removal sequences produced <4% of the aerosol compared with a single cough (p < 0.001). A transient aerosol increase was recorded during one complicated supraglottic airway insertion (which initially failed to provide a patent airway). Detailed analysis of this event showed an atypical particle size distribution and we subsequently identified multiple sources of non-respiratory aerosols that may be produced during airway management and can be considered as artefacts. These findings demonstrate supraglottic airway insertion/removal generates no more bio-aerosol than breathing and far less than a cough. This should inform the design of infection prevention strategies for anaesthetists and operating theatre staff caring for patients managed with supraglottic airways.

A position statement and practical guide to the use of particulate filtering facepiece respirators (N95, FFP2, or equivalent) for South African health workers exposed to respiratory pathogens including Mycobacterium tuberculosis and SARS-CoV-2

SUMMARY

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is transmitted mainly by aerosol in particles <10 µm that can remain suspended for hours before being inhaled. Because particulate filtering facepiece respirators ('respirators'; e.g. N95 masks) are more effective than surgical masks against bio-aerosols, many international organisations now recommend that health workers (HWs) wear a respirator when caring for individuals who may have COVID-19. In South Africa (SA), however, surgical masks are still recommended for the routine care of individuals with possible or confirmed COVID-19, with respirators reserved for so-called aerosol-generating procedures. In contrast, SA guidelines do recommend respirators for routine care of individuals with possible or confirmed tuberculosis (TB), which is also transmitted via aerosol. In health facilities in SA, distinguishing between TB and COVID-19 is challenging without examination and investigation, both of which may expose HWs to potentially infectious individuals. Symptom-based triage has limited utility in defining risk. Indeed, significant proportions of individuals with COVID-19 and/or pulmonary TB may not have symptoms and/or test negative. The prevalence of undiagnosed respiratory disease is therefore likely significant in many general clinical areas (e.g. waiting areas). Moreover, a proportion of HWs are HIV-positive and are at increased risk of severe COVID-19 and death.

RECOMMENDATIONS

Sustained improvements in infection prevention and control (IPC) require reorganisation of systems to prioritise HW and patient safety. While this will take time, it is unacceptable to leave HWs exposed until such changes are made. We propose that the SA health system adopts a target of 'zero harm', aiming to eliminate transmission of respiratory pathogens to all individuals in every healthcare setting. Accordingly, we recommend: the use of respirators by all staff (clinical and non-clinical) during activities that involve contact or sharing air in indoor spaces with individuals who: (i) have not yet been clinically evaluated; or (ii) are thought or known to have TB and/or COVID-19 or other potentially harmful respiratory infections;the use of respirators that meet national and international manufacturing standards;evaluation of all respirators, at the least, by qualitative fit testing; andthe use of respirators as part of a 'package of care' in line with international IPC recommendations. We recognise that this will be challenging, not least due to global and national shortages of personal protective equipment (PPE). SA national policy around respiratory protective equipment enables a robust framework for manufacture and quality control and has been supported by local manufacturers and the Department of Trade, Industry and Competition. Respirator manufacturers should explore adaptations to improve comfort and reduce barriers to communication. Structural changes are needed urgently to improve the safety of health facilities: persistent advocacy and research around potential systems change remain essential.

Lessons from COVID-19: A reflection on the strengths and weakness of early consensus recommendations for pediatric difficult airway management during a respiratory viral pandemic using a modified Delphi method

BACKGROUND

The authors recognized a gap in existing guidelines and convened a modified Delphi process to address novel issues in pediatric difficult airway management raised by the COVID-19 pandemic.

METHODS

The Pediatric Difficult Intubation Collaborative, a working group of the Society for Pediatric Anesthesia, assembled an international panel to reach consensus recommendations on pediatric difficult airway management during the COVID-19 pandemic using a modified Delphi method. We reflect on the strengths and weaknesses of this process and ways care has changed as knowledge and experience have grown over the course of the pandemic.

RECOMMENDATIONS

In the setting of the COVID-19 pandemic, the Delphi panel recommends against moving away from the operating room solely for the purpose of having a negative pressure environment. The Delphi panel recommends supplying supplemental oxygen and using videolaryngoscopy during anticipated difficult airway management. Direct laryngoscopy is not recommended. If the patient meets extubation criteria, extubate in the OR, awake, at the end of the procedure.

REFLECTION

These recommendations remain valuable guidance in caring for children with anticipated difficult airways and infectious respiratory pathology when reviewed in light of our growing knowledge and experience with COVID-19. The panel initially recommended minimizing involvement of additional people and trainees and minimizing techniques associated with aerosolization of viral particles. The demonstrated effectiveness of PPE and vaccination at reducing the risk of exposure and infection to clinicians managing the airway makes these recommendations less relevant for COVID-19. They would likely be important initial steps in the face of novel respiratory viral pathogens.

CONCLUSIONS

The consensus process cannot and should not replace evidence-based guidelines; however, it is encouraging to see that the panel's recommendations have held up well as scientific knowledge and clinical experience have grown.

Emergency Airway Management Outside the Operating Room: Current Evidence and Management Strategies

Emergency airway management outside the operating room (OR) is often associated with an increased risk of airway related, as well as cardiopulmonary, complications which can impact morbidity and mortality. These emergent airways may take place in the intensive care unit (ICU), where patients are critically ill with minimal physiological reserve, or other areas of the hospital where advanced equipment and personnel are often unavailable. As such, emergency airway management outside the OR requires expertise at manipulation of not only the anatomically difficult airway but also the physiologically and situationally difficult airway. Adequate preparation and appropriate use of airway management techniques are important to prevent complications. Judicious utilization of pre- and apneic oxygenation is important as is the choice of medications to facilitate intubation in this at-risk population. Recent study in critically ill patients has shown that postintubation hemodynamic and respiratory compromise is common, independently associated with poor outcomes and can be impacted by the choice of drugs and techniques used. In addition to adequately preparing for a physiologically difficult airway, enhancing the ability to predict an anatomically difficult airway is essential in reducing complication rates. The use of artificial intelligence in the identification of difficult airways has shown promising results and could be of significant advantage in uncooperative patients as well as those with a questionable airway examination. Incorporating this technology and understanding the physiological, anatomical, and logistical challenges may help providers better prepare for managing such precarious airways and lead to successful outcomes. This review discusses the various challenges associated with airway management outside the OR, provides guidance on appropriate preparation, airway management skills, medication use, and highlights the role of a coordinated multidisciplinary approach to out-of-OR airway management.

A systematic review of meta-analyses comparing direct laryngoscopy with videolaryngoscopy

PURPOSE

In the preceding 20 years, many randomized-controlled trials and meta-analyses have compared direct Macintosh laryngoscopy with videolaryngoscopy. The videolaryngoscope blades have included both traditional Macintosh blades and hyperangulated blades. Macintosh and hyperangulated blades differ in their geometry and technique for tracheal intubation; certain patient populations may benefit from one blade type over another. The primary objective of this systematic review was to assess whether published meta-analyses comparing direct Macintosh laryngoscopy to videolaryngoscopy have accounted for the videolaryngoscope blade type. Secondary objectives evaluated heterogeneity among practitioner experience and specialty, clinical context, patient population, and original primary study outcomes.

SOURCE

A search was performed across Ovid Medline, Ovid Embase, ClinicalKey, PubMed, TRIP, AccessAnesthesiology, Google Scholar, and ANZCA discovery. A systematic review identified meta-analyses which compared direct Macintosh laryngoscopy to videolaryngoscopy. There were no patient age or clinical specialty restrictions. Exclusion criteria included non-English language, studies comparing non-Macintosh blade to videolaryngoscopy, and studies in awake patients.

PRINCIPAL FINDINGS

Twenty-one meta-analyses were identified that were published between 1 January 2000 and 7 May 2020. Macintosh and hyperangulated videolaryngoscope blades were combined in most studies (16/21; 76%). Heterogeneity was also present among practitioner experience (20/21; 95%), clinician specialty (15/21; 71%), and clinical locations (10/21; 48%). Adult and pediatric patients were combined or not defined in 5/21 studies (24%). The primary outcomes of the meta-analyses varied, with the most common (7/21; 33%) being first-pass tracheal intubation success.

CONCLUSIONS

Heterogeneity across important clinical variables is common in meta-analyses comparing direct Macintosh laryngoscopy to videolaryngoscopy. To better inform patient care, future videolaryngoscopy research should differentiate blade type, clinical context, and patient-related primary outcomes.

Aerosol containment device for airway management of patients with COVID-19: a narrative review

Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), is highly contagious. To protect healthcare workers from infection during airway management, some expert recommendations and guidelines recommended wearing P2/N95 masks, goggles or glasses, glove, face-shields, and gowns as standard personal protective equipment (PPE). Nevertheless, several simulation studies have suggested that the standard PPE may not fully protect healthcare workers. Dr. Hsien Yung Lai introduced an acrylic box (“aerosol box”) as a part of PPE during airway management. Since then, several companies and healthcare workers have made their own modified devices (“aerosol containment device”), and the use of such a device has spread worldwide, without being formally assessed for its effectiveness, efficacy and safety. Several simulation studies have indicated that “aerosol containment device” would make tracheal intubation more difficult. In addition, the device would prevent the spread of droplets from a patient, but may increase the risk of healthcare workers being exposed to a higher concentration of viral aerosols. Therefore, the current state of knowledge indicates that an “aerosol containment device” without vacuum mechanism has only limited efficacy in protecting healthcare workers from viral transmission.