A quantitative evaluation of aerosol generation from upper airway suctioning during tracheal intubation and extubation sequences.

Background: Open respiratory suctioning is considered to be an aerosol generating procedure (AGP) and laryngopharyngeal suction, used to clear secretions during anaesthesia, is widely managed as an AGP. It is uncertain whether such upper airway suctioning should be designated an aerosol generating procedure (AGP) because of a lack of both aerosol and epidemiological evidence of risk. Aim: To assess the relative risk of aerosol generation by upper airway suction during tracheal intubation and extubation in anaesthetised patients. Methods: Prospective environmental monitoring study in ultraclean operating theatres to assay aerosol concentration during intubation and extubation sequences including upper airway suctioning for patients undergoing surgery (n=19 patients). An Optical Particle Sizer (particle size 300nm-10μm) was used to sample aerosol 20cm above the mouth of the patient. Baseline recordings (background, tidal breathing and volitional coughs) were followed by intravenous induction of anaesthesia with neuromuscular blockade. Four periods of oropharyngeal suction were performed with a Yankauer sucker: pre-laryngoscopy, post-intubation and pre- and post-extubation. Findings: Aerosol from breathing was reliably detected (65[39-259] particles.L-1 (median[IQR])) above background (4.8[1-7] particles.L-1, p<0.0001 Friedman). The procedure of upper airway suction was associated with much lower average concentrations of aerosol than breathing (6.0[0-12] particles.L-1, P=0.0007) and was indistinguishable from background (P>0.99). The peak aerosol concentration recorded during suctioning (45[30-75] particles.L-1) was much lower than both volitional coughs (1520[600-4363] particles.L-1, p<0.0001, Friedman) and tidal breathing (540[300-1826] particles.L-1, p<0.0001, Friedman). Conclusion: The procedure of upper airway suction during airway management is associated with no higher concentration of aerosol than background and much lower than breathing and coughing. Upper airway suction should not be designated as a high risk AGP.

Nebulizer systems: a new frontier for therapeutics and targeted delivery

Drug delivery via the pulmonary route is a cornerstone in the pharmaceutical sector as an alternative to oral and parenteral administration. Nebulizer inhalation treatment offers multiple drug administration, easily employed with tidal breathing, suitable for children and elderly, can be adapted for severe patients and visible spray ensures patient satisfaction. This review discusses the operational and mechanical characteristics of nebulizer delivery devices in terms of aerosol production processes, their usage, benefits and drawbacks that are currently shaping the contemporary landscape of inhaled drug delivery. With the advent of particle engineering, novel inhaled nanosystems can be successfully developed to increase lung deposition and decrease pulmonary clearance. The above-mentioned advances might pave the path for treating a life-threatening disorder like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which is also discussed in the current state of the art.

Aerosolization of Mycobacterium tuberculosis by tidal breathing

Rationale: Interrupting tuberculosis (TB) transmission requires an improved understanding of how - and when - the causative organism, Mycobacterium tuberculosis (Mtb), is aerosolized. Although Cough is commonly assumed to be the dominant source of Mtb aerosols, recent evidence of Cough-independent Mtb release implies the contribution of alternative mechanisms. Objective: To compare the aerosolization of Mtb and particulate matter from GeneXpert-positive patients during three separate respiratory manoeuvres: Tidal Breathing (TiBr), Forced Vital Capacity (FVC), and Cough. Methodology: Bioaerosol sampling and Mtb detection were combined with real-time assessments of CO2 production and particle counts from 39 confirmed TB patients. Measurements and Main Results: TiBr and FVC produced comparable numbers of particles, with Cough producing >4-fold more. For all manoeuvres, the proportions of particles detected across size categories from 0.5 - 5 µm were similar, with minor differences observed only in particles between 1.5 - 2 µm (p = 0.014) and >5 µm (p = 0.020). Viable Mtb bacilli were detected in 66%, 70%, and 65% of TiBr, FVC, and Cough samples, respectively. Notably, while Cough produced 3-fold more Mtb than TiBr, the relative infrequency of coughing compared to breathing implies that TiBr likely contributes >90% of the daily aerosolised Mtb across a range of Cough frequencies. Conclusions: Our results suggest that, while Cough increases particle aerosolization compared to TiBr, this is not associated with increased Mtb aerosolization. Instead, TiBr produces more Mtb per particle than Cough. Assuming the number of viable Mtb organisms detected provides a proxy measure of patient infectiousness, these observations imply a significant contribution of TiBr to TB transmission.

Measurement of breathing in patients with post-COVID-19 using structured light plethysmography (SLP)

IntroductionCOVID-19 pandemic has had a huge impact on global health to date, with 5.6 million cases in the UK since its emergence. The respiratory symptoms largely mimic those of pneumonia’ with symptoms ranging from mild to severe. The effects on respiratory physiology are not yet fully understood, but evidence is emerging that there is much dysfunctional breathing reported but little information on tidal ventilation from the acute phase of the infection. Structured light plethysmography (SLP) is a contactless technique of respiratory function testing that measures tidal breathing parameters by assessing thoracoabdominal displacement.MethodsIn a postdischarge clinic, SLP was performed routinely on 110 hospitalised patients recovering from COVID-19 who had been screened for respiratory symptoms to confirm any respiratory changes occurring after the disease. Patients were categorised based on their hospital treatment in (1) the intensive therapy unit (ITU) (requiring intubation) (n=65) or (2) respiratory wards only (n=45). Data from these two patient cohorts were compared with preacquired data from healthy controls (n=30).ResultsWe have found a significantly increased respiratory rate (p=0.006) in ITU patients compared with the healthy cohort and also a significant decrease in the inspiratory time (p=0.01), expiratory time (p=0.005) and the total breathing cycle (p=0.008). There were no significant differences between ITU and ward patients and no significant differences in healthy compared with ward patients. We examined the variability of breathing (‘entropy’) both in terms of the breath-to-breath interval and the volume-to-volume change. The breath-to-breath interval alone was significantly lower in ITU patients compared with healthy cohorts (p=0.02).ConclusionOur findings suggest that abnormalities in tidal breathing can be detected in COVID-19 recovery patients, and SLP may be a promising tool in assessing the aftermath of diseases such as COVID-19, particularly if more intensive management strategies such as mechanical ventilation are required.

Wheezing Characteristics and Predicting Reactivity to Inhaled β2-Agonist in Children for Home Medical Care

Background: Given that wheezing is treated with inhaled β2-agonists, their effect should be reviewed before the condition becomes severe; however, few methods can currently predict reactivity to inhaled β2-agonists. We investigated whether preinhalation wheezing characteristics identified by lung sound analysis can predict reactivity to inhaled β2-agonists.Methods: In 202 children aged 10–153 months, wheezing was identified by auscultation. Lung sounds were recorded for 30 s in the chest region on the chest wall during tidal breathing. We analyzed the wheezing before and after β2-agonist inhalation. Wheezing was displayed as horizontal bars of intensity defined as a wheeze power band, and the wheezing characteristics (number, frequency, and maximum intensity frequency) were evaluated by lung sound analysis. The participants were divided into two groups: non-disappears (wheezing did not disappear after inhalation) and disappears (wheezing disappeared after inhalation). Wheezing characteristics before β2-agonist inhalation were compared between the two groups.The characteristics of wheezing were not affected by body size. The number of wheeze power bands of the non-responder group was significantly higher than those of the responder group (P &lt; 0.001). The number of wheeze power bands was a predictor of reactivity to inhaled β2-agonists, with a cutoff of 11.1. The 95% confidence intervals of sensitivity, specificity, and positive and negative predictive values were 88.8, 42, 44, and 81.1% (P &lt; 0.001), respectively.Conclusions: The number of preinhalation wheeze power bands shown by lung sound analysis was a useful indicator before treatment. This indicator could be a beneficial index for managing wheezing in young children.

A quantitative evaluation of aerosol generation during manual facemask ventilation

SummaryManual facemask ventilation, a core component of elective and emergency airway management, is classified as an aerosol generating procedure. This designation is based on a single epidemiological study suggesting an association between facemask ventilation and transmission from the SARS 2003 outbreak. 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 with neuromuscular blockade. Recordings were made in ultraclean theatres and compared against the aerosol generated by the patient’s own tidal breathing and coughs. Respiratory aerosol from tidal breathing was reliably detected above the very low background particle concentrations (191 (77-486 [3.8-1313]) versus 2.1 (0.7-4.6 [0-12.9] particles.l-1 median(IQR)[range], n=11, p=0.002). The average aerosol concentration detected during facemask ventilation both without a leak (3.0 particles.l-1 (0 – 9 [0-43])) and with an intentional leak (11 particles.l-1 (7.0 – 26 [1-62])) was 64-fold and 17-fold lower than that of tidal breathing (p=0.001 and p=0.002 respectively). The peak particle concentration during facemask ventilation both without a leak (60 particles.l-1 (0 – 60 [0-120])) and with a leak (120 particles.l-1 (60 – 180 [60-480]) were respectively 20-fold and 10-fold lower than a cough (1260 particles (800 – 3242 [100-3682]), p=0.002 and p=0.001 respectively). This study demonstrates that facemask ventilation, even performed with an intentional leak, does not generate high levels of bioaerosol. On the basis of this evidence, facemask ventilation should not be considered an aerosol generating procedure.

Methacholine Challenges: comparison of different tidal breathing challenge methods

Tidal breathing methacholine challenges are now recommended by guidelines, to avoid the bronchoprotective effects of deep inhalation. This study compared different tidal breathing methacholine challenge methods, assessed the agreement between tidal dosimetric and continuous output challenges, and challenge repeatability with different methods. 15 asthma patients performed dosimetric challenges and a continuous output breath actuated challenge, all at least 3 days apart. All subjects had a pre-bronchodilator forced expired volume in 1 s (FEV1) ≥65% predicted, and PD20 <1.2 mg. Of the dosimetric challenges, one method increased methacholine concentration (standard dosimetric challenge), and one adjusted nebuliser output time to increase dose (adjusted dosimetric challenge). The adjusted dosimetric and continuous output challenges were performed twice on separate days to assess for repeatability. All challenges were matched for dose at each dose step. The mean PD20 ratio of the standard dosimetric challenge to the adjusted dosimetric challenge was 0.90 (CI: 0.66–1.23; p=0.49), and intraclass correlation coefficient (ICC)=0.82. Repeated adjusted dosimetric challenges had an ICC=0.62 for PD20. Repeated continuous output challenges had an ICC =0.74 for PD20. The adjusted dosimetric and continuous output challenges correlated (r=0.69, p=0.0043; ICC: 0.65), but PD20 was higher for the adjusted dosimetric challenge (mean PD20 ratio=2.31; CI: 1.57–3.40; p=0.0004). Tidal dosimetric methacholine challenge using adjustment of nebuliser output produces results with good repeatability. The results of this adjusted dosimetric method differed from the continuous output method, underscoring that the results of different methacholine challenge methodologies may not be directly comparable.

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

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