Carbon Dioxide Rebreathing Research Articles

Prior self-control exertion decreases pre-frontal cortex oxygenation during a CO2rebreathing challenge but does not affect perceptions of dyspnoea or tolerance time.

Dyspnoea perception is influenced by a complex interplay of physiological, psychological, and environmental factors. Recently, we showed that males with high trait self-control experience less dyspnoea and persist for longer in a carbon dioxide (CO2) rebreathing challenge than males with low trait self-control. As self-control can also vary within individuals (state self-control), the primary aim of the present study was to investigate whether prior self-control exertion influenced perceptions of dyspnoea and tolerance of a CO2 rebreathing challenge in healthy young males. We also used functional near-infrared spectroscopy (fNIRS) to assess haemodynamic activity of the pre-frontal cortex (PFC) which is a region of interest (ROI) in dyspnoea research, and the primary brain region associated with exertion of self-control. In a within-subjects design, fifteen healthy young males completed an easy (congruent) Stroop task (control condition) and a difficult (incongruent) Stroop task (prior self-control exertion, experimental condition) followed by a CO2 rebreathing challenge until the limit of tolerance. Changes in oxyhaemoglobin (ΔO2Hb) and deoxyhaemoglobin (ΔHHb) were assessed continuously in the Stroop task and CO2 rebreathing challenge. During the CO2 rebreathing challenge, dyspnoea intensity and unpleasantness were rated every 30s. Prior self-control exertion did not affect perceptions of dyspnoea or tolerance time in the CO2 rebreathing challenge (all P > 0.05). ΔO2Hb from baseline was higher in the left (+38%) and right (+44%) pre-frontal cortices during the difficult Stroop task than the easy Stroop task (both P < 0.05). During the subsequent CO2 rebreathing challenge, ΔO2Hb was attenuated following prior self-control exertion in the left PFC. Although prior self-control exertion decreased pre-frontal cortex oxygenation during a subsequent CO2 rebreathing challenge, there was no change in tolerance time or perceptions of dyspnoea.

Automatic detection of CO2 rebreathing during BiPAP ventilation

Carbon dioxide rebreathing (CO2 rebreathing) significantly influences respiratory drive and the work of breathing during BiPAP ventilation. We analyzed CO2 movement during BiPAP ventilation to find a method of real time detection of CO2 rebreathing without the need of CO2 concentration measurement sampled from the circuit (method expensive and not routinely used). Observational study during routine care in 15 bed university hospital ICU. At 18 patients who required BiPAP ventilation, intubated or during noninvasive ventilation, during weaning period airflow, pressure and CO2 concentration signals were registered on both sides of venting port and 17 respiratory parameters were measured or calculated for each of 4747 respiratory cycles analyzed. Based on CO2 movement (expiration–inspiration sequences) 3 types of cycle were identified, type I and II do not induce rebreathing but type III does. To test differences between the 3 types ANOVA, t-tests, and canonical discriminant analysis (CDA) were used. Then a multilayer perceptron (MLP) network, a type of artificial neural network, using the above parameters (excluding CO2 concentration) was applied to automatically identify the three types of respiratory cycles. Of the 4747 respiratory cycles, 1849 were type I, 1545 type II, and 1353 type III. ANOVA and t-tests showed significant differences between the types of respiratory cycles. CDA confirmed a correct apportionment of 93.9% of the cycles; notably, of 97.9% of type III. MLP automatically classified the respiratory cycles into the three types with 98.8% accuracy. Three types of respiratory cycles could be distinguished based on CO2 movement during BiPAP ventilation. Artificial neural networks can be used to automatically detect respiratory cycle type III, the only inducing CO2 rebreathing.

Oxygenation and Carbon Dioxide Rebreathing of a Well-fitting Non-rebreathing EcoLite™ Mask with a Reservoir: A Single-center Prospective Observational Study in Healthy Volunteers.

The fitting of oxygen mask affects the performance of it such as oxygenation or CO₂ elimination. The intersurgical EcoLite™ adult high-concentration oxygen mask (EcoLite with a reservoir, Intersurgical, UK) was developed to give well-fitting. The purpose of this study is to evaluate the performance of EcoLite with a reservoir compared to the conventional mask. Ten healthy volunteers were included in this study. EcoLite with a reservoir and conventional mask were given to patients at different oxygen flow rates (5, 8, 10, 12, and 15 L/min). Fraction of inspiratory O₂ (FIO₂) and partial pressure of inspiratory CO₂ (PICO₂) were measured by a sampling tube at the middle pharynx inserted via nose. The EcoLite with a reservoir had a significantly higher FIO₂ than the control reservoir mask. However, the PICO₂ was significantly higher in the EcoLite with a reservoir than in the control reservoir mask, especially when the oxygen flow rate was low. The EcoLite with a reservoir provided improved oxygenation and a better fit than the conventional reservoir masks in healthy volunteers. However, the EcoLite with a reservoir might cause higher CO₂ rebreathing at low oxygen flow rates.

Circuit-dependent carbon dioxide rebreathing during continuous positive airway pressure

BackgroundThe current standard treatment for obstructive sleep apnea (OSA), continuous positive airway pressure (CPAP), is characterized by a low adherence rate due to various factors including circuit-dependent carbon dioxide (CO2) rebreathing, which can exacerbated by disparate factors, such as low PAP, use of auto-titrating PAP or ramps. However, risk factors for rebreathing are often overlooked or poorly understood in clinical practice. Therefore, our objective was to evaluate the extent of rebreathing occurring with commonly used CPAP masks across varying PAPs, tidal volumes, and respiratory rates. MethodsIn a bench study, we assessed the rebreathing rate of nine masks interfacing a CPAP with a lung simulator providing different breathing respiratory rates (15 or 20 breaths/min) and tidal volumes (400, 500, 600, 700 and 750 mL). Additionally, a theoretical model was developed to describe the likelihood of CO2 rebreathing from four different masks at various breathing settings. ResultsOverall, all masks performed worse in situations characterized by low PAPs, high tidal volumes, and high respiratory rates. However, Dreamwear, Nuance, Siesta, Vitera, and particularly V2 masks exhibited greater susceptibility to rebreathing compared to F20, P10, Brevida, and Rio masks for the same variations of PAPs or ventilatory parameters. The mathematical model suggested that the risk of rebreathing for Rio, P10 and Nuance mask is negligible for respiratory rates of 10 breaths/min or below. ConclusionsCircuit-dependent CO2 rebreathing can be a common occurrence and warrants careful mask selection upon CPAP therapy initiation for optimal clinical outcomes.

Comparison of electrical impedance tomography and spirometry-based measures of airflow in healthy adult horses.

Electrical impedance tomography (EIT) is a non-invasive diagnostic tool for evaluating lung function. The objective of this study was to compare respiratory flow variables calculated from thoracic EIT measurements with corresponding spirometry variables. Ten healthy research horses were sedated and instrumented with spirometry via facemask and a single-plane EIT electrode belt around the thorax. Horses were exposed to sequentially increasing volumes of apparatus dead space between 1,000 and 8,500mL, in 5-7 steps, to induce carbon dioxide rebreathing, until clinical hyperpnea or a tidal volume of 150% baseline was reached. A 2-min stabilization period followed by 2minutes of data collection occurred at each timepoint. Peak inspiratory and expiratory flow, inspiratory and expiratory time, and expiratory nadir flow, defined as the lowest expiratory flow between the deceleration of flow of the first passive phase of expiration and the acceleration of flow of the second active phase of expiration were evaluated with EIT and spirometry. Breathing pattern was assessed based on the total impedance curve. Bland-Altman analysis was used to evaluate the agreement where perfect agreement was indicated by a ratio of EIT:spirometry of 1.0. The mean ratio (bias; expressed as a percentage difference from perfect agreement) and the 95% confidence interval of the bias are reported. There was good agreement between EIT-derived and spirometry-derived peak inspiratory [-15% (-46-32)] and expiratory [10% (-32-20)] flows and inspiratory [-6% (-25-18)] and expiratory [5% (-9-20)] times. Agreement for nadir flows was poor [-22% (-87-369)]. Sedated horses intermittently exhibited Cheyne-Stokes variant respiration, and a breath pattern with incomplete expiration in between breaths (crown-like breaths). Electrical impedance tomography can quantify airflow changes over increasing tidal volumes and changing breathing pattern when compared with spirometry in standing sedated horses.

Response: Rebreathing of carbon dioxide during noninvasive ventilation. Is PEEP the final solution?

Response: Rebreathing of carbon dioxide during noninvasive ventilation. Is PEEP the final solution?

Rebreathing of carbon dioxide during non-invasive ventilation. Is PEEP the final solution?

Rebreathing of carbon dioxide during non-invasive ventilation. Is PEEP the final solution?

Potential rebreathing of carbon dioxide during noninvasive ventilation provided by critical care ventilator

BackgroundCritical care ventilators are frequently used to provide noninvasive ventilation (NIV) support to critically ill patients. Questions remain regarding carbon dioxide (CO2) clearance while using a critical care ventilator and dual limb circuit with various patient interfaces. The purpose of this study is to determine the positive end expiratory pressure (PEEP) level required to effectively washout CO2 for full-face and oronasal masks when using a dual limb circuit.MethodThis randomized crossover trial was conducted at an academic medical center in the Midwest United States. After obtaining informed consent, eight healthy volunteers were placed on a 980 Puritan Bennett (Medtronic, Minneapolis, MN) ventilator operating in the NIV mode. All subjects performed 20 min of breathing on four levels of PEEP (0, 2, 4, and 5 cm H2O) and pressure support of 5 cm H2O. NIV settings were applied to four masks (two oronasal and two full-face masks) that were randomly selected with a 5-min washout period between each mask. The fraction of inspired carbon dioxide (FICO2) was sampled/monitored with a nasal cannula using a Capnostream 20p monitor (Medtronic, Minneapolis, MN) and reported as percentages. A Kruskal–Wallis test was used to reveal significant differences across PEEP levels. Pairwise comparisons of the groups were made using Mann–Whitney tests with a family-wise error correction.ResultsMedian (IQR) FICO2 was significantly lower 0.0% (0%–0.92%) at PEEP of 5 compared to 1.83% (0.66%–4.0%; p < 0.001) at PEEP of 0 or 1.0% (0.33%–2.66%; p = 0.002) at PEEP of 2. FICO2 was significantly lower 0.5% (0%–1.92%) at PEEP of 4 compared to PEEP of 0 (p = 0.001).ConclusionA PEEP level of at least 5 cm H2O associated with the reported leak was required to minimize the likelihood of CO2 rebreathing while using a critical care ventilator to provide NIV with a double limb circuit and full-face or oronasal masks.

Blood gas levels, cardiovascular strain and cognitive performance during surgical mask and filtering face piece application

Mask induced airway resistance and carbon dioxide rebreathing is discussed to impact gas exchange and to induce discomfort and impairments in cognitive performance. N = 23 healthy humans (13 females, 10 males; 23.5 ± 2.1 years) participated in this randomized crossover trial (3 arms, 48-h washout periods). During interventions participants wore either a surgical face mask (SM), a filtering face piece (FFP2) or no mask (NM). Interventions included a 20-min siting period and 20 min steady state cycling on an ergometer at 77% of the maximal heart rate (HR). Hemodynamic data (HR, blood pressure), metabolic outcomes (pulse derived oxygen saturation, capillary carbon dioxide (pCO2), and oxygen partial pressure (pO2), lactate, pH, base excess), subjective response (ability to concentrate, arousal, perceived exertion) and cognitive performance (Stroop Test) were assessed. Compared to NM, both masks increased pCO2 (NM 31.9 ± 3.3 mmHg, SM = 35.2 ± 4.0 mmHg, FFP2 = 34.5 ± 3.8 mmHg, F = 12.670, p < 0.001) and decreased pH (NM = 7.42 ± 0.03, SM = 7.39 ± 0.03, FFP2 = 7.39 ± 0.04, F = 11.4, p < 0.001) during exercise. The FFP2 increased blood pressure during exercise (NM = 158 ± 15 mmHg, SM = 159 ± 16 mmHg, FFP2 = 162 ± 17 mmHg, F = 3.21, p = 0.050), the SM increased HR during sitting (NM = 70 ± 8 bpm, SM = 74 ± 8 bpm, FFP2 = 73 ± 8 bpm, F = 4.70, p = 0.014). No mask showed any comparative effect on other hemodynamic, metabolic, subjective, or cognitive outcomes. Mask wearing leads to slightly increased cardiovascular stress and elevated carbon dioxide levels during exercise but did not affect cognitive performance or wellbeing.

Thermal Rebreathing Model for Evaluation of Infant Bedding Materials

Abstract Carbon dioxide (CO2) rebreathing is a recognized hazard, particularly for infants. A new thermal rebreathing method and apparatus have been developed for measuring and comparing the degree to which various soft bedding materials perform with respect to this hazard. The new methodology simplifies the evaluation process and uses less costly equipment than the incumbent expensive and complex CO2 rebreathing model. Using warm air as a proxy for CO2, it relies on a highly sensitive differential thermometer to measure air temperature differences that correlate to the level of rebreathing. The apparatus is portable and requires neither the use of a gas analyzer nor a source of CO2. Test results comparing the two methods show strong correlation validating the new thermal concept. The availability of a simple CO2 rebreathing method and apparatus will promote quantitative evaluation of this hazard among a wider group of users, including infant product developers and manufacturers. Additional studies are suggested to further develop the thermal rebreathing model.

A Strategy to Enhance Confidence in Respiratory Chemoreflex Characterization by Modified Rebreathing

Modelling breath‐by‐breath ventilation (V̇E) in response to carbon dioxide rebreathing in hyperoxic and hypoxic conditions (modified rebreathing) is used to characterize the central and peripheral respiratory chemoreflexes in humans. However, breath‐to‐breath variability produces uncertainty in the estimation of model parameters. We explored whether signal‐averaging of repeated rebreathing trials would improve chemoreflex sensitivity parameter estimation and confidence. Seven healthy males (age: 27±5 years) performed 6 repetitions of modified rebreathing tests in isoxic‐hypoxic (end‐tidal PO2 (PETO2)=50 mmHg) and ‐hyperoxic conditions (PETO2=150 mmHg) over the course of 4 days. End‐tidal PCO2 (PETCO2), PETO2 and V̇E were measured breath‐by‐breath by dual gas analyser and pneumotach. The slope of the V̇E vs PETCO2 relationship above the PETCO2 threshold in the hyperoxic test gave the central chemoreflex sensitivity (L∙min‐1∙mmHg‐1) and the difference in hypoxic versus hyperoxic test slopes provided peripheral chemoreflex sensitivity. Chemoreflex slopes modelled from a single trial versus ensemble‐average of 6 trials were compared by paired t‐test and effect size (Cohen’s d). Breath‐by‐breath data from the 6 trials were aligned to the same starting PETCO2, linearly interpolated to 0.1 mmHg of PETCO2, ensemble‐averaged, and averaged into 0.2 mmHg bins. Central chemoreflex sensitivity did not differ (p=0.94) between single (4.10±2.98 L∙min‐1∙mmHg‐1, 95%CI: 3.82–4.39) versus ensemble‐averaged data (4.13±2.14 L∙min‐1∙mmHg‐1, 95%CI: 3.99–4.27) but the 95%CI was reduced (p=0.031) by 0.29 L∙min‐1∙mmHg‐1 (effect size=1.5) with the ensemble‐averaged approach. Similarly, peripheral chemoreflex sensitivity did not differ (p=0.83) between single (1.69±1.14 L∙min‐1∙mmHg‐1, 95%CI: 1.54–1.84) versus ensemble‐averaged data (1.58±1.32 L∙min‐1∙mmHg‐1, 95%CI: 1.5 –1.66); 95%CI of the ensemble‐averaged data was 0.15 L∙min‐1∙mmHg‐1 lower than a single trial but this was not different (p=0.38; effect size=0.5). Signal averaging of multiple modified rebreathing trials reduces the confidence interval of respiratory chemoreflex sensitivity. This strategy could enhance the ability to detect differences in respiratory chemoreflex control in comparative or interventional studies where modified rebreathing is used.

The effect of a ketamine constant rate infusion on cardiovascular variables in sheep anesthetized at the minimum alveolar concentration of sevoflurane that blunts adrenergic responses.

To evaluate the effect of a constant rate infusion of ketamine on cardiac index (CI) in sheep, as estimated using noninvasive cardiac output (NICO) monitoring by partial carbon dioxide rebreathing, when anesthetized with sevoflurane at the previously determined minimum alveolar concentration that blunts adrenergic responses (MACBAR). 12 healthy Dorset-crossbred adult sheep. Sheep were anesthetized 2 times in a balanced placebo-controlled crossover design. Anesthesia was induced with sevoflurane delivered via a tight-fitting face mask and maintained at MACBAR. Following induction, sheep received either ketamine (1.5 mg/kg IV, followed by a constant rate infusion of 1.5 mg/kg/h) or an equivalent volume of saline (0.9% NaCl) solution (placebo). After an 8-day washout period, each sheep received the alternate treatment. NICO measurements were performed in triplicate 20 minutes after treatment administration and were converted to CI. Blood samples were collected prior to the start of NICO measurements for analysis of ketamine plasma concentrations. The paired t test was used to compare CI values between groups and the ketamine plasma concentrations with those achieved during the previous study. Mean ± SD CI of the ketamine and placebo treatments were 2.69 ± 0.65 and 2.57 ± 0.53 L/min/m2, respectively. No significant difference was found between the 2 treatments. Mean ketamine plasma concentration achieved prior to the NICO measurement was 1.37 ± 0.58 µg/mL, with no significant difference observed between the current and prior study. Ketamine, at the dose administered, did not significantly increase the CI in sheep when determined by partial carbon dioxide rebreathing.

The Cardiopulmonary Effects of Medical Masks and Filtering Facepiece Respirators on Healthy Health Care Workers in the Emergency Department: A Prospective Cohort Study

BackgroundInternational COVID-19 guidelines recommend that health care workers (HCWs) wear filtering facepiece (FFP) respirators to reduce exposure risk. However, there are concerns about FFP respirators causing hypercapnia via rebreathing carbon dioxide (CO2). Most previous studies measured the physiological effects of FFP respirators on treadmills or while resting, and such measurements may not reflect the physiological changes of HCWs working in the emergency department (ED). ObjectiveOur aim was to evaluate the physiological and clinical impacts of FFP type II (FFP2) respirators on HCWs during 2 h of their day shift in the ED. MethodsWe included emergency HCWs in this prospective cohort study. We measured end-tidal CO2 (ETCO2), mean arterial pressure (MAP), respiratory rate (RR), and heart rate values and dyspnea scores of subjects at two time points. The first measurements were carried out with medical masks while resting. Subjects then began their day shift in the ED with medical mask plus FFP2 respirator. We called subjects after 2 h for the second measurement. ResultsThe median age of 153 healthy volunteers was 24.0 years (interquartile range 24.0–25.0 years). Subjects’ MAP, RR, and ETCO2 values and dyspnea scores were significantly higher after 2 h. Median ETCO2 values increased from 36.4 to 38.8 mm Hg. None of the subjects had hypercapnia symptoms, hypoxia, or other adverse effects. ConclusionWe did not observe any clinical reflection of these changes in physiological values. Thus, we evaluated these changes to be clinically insignificant. We found that it is safe for healthy HCWs to wear medical masks plus FFP2 respirators during a 2-h working shift in the ED.

Physiological effects of providing supplemental air for avalanche victims. A randomised trial

BackgroundSurvival from avalanche burial is dependent on time to extraction, breathing ability, air pocket oxygen content, and avoiding rebreathing of carbon dioxide (CO2). Mortality from asphyxia increases rapidly after burial. Rescue services often arrive too late. Our objective was to evaluate the physiological effects of providing personal air supply in a simulated avalanche scenario as a possible concept to delay asphyxia. We hypothesize that supplemental air toward victim’s face into the air pocket will prolong the window of potential survival. MethodsA prospective randomized crossover experimental field study enrolled 20 healthy subjects in Hemsedal, Norway in March 2019. Subjects underwent in randomized order two sessions (receiving 2 litres per minute of air in front of mouth/nose into the air pocket or no air) in a simulated avalanche scenario with extensive monitoring serving as their own control. ResultsA significant increase comparing Control vs Intervention were documented for minimum and maximum end-tidal CO2 (EtCO2), respiration rate, tidal volume, minute ventilation, heart rate, invasive arterial blood pressures, but lower peripheral and cerebral oximetry. Controls compared to Intervention group subjects had a lower study completion rate (26% vs 74%), and minutes in the air pocket before interruption (13.1 ± 8.1 vs 22.4 ± 5.6 vs), respectively. ConclusionsParticipants subject to simulated avalanche burial can maintain physiologic parameters within normal levels for a significantly longer period if they receive supplemental air in front of their mouth/nose into the air pocket. This may extend the time for potential rescue and lead to increased survival.

The physical effects of wearing personal protective equipment: a scoping review

Background: The COVID-19 pandemic has required healthcare workers to wear personal protective equipment (PPE), and although there is increasing awareness of the physical effects of wearing PPE, the literature has yet to be synthesised around this topic. Methods: A scoping review was conducted to synthesise existing literature on the physical effects of wearing PPE and identify gaps in the literature. A comprehensive search strategy was undertaken using five databases from 1995 to July 2020. Results: A total of 375 relevant articles were identified and screened. Twenty-three studies were included in this review. Studies were conducted across 10 countries, spanning 16 years from 2004 to 2020. Half (13/23) were randomised controlled trials or quasi-experimental studies, five surveys, two qualitative studies, two observational or case series and one Delphi study. Most (82%, 19/23) studies involved the N95 mask (either valved or unvalved). None specifically studied the filtering facepiece 3 mask. The main physical effects relate to skin irritation, pressure ulcers, fatigue, increased breathing resistance, increased carbon dioxide rebreathing, heat around the face, impaired communication and wearer reported discomfort. Few studies examined the impact of prolonged wear (akin to real life practice) on the physical effects, and different types of PPE had different effects. Conclusions: The physical effects of wearing PPE are not insignificant. Few studies examined the physiological impact of wearing respiratory protective devices for prolonged periods whilst conducting usual nursing activity. No ideal respirators for healthcare workers exist, and the development of more ergonomic designs of PPE is required.

Safe sleep after 1 year of age.

Safe sleep after 1 year of age.

Superiority of OxyMaskTM with less carbon dioxide rebreathing in children.

Despite the growing importance of oxygen-delivery devices worldwide, there are only a few reports of physiological data on various oxygen masks in children. The possibility of carbon dioxide (CO2) rebreathing has been a prevalent concern with the use of oxygen-delivery devices. OxyMask KidTM (Southmedic Inc. Canada; hereafter OxyMask) is expected to reduce CO2 rebreathing even at low oxygen flow rates because of its structural features. Biological data using OxyMask in children have not been well investigated. Measured respiratory parameters of OxyMask with those of a simple oxygen mask in healthy children were compared. Ten subjects were enrolled, with a median age of 5.4 years. All subjects used both OxyMask and a simple oxygen mask. The fraction of inspiratory oxygen (FIO2), partial pressure of inspiratory CO2 (PICO2), and partial pressure of end-tidal CO2 were measured using a sidestream gas-sampling monitor in all subjects. The oxygen flow rate was set at 1, 3, 5, and 10 L/min. FIO2 levels were higher with OxyMask than those with the simple oxygen mask at 3 L/min of oxygen. PICO2 levels were significantly lower with OxyMask than those with the simple oxygen mask (1.5 mmHg vs. 3.7 mmHg at 1 L/min, P = 0.005; 1.0 mmHg vs. 2.7 mmHg at 3 L/min, P = 0.005, respectively), whereas PICO2 levels were higher at low oxygen flow rates with both masks.Conclusion: Our results showed that higher FIO2 and less CO2 rebreathing were achieved with OxyMask than those with a simple oxygen mask at low flow rates of oxygen in healthy children. What is Known: • OxyMask is expected to reduce carbon dioxide rebreathing even at low oxygen flow rates because of its structural features. • Efficacy has been demonstrated in experimental models and adult data, but clinical data on the use of the OxyMask in children are limited. What is New: • Higher fraction of inspiratory oxygen and lesser carbon dioxide rebreathing were achieved with OxyMask than with a simple oxygen mask at low flow rates of oxygen in healthy children.

Nano-based Masks, Disinfectants and Sanitizers Effectively Combat Covid-19

COVID-19 is an infectious viral disease caused by novel coronavirus to SARS-CoV-2 which emerged from Wuhan, China at the end of year 2019. The World Health Organization (WHO) declared COVID-19 a global pandemic due to highly contagious nature of SARS-CoV-2. Till date COVID-19 has infected and claimed lives of millions of people around the world. The virus is mainly transmitted through droplets from symptomatic patients; however, there are many cases of infection from asymptomatic people, wherein the virus is transmitted even before the symptoms appear. Therefore, it has been strategized to control the spread of virus from one person to another. Moreover, inadequate medical facilities, high cost of treatment and lack of effective medication against novel COVID-19, non-pharmacological interventions (NPIs) can help mitigate the transmission such as wearing face masks, face shields, protective clothing and practicing social distancing. However, these standard protective equipment (PE) are not effective in preventing the spread of coronavirus. Meanwhile, nano-based products are of huge help in effectively preventing COVID-19 outbreak.&#x0D; Face-mask is a cost effective first line of defense against COVID-19 as mask helps prevent the entry of small sized particles. However, commonly used facial masks are incapable of preventing the entry of small sized corona virus, which gets stuck in mask and can live on it for up to 9 days. Moreover, if such mask worn for longer period of time, virus can enter inside the body via mouth and nasal passage. Therefore, masks should be designed such that they are effective, antiviral and comfortable to use. Recently a research showed that nanoceutical N95 mask made with Zinc Oxide nanoflower cotton fabrics were comfortable, washable, porous and light-weight which solved the common problem of carbon dioxide rebreathing and prevented the spread of virus through the pores.&#x0D; Nanotechnology also offers a lot of opportunities for the development of more effective and promising disinfectant systems. In Prague, nano-polymer disinfectants were sprayed on few public vehicles to check its efficiency. It was found that Nano-polymer disinfectant can work for almost 21 days as compared to traditional disinfectants. Moreover, it was also found that copper nanoparticles incorporated disinfectants could be really effective against COVID-19. Coronavirus estimated half-life on stainless steel is 5.6h and on plastics 6.8h therefore copper can be used to inactivate virus. Additionally, the efficiency of hand sanitizers could also be enhanced by introducing nanoparticles like copper, silver, gold, and quaternary ammonium cations (QUATs) due to their antiviral properties. These metals and metal oxides can be used to create a surface coating to protect the body against the covid-19 because they possess the ability to stops the binding of viral proteins with human epithelial cells and leads to the viral protein denaturation. Scaling-up these for commercial use could help in effectively preventing COVID-19 spread. These various available nano-based products help equip people for combating COVID-19.&#x0D; Dr. Humera Kausar&#x0D; Associate Professor&#x0D; Kinnaird College for Women University&#x0D; Lahore, Pakistan

Low flow nasal oxygen supplementation in addition to non-rebreathing mask: An alternative to high flow nasal cannula oxygenation for acute hypoxemic COVID-19 patients in resource limited settings

Approximately 14% COVID-19 patients, develop acute hypoxic respiratory failure. A high flow nasal cannula device might be preferred to obtain an oxygen saturation above 90% in these cases. In resource limited settings, where high flow nasal cannula is not an option, additional low flow oxygen therapy through nasal prongs could be added to non-rebreathing mask with a reservoir bag. The possible mechanisms of the improved oxygenation could be: 1. improved oxygen-air mixing in large airways, 2. increased oxygen concentration inside the non-rebreathing mask, 3. decrease in rebreathing of carbon-dioxide from the non-rebreathing mask. This method of oxygen supplementation is easy to assemble, cost-effective and helpful in management of acute hypoxemic COVID-19 patients, whenever there is crisis of high flow nasal cannula machine. Its effectiveness needs to be assessed by a randomized controlled trial.

Facemasks simple but powerful weapons to protect against COVID-19 spread: Can they have sides effects?

In the last few months, the spread of COVID-19 among humans has caused serious damages around the globe letting many countries economically unstable. Results obtained from conducted research by epidemiologists and virologists showed that, COVID-19 is mainly spread from symptomatic individuals to others who are in close contact via respiratory droplets, mouth and nose, which are the primary mode of transmission. World health organization regulations to help stop the spread of this deadly virus, indicated that, it is compulsory to utilize respiratory protective devices such as facemasks in the public. Indeed, the use of these facemasks around the globe has helped reduce the spread of COVID-19. The primary aim of facemasks, is to avoid inhaling air that could contain droplets with COVID-19. We should note that, respiration process is the movement of oxygen from external atmosphere to the cells within tissue and the transport of carbon dioxide outside. However, the rebreathing of carbon dioxide using a facemask has not been taken into consideration. The hypercapnia (excess inhaled content of CO2) has been recognized to be related to symptoms of fatigue, discomfort, muscular weakness, headaches as well as drowsiness. Rebreathing of CO2 has been a key to concern regarding the use of a facemask. Rebreathing usually occur when an expired air that is rich in CO2 stays long than normal in the breathing space of the respirator after a breath. The increase of the arterial CO2 concentration leads to symptoms that are aforementioned. Studies have been conducted on facemask shortages and on the appropriate facemask required to reduce the spread of COVID-19; however no study has been conducted to assess the possible relationship between CO2 inhalation due to facemask, to determine and recommend which mask is appropriate in the reduction of the spread of the coronavirus while simultaneously avoid CO2 inhalation by the facemask users. In the current paper, we provided a literature review on the use of facemasks with the aim to determine which facemasks could be used to avoid re-inhaling rejected CO2. Additionally, we presented mathematical models depicting the transport of COVID-19 spread through wind with high speed. We considered first mathematical models for which the effect air-heterogeneity is neglected, such that air flow follows Markovian process with a retardation factor, these models considered two different scenarios, the speed of wind is constant and time–space dependent. Secondly, we assumed that the wind movement could follow different processes, including the power law process, fading memory process and a two-stage processes, these lead us to use differential operators with power law, exponential decay and the generalized Mittag-Leffler function with the aim to capture these processes. A numerical technique based on the Lagrange polynomial interpolation was used to solve some of these models numerically. The numerical solutions were coded in MATLAB software for simulations. The results obtained from the mathematical simulation showed that a wind with speed of 100 km/h could transport droplets as far as 300 m. The results obtained from these simulations together with those presented by other researchers lead us to conclude that, the wind could have helped spread COVID-19 in some places around the world, especially in coastal areas. Therefore, appropriate facemasks that could help avoid re-inhaling enough CO2 should be used every time one is in open air even when alone especially in windy environment.