Correction: Reusable snorkel masks adapted as particulate respirators.

[This corrects the article DOI: 10.1371/journal.pone.0249201.].

Reusable snorkel masks adapted as particulate respirators.

INTRODUCTION: During viral pandemics, filtering facepiece (FFP) masks together with eye protection form the essential components of personal protective equipment (PPE) for healthcare workers. There remain concerns regarding insufficient global supply and imperfect protection offered by currently available PPE strategies. A range of full-face snorkel masks were adapted to accept high grade medical respiratory filters using bespoke-designed 3D-printed connectors. We compared the protection offered by the snorkel to that of standard PPE using a placebo-controlled respirator filtering test as well as a fluorescent droplet deposition experiment. Out of the 56 subjects tested, 42 (75%) passed filtering testing with the snorkel mask compared to 31 (55%) with a FFP3 respirator mask (p = 0.003). Amongst the 43 subjects who were not excluded following a placebo control, 85% passed filtering testing with the snorkel versus to 68% with a FFP3 mask (p = 0.008). Following front and lateral spray of fluorescence liquid particles, the snorkel mask also provided superior protection against droplet deposition within the subject's face, when compared to a standard PPE combination of FFP3 masks and eye protection (3.19x108 versus 6.81x108 fluorescence units, p<0.001). The 3D printable adaptors are available for free download online at https://www.ImperialHackspace.com/COVID-19-Snorkel-Respirator-Project/. CONCLUSION: Full-face snorkel masks adapted as particulate respirators performed better than a standard PPE combination of FFP3 mask and eye protection against aerosol inhalation and droplet deposition. This adaptation is therefore a promising PPE solution for healthcare workers during highly contagious viral outbreaks.

Exercise ventilatory irregularity can be quantified by approximate entropy to detect breathing pattern disorder.

BACKGROUND: Breathing pattern disorder (BPD) is a prevalent cause of exertional dyspnea and yet there is currently no reliable objective measure for its diagnosis. We propose that statistical analysis of ventilatory irregularity, quantified by approximate entropy (ApEn), could be used to detect BPD when applied to cardiopulmonary exercise test (CPET) data. We hypothesised that ApEn of ventilatory variables (tidal volume (VT), breathing frequency (Bf), minute ventilation (VE)) would be greater, i.e. more irregular, in patients with BPD than healthy controls. METHODS: We evaluated ventilatory ApEn in 20 adults (14 female) with exertional dyspnoea, undergoing CPET and independently diagnosed with BPD by a specialist respiratory physiotherapist. Data were compared with 15 age- gender- and BMI-matched controls. ApEn for VT, Bf and VE were calculated for an incremental cycle exercise test. RESULTS: Patients with BPD more frequently rated breathlessness as the reason for exercise limitation and had a lower mean (SD) peak oxygen uptake compared with controls: 80 (18) vs. 124 (27) % predicted (P < 0.001). ApEn was significantly greater for VT (p = .006) and VE (p = .002) in BPD than controls. ApEn VE was inversely related (r2 = 0.24, p = .03) to peak oxygen uptake in BPD but not controls. ROC analysis revealed that ApEn VE > 0.88, conferred a sensitivity and specificity of 70% and 87% respectively, for detection of BPD. CONCLUSIONS: Non-linear statistical interrogation of CPET-acquired ventilatory data has utility in the detection of BPD. A simple calculation of approximate entropy of ventilation, during an incremental cardiopulmonary exercise test, provides a quantitative method to detect BPD.

Angiotensin-Converting Enzyme Inhibition as an Adjunct to Pulmonary Rehabilitation in Chronic Obstructive Pulmonary Disease.

RATIONALE: Epidemiological studies in older individuals have found an association between the use of angiotensin-converting enzyme (ACE) inhibition (ACE-I) therapy and preserved locomotor muscle mass, strength, and walking speed. ACE-I therapy might therefore have a role in the context of pulmonary rehabilitation (PR). OBJECTIVES: To investigate the hypothesis that enalapril, an ACE inhibitor, would augment the improvement in exercise capacity seen during PR. METHODS: We performed a double-blind, placebo-controlled, parallel-group randomized controlled trial. Patients with chronic obstructive pulmonary disease, who had at least moderate airflow obstruction and were taking part in PR, were randomized to either 10 weeks of therapy with an ACE inhibitor (10 mg enalapril) or placebo. MEASUREMENTS AND MAIN RESULTS: The primary outcome measurement was the change in peak power (assessed using cycle ergometry) from baseline. Eighty patients were enrolled, 78 were randomized (age 67 ± 8 years; FEV1 48 ± 21% predicted), and 65 completed the trial (34 on placebo, 31 on the ACE inhibitor). The ACE inhibitor-treated group demonstrated a significant reduction in systolic blood pressure (Δ, -16 mm Hg; 95% confidence interval [CI], -22 to -11) and serum ACE activity (Δ, -18 IU/L; 95% CI, -23 to -12) versus placebo (between-group differences, P < 0.0001). Peak power increased significantly more in the placebo group (placebo Δ, +9 W; 95% CI, 5 to 13 vs. ACE-I Δ, +1 W; 95% CI, -2 to 4; between-group difference, 8 W; 95% CI, 3 to 13; P = 0.001). There was no significant between-group difference in quadriceps strength or health-related quality of life. CONCLUSIONS: Use of the ACE inhibitor enalapril, together with a program of PR, in patients without an established indication for ACE-I, reduced the peak work rate response to exercise training in patients with chronic obstructive pulmonary disease.