Figures
- FIGURE 1
a) Overview of the test chamber, sensor locations (Sensirion, SPS30: mesh sensors: A-I, three sensors at 30 cm, three at 100 cm, two at 180 cm and one at 285 cm) (TSI, APS 3321: “breathing zone single sensor”: sample point 20 cm from participant face) and other equipment. The test person was seated on a chair, with an approximate breathing zone elevation of 120 cm above the floor. The sensors were positioned 120 cm above the floor. b) Protocol structure with oxygen modalities and event elements and details. Before and between each 10-min event a 15-min period of filtering out the particles of the test chamber was performed. LFNC: low-flow nasal cannula; HFNC: high-flow nasal cannula; NIV: noninvasive positive-pressure ventilation. HF: high flow; IPAP: inspiratory positive airway pressure; EPAP: expiratory positive airway pressure
- FIGURE 2
Average particles per litre of air (PPL) concentration over 10 min (red dot) between each of the eight events in each experiment, grouped according to participant (violin plots with two segment y-axes). a) Breathing-zone single sensor (particle size range 0.3–20 μm). b) average over nine mesh sensors (particle size range 0.3–10 μm). Categorical comparisons of average concentration of particles per litres of air, during the eight events of each experiment, with each red dot representing the results from 1 of 20 participants, measured by the breathing-zone single sensor (APS 3321) (c) and the average over all nine mesh sensors (d). The median is indicated with a thin black dashed line. LF: low-flow; C: cough; HF: high-flow; M: mask. e) Particle size distribution measured with the breathing-zone sensor; NIV: noninvasive positive-pressure ventilation.
- FIGURE 3
Mean and median particles per litre of air, from 20 participants, for three particle size groups, measured with the breathing-zone single sensor (APS 3321), during the eight events of the experiment. The median and means show smoothed time series (moving mean with a 3-s window). The smoothing was used to increase readability and instead of a series of spikes, a smoothed square-like step response is shown for the periods with large spikes. LFNC: low-flow nasal cannula; HFNC: high-flow nasal cannula; NIV: noninvasive positive-pressure ventilation.
- FIGURE 4
Mean particle concentration in particles per litre of air (y-axes) within each episode, for all mesh sensors. The particle concentration number includes particle sizes (0.3–10 μm). The placement of the plots within the graph is similar to the sensor position during the experiments, with the distance to each sensor shown in the subfigure headings. The distribution of measurements between participants is presented as violin plots, where the median is indicated with a thin black dashed line, and the quartiles with thinner dashed lines. LF: low-flow; C: cough; HF: high-flow; M: mask; NIV: noninvasive positive-pressure ventilation.
Tables
- TABLE 1
Descriptive statistics for particles measured in the breathing-zone of the test subject (30 cm from mouth)
Event Mean Min Max Median 0.25 0.75 Dispersion % Particle size ≤1.0 µm LFNC 73.0 21.2 151.0 60.9 41.5 106.5 107 LFNC+cough 222.7 44.9 1167.4 122.9 71.0 248.4 144 HFNC 101.2 15.9 317.1 67.8 38.5 130.0 135 HFNC+cough 190.9 36.4 1444.7 91.9 61.8 167.6 115 HFNC+M 89.3 25.3 230.5 54.8 41.0 137.2 176 HFNC+M+cough 103.1 29.2 270.5 96.7 48.2 156.5 112 NIV 77.7 20.6 245.9 66.4 33.3 102.4 104 NIV+cough 90.2 28.0 263.5 73.8 39.2 112.2 99 Particle size >1 µm and ≤5 µm LFNC 22.1 7.3 70.2 18.6 14.8 24.0 49 LFNC+cough 47.3 13.7 242.0 29.3 17.7 40.4 77 HFNC 42.4 1.8 236.7 25.7 14.9 46.0 121 HFNC+cough 41.8 13.3 186.4 25.0 21.4 37.7 65 HFNC+M 33.5 7.6 110.2 22.4 15.4 39.4 107 HFNC+M+cough 27.3 8.4 80.1 23.4 17.3 29.1 50 NIV 21.6 5.1 51.8 22.1 13.3 26.4 59 NIV+cough 24.7 6.0 72.7 21.6 16.3 31.2 69 Particle size >5 µm LFNC 1.7 0.5 5.5 1.2 0.9 2.1 100 LFNC+cough 1.7 0.3 5.5 1.4 1.0 1.8 57 HFNC 3.6 0.1 22.8 1.9 1.2 3.5 122 HFNC+cough 3.1 0.6 24.6 1.6 1.1 2.9 113 HFNC+M 3.7 0.4 20.5 1.7 1.1 3.9 167 HFNC+M+cough 2.6 0.8 9.8 1.9 1.2 2.9 88 NIV 1.3 0.3 2.5 1.3 0.9 1.8 65 NIV+cough 1.8 0.5 4.5 1.5 1.0 2.2 79 Descriptive statistics for the particle concentration (three particle size groups) measured by the breathing-zone single sensor (APS 3321) during all events. The unit used is the mean particle concentration in number per litre during the event. The dispersion of the distribution is presented as the per cent-wise ratio between the interquartile range and the median. The statistical distributions of particle counts were skewed for nearly all events and particle sizes (Shapiro–Wilk test p<0.05). LFNC: low-flow nasal cannula; HFNC: high-flow nasal cannula; NIV: noninvasive positive-pressure ventilation; M: surgical mask.
- TABLE 2
Statistical pairwise comparisons between events
Comparison Median difference Lower CI Upper CI p-value Particle size ≤1.0 µm HFNC−LFNC 9.5 −5.3 29.6 0.212 LFNC+cough−LFNC 42.9 8.9 108.5 0.005 HFNC+cough−HFNC 8.2 −3.4 31.3 0.145 HFNC+cough−LFNC+cough −12.1 −59.4 −0.2 0.184 HFNC−HFNC+M 6.7 −8.5 22.1 0.179 HFNC+cough−HFNC+M+cough 11.1 −10.9 35.4 0.126 HFNC+ M +cough−HFNC+ M 2.8 −7.0 14.6 0.332 NIV−LFNC −0.7 −4.8 14.2 0.904 NIV−HFNC −4.3 −30.3 7.4 0.204 NIV+cough−NIV 6.6 −14.5 16.0 0.455 LFNC+cough−NIV+cough 43.4 6.0 94.5 0.001 HFNC+cough−NIV+cough 28.2 6.4 43.2 0.023 Particle size >1 µm and ≤5 µm HFNC−LFNC 6.8 −0.3 16.6 0.073 LFNC+cough−LFNC 7.6 −0.5 16.6 0.048 HFNC+cough−HFNC 1.0 −10.9 5.7 0.765 HFNC+cough−LFNC+cough −1.4 −7.1 0.0 0.296 HFNC−HFNC+M 2.0 −4.6 13.4 0.391 HFNC+cough−HFNC+M+cough 2.6 −0.4 6.8 0.086 HFNC+ M +cough−HFNC+ M 1.6 −6.6 4.1 0.911 NIV−LFNC 2.5 −4.4 4.4 0.732 NIV−HFNC −5.5 −20.6 −0.2 0.057 NIV+cough−NIV 2.6 0.0 6.1 0.156 LFNC+cough−NIV+cough 7.1 −2.0 16.0 0.040 HFNC+cough−NIV+cough 4.3 −0.4 11.9 0.107 Particle size >5 µm HFNC−LFNC 0.5 0.3 0.9 0.044 LFNC+cough−LFNC 0.2 −0.4 0.4 0.862 HFNC+cough−HFNC −0.5 −0.6 0.1 0.204 HFNC+cough−LFNC+cough 0.3 −0.1 0.9 0.116 HFNC−HFNC+M 0.2 −0.6 0.7 0.926 HFNC+cough−HFNC+M+cough −0.4 −0.9 0.2 0.125 HFNC+ M +cough−HFNC+ M 0.1 −0.5 0.8 0.709 NIV−LFNC −0.3 −0.5 0.3 0.468 NIV−HFNC −0.8 −1.8 −0.2 0.009 NIV+cough−NIV 0.4 0.1 0.8 0.079 LFNC+cough−NIV+cough −0.2 −0.4 0.3 0.456 HFNC+cough−NIV+cough 0.1 −0.3 0.9 0.390 Statistical pairwise comparisons between different experimental events of particle concentrations (particles per litre of air) measured by the breathing-zone single sensor (APS 3321). Results from three particle size groups are shown. 95% confidence intervals of the median differences are based on the bootstrap method, and the p-values are based on the Wilcoxon signed rank test. LFNC: low-flow nasal cannula; HFNC: high-flow nasal cannula; NIV: noninvasive positive-pressure ventilation; M: surgical mask.
- TABLE 3
Estimates of change in particle concentrations over time
Event Fixed estimate Lower 95% CI Upper 95% CI Intercept p-value Particle size ≤1.0 µm LFNC 0.1 −0.5 0.7 72.4 0.721 LFNC+cough 27.3 −4.0 58.6 72.5 0.087 HFNC −2.5 −6.7 1.7 115.1 0.238 HFNC+cough 25.7 −16.6 68.1 49.4 0.232 HFNC+M −0.2 −2.2 1.9 90.3 0.862 HFNC+M+cough 4.4 −0.3 9.0 79.0 0.065 NIV −0.1 −0.7 0.5 78.2 0.743 NIV+cough 3.6 −0.1 7.4 70.2 0.059 Particle size >1 µm and ≤5 µm LFNC −0.8 −1.2 −0.5 26.7 <0.001 LFNC+cough 2.4 −4.2 8.9 34.2 0.474 HFNC −5.8 −13.2 1.5 74.5 0.120 HFNC+cough −1.2 −8.7 6.3 48.5 0.750 HFNC+M −2.6 −7.0 1.7 48.0 0.235 HFNC+M+cough −1.5 −2.9 0.0 35.4 0.049 NIV −1.2 −1.9 −0.4 28.2 0.002 NIV+cough 0.1 −1.9 2.1 24.2 0.929 Particle size >5 µm LFNC −0.1 −0.2 0.0 2.4 0.009 LFNC+cough −0.2 −0.3 −0.1 2.7 0.005 HFNC −0.6 −1.3 0.1 6.7 0.095 HFNC+cough −0.6 −1.5 0.3 6.4 0.180 HFNC+M −0.3 −1.1 0.5 5.4 0.440 HFNC+M+cough −0.3 −0.5 −0.2 4.5 <0.001 NIV −0.2 −0.3 −0.1 2.5 <0.001 NIV+cough −0.1 −0.2 0.0 2.3 0.084 Estimates of change in particle concentration (number/litre) per minute near the breathing-zone of the subjects for all events, based on measurements from the breathing-zone single sensor (APS 3321). Results from three particle size groups are shown. LFNC: low-flow nasal cannula; HFNC: high-flow nasal cannula; NIV: noninvasive positive-pressure ventilation; M: surgical mask.
- TABLE 4
Estimates of differences to intercept (30 cm) in mean particle concentration at different distances in the measurement chamber
Event 0.3 m (intercept) 1.0 m 1.8 m 2.85 m LFNC 218.2 (168.0–268.3) 22.9 (−23.1–68.8) −38.0 (−89.4–13.4) −14.6 (−79.6–50.4) LFNC+cough 400.2 (293.1–507.3) −20.3 (−84.2–43.6) −102.6 (−174.1–−31.1)* −100.9 (−191.3–−10.5)* HFNC 278.1 (219.2–337.0) −30.4 (−94.8–34.0) −34.8 (−106.8–37.2) −16.5 (−107.5–74.5) HFNC+cough 341.8 (258.6–425.0) 7.1 (−53.6–67.8) −99.5 (−167.3–−31.7)* −104.0 (−189.8–−18.2)* HFNC+M 210.5 (167.2–253.9) 79.1 (31.5–126.7)* 14.0 (−39.2–67.2) 25.0 (−42.3–92.4) HFNC+M+cough 303.4 (260.2–346.7) −31.0 (−92.2–30.2) −57.8 (−126.2–10.5) −71.3 (−159.4–16.8) NIV 222.8 (183.9–261.7) 35.3 (−19.8–90.3) −30.2 (−91.7–31.3) −20.4 (−98.2–57.42) NIV+cough 228.4 (181.6–275.3) 33.8 (−17.5–85.0) −43.0 (−100.3–14.2) 9.7 (−62.6–82.0) Estimates of differences in mean particle concentration (number/L) between mesh sensors at different distances from the breathing-zone of the subject based on a linear mixed-effects model. The particle concentration number includes particle sizes (0.3−10 µm). The intercept level at 30 cm is presented together with the differences (versus 30 cm) at 100 cm, 180 cm and 285 cm. 95% confidence intervals of all estimates are given in parentheses, and all differences (versus 30 cm) with a p-value <0.05 are marked with *. LFNC: low-flow nasal cannula; HFNC: high-flow nasal cannula; NIV: noninvasive positive-pressure ventilation; M=surgical mask.
Supplementary Material
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Supplementary material 00206-2021.SUPPLEMENT
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