Figures
- FIGURE 1
Chartis measurement screen image showing the actual flow and the “volume trend for the previous 20 s” (VT20) plotted for a collateral ventilation (CV) negative patient phenotype in the right upper lobe. This assessment reached VT20=6 mL at the 2 min 16 s mark, whereas the total measurement was 3 min 36 s.
- FIGURE 2
Chartis measurement screen image showing the actual flow and the “volume trend for the previous 20 s” (VT20) plotted for a collateral ventilation (CV) positive patient phenotype. This assessment never reaches a VT20 value below VT20=23 mL.
- FIGURE 3
Distribution of minimum “volume trend for the previous 20 s” (VT20) values in collateral ventilation (CV) negative and CV positive measurements.
- FIGURE 4
Distribution of “time saved” between “volume trend for the previous 20 s” (VT20)=6 mL and total measurement in collateral ventilation (CV) negative patients.
- FIGURE 5
Chartis measurement output image showing the “volume trend for the previous 20 s” (VT20) value plotted for an assessment with continued high spikes in air flow (flow of 72 mL·min−1 at 5:22 min) values for the duration of the assessment. These spikes cause confounding peak flow trend values, while the VT20 is a good indicator of the continued decline in the amount of total exhaled volume. The VT20 is 6 mL at 5:22 min, whereas the total measurement was 9:14 min (difference: 232 s).
Tables
- TABLE 1
Selection criteria for valid Chartis measurements to calculate the optimal VT20 threshold
1. Presence of positive flow prior to start of assessment. 2. The flow should be consistent.
• This flow may be decreasing over the course of the assessment, but there should be no extended duration of missing flow. This indicates proper catheter balloon positioning and sealing of the airways and that the catheter has not been clogged.
• There should be no sudden increases in flow to a much higher level. This could indicate that the catheter balloon seal was lost.
• During the assessment, if there is an instantaneous loss or drop in flow within the first 30 s and flow does not resume, the assessment should be abandoned and a new one should be re-initiated.3. At the end of the assessment, the total volume of air exhaled by the patient during the assessment should have been >50 mL. - TABLE 2
Results of Chartis assessment: duration of measurement and expiratory volume during measurement
Total CV negative CV positive p-value Subjects n 249 187 62 Duration of Chartis assessment Total time, s 240 (77–864) 226 (77–864) 304 (122–533) 0.021 Time to VT20=6 mL, s 168 (36–546) Difference, s 60 (5–354) Expiratory volume during Chartis assessment Expiratory volume, mL 320 (15–1780) 240 (15–983) 1014 (115–1780) p<0.005 Expiratory volume at VT20=6 mL, mL 235 (11–991) Difference, mL 5 (0–120) Values are presented as median (range) unless otherwise indicated. CV: collateral ventilation; VT20: “volume trend for the previous 20 s”.
