Table 2.
Baseline parameters according to nicotine-session, nicotine-free-session, and stop-session
| Nicotine-Session1 | Nicotine-Free-Session2 | Stop-Session3 | P1 vs. 3 | P2 vs. 3 | P1 vs. 2 | |
|---|---|---|---|---|---|---|
| E-cigarette use biomarkers | ||||||
| Serum propylene glycol by GC-FID, mmol/L† | 0.1 [0–0.15] | 0.09 [0–0.14] | 0 [0–0] | <0.001 | <0.001 | 0.19 |
| Serum propylene glycol by 1H-NMR, AUC | 0.07 [0.04–0.12] | 0.12 [0.03–0.16] | 0.01 [0–0.05] | 0.003 | 0.008 | 0.752 |
| Urine propylene glycol by 1H-NMR, AUC† | 1 [0.4–1.8] | 0.9 [0.6–2.2] | 0.2 [0.1–0.2] | <0.001 | <0.001 | 0.698 |
| Serum nicotine, ng/mL† | 3.9 [1.7–8.2] | 0 [0–0.7] | 0 [0–0] | 0.001 | 0.366 | <0.001 |
| Urine cotinine > 600 ng/mL, %‡ | 100 | 11 | 0 | 0.001 | 0.246 | <0.001 |
| Fraction exhaled carbon monoxide | 4 [3–5] | 4.5 [3–5.8] | 3.5 [3–5] | 0.217 | 0.087 | 0.622 |
| Respiratory parameters | ||||||
| Peripheral pulse oximetry, %* | 96.3 ± 0.4 | 96.2 ± 0.4 | 95.7 ± 0.5 | 0.006 | 0.016 | 0.672 |
| Transcutaneous oxygen tension, mmHg* | 76.1 ± 1.9 | 76 ± 1.7 | 75.3 ± 2.2 | 0.435 | 0.37 | 0.915 |
| Transcutaneous carbon dioxide tension, mmHg* | 37.1 ± 0.5 | 37.2 ± 0.5 | 37.9 ± 0.6 | 0.109 | 0.255 | 0.606 |
| End-tidal carbon dioxide, mmHg* | 37.7 ± 0.4 | 38.1 ± 0.5 | 37.7 ± 0.7 | 0.633 | 0.807 | 0.446 |
| Respiratory rate, min−1* | 15 ± 1 | 15 ± 1 | 15 ± 1 | 0.628 | 0.647 | 0.97 |
| Hemodynamic parameters | ||||||
| Heart rate, beats/min* | 66 ± 2 | 63 ± 1 | 63 ± 2 | <0.001 | 0.851 | <0.001 |
| Humeral systolic blood pressure, mmHg* | 117 ± 3 | 116 ± 3 | 115 ± 3 | 0.497 | 0.602 | 0.863 |
| Humeral diastolic blood pressure, mmHg* | 79 ± 2 | 78 ± 2 | 77 ± 2 | 0.242 | 0.545 | 0.547 |
| Cutaneous blood flow | ||||||
| Skin microcirculatory blood flow, PU* | 14 ± 2 | 13 ± 1 | 12 ± 1 | 0.958 | 0.55 | 0.496 |
| Cutaneous vascular conductance, PU/mmHg* | 0.15 ± 0.02 | 0.15 ± 0.01 | 0.14 ± 0.01 | 0.8 | 0.515 | 0.345 |
| Pneumoproteins | ||||||
| Serum CC16, µg/L† | 7.6 [6.1–9.4] | 6.5 [5.2–9.4] | 8.1 [6.8–10.3] | 0.011 | 0.004 | 0.685 |
| Serum SP-D, µg/L† | 97 [69–140] | 107 [81–146] | 105 [73–138] | 0.768 | 0.164 | 0.252 |
| Urine CC16/urine creatinine, ng/mg† | 12.6 [9–26.6] | 18.1 [10–32.2] | 16.4 [7.7–36.1] | 0.062 | 0.745 | 0.103 |
1
H-NMR, nuclear magnetic resonance spectroscopy; AUC, area under the curve; CC16, club cell protein-16; GC-FID, gas chromatography with a flame ionization detector; PU, perfusion unit (arbitrary unit); SP-D, surfactant protein-D.
*
The data are the mean ± SE;
†
The data are the median [interquartile range];
‡
Categorical variables were studied using the chi-square test.