Table 3.
Patient characteristics based on a difference between SpO2 and SaO2 < 5% or >= 5% at rest.
| Variables | SpO2 − SaO2 <5% mean ± SD, n (%) |
SpO2 − SaO2>=5% mean ± SD, n (%) |
P-value (t-test, chi-square) |
|---|---|---|---|
| n (%) | 577 (76.8) | 174 (23.2) | |
| Age (years) | 53 ±17 | 59 ±13 | <0.001 |
| Male gender | 271 (47.0) | 84 (48.3) | 0.84 |
| Height (cm) | 170.3 ±10.0 | 168.2 ±10.5 | 0.01 |
| Weight (kg) | 84.6 ±21.4 | 82.7 ±22.3 | 0.30 |
| BMI (kg/m2) | 29 ±7.0 | 29 ±6.8 | 0.88 |
| Smoking status | <0.001 | ||
| Current smoker | 20 (3.5) | 48 (27.6) | |
| Ex-smoker | 236 (41.0) | 71 (40.8) | |
| Never smoker | 319 (55) | 55 (31.6) | |
| Reason for CPET testing | <0.001 | ||
| Unexplained dyspnea | 447 (77.6) | 111(63.4) | |
| Pre-operative workup | 118 (20.5) | 62 (35.4) | |
| Exercise induced asthma | 3 (0.5) | 0 (0) | |
| Other | 7 (1.2) | 2 (1.1) | |
| FiO2 (%) | 0.48 | ||
| 21% | 563 (97.6) | 172 (98.8) | |
| 30 % | 14 (2.4) | 2 (1.2) | |
| ABG Parameters | |||
| pH | 7.43 ±0.03 | 7.42 ±0.03 | 0.018 |
| PaO2 (mmHg) | 90.0 ±10.9 | 80.6 ±10.1 | <0.001 |
| PaCO2 (mmHg) | 37.5 ±4.3 | 38.4 ±3.8 | 0.011 |
| HCO3 (mEq/L) | 24.1 ±2.2 | 24.3 ±1.9 | 0.29 |
| SaO2 (%) | 94.9 ±1.3 | 92.7 ±1.8 | <0.001 |
| Hemoglobin (g/dL) | 14.0 ±2.0 | 13.5 ±2.0 | 0.014 |
| Carboxyhemoglobin (%) | 1.31 ±0.46 | 2.07 ±1.50 | <0.001 |
| A-a gradient (mmHg) | 11.2 ±10.6 | 18.0 ±12.4 | <0.001 |
| Spirometry Parameters | |||
| FEV1 (L) | 2.7 ±0.9 | 2.3 ±0.9 | <0.001 |
| FEV1 (% of predicted) | 85.4 ±19.5 | 78.7 ±21.6 | <0.001 |
| FVC (L) | 3.5 ±1.1 | 3.26 ±1.1 | 0.01 |
| FVC (% of predicted) | 86.3 ±17.8 | 84.7 ±18.5 | 0.27 |
| Minute Ventilation (l/min) | 12.0 ±4.4 | 12.0 ±3.2 | 0.7 |
| CPET Parameters | |||
| Heart Rate (bpm) | 82 ±16 | 83 ±15 | 0.57 |
| Respiratory rate (rpm) | 17 ±5.2 | 18 ±4.5 | 0.11 |
| SpO2 (%) | 97.9 ±1.9 | 99.1 ±1.1 | <0.001 |
| Oxygen consumption (ml/min) | 321 ±91 | 312 ±84 | 0.24 |
| Oxygen consumption/Kg (ml/min/kg) | 3.9 ±0.9 | 3.9 ±0.9 | 0.91 |
| Oxygen pulse (ml/min/bpm) | 4.0 ±1.3 | 3.9 ±1.1 | 0.11 |
| End-tidal CO2 (mmHg) | 33.4 ±4.9 | 32.4 ±5.3 | 0.018 |
Abbreviations: Δ = Difference between, ABG = arterial blood gas; BMI = body mass index; CO2 = carbon dioxide; CPET = cardiopulmonary exercise testing; FEV1 = forced expiratory volume in one second; FiO2= inspired fraction of oxygen; FVC = forced vital capacity; HCO3 = bicarbonate; O2 = oxygen; PaO2 = partial pressure of oxygen; PaCO2 = partial pressure of carbon dioxide; SaO2 = arterial hemoglobin oxygen saturation; SpO2 = pulse oximetry; SD = standard deviation