Table 4.
Patient characteristics based on a difference between SpO2 and SaO2 < 5% or >= 5% at peak exercise.
| Variables | SpO2 − SaO2 <5% mean ± SD, n (%) |
SpO2 − SaO2 >=5% mean ± SD, n (%) |
P-value (t-test, chi-square) |
|---|---|---|---|
| n (%) | 553 (87.6) | 78 (12.4) | |
| Age (years) | 54 ±16 | 61 ±14 | 0.001 |
| Male gender | 276 (49.9) | 32 (41.0) | 0.178 |
| Height (cm) | 170.7 ±10.0 | 166.1 ±9.3 | <0.001 |
| Weight (kg) | 85.9 ±21.4 | 79.0 ±21.3 | 0.007 |
| BMI (kg/m2) | 29.4 ±6.8 | 28.5 ±7.0 | 0.12 |
| Smoking status | <0.001 | ||
| Current smoker (%) | 29 (5.3) | 21 (26.9) | |
| Ex-smoker (%) | 235 (42.6) | 39 (50.0) | |
| Never smoker (%) | 299 (52.2) | 18 (23.1) | |
| Reason for CPET testing | |||
| Unexplained dyspnea | 424 (78.2) | 49 (55.1) | |
| Pre-operative workup | 110 (20.3) | 38 (42.7) | |
| Exercise induced asthma | 2 (0.4) | 0 (0) | |
| Other | 5 (0.9) | 2 (2.2) | |
| FiO2 (%) | 1.00 | ||
| 21% | 542 (98.0) | 76 (97.4) | |
| 30% | 11 (2.0) | 2 (2.6) | |
| ABG Parameters | |||
| pH | 7.35 ±0.05 | 7.35 ±0.05 | 0.494 |
| PaO2 (mmHg) | 100.2 ±15.9 | 81.8 ±15.0 | <0.001 |
| PaCO2 (mmHg) | 34.0 ±5.8 | 36.8 ±5.7 | <0.001 |
| HCO3 (mEq/L) | 18.5 (5.0 | 20.0 ±3.3 | 0.011 |
| SaO2 (%) | 94.9 (2.2 | 91.4 ±4.0 | <0.001 |
| Hemoglobin (g/dL) | 15.0 (4.3 | 14.0 ±2.0 | 0.026 |
| Carboxyhemoglobin (%) | 1.14 ±0.59 | 1.85 ±1.37 | <0.001 |
| A-a gradient (mmHg) | 17.8 ±13.2 | 32.0 ±13.7 | <0.001 |
| Spirometry Parameters | |||
| FEV1 (L) | 2.7 ±1.0 | 2.1 ±1.1 | <0.001 |
| FEV1(% change) | -1.1 ±19.8 | -8.0 ±31.8 | 0.009 |
| FVC (L) | 3.5 ±1.3 | 2.8 ±1.4 | 0.002 |
| FVC (% change) | -1.3 ±19.6 | -8.6 ±31.7 | 0.005 |
| Minute ventilation (l/min) | 71.0 ±25.0 | 62.0 ±22.4 | <0.001 |
| CPET Parameters | |||
| Heart rate (bpm) | 142 ±26 | 132 ±24 | <0.001 |
| Respiratory rate (rpm) | 42 ±10 | 42 ±10 | 0.98 |
| SpO2 (%) | 97.0 ±3.2 | 97.8 ±3.0 | 0.041 |
| Oxygen consumption (ml/min) | 1813 ±629 | 1387 ±519 | <0.001 |
| Oxygen consumption/kg (ml/min/kg) | 22.0 ±9.0 | 18.2 ±7.0 | <0.001 |
| Oxygen pulse (ml/min/bpm) | 12.8 ±4.0 | 10.6 ±3.4 | <0.001 |
| End-tidal CO2 (mmHg) | 32.5 ±5.3 | 32.0 ±4.7 | 0.639 |
Abbreviations: 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