Table 2.
Participant characteristics (N = 400)*
| General characteristics | N (%)* | |
| Age, years | ||
| Mean (SD) | 64.2 (15.2) | |
| Min to max | 18.7 to 95.1 | |
| Male gender | 212 (53) | |
| Smoking status (n = 399) | ||
| Current | 43 (10.8) | |
| Ex | 203 (50.9) | |
| Never | 153 (38.5) | |
| Fitzpatrick Score | ||
| I | 44 (11) | |
| II | 198 (49.5) | |
| III | 127 (31.8) | |
| IV | 30 (7.5) | |
| V | 1 (0.3) | |
| VI | 0 (0) | |
| Conditions associated with chronic respiratory failure | ||
| None: | 229 (57.3) | |
| Hypercapnia** on ABG | 16 | |
| At least one: | 171 (42.8) | |
| Hypercapnia** on ABG | 57 | |
| Individual conditions associated with chronic respiratory failure | ||
| Chronic obstructive pulmonary disease | 113 (28.3) | |
| Obesity hypoventilation syndrome | 30 (7.5) | |
| Bronchiectasis | 19 (4.8) | |
| Cystic fibrosis | 1 (0.3) | |
| Neuromuscular disease | 24 (6) | |
| Chest wall deformity | 11 (2.8) | |
| Peripheral vascular disease | 11 (2.8) | |
| Diabetes | 80 (20) | |
| Oxygen administration | 25 (6.3) | |
| New Zealand Ethnicity | ||
| NZ European | 280 (70.0) | |
| Māori | 26 (6.5) | |
| Samoan | 13 (3.3) | |
| Chinese | 1 (0.3) | |
| Indian | 4 (1.0) | |
| Cook Island Māori | 1 (0.3) | |
| Tongan | 3 (0.8) | |
| Other | 28 (7.0) | |
| Australian Ethnicity | ||
| Caucasian | 34 (8.5) | |
| Middle Eastern | 6 (1.5) | |
| Other | 5 (1.3) | |
| Hospital location | ||
| Outpatient | 341 (85.3) | |
| Ward | 40 (10) | |
| HDU | 18 (4.5) | |
| ED | 1 (0.3) | |
| ABG and oximetry data | Mean (SD), min-max* | Median (IQR) |
| SpO2, % | 93.5 (3.8), 72 to 100 | 94 (92 to 96) |
| Participants with SpO2<90% (N, (%)) | 49 (12.3) | |
| Concern with SpO2 data accuracy recorded by investigator (N, (%))*** | 16 (4.0) | |
| SaO2, % | 94.7 (3.8), 72.1 to 100 | 95.7 (93.2 to 97.1) |
| Participants with SaO2<90% (N, (%)) | 35 (8.8) | |
| PaO2, mmHg | 74.8 (21.3), 37.9 to 396 | 73 (64.7 to 83) |
| Participants with PaO2<60 mmHg (N, (%)) | 61 (15.3) | |
| PaCO2, mmHg | 40.3 (7.2), 25.4 to 87.2 | 39 (35.8 to 43.4) |
| Hb, g/L | 136.7 (18.8), 67 to 192 | 137 (126.5 to 149) |
| CoHb, % | ||
| All participants (N = 358) | 2.1 (1.2), 0 to 7 | 1.8 (1.4 to 2.3) |
| Current smokers (N = 40) | 3.9 (1.7), 0.9 to 6.7 | 4.0 (2.4 to 5.4) |
| Ex smokers (N = 183) | 1.9 (0.9), 0.0 to 7.0 | 1.7 (1.4 to 2.2) |
| Never smokers (N = 135) | 1.9 (0.7), 0.0 to 4.2 | 1.7 (1.3 to 2.3) |
ABG: Arterial blood gas, CoHb: Carboxyhaemoglobin, COPD: Chronic Obstructive Pulmonary Disease, ED: Emergency Department, Hb: Haemoglobin, HDU: High Dependency Unit, ILD: Interstitial lung disease, NZ: New Zealand, NMD: Neuromuscular disease, OSA/OHS: Obstructive sleep apnoea and/or obesity hypoventilation syndrome, PaCO2: Partial pressure of arterial carbon dioxide, PaO2: Arterial partial pressure of oxygen, SaO2: Oxygen saturation measured by arterial blood gas sample, SpO2: Oxygen saturation measured by standard pulse oximeter
*Unless otherwise stated
**PaCO2 > 45 mmHg
***For example nail polish, acrylic nail, nail pathology, low perfusion or variability noted on monitor
Further details available in Online Additional File, including oximeter models and ABG analysers used (Additional file 1: Table S1)