TABLE 1.
Alterations of lung function tests in idiopathic pulmonary fibrosis (IPF)
| Mild IPF | Moderate to severe IPF | |
| Spirometry | ||
| FVC | Normal | Decreased |
| FEV1/FVC | Normal or increased | Normal or increased |
| Static lung volumes | ||
| TLC | Normal | Decreased |
| FRC | Normal | Decreased |
| Blood gases at rest | ||
| PaO2 | Normal | Decreased |
| PaCO2 | Normal | Decreased |
| Carbon monoxide transfer | ||
| DLCO | Decreased | Decreased |
| VA | May be normal | Decreased |
| KCO | May be normal | Decreased |
| Airways | ||
| Cough reflex | Increased | Increased |
| Airway resistance | Decreased | Decreased |
| Pulmonary haemodynamics at rest | ||
| PAP | May be increased | Frequently increased |
| PCWP | Normal | May be increased |
| Ventilatory drive | ||
| P0.1 | May be normal | Increased |
| Ventilatory response to CO2 rebreathing | Normal | Normal |
| Exercise physiology | ||
| Peak V′O2 | May be normal | Decreased |
| VD/VT | Increased | Increased |
| V′E/V′CO2 | Increased | Increased |
| PAP at exercise | Increased | Increased |
| PA–aO2 at exercise | Increased | Increased |
FVC: forced vital capacity; FEV1: forced expiratory volume in 1 s; TLC: total lung capacity; FRC: functional residual capacity; PaO2: arterial oxygen tension; PaCO2: arterial carbon dioxide tension; DLCO: diffusing capacity of the lung for carbon monoxide; VA: alveolar volume; KCO: transfer constant of carbon monoxide; PAP: pulmonary artery pressure; PCWP: pulmonary capillary wedge pressure; P0.1: 100 ms occlusion pressure; V′O2: oxygen uptake; VD/VT: ratio of dead space volume to tidal volume; V′E/V′CO2: ratio of minute ventilation to carbon dioxide elimination; PA–aO2: alveolar–arterial oxygen tension difference.