Table 4. Actions of continuous positive airway pressure in CHF.
| Scenario | Acute pulmonary oedema | OSA | CSA-CSR |
|---|---|---|---|
| Upper airway | |||
| Pneumatic splinting | + | +++ | + |
| Pulmonary | |||
| Overcome negative ITP | + | +++ | + |
| Increase lung volume | ++ | ++ | ++ |
| Prevent alveolar collapse | +++ | + | ++ |
| Improve VQ matching | +++ | + | ++ |
| Reduce pulmonary vasoconstriction | +++ | + | ++ |
| Assist inspiratory muscles | +++ | + | ++ |
| Cardiac | |||
| Afterload reduction | |||
| Less negative ITP | + | +++ | + |
| Fall in systemic BP | + | ++ | ++ |
| Reduced LV diameter | + | ++ | ++ |
| Preload reduction | ++ | + | + |
Three common scenarios: +, a slight effect; ++, a moderate effect; +++, a major effect. CHF, congestive heart failure; OSA, obstructive sleep apnea; CSA-CSR, central sleep apnoea with cheyne stokes respiration; ITP, intrathoracic pressure; VQ, ventilation perfusion.