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Table 2 Respiratory effects related to increased IAP

From: Ventilation in patients with intra-abdominal hypertension: what every critical care physician needs to know

1. Effects on respiratory mechanics (Diaphragm elevation)
 Intra-thoracic pressure ↑
 • Pleural pressure ↑
 • Peak airway pressure ↑ (volume controlled)
 • Mean airway pressure ↑
 • Plateau airway pressure ↑
 Respiratory system compliance ↓
 • Chest wall compliance ↓
 • Lung compliance =
 • Lung volumes ↓ (pressure controlled)
 Functional residual capacity (FRC) ↓
 Compression atelectasis ↑
 Pulmonary vascular resistance ↑
 Lower inflection point on PV curve ↑
2. Effects on gas exchange (Reduced gas exchange)
 Hypercarbia ↑
 Oxygenation ↓
 • Dead-space ventilation ↑
 • Intra-pulmonary shunt ↑
 • Ventilation perfusion mismatch ↑
 • Alveolar oedema ↑
3. Clinical effects (Difficult weaning)
 Oxygen consumption ↑
 Metabolic cost and work of breathing ↑
4. Biological effects
 Activated lung neutrophils (experimental) ↑
 Pulmonary inflammatory infiltration (experimental) ↑