3 - ARF and Need for MV

acute respiratory failure (ARF)

inability of cardiovascular system to maintain adequate gas exchange at pulmonary level

acute respiratory insufficiency (ARI)

gas exchange is maintained at expense of increased cardiopulmonary work

• can lead to ARF

hypoxic failure (lung/oxygenation failure)

lung disease causes ineffective alveolar gas exchange (V/Q mismatch) or low diffusion

• ↓P_aO₂

• ↑P_A-aO₂

• ↓P_aCO₂ (usually)

hypercapnic failure (pump/ventilation failure)

hypoventilation causing CO₂ retention

• ↑P_aCO₂

• normal P_A-aO₂

causes of hypercapnic failure

• ventilatory muscle fatigue

• extrapulmonary restriction

• neuromuscular dysfunction

• CNS depression

general indications for ventilatory support

• apnea

• acute ventilatory failure

• severe hypoxemia unresponsive to simpler measures

specific indications for ventilatory support

• NIF/MIP/PIP

> −20 cmH₂O

specific indications for ventilatory support

• PEP

< 40 cmH₂O

specific indications for ventilatory support

• VC

< 10 mL/kg IBW

specific indications for ventilatory support

• V_T

< 5 mL/kg IBW

specific indications for ventilatory support

• RR/f

< 8 or > 20 b/min

specific indications for ventilatory support

• C_stat

< 25 mL/cmH₂O

specific indications for ventilatory support

• FEV₁

< 10 mL/kg

specific indications for ventilatory support

• pH

< 7.35 (critical: < 7.25)

specific indications for ventilatory support

• P_aCO₂

> 45 mmHg and not compensated by HCO₃^-

specific indications for ventilatory support

• V_D/V_T

> 60%

specific indications for ventilatory support

• V_E

< 5 or > 10 L/min

specific indications for ventilatory support

• P_aO₂

< 80 mmHg on F_iO₂ ≥ 60%

specific indications for ventilatory support

• P_A-aO₂

> 300

specific indications for ventilatory support

• P_aO₂/P_AO₂

< 0.15

specific indications for ventilatory support

• P_aO₂/F_iO₂

< 200

specific indications for ventilatory support

• Q_S/Q_T

> 20%