Question

What are the methods to optimize FRC before and under general anaesthesia?

Hint:

Remember that optimizing FRC before and during anaesthesia helps prevent complications like atelectasis. Pre-oxygenation and PEEP are simple yet effective methods to improve FRC.

Answer 1

Step 1: Optimization of FRC before anaesthesia.
Before anaesthesia, various strategies can be employed to optimize FRC:
- Pre-oxygenation: Administering 100% oxygen for a few minutes before induction can help increase FRC by replacing nitrogen with oxygen, thereby improving oxygen reserves.
- Positioning: Positioning the patient in a semi-recumbent or head-up position can help to expand the chest and improve FRC.
- Positive end-expiratory pressure (PEEP): Using PEEP in mechanically ventilated patients can help to maintain FRC by preventing alveolar collapse at the end of exhalation.

Step 2: Optimization of FRC under general anaesthesia.
During general anaesthesia, the following methods are used to optimize FRC:
- Use of PEEP: As mentioned, PEEP helps to maintain FRC by preventing the collapse of small airways and alveoli.
- Optimal tidal volume: Using low tidal volumes (6-8 ml/kg) with appropriate inspiratory flow rates helps maintain lung volume and oxygenation.
- Recruitment manoeuvres: Periodic deep breaths or sustained inflation can help "recruit" collapsed alveoli and improve FRC during anaesthesia.
- Atelectasis prevention: Avoiding excessive muscle relaxant doses and using anaesthetic agents that do not depress the respiratory drive excessively can help prevent atelectasis and maintain FRC.

Step 3: Conclusion.
The optimization of FRC is crucial in improving oxygenation and preventing atelectasis during general anaesthesia. Pre-oxygenation, proper positioning, and the use of PEEP are some of the key strategies that can be used.