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Mechanical Ventilation and Obesity
- Obesity is defined as a BMI of 30 - 34.99 kg/m2, with class II obesity defined as 35 - 39.9 kg/m2 and extreme obesity as > 40 kg/m2
- In obese patients:
- oxygen consumption is increased with a high proportion going to the work of breathing
- lung volumes are abnormal with reduced expiratory reserve
- the alveolar - arterial oxygen difference is increased
- respiratory system compliance is markedly reduced
- These changes are futher exacerbated in the supine position
- To overcome the effects of reduced compliance, higher levels of PEEP are generally needed
- In addition, higher plateau pressures may be necessary to achieve adequate tidal volumes
References
Lapinsky SE, Posadas-Calleja JG, McCullagh I. Clinical review: Ventilatory strategies for obstetric, brain-injured, and obese patients. Crit Care 2009;13:206.