Target Alveolar Ventilation During Sleep for a 66-inch Tall Female
For a 66-inch tall female with normal BMI and no respiratory conditions, the appropriate target alveolar ventilation during sleep should be based on a tidal volume of 6-8 mL/kg of ideal body weight, which translates to approximately 300-400 mL per breath at a normal sleeping respiratory rate. 1
Calculation of Target Tidal Volume
- For a 66-inch tall female, the ideal body weight can be calculated using standard formulas, resulting in approximately 50-55 kg 1
- Using the recommended tidal volume of 6-8 mL/kg of ideal body weight, the target tidal volume during sleep should be approximately 300-440 mL 1
- This range accounts for the normal reduction in tidal volume during sleep, which typically decreases to about 73% of waking values 2
Normal Sleep Respiratory Parameters
- During sleep, minute ventilation naturally decreases compared to wakefulness (from approximately 7.66 L/min while awake to 7.18 L/min in non-REM sleep and 6.46 L/min in REM sleep) 2
- The breathing pattern during sleep is typically more rapid and shallow than during wakefulness 2
- Mean inspiratory flow rate (VT/Ti), an index of inspiratory drive, is significantly lower in REM sleep than during wakefulness or non-REM sleep 2
Monitoring and Adjustment Considerations
- When monitoring alveolar ventilation during sleep, it's important to maintain normal PCO2 levels, with an acceptable goal being a value less than or equal to the awake PCO2 1
- If using non-invasive positive pressure ventilation (NPPV), pressure support should be adjusted if the tidal volume falls below the acceptable goal of 6-8 mL/kg of ideal body weight 1
- Respiratory rate during sleep typically ranges from 12-15 breaths per minute, with a recommended inspiratory time between 30-40% of the respiratory cycle 1
Clinical Pitfalls to Avoid
- Avoid using actual body weight instead of ideal body weight when calculating target tidal volumes, as lung size correlates better with height than with actual weight 3
- Be aware that excessive ventilation can lead to sleep disruption and arousals, with significant individual variability in the reduction in ventilation that can be tolerated before having arousals 4
- Recognize that ventilation requirements differ between REM and non-REM sleep, with REM sleep typically requiring lower minute ventilation 2
- Monitor for signs of hypoventilation during sleep, as this can lead to hypercapnia and hypoxemia, particularly during REM sleep 2
By targeting this range of alveolar ventilation based on ideal body weight and accounting for normal sleep physiology, optimal gas exchange can be maintained while minimizing the risk of sleep disruption.