• The closing capacity (CC) is the volume in the lungs at which the alveoli collapse
• The closing capacity appears to correlate with asthma severity, hypoxemia, and atelectas

The formula utilized in this calculation is:

• CC=CV+RV

Abbreviations used:

• CC=Closing capacity
• RV=Residual Volume (Liters)
• CV=Closing Volume (Liters)

Interpretation:

One study by in't Veen, et al., found that CC increased in the patients with difficult-to-controlasthma as compared with the group with stable asthma:

• Difficult-to-control Asthma: 114.0 ± 6.4
• Stable Asthma: 99.9 ± 3.6

Bevan et al., found that if the closing capacity (CC) exceeded functional residual capacity (FRC) it can cause hypoxemia in pregnant woman.

Hedenstierna found that Atelectasis can occur in patients where closing capacity (CC) exceeded functional residual capacity (FRC).

Another study by Torchio R , et al., found CC was greater than functional residual capacity [FRC]) in most patients with chronic heart failure (CHF) but was absent in control subjects.

References

Bevan DR, et al. Closing volume and pregnancy. Br Med J. 1974 Jan 5;1(5896):13-5.

Hedenstierna G. Alveolar collapse and closure of airways: regular effects of anaesthesia. Clin Physiol Funct Imaging 2003 May;23(3):123-9.

in't Veen JC, et al. Recurrent exacerbations in severe asthma are associated with enhanced airway closure during stable episodes. Am J Respir Crit Care Med. 2000 Jun;161(6):1902-6.

Torchio R, et al. Closing capacity and gas exchange in chronic heart failure.

Chest . 2006 May;129(5):1330-6.