Maximum insufflation capacity: Vital capacity and cough flows in neuromuscular disease

Seong Woong Kang, John R. Bach

Research output: Contribution to journalArticlepeer-review

151 Scopus citations


Objective: To investigate the relationships between vital capacity (VC), maximum insufflation capacity (MIC), and both unassisted and assisted peak cough flows (PCFs). Design: The 108 patients were divided into two groups, those whose MICs were greater than their VCs (group 1) and those whose MICs could not exceed their VCs (MIC = VC, or group 2). Results: The MIC correlated positively with the VC for group 1 patients, but the percent increase in MIC correlated negatively with VC. Both VC and MIC correlated significantly with both unassisted and assisted PCF, respectively. Assisting the cough increased the PCF of 37 patients over a previously defined critical level of 2.7 L/sec. The MIC VC difference and percent increase in MIC also correlated significantly with the difference between unassisted and assisted PCF. Although the group 2 patients did not have true cough flows because of inability to close the glottis, their peak expiratory flows were significantly less than the unassisted and assisted PCF of the group 1 patients. Conclusions: The greater the MIC VC difference, the greater the PCF, and, thereby, the ability to expel airway mucus and avert respiratory complications. The lower the VC, the greater the percent increase in MIC and the greater the percent increase in assisted PCF. Maximal insufflations are extremely important to increase PCF for patients with neuromuscular conditions who have VCs of < 1500 ml.

Original languageEnglish (US)
Pages (from-to)222-227
Number of pages6
JournalAmerican Journal of Physical Medicine and Rehabilitation
Issue number3
StatePublished - May 2000

All Science Journal Classification (ASJC) codes

  • Physical Therapy, Sports Therapy and Rehabilitation
  • Rehabilitation


  • Amyotrophic Lateral Sclerosis
  • Cough
  • Exsufflation
  • Mechanical Ventilation
  • Poliomyelitis, Muscular Dystrophy
  • Respiratory Therapy

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