Residual Lung Capacity – Voice Science

Definition

Residual volume (RV) is the air remaining in the lungs after maximum exhalation—approximately 1.2L in healthy adults. This volume cannot be expelled voluntarily regardless of expiratory effort. John Hutchinson originally termed this “residual air” in 1846, recognizing that complete lung emptying is physiologically impossible.

Context

Relevance to Voice Production

Classical singers often extend phrases to near residual volume at termination, utilizing the full range between Total Lung Capacity (TLC) and RV. This extreme excursion requires the inspiratory muscles to actively brake the passive recoil forces that would otherwise cause uncontrolled exhalation at high lung volumes (Thomasson and Sundberg, 1997).

The RV/TLC ratio—residual volume as a proportion of total lung capacity—serves as an indicator of breathing efficiency. Gould and Okamura (1973) found that trained singers demonstrate lower RV/TLC ratios that improved with training duration, concluding: “The increased singing ability of the trained professional singer arises in large part from the ability to increase breathing efficiency by reducing the residual lung volume.”

This finding suggests that training enables singers to access more of their total lung capacity for phonation, effectively reducing the “unusable” portion of their respiratory system.

Measurement

Unlike Vital Capacity or Tidal Volume, residual volume cannot be measured by standard spirometry because the air never leaves the lungs. Measurement requires either:

• Body plethysmography: Measures thoracic gas volume in a sealed chamber
• Gas dilution methods: Uses helium or nitrogen washout techniques

Residual volume can also be calculated indirectly: RV = TLC − VC.

Scientific Basis

Residual volume serves essential physiological functions:

• Prevents alveolar collapse: Maintains lung inflation and gas exchange surface area
• Enables continuous gas exchange: Oxygen absorption and carbon dioxide release continue between breaths
• Protects airway patency: Prevents complete airway closure during forced exhalation

RV increases with age, contributing significantly to the decline in vital capacity observed in older adults. As RV rises, less volume remains available for voluntary breathing maneuvers. In obstructive conditions such as COPD, an elevated RV/TLC ratio exceeding 40% indicates air trapping—the pathological inability to fully exhale.

Males and females show similar residual volumes when corrected for body size, as RV scales with overall lung dimensions rather than sex-specific factors.

Pedagogical Considerations

Several respiratory dynamics become relevant as singers approach residual volume:

• Increased expiratory effort: Below approximately 30% of vital capacity, the muscular effort required for continued exhalation increases substantially as passive recoil forces diminish
• Inspiratory braking: At high lung volumes, singers must engage inspiratory muscles to control the natural tendency toward rapid deflation
• Speech patterns: Normal speech typically terminates well above residual volume, at approximately 30–40% VC
• Training effects: While training does not change anatomical RV, it appears to improve efficiency of volume utilization, effectively allowing singers to phonated closer to their physiological limits

Related Terms

Also known as: RV, Residual air (historical)

See also: Lung Capacity (parent concept), Vital Capacity (maximum voluntary volume)

References

Gould, Wilbur J., and Hiromitsu Okamura. 1973. “Static Lung Volumes in Singers.” Annals of Otology, Rhinology & Laryngology 82(1): 89–95. https://doi.org/10.1177/000348947308200118.

Kouri, Adamo, et al. 2021. “Exploring the 175-Year History of Spirometry and the Vital Lessons It Can Teach Us Today.” European Respiratory Review 30(162): 210081. https://doi.org/10.1183/16000617.0081-2021.

Thomasson, Margareta, and Johan Sundberg. 1997. “Lung Volume Levels in Professional Classical Singing.” Logopedics Phoniatrics Vocology 22(2): 61–70. https://doi.org/10.3109/14015439709075318.

Wanger, Jack, et al. 2005. “Standardisation of the Measurement of Lung Volumes.” European Respiratory Journal 26(3): 511–522. https://doi.org/10.1183/09031936.05.00035005.