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[Physiology](https://durgical.com/en/physiology/) · [Respiratory](https://durgical.com/en/physiology/#s-resp)

# Lung and chest wall compliance

- Concept
- Exam priority: medium

Compliance is how much the lung inflates for each unit of pressure. A stiff lung takes more work to fill.

Updated 2026-11-01

Also called: Compliance, Pulmonary compliance, Elastance

**See it in 3D:** [Pleura](https://durgical.com/en/anatomy/pleura/) · [Right lower lobe](https://durgical.com/en/anatomy/inferior-lobe-of-right-lung/)

## Key points

- Compliance = ΔV/ΔP; lung alone ≈ 200 mL/cmH₂O, lung + chest wall ≈ 110 mL/cmH₂O.
- Low in fibrosis, ARDS, pulmonary edema, atelectasis and surfactant deficiency.
- High in emphysema (loss of elastic fibres) and with age.
- Hysteresis (inflation ≠ deflation) is mainly due to surface tension.

## What it is

Compliance is the change in volume per change in transpulmonary pressure (ΔV/ΔP). It depends on elastic fibres and, above all, on alveolar surface tension, which surfactant lowers. The lung tends to collapse and the chest wall to spring out; at FRC the two forces balance.

## How it works, step by step

- On inflation, elastic fibres stretch and the alveolar liquid surface grows.
- Surface tension tends to close alveoli; surfactant lowers it, the more so the smaller the alveolus.
- In fibrosis, stiff collagen demands more pressure per millilitre: compliance falls.
- In emphysema the lung inflates easily but loses recoil and cannot push the air out.

### Lung volumes and capacities

**TLC** 3.6 L **VC** 2.8 L **FRC** 1.4 L **RV** 0.8 L **FEV1/FVC** 0.87

Restrictive (pulmonary fibrosis, chest wall or neuromuscular disease, obesity): all volumes ↓ (TLC
- IRV · Inspiratory reserve volume
- TV · Tidal volume
- ERV · Expiratory reserve volume
- RV · Residual volume
- Capacity (sum of volumes)
- Current forced expiration
- Normal

Stiff lung: every volume shrinks.

## Equations

**Compliance**C = ΔV / ΔP

**ΔV**
change in volume

**ΔP**
change in transpulmonary pressure

Elastance is its inverse (1/C): how much pressure each millilitre costs.

## Approximate values (adult)

| Parameter | Value | Note |
| --- | --- | --- |
| Lung compliance | ≈ 200 mL/cmH₂O | |
| Respiratory system compliance (lung + chest wall) | ≈ 110 mL/cmH₂O | |
| Static compliance on a ventilator | ≈ 50–100 mL/cmH₂O | lower supine and intubated |

Approximate values for a healthy adult at rest; each laboratory sets its own ranges.

## Changes in compliance

| Condition | Compliance | Why |
| --- | --- | --- |
| [Interstitial fibrosis](https://durgical.com/en/conditions/interstitial-lung-disease/) | Low | Stiff collagen in the interstitium |
| [ARDS, pulmonary edema](https://durgical.com/en/conditions/acute-respiratory-distress-syndrome/) | Low | Flooded alveoli and less surfactant |
| [Emphysema](https://durgical.com/en/conditions/chronic-obstructive-pulmonary-disease/) | High | Destroyed elastic fibres |
| [Obesity, kyphoscoliosis](https://durgical.com/en/conditions/obesity/) | Low (chest wall) | Stiff or loaded chest wall |

## Clinical notes

- ARDS: very low compliance calls for small tidal volumes so healthy alveoli are not overstretched.
- Premature newborn: without surfactant, alveoli collapse and compliance is low (respiratory distress syndrome).

## Test yourself

Think of the answer, then tap the question to see it.

## Why does an emphysematous lung inflate easily but empty poorly?

With elastic fibres lost, compliance rises, but so does the loss of the recoil that drives expiration and holds small airways open.

## What contributes more to lung elastic recoil: elastic fibres or surface tension?

Surface tension; that is why a lung inflated with saline needs much less pressure than one inflated with air.

## If giving 500 mL raises transpulmonary pressure by 5 cmH₂O, what is the compliance?

500/5 = 100 mL/cmH₂O.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/physiology/lung-and-chest-wall-compliance/)

## See it in 3D

The structures of Durgical's 3D anatomy where it happens.

- [Pleura](https://durgical.com/en/anatomy/pleura/)
- [Right lower lobe](https://durgical.com/en/anatomy/inferior-lobe-of-right-lung/)

## Related topics

- [Surface tension, surfactant and Laplace's law](https://durgical.com/en/physiology/surface-tension-surfactant-and-laplace-s-law/)
- [Mechanics of breathing: pressures and muscles](https://durgical.com/en/physiology/mechanics-of-breathing-pressures-and-muscles/)
- [The work of breathing](https://durgical.com/en/physiology/the-work-of-breathing/)
- [Obstructive and restrictive patterns, and flow–volume loops](https://durgical.com/en/physiology/obstructive-and-restrictive-patterns-and-flow-volume-loops/)
- [Airway resistance](https://durgical.com/en/physiology/airway-resistance/)

## Related conditions

- [Acute respiratory distress syndrome (ARDS)](https://durgical.com/en/conditions/acute-respiratory-distress-syndrome/)
- [Interstitial lung disease](https://durgical.com/en/conditions/interstitial-lung-disease/)
- [Chronic obstructive pulmonary disease (COPD)](https://durgical.com/en/conditions/chronic-obstructive-pulmonary-disease/)
- [Obesity](https://durgical.com/en/conditions/obesity/)

[← All of physiology](https://durgical.com/en/physiology/)

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: [22.3 The Process of Breathing](https://openstax.org/books/anatomy-and-physiology-2e/pages/22-3-the-process-of-breathing) (OpenStax (Rice University), 2022); [Acute Respiratory Distress Syndrome](https://www.ncbi.nlm.nih.gov/books/NBK436002/) (StatPearls (NCBI Bookshelf), 2024); [Interstitial Lung Disease](https://www.ncbi.nlm.nih.gov/books/NBK541084/) (StatPearls (NCBI Bookshelf), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 38). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/lung-and-chest-wall-compliance/