Pulmonary Function Testing, Spirometry and Related Tests (Book Chapter)
Authors: Rolf M. Schlegelmilch, Rüdiger Kramme
DOI / Source: http://www.springer.com/978-3-540-74657-7
Date: 13 March 2015
Reading level: Intermediate
Why This Matters for Freedivers
Spirometry is one of the simplest ways to measure how your lungs are actually functioning, not just how big they are. It can help spot things like airway obstruction, poor exhalation mechanics, or changes after illness—useful if you’re training hard, diving frequently, or recovering from a chest issue. It’s also the gateway to more advanced tests (lung volumes, diffusion) that matter when you’re trying to understand “big lungs vs effective lungs.”
Synopsis
This chapter explains the core ideas behind pulmonary function testing, with a strong focus on spirometry—the most common, low-cost, fast test used to measure how much air you can move and how quickly you can move it.
It starts with the two main questions spirometry answers: (1) how much air you can inhale/exhale (volume) and (2) how fast you can exhale it (flow). From a full inhale followed by a forced exhale, clinicians measure key values like FVC (forced vital capacity) and FEV1 (how much you can force out in the first second). The chapter also explains the two common ways results are displayed: a volume–time curve (spirogram) and a flow–volume loop, where the shape of the loop can quickly suggest normal lungs, obstruction, restriction, emphysema patterns, or upper-airway narrowing.
A major theme is that spirometry is only as good as the measurement. The chapter walks through how spirometers measure airflow (pneumotachography), how flow is digitally integrated to volume, and why devices must be checked with verification/calibration routines using a known-volume syringe. It also covers practical issues that affect accuracy: sensor contamination, baseline drift, “dead zones” near zero flow, and why modern devices apply BTPS correction (converting measured air at room conditions to body conditions—warm and humid—so volumes and flows aren’t off by ~10%).
The chapter then expands beyond basic spirometry into the “next layer” of testing: body plethysmography (for absolute lung volumes and airway resistance), diffusion capacity testing (how well gases cross from alveoli to blood, usually via carbon monoxide transfer), nitrogen washout (for functional residual capacity), and ergospirometry (gas exchange during exercise to understand the lung–heart–muscle system together).
Overall, it’s a technical-but-practical guide: what the tests measure, how the devices work, what can go wrong, and how results are interpreted in real clinical settings.
Abstract
Pulmonary function tests examine how well the lungs work. This chapter reviews the principles and instrumentation behind major pulmonary function techniques, including spirometry, peak flow measurement, body plethysmography, nitrogen washout, diffusion testing, and ergospirometry. Spirometry is presented as the fundamental test for measuring volumes and flow rates during breathing, especially during forced expiration, enabling standard parameters such as forced vital capacity and forced expiratory volume in one second. The chapter also discusses sensor technologies, calibration and verification, hygiene, conversion to body conditions, and practical considerations that influence test quality and interpretation.