Lung volumes are subdivided into static and dynamic lung volumes. Static lung volumes are measured by methods which are based on the completeness of respiratory manoeuvres, so that the velocity of the manoeuvres should be adjusted accordingly. The measurements taken during fast breathing movements are described as dynamic lung volumes and as forced inspiratory and expiratory flows.

### 1.1 Static lung volumes and capacities

The volume of gas in the lung and intrathoracic airways is determined by the properties of lung parenchyma and surrounding organs and tissues, surface tension, the force exerted by respiratory muscles, by lung reflexes and by the properties of airways. The gas volumes of thorax and lung are the same except in the case of a pneumothorax. If two or more subdivisions of the total lung capacity are taken together, the sum of the constituent volumes is described as a lung capacity. Lung volumes and capacities are described in more detail in § 2.

#### 1.1.1 Determinants

Factors which determine the size of the normal lung include stature, age, sex, body mass, posture, habitus, ethnic group, reflex factors and daily activity pattern. The level of maximal inspiration (total lung capacity, TLC) is influenced by the force developed by the inspiratory muscles (disorders include e.g. muscular dystrophy), the elastic recoil of the lung (disorders include e.g. pulmonary fibrosis and emphysema) and the elastic properties of the thorax and adjacent structures (disorders include e.g. ankylosis of joints). The level of maximal expiration (residual volume, RV) is determined by the force exerted by respiratory muscles (disorders include e.g. muscle paralysis), obstruction, occlusion and compression of small airways (disorders include e.g. emphysema) and by the mechanical properties of lung and thorax (disorders include diffuse fibrosis, kyphoscoliosis).

Assessing the total lung capacity is indispensable in establishing a restrictive ventilatory defect or in diagnosing abnormal lung distensibility, as may occur in patients …

Lung volumes and forced ventilatory flows

To study the mechanisms and kinetics underlying the development of increased airway responsiveness (AR) after allergic sensitization, animal models have been invaluable. Using barometric whole-body plethysmography and increases in enhanced pause (Penh) as an index of airway obstruction, we measured responses to inhaled methacholine in conscious, unrestrained mice after sensitization and airway challenge with ovalbumin (OVA). Sensitized and challenged animals had significantly increased AR to aerosolized methacholine compared with control animals. AR measured as Penh was associated with increased IgE production and eosinophil lung infiltration. In a separate approach we confirmed the involvement of the lower airways in the response to aerosolized methacholine using tracheotomized mice. Increases in Penh values after methacholine challenge were also correlated with increased intrapleural pressure, measured via an esophageal tube. Lastly, mice demonstrating AR using a noninvasive technique also demonstrated ...

Noninvasive Measurement of Airway Responsiveness in Allergic Mice Using Barometric Plethysmography

The forced oscillation technique in clinical practice: methodology, recommendations and future developments. E. Oostveen, D. MacLeod, H. Lorino, R. Farre´ , Z. Hantos, K. Desager, F. Marchal, on behalf of the ERS Task Force on Respiratory Impedance Measurements. #ERS Journals Ltd 2003. ABSTRACT: The forced oscillation technique (FOT) is a noninvasivemethod with which to measure respiratory mechanics. FOT employs small-amplitude pressure oscillations superimposed on the normal breathing and therefore has the advantage over conventional lung function techniques that it does not require the performance of respiratory manoeuvres. The present European Respiratory Society Task Force Report describes the basic prin- ciple of the technique and gives guidelines for the application and interpretation of FOT as a routine lung function test in the clinical setting, for both adult and paediatric populations. FOT data, especially those measured at the lower frequencies, are sensitive to airway obstruction, but do not discriminate between obstructive and restrictive lung disorders. There is no consensus regarding the sensitivity of FOT for bronchodilation testing in adults. Values of respiratory resistance have proved sensitive to bronchodilation in children, although the reported cutoff levels remain to be cone rmed in future studies. Forced oscillation technique is a reliable method in the assessment of bronchial hyper- responsiveness in adults and children. Moreover, in contrast with spirometry where a deep inspiration is needed,forced oscillation techniquedoes not modifytheairway smooth muscle tone. Forced oscillation technique has been shown to be as sensitive as spirometry in detecting impairments of lung function due to smoking or exposure to occupational hazards. Together with the minimalrequirement for the subject 9s cooperation, this makes forced oscillation technique an ideal lung function test for epidemiological and e eld studies. Novel applications of forced oscillation technique in the clinical setting include the monitoring of respiratory mechanics during mechanical ventilation and sleep.

https://erj.ersjournals.com/content/erj/22/6/1026.full.pdf

The forced oscillation technique in clinical practice: methodology, recommendations and future developments

Nicole Beydon, Stephanie D. Davis, Enrico Lombardi, Julian L. Allen, Hubertus G. M. Arets, Paul Aurora, Hans Bisgaard, G. Michael Davis, Francine M. Ducharme, Howard Eigen, Monika Gappa, Claude Gaultier, Per M. Gustafsson, Graham L. Hall, Zoltán Hantos, Michael J. R. Healy, Marcus H. Jones, Bent Klug, Karin C. Lødrup Carlsen, Sheila A. McKenzie, François Marchal, Oscar H. Mayer, Peter J. F. M. Merkus, Mohy G. Morris, Ellie Oostveen, J. Jane Pillow, Paul C. Seddon, Michael Silverman, Peter D. Sly, Janet Stocks, Robert S. Tepper, Daphna Vilozni, and Nicola M. Wilson, on behalf of the American Thoracic Society/ European Respiratory Society Working Group on Infant and Young Children Pulmonary Function Testing

An official American Thoracic Society/European Respiratory Society statement: pulmonary function testing in preschool children.

Much has been published in the past 20 years on the use of measurements of arterial stiffness in animal and human research studies. This summary statement was commissioned by the American Heart Association to address issues concerning the nomenclature, methodologies, utility, limitations, and gaps in knowledge in this rapidly evolving field. The following represents an executive version of the larger online-only Data Supplement and is intended to give the reader a sense of why arterial stiffness is important, how it is measured, the situations in which it has been useful, its limitations, and questions that remain to be addressed in this field. Throughout the document, pulse-wave velocity (PWV; measured in meters per second) and variations such as carotid-femoral PWV (cfPWV; measured in meters per second) are used. PWV without modification is used in the general sense of arterial stiffness. The addition of lowercase modifiers such as “cf” is used when speaking of specific segments of the arterial circulation.

The ability to measure arterial stiffness has been present for many years, but the measurement was invasive in the early times. The improvement in technologies to enable repeated, minimal-risk, reproducible measures of this aspect of circulatory physiology led to its incorporation into longitudinal cohort studies spanning a variety of clinical populations, including those at extreme cardiovascular risk (patients on dialysis), those with comorbidities such as diabetes mellitus (DM) and hypertension, healthy elders, and general populations.

In the ≈3 decades of clinical use of PWV measures in humans, we have learned much about the importance of this parameter. PWV has proven to have independent predictive utility when evaluated in conjunction with standard risk factors for death and cardiovascular disease (CVD). However, the field of arterial stiffness investigation, which has exploded over the past 20 years, has proliferated without logistical guidance for clinical and …

Recommendations for Improving and Standardizing Vascular Research on Arterial Stiffness: A Scientific Statement From the American Heart Association

We tested the hypothesis that a simple change in wall composition (medial calcium overload of elastic fibers) can decrease aortic elasticity. Calcium overload was produced by hypervitamino...

Calcification of Medial Elastic Fibers and Aortic Elasticity

The sections in this article are:


1
Modeling the Respiratory System as a Linear System
1.1
Models

1.2
Elemental Equations

1.3
Sinusoidal Forcing and Complex Impedance

1.4
Continuity and Compatibility Conditions

1.5
General Formulation of System Models

1.6
System Functions

1.7
Equivalent Circuits

1.8
Distributed-Parameter Models




2
History

3
Experimental Methods
3.1
Equipment

3.2
Inputs and Data Processing

3.3
Upper Airway Variability and Shunt




4
Frequency Responses Below 100 HZ
4.1
Total Respiratory System

4.2
Input Impedance Forcing at the Airway Opening

4.3
Transfer Impedance Forcing at the Chest

4.4
Transfer Impedance Forcing at the Mouth

4.5
Pressure and Flow Transfer Functions

4.6
Lung Impedance

4.7
Chest Wall Impedance

4.8
Airway Impedance




5
Frequency Responses Above 100 HZ
5.1
Wave Propagation in the Airways

5.2
Input Impedance Forcing at the Airway Opening

5.3
Pressure Transfer Functions

5.4
Airway Area by Acoustic Reflections




6
Clinical Applications
6.1
Pulmonary Function in Children

6.2
Obstructive Lung Diseases

6.3
Restrictive Lung Diseases

6.4
Miscellaneous Lung Diseases

Oscillation Mechanics of the Respiratory System

Potential advantages of the forced oscillation technique over other methods for monitoring total respiratory mechanics during artificial ventilation are that it does not require patient relaxation, and that additional information may be derived from the frequency dependence of the real (Re) and imaginary (Im) parts of respiratory impedance. We wanted to assess feasibility and usefulness of the forced oscillation technique in this setting and therefore used the approach in 17 intubated patients, mechanically ventilated for acute respiratory failure. Sinusoidal pressure oscillations at 5, 10 and 20 Hz were applied at the airway opening, using a specially devised loudspeaker-type generator placed in parallel with the ventilator. Real and imaginary parts were corrected for the flow-dependent impedance of the endotracheal tube; they usually exhibited large variations during the respiratory cycle, and were computed separately for the inspiratory and expiratory phases. In many instances the real part was larger during inspiration, probably due to the larger respiratory flow, and decreased with increasing frequency. The imaginary part of respiratory impedance usually increased with increasing frequency during expiration, as expected for a predominately elastic system, but often varied little, or even decreased, with increasing frequency during inspiration. In most patients, the data were inconsistent with the usual resistance-inertance-compliance model. A much better fit was obtained with a model featuring central airways and a peripheral pathway in parallel with bronchial compliance. The results obtained with the latter model suggest that dynamic airway compression occurred during passive expiration in a number of patients. We conclude that the use of forced oscillation is relatively easy to implement during mechanical ventilation, that it allows the study of respiratory mechanics at various points in the respiratory cycle, and may help in detecting expiratory flow limitation.

https://erj.ersjournals.com/content/erj/6/6/772.full.pdf

Respiratory mechanics studied by forced oscillations during artificial ventilation.

A new method for measuring total respiratory input impedance (Zrs), which ensures minimal motion of extrathoracic airway walls, was tested over frequencies of 4–30 Hz in 14 normal subjects and 10 p...

Respiratory impedance measured with head generator to minimize upper airway shunt.

When studying respiratory impedance by forced oscillations, part of the flow measured at the mouth is lost in upper airway wall motion and does not enter the trachea. The corresponding error was studied in 10 normal subjects and 8 patients with chronic obstructive pulmonary disease (COPD) by measuring respiratory impedance with the cheeks unsupported, with the cheeks supported, and when upper airway wall motion was simultaneously measured with a head plethysmograph, and corrected for. In normal subjects, wall motion had little influence on respiratory resistance but, whether the cheeks were supported or not, increased the resonant frequency (p less than 0.05) and respiratory compliance (p less than 0.001) and decreased respiratory inertance (p less than 0.001). In patients with COPD, average resistance from 4 to 30 Hz was significantly lower when the cheeks were not supported (3.32 +/- 0.57 cm/H2O X L-1 X s; m +/- SD) than when they were (4.59 +/- 0.73, p less than 0.01) and when the data were corrected (5.41 +/- 1.14, p less than 0.001). Moreover, resistance increased with increasing frequency when wall motion was corrected for and decreased when it was not. Upper airway wall motion also tended to increase resonant frequency and decrease inertance in patients. The data show that supporting the cheeks does not prevent large errors on respiratory impedance and derived parameters, especially in obstructive patients; accurate measurements require that airway wall motion be evaluated and corrected for.

R. Peslin

Papers

Calcification of Medial Elastic Fibers and Aortic Elasticity

Oscillation Mechanics of the Respiratory System

Respiratory mechanics studied by forced oscillations during artificial ventilation.

Respiratory impedance measured with head generator to minimize upper airway shunt.

Upper airway artifact in respiratory impedance measurements.