Respiratory Airflow

Overview:

Spirometry is a non-invasive method of lung function testing, which measures the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. Most lung function tests involve fairly simple breathing tasks and are usually not uncomfortable. Breathing requirements for some test measurements may be normal and quiet. Other tests require forced inhalation or exhalation after a deep breath. Spirometry can be used for assessing lung conditions such as asthma, emphysema, pulmonary fibrosis and cystic fibrosis.





 

Method:

During a human spirometry test, a nose clip is used and the subject breathes through a tight-fitting mouthpiece that is connected to an instrument called a spirometer. The spirometer (using differential pressure measurements that are related to air flow) records the rate of airflow breathed in and out over a period of time.

Most digital spirometers display the following graphs:

• A volume-time curve, showing volume (liters) along the Y-axis and time (seconds) along the X-axis
• A flow-volume loop, which graphically depicts the rate of airflow on the Y-axis and the total volume inspired or expired on the X-axis

Measurement Techniques

Pneumotachometer
This type of spirometer is also referred to as a differential pressure transducer (DPT) and measures the flow of air by detecting pressure differences across the two sides of a fine wire-mesh within a flow head. One advantage of this spirometer is that the subject under investigation can breathe in fresh air during the experiment. However, a DPT does not provide an output reading of absolute pressure within the system. The ML141 Spirometer is a precision differential pressure transducer for measurements of respiratory flow rates. With a flow head of a suitable size, the Spirometer can be used with animals of all sizes, from mice and rats, to large animals and humans.

Whole body plethysmograph
The whole body plethysmograph provides a more accurate measurement for the components of lung volumes compared to conventional spirometers. In this technique, the subject (i.e. small animal) is enclosed in a small airtight chamber when the measurement is taken. This method obtains the absolute volume of air within the subject’s lungs. The MLT844 Physiological Pressure Transducer is ideal for measuring absolute respiratory and pulmonary pressures, such as mean expiratory pressure [MEP]. This transducer is suitable for pressures ranging from -27 cmH₂O (-20 mmHg) to 408 cmH²O (300 mmHg). Note: Whilst the Physiological Pressure Transducer may be suitable for measuring MEPs (typically 80 to 200 cmH₂O), it cannot be used for determining mean inspiratory pressures (MIPs) as the transducer does not cover this range (often in excess of -60 cm H₂O). For recording both MIPs and MEPs in human adults, third-party transducers are required.

Related information:

Exercise Physiology Studies application page
Respiratory Gas Analysis application page

Note: Functional Residual Capacity or FRC (the volume in the lungs when the muscles of respiration are relaxed) cannot be measured by Spirometry, but it can be measured using whole body plethysmography, nitrogen washout or helium dilution tests.

Software:

The LabChart Advantage:

(may require additional Modules and Extensions)

• Pneumotachograph flow signals can be integrated in LabChart to create an air volume trace
• The Spirometry Extension for LabChart processes the raw flow signal and displays respiratory parameters such as tidal volume, minute ventilation, respiratory rate, PIF, PEF, FVC, FEV₁ and generates flow-volume plots as well as Spirometry Reports
• Respiratory rate can be calculated online or offline using Cyclic Measurements (Win) or Computed Input/Cycle Variables (Mac) features in LabChart
• Flow/Volume or pressure/flow loops can be displayed online with LabChart’s XY View feature

LabChart

LabChart software (for Windows and Macintosh) together with a PowerLab data acquisition system offers up to 32 channels of real-time data acquisition, data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Additional acquisition and analysis functionality is provided with the use of specialized LabChart Extensions and LabChart Modules. LabChart Modules are available as part of LabChart Pro and LabChart Extensions are free for download from the website for existing LabChart users.

Metabolic Module

The Metabolic Module for LabChart (Windows and Macintosh) in combination with ADInstruments hardware is ideal in the determination of cardiorespiratory function and exercise physiology measurements. Typical applications include:

• Metabolic measurements
• Respiratory gas analysis
• Student exercise testing
• Pulmonary function analysis
• Anaerobic threshold
• Biopotential measurements and spirometry

The Metabolic Module records CO₂ and O₂ concentrations sampled from a gas mixing chamber and interprets these values in real time to provide parameters such as: VCO₂/min, VO₂/min, V_E/min and RER. The module also provides options for setting subject details, recording parameters and environmental conditions that includes:

• Hardware preferences: Choice of appropriate hardware
• Subject details: Name, Age, Weight, Height, Gender, ID number, Comments
• Calibration preferences: Settings for automated first and second gas calibrations
• General preferences: Averaging time (data logging) and recording time (duration of experiment) settings
• Environment settings: Expired/inspired, atmospheric and air conditions

Spirometry Extension

The Spirometry Extension for LabChart (Windows and Macintosh) provides:

• Automated calibration of respiratory flow (ADI Spirometer) and volume recordings
• Advanced analysis functions
• Generation of flow-volume plots
• Calculation of tidal volume and respiratory rate
• Calculation of minute ventilation, peak inspiratory and expiratory flow

GLP and 21 CFR Part 11
For those researchers working within a laboratory requiring GLP and 21 CFR Part 11 compliance the GLP Client and GLP Server are available for use with LabChart (Windows only) and PowerLab data acquisition systems. For more information, visit the Good Laboratory Practice application page or contact your nearest ADInstruments representative.

Hardware:

PowerLab Data Acquisition Systems

The PowerLab is a high-performance data acquisition unit capable of recording at speeds of up to 400,000 samples per second continuously to disk (aggregate). PowerLab units are compatible with instruments, signal conditioners and transducers supplied by ADInstruments, as well as many other third-party companies. In addition to standard single-ended BNC inputs, 4 differential Pod ports are also available for direct connection of Pod signal conditioners and appropriate transducers. Research PowerLab units include:

• PL3504 PowerLab 4/35 - 4 Channels
• PL3508 PowerLab 8/35 – 8 Channels
• PL3516 PowerLab 16/35 – 16 Channels
   

Systems

The PL3508B80 Exercise Physiology System is a complete physiology recording system for monitoring cardiorespiratory and metabolic function during exercise. The system records and displays continuous real-time measurements of metabolic parameters such as CO₂ and O₂ concentrations, airflow, air temperature, ECG or EMG.

The Exercise Physiology System includes:

• PL3508 PowerLab 8/35 (with LabChart software)
• MLS260/7 LabChart Pro Software
• FE132 Bio Amp
• ML206 Gas Analyzer
• MLA246 Gas Mixing Chamber
• FE141 Spirometer
• ML309 Thermistor Pod
• MLA240 Exercise Physiology Accessory Kit

Signal Conditioners

The FE141 Spirometer is a precision differential pressure transducer that is used with a PowerLab for measurements of respiratory flow rates in humans and animals. Using a flow head of a suitable size, respiratory flow rates from a variety of species can be measured.

The ML311 Spirometer Pod also measures respiratory flow rates in humans in conjunction with an appropriate respiratory flow head and PowerLab. The Spirometer Pod connects to any PowerLab with Pod ports (8-pin DIN inputs) or using the ML305 Pod Expander for units without Pod ports.

Transducers and Accessories

Airflow
Flow heads contain a fine wire-mesh and, in conjunction with a differential pressure transducer (such as the FE141 Spirometer and ML311 Spirometer Pod), the user can measure pressure changes across the wire-mesh which are proportional to airflow. ADInstruments provide the following range of flow heads:

• MLT1L Respiratory Flow Head 1L (for mice, small rats, guinea pigs)
• MLT10L Respiratory Flow Head 10L (for rabbits, cats and small dogs)
• MLT300L Respiratory Flow Head 300L (for human adults at rest)
• MLT1000L Respiratory Flow Head 1000L (for human adults during forced breathing and exercise)
• MLT3813H-V Heated Pneumotach 800L and Heater Controller (a heated flow head designed to eliminate condensation. Ideal for human exercise studies and experiments conducted in humid environments)
• A 3 Liter MLA5530 Calibration Syringe is also available to calibrate the larger flow heads. Additional syringes are available upon request.

Absolute Respiratory Pressure
The MLT844 Physiological Pressure Transducer is ideal for measuring absolute respiratory and pulmonary pressures, such as mean expiratory pressure [MEP]. This transducer is suitable for pressures ranging from -27 cmH₂O (-20 mmHg) to 408 cmH₂O (300 mmHg). Note: It cannot be used for determining mean inspiratory pressures (MIPs) as the transducer does not cover this range (often in excess of -60 cm H₂O).

Respiratory Rate

• The MLT1132 Piezo Respiratory Belt Transducer is recommended for recording respiratory rate in humans. The Respiratory Belt Transducer can also be used in large animals such as rabbits, dogs and pigs.
• The MLT415/A or MLT415/D Nasal Temperature Probe can be used to record respiratory rate in humans from nasal airflow measurements.
• The MLT1010 Piezo Electric Pulse Transducer may be suitable for qualitatively recording respiratory rate in small animals.
• For wireless measurements, the BioHarness Telemetry System (MLE1202 USA or MLE1201 EURO) can be used to measure a range of human biopotentials, including respiratory rate, wirelessly via radio frequency (Euro; 868.2 MHz and USA; 915 MHz)

Lung Sounds
Lung sounds can be recorded with the MLT206 Electronic Stethoscope using a high-frequency pulmonary setting and can be easily correlated with respiratory cycles by recording the flow and lung sounds on separate channels.

Other Accessories
A variety of accessories are available from ADInstruments, including:

• MLA0343 Drying Tube (Nafion)
• MLA6024 Desiccant Cartridge
• MLA0110 In-line Filters (10 Pack)
• MLA304 Disposable Filters, Supplied in packs of 50
• MLA1008 Nose Clips, Supplied in packs of 50
• MLA1026 Reusable Mouthpieces (10)
• MLA1081 Flow Head Adapter
• MLA1011A Clean-bore Tubing & Tubing Adapter
• MLA1013 Tubing Adapter (35mm ID)
• MLA1029 Face Mask Kit (adult small and medium)
• MLA1028 Face Mask (adult medium)
• SP0141 Adult Face Mask (small)
• SP0155 Adult Face Mask (Medium)
• SP0150 Adult Face Mask (Large)

Sex differences in the resistive and elastic work of breathing during exercise in endurance-trained athletes
Guenette JA, Querido JS, Eves ND, Chua R, Sheel AW, American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, R166–R175, 2009

Breath-to-breath hypercapnic response in neonatal rats: temperature dependency of the chemoreflexes and potential implications for breathing stability
Cummings KJ, Frappell PB, American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, R124-R134, 2009

Chaotic dynamics of cardioventilatory coupling in humans: effects of ventilatory modes
Mangin L, Clerici C, Similowski T, Poon CS, American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, R1088-R1097, 2009