Respiratory Airflow

Overview:

The spirometry technique is a very common measurement to assess lung function. It measures the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. Spirometry can be used for assessing conditions such as asthma and pulmonary fibrosis.





 

Method:

The spirometry test is performed using a device called a spirometer, which comes in several different varieties. Most 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

Differential Pressure Measurements
To measure the pressure difference that develops across the two sides of the wire-mesh within the flow head, a differential pressure transducer (DPT) is required. However, a DPT does not provide an output reading of absolute pressure within the system.

Absolute Respiratory Pressure Measurements
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) and connects to the PowerLab via any ADInstruments Bridge Amplifier.

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:

Metabolic Rates application page
Oximetry application page
Respiratory Gas Analysis application page
CO₂ and NH₃ application page
Oxygen Concentration application page

Software:

LabChart
LabChart™ software (for Windows and Macintosh) combines the familiar simplicity of a traditional strip chart recorder with the powerful analysis features of a digital acquisition system. LabChart software and a PowerLab data acquisition unit provide data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Acquisition and analysis capabilities can be further increased with 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.

Respiratory rate can be calculated online or offline using the Cyclic Measurements (Win) or Computed Input/Cycle Variables (Mac) features in LabChart.

Spirometry Extension
The Spirometry Extension for LabChart is available on both Windows and Macintosh platforms and provides:

• Automated calibration of respiratory flow 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

Metabolic Module (Windows or Macintosh)
The MLS240/7 Metabolic Module for LabChart 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
• Indirect calorimetry
• 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, VE/min and RER. The module also provides options for setting subject details, recording parameters and environmental conditions.

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:

ADInstruments provide a range of data acquisition systems, signal conditioners, respiratory flow heads, pressure transducers and amplifiers that connect to PowerLab data acquisition systems for monitoring air flow and calculating respiratory data.

PowerLab Data Acquisition Systems
The PowerLab is a high-performance data acquisition unit suitable for a wide range of research applications. Typical applications include human and animal physiology, pharmacology, neurophysiology, biology, zoology, biochemistry, and biomedical engineering. Units are capable of recording at speeds of up to 400 000 samples per second continuously to disk (aggregate), and are compatible with instruments, signal conditioners and transducers supplied by ADInstruments, as well as many other brands. 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. These systems include:

• ML866 PowerLab 4/30 - 4 Channels
• ML870 PowerLab 8/30 – 8 Channels
• ML880 PowerLab 16/30 – 16 Channels

Signal Conditioners
ML141 Spirometer
The Spirometer is a precise differential pressure transducer that is used with a PowerLab for measurements of respiratory flow rates. Respiratory flow rates from a variety of species can be measured with a flow head of a suitable size.

Respiratory Flow Heads
The flow head connects directly to the inspiratory or expiratory port in a respiratory monitoring system and, in conjunction with a differential pressure transducer, is used to measure pressure changes across a fine, wire mesh. The pressure change across the wire mesh (within the flow head) is 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 humans adults at rest)
• MLT1000L Respiratory Flow Head 1000L (For humans 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 (ranging from 10 ml to 7 L).

Transducers
MLT844 Physiological Pressure Transducer

Respiratory Rate
The (MLT1132 or MLT1133 MR compatible) Piezo Respiratory Belt Transducer or (MLT415/A or MLT415/D) Nasal Temperature Probe are 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 MLT1010 Piezo Electric Pulse Transducer is recommended for small animals.

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

• MLA6024 Desiccant Cartridge
• 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)
• MLA5530 Calibration Syringe

Human G protein Beta-3 subunit variant does not alter hypercarbic or hypoxic ventilatory response
H J Exner; H Groeben; D Rosskopf; W Siffert and J Peters, Clinical Physiology, 612-620, 2001

Carotid and cardiopulmonary chemoreceptor activity increases hippocampal theta rhythm in conscious rabbits.
Ying-Hui Yu and W. W. Blessing , American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, R973-R979, 2000