Tuesday, August 22, 2017

Deep inflations and their role in reproducible lung function measurements

Reproducibility is more than ever an inevitable topic in research.  Recently, the subject was addressed by Dr. Jason Bates1 specifically in relation to preclinical lung function measurements. 

As explained in this interesting article, lung function measurements are affected by a number of confounding factors and controlling for them ensures that the subjects are studied under the same conditions, which helps generate robust data that can be reproduced by others. 

According to Dr. Bates, controlled experimental conditions including anaesthesia and mechanical ventilation are needed to achieve high-quality preclinical lung function data1, 2.  However, it is known that under these conditions, there is a progressive loss in lung volume due to airway closure or collapse3.  Additionally, as can be seen in a number of studies, once closed, airspaces do not spontaneously re-open.  A high-pressure manoeuver, such as a deep lung inflation, is typically required to open-up closed airways4, 5 or completely collapsed lungs6.  Therefore, as reported in the article at hand1, it is key to start a preclinical lung function experiment with a deep inflation to standardize lung volumes across subjects at baseline. 

DEEP INFLATION

Technical Description
  • The deep inflation gradually inflates the subject’s lungs to a pressure of 30 cmH2O over a period of 3 seconds.
  • The lungs are then held at that pressure for another 3 seconds, time during the alveolar pressure is allowed to equilibrate to the applied pressure.
  • The initial and end volumes are used in the calculation the inspiratory capacity (IC).
Physiological Description
  • The Deep Inflation perturbation brings the subject’s lungs from end of expiration (FRC) to total lung capacity (TLC), which is defined by default as a pressure of 30 cmH2O.
  • It provides a direct measurement of the subject’s inspiratory capacity.
For more information on the deep inflation and other manoeuvers questions linked to preclinical lung function measurements or scientific equipment for respiratory research, please visit SCIREQ website - Knowledge Center or contact one of our applications specialists.  We will be happy to work with you to enhance the reproducibility of your research.

References
1.       Bates, JHT.  2017.  CORP: Measurement of lung function in small animals.  J Appl Physiol, in press, DOI: 10.1152/japplphysiol.00243.2017.
2.       Bates JH, Irvin CG.  2003.  Measuring lung function in mice: the phenotyping uncertainty principle. J Appl Physiol 94: 1297-306.
3.       Mead J, Collier C.  1959.  Relation of volume history of lungs to respiratory mechanics in anesthetized dogs.  J Appl Physiol 14: 669-678.
4.       Wagers S, Lundblad LK, Ekman M, Irvin CG, Bates JH.  2004.  The allergic mouse model of asthma: normal smooth muscle in an abnormal lung?  J Appl Physiol 96: 2019-27.
5.       Shalaby KH, Gold LG, Schuessler TF, Martin JG, Robichaud A.  2010.  Combined forced oscillation and forced expiration measurements in mice for the assessment of airway hyperresponsiveness.  Respir Res 11: 82.
6.       Limjunyawong N, Fallica J, Horton MR, Mitzner W.  2015.  Measurement of the pressure-volume curve in mouse lungs. Journal of visualized experiments: J Vis Exp 95: 52376.

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