A leak-free head-out plethysmography system to accurately assess lung function in mice

Abstract

Mice are a valuable model for elegant studies of complex, systems-dependent diseases, including pulmonary diseases. Current tools to assess lung function in mice are either terminal or lack accuracy. We set out to develop a low-cost, accurate, head-out variable-pressure plethysmography system to allow for repeated, non-terminal measurements of lung function in mice. Current head-out plethysmography systems are limited by air leaks that prevent accurate measures of volume and flow. We designed an inflatable cuff that encompasses the mouse's neck preventing air leak. We wrote corresponding software to collect and analyze the data, remove movement artifacts, and automatically calibrate each dataset. This software calculates inspiratory/expiratory volume, inspiratory/expiratory time, breaths per minute, mid-expiratory flow, and end-inspiratory pause. To validate the use, we established that our plethysmography system accurately measured tidal breathing, the bronchoconstrictive response to methacholine, sex and age associated changes in breathing, and breathing changes associated with house dust mite sensitization. Our estimates of volume, flow, and timing of breaths are in line with published estimates, we observed dose-dependent decreases in volume and flow in response to methacholine (P < 0.05), increased lung volume and decreased breathing rate with aging (P < 0.05), and that house dust mite sensitization decreased volume and flow (P <0.05) while exacerbating the methacholine induced increases in inspiratory and expiratory time (P < 0.05). We describe an accurate, sensitive, low-cost, head-out plethysmography system that allows for longitudinal studies of pulmonary disease in mice.

Obesity-Associated Alterations in Lung Function in Mice Measured with Head-Out Plethysmography

“…Tidal breathing comparison between lean and diet-induced obese male mice for variables collected using head-out plethysmography. The authors have reported a subset of group (n=9 lean mice tidal breathing & response to methacholine) previously(14). For all graphs lean n=23 obese n=29; results presented as mean + SEM.…”

“…High fat diet (HFD: Tekland WI TD 06414) was provided at 12 weeks of age for 9 weeks. At 21 weeks of age, we assessed lung function in chow fed lean (24.4 + 0.7 grams) and diet-induced obese mice (40.8 + 1.2 grams) with head-out plethysmography and subsequently measured lung mechanics using forced oscillation technique in a subset of mice (14).…”

“…Lean and obese mice responded similarly to methacholine as measured using head-out plethysmography (Figure 2) and the forced oscillation technique (Figure 3). We have reported the data for a subset of the lean mice (9 lean mice tidal breathing and response to methacholine) previously (14).…”

“…Different letters signify statistically significant difference between bars. The authors have reported a subset of group (n=9 lean mice tidal breathing and response to methacholine) previously (14). For all graphs lean n=23 obese n=29; results presented as mean + SEM.…”

“…We have previously described the validation of a leak-free, head-out plethysmography system for use in mice (14). Head-out plethysmography assesses lung function by placing mice in an airtight chamber with their head protruding.…”