Paradoxical movement of the lower rib cage at rest and during exercise in COPD patients

¹ TBM Lab, Dipartimento di Bioingegneria, Politecnico di Milano, Milano, Italy
² TBM Lab, Dipartimento di Bioingegneria, Politecnico di Milano, Milano, Italy; and Clinical Sciences Centre, University Hospital Aintree, University of Liverpool, Liverpool, United Kingdom
³ Clinical Sciences Centre, University Hospital Aintree, University of Liverpool, Liverpool, United Kingdom
⁴ Clinical Sciences Centre, University Hospital Aintree, University of Liverpool, Liverpool, United Kingdom; and Federal University of Sao Paulo, Brazil

^* To whom correspondence should be addressed. E-mail: andrea.aliverti{at}polimi.it.

	Abstract

Paradoxical inward displacement of the costal margin during inspiration is observed in many COPD patients at rest but its importance is unclear.

We studied 20 patients (FEV₁=32.6±11.7, FRC=186±32%pred) and 10 healthy controls at rest and during symptom-limited incremental exercise. With optoelectronic plethysmography we quantified the phase shift between pulmonary and abdominal ribcage volumes and the percentage of inspiratory time the rib cage compartments moved in opposite directions using control data to define the normal range of movement.

Eight patients showed lower ribcage inspiratory paradox (P+) at rest while 12 patients did not (P-). This was unrelated to resting lung function or exercise tolerance.

Total end-expiratory chest wall volume (EEVcw) increased immediately when exercise began in P+ patients, but later in exercise in P- patients (p<0.001). This difference in EEVcw was mainly due to a greater increase of end-expiratory pulmonary ribcage volume (p<0.001) in P+ patients. During exercise, dyspnoea increased similarly in the two groups, while leg effort increased more markedly in the patients without paradox (p<0.01).

We conclude that lower ribcage paradox at rest is reproducible, associated with early-onset hyperinflation of the chest wall and predominant dyspnoea at end-exercise. When paradox is absent, the sense of leg effort becomes a more important symptom limiting exercise.