PT  - JOURNAL ARTICLE
AU  - M. Gorini
AU  - G. Misuri
AU  - A. Corrado
AU  - R. Duranti
AU  - I. Iandelli
AU  - E. De Paola
AU  - G. Scano
TI  - Breathing pattern and carbon dioxide retention in severe chronic obstructive pulmonary disease.
AID  - 10.1136/thx.51.7.677
DP  - 1996 Jul 01
TA  - Thorax
PG  - 677--683
VI  - 51
IP  - 7
4099  - http://thorax.bmj.com/content/51/7/677.short
4100  - http://thorax.bmj.com/content/51/7/677.full
SO  - Thorax1996 Jul 01; 51
AB  - BACKGROUND: The factors leading to chronic hypercapnia and rapid shallow breathing in patients with severe chronic obstructive pulmonary disease (COPD) are not completely understood. In this study the interrelations between chronic carbon dioxide retention, breathing pattern, dyspnoea, and the pressure required for breathing relative to inspiratory muscle strength in stable COPD patients with severe airflow obstruction were studied. METHODS: Thirty patients with COPD in a clinically stable condition with forced expiratory volume in one second (FEV1) of < 1 litre were studied. In each patient the following parameters were assessed: (1) dyspnoea scale rating, (2) inspiratory muscle strength by measuring minimal pleural pressure (PPLmin), and (3) tidal volume (VT), flow, pleural pressure swing (PPLsw), total lung resistance (RL), dynamic lung elastance (ELdyn), and positive end expiratory alveolar pressure (PEEPi) during resting breathing. RESULTS: Arterial carbon dioxide tension (PaCO2) related directly to RL/PPLmin, and ELdyn/PPLmin, and inversely to VT and PPLmin. There was no relationship between PaCO2 and functional residual capacity (FRC), total lung capacity (TLC), or minute ventilation. PEEPi was similar in eucapnic and hypercapnic patients. Expressing PaCO2 as a combined function of VT and PPLmin (stepwise multiple regression analysis) explained 71% of the variance in PaCO2. Tidal volume was directly related to inspiratory time (TI), and TI was inversely related to the pressure required for breathing relative to inspiratory muscle strength (PPLsw, %PPLmin). There was an association between the severity of dyspnoea and both the increase in PPLsw (%PPLmin) and the shortening in TI. CONCLUSIONS: The results indicate that, in stable patients with COPD with severe airflow obstruction, hypercapnia is associated with shallow breathing and inspiratory muscle weakness, and rapid and shallow breathing appears to be linked to both a marked increase in the pressure required for breathing relative to inspiratory muscle strength and to the severity of the breathlessness.