Am. J. Respir. Crit. Care Med., Vol 152, No. 6, Dec 1995, 2181-2184.
Oxygen cost of breathing in patients with emphysema or chronic bronchitis in acute respiratory failure
V Jounieaux and I Mayeux
Service de Pneumologie et Unite de Reanimation Respiratoire, Centre Hospitalier Universitaire Sud, Amiens, France.
This study compared the oxygen cost of breathing (VO2 resp) in 19 patients
with severe chronic obstructive pulmonary disease intubated for acute
respiratory failure. Ten patients showed radiologic (X-ray and/or computed
tomographic scan) evidence of emphysema. The remaining ones were considered
as having chronic bronchitis. Measurements were made just before
extubation. Despite similar expiratory airflow obstruction, patients with
emphysema exhibited significantly higher VO2 resp than patients with
chronic bronchitis (109 +/- 61 versus 42 +/- 26 ml/min/m2, respectively; p
< 0.006). Moreover, emphysema was associated with nutritional depletion
assessed through decreases in body mass index (emphysema: 17.9 +/- 3.5
kg/m2; chronic bronchitis: 28.8 +/- 8.2 kg/m2; p < 0.005). This seemed
to affect somatic stores (significant decreases in arm muscular
circumference and triceps skin-fold thickness, whereas visceral stores were
preserved (no decreases in serum albumin, serum prealbumin, and retinol
binding protein). Malnutrition appeared to be the consequence of a
hypermetabolic state of the respiratory muscles, with a significant
negative correlation between VO2 resp and body mass index, arm muscular
circumference, and triceps skinfold thickness (p < 0.05). Total oxygen
consumption normalized for body surface was similar in the two groups.
Thus, in emphysematous patients, the oxygen available for tissues other
than respiratory muscles was significantly reduced (emphysema: 124 +/- 51
ml/min/m2; chronic bronchitis: 207 +/- 78 ml/min/m2; p < 0.02). This
could explain nutritional differences observed between patients with
emphysema and those with chronic bronchitis.
