Chest wall hyperinflation during acute bronchoconstriction in asthma.
The mechanics of the chest wall was studied in seven asthmatic patients before and during histamine-induced bronchoconstriction (B). The volume of the chest wall (VCW) was calculated by three-dimensional tracking of 89 chest wall markers. Pleural (Ppl) and gastric (Pga) pressures were simultaneously recorded. VCW was modeled as the sum of the volumes of the pulmonary-apposed rib cage (VRC,p), diaphragm-apposed rib cage (VRC,a), and abdomen (VAB). During B, hyperinflation was due to the increase in end-expiratory volume of the rib cage (0.63 +/- 0.09 L, p < 0.01), whereas change in VAB was inconsistent (0.09 +/- 0.07 L, NS) because of phasic recruitment of abdominal muscles during expiration. Changes in end-expiratory VRC,p and VRC,a were along the rib cage relaxation configuration, indicating that both compartments shared proportionally the hyperinflation. VRC,p-Ppl plot during B was displaced leftward of the relaxation curve, suggesting persistent activity of rib cage inspiratory muscles throughout expiration. Changes in end-expiratory VCW during B did not relate to changes in FEV(1) or time and volume components of the breathing cycle. We concluded that during B in asthmatic patients: (1) rib cage accounts largely for the volume of hyperinflation, whereas abdominal muscle recruitment during expiration limits the increase in VAB; (2) hyperinflation is influenced by sustained postinspiratory activity of the inspiratory muscles; (3) this pattern of respiratory muscle recruitment seems to minimize volume distortion of the rib cage at end-expiration and to preserve diaphragm length despite hyperinflation.
Gorini
M
M
Fondazione Pro Juventute Don C Gnocchi ONLUS, Firenze, Terapia Intensiva Polmonare e Fisiopatologia Toracica, Ospedale di Careggi, Clinica Medica III, Università di Firenze, Firenze, Italy.
Iandelli
I
I
Misuri
G
G
Bertoli
F
F
Filippelli
M
M
Mancini
M
M
Duranti
R
R
Gigliotti
F
F
Scano
G
G
D000009:Abdominal Muscles / Q000503:physiopathology; D000328:Adult; D000403:Airway Resistance; D001249:Asthma / Q000503:physiopathology*; D016084:Bronchoconstriction; D005541:Forced Expiratory Volume; D006632:Histamine / Q000008:administration & dosage; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D012044:Regression Analysis; D015656:Respiratory Mechanics; D012815:Signal Processing, Computer-Assisted; D013909:Thorax / Q000503:physiopathology*
D006632:Histamine; D010100:Oxygen