Vol. 93, Issue 4, 1515-1526, October 2002
INNOVATIVE TECHNIQUES
Phonospirometry for noninvasive measurement of ventilation:
methodology and preliminary results
Cheng-Li
Que1,
Christof
Kolmaga1,
Louis-Gilles
Durand2,
Suzanne M.
Kelly1, and
Peter T.
Macklem1
1 Meakins-Christie Laboratories, Montreal Chest
Institute, Royal Victoria Hospital, Montreal, Quebec H2X 2P2;
2 Institut de Recherches Cliniques de
Montréal, University of Montreal, Montreal, Quebec,
Canada H2W 1R7
We measured tracheal flow from
tracheal sounds to estimate tidal volume, minute ventilation
(
I), respiratory frequency, mean inspiratory flow
(VT/TI), and duty cycle (TI/Ttot).
In 11 normal subjects, 3 patients with unstable airway obstruction, and
3 stable asthmatic patients, we measured tracheal sounds and flow
twice: first to derive flow-sound relationships and second to obtain
flow-volume relationships from the sound signal. The flow-volume
relationship was compared with pneumotach-derived volume. When subjects
were seated, facing forward and with neck rotation, flexion, and
standing, flow-volume relationship was within 15% of
pneumotach-derived volume. Error increased with neck extension and
while supine. We then measured ventilation without mouthpiece or nose
clip from tracheal sounds during quiet breathing for up to 30 min.
Normal results ± SD revealed tidal volume = 0.37 ± 0.065 liter, respiratory frequency = 19.3 ± 3.5 breaths/min, I = 6.9 ± 1.2 l/min,
VT/TI = 0.31 ± 0.06 l/s, and TI/Ttot = 0.37 ± 0.04. Unstable airway obstruction had large I due to
increased VT/TI. With the exception of
TI/Ttot, variations in ventilatory parameters were closer
to log normal than normal distributions and tended to be greater in
patients. We conclude that phonospirometry measures ventilation
reasonably accurately without mouthpiece, nose clip, or rigid postural constraints.
minute ventilation; pattern of breathing; breath sounds; tidal
volume; breathing frequency
