Phonospirometry for noninvasive measurement of ventilation: methodology and preliminary results.

We measured tracheal flow from tracheal sounds to estimate tidal volume, minute ventilation (VI), 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, VI = 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 VI 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.

The burden of illness in patients with moderate to severe chronic obstructive pulmonary disease in Canada.

INTRODUCTION: No recent Canadian studies with physician- and spirometry-confirmed diagnosis of chronic obstructive pulmonary disease (COPD) that assessed the burden of COPD have been published. OBJECTIVE: To assess the costs associated with maintenance therapy and treatment for acute exacerbations of COPD (AECOPD) over a one-year period. METHODS: Respirologists, internists and family practitioners from across Canada enrolled patients with an established diagnosis of moderate to severe COPD (Global initiative for chonic Obstructive Lung Disease stages 2 and 3) confirmed by postbronchodilator spirometry. Patient information and health care resources related to COPD maintenance and physician-documented AECOPD over the previous year were obtained by chart review and patient survey. RESULTS: A total of 285 patients (59.3% male; mean age 70.4 years; mean pack years smoked 45.6; mean duration of COPD 8.2 years; mean postbronchodilator forced expiratory volume in 1 s 58.0% predicted) were enrolled at 23 sites across Canada. The average annual COPD-related cost per patient was $4,147. Across all 285 patients, maintenance costs were $2,475 per patient, of which medications accounted for 71%. AECOPD treatment costs were $1,673 per patient, of which hospitalizations accounted for 82%. Ninety-eight patients (34%) experienced a total of 157 AECOPD. Treatment of these AECOPD included medications and outpatient care, 19 emergency room visits and 40 hospitalizations (mean length of stay 8.9 days). The mean cost per AECOPD was $3,036. DISCUSSION: The current costs associated with moderate and severe COPD are considerable and will increase in the future. Appropriate use of medications and strategies to prevent hospitalizations for AECOPD may reduce COPD-related costs because these were the major cost drivers.