ABSTRACT
The views expressed herein are those of the authors and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the U.S. Government.
COHb Carboxyhemoglobin
CPET Cardiopulmonary exercise testing
CXR Chest radiograph DLCO Carbon monoxide diffusing capacity
EBCT Electron beam computed tomography
ECG Electrocardiogram
EELV End-expiratory lung volume (EELV¼TLC – IC) EILV End inspiratory lung volume (EILV¼TLV – IRV) EVH Eucapneic voluntary hyperventilation
ExtFVL Exercise tidal flow-volume loop
f Respiratory frequency FEV1 Forced expiratory volume in first second of exhalation
FVL Flow-volume loop
FVC Forced vital capacity
GERD Gastroesophageal reflux disease
GFR Glomerular filtration rate
HCO3 Serum bicarbonate
HIV Human immunodeficiency virus
HR Heart rate HRCT High resolution computed tomography
HRR Heart rate reserve
IET Incremental cardiopulmonary exercise test
IC Inspiratory capacity
ILD Interstitial lung disease
MEP Maximum expiratory pressure
MFVL Maximal volitional flow-volume envelope
MIP Maximum inspiratory pressure MVV Maximum voluntary ventilation
O2 Oxygen
O2 pulse VO2/HR, a noninvasive estimate of stroke volume
PAH Pulmonary arterial hypertension
PaO2 Arterial partial pressure of oxygen
P(A-a) O2 Alveolar-arterial difference in partial pressure of oxygen
PETCO2 Partial pressure of end tidal CO2 PETO2 Partial pressure of end tidal O2 PVO2 Venous partial pressure of oxygen
RER Respiratory exchange ratio
RV Residual volume
SaO2 Arterial oxygen saturation
SpO2 Noninvasive oxygen saturation measured by pulse oximetry
SV Stroke volume
TLC Total lung capacity
VCD Vocal cord dysfunction
V˙CO2 Carbon dioxide output V˙D/V˙T Dead space to tidal volume ratio V˙E Minute ventilation V˙Emax Maximal V˙E achieved during exercise V˙E/V˙CO2 Minute ventilation over carbon dioxide output, a marker of
ventilatory efficiency
V˙E/V˙O2 Minute ventilation over oxygen uptake, a marker of ventilatory efficiency
V˙O2 Oxygen uptake V˙O2/kg Oxygen uptake normalized for body mass V˙O2max Maximal oxygen uptake value V˙O2peak Peak oxygen consumption V/Q Ventilation/Perfusion
VR Ventilatory reserve (V˙Emax/MVV; MVV – V˙Emax) V-slope Plot of V˙CO2 vs. V˙O2, used to determine anaerobic threshold V˙T Tidal volume VTE Venous thromboembolism
WR Work rate
I. Introduction
Dyspnea is a common complaint. An estimated 3-25% of the general community has been reported to complain of shortness of breath (1). Dyspnea is the presenting complaint for 3.7% of ambulatory medicine visits (2), 2.7% of emergency department visits (3), and 15-25% of all hospital admissions (4,5).
