Table 2.

Causes of unexplained and persistent dyspnea across different diagnostic algorithms.

	Del Paso et al (16)	Martinez et al (18)	Pratter et al (17)	Huang et al (22)
Patients	N=77	N=50	N=123	N=530
Diagnosis made in n=	63	49	122	530
Respiratory	36%	32%	53%	17%
	Asthma Intrathoracic focal obstruction of a large airway Extrathoracic upper airway obstruction	Hyperactive airways Interstitial lung disease Other lung diseases	Airflow obstruction Interstitial lung diseases Other lung diseases	Pulmonary hypertension
Cardiovascular/circulatory	14%	10%	16%	18%
	Coronary artery disease Arrhythmias Constrictive pericarditis	Ischemic Heart Disease Heart Failure with preserved ejection faction Atrial septal defect	Congestive heart failure/other cardiomyopathies Valvular heart disease Other	Heart failure with preserved ejection fraction
Non-cardiopulmonary	50%	60%	31%	65%
	Hyperventilation syndrome Poor conditioning Gastroesophageal Reflux disease Thyroid disease Unexplained	Obesity/deconditioning Psychogenic, normal Gastroesophageal Reflux disease	Obesity Psychogenic Deconditioning Others	Primary hyperventilation Dysautonomia Oxidative myopathy Others