title: End tidal CO(2) tension: pulmonary arterial hypertension vs pulmonary venous hypertension and response to treatment.
abstract: BACKGROUND
  CO(2) excretion is impaired in pulmonary arterial hypertension (PAH) due to underlying vascular obstruction and increased dead space. Our aim was to determine whether resting end tidal CO(2) (Etco(2)) could differentiate patients with PAH from those with pulmonary venous hypertension (PVH) or patients without pulmonary hypertension (PH) and whether successful treatment of PAH resulted in higher Etco(2) values.
  
  
  METHODS
  We performed Etco(2) measurements for five breaths at rest and after a 6-min walk test (6MWT) in patients seen at our pulmonary vascular center. Mean Etco(2) values were correlated with 6-min walk distance and right-sided heart catheterization data.
  
  
  RESULTS
  We enrolled 84 patients with PAH, 17 with PVH without left ventricular systolic dysfunction, and seven with no PH and no severe alterations in pulmonary function testing. Etco(2) was significantly lower in patients with PAH than in those with no PH and PVH (P < .0001 PAH vs both groups). Etco(2) correlated with the pulmonary artery diastolic pressure-to-pulmonary artery occlusion pressure gradient (r = -0.50, P = .0002) and pulmonary vascular resistance (r = -0.44, P = .002). Etco(2) after 6MWT correlated with walk distance (r = 0.34, P = .003). In patients with prostaglandin therapy escalation, Etco(2) increased in those who had clinical improvement, whereas in patients who did not improve clinically, Etco(2) failed to rise (P = .04).
  
  
  CONCLUSIONS
  Etco(2) is a promising tool to differentiate patients with PAH from those with PVH or no PH, correlates with diagnostic and prognostic hemodynamic indicators, and may increase with successful treatment of PAH.
authors.affiliation: Division of Allergy, Pulmonary and Critical Care Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN. Electronic address: anna.r.hemnes@vanderbilt.edu.
authors.forename: Anna R
authors.initials: AR
authors.lastname: Hemnes
authors.affiliation: Division of Allergy, Pulmonary and Critical Care Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Meredith E
authors.initials: ME
authors.lastname: Pugh
authors.affiliation: Division of Allergy, Pulmonary and Critical Care Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Newman
authors.affiliation: Division of Allergy, Pulmonary and Critical Care Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Ivan M
authors.initials: IM
authors.lastname: Robbins
authors.affiliation: Division of Allergy, Pulmonary and Critical Care Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: James
authors.initials: J
authors.lastname: Tolle
authors.affiliation: Division of Allergy, Immunology and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Austin
authors.affiliation: Division of Allergy, Pulmonary and Critical Care Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: John H
authors.initials: JH
authors.lastname: Newman
mesh_terms: D000328:Adult; D000959:Antihypertensive Agents / Q000627:therapeutic use; D019540:Area Under Curve; D019296:Capnography; D002245:Carbon Dioxide / Q000378:metabolism*; D016022:Case-Control Studies; D011464:Epoprostenol / Q000627:therapeutic use; D005080:Exercise Test; D005260:Female; D006439:Hemodynamics; D006801:Humans; D006976:Hypertension, Pulmonary / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018709:Statistics, Nonparametric; D013990:Tidal Volume; D016896:Treatment Outcome
chemical_list: D000959:Antihypertensive Agents; D002245:Carbon Dioxide; D011464:Epoprostenol