Clinical Trial: Pulmonary Vascular Effects of Respiratory Rate & Carbon Dioxide

Study Status: Withdrawn
Recruit Status: Withdrawn
Study Type: Interventional

Official Title: The Pulmonary Vascular Consequences of Divergent Strategies for Low Tidal Volume Ventilation: Hypercapnia or High Respiratory Rate?

Brief Summary: The purpose of this protocol is to perform serial physiological measurements and blood testing on mechanically ventilated patients comparing conditions of eucapnia and hypercapnia in the same patient. We will be testing two hypotheses: (1) while administering inspired carbon dioxide (CO2), eucapnia achieved by high respiratory rate (EHR) significantly decreases pulmonary artery pressures compared to hypercapnia with a lower respiratory rate (HLR), and (2) that EHR decreases myocardial strain compared to HLR.

Detailed Summary:

The purpose of this protocol is to perform serial physiological measurements and blood testing on mechanically ventilated patients comparing conditions of eucapnia (maintaining alveolar ventilation to target carbon dioxide partial pressure (pCO2) 35-40 mm Hg) and hypercapnia (providing inspired CO2 to target pCO2 55-60 mm Hg) in the same patient. This prospective clinical study will enroll consenting adult patients scheduled for elective cardiac surgery and who require postoperative mechanical ventilation, pulmonary artery (Swan-Ganz) catheter monitoring, and arterial catheterization as part of routine standard care during the immediate postoperative period. The study will perform measurements using available ventilator monitors, ventilator in-line pneumotachograph and capnograph, measurements from the indwelling pulmonary artery catheter, transesophageal echocardiography, and other measurements available as part of routine care. The entire experimental protocol will be performed in one day over 2-4 hours, and the protocol will not interfere with routine postoperative care, nor prolong the need for mechanical ventilation, pulmonary artery catheterization, arterial catheterization, or intensive care unit length of stay.

Ventilation with low tidal volumes has been shown definitively to improve mortality from acute respiratory distress syndrome (ARDS)1 and may provide benefit even in patients without ARDS.2 During low tidal volume ventilation, practice varies on whether to allow some degree of alveolar hypoventilation with incidental hypercapnic acidosis (termed "permissive hypercapnia"),3 or to increase respiratory rate to maintain alveolar ventilation and target eucapnia, often requiring respiratory rates > 30/min.4 The physiological consequences of these divergent strategies remain to be fully elucidated. We propose the following study to distinguish the effe
Sponsor: Beth Israel Deaconess Medical Center

Current Primary Outcome: mean pulmonary artery pressure (mPAP) [ Time Frame: 4 hours ]

Pulmonary artery pressure will be measured directly by transducing the pulmonary artery catheter, and will include systolic (PASP) and diastolic (PADP) Ppa. The mean pulmonary artery pressure (mPAP) will be calculated according to the formula: mPAP = 1/3 PASP + 2/3 PADP


Original Primary Outcome: Same as current

Current Secondary Outcome: Right ventricular systolic function [ Time Frame: 4 hours ]

Right ventricular systolic function will be assessed using strain echocardiography or peak tricuspid annular systolic velocity.


Original Secondary Outcome: Same as current

Information By: Beth Israel Deaconess Medical Center

Dates:
Date Received: August 20, 2013
Date Started: September 2013
Date Completion:
Last Updated: February 24, 2017
Last Verified: August 2014