Clinicians caring for children or adults with pulmonary arterial hypertension (PAH) face a number of challenges, not the least of which is determining whether a patient has met treatment targets based on changes in a given test (such as the 6-min walk distance (6MWD)) and whether these changes translate to meaningful improvements in that patient's quality of life or survival. While several trea...

The variational derivative of a functional J[y] can be defined as δJ/δy = F y (x, y, y ′)− d dx F y ′ (x, y, y ′) [1, pp. 27–29]. Euler's equation essentially states that the variational derivative of the functional must vanish at an extremum. This is analogous to the well-known result from calculus that the derivative of a function must vanish at an extremum. In this section, we consider a sim...

Infrared oculography was performed during sustained lateral gaze in 12 normal subjects to investigate end-point nystagmus while fixating a target light. Five failed to develop nystagmus despite deviation up to 40 degrees from 4 to 5 min. Six subjects developed nystagmus immediately or shortly after reaching the deviated position. In one, the nystagmus (0.5 degrees to 1 degree and 1.0 Hz) began ...