However, they are temporally separated in most patients in natural history. Since PND and orthopnea share a close relationship in terms of pathophysiology, we cluster it together in symptomatology. However, as heart disease (as in cardiomyopathy ) worsens the pulmonary interstitium shows some reactive fibrotic changes resist water logging in the lungs. These patients, later on, can get into the same cycle of PND. Many of these patients, however, do get into sleep after some time as some sort of compensation or adaptation to neural signals of dyspnea take place. Orthopnea has no time lag.It occurs immediately hence it is obviously more severe. No.It has very low sensitivity to predict severity of heart disease.Ĭan PND and Orthopnea occur at same patient at same time a same day ? It has low sensitivity( <30% ) but up to 75% specificity to diagnose heart disease.(Class 3 Non-Expert Evidence) What is the sensitivity of PND for predicting heart disease? Since its a volume-dependent pulmonary hemodynamic stress, a diuretic at dusk will prevent these episodes in many. Because PND requires a time lag of at least few hours.Usually, these patients will not sleep thereafter or the usual wake-up time ensues. How many episodes of PND can occur in one night? PND can never predict which day its going to come as there is CNS component to the circuit in triggering this. PND vs Orthopnea: Which is a reproducible symptom? If rales appear immediately after lying down it may Indicate severely compromised LV function. But it should be emphasized in orthopnea patients, rales are rare since it takes some time for lung congestion take place. Is basal rales mandatory during episodes of PND? *Postural changes in LA mean pressure is a complex topic of physics involving lungs, pulmonary circulation, and LA mean pressure. How do pillows give relief of dyspnea in acute LVF? Few of the above mechanism operates) Finally seeking the window is spontaneous, in search for better fractional oxygen content from the atmosphere. V/Q mismatch improves as more lungs get perfusion in an erect posture. Apart from this two more factors contribute. The gravitational forces emerge* and aid in LV filling and improve stroke volume and relieve the congestion backlog. Further standing up (even sitting up is sufficient) brings the left atrium in its natural superior position, compared to LV. Since symptoms are due to sudden unexpected congestion during sleep, assuming erect posture slows down the venous return of 400 ml instantly. The relief is completely in many unless the ongoing trigger and baseline cardiac defect overwhelms the reserve mechanism. sits up, often to stand up, and go to the nearest window and try to breathe fast and an episode of dyspnea settles down in a few minutes. The classical description is, the patient wakes up from sleep. Some Infrequently asked questions in (iFAQ) in PND
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