clinical assessment of respiratory disease Flashcards
lung function tests: explain the use of lung function tests and recall how they may change in patients with respiratory disease, and explain the pressure-volume relationship for inspiration and expiration in health and disease
describe process of spirometry
wearing a noseclip, patient inhales to TLC, then exhales as hard and fast as possible for six seconds into vitalograph
effect of obstructive pulmonary disease on spirometry reading
much slower exhalation rate, forced expiration volume lower, FEV1:FVC (forced expiratory volume in 1 second to forced vital capacity) ratio lower 25% (FEV1 much lower)
effect of restrictive pulmonary disease on spirometry reading
similar rate to normal but lower forced expiratory volume as airways are fine but volume affected (FEV1 and FVC lower)
what is peak flow
measures peak expiratory flow rate (maximum speed of expiration)
image of spirometry graph with normal, restrictive and obstructive patients
benjis
process of creating flow volume loop
patient wraps lips round mouthpiece → patient completes at least one tidal breath (A&B) → patient inhales steadily to TLC (C) → patient exhales as hard and fast as possible (D) → exhalation continues until RV is reached (E) → patient immediately inhales to TLC (F)
image of flow volume loop
benjis
what does the green section show
tidal breathing (slow and limited)
on red, what should the rate be after peak expiratory flow
linear
what does the respiratory flow envelope (red and blue lines) demarcate
maximum rates
effect of mild (obstructive) COPD on flow volume loop
volume increases as lungs get larger (displaced to left with higher residual volume); coving occurs (indented exhalation curve) as smaller airways offer lower flow rates, decreased peak flow
effect of severe (obstructive) COPD on flow volume loop
capacity decreases further and coving increases
effect of restrictive disorders on flow volume loop
operating at lower volumes (displaced to right with lower residual volume) as less access to air; normal/slightly lower peak expiratory flow peak (narrower curve), as filling, not moving gas, is the problem, narrower curve as decreased total lung capacity
flow volume loops of mild COPD, severe COPD and restrictive disease
benjis
effect of variable extrathoracic obstruction on flow volume loop
blocked inhalation (chest can’t expand) decreasing inspiratory flow rate, so blunted inspiratory curve
