Pulmonary function Testing lecture for Nursing students

By Elizabeth Kelley Buzbee AAS, RRT-NPS, RCP

 http://www.nationaljewish.org/patient-info/progs/pps/tests/pulmonary-test.aspx#1

 

1.                  Describe pulmonary function studies.

a.     What are lung volumes? When we measure the volumes we are looking for how deeply a patient can inhale and how much he can exhale.

                                                             i.      Vt: the normal in and out of daily breathing

                                                          ii.      IRV: inspiratory reserve volume, at the end of a normal exhalation how much air can one pull in.

                                                       iii.      ERV: expiratory reserve volume, at the end of a normal exhalation how much air can one exhale

                                                        iv.      RV: air left in the chest that never leaves. [the exact amount can increase or decreased based on pathology]

b.    The spirometer measures volume of air that enters and exits the lung so we directly measure the Vt, and ERV and IRV. There are special tests to determine how much air is left in the lungs at the end of a forced exhalation so the RV is indirectly measured. [picture of body box]

c.     What are lung capacities? Combinations of 2 or more volumes.

                                                            i.      TLC = all 4

                                                        ii.      VC = all but RV

                                                     iii.      IC = IRV + Vt

                                                      iv.      FRC = ERV + Vt

2.               What are the indications for PFT?

a.     To identify and to track the presence of obstructive or restrictive lung disease

b.    To screen out fragile patients prior to initiation of pulmonary rehab or prior to surgery

c.     Evaluate patient’s condition prior to weaning from the ventilator [this one is a modified group of PFTs]

3.               What are the hazards of PFT?

a.     Fatigue

b.    hypoxia

c.     Bronchospasm

d.    Inaccurate data; unlike blood tests this data is frequently patient effort dependent. In order to make sure the studies are accurate, the RCP may have to duplicate test. For instance: we can take a PEFR to determine the level of obstruction due to wheezing and airway collapse however we may also measure the patient’s FEV1 or his average flow rates to validate this data.

 

4.               Identify the kind of information one finds in derangements of pulmonary functions.

a.    In a complete PFT, we may measure a dozen parameters, but we actually are only asking 2 or 3 questions.

                                                             i.      Is there obstruction from occluded airways?

                                                          ii.      Is there restriction on the ability of the lung to inflate?

                                                       iii.      Is there a diffusion problem where 02 doesn’t enter the bloodstream as it should

          b. flow volume loops http://www.spirxpert.com/rustlus.htm

 

a.     Problems with gas flow [obstructive defects]:

                                                             i.      When there is significant bronchospasm, the exhaled flow rates will drop. The airways are too tight for air to exit any faster.

                                                          ii.      Where there is significant airway disease, the patient can air trap as gas fails to exit completely

b.    Problems with volume [restrictive defects]:

                                                             i.      Patient’s with stiff lungs from problems associated with the alveoli will have problems getting air into their chest, so their volumes will be down

c.     Problems with diffusion of gases [diffusion defect]

                                                             i.      Basically anyone who is hypoxic will also have diffusion problems due to flow problems or volume problems. If the patient has no flow or volume defects but still has decreased diffusion of 02, we worry about things like emboli

d.   Problems with distribution of gases

                                                             i.      There is a specific route for gas to exist. The first to fill are the bottom alveoli which are also the first to empty.

                                                          ii.      Some patients with airway problems will have trouble completely emptying different portions of the lungs in the sequence we expect—they have distribution problems [usually due to air flow difficulties.]

5.               What parameters affect these values

                                                             i.      Patient’s height / BSA is the classic way to establish PFT norms

                                                          ii.      Patient’s gender: women tend to do less well than men

                                                       iii.      Patient’s age: like everything else PFT deteriorate with age, but patient’s overall body condition will determine how well they do

                                                        iv.      Race: debates right now

6.                How does the nurse prepare her patient for PFT?

a.     PFT are hard work even for normal folks; and for a COPD patient can be very tiring. Send them to the PFT lab with their oxygen running and on. If oxygen is ordered “only as needed”---this is the one time they really need it.

b.    PFT can trigger bronchospasm in persons with cholinergic reflex bronchospasm

c.     One can get false readings if the patient has received a bronchodilator prior to the test. As soon as the PFT is scheduled you tell the RCP to hold the treatment and the RCP and the PF Tech should be in communication. The PF Tech will administer the drugs

d.    If possible, we try to hold systemic bronchodilators like theophylline

e.     Eating light is ok.