Pulmonary Function Tests PFT s

1. Pulmonary Function Tests (PFT�s) Scott Stevens D.O. Gannon University College of Health Sciences Graduate Program � Department of Nursing

2. Pulmonary Function Tests (PFT�s) A nonspecific term used most often to describe only spirometry Pulmonary tests include: chest x-ray (CXR), arterial blood gas (ABG), Spirometry with FEV1sec, FVC, FEV1/FVC, FEF 25-75, Flow-volume loops, Ventilation-perfusion (V/Q) scan, Pulse oximetry (SpO2), SaO2 from ABG, Mixed venous oxygen (PvO2) and saturation from pulmonary artery catheter

3. PFT Indications Possible pneumonectomy or lobectomy Surgery of upper abdomen History of pulmonary disease: COPD, bronchitis, emphysema, pulmonary fibrosis, significant smoking history Severe obesity, obstructive sleep apnea (OSA), pickwickian syndrome (obesity, decreased pulmonary function, polycythemia) Evidence of pulmonary dysfunction during history and physical exam Dyspnea = shortness of breath, SOB DOE = dyspnea on exertion

4. Patients at risk for post-op pulmonary complications Significant history of pulmonary disease Thoracic or abdominal (esp. upper) surgery Obesity Long-term smokers Elderly patients (>70 yrs)

5. High risk PFT results FEV1 < 2L FEV1/FVC < 0.5 VC < 15cc/Kg in adult & < 10cc/Kg in child VC < 40 to 50% than predicted

6. Why get PFT�s preoperatively? By estimating pulmonary reserve one can better plan and predict pre-, intra- and post-operative pulmonary care requirements

7. Preoperatively Goal is to treat any reversible conditions, optimize pt Bronchodilators: testing will show any improvement with treatment, adjust doses Most important in patients with a >15% improvement in FEV1 after treatment Bronchitis: optimize patient respiratory therapy, bronchodilators for bronchospasm antibiotics to treat infection, sputum for culture and sensitivity (C&S) Optimize CHF

8. Intraoperatively Ventilator adjustments Severe emphysema requires longer expiratory times (normal I:E is 1:2, so in COPD ? 1:3) Closely monitor peak inspiratory pressures (PIP) to avoid rupturing an emphysematous bleb CO2 retainers: EtCO2 should be keep near the pt�s baseline, a rapid correction will lead to metabolic alkalosis Bronchospasm: avoid *histamine releasing drugs Pentothal (STP), Morphine (MSO4), Atracurium, Mivacurium, Neostigmine Tx with nebulized albuterol

9. Postoperatively Extubation: If FEV1 is >50% predicted than extubation probably will not be effected If FEV1 is between 25 � 50%, with some hypoxemia and hypercarbia � prolonged intubation probable If FEV1 is <25% predicted � only life saving procedures should be done, regional anesthesia if possible, long term ventilatory support, possible inability to wean from ventilator, tracheostomy probable *Extubation criteria: VSS, awake & alert, resp. rate < 30 ABG on FiO2 of 40% ? PaO2 >70 and PaCO2 <55 MIF is more negative than -20cm H2O Vital capacity (VC) > 15cc/Kg

10. Acute respiratory failure *Intubation criteria: Mechanics: RR>35, VC <15cc/Kg in adult or <10cc/Kg in child, MIF more neg. than -20cmH2O Oxygenation: PaO2 < 70mmHg on FiO2 of 40%, A-a gradient > 350mmHg on 100% O2 Ventilation: PaCO2 > 55 (except in chronic hypercarbia), Vd/Vt > 0.6 (remember normal dead space is 30%) Clinical: airway burn, chemical burn, epiglottis, mental status change, rapidly deteriorating pulmonary status, fatigue

11. Normal CXR

12. Expiratory CXR

13. Inspiratory CXR (same pt)

14. Expiratory CXR for pneumothorax (PTX)

15. Tension Pneumothorax

16. CHF or excessive IV fluids

17. RUL consolidation ? aspiration

18. ABG Results: pH / PCO2 / PO2 / bicarbonate / base excess Usually obtained from radial, brachial, femoral, axillary, or dorsalis pedis artery Drawn in heparinized syringe Must be measured within 15 minutes or glycolysis will occur with lactic acid production, decreased pH, and increased PCO2 Sample can be stored on ice for 1 to 2 hours Heparin may significantly lower PCO2 by dilution, esp. in children when small samples taken

19. ABG normal values pH: 7.35 � 7.45 PCO2: 35 � 45 mmHg PO2: 75 � 105 mmHg Bicarbonate: 20 � 26 mmoles/L Base excess: -3 to +3 mmoles/L

20. pH Acidemia = blood pH < 7.35 Alkalemia = blood pH > 7.45 Acidosis = a process which causes acid to accumulate Alkalosis = a process which causes alkali accumulation Altered pH ? next determine if respiratory (CO2) or metabolic (HCO3-) Buffers: substance that can absorb or donate H+ Bicarb(HCO3-), Hb, serum proteins, phosphate(HPO4-)

21. PaCO2 Hypercapnia � increased CO2 Hypocapnia � decreased CO2 *Rule: an increase of PCO2 by 10 mmHg causes a decrease in pH by 0.08, likewise, a decrease of PCO2 by 10 mmHg will increase pH by 0.08 So an acute increase in CO2 to 60 should cause a drop in pH to 7.24

22. PaO2 Hypoxemia = decreased PO2 in blood, < 75 Hypoxia = a low O2 state A-a gradient � a measure of efficiency of lung PAO2 = (PB-PH2O)*(FiO2) � (PaCO2/0.8) PAO2 = (760-47)*(0.21) � (40/0.8) = 100 PAO2 = (760-47)*(0.5) � (40/0.8) = 306 PAO2 = (760-47)*(1) � (40/0.8) = 663 Normal A-a = approximately (Age / 3) A-a gradient is widened during anesthesia and with intrinsic lung Dz: PTX, PE, shunt, V/Q mismatch, diffusion problems A-a gradient is normal with hypoventilation or low FiO2 Tx is supplemental O2, adjust ventilation, tx atelectasis, add PEEP, tx underlying cause

23. Bicarbonate A calculated value from: [H+] = 24 * (PaCO2/[HCO3-]) Values alter due to acidosis/alkalosis Base excess is calculated directly using PaCO2, pH, and bicarbonate values Rule: a decrease in bicarb. by 10 mmoles decreases the pH by 0.15, likewise, an increase in bicarb. By 10 mmoles increases pH by 0.15 A bicarb. of 13 would result in a pH of 7.25 Total body bicarb. deficit = (base deficit * wt in Kg * 0.4), in mEq/L, usually replace � of deficit

24. Respiratory Acidosis Low pH & High PaCO2 Acute and chronic causes: Hypoventilation with hypercarbia CNS depression � trauma, drugs Decreased FRC � obesity Upper or lower airway obstruction COPD, asthma, pulmonary fibrosis After 1-2 days renal compensation occurs H+ excreted by kidney and HCO3- reabsorbed into blood to partially correct pH

25. Respiratory Alkalosis High pH & Low PaCO2 Hyperventilation with hypocarbia Causes: hypoxic respiration, CNS Dz, encephalitis, anxiety, narcotic withdrawl, pregnancy, early septic shock, hypermetabolic states, artificial ventilation Renal compensation will occur causing increased excretion of HCO3- and decreased secretion of H+ which partially corrects pH

26. Metabolic Acidosis Low pH & Low HCO3- Causes: lactic acidosis from hypoperfusion, DKA, renal Dz with bicarb loss (anion gap and K+), HCO3- loss in diarrhea, ASA ingestion, high protein intake Respiratory compensation (central chemoreceptors) with hypocarbia, more rapid than renal compensation, partial correction Kidneys may increase H+ excretion

27. Metabolic Alkalosis High pH & High HCO3- Causes: bicarb. infusion, metabolism of lactate or citrate, loss of H+ from vomiting or excessive NGT suctioning Respiratory compensation by limited hypoventilation due to eventual hypoxic drive, partial correction Kidneys may increase bicarb. excretion in urine

30. Spirometry

31. FEV-1 second After maximal inspiration, the volume of air that can be forcefully expelled in one second Effort dependent Normally between 3 � 5 L Also reported as percent predicted Also reported as a percent of FVC FEV1 / FVC ? normally > 75% Most important clinical tool in assessing the severity of airway obstructive disease

32. FEV1

33. Degree of risk in obstructive lung disease RISK FEV1 / FVC Normal > 75 Mild 60-75 Moderate 45-60 Severe 35-45 Extreme < 35

34. Flow-Volume loop

35. Flow-volume loops Helps distinguish between upper airway obstruction (extrathoracic) and generalized pulmonary disease (intrathoracic) An extrathoracic obstruction decreases inspiratory flow An intrathoracic obstruction decreases expiratory flow

37. FEF 25-75 Forced expiratory flow at 25 to 75% of FVC Effort independent Reflects collapse of small airways, peripheral airways Sensitive indicator of early airway obstruction

38. MVV or MBC Maximal voluntary ventilation Maximal breathing capacity �will to live� test The maximal amount of air a pt can exhale in one minute at maximal effort (hyperventilation) Extremely effort dependent, nonspecific Tests motivation, mechanics, strength, and endurance A decrease has been shown to predict increased morbidity and mortality in pts undergoing thoracic surgery

39. That�s All For Today