Ventilation / Ventilation Control Tests - Equipment and Equations RET 2414L Pulmonary Function Testing Module 5.0

Equipment and Equations Ventilatory Response to O2

Equipment and Equations Ventilatory Response to O2 Equipment Required Spirometer Pneumotachometer to measure ventilation Pressure Transducer / Mouth Shutter Allows measurement of P100 Bag-in-Box Circuit Allows the patient to rebreathe into a bag to which CO2 or O2 can be added Adjustable Blower Allows the level of CO2 in the system to be maintained at baseline levels (isocapnia)

Equipment and Equations Ventilatory Response to O2 Equipment Required CO2 Scrubber Gas Source O2 / CO2 Gas analyzers Pulse Oximeter Provides data on the patient’s saturation

Equipment and Equations Ventilatory Response to CO2

Equipment and Equations Ventilatory Response to CO2 Equipment Required Same as that used to measure ventilatory response to O2 with two differences Bag is filled with 5% to 7% CO2 in O2 Scrubber is removed from the circuit

Case 4 - 1 T.J. is a 45-year-old man admitted to the hospital for acute shortness of breath. He has never smoked but has a family history of heart disease. His lungs are clear during auscultation. He becomes breathless just moving around the hospital room. He denies any recent respiratory infections. Because of his rapid respiratory rate, his attending physician requested an arterial blood gas test using room air and VD/VT ratio determination Age: 45 Weight: 175 Height: 67 Race: White

Case 4 - 1 Blood Gas Analysis Exhaled Gas Analysis pH 7.49 PCO2 29 PO2 102 HCO3- 21 Hb 14.2 SaO2 98 Exhaled Gas Analysis 24.2 L/min fB 20 breaths/min PECO2 14 mm Hg

Case 4 - 1 Determine VT VT = ____ fB 24.2 20 VT = 1.21 L

Case 4 - 1 Determine VD/VT = (29 – 14) 29 VD/VT = 0.517 or 52% VD/VT = PaCO2 – PECO2 PaCO2 = (29 – 14) 29 VD/VT = 0.517 or 52% Remember, normal is 20% - 40%

Case 4 - 1 Determine = fB (VT – VD) Where: VD = (VD/VT)(VT) Substituting this value for the alveolar ventilation equation = 20(1.21 – 0.626) = 20(0.584) = 11.68

Case 4 - 2 T.B is a 37-year-old man who weighs 275 lb. He was referred to the PFT Laboratory after evaluation in the sleep laboratory revealed obstructive sleep apnea (OSA). He admits to daytime somnolence. Baseline PFTs revealed the following ACT %Predicted FVC 3.2 72% FEV1 2.7 81% FEV1% 84 75 – 85% TLC 4.1 71% RV/TLC 22% 20 – 35%

Baseline blood gas results were as follows: Case 4 - 2 Baseline blood gas results were as follows: pH 7.36 PCO2 47 PO2 77 HCO3- 28 SaO2 93

Case 4 - 2 CO2 response test was performed (breathing a mixture of 7% CO2 in O2 for 4 minutes). The following lab data was obtained: PetCO2 mm Hg (L/min) P100 (cm H2O) 43 4.5 2.2 46 4.4 ---- 50 5.9 ---- 54 7.9 7.8 57 15.1 ---- 59 17.1 12.0 What is the interpretation of: Ventilatory response to CO2 stimulation? Respiratory drive response to CO2 stimulation?

Practice Quiz Module 5.0 A patient with asthma has the following data recorded: : 5.7 L/min fB: 15 What is the patient’s VT? 0.15 L 0.32L 0.38L 0.44L

Practice Quiz Module 5.0 In which of the following condition would increased minute ventilation be expected? Metabolic acidosis Hypoxemia Central nervous system depression CO2 narcosis I and II only III and IV only I, II and III II, III and IV

Practice Quiz Module 5.0 In addition to PaCO2, what other measurement is needed to calculate the VD/VT ratio? Tidal volume Minute ventilation Mixed expired CO2 PaO2

Practice Quiz Module 5.0 Which of the following VD/VT rations would be expected in a patient with a diagnosis of pulmonary embolism? 0.09 0.15 0.25 0.50

Practice Quiz Module 5.0 A COPD patient has his dead space measured as 0.4L. If he is breathing at a rate of 16/min with a VT of 0.8 L, what is his VA? 1.21 L 6.4 L 12.4 L 12.8 L

Practice Quiz Module 5.0 Exhaled gas is collected for 10 minutes; the mixed expired PCO2 is measured. Blood gases are drawn during the last minute of gas collected, and the following data are recorded: PECO2: 28 mm Hg pH: 7.38 PaCO2: 44 PaO2: 69 What is the patient’s VD/VT ratio? 0.63 0.57 0.41 0.36

Practice Quiz Module 5.0 A patient has the following results after 4 minutes of a CO2 rebreathing test: Time 0 4 minutes PetCO2 40 60 VE 4.0 64.0 These findings are consistent with which of the following? Interstitial pulmonary fibrosis Obesity-hypoventilation syndrome COPD Normal lung function

Practice Quiz Module 5.0 Which of the following measurements are consistent with the diagnosis of hyperventilation? PaCO2 of 29 mm Hg of 6.5 L/min pH of 7.52 VD/VT of 0.49 I and III only II and IV only I, II and IV I, II, III and IV

Practice Quiz Module 5.0 P100 is which of the following? Pressure during the first 100 msec of an occluded breath PaO2 when the patient breaths 100 L/min Minute ventilation when the patient is breathing 100% O2 Mouth pressure at a respiratory rate of 100/min