1. Respiratory I Wendy Phelps Lafreniere, RN, MSN, CCRN Nursing 487 – Fall 2016 Chapter 10 – Determinants and Assessment of Pulmonary Gas Exchange

2. Objectives 1.Describe the function and role of the pulmonary system; 2.Explain pulmonary perfusion and determine abnormalities of perfusion; 3.Identify normal values for and interpret arterial blood gases differentiating between respiratory acidosis and alkalosis and metabolic acidosis and alkalosis; 4.Describe a focused respiratory nursing history and assessment; 5.Describe tests and procedures used to evaluate pulmonary function and oxygenation and list normal values.

3. Functions Protect and defend Exchange of gases ◦ Intact neuro system ◦ Compliant lungs ◦ Adequate WOB ◦ Adequate hemodynamic/cardiovascular function

4. Respiratory Tract -REVIEW Protective functions Conducting airway contains a mucociliary system ◦ in high-acuity patients, initial conducting airway is bypassed if intubated

5. Respiratory Process 1. Ventilation 2. Respiration 3. Perfusion

6. Ventilation Actual work of breathing Air exchanged with the atmosphere Changing size of thorax ◦ inspiration/expiration Air moves from area of higher pressure to one of lower pressure Inside lungs – lower pressure – inspire until pressure slightly higher – then expiration

7. Lung Compliance & Ventilation Ability of lungs to expand and recoil As alveoli approach filling capacity, they lose compliance and can eventually burst Can use PEEP (positive end-expiratory pressure) to increase compliance – but too much PEEP can cause damage

8. Lung Compliance Compliance sensitive to conditions that affect lung's tissues ◦ deficiency of surfactant leads to decreased compliance ◦ “stiff lungs" ◦ increases work of breathing, decreases tidal volume ◦ restrictive pulmonary disorders

9. Respiration The body's cells are supplied with oxygen, and carbon dioxide is eliminated Internal respiration – movement of gas across systemic-capillary cell membranes in the tissue External respiration – movement of gas across the alveolar-capillary membranes ◦ both use diffusion to exchange gases

10. Diffusion Factors that affect diffusion ◦ Gradient ◦ Surface Area ◦ Thickness ◦ Length of exposure

11. Figure 10-5: Oxyhemoglobin dissociation curve. The percent O 2 saturation of hemoglobin and total blood oxygen volume are shown for different oxygen partial pressures (PO 2 ). Arterial blood in the lungs is almost completely saturated. During one pass through the body, about 25% of hemoglobin-bound oxygen is unloaded to the tissues. Thus, venous blood is still about 75% saturated with oxygen. The steep portion of the curve shows that hemoglobin readily off-loads and on-loads oxygen at PO 2 levels below the 50mmHg.

12. Figure 10-6: Oxyhemoglobin dissociation curve right and left shifts. Normally, when hemoglobin is 50 percent saturated with oxygen (P50) the PaO 2 will be 27 mm Hg. The P50 changes when physiologic factors are altered, shifting the curve. A shift to the left increases the affinity of oxygen to hemoglobin, inhibiting its release to tissues. A shift to the right decreases the affinity of oxygen to hemoglobin, making it release to tissues more readily. LeMone & Burke. (2008).

13. Shifts in OxyHgb curve Left Shift: ◦ Hgb and oxygen have increased affinity ◦ Alkalosis ◦ Low metabolism Right Shift: ◦ Hgb and oxygen have decreased affinity ◦ More oxygen released ◦ Acidosis ◦ High metabolism

14. Perfusion Third component of respiratory process Pumping or flow of blood into tissues and organs Two circulatory systems ◦ systemic system ◦ pulmonary system  depends on systemic system

15. Perfusion Cardiac output Gravity Pulmonary Vascular Resistance

16. Cardiac Output CO = SV x HR Normal cardiac output 4-8 liters per minute Stroke volume a function of ventricular preload, afterload, and contractility MAP = Mean arterial pressure ◦ MAP < 60 mmHg is inadequate ◦ clinical goal to maintain MAP at 65 or above

17. Gravity Effects of gravity on blood are important Blood has weight Naturally flows toward dependent areas of body

18. Pulmonary Vascular Resistance PVR Resistance to blood flow in pulmonary vascular system Affected by:  Length of vessels  Radius of vessels  Viscosity of blood

19. Vessel Radius Determinants Pulmonary vasoconstriction occurs in response to hypoxia, hypercapnia, and acidosis ◦ vasoconstriction is a major cause of increased pulmonary vascular resistance (PVR) ◦ hypoxia is strongest stimulant for pulmonary vasoconstriction ◦ when an area of the lung becomes hypoxic, vasoconstriction is triggered

20. Ventilation-Perfusion Relationship V/Q ratio – measurement of alveolar ventilation and pulmonary perfusion Balance of ventilation to perfusion affected by PaO 2 and PaCO 2 Balance depends on adequate diffusion of oxygen and carbon dioxide Should significant imbalance develop, normal gas exchange cannot take place in affected areas

21. Figure 10-8 The relationship of ventilation to perfusion.

22. Ventilation-Perfusion Relationship Clinical significance of ventilation- perfusion balance apparent in prolonged bedrest Because blood is gravity dependent, it will shift from lung bases to lung area in dependent position while air continues to be drawn toward diaphragm

23. Figure 10-9: Positioning and ventilation-to-perfusion relationship. (A) Upright position—Air moves towards diaphragm and blood gravitates to bases. Best V/Q match (B) Side lying position—Air moves towards diaphragm while blood gravitates to lateral dependent lung fields. (C) Supine postion—Air moves towards diaphragm while blood gravitates to posterior dependent lung fields. (D) Prone position—Air moves towards diaphragm while blood gravitates to the anterior dependent lung fields.

24. Ventilation/Perfusion mismatching Can occur due to not enough BLOOD or not enough AIR If V is greater than Q ratio >1 If Q is greater than V, ratio <1

25. Shunting - Blood flows through pulmonary cap system without undergoing gas exchange Anatomic Capillary “Shuntlike” effect Percentage of cardiac output that flows from right heart and back into left heart without undergoing pulmonary gas exchange Pulmonary shunting is major cause of hypoxemia in high-acuity patients

26. Anatomic Shunt Not all blood that flows through lungs participates in gas exchange Blood that moves from right heart back into left heart without contact with alveoli; Normal AS is approximately 2-5% of blood flow

27. Anatomic Shunt Normal anatomic shunting occurs as result of emptying bronchial and other veins into lung's own venous system Abnormal anatomic shunting can occur because of heart or lung problems ◦ Congenital heart problems ◦ Lung abnormalities

28. Capillary Shunt Normal flow of blood past completely unventilated alveoli Blood flowing by affected units will not take part in diffusion Results from consolidation or collapse of alveoli, atelectasis, or fluid in alveoli

29. Absolute shunt ◦ Combo of capillary shunt and anatomic shunt ◦ lung tissue affected by absolute shunt unaffected by oxygen therapy ◦ shunting of > 15% of cardiac output can result in severe respiratory failure ◦ patients with acute respiratory distress syndrome (ARDS) ◦ hallmark of ARDS is refractory hypoxemia

30. Shuntlike Effect Not a “true shunt”, because the shunting is not complete Exists when there is an excess of perfusion in relation to alveolar ventilation Common causes: ◦ Bronchospasm, excess secretions, hypoventilation Hypoxemia secondary to shuntlike effect is very responsive to oxygen therapy

31. Figure 10-10 Types of physiologic shunt. (a) Anatomic shunt; (b) Capillary shunt; (c) Shuntlike effects— Alveoli with decreased ventilation may respond well to oxygen therapy.

32. Estimating Intrapulmonary Shunt

33. PaO2/FiO2 ratio ph = 7.3 PaO2 70 PCO2 55 SIMV, Rate 14 TV 750 FiO2 40% ph = 7.22 PaO2 102 PCO2 34 SIMV, Rate 8 TV 650 FiO2 50% MWafer

34. Ischemia-Hypoxemia-Hypoxia Ischemia - decreased blood flow to tissues Hypoxemia - reduced transfer of oxygen from alveolar air to blood;,measured by Pa02 – normal 80-100mmHg  MILD 60-70 mmHg  MODERATE 45-59 mmHg  SEVERE <45 mm Hg Hypoxia - decreased ability to obtain or use oxygen

35. Hypoxia vs. Hypoxemia Can’t “see” hypoxemia - so MUST consider relationship of SaO2 to PaO2 S/S of hypoxia: pallor dyspnea, tachypnea use of accessory muscles Tachycardic, dysrhythmias, CP, hypotension w/ bradycardia anxiety, restlessness, confusion Late signs: cyanosis, diaphoresis, resp arrest

36. Respiratory Assessment ABGS Nursing History- REVIEW Physical Assessment - REVIEW Pulmonary Function Tests Other tools for resp assessment

37. Arterial Blood Gas Interpretation A single ABG measurement represents only a single point in time ABGs most valuable when trends are evaluated over time Interpretation of ABGs includes determination of acid-base state, level of compensation, and oxygenation status

38. ABGs ABGs PH = 7.35 - 7.45 CO2 = 35 - 45 HCO3 = 24-28 Acidosis PH < 7.35 (R) CO2 > 45 (M) HCO3< 22 Resp = CO2 disturbances Metabolic = HCO3 disturbances Alkalosis PH > 7.45 (R) CO2< 35 (M) HCO3> 26 1. Acidosis or Alkalosis?2. Respiratory or Metabolic? 3. Compensated disturbances Adapted fromMWafer PaO2 80-100mmHG SaO2 Greater than 95% Hgb 13.5-18g/dL(males) 12-15 g/dL (females)

39. ABG Interpretation 1. Evaluate pH Consider all values > 7.4 to be alkaline & all values < 7.4 to be acidic 2. Evaluate PaCO2 Consider PaCO2 45 mmHg to be acidic 3. Evaluate HCO3 If HCO3 26 mEq/L, consider it alkaline 4. Determine Acid-Base Status Ask: Which individual component matches the pH acid-base state? The MATCH will determine the PRIMARY acid-base disturbance: respiratory vs. metabolic

40. ABGs Example: pH: 7.58 (alkalotic) PaCO2: 38 (normal) HCO3: 30 (alkaline) pH matches HCO3, so we have metabolic alkalosis

41. ABG Interpretation 5. Next step is to determine compensation. Look at : pH, Pa CO2 & HCO3 pH indicates degree of compensation Normal pH - indicates normal value or full compensation Abnormal pH indicates an uncompensated or partially compensated acid-base state.

42. Determine Compensation Uncompensated (Acute) - abnormal pH plus one abnormal value plus a normal value: Example: ph - 7.20, PaCO2 - 65mmHg, HCO3 - 24 mEq/L INTERPRETATION: pH & PaCO2 match (acid). HCO3 is normal. NO COMPENSATION is occurring = state of uncompensated (acute) respiratory acidosis exists.

43. Determine Compensation Partially compensated - abnormal pH plus two abnormal values (PaCO2 & HCO3 are moving in opposite directions). Body has initiated neutralizing imbalance but not there yet. Example: pH - 7.25, PaCO2 60mmHg, HCO3 - 32 mEq/L INTERPRETATION: pH and PaCO2 match (acid). HCO3 is alkaline or moving in opposite direction from PaCO2. pH still abnormal = state of PARTIALLY COMPENSATED respiratory acidosis exists.

44. Determine Compensation Compensated - normal pH plus two abnormal values (PaCO2 & HCO3 are moving in opposite directions). Example: pH - 7.39, PaCO2 - 50mmHg, HCO3 - 31mEq/L INTERPRETATION - pH & PaCO2 match (acid). HCO3 is alkaline (opposite of PaCO2). pH is normal = State of COMPENSATED respiratory acidosis exists. You will not be responsible for interpreting mixed acid-base disorders

45. Causes of Acid – Base Disturbances Resp. Acidosis CNS Disorders, Drug overdose, pneumonia, pulmonary edema, restrictive lung diseases Metabolic Acidosis Renal failure, DKA, drug overdose (ASA, methanol), diarrhea Resp. Alkalosis Hyperventilation, anxiety, fear, fever, asthma, ARDS, CHF, PE, CNS disorders Met. Alkalosis Too many antacids, vomiting, NGT suctioning, low potassium, steroids, diuretics

46. Lactic Acidosis Acid metabolites like lactic acid result from cellular breakdown and anaerobic metabolism Normal range for serum lactate is 0.5-2.0 mEq/L High-acuity patients are at risk for developing elevated levels of lactate During shock, cellular hypoxia drives serum lactate up rapidly

47. The pH-to-HCO 3 Relationship If a metabolic disturbance is present, the pH and HCO 3 should maintain a stable relationship

48. The pH-to-PaCO 2 Relationship pH decreases as PaCO 2 increases pH increases as PaCO 2 decreases

49. The PaCO 2 -to-HCO 3 Relationship Under normal conditions, the PaCO 2 and HCO 3 maintain a stable relationship

50. Nursing History Assess ABC Social History Social History Nutritional History Nutritional History Cardiopulmonary History Cardiopulmonary History Sleep-Rest History Sleep-Rest History Dyspnea /PND Dyspnea /PND Cough Cough

51. Vital Signs and Hemodynamic Values Give crucial baseline data Include arterial blood pressure, pulse rate and rhythm, respiration rate and rhythm, and temperature Obtain pulse oximeter reading If pulmonary artery catheter in place, assess

52. Focused Respiratory Physical Assessment Cyanosis is a late sign of respiratory distress, not a reliable indicator of hypoxia Inspect shape of chest, and observe movement Chest percussion can help detect presence of air, fluid, or consolidation

53. Breath Sounds TypeLocation Associated Problems Characteristics Crackles Peripheral airways, alveoli Atelectasis, excess fluid, mucous, inflammation Discontinuous popping sounds, usually inspiratory Rhonchi Large Airways Inflammation Excess fluid, mucous Continuous coarse, usually expiratory Wheeze Large &/or small airways Bronchoconstriction (always narrowing) from bronchospasm, fluid, mucous, inflammatory byproducts, obstructive lesion Continuous musical sound usually expiratory, doesn’t clear with cough Pleural Friction Rub Pleural surfaces Inflamed surfaces Grating sound w/cont & discontinuous qualities PThomas

54. Pulmonary Function Tests (PFTs) Ventilation is measured using pulmonary function tests Differentiate a restrictive pulmonary problem from an obstructive one PFTs are useful for monitoring effectiveness of therapeutic interventions Diagnostic PFT is usually conducted in a pulmonary laboratory A spirometer can be used at bedside

55. Work of Breathing How does one assess the WOB? Dependent on COMPLIANCE & RESISTANCE PFT disease of ventilation measure of respiratory muscle strength useful in weaning

56. Total lung capacity Volume of gas present in the lungs after maximal inspiration ~ Normal 6000ml in adults composed of four separate volumes : ◦ Inspiratory Reserve Volume (IRV) – amount of air inhaled above normal inhalation ~ 3100ml ◦ Tidal Volume (TV) – amount if air in and out with normal inspiration (details next slide) ◦ Expiratory Reserve Volume (ERV) – amount of air exhaled after normal expiration ~1200ml ◦ Residual volume (RV) – amount of air remaining after maximal expiration (dead air space) ~1200ml

57. Pulmonary Function Tests Tidal Volume ◦ 7-9ml/kg ◦ 500ml avg adult Vital Capacity ◦ 4800 ml ◦ Maximum amount of air exhaled after maximal inspiration Measure WOB

58. Pulmonary Function Tests Minute Ventilation (VE = VT X f) ◦ 5 – 10 L/min ◦ 500ml x 18 = 9000ml or 9L Forced Expiratory Volume- FEVs – Peak Flow

59. Figure 9–17: Pulmonary function tests. The relationship of lung volumes and capacities.Volumes (mL) shown are for an average adult male.

60. Pulse Oximetry Noninvasive technique Uses light wavelengths Detects pulsatile flow Uses a sensor Fingers are most commonly used for placement

61. Causes of Inaccurate Readings Many factors can alter the accuracy of pulse oximetry in high-acuity patients Technical problems Physiologic factors

62. Capnography Monitor C02 levels PETCO Usefulness for patients on PCA pump Use during ACLS

63. Capnography Nasal cannula capnography Endotracheal Tube Capnography

64. Invasive Blood Gas Monitoring Arterial catheter is an invasive means to monitor hemodynamic status and pulmonary gas exchange status Arterial catheters are most commonly inserted into a radial artery May be inserted into a femoral or other artery Major advantage is that frequent samples can be obtained without causing additional trauma and pain to the patient

65. References Carlson, K. (2009). Advanced Critical Care Nursing. St. Louis, MO: Saunders, Elsevier. Chulay, M. & Burns, S. (2006). AACN Essentials of Critical Care Nursing. New York, New York: McGraw-Hill. Wagner, K., Johnson, K., Hardin-Pierce, M. (2014). High Acuity in Nursing, (6 th ed.) Upper Saddle River, NJ: Pearson.