Question Answer
Hypoxemia responsive to an increase in FIO2 is likely caused by what? Low V/Q ratio
Hypoxemia Unresponsive to an increase in FIO2 is likely caused by what? Diffusion defect or shunt
What two things determine the arterial PCO2? Alveolar ventilation & carbon dioxide production
When the WOB is relieved, how does McVent affect alveolar ventilation and CO2 production? alveolar ventilation increases & CO2 production decreases
McVent w/ positive pressure does what to dead space and V/Q ratio? increases dead space decreases V/Q ratio
In disorders that affect time constants, what can be manipulated to improve oxygenation and alveolar emptying? Inspiratory OR expiratory time
The mode of ventilation chosen for a patient should be matched to the patient’s lung traits to achieve what (3) goals? optimize patient-ventilator synchrony / improve acid-base status / improve oxygenation
What (4) dangers do we protect against when choosing a mode of ventilation for a patient? alveolar damage / oxygen toxicity / muscle atrophy / fatigue
What (6) physiologic benefits come from PPV? alveolar expansion / improved oxygenation / improved ventilation / decreased WOB / decreased cardiac work / improved O2 delivery
If not carefully managed, PPV can cause what (3) negative effects? hyperventilation / tissue damage / barotrauma
When PPV increases the intrapleural & mean airway pressures, what else can happen? It can decrease venous return and cardiac output
What effect does PPV have on renal, hepatic, & gastrointestinal functions, and why? PPV causes malfunction of those areas due to decreased perfusion of those capillary beds
Name (3) effective strategies to decrease ICP in traumatic brain injury. elevate the head / osmotic diuretics / CSF drainage
Hypoxemia caused by hypoventilation responds to increased FIO2, BUT how is alveolar ventilation restored? McVent increases alveolar ventilation, which in turn increases PaO2
According to the alveolar air equation, what does increasing the FIO2 do? it increases PAO2
What (2) factors influence a change in PaCO2? a change in alveolar ventilation and metabolic rate
In a shunt, because the alveoli are flooded or collapsed – what happens to surface area and PAO2? they are decreased
With ALI, the permeability of the capillary endothelium to fluid is increased. What results from this? fluid filling of the interstitial and alveolar spaces and an increase in the AC membrane thickness
O2 content is directly related to arterial oxygenation and Hgb concentration as shown in the CaO2 equation.Explain what 1.34 & .003 are 1.34 is a constant & represents the amt of O2 carried by ea fully sat. gm of Hgb .003 is a constant that represents the amt of O2 carried in the plasma PaO2
With the administration of Peep/CPAP in treating a shunt, what result can you expect? an increase in alveolar surface area for diffusion / improved V/Q matching / improved arterial oxygenation
Why should PEEP/CPAP be used cautiously? pressures too high can cause alveolar overdistension, which will redistribute pulmonary blood flow, resulting in an increased shunt
Tissue oxygen delivery (DO2)is defined by what (2) factors? CaO2 x C.O.
Name (4) goals of PEEP. improve arterial oxygenation / improve tissue oxygen delivery / increase PAO2 / decrease FIO2


Egan’s Chapter 43 Practice Questions:


1. The airways are represented by: transairway pressure Pta, and is the difference between the Pawo-Palv

2. ARDS higher rate: Asthma has a lower bpm rate

3. As alveolar ventilation decreases: PaCO2 increases

4. The chest wall is represented: trans-chest wall pressure Ptcw=Ppl-Pbs

5. Decreased ventilation/perfusion ratio is possible with certain diseases.

6. If the chest wall and lungs are lumped together they can be represented by: transthoracic pressure Ptt=Palv-Pbs

7. The lungs are represented by the: transalveolar pressure Pl=Plv,-Ppl

8. Mechanical ventilation tidal volume in acute respiratory failure is: 4-8 ml/kg

9. Minute ventilation: tidal volume times rate

10. Negative pressure mechanical ventilation: similar to spontaneous breathing, decreases pleural pressure during inspiration b/c the chest is exposed to subatmospheric pressure, at rest negative intrapleural pressure, zero alveolar and zero pressure of the respiratory system, mid-inspiration alveolar and pleural pressure become negative and negative pressure of the respiratory system, end-inspiration pleural space negative and alveolar is zero negative pressure of the respiratory system, beginning exhalation plural space is negative ans alveolar is positive zero pressure of the respiratory system, end-exhalation pleural space is negative and alveolar space returns to zero and zero pressure of the respiratory system

11. Negative pressure mechanical ventilation may impede on: venous return causing tank shock. Also may cause sleep apnea in pt with COPD or neuromuscular dysfunctions

12. Normal lungs or COPD: 6-8 ml/kg

13. Normal spontaneous tidal volume is: 5-8 ml/kg

14. Positive pressure mechanical ventilation: caused by an increase in airway pressure. Also causes an increase in Ptp, at rest negative intrapleural pressure alveolar is zero, inspiration alveolar and pleural pressure become postive, end-inspiration pleural space alveolar are positive, beginning exhalation plural space and alveolar is positive, end-exhalation pleural space is negative and alveolar space returns to zero

15. Pressure at the airway opening Pawo, is known as: mouth pressure

16. Patient with ARDS tidal volume range: 4-8 ml/kg

17. Respiratory rate in normal pt is 12-20bpm: 12-20bpm

18. Spontaneous ventilation: end exhalation is slightly negative, alveolar, mouth and body surface pressures are zero, at inspiration diaphragm contracts because of stimulus, causing negative intrapleural pressure, mid-inspiration alveolar and plural pressure become negative , end-inspiration pleural space negative and alveolar is zero, beginning exhalation plural space is negative ans alveolar is positive, end-exhalation pleural space is negative and alveolar space returns to zero.

19. Transalveolar pressure should be as low as possible during mechanical ventilation: Palv less than 28-30cmH2O minimize vent induced lung injury. Pplat less then 28-30cmH2O-thne Palv cannot exceed the danger level.

20. Transdiaphragmatic pressure affects gas movement: the difference between intra-abdominal pressure and pleural pressure and the effects on the diaphragmatic movement Ppl-Pab

21. Transrespiratory pressure Ptr: the difference between the airway opening pressure and the body surface pressure.

22. What is needed for gas to flow through the airway: pressure gradient

23. What is Ppl, pressure in the pleural space: the virtual space between the visceral and parietal pleurae, this is usually a negative pressure

24. What is the primary indication for mechanical ventilation: hypercapnic respiratory failure aka: ventilatory failure

25. Aerophagia: Swallowing of air

26. Autoregulation: Automatic control of a mechanical or physiologic system; necessitates both a sensing mechanism (to measure what is regulated) and a feedback loop (to respond to changes)

27. Barotrauma: Physical injury sustained as result of exposure to ambient pressures above normal, most commonly secondary to positive pressure ventilation (e.g. pneumothorax, pneumomediastinum)

28. Biotrauma: Inflammation of the lungs in response to inappropriate mechanical ventilation that promotes alveolar overdistention in inspiration and derecruitment on exhalation

29. Mean Airway Pressure: Average pressure applied to the airway

30. Transairway Pressure: Difference between airway pressure and alveolar pressure

31. Transalveolar Pressure: Diffference between alveolar pressure and pleural pressure

32. Trans-Chest Wall Pressure: Difference between the pleural space and the body surface. Also called Transthoracic Pressure.

33. Transdiaphragmatic Pressure: The pressure change across the diaphragm associated with breathing

34. Transpulmonary Pressure: Of or pertaining to the difference in parameter (e.g. pressure) between alveoli and pleural space

35. Transrespiratory Pressure: Across the respiratory system; of or pertaining to the difference in a parameter (e.g. pressure) between the alveoli and the body surface

36. Transthoracic Pressure: Difference between the pleural space and the body surface. Also called Trans-Chest Wall Pressure.

37. Valutrauma: Alveolar overdistention and damage caused by ventilation with high peak inflation pressures.