Chapter 4 Diagnosis and Management of Acute Respiratory Failure

Question 1

What are the 3 Types of Respiratory Failure (With Expected labs)

Answer 1

Hypoxemic-
room air Pao2 of ≤ 60 mm Hg
or abnormal Pao2:Fio2 ratio

Hypercapnic-
Paco2 ≥ 50 mm Hg not caused by respiratory compensation for metabolic alkalosis, usually with a pH < 7.35

Mixed-
features of both hypercapnia and hypoxemia

Question 2

What is a normal A-a gradient, and how is is calculated

Answer 2

Alveolar-arterial gradient
5-10 in health adults

PAo2 = Fio2 × (PATM – PH2o) – (Paco2/R)
PAo2= Fio2 x (760-47) - (PaCO2 /0.8)

Question 3

What is a normal P:F ratiov (Pao2:Fio2)

Answer 3

300-500

Question 4

Clinical Criteria for ARDS (Acute Respiratory Distress Syndrome)

Answer 4

1. Onset within 7 days after a known clinical insult or new or worsening symptoms
2. Bilateral diffuse alveolar opacities on chest imaging (chest radiograph or CT scan)
3. P:F ratio < 300*
   Mild : 201 to 300
   Moderate: 101 to 200
   Severe: < 100

Question 5

What is the Oxygenation Index (OI)

What value indicates severe hypoxemia

Answer 5

OI is a measurement of oxygenation dysfunction that takes into account mean airway pressure while a patient is on mechanical ventilation.

OI = [100 × (mean airway pressure (cm H2O) × Fio2]/Pao2

OI of ≥ 25 can indicate severe hypoxemia

Question 6

What are the 4 Mechanisms of Hypoxemia (and examples)

Answer 6

1. Ventilation/Perfusion (V/Q) Mismatch- Pnemumonia, COPD (hypoxic pulmonary vasoconstriction)
2. Hypoventilation- Opioid Overdose, TBI
3. Diffusion Impairment- Fibrosis, Pulmonary Edema
4. Reduced inspired oxygen(Pio2)- High altitudes

Question 7

A Pulmonary Embolism generally results in what type of respiratory failure

Answer 7

Hypercapnic

Increased Dead space results in High PaCO2 and Low ETCO2

Question 8

What are some non-respiratory causes of hypercapnia

Answer 8

hypermetabolic states (burns, hyperthyroidism, prolonged fever)

Question 9

What is paradoxical breathing

Answer 9

Belly Breathing

Diaphragm collapses during inspiration and abdominal wall moves in

Question 10

FIO2 ranges for
1. Nasal Cannula
2. Simple Mask
3. No-Rebreather Mask

Answer 10

1. 24%-45%
2. 25%- 60%
3. 60%-90%

Question 11

Contraindications to Noninvasive positive pressure ventilation (NIPPV)

Answer 11

Altered mentals status
Active vomiting
Hypotension
severe acidosis
Recent facial or esophageal / gastric surgery

Question 12

When should you consider escalating to intibation from NIPPV

Answer 12

No improvement within 4-6 hours

Question 13

What is IPAP and EPAP in relation to NIPPV and how much of a difference should be mainatined between the two

Answer 13

IPAP- Ispiratory positive airway pressure

EPAP- Epiratory positive airway Pressure

IPAP should generally be at least 4cmH2O higher than EPAP

Question 14

Physiology of PEEP in treatment of CHF

Answer 14

Increased intrathoracic pressure decreases preload, reducing lung edema

Question 15

Mechanism of albuterol in respiratory distress

Answer 15

Beta 2 Agonist (respiratory sommth muscle relaxation)

Question 16

Mechanism of Ipratropium bromide in respiratory distress

Answer 16

Anticholinergic- competes with acetylcholine resulting in smooth muscle relaxation and decreased secretion

Question 17

What tidal volume is recommended initially when using NIPPV

Answer 17

6-8mL/Kg

Question 18

What is the maximum inspiratory pressure with NPPV and why

Answer 18

20 cm H2O because gastric distension can occur

Question 19

What is “Cycling” in regards to mechanical ventilation

What parameters can cause a ventilator to cycle

Answer 19

changeover from the end of inspiration to the expiratory phase

elapsed time, delivered volume, or a decrease in flow rate

Question 20

What parameters are used to determine the amount of volume delivered by a ventilator during inspiration

Answer 20

specific volume, pressure, and/or flow.

Question 21

What is “Triggering” in regards to mechanical ventilation

What usually triggers a breath

Answer 21

changeover from expiration to inspiration

PAtient triggered assisted breath or elapsed time (unassisted)

Question 22

What is a Volume-Cycled Breath

Answer 22

Volume assist-control

Preset tidal volume is delivered

Question 23

What is a Time-Cycled Breath

Answer 23

(Pressure Assist-Control)

Aplies a constant pressure over a set amount of time, resulting in variable tidal volumes

Question 24

What is a Flow-Cycled Breath

Answer 24

Pressure Support

Patient regulates rate and tidal volume while ventilator provides presssure support

Question 26

Explain **Assist-Control Ventilation** and which types of ventilator breaths does it utilize

Answer 26

Volume Cycled (Volume Assist Control)- Set Volume and Minimum rate, however patient can still trigger breaths Time Cycled (Pressure Assist-Control)- Set Pressure and time of inspiration. Variable tidal volume based on lung compliance / I:E ratio

Question 27

Describe **Pressure Support Ventilation** and what type of breath it utilizes

Answer 27

preset level of inspiratory pressure assist with each ventilator-detected patient effort Flow Cycled (assist decelerates when flow of patients breath falls below 25% of initial

Question 28

how is Pressure Support Ventilation titrated

Answer 28

A VT of 6 to 8 mL/kg, depending on patient needs A slowing of spontaneous breathing rate to an acceptable range (< 30 breaths/min) The desired minute ventilation

Question 29

Describe **Synchronized Intermittent Mandatory Ventilation (SIMV)**

Answer 29

delivers volume-cycled or time-cycled breaths at a preset mandatory rate Breaths may be triggered by the patient or by the time elapsed

Question 30

What is **Controlled Manual Ventilation (CMV)**

Answer 30

delivers unassisted ventilator breaths at a preset rate Only used in paralyzed patients

Question 31

What is the recommended Tidal volume for bentilated patients

Answer 31

6-8ml/Kg of ideal body weight

Question 32

What is a normal**Minute Ventilation** for ventilated patients and how is it calculated

Answer 32

5-8L/min (Vt x respiratory rate)

Question 33

How do you estimate** Predicted (Ideal) body weight**

Answer 33

Males: 50 + 2.3 (height in inches – 60) 50 + 0.91 (height in cm – 152.4) Females: 45.5 + 2.3 (height in inches – 60) 45.5 + 0.91 (height in cm – 152.4)

Question 34

What tidal volume is used in patients with poor lung compliance (ARDS)

Answer 34

4 to 6 mL/kg by PBW

Question 35

What is Auto-PEEP

Answer 35

When exhalation time is too short leading to retained volume and increreased PEEP beyond vent settings when subsequent breath is delivered

Question 36

What is the goal FIO2 within the first 24 hours

Answer 36

≤ 0.5 (50% oxygen)

Question 37

What adjuncts can be used toreduce risk of Ventilator acquired pneumonia

Answer 37

elevation of the head of the bed to ≥ 30°, oral hygiene, and daily evaluations weaning

Question 38

Goals of mechanical ventilation in ARDS

Answer 38

PaO2: 55-80 mm Hg (7.3-10.7 kPa) Pplat: ≤30 cm H2O VT: 4-6 mL/kg PBW pH: >7.15 is acceptable

Question 39

What can cause an acute rise in peak airway pressures

Answer 39

Mucus Plugging ET Tube obstruction Rapid change in lung compliance

Question 40

What are the criteria for extubation

Answer 40

The main cause of the respiratory failure that lead to the intubation and mechanical ventilation has improved significantly or resolved. Adequate mental status to maintain an airway (including the ability to clear secretions) Adequate oxygen saturation > 90%, Po2 > 60 mm Hg with Fio2 40–50% PEEP around 5–8 cm H2O pH > 7.25

Question 41

What should be performed prior to extubation

Answer 41

Spontaneous Breathing Trial (SBT)

Question 42

**Hypotension after initiating mechanical ventilation** should raise concern for...

Answer 42

Tension Pneumo