Identifing the Need for Mechanical Ventilation

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Ch. 4 Pilbeam's Mechanical Ventilation
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What are some physiological Objectives for Mechanical Ventilation

1. Support/manipulate pulm. gas exchange.

Alveolar Ventilation- achieve ventilation/allow permissive hypercapnia

2. Increase lung vol.- prevent/treat atelectasis w/ PEEP; restore/maintain adequate FRC

3. Increase WOB


When is permissive hypercapnia allowed?

Required in the ventilation of pts w/ life threatening Asthma, Acute lung injury (ALI), or ARDS to protect the lung by avoiding high ventilating volumes/pressure.


Clinical Objectives of Mechanical Ventilation

1. Reverse Acute Respiratory failure

2. Reverse Respiratory distress

3. Reverse Hypoxemia

4. Prevent/Revers atelectasis and maintain FRC

5. Reverse Respiratory muscle fatigue

6. Permit sedation/paralysis (or both)

7. Minimize assoc. complications/reduce mortality


Initial Assessment of Patient

1. Determine LOC

2. Assess appearance/texture of skin

3. Evaluate pt's vitals


Physical signs of Respiratory Distress

anxiety, eyes wide open, forehead furrowed, nostrils flared, diaphoretic/flushed, tripodding, may appear ashen/pale/cyanotic, accessory muscle use


What is Acute Respiratory Failure (ARF)?

Resp. activity is absent or insufficient to maintain adequate O2 uptake/CO2 clearance, in spite of therapy.


What does ARF look like clinically?

Inability to maintain PaO2, PaCO2, and pH.

(PaO2 below normal predicted range for pt's age; PaCO2 >55 mmHg; pH at or <7.25)


What are the two forms of ARF?

Hypoxemic Respiratory Failure and Hypercapnic Respiratory Failure


Acute Hypoxemic Respiratory Failure

acute life-threatening or vital organ-threatening tissue hypoxia


What is the usual cause of Hypoxemic Respiratory failure?

severe V/Q mismatching and Diffusion defects (right-to-left shunting, alveolar hypoventilation, aging, and inadequate inspired O2)


Acute Hypercapnic Respiratory failure

aka Acute ventilator failure. Occurs when a person can't achieve adequate ventilation to maintain a normal PaCO2.


What does the ventilator pump consist of?

respiratory muscles, thoracic cage, and nerves that are controlled by the respiratory centers of the brainstem.


What three types of disorders can lead to pump failure?

1. CNS disorders

2. Neuromuscular disorders (NIF/VC)

3. Disorders that increase WOB


CNS Disorders that Reduce Drive to Breathe (assoc. w/ hypoventilation and possible Resp. failure)

Depressant drugs, Brain/Brainstem lesions, Hypothyroidism, Sleep Apnea syndrome caused by idiopathic central alveolar hypoventilation


CNS Disorders that Increase Drive to Breathe (assoc. w/ hypoventilation and possible Resp. failure)

Increase CO2 production (^ metabolic rate), Metabolic Acidosis, Anxiety associated w/ dyspnea


Neuromuscular Disorders (assoc. w/ hypoventilation and possible Resp. failure)

Paralytic disorders (Myasthenia gravis, Guillain-Barre, tetanus, botulism), Paralytic drugs (succs), Drugs that affect NM transmission, Impaired muscle fxn (peripheral nerve disorders, chronic pulm. disease w/ decreasing capacity for diaphragmatic contraction as a result of air trapping)


Disorders that Increase WOB (assoc. w/ hypoventilation and possible Resp. failure)

Pleura-occupying lesions (PE, pneumo, empyema, hemothorax), Chest Wall deformaties (flail chest, rib fractures), Increased airway resistance resulting from increased secretions, mucosal edema, bronchoconstriction, foreign body), Lung tissue involvement (ARDS, interstitial pulm fibrotic disease), Pulm. Vasc. problems, Increased Metabolic rates w/ pulm. problems, Post-op pulm. complications, Dynamic hyperinflation (air trapping)


Resp. Signs of Hypoxemia

Mild/Moderate: Tachypnea, Dyspnea, Paleness

Severe: Tachypnea, Dyspnea, Cyanosis


Cardiac Signs of Hypoxemia

Mild/Mod: Tachy, Mild HTN, Peripheral vasoconstriction

Severe: Tachy eventually brady/arrhythmias, HTN eventually hypotension


Neurologic signs of Hypoxemia

Mild/Mod: Restlessness, Disorientation, Headaches, Lethargy

Severe: Somnolence, confusion, delirium, blurred vision, tunnel vision, Loss of Coordination, Impaired judgement, Slowed rxn time, manic-depressive activity, LOC, coma


Respiratory Signs of Hypercapnia

Mild/Mod: Tachypnea, Dyspnea

Severe: Tachypnea eventually bradypnea


Cardiovascular signs of Hypercapnia

Mild/Mod: Tachy, HTN, Vasodilation

Severe: Tachy, HTN eventually hypotension


Neuromuscular signs of Hypercapnia

Mild/Mod: Headaches, drowsiness, dizziness, confusion

Severe: Hallucinations, hypomania, convulsions, LOC eventually coma


Signs of Hypercapnia

Sweating, skin redness


Pts w/ Hyperapnic Respiratory Failure

PzCO2 levels are elevated w/ accompanying hypoxemia unless the pt is receiving O2 therapy


What can untreated hypoxemia, hypercapnia, and acidosis lead to?

cardiac dysrhythmias, ventricular fibrillation, and cardiac arrest


What elements are required to achieve a successful outcome to treat hypoxemia, hypercapnia, and acidosis?

1. Use of supplemental O2 therapy

2.maintenance of a patent airway

3. continuous monitoring of oxygenation and ventilatory status w/ pulse ox and ABG analysis


58 y/o male is admitted to the ED from his home after a suspected CVA. VS reveal a HR OF 94bpm, RR 16 bpm, normal temp, and BP 165/95 mmHg. The pt's pupils respond slowly and unequally to light. Breath sounds are diminished in the lung bases. A sound similar to snoring is heard on inspiration. The pt is unconscious and unresponsive to painful stimuli. What is the most appropriate course of action?

The pt should be intubated to protect patent airway and immediately evaluated for cerebral reperfusion therapy. The pt is typically admitted to ICU post reperfusion therapy for further eval. Mechanical ventilation may be necessary if the pt remains unconscious and unresponsive. In cases where the pt is not receiving mechanical ventilation, aerosol therapy delivered through a T-adapter is required to prevent drying of secretions.


A stat ABG eval performed on a pt admitted through the ED reveals the following: pH 7.15, PaCO2 83 mmHg, PaO2 34 mmHg, HCO3 28 mEq/L on RA. The pt was found unconscious in a nearby park. No hx is available. What is the most appropriate course of action at this time?

1. The problem may be drug related, try naloxone (Narcan).

2. Intubate and begin ventilation; assess further w/ VS, SpO2 monitoring, EKG, breath sounds, ABG Values, electrolytes, blood alcohol levels, toxicology screening, and neurologic status eval.


Blood Values: Indications for ARF and the need for Mechanical Ventilation

pH 7.35-7.45; <7.25

PaCO2 35-45 mmHg; >55 and rising

VD/VT ration 0.3-0.4; >0.6

PaO2 80-100 mmHg; <70 on O2 >6L

P(A-a)O2 5-20 mmHG; >450 on O2

PaO2/PAO2 0.75; <0.15

PaO2/FiO2 475; <200


Ideal Body Weight (IBW)

m: 106+(6(H-60))

f: 105+(5(H-60))


Minute Ventilation (VE)


Respiratory rate x tidal volume


Starting point for PEEP on mechanical ventilation



Normal Non-Intubated Tidal Volume

5-7 mL/Kg of IBW


Normal Tidal Volume for a Ventilated Pt

6-8 mL/Kg of IBW


Normal Tidal Volume for COPD

8-10 mL/Kg of IBW

(High lung compliance CL)


Normal Tidal volume for ARDS

4-6 mL/Kg of IBW

(Low lung compliance CL)


Normal BP

Systolic 90-100

Diastolic 60-80


Plateau Pressure

  • Tells us if adjustment of Vt or pressure is needed on vent
  • Taken w/ Inspiratory hold (2-3 sec)
  • Range is <30
  • if >30 lungs can over expand

Pt w/ Low lung compliance

Use more PEEP to avoid atelectasis


Pt w/ high lung compliance

Use higher respiratory rate to help carry O2 to areas of gas exchange

  • O2 has to navigate through more dead space

Dead space

Gas within the tidal volume that doesn't participate in gas exchange

  • 1/3 or 2.2 mL of each breath is normal dead space

Risks of too much Positive Pressure

Can decrease Right Venous blood return to the heart and can impede hemodynamics


Normal Values for Mechanically Ventilated pt

RR 12-20

HR 60-100

Ve 5-10 L/min


Pressures on the vent

Measured in cmH2O


Static Compliance for Mechanically ventilated pt

Normal Cstat is 50-100 mL/cmH2O



Normal -100 to -50 cmH2O

Critical -20 to 0 cmH2O



Maximum Expiratory Pressure

Normal 100 cmH2O

Critical <40 cmH2O



Vital Capacity

Normal 65 to 75 ml/kg

Critical <10 to 15 ml/kg



Tidal Volume

Normal 5-8 ml/kg

Critical <5 ml/kg



Respiratory Frequency

Normal 12-20 breaths/min

Critical >35 bpm



Forced Expired Volume at 1 Second

Normal 50 to 60 ml/kg

Critical <10 ml/kg



Peak Expiratory Flow Rate

Normal 350-600 L/min

Critical 75-100 L/min


CNS disorders that decrease the respiratory drive

Depression of the resp. drive induced by drugs/trauma can lead to reductions in VE and VA (alveolar ventilation) and ultimately to hypercapnia and hypoxemia


Increase PaCO2 greater than 70mmHg

has a CNS depressant effect which reduces the resp. drive and ventilation


CNS disorders assoc. w/ tumors, stroke or head trauma

can alter normal breathing and cause Biot respirations or Cheyne-Stokes respirations if significant bleeding occurs with these types of injuries


Cerebral abnormalities can affect normal swallowing reflexes

ETT may be required to protect airway from aspiration or obstruction of the tongue


Neuromuscular disorders that can lead to resp. failure are usually the result of

  • Motor nerve damage
  • Problems w/ transmission of nerve impulses at the neuromuscular junction
  • muscle dysfunction
  • CNS disorders
  • Drugs that affect nm function

Drug-induces NM failure

  • usually rapid onset
  • intubation and mechanical ventilation are indicated if resp. fatigue occurs rapidly in a pt w/ a nm disorder and ARF is imminent

Respiratory failure in disease states like myasthenia gravis

  • may not occur for days or even years
  • intubation and mechanical ventilation are indicated if resp. fatigue occurs rapidly in a pt w/ a nm disorder and ARF is imminent

Maximum Inspiratory Pressure (MIP) and Vital Capacity (VC)

  • used to assess respiratory muscle strength of pts w/ nm disorders
  • non-invasive; easy to obtain; inexpensive
  • q 2-4h to monitor changes in respiratory status
  • MIP of -20 to -30 cmH2O or less
  • VC lower than 10-15 mL/kg

If pt's condition progressively worsens w/ nm Disorders

  • do not wait until acute situation develops to intervene
  • Generally, invasive positive pressure ventilation should be initiated before acute respiratory acidosis develops

Case 1

A 68 y/o woman w/ hx of myasthenia gravis has been in the hospital for 12 days. She was admitted b/c her primary disease had worsened. The pt is unable to perform MIP and slow VC maneuvers b/c she can't seal her lips around the mouthpiece. Her attempts produced these values: MIP -34 cmH2O; SVC 1.2 L. What should the clinician recommend at this time?

In spite of pt not being able to form a good seal, the measurements are acceptable. Continue to monitor MIP and VC q8h. Request and eval of an anticholinesterase challenge. Keep pt NPO and provide suctioning at bedside until swallowing ability can be evaluated. Monitor SpO2 and ABG if symptoms become worse


Case 2

26 y/o male recovering from mycoplasma pneumonia complains of tingling sensations and weakening in his hands/feet. He is admitted for observation. Over several hours the pt becomes unable to move his legs. What should the RT recommend at this time?

The hx/symptoms suggest Guillian-Barre syndrome. Assessment of the pt should include measurement of MIP, VC and ABG. A reduced MIP <15 cmH2O and VC of <10-15 mL/kg plus the presence of ARF would be consistent w/ respiratory muscle weakness assoc. w/ Guiallian-Barre. Mechanical ventilation is indicated. Consider the advantages/disadvantages of using NIVV, oral vs nasal endotracheal intubation, or a tracheostomy. The RT may also suggest an anticholinesterase challenge to confirm dx.


Increased WOB

  • can lead to resp. failure secondary to resp. muscle fatigue
  • in pts experiencing resp. distress WOB can account for 35-40% of total O2 consumption
  • it is usually assoc w/ and Increased rate/depth of breathing
  • can induce hypoventilation, resp. insufficiency, and eventually resp. failure

Conditions that cause increased WOB

  • flail chest
  • pneumothorax
  • hemothorax
  • can all impair the mechanics of breathing and affect pts ability to breathe

Reduction in Alveolar Ventilation can lead to...

  • V/Q mismatch
  • an increased VD/VT
  • and ultimately hypoxemia, hypercapnia, and acidosis

Increased WOB (in some patients) can eventually result in...

Rapid, shallow breathing and paradoxical breathing

(the abdomen moves out during exhalation and in during inhalation while the chest wall moves out during inhalation and in during exhalation)


Treatment of Flail chest

  • better outcomes are achieved when pts w/ flail chest are managed w/out intubation or invasive positive pressure ventilation
  • IPPV is only used for flail chest when it is assoc. w/ imminent respiratory failure

Asthma Case

13 y/o girl is seen in the ED for an acute exacerbation of asthma. Continuous neb trx w/ a B-2 adrenergic bronchodilator is administered. The pt has been given a high dose of corticosteroid and is receiving O2. Four hrs after admission, she is alert/responsive. Her RR is 20 bpm. Coarse crackles and end-expiratory wheezes are heard through both lung fields. What recommendation for continuous respiratory care should be made?

Pts condition appears to be improving. Continue drug trx, adjusting med dose and frequency as necessary, continue to monitor pt


Normal Adult and Critical Range Values


MIP -100 to -50 cmH2O -20 to 0 cmH2O

MEP 100 cmH2O <40 cmH2O

VC 65-75 mL/kg <10 to 15 mL/kg

VT 5 to 8 mL/kg <5 mL/kg

f 12-20 bpm >35 bpm

FEV1 50 to 60 mL/kg <10 mL/kg

PEF 350 to 600 L/min 75 to 100 L/min


Critical Range Values indicate....

they may indicate the need for mechanical ventilation when considered w/ other assessment criteria


What do the normal range values indicate?

They are a better used as indications to discontinuing mechanical ventilation with the exception of

  • in pts w/ neuromuscular disorders, the MIP and VC may be beneficial in tracking respiratory muscle strength
  • In pts w/ reactive airway disease, the FEV1 and the PEF are helpful for quantifying the degree of airway resistance

MIP and VC

These are bedside measurements most often used to assess respiratory muscle strength in pts w/ neuromuscular disease


PEF (peak expiratory flow)

most often used parameter to assess airway resistance and to measure pt's ability to maintain airway patency

  • used as part of an effective asthma treatment plan for asthma pts
  • measured w/ a peak flow meter
  • acceptable values are 350-600 L/min
  • Low PEFs are seen often in pts having an acute asthma episode (75-100 L/min are the critical ranges)

FEV1 (Forced expiratory volume at 1 min)

another pulmonary function parameter used to assess airway resistance

  • normally 80% of VC (50-60 mL/kg IBW)
  • fev1 <10 mL/kg IBW is considered extremely low
  • measured w/ a spirometer
  • not to be measured if pt is severely SOB and in acute resp. distress

MIP (Maximum inspiratory pressure) or Pimax

the most negative pressure generated during a forceful inspiratory effort against an occluded airway. It can also be called a NIF (negative inspiratory force)

  • measured w/ a pressure manometer
  • connected by means of a mask, mouthpiece, or endotracheal tube adapter
  • MIP is most accurate when it is measured from the residual volume (RV) (after a maximum exhalation)

Vital Capacity (VC)

the volume of air that can be maximally exhaled following a maximum inspiration

  • can provide valuable info about ventilatory function b/c the pt must be able to take in a lg. volume of air to produce a cough strong enough to clear the airway
  • typically 65-75 ml/kg of IBW
  • can be measure at bedside w/ a pneumotachometer or respirometer

Respiratory Rate (f)

  • normally 12-20 bpm
  • critical if >35 bpm; it is a sign of inadequate alveolar ventilation or hypoxemia (or both)
  • increased RR is an indication of increased WOB which eventually leads to respiratory muscle fatigue

Minute Ventilation (VE)

  • product of Vt and RR (VE= RRxVT)
  • Normal is 5-6 L/min and this value is directly related to pts metabolic rate
  • VE >10 L/min is critical
  • if pt demonstrates significant resp. dysfunction, the VE required to maintain a stable PaCO2 may become so high that the pt can't sustain the required WOB

Failure of Ventilation and Increased Dead Space (VD)

  • best indicator of adequate ventilation is PaCO2
  • PaCO2 >50-55mmHg with a pH <7.25 indicates acute hypoventilation or acute hypercapnic respiratory failure
  • increased PaCO2 suggests VD is increased relative to VT
  • Normal VD/VT is 0.3-0.4 at normal VT
  • Critical VD/VT is >0.6 (indicates increase in VD)

Increases in VD (dead space)

  • are associated w/ V/Q mismatching (VD ventilation is defined as ventilation w/out perfusion)
  • Common causes: pulmonary thromboemboli, pulmonary vascular injury, and regional hypoperfusion

Measurement of VD/VT

estimated by using non-invasive volumetric capnometry


Failure of Oxygenation

  • PaO2 is a good indicator of oxygenation status
  • Normal PaO2 is 80-100 mmHg when pt is on room air
  • value varies w/ age and body position
  • PaO2 <70 mmHg on 60% FiO2 indicates refractory hypoxemia or hypoxemic resp/ failure


Formula: PaO2-PAO2

  • used to determine cause of altered oxygenation
  • Normal range for P(A-a)O2 for pts of RA is 5-20 mmHg
  • Normal range for P(A-a)O2 for pts on 100% O2 is 25-65 mmHg
  • when PaO2 is low P(A-a)O2 is high
  • hypoxemia is due to one of the other three general causes: shunt, diffusion defects, V/Q mismatch (PaCO2 lower than normal indicates hypoventilation to compensate for hypoxemia)

Range for P(A-a)O2

  • 4 mmHg for every 10 years of pt age
  • on 100% O2, every 50 mmHg difference in P(A-a)O2 approximates 2% shunting

PaO2/PAO2 ratio

  • another approach that can be used to evaluate pts O2 status
  • Normally 0.75-0.95; <15% is critical
  • range indicates 75%-95% of the O2 available in the alveoli is diffusing into the pulm. capillaries
  • PaO2 in mmHg divided by PAO2 in mmHg

PaO2/FiO2 ratio

  • eliminates the need to calculate the PaO2
  • Normal values calculated as 90 mmHg/0.21= 428
  • Range 350 to 450

PaO2/FiO2 indicating refractory hypoxemia

A PaO2 of 40 mmHg/FiO2 of 1.0=40

  • this is an example of an extremely severe abnormality (refractory hypoxemia)

Hypoxemia caused by low Hb/Hct as a result of hemorrhage

A blood transfusion is required to improve O2 content and transport


Refractory hypoxemia respiratory failure

Can be treated w/ PEEP and CPAP


Treating Hypoxemia that is accompanied by increased WOB or a rising PaCO2 and falling pH

Mechanical ventilation is required


In patients w/ Acute Lung Injury (ALI)

Mask CPAP and O2 are not effective treatments, Intubation is required


Criteria for Institution Mechanical Ventilation

  • Apnea/absence of breathing
  • Acute respiratory failure
  • Impending Ventilatory failure
  • refractory hypoxemic resp. failure w. increased WOB or ineffective breathing pattern

What to consider when trying to reverse underlying disease

Consider pts medical HX, Physical assessment, ABG, lung mechanics measurements, prognosis, and advanced directives


Criteria for mechanical ventilation

  • support pulm system so it can maintain adequate level of alveolar ventilation
  • Reduce WOB until cause of resp failure can be identified/treated
  • Restore arterial/systemic acid-base balance to normal level for pt
  • Increase O2 delivery to and oxygenation of body organs/tissues
  • Prevent complications assoc. w/ mechanical ventilation

Alternatives to Invasive Ventilation

  • High flow NC allows delivery of high gas flows through a narrow tube
  • Placing pt in upright or Fowler position
  • providing appropriate medications to provide some relief of hypoxemia

Indications for Mech. Ventilation in adults w/ ARF

1. Apnea or impending respiratory arrest



Indications for mech. ventilation in adults w/ ARF

2. Acute exacerbation of COPD w/ dyspnea, tachypnea, and acute resp. acidosis plus one of the following

  • Acute CV instability
  • Altered mental status or persistent uncooperativeness
  • Inability to protect lower airway
  • Copious/unusually viscous secretions
  • Abnormalities of the face/upper airway that would prevent NIPPV

Indications for mech. ventilation in adults w/ ARF

3. Acute ventilatory insufficiency in cases of NM disease accompanied by any of the following

  • Acute resp. acidosis (hypercapnia/decreased arterial pH)
  • progressive decline in VC <10-15 ml/kg
  • progressive decline in MIP <-20 to -30 cmH2O

Indications for mech. ventilation in adults w/ ARF

4. Acute hypoxemic resp. failure w/ tachypnea, respiratory distress, and persistent hypoxemia despite admin of high FiO2 w/ HFNC or in presence of any of the following:

  • Acute CV instability
  • Altered mental status/persistent uncooperativeness
  • inability to protect lower airway

Indications for mech. ventilation in adults w/ ARF

5. Need for ETT to maintain/protect airway or to manage secretions, given the following factors:

  • ET <7 mm internal diameter (ID) w/ VE >10L/min
  • ET <8 mm ID w/ VE >15 L/min

Invasive positive pressure ventilation may not be indicated for the following conditions until other therapies have been attempted

  • dyspnea, acute respiratory distress
  • acute exacerbation of COPD
  • Acute severe asthma
  • acute hypoxemic respiratory failure in immunocompromised pt
  • Hypoxemia as an isolated finding
  • traumatic brain injury
  • flail chest

Acute on chronic respiratory failure

  • treatment of choice is NIV (non-invasive positive pressure ventilation)
  • shown to reduce the need for intubation , complications of ventilation, shorten hospital stay, and mortalities

Indications for Noninvasive Positive pressure ventilation (NIV) in adults

At least 2 of the following must be present

  • RR >25 bpm
  • Mod to severe acidosis: pH 7.25-7.30; PaCO2 45-60 mmHg
  • mod to severe dyspnea w/ use of accessory muscles and paradoxical breathing pattern

Absolute Contraindications for NIV

  • Resp. arrest
  • cardiac arrest
  • CV instability (HTN, dysrhythmias, acute MI)
  • non-resp. organ failure (encephalopathy, GI bleeding/surgery, hemodynamic instability w/ or w/out unstable cardiac angina)
  • pt tracheoesphageal fistula
  • inability to protect airway/ high risk of aspiration
  • uncooperative pt
  • facial/head trauma

Relative contraindications for NIV

  • copious or viscous secretions
  • fixed nasopharyngeal abnormalities
  • extreme obesity

Intubation without Ventilation

  • used if no ventilatory support is needed, but airway needs to be protected

Ethical Considerations

  • if no reasonable chance exists that ventilation would extend a persons quality of life
  • if the pt has advanced directives stating no mechanical ventilation
  • determine if pt has legal documentation with their wishes (advanged directives)

Switching from NIV to Invasive Ventilation

  • Respiratory arrest
  • RR >35 bpm
  • Severe dyspnea w/ use of accessory muscles and/or paradoxical breathing
  • Life-threatening hypoxemia: PaO2 <40 mmHg; PaO2/FiO2 <200
  • Severe acidosis: pH <7.25; PaCO2 >60 mmHg
  • Hypersomnolence, impaired mental status
  • CV complications (HTN, shock, heart failure)
  • Failure of NIV
  • Metabolic abnormalities, sepsis, pneumonia, pulmonary embolism, barotrauma, massive pleural effusion

Treatments for Arterial Hypoxemia

  • Hypoventilation-Increase FiO2, Increase alveolar ventilation
  • Low V/Q ratio- Increase FiO2, CPAP
  • Intrapulmonary shunt- Increase FiO2, CPAP
  • Diffusion defect- Increase FiO2, steroids, diuretics
  • Low pB- Descend to lower alt.
  • Low inspired O2 concentration <21%- Increase FiO2

Key Point 4-1

tachycardia and tachypnea are nonspecific, mostly subjective signs that provide only limited help in deciding when to intubate and ventilate a patient


Key Point 4-2

MIP and VC are bedside measurements most often used to assess respiratory muscle strength of patients with neuromuscular disease


Key Point 4-3

No single value for PaO2, PaCO2, or pH indicates a need for invasive ventilation


Key Point 4-4

PaO2 and SpO2 are the key indicators of the severity of acute hypoxemic respiratory failure


Key Point 4-5

Protecting the pt's airway is critical w/ conditions such as stroke, drug OD, cerebral damage, and copious or viscous secretions


Key point 4-7

A simple test for dehydration: gently pinch the skin on the back of the hand, if the skin quickly returns to its normal position then the skin turgor is normal. If the skin remains puckered, skin turgor is decreased and the pt is probably dehydrated.


Which of the following suggest the presence of respiratory insufficiency and the need for ventilatory support?

A 1 and 2 only

B 2 and 4 only

C 1,2, and 4 only

D 1,2,3, and 4

1. MIP of -17 cmH2O

2. VC of 2.1 L in a 70 kg man

3. PaCO2 of 81 mmHg and pH of 7.19

4. PaO2 of 65 mmHg on RA


Blood gas results on room air from an unconscious pt brought into the ER are as follows: pH=7.23, PaCO2=81 mmHg, HCO3= 33 mEq/L, PaO2= 43 mmHg, SaO2= 71%. With no other data, what should be the form of therapy?

A. O2 w. a nonrebreather mask

B. CPAP Mask

C. IPPB treatment w/ Albuterol

D. Mechanical ventilation


A 30 y/o woman is seen in the ER. She demonstrates paralysis of the lower extremeties that is progressively worsening. After several hours, during which she was monitored, her VC has decreased to 12 mL/kg and MIP is -30 cmH2O. The ABG results are not yet available. What type of therapy is most likely needed?

A. Aerosolized bronchodilator in a MDI

B. Mechanical ventilation

C. Incentive spirometry to improve muscle strength

D. Narcotic-blocking agent


A 28 y/o man w/ botulism poisioning is beginning to develop progressive paralysis. The RT has been monitoring the pts MIP and VC q2h. The most recent results show the pt continues to deteriorate. MIP is -27 cmH2O, Vc is 32 ml/kg. Which of the following could be appropriately recommended?

A. Gastric lavage

B. O2 Therapy

C. Medication to reverse paralysis

D. Mechanical ventilation


A 34 y/o man is taken to the ER after a MVC. He is unconscious and unresponsive. ABGs obtained while the pt is receiving O2 via a nonrebreather show: pH=7.09, PaCO2= 93 mmHg, HCO3= 27 mEq/L, PaO2= 47 mmHg. Which of the following would the therapist recommend?

A. Recheck Vitals

B. Intubate and ventilate

C. Change to a venture mask and coach the pt to breathe

D. Begin CPR


A 68 y/o man w/ a hx of COPD and CO2 retention is brought to the ER by ambulance. He is receiving O2 through a NC @ 2L. He is conscious and cooperative but in distress. He is tripodding and using accessory muscles to breathe. His VS show: HR=100 bpm, BP= 128/78 mmHg, Temp= 37.8 C, RR= 20 bpm through pursed lips. Breath sounds reveal bilateral crackles and wheezes. Which of the following is most appropriate?

A. Change to a venture mask and coach pt to breathe

B. Intubate and ventilate

C. Change to a nonrebreather

D. Evaluate for NIV (BIPAP/CPAP)