Respiratory Failure

RESPIRATORY FAILURE

Q. 1

Which of the following is a false statement about Type I respiratory failure:

 A

Decreased Pa02

 B

Decreased PaC02

 C

Normal PaC02

 D

Normal A-a gradient

Q. 1

Which of the following is a false statement about Type I respiratory failure:

 A

Decreased Pa02

 B

Decreased PaC02

 C

Normal PaC02

 D

Normal A-a gradient

Ans. D

Explanation:

A-a Gradient is the difference between the Alveolar PO2 (A) and arterial PO2 (a). The a-a gradient indicates how well O2 is equilibrating across the blood air barrier. 

 
Acute respiratory failure is defined as a lung disorder, wherein adequate functioning of lung, to meet the necessary demands of an individual is not met. It is unable to maintain normal levels of arterial gas in the blood. Respiratory failure is of 3 types, namely
 
Type 1 respiratory failure or Oxygenation Failure
Type 2 respiratory failure or Ventilation Failure
Type 3 respiratory failure or Combined Respiratory Failure
 
Ref: NMS Medicine By Susan. D. Wolfsthal, Page 63 ; High-Yield Physiology, Part 845, Volume 2008, By Ronald W. Dudek, Page 59 ; Clinical Llaboratory Medicine By Kenneth D. McClatchey, 2202, Page 375

Q. 2

CO2 retention is seen in:

 A

Carbon monoxide poisoning

 B

Respiratory failure

 C

High altitude

 D

All

Q. 2

CO2 retention is seen in:

 A

Carbon monoxide poisoning

 B

Respiratory failure

 C

High altitude

 D

All

Ans. B

Explanation:

B i.e. Respiratory failure

Type II respiratory failure, which occurs d/t hypoventilation (i.e. failure of ventilation) is characterized by hypoxemia with hypercapnia (CO2) retention but normal (not increased) alveolar-arterial oxygen gradient IP                                            1

Aa02,

Hypercapnia (hypercarbia or CO2 retention) is defined as an elevation in arterial partial pressure of carbon dioxide (Pco2). It characteristically occurs secondary to inadequate alveolar ventilation (hypoventilation), in type II respiratory failure.   –

–              Type II respiratory failure (or alveolar hypoventilation = alveolar ventilatory failure = hypercapnia = hypercarbia = CO2 retention = respiratory acidosis) or normal PA-a02 is seen in reduced compliance of chest like kyphoscoliosisQ, reduced lung compliance like pulmonary (alveolar) edetnaQ, obstructive lung disease like COPDQ, weakness of respiratory muscle (like bulbar poliomyelitisQ), bronchospasm and decreased central respiratory drive. Drowning may cause bronchospasm & pulmonary edema & so CO2 retention.

–   Type I respiratory failure results from failure in exchange (diffusion) of respiratory gases at the alveolar-capillary junction as a result of disease of lung parenchyma (like pneumonia), or vasculature (like right to left shunt), and ventilation-perfusion mismatchQ. It is characterized by increased alveolar-arterial oxygen gradient (PA-ao2)Q, hypoxemia and normal or low PaCO2.

–  At high altitudes alveolar CO2 decreases b/o hyperventilation.

Respiratory failure is defined as a disorder wherein lung function is inadequate to meet the metabolic demands of the individual and is unable to maintain normal arterial cas level in the blood.

Type

Characteristic Features

Causes

RF-I

Represents failure of oxygenation,

and is characterized by dysponea

and secondary hyperventilation l/t

Results from failure in exchange of respiratory gases (mainly 02)at the alveolar capillary

junction (i.e. alveolar capillary block syndrome) as a result of disease of lung parenchyma.

There is thickening of alveolar or capillary wall resulting in ventilation -perfusion (V-Q)

 

– Hypoxemia (Pao2 – decreased; <

mismatch. Only 02 transfers is affected because CO2 is 20 times more diffusible. So causes

 

60 mm Hg)

are

 

–  Increased alveolar – arterial

I.  Parenchymal (interstitial) lung diseases

 

Oxygen gradients’ (PA-ao2 > 15

mm Hg)

– which thicken alveolar – capillary membrane eg. asbestosis, sarcoidosis,

pneumoconiosis, berylliosis, diffuse interstitial fibrosis, infiltrative lung disease like

 

–  Normal or decreased Paco2 ( 40

malignancy & granulomatosis.

 

mmHg) i.e. respiratory alkalosis

– Which separate A-C membrane like pulmonary (interstial) edema (in cardiac failure)

and exudates (pneumonitis or pneumonia)(2 and (resultant) pulmonary fibrosis.

 

 

II. Mixing of venous blood with arterial blood like right to left shuntQ.

 

 

III. Ventilation – Perfusion mismatch Q: In emphysema surface area for diffusion decreases

 

 

(i.e. poorly ventilated alveoli increase).

 

 

Mn: “RAPE-VIP” = “Right to left shunt, Alveolar (pulmonary) edema, parenchymal disease

 

 

(pneumonia), emphysema – ventilation perfusion mismatch”.

RF II

Represents failure (defect) in

I.  Decreased central respiratory drive to breathe

 

ventilation and is characterized by

– Drug like morphine, sedative & anesthetics overdose.

 

hypoventilation lit

– Brain stem injury, bulbar poliomyelitisQ, hypothyroidism, sleep disordered breathing.

 

– Hypoxemia (Pao2 decreased; < 60

II. Respiratory muscle weakness

 

mmHg)

– Normal alveolar-arterial oxygen

– Neuromuscular disorders like myasthenia gravis, GB syndrome, bulbar poliomyelitis,

ALS.

 

gradient (PA-ao2 < 15 mmHg)

– Myopathy, polymyositis, electrolyte derangement.

 

– Hypercapnia (Paco2 > 40 mm Hg)

III.Obstructive lung disease

 

i.e. respiratory acidosis Q.

– Acute obstruction like foreign body, laryngeal edema, bronchospasm, asthma

 

 

– COPD (esp during acute exacerbation) like chronic bronchitis, emphysema, interstial

lung disease.

 

 

IV.Increased load on respiratory system d/t

 

 

– Resistive load eg bronchospasm

 

 

– Reduced chest wall compliance eg. pleural effusion, pneumo/fibro – thorax,

abdominal distension (ascitis), rib cage disorder (kyphoscoliosis)Q, ankylosing

spondylitis, flail chest.

 

 

– Reduced lung compliance eg. atelectasis, lung resection, alveolar edema (ARDS)Q,

PEEP (positive end expiratory pressure).

 

 

– Increased minute ventilation requirements eg pulmonary embolism with increased

dead space, sepsis.

RF III

Also called peri-operative

respiratory failure

Occurs as a result of atelectasis and atelectasis is common in perioperative period

RF IV

Result of hypoperfusion of

respiratory muscles

Occurs in patient with shock


Q. 3

Most common cause of death in case of acute poliomyelitis is –

 A

Intercostal muscles paralysis

 B

Convulsion

 C

Cardiac arrest

 D

Respiratory failure

Q. 3

Most common cause of death in case of acute poliomyelitis is –

 A

Intercostal muscles paralysis

 B

Convulsion

 C

Cardiac arrest

 D

Respiratory failure

Ans. D

Explanation:

Ans. is ‘d i.e., Respiratory failure 

Death is usually due to complications arising from respiratory dysfunction.

        Paralytic polio

o In less than I% of infections.

o Paralysis is characterized as :

I. Descending                    4. Non progressive                     6. No autonomic disturbance

2. Asymmetrical                5. No sensory involvement         7. Lower motor neuron type

3. Proximal muscles > distal muscles

o Most common muscle affected —> Quadriceps

o Most common muscle undergoes complete paralysis Tibialis anterior

o Most common muscle affected in hand —> Opponens pollicis.

o M.C. cause of death -4 Respiratory paralysis

Following signs can be elicited :

1. Tripod sign                                 —>       Child is asked to sit up unassisted. He assumes tripod posture.

2. Kiss the knee Test                     —>          The child cannot kiss his knees due to spine stiffness.

3. Head drop sign                       —>           Hand is placed under the patients shoulder and the trunk is raised. The head lags behind simply.


Q. 4

False statement about type I respiratory failure is:

 A

Decreased PaO2

 B

Decreased PaCO2

 C

Normal PaCO2

 D

Normal A-a gradient

Q. 4

False statement about type I respiratory failure is:

 A

Decreased PaO2

 B

Decreased PaCO2

 C

Normal PaCO2

 D

Normal A-a gradient

Ans. D

Explanation:

Answer is D (Normal A-a gradient)

Type I Respiratory failure is characterized by an increase in alveolar arterial 02 gradient.

Respiratory failure is defined as a disorder wherein, lung function is inadequate to meet the metabolic demands of the individual and is unable to maintain normal arterial gas levels in the blood.

It is of two types:

Type I Respiratory failure

Type II Respiratory failure

 

Represents failure of oxygenation and is characterized by a

low Pa02 with normal or low PaCO2.

Represents a defect in ventilation (hypoventilation) and is

characterized by decreased PaO, with increase PaCO2.

Pa02

: Low (< 60 mm Hg)

Pa02

: Decreased (< 60 mm Hg)

PaCO2

: Normal or low

49 mm Hg)

PaCO2

: Increased (> 49 mm Hg)

PA-a0′

: Increased

 

PA-a02

: Normal

Causes :

 

 

Causes :

 

 

This type is caused by conditions which affect oxygenation, like:

  • Parenchymal diseases (V-Q mismatch)
  • Diseases of vasculature/shunts

Examples:

– Pneumonia Q

– ARDS Q

– Emphysema Q

–  Right to left shunts Q

 

This type is caused by conditions causing hypoventilation as in:

  • Obstructive lung disease: COPD, F. body
  • Decreased central respiratory drive e.g. CNS disorders like : Brain injury, Meningitis
  • Weakness of respiratory muscle e.g.

–   Peripheral N.S. disorders like: M. gravis.

–   Interstitial lung disease. Q

–   MS disorders like polymyositis.

– Rib cage disorders : Kyphoscoliosis


Q. 5

In type – II respiratory failure, there is :

 A

Low pO2 and low pCO2

 B

Low pO2 and high pCO2

 C

Normal pO2 and high pCO2

 D

Low pO2 and normal pCO2

Q. 5

In type – II respiratory failure, there is :

 A

Low pO2 and low pCO2

 B

Low pO2 and high pCO2

 C

Normal pO2 and high pCO2

 D

Low pO2 and normal pCO2

Ans. B

Explanation:

Answer is B (Low PO2 and high PCO2):

Type II respiratory failure (or pump failure) is characterized by decreased Pa02 and increased PaCO2 as a result of alveolar hypoventilation. There is a fall in minute ventilation which causes a rise in PaCO2 and fall in Pa02. The alveolar arterial gradient (PaO2 is normal).

Type I Respiratory failure
Hypoxemia with decreased PaCO2

Type II Respiratory failure
Hypoxemia with increased PaCO2


Q. 6

Which is NOT a type I respiratory failure:

March 2013 (e)

 A

ARDS

 B

COPD

 C

Pulmonary edema

 D

Pneumonia

Q. 6

Which is NOT a type I respiratory failure:

March 2013 (e)

 A

ARDS

 B

COPD

 C

Pulmonary edema

 D

Pneumonia

Ans. B

Explanation:

Ans. B i.e. COPD

Respiratory failure

Type I:

–  Parenchymal disease,

–  ARDS,

–  Pneumoniae,

Emphysema

Type II:

– COPD,

– Flail chest etc.

Type III:

–  Atelectasis


Q. 7

Type-II respiratory failure is associated with:

September 2009

 A

Flail chest

 B

Pulmonary edema

 C

Interstitial lung disease

 D

ARDS

Q. 7

Type-II respiratory failure is associated with:

September 2009

 A

Flail chest

 B

Pulmonary edema

 C

Interstitial lung disease

 D

ARDS

Ans. A

Explanation:

Ans: A: Flail chest

Hypercapnic respiratory failure (type II) is characterized by a PaCO2 of more than 50 mm Hg. Hypoxemia is common in patients with hypercapnic respiratory failure who are breathing room air. The pH depends on the level of bicarbonate, which, in turn, is dependent on the duration of hypercapnia.

Type I (Oxygenation) respiratory failure:

–        Adult respiratory distress syndrome (ARDS)

–        Asthma

–        Pulmonary oedema

–        Chronic obstructive pulmonary disease (COPD)

–        Interstitial fibrosis
Pneumonia

–        Pneumothorax

–        Pulmonary embolism

–        Pulmonary hypertension

Type II Respiratory Failure:

  • Disorders affecting central ventilatory drive

–        Brain stem infarction or haemorrhage

–        Brain stem compression from supratentorial mass

–        Drug overdose, Narcotics, Benzodiazepines, Anaesthetic agents etc.

  • Disorders affecting signal transmission to the respiratory muscles

–        Myasthenia Gravis

–        Amyotrophic lateral sclerosis

–        Gullain-Barre syndrome

–        Spinal -Cord injury Multiple sclerosis

–        Residual paralysis (Muscle relaxants)

  • Disorders of respiratory muscles or chest-wall

–        Muscular dystrophy

–        Polymyositis

–        Flail Chest

Type Ill respiratory Failure:

–        Occurs as a result of lung atelectasis

Type IV respiratory Failure:

It occurs due to hypoperfusion of respiratory muscle in a patient with shock.


Q. 8

Example of type-I respiratory failure is: 

March 2010

 A

Cardiogenic shock

 B

Atelectasis

 C

Myasthenia gravis

 D

ARDS

Q. 8

Example of type-I respiratory failure is: 

March 2010

 A

Cardiogenic shock

 B

Atelectasis

 C

Myasthenia gravis

 D

ARDS

Ans. D

Explanation:

Ans. D: ARDS


Q. 9

Characteristic of type-II respiratory failure is:

September 2010

 A

Low PaO2 and low PaCO2

 B

Low PaO2 and normal PaCO2

 C

Normal PaO2 and high PaCO2

 D

Low PaO2 and high PaCO2

Q. 9

Characteristic of type-II respiratory failure is:

September 2010

 A

Low PaO2 and low PaCO2

 B

Low PaO2 and normal PaCO2

 C

Normal PaO2 and high PaCO2

 D

Low PaO2 and high PaCO2

Ans. D

Explanation:

Ans. D: Low PaO2 and high PaCO2

Type II Respiratory Failure (Ventilatory Failure: Arterial Hypercapnia): Partial pressure of CO2 in the arterial blood reflects the efficiency of ventilatory mechanism that clears (washes out) CO2 produced during tissue metabolism. Type II failure can be caused by any disorder that decreases central respiratory drive, interferes with the transmission of signals from the central nervous system, or impedes the ability of respiratory muscles to expand the lungs and chest wall.

Type II failure is characterized by an abnormal increase in the partial pressure of CO2 in the arterial blood (PaCO2 > 46 mm Hg), and is accompanied by simultaneous fall in PAO2 and Pa02, therefore PAO2 – Pa02 difference remains unchanged.


Q. 10

Most common cause of hypercapnic respiratory failure:

March 2011,’Parch 2013 (a, b, h)

 A

Acute asthma

 B

Aspergillosis

 C

COPD

 D

Pneumothorax

Q. 10

Most common cause of hypercapnic respiratory failure:

March 2011,’Parch 2013 (a, b, h)

 A

Acute asthma

 B

Aspergillosis

 C

COPD

 D

Pneumothorax

Ans. C

Explanation:

Ans. C: COPD

Causes of type II (hypercapnic) respiratory failure:

Chronic causes: COPD, sleep apnea, kyphscoliosis, myopathies/ muscular dystrophies, ankylosing spondylitis;

Acute causes: Acute severe asthma (NOT acute asthma), acute exacerbation of COPD, upper airway obstruction, narcotic drugs etc.

Type II respiratory failure:

  • Reduced PaO2
  • Increased PaCO2
  • Normal P(A-a)O2
  • Hypoxemia with increased PaCO2

Type I respiratory failure:

  • Reduced PaO2
  • Normal/ decreased PaCO2
  • INcreased P(A-a)O2
  • Hypoxemia with decreased PaCO2

Q. 11

Type 3 respiratory failure occurs due to ‑

 A

Post-operative atelectasis

 B

Kyphoscoliosis

 C

Flail chest

 D

Pulmonary fibrosis

Q. 11

Type 3 respiratory failure occurs due to ‑

 A

Post-operative atelectasis

 B

Kyphoscoliosis

 C

Flail chest

 D

Pulmonary fibrosis

Ans. A

Explanation:

Ans. is ‘a’ i.e., Post-operative atelectasis



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