Respiratory Failure

Respiratory Failure 

Respiratory Failure is a general term used to describe them inability of the respiratory system to maintain an adequate amount of

1. Oxygen (O2) exchange between the alveoli and the pulmonary capillaries, or

2. Carbon dioxide (CO2) removal out of the lungs, or
3. a combination of both.

The arterial blood gas (ABG) criteria

According to this criteria the respiratory failure in the normal individuals are an arterial partial pressure of oxygen (PaO2) less than 60 mm Hg, or an arterial partial pressure of carbon dioxide (PaCO2) greater than 50 mm Hg, or a mixture of both.

Due to some respiratory disorders can cause one or more abnormal anatomic alterations of the lung—which, in turn, activate specific, and very predictable, pathophysiologic mechanisms and clinical manifestations—which can progressively worsen if not identified and treated.

There are six major anatomic alterations of the lungs—

(1) Atelectasis-
Atelectasis is the collapse of a lung tissues affecting part, segment, lobe of the lung, or an entire lung – is fairly common and most often spontaneously corrects itself for full recovery it is prevents normal oxygen absorption to healthy tissues. The collapse may result from obstruction, structural damage to lung tissue, fibrosis that destroys bronchial segments (e.g. mucus plugging, upper abdominal surgery, pneumothorax, or flail chest).

(2) Alveolar Consolidation

Alveolar or lung consolidation is a medical condition in which solidification of lung tissues or alveoli and describes as the filling of lungs with liquid and solid material. It may affects entire segment, lobes or lungs (e.g. Pneumonia, Tuberculosis).

(3) Increased Alveolar capillary Membrane Thickness-

Increase the alveolar capillary membrane thickness it may affect the diffusion capacity, perfusion and ventilation between the alveoli and the pulmonary capillary (e.g. acute respiratory distress syndrome (ARDS), pneumoconiosis, or pulmonary edema).

(4) Bronchospasm-

Bronchospasm is a condition of the respiratory airway in which sudden contraction of the smooth muscle of the bronchus or bronchi it produces narrowing of the airway diameter. Due to reduce airway diameter start difficulty in respiration because of inadequate amount of ventilation may produce dyspnea. The airway muscles is very sensitive to external or internal stimuli (e.g. asthma).

(5) Excessive Bronchial Secretions-

The irritation or stimulation can changes the pathology of goblet cells and mucous glands are present in the airway start secretions of mucus, plasma fluid, and proteins, including fibrinogen, in excess amount. It may affect the diameter of airway and changes the ventilation (e.g. chronic bronchitis).

(6) Distal Airway and Alveolar Weakening

The chronic airway disease (COPD) affects alveoli and may produce weakening of alveolar wall and distal airway distraction. Due to distraction of alveolar wall reduced the surface area for diffusion of respiratory gases and also affect the ventilation (e.g., emphysema).

In severe cases, any one of these six abnormal alterations of the lungs can leads to a clinical scenario that ends in respiratory failure (see clinical

Scenarios

Respiratory failure is commonly classified as either:-

•  Hypoxemic (Type I) Respiratory Failure,
•  Hypercapnic (Type II) Respiratory Failure or
•  A Combination of Both

I)  Hypoxemic (type I) respiratory failure- Oxygenation Failure

 The term Hypoxemic (type I) respiratory failure is used when the primary problem is an inadequate oxygenation exchange between the alveoli and the pulmonary capillary system—which results decreased PaO2.

II) Hypercapnic (type II) respiratory failure -ventilatory failure-

The term hypercapnic (type II) respiratory failure used when the primary problem is alveolar hypoventilation—which results in an increased PaCO2 and, without supplemental oxygen, a decreased PaO2.

Further it is classify in two other types-

    A) Acute Ventilatory Failure (High PaCO2 and Low pH)-

In this type High PaCO2 and low pH produce acidemia this condition is known as acute ventilatory failure or acute respiratory acidosis. Baseline ABG pH: decreased 7.17, PaCO2: increased 79 mm Hg, HCO3 − increased (but normal) 28 mEq/L, PaO2: decreased 49 mm Hg.

)  B) Chronic Ventilatory Failure (High Paco2 and Normal pH) –

It is defined as High PaCO2 but pH is in normal range termed as chronic ventilatory failure (compensated respiratory acidosis). Baseline ABG pH: normal 7.37, PaCO2: increased 77 mm Hg, HCO3 −: increased (significantly) 43 mEq/L, PaO2: decreased 61 mm Hg.

Chronic ventilatory failure again divided in two types-

      Acute alveolar hyperventilation superimposed on chronic ventilatory failure-

 To maintain the baseline PaO2, PaCO2 often decreases from their normally high baseline level and pH increases. Because increase their alveolar ventilation significantly, the patient’s baseline ABG values can quickly change from chronic ventilatory failure to acute alveolar hyperventilation superimposed on chronic ventilatory failure.

Acute ventilatory failure (Hypoventilation) superimposed on chronic ventilatory failure-

When the patient with chronic ventilatory failure does not have the mechanical reserve to meet the hypoxemic challenge of a respiratory disorder, the patient begins to breathe less. This action causes the PaCO2 to increase above the patient’s already high PaCO2 baseline level. As the PaCO2 suddenly increases, the patient’s arterial pH level falls, or becomes acidic and chronic ventilatory failure change in acute ventilatory failure superimposed on chronic ventilatory failure.

 III)   Combination of both Type I and II

Hypoxemic Respiratory Failure (Type I) (Oxygenation Failure)

• Hypoxemic respiratory failure (type I) is used to describe a patient whose primary problem is inadequate oxygenation.

•  Patients with hypoxemic respiratory failure typically demonstrate hypoxemia—a low PaO2—and a normal, or low PaCO2 value.

•   The low PaCO2 is usually attributable to the alveolar hyperventilation associated with hypoxemia.

Respiratory Disorders Associated With Hypoxemic Respiratory Failure (Oxygenation Failure)-

Restrictive Pulmonary Disorders

• Pneumonia

• Lung abscess

• Pulmonary edema

• Interstitial lung diseases

• Acute respiratory distress syndrome

• Alveolar atelectasis

Chronic Obstructive Pulmonary Disorders

• Emphysema

• Chronic bronchitis

• Asthma

• Cystic fibrosis

Neoplastic Disease

• Cancer of the lung

Newborn and Early Childhood Respiratory Disorders

• Meconium aspiration syndrome

• Transient tachypnea of the newborn

• Respiratory distress syndrome

• Pulmonary air leak syndromes

• Respiratory syncytial virus infection

• Congenital diaphragmatic hernia

• Bronchopulmonary dysplasia§

• Croup syndrome†

Other

• Near drowning

• Smoke inhalation and thermal injuries
Causes of hypoxemic respiratory failure-
Alveolar Hypoventilation

2.      Pulmonary  Shunting

3.      Ventilation- Perfusion Mismatch

4.      Decrease in Inspired Oxygen (decreased FIO2 or PiO2)

Hypercapnic Respiratory Failure (Type II) (Ventilatory Failure)-

• Hypercapnic respiratory failure (type II) term is used when the primary problem is alveolar hypoventilation.

• Patients with hypercapnic respiratory failure demonstrate an increased PaCO2 and, without supplemental oxygen, a decreased PaO2.

Respiratory Disorders Associated With Hypercapnic Respiratory Failure (Ventilatory Failure)

Pulmonary Disorders

• Emphysema

• Chronic bronchitis

• Asthma

• Cystic fibrosis

 Respiratory Center Depression

• Drug overdose

• Cerebral trauma or infarction

• Bulbar poliomyelitis

• Encephalitis

Neuromuscular Disorders

• Myasthenia gravis

• Guillain-Barré syndrome

• Spinal cord trauma

• Muscular dystrophy

Pleural and Chest Wall Disorders

• Flail chest

• Pneumothorax

• Pleural effusion

• Kyphoscoliosis

• Obesity

 Sleep Apnea

The major pathophysiologic mechanisms that result in hypercapnic respiratory failure are

(1) alveolar hypoventilation,

(2) increased dead-space in disease, and

(3) V/Q ratio mismatch.

The four standard criteria to start the mechanical ventilation are-

•      Apnea is defined as the complete absence of spontaneous ventilation—

Apnea causes the PaO2 to rapidly decrease and the PaCO2 to increase (Hypercapnic respiratory failure) which is an absolute indication for invasive mechanical ventilation

•      Acute ventilatory failure is defined as a sudden increase in PaCO2 to greater than 50 mm Hg with an accompanying low pH value (<7.30) (Hypercapnic respiratory failure).

•       Impending ventilatory failure occurs when the patient demonstrates a significant increase in the work of breathing, but with only a borderline acceptable arterial blood gas (Hypercapnic respiratory failure).

•      Severe refractory hypoxemia is a critically low oxygenation status that does not respond well to oxygen therapy (Hypoxemic respiratory failure).

Clinical Indicators for Hypoxemic Respiratory Failure (Oxygenation Failure)

Clinical Indicator	Normal Value	Critical Value
PaO2 (mm Hg)	80 to 100	<60 on FIO2 >0.50
P(A-a)O2 on 100%	25-65	>350
PaO2/PAO2 ratio	0.75-0.95	<0.15
PaO2/FIO2 ratio	350-450	<200
Q_ S /Q_ T (%)	<5	>20

Clinical indicators for ventilatory failure-

Clinical Indicator	Normal Value	Critical Value
Alveolar Ventilation           PaCO2 (acute change)                     pH	35-45 mm Hg 7.35-7.45	>50 mm Hg and Rising <7.2
Lung Expansion • Tidal volume (VT) • Respiratory rate (breaths/min)	5-8 mL/kg 12-20/min	<3 to 5 mL/kg >30/min, or <10/min
Muscle Strength • Maximum inspiratory pressure (MIP, cm H2O) • Vital capacity (VC)	−80 to 100 cm H2O 65-75 mL/kg	<−20 cm H2O <10 to 15 mL/kg
Work of Breathing • Minute ventilation (_VE)  VD/VT (%)	5-6 L/min 25-40%	>10 L/min >60%

Mechanical Ventilator protocols for respiratory failure-

Commonly three types of ventilator are used-

Prophylactic Ventilation 

Non Invasive Ventilation

Invasive Ventilation

Physiotherapy management

In patient phase

Short Term Goals

•      Educate the patients and family.

•      Mobilize mucociliary transport and secretion accumulation.

•      Improve gas exchange.

•      Improve expansion of lungs.

•      Reduce V/Q mismatch.

•      Minimize the work of breathing.

•      Minimize the need for mechanical ventilation

Long term goals

•      Maintain or improve lung compliance.

•      Maintain or restore thoracic mobility and strength, endurance and coordination of respiratory muscles.  

•      Avoid recurrent Respiratory infections.

•      Maximally involve the patient in self care activity & Healthy life style.

•      To improve and maintain aerobic capacity

Therapeutic   Interventions On Mechanical Ventilated Patients

•      Therapeutic positioning.

•      Chest physiotherapy techniques.

•      Manual hyperinflation.

•      Suctioning.

•      Respiratory proprioceptive neuromuscular facilitation techniques

•      Limb elevation and apply crepe bandage.

•      Passive movement of bilateral lower extremity.

Therapeutic Interventions For Off Ventilated Patients

•        Oxygen therapy 
•        Therapeutic positioning/Frequent turning.
•        Chest physiotherap. 
•             Suctioning.

After extubation

     •      Active cycle of breathing techniques

     •      Huffing/coughing techniques.

     •      Incentive spirometry.

     •      Early mobilization.

       Out patient phase