Acute Hypoxic Respiratory Failure occurs when the body unable to maintain normal partial pressure O2 and Co2 in bloodstream.
Acute Hypoxic Respiratory Failure is an emergency condition. Oxygen and carbon dioxide exchange is the main cause of this respiratory failure. Inadequate oxygen in the bloodstream causes metabolism disturbances.
Respiratory failure is a condition that is caused by inadequate gas exchanges. This condition make symptoms like hypoxic (inadequate oxygen in bloodstream), hypercapnea (high carbondioxyde concentration in artery), and acidosis.
Ventilator is equipment for help all ventilation process. This equipment can maintain oxygen and carbon dioxide still in homeostatic.
Acute Hypoxic Respiratory Failure Classifications
Acute Hypoxic Respiratory Failure classification is based on affected organs. So there are two classification of Acute Hypoxic Respiratory Failure.
Respiratory failure can be caused by high PaO2 and low PaCo2 pressure. These conditions cause gas diffusion problem or edema. Lung edema occurs when the heart fail to do its function, and high intravascular exchanges (between vascular into interstitial and alveolar).
There are cardiovascular problems that lead myocardium dysfunction and increasing LVEDV and LVEDP lead to backward-forward mechanism. Lung capillary hydrostatic pressure will increase and fluid will leak into interstitial space and alveolar. Those mechanisms are a mechanism of lung edema.
- These are diseases cause myocardium dysfunction: myocardium infarction, cardiomyopathy, and myocarditis.
- And the disease cause high LVEDV and LVEDP:
- Overload pressure: stenosis aorta, hypertension, Courtois Aorta
- High volume: insufficiency mitral, insufficiency aortic, ASD, and VSD.
- Ventricle filling resistances: mitral stenosis and insufficiency tricuspid
Non-cardiac means causes of Acute Hypoxic Respiratory Failure from respiratory problems. It is especially problems in upper and lower respiration tract, and diffusion process. Acute Hypoxic Respiratory Failure can be arisen because of some conditions like obstruction, emphysema, atelectasis, pneumothorax, ARDS, etc.
There are 2 types of Respiratory Failure; those are Acute Hypoxic Respiratory Failure and Chronic Hypoxic Respiratory Failure.
Acute Hypoxic Respiratory Failure
It is a disease where the patient is still had normal lung structure and function before the onset of the disease.
Chronic Hypoxic Respiratory Failure
It is a disease where the patient has chronic lung disease like chronic bronchitis, emphysema, and black lung disease.
Hypoxic Respiratory Failure Causes
- Head trauma: contusion cerebra
- Brain Inflammation: encephalitis
- Vascular: bleeding in brain
- Medication causes: anesthesia
- Neuromuscular defect: GBS, tetanus, cervical trauma, muscle relaxant
- Airway defects: obstruction and asthma
- Lung defects: lung edema, atelectasis, ARDS.
- Thorax defects: costae fracture, Pneumothorax, hematothorax
- Heart defects: left heart failure
Acute Hypoxic Respiratory Failure in children depends on many factors:
Children’s chest wall is still soft with rips insertion, hips looked horizontal and intercostal muscle development are still in development process. All of these conditions make chest limited movement.
Airway in children is wider than older people. But if there is obstruction or inflammation, let’s say it just 1 mm, in children; it will shrink the children’s airway about 75%.
Elastic tissue in alveolar septum called elastic recoil. It has function in maintaining alveolar position. In children, alveolar is relative bigger and easy to collapse.
Children is easy to get infection like pneumonia. This infection risk is higher in children and it can develop Acute Hypoxic Respiratory Failure in children.
Congenital defect can affect all of respiratory system. It is not only respiratory system, but also cardiovascular and other organ systems.
Physiology and Metabolic Factors
Oxygen need and airway resistance in children is bigger than common people like us. If there is an infection, metabolism will increase. This condition will make the body need more oxygen. This oxygen need condition should be got by more breath effort, but it causes more calorie and water consumption, and it needs more respiration muscle use. In children, glycogen level is low and it causes organic acid accumulation from anaerobe metabolism. This acidosis will lead to acidosis.
Pathophysiology of Acute Hypoxic Respiratory Failure
First of all, patient with acute hypoxic respiratory failure experience hypoxic and hypercapnia tolerance which become worse time by time. After acute hypoxic respiratory failure, the lung back to its normal function.
But it is different with chronic hypoxic respiratory failure; patient’s lung structure is in irreversible damage.
The indicator of respiratory failure can be assessed in breathing frequency. Normally breathing frequency is about 16-20 times per minutes. If the breathing is more than 20 times per minute, the patient will need ventilator because “breathing effort” is high and lead to fatigue. Normal vital capacity of lung is about 10-20 ml/kg.
The most common cause of respiratory failure is inadequate ventilation. It can be caused by upper airway obstruction. Breathing center which control the breathing pattern is in pons and medulla.
Anesthesia, head injury, stroke, brain tumor, encephalitis, meningitis, hypoxic and hypercapnia suppress the respiration center. Breathing pattern will be slow and shallow.
At post-operative period with general anesthesia lead to inadequate breathing because anesthetic agent suppresses the breathing pattern.
Pneumonia or lung disease leads to Acute Hypoxic Respiratory Failure.
Spontaneous inhalation happens because diaphragm and intercostalis muscle contraction, chest cavity expand and negative pressure arise so that air flow come into lung. Otherwise, in expiration or exhalation phase that work passively.
In mechanical ventilation, ventilator blows air into patient’s lung so that the pressure during inspiration is positive pressure. This positive pressure causes increasing intra-thorax pressure.
There are 2 basic mechanism that make acute hypoxic respiratory failure as follows:
If a child has infection in his or her airway, then secretion of tracheobronchial is much produced, inflammation and airway obstruction, high blood supply is needed in respiratory system, and high metabolism rate.
Because of mucus edema, thick secretion and smooth muscle spasm will make airway lumen shrink. This condition cause air trapped in distal area of lung.
Diffusion and CO2 retention arise hypoxic and hypercapnia, both includes shallow respiration and acidosis.
Hypoxic and hypercapnia will cause disturbed alveolar ventilation, then depressed respiration. If it stays still, fatigue and acidosis will appear. Hypoxic and hypercapnia will cause vasoconstriction of pulmonary artery that will make alveolar retention. The heart will work harder and lead to heart failure.
Because of high blood supply in lung, hypoxic condition will cause capillary permeability, CO2 retention, high metabolic rate, and lung edema. Finally, lung edema will lead to ventilation and oxygenation failure (acute hypoxic respiratory failure).
Sign and Symptoms of Acute Hypoxic Respiratory Failure
- General Symptoms: fatigue and sweaty (diaphoresis)
- Respiration : wheezing breathing sound or even no breathing sound, nose retraction in children, tachypnea, bradypnea, apnea, and cyanosis.
- Cardiovascular: Bradycardia or tachycardia, hypo tension or hypertension, Pulses Paradoxes 21 mmHg, and cardiac arrest.
- Cerebral: Irritability, headache, mental disturbances, low consciousness, seizure, and coma.
Diagnosis of Acute Hypoxic Respiratory Failure
Early diagnosis for respiratory failure is difficult to know clinically. Laboratory test is the most important to diagnose respiratory failure such as Blood Gas Analysis (BGA) to know oxygenation status, ventilation and acid-base balances, oxygen saturation and blood pH.
In BGA diagnosis, the most common result are hypoxic, hypercapnia, and acidosis respiratory or metabolic.
Here is the detail:
- Hemoglobin is under 12 gr %
- pH is under 7,35 or over 7,45
- paO2 is under 80 or over 100 mmHg
- pCO2 is under 35 or over 45 mmHg
- BE is under -2 or over +2
- Oxygen saturation less than 90%
- Rontgen: There is fluid or air accumulation image and movement of mediastinum.
Acute Hypoxic Respiratory Failure Treatment
It is a temporary treatment while looking for the main cause of respiratory failure.
Medicines and Other Treatments
Mucolytic is useful to remove excessive secretion accumulation in respiratory systems.
Postural drainage is the best treatment for excessive secretion in respiratory system. This procedure is like removing the secretion in many body positions.
Chest physiotherapy are clapping and vibrating the chest or back of the body. Clapping and vibrating will detach thick secretion in respiratory airway. Chest physiotherapy usually combines with postural drainage for better result.
Trachea may consist of excessive secretion, so the nasothraceal suction will remove the secretion out of the trachea so that the airway clearance easy to do without using much energy.
Cough / Deep Breathing Exercise
Maintaining respiratory function by exercising cough and deep breathing is the best procedure to do. The lung must expand freely without using much energy to cough and breath.