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• Involuntary breathing


  Controlled by the neurons, located in the medulla and pons
• Lungs expanding when air enters

  • Apneustic
  • Pneumotaxic
  • Carotid bodies
  • Aortic arch chemoreceptors
• Increase in pCO2


  Stimulates peripheral chemoreceptors to initiate respiration
• Generates rhythmic impulses for rhythmic breathing activities


  Medullary inspiratory centers
• Respiration is a reflex process, but it can be controlled voluntarily for a short period
• Respiration is subjected to variation, even under normal physiological conditions. For example, emotion and exercise increase the rate and force of respiration
• The altered pattern of respiration is brought back to normal, within a short time by some regulatory mechanisms in the body
• Regulatory mechanisms


  • Nervous or neural mechanism
  • Chemical mechanism
• Respiratory centers


  • Medullary centers
  • Pontine centers
• Medullary centers


  • Dorsal respiratory group of neurons
  • Ventral respiratory group of neurons
• Pontine centers


  • Apneustic center
  • Pneumotaxic center
• Nerves


  • Afferent nerves
  • Efferent nerves
• Chemoreceptors


  • Central chemoreceptors
  • Peripheral chemoreceptors
• Dorsal Respiratory Group of Neurons (DRG)


  • Diffusely situated in the nucleus of tractus solitarius (NTS)
  • Generate an inspiratory ramp
  • Responsible for the basic rhythm of respiration
  • Serve as the principal initiators of the activity of the phrenic nerves and maintain the activity of the diaphragm
• Inspiratory "Ramp" Signal


  • Begins weakly and increases steadily in a ramp manner for about 2 seconds in normal respiration
  • Ceases abruptly for approximately the next 3 seconds, which turns off the excitation of the diaphragm and allows elastic recoil of the lungs and the chest wall to cause expiration
  • Causes a steady increase in the volume of the lungs during inspiration, rather than inspiratory gasps
  • Rate of increase and span (limit) are controlled
• Ventral Respiratory Group (VRG)


  • Consist of both inspiratory and expiratory neurons
  • Located in the nucleus ambiguous and nucleus retroambiguous
  • Neurons in the nucleus ambiguous are primarily vagal motor neurons that innervate the ipsilateral laryngeal, pharyngeal, and tongue muscles involved in breathing and maintenance of the patency of the upper airway
  • VRG remains inactive during normal inspiration
  • Activated by the DRG to act and assist the dorsal group when greater pulmonary ventilation is needed (e.g. exercise)
  • Supplies expiratory signals to the abdominal muscles during forced heavy expiration
• Apneustic center


  • Situated in the reticular formation of lower pons
  • Functions to increase the depth of inspiration by acting directly on dorsal group neurons
  • Increases tidal volume and duration of inspiration (with occasional expiratory gasps)
  • Its activity is inhibited by the pneumotaxic center and by vagal impulses
• Pneumotaxic Center


  • Located dorsally in the nucleus parabrachialis of the upper pons
  • Inhibits the apneustic center so that the dorsal group neurons are inhibited
  • Primary effect is to control the "switch-off" point of the inspiratory ramp, thus controlling the duration of the filling phase of the lung cycle by limiting inspiration, thus increasing the rate of breathing
• Central chemoreceptors


  • Located in the ventral medulla
  • Respond to local increases in hydrogen ion concentration, pCO2, or both
  • Do not respond to hypoxia
  • About 80–90% of the normal total steady-state response to increased carbon dioxide concentrations comes from the central chemoreceptors
• Peripheral chemoreceptors


  • Located in aortic bodies and carotid bodies, the carotid bodies are much more important in this response than the aortic bodies
  • Carotid bodies are located bilaterally in the bifurcations of the common carotid arteries, their afferent nerve fibers pass through Hering's nerves to the glossopharyngeal nerves and then to the dorsal respiratory area of the medulla
  • Aortic bodies are located along the arch of the aorta; their afferent nerve fibers pass through the vagi, also to the dorsal medullary respiratory area
  • Detect PO2 level and increase ventilation when arterial PO2 is below 70 mm Hg
  • The activity of peripheral chemoreceptors increases usually leading to an increase in ventilation
  • The response to hypoxia is potentiated at higher arterial pCO2
• Juxtacapillary receptors


  • Located adjacent the capillaries in the pulmonary vessel
  • Stimulated by pulmonary congestion, inflammation, overinflation of the lungs, irritants and endogenous substances (histamine, capsacin, bradykinin, serotonin)
  • Role isn't well defined in physiologic situations
  • Responsible for hyperventilation in pulmonary congestion and left heart failure
  • Produce apnea then rapid breathing, bradycardia and hypotension
• Artificial respiration


  Any measure that causes air to flow in and out of a person's lungs when natural breathing is inadequate or ceases, as in drowning, electric shock etc
• Stoppage of oxygen supply for 5 minutes causes irreversible changes in tissues of brain, particularly tissues of cerebral cortex
• Purpose of artificial respiration


  To ventilate the alveoli and to stimulate the respiratory centers
• Indications for artificial respiration


  • Drowning
  • Strangulation
  • Suffocation
  • Gas and smoke inhalation
  • Carbon monoxide poisoning
  • Electric shock
  • Anaesthesia
  • Respiratory paralysis (e.g. drugs, myasthenia gravis, poliomyelitis)
• Manual artificial respiration methods


  • Mouth-to-mouth method
  • Prone pressure method (Schafer)
  • Arm life chest pressure method (Silvester)
  • Arm lift back pressure method (Holger-Nielsen)
  • Tilting or Eve's rocking method
• Mouth-to-mouth respiratory method


  Also known as rescue breath method/expired air method/intermittent positive pressure breathing method/direct method
• Mouth-to-mouth respiratory method


  • There are several variations to this method - Mouth-to-nose, Mouth-to-nose-and-mouth, Mouth-to-mask (reduces infection), AMBU (artificial manual breathing unit) bag or bag-mask-valve, CPR mask
  • Only manual technique able to produce adequate ventilation
  • Expired air contains 16% CO2, it helps to stimulate the respiratory centers
  • Simple, effective and useful for all age groups
• Prone pressure method (Schafer)


  The subject is laid on their stomach, the rescuer presses on the back to force out air from the lungs and draws fresh air in by releasing the pressure
• Arm lift chest pressure method (Silvester)


  The subject is laid on their back, the rescuer presses their arms over the subject's chest to force out air from the lungs and draws fresh air inside by pulling their arms above the head
• Arm lift back pressure method (Holger-Nielsen)


  The subject is laid on their back, the rescuer lifts the subject's arms above their head to draw fresh air in and presses down on their back to force air out
• Tilting or Eve's Rocking method


  The subject is laid on their side, the rescuer rocks the subject's body to force air in and out of the lungs
• Instrumental or mechanical artificial respiration methods


  • Drinker's method
  • Bragg Paul's method
  • Mechanical Ventilator
• Drinker's method


  Uses an iron lung chamber or tank respirator machine
• Bragg Paul's method

  Uses a resuscitator or ventilator
• Types of mechanical ventilation


  • Positive-pressure ventilation: pushes air into the lungs (invasive with tube, or noninvasive like CPAP, BiPAP, APAP)
  • Negative-pressure ventilation: sucks air into the lungs by expanding and contracting the chest (e.g. iron lung, chest cuirass)
  • Volume ventilators: pump a constant volume of air into the lungs intermittently with minimum pressure
• Mechanical ventilation devices


  • Chest Cuirass
• Mechanical ventilation may be invasive with a tube in the airway, or noninvasive that can be used at home
• Most of the CO2 transported in the blood is in HCO3−
• The amount of hemoglobin in the blood has the greatest effect on the ability of blood to transport oxygen