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  • Also called inspiration.
  • Diaphragm contracts and moves downward.
  • Intercostal muscles contract and the ribcage expands.
  • Negative pressure in the chest cavity causes air to rush into the lungs.


  • Also called expiration.
  • Diaphragm relaxes and moves up.
  • Intercostal muscles relax and the ribcage moves inwards.
  • Decreasing size of the chest cavity forces air out.

Control of respiration

  • Hypercarbic drive: normal respiratory control responds to CO2 levels in the arterial blood. You feel an urge to breath when CO2 level is high.
  • Hypoxic drive: in COPD (chronic obstructive pulmonary disease) patients, such as emphysema and chronic bronchitis, respiratory control responds to O2 levels in the arterial blood. You feel an urge to breath when O2 level is low.
  • Prolonged administration of high concentration O2 in a COPD patient may cause the patient to stop breathing.

Respiration terms

  • Respiration: the entire process of gas exchange.
  • Oxygenation: the process of getting oxygen to blood and cells.
  • Ventilation: the mechanical process of breathing.


  • Hypoxia = not enough oxygen.
  • Causes: occluded airway, inadequate breathing, shock, CO poisoning, diseases... etc.
  • Signs of mild hypoxia
    • Tachypnea: increase in respiratory rate.
    • Dyspnea: shortness of breath.
    • Pale, cool and clammy skin.
    • Tachycardia: increase in heart rate.
    • Hypertension.
    • Restlessness, agitation and combativeness.
    • Disorientation / confusion.
    • Headache.
  • Severe hypoxia
    • Tachypnea
    • Dyspnea
    • Cyanosis: late sign of hypoxia - bluish color of the lips, inside the mouth, conjunctiva, and nail beds.
    • Tachycardia and/or dysrhythmia (irregular heart rhythm), which eventually leads to bradycardia.
    • Altered mental status.
    • Sleepiness.
    • Head bobbing.
  • Treatment:
    • Opening the airway.
    • Administer high concentration O2 via nonrebreather mask.
    • Provide positive pressure ventilation.

Gas exchange

  • Diffusion governs gas exchange. Things diffuse from an area of high concentration to an area of low concentration.
  • In the lungs, O2 diffuses from the air into the capillary and CO2 diffuses from the capillary into the air.
  • In the body, O2 diffuses from the capillary into the cells and CO2 diffuses from the cells into the capillary.

Airway in infants and children

  • Airway becomes more easily obstructed in children due to:
    • Smaller mouth and nose.
    • Larger tongue.
    • Narrower trachea and lower airway.
    • Larger head that tilts to obstruct the airway when lying supine. Children requires padding on the back when lying supine
    • Less rigid cricoid cartilage, which is also the narrowest part of the upper airway.
  • Softer chest wall which requires more use of the diaphragm for breathing.
  • The softer chest wall means that a child's lungs can easily be over inflated during artificial ventilation.
  • Children have smaller O2 reserve and a higher metabolic rate, which means that hypoxia can easily be a problem.
  • Hypoxia is the leading cause of cardiac arrest in children.

Signs to look for in airway

  • Alert, responsive and talking patients have a patent airway, which means that it is open. This is good.
  • Altered mental status patients cannot protect their airway
    • The tongue may obstruct the pharynx.
    • Loss of gag reflex may cause aspirations of food / vomit.
  • Facial injuries like burns or trauma may block or deform the airway.
  • Snoring: caused by the tongue obstructing the airway. Treat by head-tilt chin-lift or jaw thrust and / or insert airway adjunct.
  • Crowing: caused by muscle spasms around the larynx. Administer oxygen and artificial ventilation.
  • Gurgling: caused by liquid in the airway. Treat by suctioning.
  • Stridor: swelling of the larynx. Administer oxygen and artificial ventilation.

Airway Techniques

  • Opening the mouth: patient supine, you position behind the patient, and then use a crossed thumb-forefinger to open the mouth by the teeth using a scissors motion.
  • Opening the airway:
    • Head-tilt chin-lift: position to the side of a supine patient. Hold down the forehead with one hand, lift up the chin with the other. Do not perform on patients with spinal injury.
    • Jaw thrust: position behind a supine patient. Firmly hold the head and jaw on both sides with your hands. Thrust the jaw forward with your fingers. No spinal movement involved.
  • Suction
    • Do not suction below the base of the tongue.
    • Always suction using the catheter on its way out.
    • Suction for no more than 15 s at a time for adults and 5 s for infants and children.
    • Provide PPV (positive pressure ventilation) and O2 if the patient if suctioning causes inadequate respiration.
    • Hard / rigid catheter: also called the Yankauer, tonsil tip or tonsil sucker. Used to suction the mouth and oral pharynx.
    • Catheter size for the mouth is measured from the corner of the mouth to the earlobe.
    • Soft catheter: also called the "French" catheter. Can be used to suction the nose and nasopharynx.
    • Catheter size for the nose is measured from the tip of the nose to the earlobe.
    • Stoma: For patients undergoing tracheostomy or laryngectomy, a stoma is created - a hole in the neck that serves as the airway opening. Treat the stoma as the opening at which you perform suction and artificial ventilation.
  • Abdominal thrusts (Heimlich maneuver): removes airway obstruction when a conscious patient is choking on something. Stand behind the patient, hug and grasp around the abdomen, and then thrust inward and upward.
  • Back slaps: for conscious, choking infants below 1 years of age. Tilt the infant downward, then slap on the back.
  • Oral adjuncts
    • Oropharyngeal airway (oral airway):
      • Measure from the corner of mouth to earlobe.
      • Holds open the airway through the mouth (protects the tongue from blocking the airway).
      • Cannot use on patients with a gag reflex.
    • Nasopharyngeal airway (naso airway):
      • Measure from the tip of the ear to earlobe.
      • Holds open the airway through the nostrils.
      • May work even in the presence of a gag reflex.
  • Recovery position: protects from aspiration by placing the patient in a coma / recovery position. The patient is placed on his or her side with the arm not touching the ground folded such that the hand is beneath the head. The patient can vomit as much as he or she likes, and the vomit will flow right out. For obese or pregnant patients, grasp at the midline of the sternum.

Breathing properties

  • Rate: breaths per minute
  • Volume: volume per breath
  • Tidal volume: total volume of alveolar volume and dead air space combined.
  • Alveolar volume: air that reaches the alveoli and can participate in gas exchange.
  • Dead air space: air in the respiratory tract that never reaches the alveoli and cannot participate in gas exchange.
  • Minute volume = breaths per minute x volume per breath = volume per minute.
  • Alveolar ventilation = breaths per minute x alveolar volume per breath = alveolar volume per minute.

Signs to look out for adequate breathing

  • Can talk with ease.
  • Rate: 10-24 for adults, faster for children, up to 50 in infants.
  • Volume: adequate chest rise and fall.
  • Normal breathing sounds.
  • Clear breath sounds from ausculating the chest that are equal on both sides.

Signs to look out for inadequate breathing

  • Tripod position.
  • Retractions: pulling inward of above the clavicles, between ribs, and below the rib cage.
  • Increased effort to breath.
  • Use of accessory muscles.
  • Nasal flaring.
  • Agonal respirations (gasping).
  • Cool and clammy skin.
  • Hypoventilation: either rate or volume is inadequate.
  • Rate: abnormal rate and/or irregular rhythm.
    • Bradypnea: breathing too slow.
    • Tachypnea: breathing too fast (inadequate because breathing is also shallow).
  • Volume: shallow, inadequate depth, inadequate chest rise, unequal chest expansion.
    • Hypopnea: low volume breathing.
  • Abnormal or absence of breath sounds.
  • Signs of hypoxia (see above in the hypoxia section).

Artificial ventilation

  • Artificial ventilation is required with breathing is inadequate (either rate or volume is inadequate, or both).
  • Mouth-to-mouth.
  • Mouth-to-mask: using a pocket mask.
  • Bag-valve mask (BVM) operated by one person: one hand holding the face-mask seal, the other hand squeezes the bag.
  • Bag-valve mask (BVM) operated by two people: one person holds the face-mask seal with both hands, the other person squeezes on the bag.
  • CPR: Chest compressions (chest compressions are NOT for breathing, they are for circulation) coupled to BVM for a pulse-less, non-breathing patient.
  • Flow-restricted, oxygen-powered ventilation device: also called a demand-valve device. Delivers 100% O2, no need for squeezing to ventilate.
  • Cricoid pressure: also called the Sellick maneuver. BURP (backwards, up, right pressure) on the cricoid cartilage. This blocks the esophagus at the cricoid, preventing stomach inflation or aspirations during artificial ventilation.
  • Spinal stabilization: for patients with suspected spinal injury, you need to hold C-spine. If you are by yourself and performing BVM ventilation, kneel and use your legs to hold C-spine.
  • Stoma: For patients undergoing tracheostomy or laryngectomy, a stoma is created - a hole in the neck that serves as the airway opening. Treat the stoma as the opening at which you perform suction and artificial ventilation.

Ventilation effectiveness

Property Effective Ineffective
Rate Once every 5-6 s for adults with pulse. 3-5 s for infants and children with pulse. 30 compressions followed by 2 ventilations for CPR (no pulse). Too fast of a rate causes gastric distention (you're inflating the stomach). Too slow of a rate is inadequate.
Volume Consistent, adequate tidal volume causing adequate chest rise. Delivered over a 1 second period. No chest rise observable.
Heart rate Heart rate return to normal. Hypoxic signs: tachycardia, disrhythmia, bradycardia.
Skin color Decreasing pallor or cyanosis Hypoxic signs: pallor or cyanosis

If Ventilation not ineffective

  • Rate and volume: make sure you get these right. Perhaps try a larger tidal volume.
  • Reposition the head and neck.
  • Interchange between head-tilt chin-lift and jaw thrust.
  • Make sure you have a good face-mask seal. Readjust if necessary.
  • Consider inserting an airway adjunct.


  • Typically, O2 therapy = 100% O2 at 15 lpm via a nonrebreather mask.
  • Oxygen tanks are always in green.
  • A full tank is at 2000 psi.
  • Safety hazards: high pressure, highly flammable.
  • Oxygen humidifier: container filled with water, connects to the regulator of oxygen tank. Oxygen bubbles through water to be humidified. Moist oxygen is less irritating to the respiratory tract.
  • Nonrebreather mask: ensures the patients breath in 100% O2. Has an oxygen reservoir bag and a valve that prevents rebreathing of exhaled air. Always make sure the reservoir bag is filled up.
  • Nasal cannula: O2 tubes connected into the nostrils. Flow rate should be 1-6 lpm. For those who won't tolerate masks.
  • Other masks:
    • Simple face mask: No oxygen reservoir bag.
    • Partial rebreather mask: Similar to nonrebreather, but has a two-way valve that allows partial rebreathing of exhaled air.
    • Venturi mask: allows for precise control of concentrations of oxygen. Useful for COPD patients.