gas exchange

• the upper respiratory tract consists of

  • NOSE
  • MOUTH
  • SINUSES
  • PHARYNX
  • EPIGLOTTIS
  • LARYNX
• right lung has 3 lobes
• left lung has 2 lobes
• trachea (windpipe) - lined by pseudostratified ciliated epithelium, with c shape rings of cartilage
• bronchi - right and left mainstem
• trachea branches into:

  • right and left primary bronchi
  • secondary bronchi
  • bronchioles
  • terminal bronchioles
  • respiratory bronchioles
  • alveolar ducts
  • alveoli
• the respiratory rate is controlled by the respiratory centre, the medulla oblongata, in the brain
• the medulla oblongata responds to changes in carbon dioxide, oxygen, and ph levels in the blood
• respiratory rate = number of breaths per minute
• pulmonary circulation - gathers deoxygenated blood from the heart to be replaced with oxygen from the lungs
• oxygen is transported in the blood in two forms:

  • majority is bound to Hgb inside the RBC
  • small portion is dissolved in plasma
• how well oxygen is delivered depends on:

  • temp
  • ph
  • concentration of the component 2,3-bisphosphoglycerate
• the ability of the respiratory system to deliver o2:

  • inflated, well oxygenated alveolus
  • healthy capillaries
  • free flowing blood with adequate blood pressure
• impairment of gas exchange occurs when the diffusion of gases becomes impaired because of:

  • ineffective ventilation
  • reduced capacity for gas transportation
  • inadequate perfusion
• ventilation: the process of moving gases into and out of the lungs
• transport: the availability of hemoglobin and its ability to carry o2 from alveoli cells for metabolism, carry co2 produced by cellular metabolism from cells to alveoli to be elimenated
• perfusion: the ability of blood to transport o2 containing hemoglobin to cells and return carbon dioxide containing hemoglobin to the alveoli
• physiological factors affecting oxygenation

  decreased oxygen carrying capacity

  • anemia
  • inhaling toxins

  decreased inspired oxygen concentration

  • upper or lower airway obstruction

  hypovolemic

  • dehydration
  • decreased blood volume

  increased metabolic rate

  • pregnancy
  • fever
  • infection

  conditions affecting chest wall movement

  • pregnancy
  • obesity
  • trauma
  • neuromuscular disease
  • CNS alterations
• alterations in cardiac function

  impaired valvular function

  • acquired or congenital disorder of a cardiac valve caused by stenosis or regurgitation

  myocardial ischemia

  • coronary artery flow to the myocardium insufficient to meet myocardial oxygen demands
  • angina pectoris, myocardial infarction, acute coronary syndrome

  disturbances in conduction

  • caused by electrical impulses that do not originate from the SA node

  altered cardiac output

  • insufficient volume ejected into the systemic and pulmonary circulation
  • left sided heart failure
  • right sided heart failure
• hyperventilation: ventilation in excess of that required to eliminate carbon dioxide produced by cellular metabolism
• hypoventilation: alveolar ventilation inadequate to meet the body's oxygen demand or to eliminate sufficient carbon dioxide
• airway obstruction refers to an anatomic narrowing or occlusion, resulting in decreased ability to move air. may be acute or chronic; partial or complete; upper or lower, reversible or fixed
• etiology is any pathology that compromises airflow from the nasopharynx and oropharynx to the lungs can cause upper airway obstruction
• most often, etiologies that cause upper airway obstructions involve inflammation, infection, or trauma of the airway structures. an anatomical variant may also cause or contribute to obstruction
• anatomical obstruction is a physical blockage within the airway caused by structural anomalies or foreign objects that physically block or narrow the airway
• physiological airway obstructions are blockages within the airway that occur due to changes in the body's normal physiological processes, leading to impaired airflow. these obstructions are caused by conditions that affect the function of the airway rather than its structure
• in cases of acute obstruction of the airway, a history of the events leading to the obstruction may be critical to deciding the intervention. patient often present in acute distress, altered loc, and other signs of inability to move air. in more severe cases, patients may also present in the obtunded state or cardiopulmonary arrest
• ventilation perfusion mismatch (v/q) - an airway obstruction decreases or completely blocks airflow to the affected alveoli. this means less oxygen enters the alveoli, and less carbon dioxide is removed. despite the reduced ventilation, blood flow (perfusion) to these alveoli may remain normal, leading to a v/q mismatch
• hypoxia - decreased oxygen levels in blood
• hypercapnia - increased carbon dioxide levels in blood
• respiratory acidosis - accumulation of carbon dioxide can lower blood ph, making it more acidic
• signs of an airway obstruction

  • stridor
  • wheezing
  • use of accessory muscles
  • cyanosis
• symptoms of airway obstruction

  • dyspnea
  • anxiety or agitation
  • decreased oxygen saturation
• physical examination: inspection, palpating, percussion, auscultation
• pulse oximetry - measuring oxygen saturation levels
• arterial blood gases (abg's) : assessing oxygen, carbon dioxide, ph levels in blood
• imaging : x-ray, ct scan, mri, bronchoscopy
• immediate goal is relieving the obstruction, so gas exchange can proceed
• immediate and definite relief of obstruction may include:

  • removal of foreign body
  • naso tracheal intubation
  • endotracheal intubation
  • tracheostomy
  • cricothyroidotomy