Airway Management, Respiration, & Artificial Ventilation

• Tidal volume: amount of air moved in or out of the lungs during a single breath.

  500-600mL in Males
• Inspiratory reserve volume: additional amount of air that can be inhaled after normal TV has been reached - 2,000 - 3,000mL
• Expiratory reserve volume: additional amount of air that can be exhaled after normal TV is expelled - avg 1,200mL
• Gas flows from an area of higher pressure to an area of lower pressure
• Inspiration (active):

  • Chest wall expands causing inc in size of thoracic which expands lungs
  • Lung space inc causes a drop in intrapulmonic pressure to abt 1mmHg below atmospheric pressure
  • Pressure gradient cause gas to go into lungs
  • Thorax/Alveoli stops expanding - intrapulmonic = atmospheric
  • diaphragm & intercostal muscle contract
• Expiration (Passive):

  • Chest wall relaxes - thorax/lung space decrease in size which increases intrapulmonic pressure
  • Pressure gradient causes dec in alveolar volume, inc in intrapulmonic pressure to abt 1mmHg over atmospheric pressure
  • Gas flow out of lungs
  • diaphragm & external intercostal muscles relax
• Anatomical dead space: inspired air that fills upper respiratory tract & lower non respiratory bronchioles but never reaches alveoli for gas exchange.
• Physiological dead space: anatomical dead space + volume of any nonfunctional alveoli
• Residual volume: gas that remains in respiratory system after expiration - 1,000 to 2,000mL
• Total lung capacity: (inspiratory + expiratory reserve volumes) + (TV + residual volume) ~5800mL
• Vital capacity: volume of gas moved on deepest inspiration & expiration ~4600mL
• Minute volume: TV x RR - amount of gas inhaled/exhaled in a minute

  • if dec, pt is not ventilating adequately
  • inc in TV or RR, inc MV
• Diffusion ceases when alveolar & capillary partial pressures become equal - this may be affected by destruction of alveolar sacs or decreased permeability in alveolar capillary membrane
• Phrenic nerves are responsible for moving diaphragm & 11 pairs of intercostal nerves are responsible for intercostal muscles - nerve impulses originate from medulla
• Vagal: prevent overinflation of lungs - conveys information from vagus nerve to medulla, respiration stop so lungs deflate
• Pneumotaxic center - in pons, has an inhibitory effect on inspiratory center
• Apneustic center: lower portion of pons - stimulates inspiratory center
• Chemoreceptors: monitor arterial PO2 - in the medulla & carotid/aortic bodies - these have intimate contact w/ arterial blood of great vessels
• Pulsus paradoxus: a drop of 10mmHg or more in systolic BP on inspiration - seen in pt with asthma, COPD, pericardial tamponade
• Agonal: slow, shallow, irregular breathing resulting from brain anoxia
• Ataxia: irregular breathing pattern series of inspirations and expirations; linked to lesion in medullary respiratory center
• Biot's: irregular pattern, rate, & volume with periods of apnea - linked to ICP
• Cheyene-Stokes: RR & TV gradually inc. followed by gradual dec w/ periods of apnea - linked to brain stem insult
• Kussmaul: deep, rapid breathing pattern - linked with DKA
• Apneustic: Prolonged, gasping inhalation followed by extremely short, ineffective exhalation; associated with brainstem insult.
• Nasal Cannula: 1-6lpm - provide O2 concentration of 24-44%
• NRB: 15lpm - concentration O2 up to 90%
• BVM: 15lpm - concentration O2 nearly 100%
• Partial Rebreathing Mask: lacks a one-way valve between the mask and the reservoir - 6-10lpm - concentration O2 of 35-60%
• D cylinder: 350L - factor 0.16
• M cylinder: 3000L -factor 1.56
• E cylinder: 625L - factor 0.28
• Duration of Flow in min = ((Tank Pressure in psi − 200 psi [the safe residual pressure]) × Cylinder Constant)/Flow Rate in L/min 
• CPAP: provides ventilatory support for patients experiencing respiratory distress - inc pressure in lungs, opens collapsed alveoli and prevents further alveolar collapse, pushes more O2 across alveolar membrane, & forces interstitial fluid back into pulmonary circulation.
• Indications for CPAP:

  • Pt is alert
  • Signs of severe respiratory distress - COPD, pulmonary edema, acute bronchospasm, pneumonia
  • SPO2 less than 90%
• Contraindication for CPAP:

  • Pt is unresponsive, unable to speak, protect own airway, sit up
  • Respiratory arrest or agonal respirations
  • Hypoventilation
  • Hypotension
  • S&S of pneumothorax or chest trauma
  • Closed head injury
  • Facial trauma
  • Cardiogenic shock
  • Tracheostomy
  • History of recent GI surgery
  • Active GI bleeding surgical procedure
• Whistle-Tip: narrow, flexible - mainly used for tracheobronchial suctioning to clear secretions through either an ET tube or nasopharynx
• Yankauer (Tonsil-Tip Suction): rigid pharyngeal catheter - used to clear secretions, blood clots, other foreign material
• Nasogastric Tube: inserted through the nose, into nasopharynx, through esophagus, & into stomach. It decompresses stomach, thereby decreasing pressure on diaphragm & limiting the risk of regurgitation.
• Orogastric Tube: inserted through mouth - decompresses stomach