topic 3

• Ngayon, lahat ng ventilators is gumagamit ng PPV.
• Positive Pressure Ventilation

  Uses positive pressure to bring air into the lungs
• Types of Positive Pressure Ventilation


  • Volume type
  • Pressure type
  • Pressure and Volume (Advance Modes)

  
• Pressure and Volume (Advance Modes)

  Pwedeng ma-control or set yung volume and the pressure at the same time
• Most commonly, yung mga conventional ventilators natin, ang mga modes is either volume or pressure type lang. Bihira yung mga ventilators or modes na pinagsasabay yung pressure and volumes.
• Sa CVMC (or sa mga hospitals), usually na ginagamit na mode is conventional lang, either volume or pressure lang.
• Sa volume and pressure type, each mode has certain parameters na meron sa volume type na hindi sine-set sa pressure type, and vise versa.

  
• Barometric Pressure (PB)


  The pressure exerted by the weight of the atmosphere
• Alveolar Pressure (PALV)


  The pressure inside the alveoli of the lungs
• Spontaneous Breathing

  1. Inspiration: PB 0, PALV -5, Flow into lungs

  2. End-Inspiration: PB 0, PALV 0, No flow

  3. Expiration: PB 0, PALV +5, Flow out of lungs

  4. End-Expiration: PB 0, PALV 0, No flow
• During spontaneous breathing, respiratory muscles in the diaphragm generate negative pressure in order for the air to flow inside the lungs.
• Inspiration: Mas mababa yung pressure sa alveoli compared sa PB para pumasok yung hangin.
• End-Inspiration: nag-e-equalize lahat ng pressures, no pressure gradient, kaya nags-stop yung air flow.
• Expiration: once expiration starts, nag-ge-generate ng positive pressure yung alveoli para lumabas yung hangin sa lungs
• End-Expiration: Equalized lahat ng pressures
• Positive Pressure Ventilation


  1. Inspiration: Pi 20, PALV 0, Flow into lungs

  2. End-Inspiration: Pi 20, PALV 20, No flow

  3. Expiration: Pi 0, PALV 20, Flow out of lungs

  4. End-Expiration: Pi 0, PALV 0, No flow

  
• Inspiration: Nag-i-induce na ng PPV or peak inspiratory pressure (PIP/Pi), and mas mataas na si Pi compared to Palv (which is 0), so that the pressure gradient itutulak yung hangin papasok sa lungs.

  
• End-Inspiration: nagpa-pantay sila pareho or parehong positive (equalized na sila) para tumigil yung pasok ng hangin
• Expiration: Pi = 0, so tumitigil yung machine na magbigay ng pressure. Palv naman ang naglalabas ng hangin kaya nag-ge-generate siya ng positive pressure (which is 20) palabas ng lungs
• End-Expiration: lahat 0, hindi pwedeng may positive pressure kasi it means nasa inspiratory phase tayo, kaya 0 siya.
• Airway Pressures


  • PAP (Peak Airway Pressure)
  • PPlat (Plateau Pressure)
  • mPaw (Mean Airway Pressure)
  • Vt (Tidal Volume)
  • PFR (Peak Flow Rate)
  • Raw (Airway Resistance)

  
• Airway pressures Have direct impact on: Intrathoracic pressure, Blood flow, Blood pressure and Indirectly on major organs

  
• If ever may tinaas na parameters sa Airway Pressures


  the also increases, and vise versa
• Compliance


  Has something to do with positive pressure (intrathoracic pressures)
• Lungs with normal compliance - 50% of airway pressure is transmitted to the thoracic cavity.
• Lungs with low compliance - pressure transmitted to the thoracic cavity is much less due to the dampening effect of nonelastic tissues.
• Kapag tumigas yung baga like cystic fibrosis, yung pressure na sinet is hindi masyadong mae-expand yung lungs. Therefore, yung pressure na dapat mapupunta sa intrathoracic is mababa rin or hindi na 50% or male-lessen siya.
• For this reason, the decrease in cardiac output due to excessive PIP or PEEP is less severe.
• Kahit na mag-increase ng PIP or medyo tumaas ang PEEP, hindi na siya ganun kataas and hindi na siya ganun ka-severe yung magiging effect sa CO.
• If COPD px (↑ compliance), their CXR shows right-sided heart failure or enlargement on the right side of the heart (cor pulmonale) because hyperextended na yung lungs and nagiging side effect is nai-impede or collapsed yung pulmonary blood vessels. Therefore, dapat na normal na pulmonary circulation is naco-compromised. So kumokonti yung dumadaloy na dugo sa lungs and nagkakaroon ng backflow papunta sa right side or overflow causing enlargement on the right side of the heart.
• PIP, I time, RR, PEEP


  Should be kept at minimum to keep mPaw at lowest possible level
• The 4 parameters (PIP, I time, RR, PEEP), is nakaka-apekto sa mPaw. If ever na nag-increase sa kahit alin sa 4 na yan, automatic increase din ang mPaw.
• mPaw is dapat mababa lang.
• Decrease in Cardiac output

  Caused by decrease O2 content x ↓ CO = and also ↓ O2 delivery
• Just like COPD kasi masyadong mataas ang pressure nila, cardiac output will ↓.
• Ganun din kapag nasobrahan ng pressures na binibigay sa px, effect is decrease CO of heart causing decrease in O2 delivery. Syempre, kung mababa yung perfusion, mababa din yung magiging O2 content and mababa din yung O2 sa venous.
• PPV leading to Decrease in O2 Delivery

  1. PPV ↑ Intrathoracic Pressure

  2. Compression of Pulmonary Vessels and Great Vessels

  3. Reduction in stroke volume

  4. Reduction of CO and Pulmonary Blood Flow

  5. High V/Q mismatch

  6. Hypoxemia

  7. Decreased O2 Content

  8. Decrease in O2 delivery to the tissues

  
• Kapag nag-induce ng PPV, automatic ↑ Intrathoracic Pressure. Effect: Compression of Pulmonary Vessels and Great Vessels, leading to ↓ in stroke volume. So pag nag-↓ ang stroke volume, automatically CO ↓ and perfusion (pulmonary blood flow). If nagkaroon ng ↓ perfusion, effect is nagkakaroon ng high V/Q mismatch. Sa upper part ng lungs, anong V/Q ang nakikita? INCREASE V/Q MISMATCH would lead to hypoxemia, and nagkakaroon ng ↓ O2 content and O2 delivery to the tissues.

  
• Pulsus Paradoxus during spontaneous breathing

  ↓ in systolic in asthma patient, cardiac tamponade >10 mmHg
• Reverse Pulsus Paradoxus: (if nag-induce ng) Spontaneous to PPV


  ↑ in systolic >15 mmHg - causing hypovolemia