#36 – Basics of the Ventilator with Wes Johnson, PA-C



Guest Information


Wes Johnson, MSPAS, PA-C, (soon to be), DHSc was a former student of mine at UAB and was a respiratory therapist prior to PA school.  He is the Regional Director of Clinical Education for Island Medical Management Emergency group in North Alabama.  He won the Preceptor of The Year award from UAB in 2016 and currently finishing up his doctorate degree from A.T. Still University.

Twitter – @wesj2288



For the purposes of this podcast and post, we will be using the Puritan Bennett 840 ventilator (pictured below).  All the term we use are synonymous with all vents, but the screens will be different.

Puritan Bennett 840

Big Concepts of The Ventilator


  1. Mode
    1. Assist Control (AC)
      1. Every breath is either a machine driven (set by rate) or fully assisted (initiated by the patient)
        1. Uses either pressure (ACPC) or volume (ACVC)
    2. Synchronized Intermittent Mechanical Ventilation (SIMV)
      1. Set number of machine driven breaths, and patient intitated breaths are partially assisted
    3. Pressure Support (PS)
      1. No machine driven breaths and all breaths are initiated by the patient and partially assisted
  2. Delivery
    1. Pressure
      1. Static Controls
        1. Pressure
        2. Time (inspiratory)
        3. Peak flow
      2. Variable Factors
        1. Volume
        2. Total flow
    2. Volume
      1. Static Controls
        1. Tidal volume (cc)
        2. Flow (L/min)
      2. Variable Factors
        1. Pressure
  3. Positive End Expiratory Pressure (PEEP)
    1. The pressure left in the circuit at the end of expiration
    2. Prevents alveolar collapse and improves oxygenation
    3. Can cause barotrauma and affect hemodynamics

Static Controls


(For this section, refer back to the vent picture above)

  1. Fraction of Inspired Oxygen (FiO2)
    1. Start at 100% and titrate down to 21%
  2. f (machine breath rate)
  3. Control
    1. Pressure Control (PC)
      1. Inspiratory pressure (Pi)
        1. Peak pressure in circuit
        2. Initial setting = < 20 cm H20
      2. Inspiratory time (I-time)
        1. Initial setting = 1.25 seconds
    2. Volume Control (VC)
      1. Vt (tidal volume of each breath)
        1. Initial setting = 6-8 cc/kg IBW
      2. Vmax (flow rate)
  4. Spontaneous Support
    1. Trigger for spontaneous support
      1. Volume = V-trig
      2. Pressure = P-trig
    2. Pressure Support (PS)
      1. I was always taught at least 5 cm H20 to overcome circuit resistance

Real-Time Controls


  1. Flashing “C” and “S”
    1. Lets you know what breaths are controlled (machine) or spontaneous (patient)
  2. Airway Pressure
    1. Ppeak (max airway pressure)
      1. A marker of resistance
    2. Pmean (average airway pressure)
      1. A measure of alveolar pressure
    3. Pplat (small airway and alveoli pressure)
      1. A measure of compliance
  3. fTotal (machine + spontaneous breaths)
  4. I:E (inspiratory:expiratory ratio)
    1. Normal = 1:2 (at rest)
    2. Inverse ratio (2:1) can improve oxygen due to intention auto-PEEP

Wes Johnson’s Approach to Setting Up a Ventilator (after RSI)


Mode: AC

Vt: 6-8 mL/kg based on pt’s IBW

Rate: 12-16 bpm

FiO2: 100%

PEEP: 5.0

At the 5-minute mark:

  • Check an ABG
    • Titrate FiO2 off of PaO2 and pulse oximeter
    • Adjust minute ventilation off of PaCO2 and/or ETCO2


  1. Respiratory Review YouTube Channel https://www.youtube.com/channel/UCtaRF58UDVthvH36YYCttng
  2. Deranged Physiology.  Mechanical Ventilation. http://www.derangedphysiology.com/main/core-topics-intensive-care/mechanical-ventilation-0
  3. Weingart SD – “Spinning Dials – How to Dominate the Ventilator” – https://emcrit.org/wp-content/uploads/vent-handout.pdf
  4. Weingart SD. Managing Initial Mechanical Ventilation in the Emergency Department. Annals of emergency medicine. 2016; 68(5):614-617. [pubmed]
  5. Air Link Regional West – “Initial Adult Ventilator Settings” – https://www.rwhs.org/sites/default/files/airlink-factsheet-ventsettings.pdf
  6. Open Anesthesia. Modes of Mechanical Ventilation. https://www.openanesthesia.org/modes_of_mechanical_ventilation/
  7. Modern Medicine Network.  A Quick Guide to Vent Essentials. http://www.modernmedicine.com/modern-medicine/content/tags/copd/quick-guide-vent-essentials
  8. Tobin MJ. Extubation and the myth of “minimal ventilator settings”. American journal of respiratory and critical care medicine. 2012; 185(4):349-50. [pubmed]

PAINE #PANCE Pearl – Emergency Medicine



What are the 5 main life-threatening causes of chest pain?



The 5 main life-threatening causes of chest pain you should ALWAYS think of are:

  1. Acute Myocardial Infarction
  2. Pulmonary Thromboembolism
  3. Pneumothorax (risk of tension)
  4. Pericarditis (risk of tamponade)
  5. Aortic Dissection

There are a few others that should also cross your mind:

  1. Esophageal Rupture (Boerhaave’s Syndrome)
  2. Acute Chest Syndrome in Sickle Cell patients
  3. Unstable angina



  1. The Five Deadly Causes of Chest Pain Other than Myocardial Infarction. JEMS. 2017
  2. Chest Pain.  Life in The Fastlane.
  3. Woods WA, Young JS, Just JS. Emergency Medicine Recall.  2000.



Hesselbach’s Triangle


Other Known Aliases – Inguinal triangle, medial inguinal fossa

DefinitionAnatomical region of the abdominal wall outlined by the boundaries of the lateral margin of the rectus sheath, the inferior epigastric vessels, and the inguinal ligament.

Inguinal triangle.png

Clinical Significance – The area is where direct hernias protrude through the abdominal wall.

Image result for direct hernia

History – Named after Franz Kasper Hesselbach (1759-1816), who was a German physician, surgeon, and anatomist in Hammelburg, Germany.  He had a prolific career surgical assistant and prosector under Karl Kasper von Siebold at The Juliusspital in Würberg, before obtaining his doctor of medicine there.  He is best known for his contributions to the surgery of hernias and has several other eponyms as well: Hesselbach’s fascia (cribriform fascia) and Hesselbach’s ligament (interfoveolar ligament.

Image result for franz kaspar hesselbach

From his 1806 manuscript


  1. Firkin BG and Whitwirth JA.  Dictionary of Medical Eponyms. 2nd ed.  New York, NY; Parthenon Publishing Group. 1996.
  2. Bartolucci S, Forbis P.  Stedman’s Medical Eponyms.  2nd ed.  Baltimore, MD; LWW.  2005.
  3. Yee AJ, Pfiffner P. (2012).  Medical Eponyms (Version 1.4.2) [Mobile Application Software].  Retrieved http://itunes.apple.com.
  4. Whonamedit – dictionary of medical eponyms. http://www.whonamedit.com
  5. Tubbs RS, Gribben WB, Loukas M, Shoja MM, Tubbs KO, Oakes WJ. Franz Kaspar Hesselbach (1759–1816): anatomist and surgeon. World journal of surgery. 2008; 32(11):2527-9. [pubmed]
  6. Hesselbach HK. Anatomisch-chirurgische Abhandlung über den Urspurng der Leistenbrüche. Würzburg, Baumgärtner. 1806.
  7. Hesselbach HK. Neueste anatomisch-pathologische Untersuchungen über den Ursprung und das Fortschreiten der Keisten- und Schenkelbrüche. Würzburg, Stahel. 1814

PAINE #PANCE Pearl – Gastrointestinal



What are the some of the pancreatitis scoring systems that are commonly used to estimate severity and mortality?



There are several scoring systems for estimating severity and mortality in pancreatitis.


  1. Ranson’s Criteria
    1. This is probably the most well known and estimates severity on admission and mortality after 48 hours:
      1. On Admission
        1. Glucose > 200 mg/dL
        2. AST > 250
        3. LDH > 350
        4. Age > 55
        5. WBC > 16,000
        6. ≥ 3 suggests severe pancreatitis and ICU admission
      2. After 48 hours
        1. > 10% decrease in hematocrit
        2. > 5 mg/dL increase in BUN
        3. < 8 mg/dL in serum calcium
        4. < 60 mmHg in PaO2
        5. > 4 base deficit
        6. > 6L fluids needed
        7. Predicted Mortality
          1. 0-2 – 1%
          2. 3-4 – 15%
          3. 5 – 40%
  2. Bedside Index of Severity in Acute Pancreatitis (BISAP)
    1. Predicts mortality
      1. BUN > 25 mg/dL
      2. GCS < 15
      3. Evidence of SIRS (2 of the following)
        1. Temp < 36oC or > 38oC
        2. Respiration > 20 or PaCO2 < 32 mmHg
        3. Heart rate > 90 bpm
        4. WBC < 4000, > 16,000, or > 10% bands
      4. Age > 60
      5. Imaging reveals pleural effusions
    2. Predicted Mortality
      1. 0-2 – < 2%
      2. 3-5 – > 15%
  3. CT Severity Index (CTSI)
    1. Assesses severity of pancreatitis via contrast enhanced CT and is the the sum of two scores:
      1. Balthazar Score
        1. 0 – normal pancrease
        2. 1 – enlargement of pancrease
        3. 2 – inflammatory changes in pancrease and peripancreatic fat
        4. 3 – defined single peripancreatic fluid collection
        5. 4 – two or more poorly defined peripancreatic fluid collections
      2. Pancreatic Necrosis
        1. 0 – none
        2. 2 – < 30%
        3. 4 – 30-50%
        4. 6 – ≥ 50%
      3. Assessment
        1. 0-3 – mild
        2. 4-6 – moderate
        3. 7-10 – severe
  4. Glasgow-Imrie Criteria for Severity of Acute Pancreatitis
    1. This one has a nice mneumonic (PANCREAS):
      1. PaO2 < 60
      2. Age < 55
      3. Neutrophil (WBC) > 15,000
      4. Calcium < 8 mg/dL
      5. Raised BUN > 45 mg/dL
      6. Enzyme (LDH) > 600 IU/L
      7. Albumin < 3.2 g/dL
      8. Sugar (glucose) > 180 mg/dL
    2. ≥ 3 points suggests severe disease



  1. Ranson JH, Rifkind KM, Roses DF, Fink SD, Eng K, Spencer FC. Prognostic signs and the role of operative management in acute pancreatitis. Surgery, gynecology & obstetrics. 1974; 139(1):69-81. [pubmed]
  2. Wu BU, Johannes RS, Sun X, Tabak Y, Conwell DL, Banks PA. The early prediction of mortality in acute pancreatitis: a large population-based study. Gut. 2008; 57(12):1698-703. [pubmed]
  3. Balthazar EJ, Robinson DL, Megibow AJ, Ranson JH. Acute pancreatitis: value of CT in establishing prognosis. Radiology. 1990; 174(2):331-6. [pubmed]
  4. Knipe H, Cuete D.  CT Severity Index in Acute pancreatitis.  Radiopaedia.
  5. Blamey SL, Imrie CW, O’Neill J, Gilmour WH, Carter DC. Prognostic factors in acute pancreatitis. Gut. 1984; 25(12):1340-6. [pubmed]


Murphy’s Sign


Other Known AliasesMoynihan’s Method (using just the thumb with patient supine)

DefinitionInspiratory arrest with deep palpation in the right upper quadrant 

Clinical SignificanceAs the patient exhales, the abdominal organs move cephalad and under the diaphragm.  After full exhalation and during inspration, the organs move caudal back into the abdominal cavity.  When there is inflammation of the gallbladder, the patient will stop inhaling as the inflammed gallbladder touches the practitioner’s fingers during deep palpation of the right upper quadrant.

History – Named after John Benjamin Murphy (1857-1916), who was an American surgeon and early pioneer for many different surgical operations and techniques.  In fact, William James Mayo (co-founder of The Mayo Clinic) called him “the surgical genius of our generation”. 

In 1889, he advocated for and popularized early appendectomy in all suspected appendicitis cases and had over 200 successful cases to begin convincing his colleagues of the benefits of early surgery.  Dr. Murphy also pioneered treatment of tuberculosis with iatrogenic pneumothoraces and was the first surgeon to re-anastomose a transected femoral artery from a gunshot wound.  He was also a distinguished teacher and developed “wet clinics” at Mercy Hospital, where he operated and lectured to an audience of learners in a traditional operative theater.


Dr. Murphy also attended to Theodore Roosevelt after an assassination attempt and was one of the founding members of the American College of Surgeons.  He is also the author of one of the more famous quotes pertaining to patient-centered care.


  1. Firkin BG and Whitwirth JA.  Dictionary of Medical Eponyms. 2nd ed.  New York, NY; Parthenon Publishing Group. 1996.
  2. Bartolucci S, Forbis P.  Stedman’s Medical Eponyms.  2nd ed.  Baltimore, MD; LWW.  2005.
  3. Yee AJ, Pfiffner P. (2012).  Medical Eponyms (Version 1.4.2) [Mobile Application Software].  Retrieved http://itunes.apple.com.
  4. Whonamedit – dictionary of medical eponyms. http://www.whonamedit.com