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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.
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
Assist Control (AC)
Every breath is either a machine driven (set by rate) or fully assisted (initiated by the patient)
Uses either pressure (ACPC) or volume (ACVC)
Synchronized Intermittent Mechanical Ventilation (SIMV)
Set number of machine driven breaths, and patient intitated breaths are partially assisted
Pressure Support (PS)
No machine driven breaths and all breaths are initiated by the patient and partially assisted
Tidal volume (cc)
Positive End Expiratory Pressure (PEEP)
The pressure left in the circuit at the end of expiration
Prevents alveolar collapse and improves oxygenation
Can cause barotrauma and affect hemodynamics
(For this section, refer back to the vent picture above)
Fraction of Inspired Oxygen (FiO2)
Start at 100% and titrate down to 21%
f (machine breath rate)
Pressure Control (PC)
Inspiratory pressure (Pi)
Peak pressure in circuit
Initial setting = < 20 cm H20
Inspiratory time (I-time)
Initial setting = 1.25 seconds
Volume Control (VC)
Vt (tidal volume of each breath)
Initial setting = 6-8 cc/kg IBW
Vmax (flow rate)
Trigger for spontaneous support
Volume = V-trig
Pressure = P-trig
Pressure Support (PS)
I was always taught at least 5 cm H20 to overcome circuit resistance
Flashing “C” and “S”
Lets you know what breaths are controlled (machine) or spontaneous (patient)
Ppeak (max airway pressure)
A marker of resistance
Pmean (average airway pressure)
A measure of alveolar pressure
Pplat (small airway and alveoli pressure)
A measure of compliance
Total (machine + spontaneous breaths) I:E (inspiratory:expiratory ratio)
Normal = 1:2 (at rest)
Inverse ratio (2:1) can improve oxygen due to intention auto-PEEP
Wes Johnson’s Approach to Setting Up a Ventilator (after RSI)
Vt: 6-8 mL/kg based on pt’s IBW
Rate: 12-16 bpm
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
Respiratory Review YouTube Channel
https://www.youtube.com/channel/UCtaRF58UDVthvH36YYCttng Deranged Physiology. Mechanical Ventilation.
http://www.derangedphysiology.com/main/core-topics-intensive-care/mechanical-ventilation-0 Weingart SD – “Spinning Dials – How to Dominate the Ventilator” –
Weingart SD. Managing Initial Mechanical Ventilation in the Emergency Department. Annals of emergency medicine. 2016; 68(5):614-617. [
Air Link Regional West – “Initial Adult Ventilator Settings” –
https://www.rwhs.org/sites/default/files/airlink-factsheet-ventsettings.pdf Open Anesthesia. Modes of Mechanical Ventilation.
https://www.openanesthesia.org/modes_of_mechanical_ventilation/ Modern Medicine Network. A Quick Guide to Vent Essentials.
Tobin MJ. Extubation and the myth of “minimal ventilator settings”. American journal of respiratory and critical care medicine. 2012; 185(4):349-50. [
What are some of the chest scores we use to evaluate the likelihood a patient with chest pain is having ACS?
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:
Acute Myocardial Infarction
Pneumothorax (risk of tension)
Pericarditis (risk of tamponade)
There are a few others that should also cross your mind:
Esophageal Rupture (Boerhaave’s Syndrome)
Acute Chest Syndrome in Sickle Cell patients
The Five Deadly Causes of Chest Pain Other than Myocardial Infarction. JEMS. 2017
Chest Pain. Life in The Fastlane. Woods WA, Young JS, Just JS. Emergency Medicine Recall. 2000.
What are the 5 main life-threatening causes of chest pain?
Other Known Aliases – I nguinal triangle, medial inguinal fossa
Definition – Anatomical 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.
Clinical Significance – The area is where direct hernias protrude through the abdominal wall.
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.
From his 1806 manuscript
Firkin BG and Whitwirth JA.
Dictionary of Medical Eponyms. 2nd ed. New York, NY; Parthenon Publishing Group. 1996. Bartolucci S, Forbis P. Stedman’s Medical Eponyms. 2nd ed. Baltimore, MD; LWW. 2005.
Yee AJ, Pfiffner P. (2012). Medical Eponyms (Version 1.4.2) [Mobile Application Software]. Retrieved
Whonamedit – dictionary of medical eponyms.
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. [
Hesselbach HK. Anatomisch-chirurgische Abhandlung über den Urspurng der Leistenbrüche. Würzburg, Baumgärtner. 1806.
Hesselbach HK. Neueste anatomisch-pathologische Untersuchungen über den Ursprung und das Fortschreiten der Keisten- und Schenkelbrüche. Würzburg, Stahel. 1814
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.
This is probably the most well known and estimates severity on admission and mortality after 48 hours:
Glucose > 200 mg/dL
AST > 250
LDH > 350
Age > 55
WBC > 16,000
≥ 3 suggests severe pancreatitis and ICU admission
After 48 hours
> 10% decrease in hematocrit
> 5 mg/dL increase in BUN
< 8 mg/dL in serum calcium
< 60 mmHg in PaO2
> 4 base deficit
> 6L fluids needed
0-2 – 1%
3-4 – 15%
5 – 40%
Bedside Index of Severity in Acute Pancreatitis (BISAP)
BUN > 25 mg/dL
GCS < 15
Evidence of SIRS (2 of the following)
Temp < 36oC or > 38oC
Respiration > 20 or PaCO2 < 32 mmHg
Heart rate > 90 bpm
WBC < 4000, > 16,000, or > 10% bands
Age > 60
Imaging reveals pleural effusions
0-2 – < 2%
3-5 – > 15%
CT Severity Index (CTSI)
Assesses severity of pancreatitis via contrast enhanced CT and is the the sum of two scores:
0 – normal pancrease
1 – enlargement of pancrease
2 – inflammatory changes in pancrease and peripancreatic fat
3 – defined single peripancreatic fluid collection
4 – two or more poorly defined peripancreatic fluid collections
0 – none
2 – < 30%
4 – 30-50%
6 – ≥ 50%
0-3 – mild
4-6 – moderate
7-10 – severe
Glasgow-Imrie Criteria for Severity of Acute Pancreatitis
This one has a nice mneumonic (PANCREAS):
PaO2 < 60
Age < 55
Neutrophil (WBC) > 15,000
Calcium < 8 mg/dL
Raised BUN > 45 mg/dL
Enzyme (LDH) > 600 IU/L
Albumin < 3.2 g/dL
Sugar (glucose) > 180 mg/dL
≥ 3 points suggests severe disease
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. [
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. [
Balthazar EJ, Robinson DL, Megibow AJ, Ranson JH. Acute pancreatitis: value of CT in establishing prognosis. Radiology. 1990; 174(2):331-6. [
Knipe H, Cuete D. CT Severity Index in Acute pancreatitis. Radiopaedia.
Blamey SL, Imrie CW, O’Neill J, Gilmour WH, Carter DC. Prognostic factors in acute pancreatitis. Gut. 1984; 25(12):1340-6. [