< Back Thai Chicken Enchiladas Ingredients 8 flour tortillas 2 cooked and shredded chicken breasts 1 Tbsp canola oil 1/2 sweet onion, chopped 1/3 C chopped/shredded carrots 1/2 C chopped/shredded cabbage (premade coleslaw mix works well) 4 garlic cloves, minced 1/2 tsp salt 1/2 tsp pepper 4 green onions, sliced 1/3 C chopped peanuts (more for garnish) 1/4 C chopped fresh cilantro (more for garnish) 2 1/2 C light coconut milk 1/3 C + 1/2 C sweet chili sauce Instructions 1. Preheat oven to 350 degrees F. 2. Heat oil in large skillet over medium heat. Add onions, cabbage, carrots, garlic and 1/4 tsp salt and stir to mix. Stir occasionally and cool until vegetables are soft (6-8 min). Add in chicken, green onions, peanuts, cilantro, remaining salt and pepper, tossing to coat, cook for 1-2 min. Add 3/4 c coconut milk and 1/3 c sweet chili sauce, mixing thoroughly to combine. Turn off heat. 3. Spray 9×13 dish with nonstick spray. Whisk together remaining coconut milk and sweet chili sauce. Pour about 1/2 C on the bottom of the dish. Slightly warm tortillas, then place a few spoonfuls of the chicken mixture in each, roll up tightly and place in the dish. Use a spoon to cover the tortillas with remaining coconut milk and chili sauce mix. 4. Bake for 20 minutes, remove and garnish with peanuts and cilantro. Spoon sauce from the bottom of the dish all over the tortillas. The vegetables cooling and softening Previous Rolled up and ready to head into the oven Final product! Next

< Back Bowel Anastomosis A handsewn small bowel anastomosis can be created end to end or side to side. When creating a side to side anastomosis, the planned enterotomy site on each limb of bowel is identified. The backwall is created first, just lateral to the planned enterotomy sites- it would be very challenging to access this portion of the anastomosis after creating the inner layer. The back layer is followed by inner layers of absorbable suture. My personal preference is Vicryl, but PDS can also be used. Finally, the anterior outer seromuscular layer of silk is created. Posterior outer layer of interrupted 3-0 Silk Limbert sutures Posterior inner layer of interrupted 3-0 Vicryl sutures Anterior inner layer of Connell with 3-0 Vicryl Anterior outer layer or interrupted 3-0 Silk Limbert sutures Inner layer of absorbable sutures and outer seromuscular layer of silk. Two different depictions of side to side anastomoses (1,2). Rao SD. Small Intestine, In: Snapshots in Gastroenterology. Jaypee Brothers Medical Publishers (P) Ltd. 2016. Rao SD. Pre- and Postoperative Management in Midgut (Small Bowel) Surgery, In: Gastrointestinal Surgery Step by Step Management. Jaypee Brothers Medical Publishers (P) Ltd. 2005. Previous Next

Things I don't want to do (or do again) Anti-Bucket List Things I don't want to do (or do again) Experiences I don't care to repeat, but glad I did them once Tough Mudder Eaten alligator and shark Things others want to do that I have no desire to do Skydiving Scuba diving Attend the Masters Previous Next

Surgery trainee education. Trauma surgeon. Acute Care Surgery. FAQs Why did you make this website? Over these years of learning about the practice of surgery, I've also learned a lot about myself. I am not an expert, and I did not follow a typical pathway- but I have some knowledge and resources to share. As I transition into my new Acute Care Surgeon role after 17 years in training, I'm pausing to share my experience, tips for success, and random nuggets of wisdom. This will be a work in progress, and I look forward to seeing how it evolves. My goal is to share my experience and knowledge in the hopes of helping those who desire to follow this path. But why do we need another medical education website? There are so many good resources already... There are endless ways to explain clinical concepts- pictures, text, analogies, clinical cases, podcast discussions of cases or principles, review articles, etc. There are also different learning styles. When I was trying to grasp advanced ventilator management, I read basic critical care textbooks, a book dedicated solely to ventilator management, and various websites and journal articles. This website is another way to interact with the information. Hopefully you will understand some of the concepts in a new way that helps you remember and apply them in clinical scenarios. In addition, I have also tried to create a comprehensive collection of all the useful resources I know, like apps and open access medical education resources (websites, clinical guidelines, etc) in one place for trainees to What does Doc on the Run mean? The summer before my last year of medical school was the start of my running career. My focus was enjoying the outdoors, not pace or distance. During my residency, I met someone who helped me refine my running. I started timing myself, training, and racing. Within a year or two, I pushed through personal barriers to become a "runner." My first half marathon was on Thanksgiving in my third year of surgical residency. I am at the end of my formal training, I am now an Acute Care Surgeon. As a surgeon, there are numerous factors that I can't control. It's fast-paced, demanding, and dynamic. I enjoy the organized chaos and high-stakes cases. Running is key to my work-life balance. Unlike in the operating room or the trauma bay, I have control over most aspects of my runs- pace, distance, route, and thoughts. It's not chaotic- it's basically the polar opposite of my work. During the day, my mind is going a million miles an hour. When I run, everything becomes clearer- I can solve problems, mull over ideas, or process dilemmas. And perhaps the most concrete impact is the runner's high that I enjoy after finishing. I have continued to run 10Ks, 10 milers, and the occasional 5K or 15K. I have learned more about the science of running (HR training zones, different paces for tempo/ interval/ long runs/ short runs) and I've learned how to adapt training schedules to fit my life. Unfortunately, I have suffered my share of injuries, including most recently nerve impingement in my foot. While I may have scaled back, running will always be part of my identity. Did you really build this website yourself? Yes, I did. No, I didn't do all the intricate coding by myself. But I did design, format, and create the content. So are you a computer/ technology guru? Whatever I know about technology, I learned from my brother and from spending many hours researching problems online. While my parents might consider me an expert, I literally just search online to solve most issues. When I get to the end of the internet and still haven't found the solution, my next step is Apple tech support (obviously only if the problem is with my iPhone or Mac). What did you learn while making this website? - Formatting the working space on a website - URL redirect - Domains and subdomains - Search engine optimization (SEO) - Establishing custom domains - Which text/ background colors are easiest to read - Anchors If you weren't an Acute Care Surgeon, what would you do? I'd be a chef. I love cooking! Is there anything that is overwhelmingly gross in your job? I have had almost every body fluid on me- stool, urine, blood, etc. So very little grosses me out. But I can't stand oral or nasal secretions (aka saliva, slobber, snot, etc.).

< Back Shakshuka- A North African Dish Ingredients 1 large red bell pepper, thinly sliced 1 large yellow bell pepper, sliced 1 red onion, sliced 3-4 garlic cloves, diced ¾ tsp salt cracked pepper to taste 1 tsp cumin 1 tsp sugar ½ tsp smoked paprika ½ tsp chili flakes 3 medium tomatoes diced small ⅓ c white wine or water 1 T fresh basil ribbons or chopped Italian parsley 4 -6 Extra large organic eggs Other optional additions: crumbled feta or goat cheese 1 C browned chorizo ¼ C finely diced spanish style cured Chorizo or Merguez, a North African spiced sausage Instructions 1. Preheat oven to 400F. 2. In a large cast iron skillet, heat the olive oil over medium heat. Add the onion and cook until tender, about 5 minutes. If adding raw chorizo, brown it with the onions. 3. Add the sliced peppers and garlic, and turn heat down to med-low and cook for 5 more minutes, until peppers are tender. If adding the cured spanish chorizo or Merguez sausage, add it now. Add all spices, sugar and salt. Cook for 2 more minutes. Add fresh tomatoes and white wine. 4. Simmer on low for 15 minutes, adding more water if it gets too dry or thick- you want a stew-like consistency. After tomatoes cook down, taste, it should be full flavored- adjust salt and sugar if necessary. Crack 4-6 eggs over the mixture, sprinkling each egg with salt and cracked pepper. Add crumble goat cheese or feta over the top and place in the 400F oven. 5. Bake until egg whites are cooked (about 7 minutes) and yolks are still soft. Remove from oven and top with fresh basil (or Italian parsley). Serve with toast or crusty bread. Veggies sizzling Previous Ready for the oven Yummy! Next

< Back Interpreting Chest X-Rays Developing skill with radiographic interpretation requires practice. Look at every film for your patients. Practice by looking at normal films, then compare between normal and abnormal. For example, compare an image for a patient with a normal cardiac silhouette and compare it with a patient with an abnormal silhouette with a widened mediastinum. This is NOT an exhaustive list of everything that can be seen on a chest x-ray, but is an overview of common pathology that can be seen. How to read a film 1. Identify- correct patient/ date/ time. 2. Identify orientation. Is the projection posterior-anterior (PA) or anterior-posterior (AP)? Is the patient rotated? PA is when the patient stands with their chest facing the x-ray cassette and the x-ray is behind the patient, so the x-ray beam travels from the posterior of the patient toward the plate, which is situated on the patients anterior surface. AP is when the patient’s back is towards the board and the x-ray is in from front of the patient, so the x-ray beam travels from the anterior of the patient toward the plate, which is situated on the patient’s posterior. This is the orientation when a patient is laying supine in the trauma bay. On an AP film, the heart appears enlarged compared to the PA. Rotated- compare bilateral or midline structures, such as clavicles and the spinous processes of the vertebra. If the clavicles are asymmetric or the spinous processes are not midline, the patient is rotated. Structures (ABCs) 1. Airway Is the trachea midline? Are there any opacities in the lung fields- pneumonia, masses, bilateral haziness? Do the lung markings extend to the edge of the chest? If not, and the space area is dark, this is suggestive of a pneumothorax. In contrast, if the space is white, this is suggestive of a fluid collection (hemothorax, infected fluid, etc). Is there evidence of fluid? This depends on the patient’s postion and the consistency of the fluid. Free fluid (fresh hemothorax, pleural effusion) will layer dependently, so if the patient is upright, the costophrenic angles will be blunted. If the patient is supine, the fluid can cause generalized opacity of the lung field because it layers along the back of the patient. 2. Bones- examine for fracture, dislocation, masses (tumor) Upper extremity/ shoulder? Ribs? Vertebra? 3. Cardiac Silhouette size/ contour? Normal is <1/2 the size of the thoracic cavity Evidence of aortic injury? *Bonus- 3 places for blunt aortic injury- aortic root, diaphragm, and isthmus just past subclavian takeoff Widened mediastinum (supine >8 cm or upright > 6cm) Loss of aortopulmonary window Abnormal aortic contour Depressed left mainstem bronchus Left apical capping Left hemothorax Nasogastric tube deviation Widened paraspinal or paratracheal stripe 4. Diaphragm Elevated- symmetric elevation is consistent with poor inspiratory volume. Blunting of costophrenic angle- effusion. Abdominal contents in chest (ie gastric bubble in the left chest)- consistent with diaphragm injury or defect. 5. Everything else Air in soft tissue- many potential etiologies, but common causes include pneumothorax or esophageal/ airway disruption. Air under the diaphragm (pneumoperitoneum)- concerning for hollow viscus injury. Iatrogenic foreign bodies- endotracheal tube, central lines, ports, pacemaker, endovascular grafts, esophageal stents, feeding tubes Non-iatrogenic foreign bodies- swallowed objects Additional References and Images from Radiopaedia.org **Click on Cases and figures and Imaging differential diagnosis on the right-hand column of each page for more in-depth explanations of specific pathology** Radiopaedia Airway Bones and Soft Tissue Cardiac Silhouette and Mediastinum Widened Mediastinum Hemothorax Pneumothorax Nasogastric Tube Position Previous Next

< Back Snowboarding Gear and Resources I currently ride a true twin snowboard. Brand- Arbor Cadence Size- 147 cm Profile- System Rocker What kind of board I'm looking for? All-mountain Shape- directional twin Profile- rocker/ reverse camber Flexibility- medium Website Links On the Snow Up-to-date information about snow conditions. Projected resort opening/ closing dates. State Level Information- V irginia Snow Report Specific Resort Information- Jay Peak Apps On the Snow (see above) Epic Pass Slopes How to Choose a Snowboard Snowboardingdays.com REI.com How to Set Up Your Snowboard Burton.com Mounting Burton Bindings Miscellaneous Seven Most Dog-Friendly Ski Resorts in North America Previous Next

< Back Vent Mgmt #4: All Together Choosing a mode Controlled- patients who aren't generating breaths. PC, VC. Most common mode at initiation of MV. SIMV- patient generating some breaths, but still needs significant mechanical support. Spontaneous- not frequently used at initiation, but can be used for patients with airway obstruction and preserved lung function. How to set initial parameters TV (6-8 mL/ kg predicted body weight) [lung protective ventilation] RR 10-14 FiO2 often start at 100%, but quickly weaned unless severely hypoxic Inspiratory:expiratory ratio typically 1:2 Flow- typically set @ 60L/min, can increase if the patient is in distress or has a high minute ventilation How to adjust parameters based on arterial blood gas results Low PaO2 (low arterial oxygen content)- increase FiO2, increase mean airway pressure Markedly elevated PaO2 (hyperoxia)- decrease FiO2 Low PaCO2 (low arterial carbon dioxide concentration)- decrease TV or RR High PaCO2 (high arterial carbon dioxide concentration)- increase TV or RR *For more details, check out these resources: Lectures: Critical Care: Respiratory Failure Lectures: Critical Care: Vents Other principles of mechanical ventilation VAP bundle- elevated head of bed, oral care Daily awakening and spontaneous breathing trials Previous Next

< Back Vent Mgmt #2: Modes Mandatory Breaths Volume control (volume limited)- set TV and flow, pressure and inspiratory time are the dependent variables. Pressure control (pressure limited)- set inspiratory pressure and inspiratory time, volume and flow are the dependent variables. What is the downside of VC and PC? You can only control one parameter, and the dependent variable varies based on the patient's lung mechanics. For a patient on VC, if their lungs become less compliant, delivering the same tidal volume will generate higher pressure, increasing the risk of barotrauma. For a patient on PC, if their lungs become less compliant, the target pressure will be reached at a lower volume, so there is a risk of decreased ventilation (↑PaCO2). Pressure-regulated volume control (PRVC) is a hybrid mode that attempts to overcome this limitation. The target volume is delivered at the lowest possible inspiratory pressure by assessing the delivered tidal volume at the inspiratory pressure during each breath. What about inverse ratio (IR, IRV-PC) ? Increasing the inspiratory time relative to expiratory time increases mean airway pressure. This can be accomplished with pressure-controlled modes, where inspiratory time can be prolonged (normal ratio 1:2, IRV is when inspiratory time is greater than expiratory time). As discussed, MAP affects the surface available for oxygen exchange. This is why IR can be used to optimize oxygenation. Mandatory and Spontaneous Breaths Synchronized intermittent mandatory ventilation (SIMV)- a variation on VC or PC. The machine delivers mandatory breaths, but the patient can also control spontaneous breaths in between the mandatory breaths. Spontaneous Breaths Pressure support- spontaneous mode, the patient initiates breath, the ventilator provides support to overcome the resistance of breathing through the endotracheal tube, flow is adjusted to maintain the inspiratory pressure. The support is terminated when the flow decreases to <25% of peak flow. The patient controls duration and volume. *This is also a setting that can be adjusted in SIMV for assisting spontaneous breaths between ventilator breaths. Airway Pressure Release Ventilation (APRV)- invasive form of ventilation with BiPAP. The patient breaths spontaneously, alternating between a sustained time (time-high) at a set pressure (pressure-high) with a very brief release (time-low) of pressure (pressure low) to allow expiration. The goal is to maintain a higher MAP to optimize oxygenation. Previous Next

< Back ICU Rounding: How I Do It The ICU can be intimidating. Critically ill patients are often surrounded by machines (ventilators, dialysis, etc) and IV poles, with multiple lines and catheters extending from their face, chest, abdomen, neck, and groin. A standardized approach can help the team synthesize and interpret all the subjective and objective data to establish a diagnosis and devise a treatment plan for these complex patients. Rounding in the ICU is different from rounding on floor patients. Floor patients are typically presented in a problem-based format- they are likely to have a short list of active issues being addressed, often just one diagnosis (cholecystitis, bowel obstruction, colon cancer status-post colectomy). Patients can certainly have co-morbidities, such as diabetes and hypertension, but they are usually relatively straightforward. Presentations are briefer than ICU presentations, and largely focus on the acute surgical diagnosis. Here is an example of a surgical floor patient. 32 year old female, hospital day 2 following laparotomy for small bowel obstruction. Her pain is controlled with oral analgesics with minimal prn requirements. She is hungry and passing flatus. She is using her incentive spirometry and ambulating. She has had minimal output in her nasogastric tube. Staples are intact along her midline laparotomy incision with no surrounding erythema and appropriate peri-incisional tenderness. Labs are only remarkable for some mild hypokalemia with K 3.4. She is voiding spontaneously with adequate urine output. Plan to replete potassium, remove NGT and advance diet. In contrast, ICU patients are fragile with more physiologic derangements that threaten homeostasis. Critical illness can profoundly impact multiple organ systems and the interdependence of organ systems adds another layer of complexity. Patients can be presented in a problem-based format, like floor patients, or a system-based format. There are pros and cons to each. As mentioned, a problem-based format addresses each diagnosis (for example- cholecystitis, bowel obstruction, heart failure, pneumonia, ileus). In contrast, a system-based format addresses each organ system (for example- cardiac, pulmonary, renal, neurologic). Problem-based might seem easier on first glance, but one downside in the ICU setting is the risk of overlooking organ systems without a discrete disease process. One downside of the system-based format is the categorization of one diagnosis to various organ systems. For example, ventilator-associated pneumonia is related to the pulmonary system but overlaps with infectious disease. However, the system-based format is comprehensive and thorough, which helps ensure that all physiologic processes are considered. One advantage of the system-based format is it’s adaptability to less complex patients. While it’s challenging to apply floor round formatting to the ICU setting, once you understand how to utilize the ICU system-based model, you can use it to briefly review non-ICU patients to ensure that you don’t forget something. For a young male with cholecystitis, you don’t need to report GCS, medication infusion rates, ventilator settings, insulin requirements, etc. But the systems are still pertinent- address pain (neuro), ensure normal vitals (cardiac) and use of incentive spirometer (pulmonary), check oral intake, assess return of bowel function and examine wounds (GI), inquire about adequate urination and review BMP (renal), ensure no fever, review CBC (heme and ID), and ensure ambulation/ SCDs (prophylaxis). ICU care is a team endeavor, requiring the integration of nursing, respiratory therapy (RT), dieticians, pharmacists, physical therapy and other team members to provide comprehensive care. ICUs must implement a system to integrate care plans between all team members. This can occur in different formats, either with “prerounds” (brief discussion with multidisciplinary team about each patient before formal rounds) or with multidisciplinary rounds (team members present their key data points/ plans in a structured format). One example of multi-disciplinary rounds (abbreviated): resident reports one-liner (see example below); nurse reports their assessments (pain/ sedation scores, delirium assessment, etc); RT reports current ventilator settings, results of spontaneous breathing trials and respiratory treatments; the resident then presents the patient as below. Order of Presentation during Rounds 1. Brief one-liner [presented by the resident, APP or student caring for the patient]. See below. 2. Bedside nurse- report on sedation, pain, infusion rates, etc 3. Respiratory therapy- report on ventilator settings, respiratory interventions, etc 4. Formal patient presentation [presented by the resident, APP or student caring for the patient]. See below. 5. Pharmacist- review of medications, including potential dose adjustments, antibiotic tailoring, etc 6. Attending 7. FAST-HUG- ensure that key aspects of care are addressed (feeding, analgesia, sedation, thromboprophylaxis, head of bed elevated, ulcer prophylaxis, glycemic control) 8. Readback- nurse briefly summarizes the key goals of the day One-liner: brief patient history, acute overnight events. Example: 32 year old male, POD 7 exploratory laparotomy following motor vehicle collision, remains intubated for VAP. Formal Patient Presentation [Systems Based] Neurologic (Neuro) Diagnosis: Exam/ objective data. GCS, reflexes, pupils. ICP monitor. Medication: continuous infusions, requirements of prn analgesics Plan: Neuro- patient remains intubated and sedated, GCS 11T off sedation, currently on Fentanyl @ 100 mcg/ hr and propofol @ 20. Minimal requirements of prn analgesics. We will wean fentanyl infusion and use enteral multi-modal analgesia. Cardiac Diagnosis: Exam/ objective data. Vitals: describe the trend, know when outliers occurred (for example, an isolated heart rate (HR) of 130 during a procedure at noon the previous day is different from a sustained HR of 130s). If patient has any invasive monitoring, such as arterial pressure waveform analysis (FloTrac, Vigileo), pulmonary artery catheter or central line, include these as well. Medication: Plan: Cardiac: HR 90s-100s, Flotrac shows normal SVV. On norepinephrine, requirement is currently down to only 2 from a max of 10 yesterday, MAP goal of >65. Continue to wean norepinephrine. Remove arterial line once off norepinephrine for 12 hours. Pulmonary (Pulm) Diagnosis: Exam/ objective data: intubated, secretions, breath sounds, breathing pattern. Ventilator settings. Labs: ABG if performed. Imaging: note findings, and describe how it’s changed relative to prior imaging Medication: Plan: Example: Pulm- pt remains intubated, current ventilator settings. CXR still shows bilateral fluffy infiltrates. *on antibiotics day x of x for VAP, CXR worsening/ stable, secretions improving. Then, later: ID- patient is on antibiotics day x of x for UTI, and day x of x for VAP. Gastrointestinal (GI)/ Nutrition Diagnosis: Exam/ objective data: abdominal wounds, drains, stool management system, bowel function, nutrition. Medication: bowel regimen Plan: GI- patient started on tube feeds two days ago, but he’s having minimal stool output. Abdomen is distended and tympanitic. We held feeds this morning and have an abdominal plain film pending. Renal/ Fluids/ Electrolytes (Renal) Diagnosis: Exam/ objective data. IV fluids. Intake/ output. BMP. Medication: Plan: Renal- foley in place with good urine output, I/O 3.2L/2.9L. No continuous IV fluids. Electrolytes within normal limits. Hematologic (Heme) Diagnosis: Exam/ objective data. Labs: Hgb, Plt. Transfusion. Medication: Plan: Heme- stable mild anemia, checking CBC every Monday/ Wednesday/ Friday. Infectious Disease (ID) Diagnosis: Exam/ objective data. Labs: WBC, neutrophils. Culture results (sample source, date, results). Medication: current antimicrobials. Plan: ID- patient is on antibiotics day 2/5 for UTI, and day 2/5 for VAP. He has remained afebrile for the last 48 hrs. His WBC is downtrending. No pending cultures. Endocrine (Endo) Diagnosis: Exam/ objective data. Labs: glucose trend, insulin requirements Medication: Plan: Endo- stress hyperglycemia, glucose range from 210-240. Currently on SSI with 24 hr requirement of 22U. Increase to more aggressive sliding scale, but holding off adding scheduled/ basal insulin while adjusting his enteral nutrition. Prophylaxis/ Lines and Tubes GI prophylaxis DVT prophylaxis Location/ date of invasive lines and tubes Patient is on IV PPI for ulcer prophylaxis, on enoxaparin BID. PICC RUE, day 10. Foley, day 5. Helpful hints: - Be succinct and synthesize the data. Have all the information available if asked, but don’t report every single bit of data. - Some problems can be relevant to multiple systems. For example, ventilator-associated pneumonia is related to the pulmonary system but overlaps with infectious disease. You can pick one system to discuss it, but you can also briefly mention it in the other relevant system. For example: Pulmonary- patient remains intubated, on antibiotics day x of x for VAP, CXR worsening/ stable, secretions improving. Then, later: ID- patient is on antibiotics day x of x for UTI, and day x of x for VAP. - If the patient’s BMP is normal, you can state that instead of reading every value. If there is one lab value that is abnormal but the remainder is normal, you can say “normal except for [elevated potassium of 5.5]” - Be thoughtful about ordering labs and imaging. Daily CXR purely because a patient is intubated for a bad TBI is not necessarily helpful. Even if the patient is being treated for pneumonia, daily CXR is unlikely to change your management unless there is a clinical change. CXR is appropriate if there are specific interventions that were performed or if the patient has a clinical deterioration- for example, following placement of chest tube for pleural effusion, following 24 hours of aggressive diuresis, for evaluation of acute dyspnea/ hypoxia. - Don’t repeat information presented by other team members- if the nurse has already provided infusion rates or RT has already provided ventilator settings, just move through the next part of the presentation. ICU Rounds .pdf Download PDF • 46KB A-F Bundle .pdf Download PDF • 33KB Previous Next

< Back Vent Mgmt #3: Pressures Inspiratory Pressures Pressure Controlled Ventilation (PCV) End-inspiratory pressure= alveolar pressure. The pressure is essentially constant during PCV- high flow at the beginning to get to target pressure, then flow tapers until it ends (no airflow at end inspiration). Can't measure resistance because flow rate is dynamic. Volume Controlled Ventilation (VCV) Peak inspiratory pressure (PIP)- maximal pressure with inspiration. Sum of plateau pressure and pressure required to overcome airway resistance. Keep <40 cm H2O, SCCM recommends below 30 for ARDS. Abnormalities: elevated PIP indicates high resistance (secretions, bronchospasm, biting tube). Plateau pressure= alveolar pressure. Mean pressure during end-inspiratory pause, basically when there is no air movement. Not affected by resistance. Goal ≤30 cm H2O. Abnormalities: elevated plateau pressure indicates poor compliance. Driving pressure= plateau - PEEP. Goal ≤15 cm H2O (>15 is associated with ↑mortality). PEEP can either improve or worsen driving pressure. If the set PEEP promotes recruitment→ ↓driving pressure. If the set PEEP creates overdistension of the alveoli→ ↑driving pressure. End Expiratory Pressure Positive end expiratory pressure (PEEP)- lowest pressure that avoids alveolar collapse, which occurs when intrapleural pressure is higher than intra-alveolar pressure. This is indicated by the lower bend on the pressure/ volume curve, known as the lower inflection point. Mean Airway Pressure Mean airway pressure (MAP)- average pressure the lungs are exposed to during the breathing cycle. One of the two parameters that determine oxygenation. - How to increase MAP: ↑PEEP. If using IRV, ↑inspiratory time (Thigh) and ↑inspiratory pressure (Phigh). Parameters that Impact Airway Pressures Resistance- change in pressure relative to flow (PIP - plateau/ peak inspiratory flow). Relationship between PIP and plateau is directly related to airway resistance. ↑PIP and [PIP - plateau >5 cmH2O]= ↑resistance (bronchospasm, ETT obstruction/ kink). ↑PIP and ↑plateau [PIP - plateau <5 cmH2O]= ↓compliance (PTX, ARDS, pneumonia, edema, auto-PEEP). Compliance- change in volume per change in pressure. Normal- 50-100 mL/ cm H2O Previous Next

< Back Vent Mgmt #1: Basics The goal of ventilatory support is to maintain appropriate O2 and CO2 in the blood while offloading the work of the respiratory muscles and minimizing iatrogenic lung damage. Understanding this principle will help guide your ventilator management. Many variables can be manipulated on the ventilator, but there are a few key variables that truly control oxygenation and ventilation. While there is not one ideal setting for every scenario, there are a few basic principles that cover the majority of ventilator management. Basic Ventilator Settings First, it is important to understand what the ventilator does. The ventilator can push air into patients. You can control how much air is pushed in (tidal volume), the number of breaths per minute (respiratory rate, RR), and the concentration of oxygen molecules in the air itself (fraction of inspired oxygen, FiO2). It's also possible to control how quickly air is pushed in (flow)- but we will get to that later. It is important to note: the ventilator does NOT generate pressure- it only monitors pressure to prevent damage from elevated pressures (barotrauma). Breathing is controlled by three variables. Trigger- this determines when a breath starts. Either time, flow, or pressure. Time trigger is utilized when the patient is not generating any spontaneous breathing (ie mandatory breaths). Flow and pressure triggers are utilized if the patient has spontaneous respiratory activity. When the patient attempts to inhale, there is a change in flow and/ or pressure. This is sensed by the ventilator, and a breath is delivered. Limit- this sets the maximum value a parameter can reach during a breath. For example, volume-limited indicates that a breath can't exceed a certain max mL and pressure-limited indicates that the pressure monitored by the machine can't exceed a certain max cm H2O. For a graphic representation, please refer to the image in the section on Limit Variables in Deranged Physiology. Limits impact the shape of the waveform. Volume limited- flow ceases when the set/ target volume is delivered. Pressure limited- a large portion of the TV delivered at the beginning of the breath until the set/ target pressure is reached and then the flow tapers, slowly delivering the remainder of the volume until the breath is time or flow cycled (see next) Cycle- this determines the end of a breath. Time cycled- inspiration ceases at the end of a set time duration. Used in mandatory breaths. Flow cycled- inspiration ceases when flow drops below a certain level. Used in spontaneous breaths. Volume and pressure are not currently used to cycle breaths. The goals of mechanical ventilatory support are O2 delivery (oxygenation) and CO2 removal (ventilation). Effective oxygenation and ventilation are measured by an arterial blood gas- PaO2 indicates the partial pressure of O2 and PaCO2 indicates the partial pressure of CO2. Oxygenation is a function of the concentration of O2 delivered to the patient (fraction of inspired O2, FiO2) and the surface available for O2 exchange. Positive pressure maintains open airways, which maintains the surface available for O2 exchange. Mean airway pressure (MAP) is the parameter that indicates the average pressure measured in the lungs throughout inspiration (inspiratory pressure) and expiration (positive end expiratory pressure, PEEP). Expiration is usually 2-3 times longer than inspiration, so MAP is often simplified to PEEP when trying to optimize oxygenation. However, increasing inspiratory time can improve MAP without adjusting PEEP. Ventilation is controlled by minute ventilation (total volume of air exchanged every minute). Minute ventilation is respiratory rate multiplied by tidal volume. Therefore, respiratory rate (RR) and tidal volume (TV) are the two parameters that can optimize ventilation. Lung-Protective Ventilation Minimizing iatrogenic lung injury is also important when caring for patients receiving ventilatory support. Different types of trauma, including barotrauma (excess pressure), volutrauma (excess volume), and atelectrauma (repetitive opening and closing of alveoli), can damage lungs that are already diseased. The risk of barotrauma can be minimized by monitoring airway pressures (peak and plateau pressures). Volutrauma can be minimized by low tidal volume. Historically, larger tidal volumes were standard (10-12 mL/kg). Currently, the most commonly recommended volume is 6-8 mL/kg (there are some exceptions). Decreased TV leads to ↓minute ventilation and ↓CO2 clearance (↑PaCO2). This is the basic physiologic principle behind "permissive hypercapnia" during mechanical ventilation for ARDS. Atelectrauma can be minimized by maintaining PEEP, which keeps alveoli open. Additional References 1. Respiratory Therapy Pocket Reference Card Previous Next