HFOV Case Study 14 year old Instructor Copy Color key: Black Patient case Blue RN/RCP collaboration Red MD consult Green - Critical Thinking Inquiry Green italics CT answers ABG format: ph/pco2/po2/base A 14-year-old female is admitted with a decreased level of consciousness and abdominal bleeding. She also complains of abdominal pain, diaphoresis, and cramping in the left upper quadrant and periumbilical area. A diagnostic laparoscopy is performed, noting copious bleeding from a hemorrhagic cyst. She experiences hypotension and a decreased hemoglobin and hematocrit. Packed red blood cells are transfused. After fluid and blood resuscitation, an exploratory laparotomy is performed. A 2000ml hemoperitoneum with a small amount of bleeding from the right ovary is discovered. ABG: 7.32/52/68/26 on room air CT: What is happening with the above ABGs? This blood gas indicates a potential for respiratory failure. The CO2 level is higher than normal without any form of compensation. This is an acute event. This patient is intubated to protect her airway. Because of the potential for respiratory failure, it is preferable to intubate as an elective procedure, rather than as an emergency measure during an arrest situation. This patient has a great risk for hemorrhagic shock because of the amount of blood loss from the cyst. Close monitoring of the hematocrit and hemoglobin is important. In addition, it may be necessary to place an arterial catheter for continuous blood pressure monitoring and laboratory draws. PRVC: volume ventilation with minimal pressures FIO2 1.0 Vt 350ml Rate 20 ABG: 7.47/31/54/22/+1.0 CT: Is this a ventilation or an oxygenation problem? Clearly oxygenation MD called to bedside. HFOV is initiated CT: Why the need for HFOV at this stage? Need to minimize the insult to the lungs and try to recruit more alveoli and improve oxygenation What would be appropriate settings? Initial ventilator settings would be FiO2 100%, Hz 6.0, amp to ensure adequate CW, and MAP 35 (5 above CMV MAP). The amp setting is set just high enough to cause a wiggle from the nipple line to the groin. ABG: 7.32/48/203/25/-1.5. 1 of 6
CT: What is the next move? The goal is to decrease the CO2. Increase the amplitude. Hyper-oxygenation is not necessary. Amplitude is increased and another ABG is drawn after one hour. ABG: 7.04/113/376/30/-4.8. RN/RCP: Discuss ABG and plan to suction. A chest x-ray is taken at this time and reveals rib expansion to the eighth rib. The patient is suctioned for a large amount of thick secretions. CT: What are some of the consequences of suctioning? Air trapping, loss of lung volume ABG: 7.13/93/225/+1.5 CT: What does this indicate between the CXR and the ABG? As the 8th rib is minimal expansion, and the CO2 is 93, the decision would be to either increase the amplitude or decrease the Hz. What determines which parameter is changed? Observe chest wiggle, if it past the groin, then decision would be to decrease the Hz to 5. This will allow a larger tidal volume. ABG: 7.16/66/314/23/-7.0. MD at bedside. He is asking your opinion on what to do next. CT: What changes would you make? Create a 5cm cuff leak so that CO2 can escape around the ETT, again, because of more than adequate CWF, decrease Hz to 4. Start decreasing the FIO2 first until you get around 50%, then can start decreasing the MAP ABG: 7.34/50/128/+1 CT: Were the changes above appropriate? Yes Over the next five days, the FiO2 and the MAP are weaned gradually. CT: When would be an appropriate time to switch to conventional ventilation? Why? The goal is to wean the mean airway pressure lower. When the mean airway pressure is about 5 cm H2O over where it was on conventional ventilation, it is time to change ventilation modes. The amplitude setting is another indicator that it is time to switch to conventional ventilation. As the patient recovers, the amplitude is weaned. This indicates that the lungs are healing and recovering. It is then time to change the mode of ventilation to a conventional mode. When the amplitude is weaned to a low number, such as 18 or 20, it also indicates it is time to change to conventional ventilation. When placing the patient back on conventional ventilation, the settings might be temporarily higher to allow the patient to compensate for the change in ventilator modes. Also can consider extubation. 2 of 6
References Bryan, A.C., Cox, P.N. (Oct 30, 1999). History of high frequency ventilation. Schweiz Med Wochenschr. 129(43):1613-6. Eichenwald, E.C., Stark, A.R. (Dec, 1999). High frequency ventilation: Current Status. Pediatric Review. 20(12):e127-33. Lai, M.K., Jeng, M.J. et al. (Dec 1999). High frequency oscillatory ventilation in premature infants. Chung Hua I Hsuen Tsa Chin (Taipei). 62(12):879-85. Morris, K. (Jan, 2000). Acute hypoxemic respiratory failure in children. Intensive Care Medicine. 26(1):109-16. Watkins, S.J., Peters, M.J., Tasker, R.C. (Jan-Feb, 2000). One hundred courses in high frequency ventilation: What have we learned? European Journal of Pediatrics. 159(1-2):134. Surfactant was administered at this time 100ml/kg ABG: 7.49/23/44/-3.2 tcco2 30 O2 SAT: 80% RN/RCP: discuss sat goals for patient, assess breath sounds, markedly diminished bilaterally MD called: Rate 50, FIO2 0.7 CT: Response to vent order What is VT? What is the optimum lung inflation? 8 ribs, hyperventilated,? lung injury??? 2000 CMV: PIP 20 PEEP 5 Rate 40 IT 0.4 FIO2 0.7 tcco2 70 O2 SAT 60% RN/RCP: Discuss possibilities of sudden change in vital signs MD called to bedside CT: Possible diagnosis? Tension pneumothorax 2015 CXR: Right sided Pneumothorax 2025 One chest tube placed. Four hours later, the patient developed acute distress requiring chest compressions, IV sodium bicarbonate and epinephrine was administered through the ETT. ABG: 7.0/65/27/-8 tcco2 80 O2SAT 56% CT: What s happening with this patient. Note the acute onset of the code and follow up ABG. Another Pneumothorax, acute respiratory acidosis 3 of 6
CXR: Left sided tension Pneumothorax that has partially re-expanded after chest tube placement. 2045 MD: Order for HFOV CT: What would be the appropriate initial HFOV settings? Why? Low lung volume strategy for air leak MAP should be 1-2cm lower than CMV MAP. AMP should be adjusted for adequate CWF (clavicles to umbilicus) Hz appropriate for patient weight What are potential complications of HFOV? Air trapping/hyperinflation/hemodynamic compromise What do we need before switching to HFOV? Vital Signs/Assessment Heightened awareness of safety and stable airway; positioning and immobility; firm mattress, suctioning, assess BP 2100 HFOV: FIO2 1.0 MAP13 Amp 20 Hz 15 CT: Response to HFOV? Assess CWF, Bp, O2 SAT, how is CWF assessed? 2210 CXR reveals changes consistent with pulmonary interstitial emphysema and bilateral pneumothoraces. 0100 ABG: 7.44/46/89/+1 tcco2 49 O2 SAT 91% RN/RCP discuss the need for suctioning MD: Wean FIO2 for sats <92%, adjust amp to keep PCO2 50 and for adequate CW CT: How long since surfactant was given? Refrain from suctioning up to four hours post dosing except for possible airway obstruction. What are potential adverse effects of suctioning pt. on HFOV? Loss of lung volume (especially if the baby does not return to baseline very quickly), atelectasis, ETT dislodgment Why is the FIO2 being weaned before the MAP? Oxygen toxicity 4 of 6
48 hours old: HFOV: FIO2 0.4 MAP 10 AMP 18 Hz 15 The patient was positioned with left side down because the air leak appeared on CXR to be worse there. Follow up CXR 12 hours later reflected dramatic improvement in the air leak and healing PIE. ABG: 7.46/41/80/+1 CT: What assessments are needed at this time? What ventilatory changes should be made? Decrease MAP by 1cm increments, decrease amp 2-5 cm increments Q1 hour, maintain Hz as long as CW is to umbilicus. 76 hours old: CXR indicated almost complete resolution of the air leak on the left side. HFOV continues to be weaned. CT: When do we start thinking about changing back to conventional ventilation? What vent settings would you choose? When the MAP is 10-15, amp is low, pt is stable and able to tolerate touch, suctioning, etc. Settings: FIO2 25% Rate 30 PIP 20 PEEP 4 IT 0.4 The use of a lower airway pressure with HFOV provided significant advantages for this patient. HFOV may be suggested not only to prevent, but also to resolve, air leak syndrome in neonatal patients with RDS. Perhaps the greatest lesson learned in HFOV research, to date, is the critical importance of proper ventilator-management strategy. Through their work with more than 400 critically ill neonates, Clark et al, 9 identified four categories of illness to be supported using HFOV: diffuse homogeneous lung disease, non-homogeneous lung disease, lung hypoplasia syndrome, and air leak syndrome. Based on their experience, they advocated the use of a low-pressure management strategy for patients with severe air leak. References 1. Varnholt V, Lasch P, Kachel W, Diehm T, Koelfen W. High frequency oscillatory ventilation of infants with severe respiratory disorders: possibilities, risks and limits. Klin Padiatr. 1994;206:161-166. 2. Miyahara K, Ichihara T, Watanabe T. Successful use of HFOV for pneumomediastinum. Ann Thorac Cardiovasc Surg. 1999;5:49-51. 3. Clark RH, Gertsmann DR. Controversies in high frequency ventilation: controversies in neonatal pulmonary care. Clin Perinatol. 1998;25:113-122. 4. Coalson JJ, delemos RA. Pathologic features of various ventilatory strategies. Acta Anaesthesiol Scand Suppl. 1989;90:108-116. 5. Helbich TH, Popow C, Dobner M, et al. New-born infants with severe hyaline membrane disease: radiological evaluation during high frequency oscillatory versus conventional ventilation. Eur J Radiol. 1998;28:243-249. 6. HiFO Study Group. Randomized study of high-frequency oscillatory ventilation in infants with severe respiratory distress syndrome. J Pediatr. 1993;122:609-619. 5 of 6
7. Boynton BR, Mannino FL, Davis RF, Kopotic RJ, Friederichsen G. Combined high-frequency oscillatory ventilation and intermittent mandatory ventilation in critically ill neonates. J Pediatr. 1984;105:297-303. 8. Gerstmann DR, Minton SD, Stoddard RA, et al. The Provo multicenter early high-frequency oscillatory ventilation trial: improved pulmonary and clinical outcome in respiratory distress syndrome. Pediatrics. 1996;98:1044-1057. 9. Clark RH, Gertsmann DR, Null DM, et al. Pulmonary interstitial emphysema treated with high frequency oscillatory ventilation. Crit Care Med. 1986;14:926-930. 10. delemos RA, Coalson JJ, delemos JA, King RJ, Clark RH, Gertsmann DR. Rescue ventilation with high frequency oscillation in premature baboons with hyaline membrane disease. Pediatr Pulmonol. 1992:12;29-36. 11. Minton SD. High-frequency oscillation using an inspiratory:expiratory ratio strategy of 1:2 decreased the incidence of air leak syndrome in infants with severe respiratory distress syndrome. N Engl J Med. 1989;320:88-90. 12. Kinsella JP, Parker TA, Galan H, et al. Independent and combined effects of inhaled nitric oxide, liquid perfluorochemical, and high frequency oscillatory ventilation in premature lambs with respiratory distress syndrome. Am J Respir Crit Care Med. 1999;159:1220-1227 Prepared by: Ruben D Restrepo, MD, RRT, is assistant professor, Cardiopulmonary Care Sciences Department, Georgia State University and PICU therapist, Children s Healthcare of Atlanta at Egleston, Atlanta; and Stephen Dickson, RRT, is a PICU therapist at Children s Healthcare of Atlanta at Egleston. These case studies are for reference only. Each patient is unique and may require different care. 6 of 6