Arguably, airway management is one of the most important interventions provided by emergency medical service personnel. Despite the allegiance to endotracheal intubation as a gold standard of airway control, endotracheal tube placement during acute exacerbation of various respiratory conditions comes with a significant increase in complications and mortality (Keenan, Sinuff, Cook, & Hill, 2004). Alternative airway control strategies such as non-invasive positive-pressure ventilation (NPPV) may be beneficial in some cases.
Two different types of NPPV are currently available. Bilevel positive airway pressure (BiPAP) increases the pressure during inspiration and decreases it during expiration. Continuous positive airway pressure (CPAP) provides a constant level of positive pressure during inspiration and expiration.
CPAP reduces the work of breathing, reinflates collapsed alveoli and improves pulmonary compliance. CPAP provides additional benefits to patients suffering from the acute effects of cardiogenic pulmonary edema by reducing both the preload and afterload, thereby improving the body’s hemodynamics.
CPAP reduces intubation risk in the ED setting
In 1998, a systematic review of emergency department (ED) administered CPAP via face mask found a 26% absolute risk difference in the need for intubation while caring for patients suffering from cardiogenic pulmonary edema with respiratory distress compared to standard therapy alone (Pang, Keenan, Cook, & Sibbald, 1998). A follow-up review conducted in 2006 found that ED personnel utilizing non-invasive positive pressure ventilation (NPPV) could decrease the relative risk of mortality by 39% while simultaneously decreasing the need for endotracheal intubation by 57% in patients with similar signs and symptoms (Collins et al., 2006). To date, there is no strong evidence demonstrating the superiority of one strategy over the other.
What is the utility of prehospital CPAP?
On the other hand, prehospital data on the utility of CPAP orBiPAP is less clear. . A retrospective review of patients treated by Helsinki EMS for respiratory distress found significant improvements in the patient’s hemodynamic and respiratory variables when treated in the field with CPAP (Kallio, Kuisma, Alaspää, & Rosenberg, 2003). Using a non-randomized control group design, researchers utilizing two-separate EMS agencies found an absolute risk reduction of 16% for intubation and 18% for death when using CPAP (Hubble, Richards, Jarvis, Millikan, & Young, 2006).
However, after introducing a CPAP protocol, researchers in San Diego could not demonstrate a reduction in the need for emergency department intubation, ICU admission or survival to discharge for patients suffering from severe respiratory distress when compared to historical controls (Aguilar et al., 2013). Despite observed improvement in physiologic parameters such as blood pressure, pulse rate, respiratory rate and pulse oximetry values, prehospital researchers in Canada could not demonstrate significant differences in intubation rates or mortality in patients suffering from acute respiratory emergencies after introducing CPAP (Cheskes, Turner, Thomson, & Aljerian, 2013).
Failure to demonstrate improved intubation rates or mortality persisted even after controlling for confirmed in-hospital diagnosis of pulmonary edema, CHF, COPD, and patient acuity. The Canadian results are similar to the results of a multi-center randomized controlled trial conducted in the United Kingdom (Gray et al., 2008).
A meta-analysis suggests the lack of compelling data for mortality reduction associated with prehospital non-invasive ventilation may be the result of research limitations rather than a true absence of benefit (Simpson & Bendall, 2011).
CPAP and low levels of oxygenation
In response to the growing concerns about the deleterious effects of hyperoxygenation, researchers in Nevada recently examined the use of CPAP powered by low fractional oxygen concentrations (Bledsoe et al., 2012). Paramedics provided CPAP at a pressure of 10 cmH2O using 28% to 30% oxygen concentration to all adult patients complaining of respiratory distress secondary to asthma, COPD, CHF and/or pneumonia. Although most prehospital CPAP relies on 100% oxygen concentrations, the lowered concentration used in this investigation resulted in significantly improved respiratory rate and oxygen saturation values over baseline. In addition, more that 70% of the patients subjectively reported symptom improvement.
CPAP and drowning
CPAP also has applicability to patients who suffer near fatal drowning episodes. The hypoxemia associated with submersion incidents results from a combination of ventilation-perfusion mismatch and intrapulmonary shunting (Dottorini, Eslami, Baglioni, Fiorenzano, & Todisco, 1996). The single treatment most effective at reversing hypoxemia from either fresh or salt-water drowning is application of CPAP (Modell, 1993).
Using CPAP in managing respiratory distress
Management of patients suffering from respiratory distress begins by providing ventilatory support. This support ranges in complexity from simple oxygen administration to advanced airway maneuvers, depending upon the clinical condition of the patient. Patients who do not respond to simple therapy will require a more aggressive strategy.
In the event that the patient requires the use of NPPV, there are a few important points to remember that may be beneficial for both you and your patient. Before applying CPAP, explain the procedure to the patient. In many cases, patients requiring the use of CPAP will be in an excited state and may believe they are suffocating. Placing a pressurized mask on their face can add to their stress level. To help reduce the anxiety level, allow the patients who can cooperate with your therapy to self-administer until they become acclimated to the device.
Set the initial CPAP pressure low and verify that the delivery mask does not have any leaks. Allow the patient to hold the delivery assembly and instruct them to self-administer. If the patient cannot, the rescuer will need to create a seal between the delivery mask and the patient’s mouth and nose. Coach the patient to take several breaths and, if necessary, remove the mask from the patient’s face for a few seconds before reapplying. Gradually increase the amount of time the patient is breathing against the CPAP. Once the patient can tolerate the device, secure the mask to the patient’s face.
Monitor and document the patient’s respiratory response to the treatment. Most patients will have noticeable improvement in oxygenation with minutes. Continue to coach patient to keep the mask in place and re-adjust as needed. If respiratory status deteriorates, or if no improvement is observed within this time, remove the device and provide BVM ventilation with or without endotracheal intubation.
Summary
Respiratory distress is a common and often life-threatening prehospital presentation. Critical to their survival is command of the patient’s airway. CPAP is emerging as one of the most effective methods of quickly relieving the distress, preventing the need for endotracheal intubation, and reducing morbidity and mortality in patients suffering from a variety of respiratory pathologies.
References
Aguilar, S. A., Lee, J., Castillo, E., Lam, B., Choy, J., Patel, E., Pringle, J., & Serra, J. (2013). Assessment of the addition of prehospital continuous positive airway pressure (CPAP) to an urban emergency medical services (EMS) system in persons with severe respiratory distress. Journal of Emergency Medicine, 45(2), 210-219. doi:10.1016/j.jemermed.2013.01.044
Bledsoe, B. E., Anderson, E., Hodnick, R., Johnson, L., Johnson, S., & Dievendorf, E. (2012). Low-fractional oxygen concentration continuous positive airway pressure is effective in the prehospital setting. Prehospital Emergency Care, 16(2), 217-221. doi:10.3109/10903127.2011.640765
Cheskes, S., Turner, L., Thomson, S., & Aljerian, N. (2013). The impact of prehospital continuous positive airway pressure on the rate of intubation and mortality from acute out-of-hospital respiratory emergencies. Prehospital Emergency Care, 17(4), 435-441. doi:10.3109/10903127.2013.804138
Collins, S. P., Mielniczuk, L. M., Whittingham, H. A., Boseley, M. E., Schramm, D. R., & Storrow, A. B. (2006). The use of noninvasive ventilation in emergency department patients with acute cardiogenic pulmonary edema: A systematic review. Annals of Emergency Medicine, 48(3), 260–269.
Dottorini, M., Eslami, A., Baglioni, S., Fiorenzano, G., & Todisco, T. (1996). Nasal-continuous positive airway pressure in the treatment of near-drowning in freshwater. Chest, 110(4), 1122-1124.
Gray, A., Goodacre, S., Newby, D. E., Masson, M., Sampson, F., Nicholl, J., & the 3CPO Trialists. (2008). Noninvasive ventilation in acute cardiogenic pulmonary edema. New England Journal of Medicine, 359(2), 142–151. doi:10.1056/NEJMoa0707992
Hubble, M. W., Richards, M. E., Jarvis, R., Millikan, T., & Young, D. (2006). Effectiveness of prehospital continuous positive airway pressure in the management of acute pulmonary edema. Prehospital Emergency Care, 10(4), 430–439. doi: 10.1080/10903120600884848
Kallio, T., Kuisma, M., Alaspää, A., & Rosenberg, P. H. (2003). The use of prehospital continuous positive airway pressure treatment in presumed acute severe pulmonary edema. Prehospital Emergency Care, 7(2), 209–213.
Keenan, S. P., Sinuff, T., Cook, D. J., & Hill, N. S. (2004). Does noninvasive positive pressure ventilation improve outcome in acute hypoxemic respiratory failure? A systematic review. Critical Care Medicine, 32(12), 2516-2523. doi:10.1097/01.CCM.0000148011.51681.E2
Modell, J. H. (1993). Drowning. New England Journal of Medicine, 328(4), 253-262
Pang, D., Keenan, S. P., Cook, D. J., & Sibbald, W. J. (1998). The effect of positive airway pressure support on mortality and the need for intubation in acute cardiogenic pulmonary edema: A systematic review. Chest, 114(4), 1185–1192. doi:10.1378/chest.114.4.1185
Simpson, P. M., & Bendall, J. C. (2011). Prehospital non-invasive ventilation for acute cardiogenic pulmonary oedema: An evidence-based review. Emergency Medicine Journal, 28(7), 609–612. doi: 10.1136/emj.2010.092296
