- Email: [email protected]
Continuous flow positive airway pressure generator in critically ill patients
Correspondence
device errors may still occur no matter what administration system is in place. We also suggest that calcium is readily available in locations where magnesium is administered and that all staff are familiar with the management of acute magnesium toxicity. N. J. McDonnell Subiaco, Australia E-mail: [email protected] 1 McDonnell NJ. Cardiopulmonary arrest in pregnancy: two case reports of successful outcomes in association with perimortem Caesarean delivery. Br J Anaesth 2009; 103: 406– 9 2 James MFM. Magnesium: an emerging drug in anaesthesia. Br J Anaesth 2009; 103:465 – 7 3 Jee D-L, Lee D-H, Yun S-S, Lee C-H. Magnesium sulphate attenuates arterial blood pressure increase during laparoscopic cholecystectomy. Br J Anaesth 2009; 103: 484 – 9 doi:10.1093/bja/aep349
Continuous flow positive airway pressure generator in critically ill patients A recent article by Glover and Fletcher1 assessed the performance of a continuous flow positive airway pressure generator (Whisperflow; Philips Respironics) which was bench-tested under dynamic conditions that simulated many clinical circumstances. We have also assessed the performance of two continuous flow positive airway pressure generators (Adjustable Downs Flow Generator-Vital Signs and the same Whisperflow).2 We also found a poor performance of the Whisperflow generator under dynamic conditions, especially when those conditions were more demanding. In view of the above studies and the considerations below, we believe that the use of such generators is unjustifiable. Besides the underperformance of the Whisperflow generator, there are some other reasons that should preclude the use of continuous flow positive airway pressure generators in critically ill patients. In our country (Brazil), simple turbine-driven CPAP machines have similar acquisition cost to flow generators. Even if this does not apply worldwide, the increased cost of a preventable adverse event would wreck the economic argument.3 In our experience, the noise of generators is high enough to bother patients and intensive care unit staff, with probable negative impact in patients’ sleep4 and delirium. A recent study measured the noise of two CPAP systems (including Whisperflow) and it reached more than 90 dB depending on the interface5 (similar to a food blender at 1 m distance). In addition, continuous flow generators do not offer indispensable alarms and monitoring. As these two studies1 2 have demonstrated, the number of possible factors that can be adjusted in a continuous flow generator (fraction of O2, pipeline supply, valve load,
and flow adjustment) makes the performance excessively variable and unpredictable. We fully agree with Glover and Fletcher that further in vivo data are required, but due to the low efficacy and serious concerns about safety, we believe that we should consider a moratorium on the use of continuous positive airway pressure flow generators in critically ill patients. P. Caruso* C. Fu C. R. Ribeiro de Carvalho Sao Paulo, Brazil *E-mail: [email protected]
Editor—We are grateful to Caruso and colleagues for their interest in our paper.1 They present persuasive arguments against the use of continuous high-flow CPAP generators (HFCPAP) in the critically ill, specifically the Whisperflow (Philips Respironics). As demonstrated by both our and Caruso’s studies, the in vitro performance of this device is sub-optimal.1 2 Furthermore, there are clinical data indicating that CPAP in general may increase work of breathing and worsen outcome in hypoxaemic respiratory failure.6 7 While we are inclined to agree with Caruso’s proposal for a moratorium on the use of the Whisperflow and similar devices, we must carefully consider the possible consequences. In the UK, the use of HFCPAP systems is widespread and indeed the Whisperflow is being promoted for prehospital use. Use is often by non-intensivist physicians and therapists in patients with a wide range of causes of respiratory failure. The Whisperflow is used on the basis of low cost, simplicity and in the belief that it is effective and suitable for use by those without advanced critical care training and sometimes without close monitoring. If we prohibit this kind of use, then demand for ‘formal’ critical care support will increase in an unsustainable fashion. Conversely, it could be argued that the usage of non-invasive ventilatory support outside the critical care unit has always been inappropriate and has arisen because of resource limitations. Non-invasive respiratory support has been one of the great advances in critical care, and yet it must be used with care. As with any device, it is vital that the user is fully aware of the limitations of the technology. Currently, this is not the case. This is largely because formal evaluation of these devices before marketing is not mandatory. It is only now through the work of Caruso, ourselves, and others that we are beginning to understand the performance of HFCPAP generators. The next generation of work must look at the patient’s respiratory support requirements also. This is a largely neglected area of study.
116
Correspondence
The ultimate question is whether HFCPAP devices like the Whisperflow are better than nothing at all. We do not know the answer to this question. Therefore, we advocate caution in the use of the Whisperflow and other HFCPAP devices, rather than, at this stage, an outright hospital-wide ban. However, in our intensive care unit, with the availability of more sophisticated ventilators that provide noninvasive ventilation, along with appropriate monitoring, the Whisperflow is to be phased out. It is now incumbent on manufacturers to adequately assess existing and new products to ensure that they are fit for purpose. It is also incumbent on specialist societies and regulatory bodies such as the UK National Institute for Clinical Excellence to take a view on the use of these devices. S. J. Fletcher* G. W. Glover Bradford, UK *E-mail: [email protected] 1 Glover GW, Fletcher SJ. Assessing the performance of the Whisperflow continuous positive airway pressure generator: a bench study. Br J Anaesth 2009; 102: 875 – 81 2 Fu C, Caruso P, Lucatto JJ, et al. Comparison of two flow generators with a noninvasive ventilator to deliver continuous positive airway pressure: a test lung study. Intensive Care Med 2005; 31: 1587 – 92 3 Kaushal R, Bates DW, Franz C, Soukup JR, Rothschild JM. Costs of adverse events in intensive care units. Crit Care Med 2007; 35: 2479 – 83 4 Gabor JY, Cooper AB, Crombach SA, et al. Contribution of the intensive care unit environment to sleep disruption in mechanically ventilated patients and healthy subjects. Am J Respir Crit Care Med 2003; 167: 708 –15 5 Cavaliere F, Conti G, Costa R, et al. Exposure to noise during continuous positive airway pressure: influence of interfaces and delivery systems. Acta Anaesthesiol Scand 2008; 52: 52 – 6 6 L’Her E, Deye N, Lellouche F, et al. Physiologic effects of noninvasive ventilation during acute lung injury. Am J Respir Crit Care Med 2005; 172: 1112 – 8 7 Declaux C, L’Her E, Alberti C, et al. Treatment of acute hypoxaemic nonhypercapnic respiratory insufficiency with continuous positive airway pressure delivered by a face mask: a randomised controlled trial. J Am Med Assoc 2000; 284: 2352 – 60
elongation and correction of deformities in the lower limb.1 2 Surgical correction of deformities of lower limb alignment is highly invasive, and requires good anaesthetic management both during the surgery and for postoperative pain. We report the case of a patient undergoing corrective surgery by using the MAC fixation system for epiphysiolysis of the femoral head, performed under general anaesthesia combined with sciatic and femoral nerve blocks. A 15-yr-old (69 kg) male was undergoing osteotomy and placement of MAC fixation system due to shortening and varus deviation of his right knee (Fig. 1). As a result of distal epiphysiolysis in both femurs at 4 yr old, he had had several major orthopaedic procedures, including (age 11 yr) osteotomy for varus correction using an external fixator with lengthening adapter. The patient was premedicated with oral midazolam 0.5 mg kg21, 90 min before surgery. In the operating theatre, in addition to the standard monitoring, bispectral index, oesophageal temperature, and neuromuscular function were monitored. Body temperature was maintained between 358C and 368C. The patient received oxygen 100% for 3 min. Anaesthetic induction was performed with atropine 0.01 mg kg21, propofol 2 mg kg21, and mivacurium 0.2 mg kg21 and a laryngeal mask number 4 (Supremew) was inserted. Anaesthesia was maintained with oxygen and air (FIO2 0.5), expired sevoflurane 1.5%, and remifentanil 0.2– 0.3 mg kg21 min21 in the 40– 60 BIS range. Femoral and sciatic nerve blocks were performed using the anterior approach with ultrasound guidance (Sonosite S-Nervew), and bupivacaine 0.25% (50 mg) used for each nerve block. In addition, a catheter was placed with stimulation device (Arroww) at the femoral nerve with continuous infusion system of bupivacaine 0.125% (7 ml h21) for treatment of postoperative pain. The surgery lasted 150 min and was uneventful. The patient’s postoperative course was satisfactory, with adequate pain control with continuous infusion of bupivacaine and acetaminophen 1 g i.v. as rescue analgesia. Maximum
doi:10.1093/bja/aep350
Anaesthetic management of a patient for femoral correction using a new multi-axial fixation system Editor—Multi-axial correction (MAC) monolateral external fixation system (Biomet, Parsippany, NJ, USA) is a non-circular fixator that was developed as a response to the difficulties, for both patients and physicians, of placing, managing, and tolerating a circular fixator, in
Fig 1 MAC fixation system in right femur for correction of the knee with varus deviation.
117
Copyright of BJA: The British Journal of Anaesthesia is the property of Oxford University Press / UK and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
device errors may still occur no matter what administration system is in place. We also suggest that calcium is readily available in locations where magnesium is administered and that all staff are familiar with the management of acute magnesium toxicity. N. J. McDonnell Subiaco, Australia E-mail: [email protected] 1 McDonnell NJ. Cardiopulmonary arrest in pregnancy: two case reports of successful outcomes in association with perimortem Caesarean delivery. Br J Anaesth 2009; 103: 406– 9 2 James MFM. Magnesium: an emerging drug in anaesthesia. Br J Anaesth 2009; 103:465 – 7 3 Jee D-L, Lee D-H, Yun S-S, Lee C-H. Magnesium sulphate attenuates arterial blood pressure increase during laparoscopic cholecystectomy. Br J Anaesth 2009; 103: 484 – 9 doi:10.1093/bja/aep349
Continuous flow positive airway pressure generator in critically ill patients A recent article by Glover and Fletcher1 assessed the performance of a continuous flow positive airway pressure generator (Whisperflow; Philips Respironics) which was bench-tested under dynamic conditions that simulated many clinical circumstances. We have also assessed the performance of two continuous flow positive airway pressure generators (Adjustable Downs Flow Generator-Vital Signs and the same Whisperflow).2 We also found a poor performance of the Whisperflow generator under dynamic conditions, especially when those conditions were more demanding. In view of the above studies and the considerations below, we believe that the use of such generators is unjustifiable. Besides the underperformance of the Whisperflow generator, there are some other reasons that should preclude the use of continuous flow positive airway pressure generators in critically ill patients. In our country (Brazil), simple turbine-driven CPAP machines have similar acquisition cost to flow generators. Even if this does not apply worldwide, the increased cost of a preventable adverse event would wreck the economic argument.3 In our experience, the noise of generators is high enough to bother patients and intensive care unit staff, with probable negative impact in patients’ sleep4 and delirium. A recent study measured the noise of two CPAP systems (including Whisperflow) and it reached more than 90 dB depending on the interface5 (similar to a food blender at 1 m distance). In addition, continuous flow generators do not offer indispensable alarms and monitoring. As these two studies1 2 have demonstrated, the number of possible factors that can be adjusted in a continuous flow generator (fraction of O2, pipeline supply, valve load,
and flow adjustment) makes the performance excessively variable and unpredictable. We fully agree with Glover and Fletcher that further in vivo data are required, but due to the low efficacy and serious concerns about safety, we believe that we should consider a moratorium on the use of continuous positive airway pressure flow generators in critically ill patients. P. Caruso* C. Fu C. R. Ribeiro de Carvalho Sao Paulo, Brazil *E-mail: [email protected]
Editor—We are grateful to Caruso and colleagues for their interest in our paper.1 They present persuasive arguments against the use of continuous high-flow CPAP generators (HFCPAP) in the critically ill, specifically the Whisperflow (Philips Respironics). As demonstrated by both our and Caruso’s studies, the in vitro performance of this device is sub-optimal.1 2 Furthermore, there are clinical data indicating that CPAP in general may increase work of breathing and worsen outcome in hypoxaemic respiratory failure.6 7 While we are inclined to agree with Caruso’s proposal for a moratorium on the use of the Whisperflow and similar devices, we must carefully consider the possible consequences. In the UK, the use of HFCPAP systems is widespread and indeed the Whisperflow is being promoted for prehospital use. Use is often by non-intensivist physicians and therapists in patients with a wide range of causes of respiratory failure. The Whisperflow is used on the basis of low cost, simplicity and in the belief that it is effective and suitable for use by those without advanced critical care training and sometimes without close monitoring. If we prohibit this kind of use, then demand for ‘formal’ critical care support will increase in an unsustainable fashion. Conversely, it could be argued that the usage of non-invasive ventilatory support outside the critical care unit has always been inappropriate and has arisen because of resource limitations. Non-invasive respiratory support has been one of the great advances in critical care, and yet it must be used with care. As with any device, it is vital that the user is fully aware of the limitations of the technology. Currently, this is not the case. This is largely because formal evaluation of these devices before marketing is not mandatory. It is only now through the work of Caruso, ourselves, and others that we are beginning to understand the performance of HFCPAP generators. The next generation of work must look at the patient’s respiratory support requirements also. This is a largely neglected area of study.
116
Correspondence
The ultimate question is whether HFCPAP devices like the Whisperflow are better than nothing at all. We do not know the answer to this question. Therefore, we advocate caution in the use of the Whisperflow and other HFCPAP devices, rather than, at this stage, an outright hospital-wide ban. However, in our intensive care unit, with the availability of more sophisticated ventilators that provide noninvasive ventilation, along with appropriate monitoring, the Whisperflow is to be phased out. It is now incumbent on manufacturers to adequately assess existing and new products to ensure that they are fit for purpose. It is also incumbent on specialist societies and regulatory bodies such as the UK National Institute for Clinical Excellence to take a view on the use of these devices. S. J. Fletcher* G. W. Glover Bradford, UK *E-mail: [email protected] 1 Glover GW, Fletcher SJ. Assessing the performance of the Whisperflow continuous positive airway pressure generator: a bench study. Br J Anaesth 2009; 102: 875 – 81 2 Fu C, Caruso P, Lucatto JJ, et al. Comparison of two flow generators with a noninvasive ventilator to deliver continuous positive airway pressure: a test lung study. Intensive Care Med 2005; 31: 1587 – 92 3 Kaushal R, Bates DW, Franz C, Soukup JR, Rothschild JM. Costs of adverse events in intensive care units. Crit Care Med 2007; 35: 2479 – 83 4 Gabor JY, Cooper AB, Crombach SA, et al. Contribution of the intensive care unit environment to sleep disruption in mechanically ventilated patients and healthy subjects. Am J Respir Crit Care Med 2003; 167: 708 –15 5 Cavaliere F, Conti G, Costa R, et al. Exposure to noise during continuous positive airway pressure: influence of interfaces and delivery systems. Acta Anaesthesiol Scand 2008; 52: 52 – 6 6 L’Her E, Deye N, Lellouche F, et al. Physiologic effects of noninvasive ventilation during acute lung injury. Am J Respir Crit Care Med 2005; 172: 1112 – 8 7 Declaux C, L’Her E, Alberti C, et al. Treatment of acute hypoxaemic nonhypercapnic respiratory insufficiency with continuous positive airway pressure delivered by a face mask: a randomised controlled trial. J Am Med Assoc 2000; 284: 2352 – 60
elongation and correction of deformities in the lower limb.1 2 Surgical correction of deformities of lower limb alignment is highly invasive, and requires good anaesthetic management both during the surgery and for postoperative pain. We report the case of a patient undergoing corrective surgery by using the MAC fixation system for epiphysiolysis of the femoral head, performed under general anaesthesia combined with sciatic and femoral nerve blocks. A 15-yr-old (69 kg) male was undergoing osteotomy and placement of MAC fixation system due to shortening and varus deviation of his right knee (Fig. 1). As a result of distal epiphysiolysis in both femurs at 4 yr old, he had had several major orthopaedic procedures, including (age 11 yr) osteotomy for varus correction using an external fixator with lengthening adapter. The patient was premedicated with oral midazolam 0.5 mg kg21, 90 min before surgery. In the operating theatre, in addition to the standard monitoring, bispectral index, oesophageal temperature, and neuromuscular function were monitored. Body temperature was maintained between 358C and 368C. The patient received oxygen 100% for 3 min. Anaesthetic induction was performed with atropine 0.01 mg kg21, propofol 2 mg kg21, and mivacurium 0.2 mg kg21 and a laryngeal mask number 4 (Supremew) was inserted. Anaesthesia was maintained with oxygen and air (FIO2 0.5), expired sevoflurane 1.5%, and remifentanil 0.2– 0.3 mg kg21 min21 in the 40– 60 BIS range. Femoral and sciatic nerve blocks were performed using the anterior approach with ultrasound guidance (Sonosite S-Nervew), and bupivacaine 0.25% (50 mg) used for each nerve block. In addition, a catheter was placed with stimulation device (Arroww) at the femoral nerve with continuous infusion system of bupivacaine 0.125% (7 ml h21) for treatment of postoperative pain. The surgery lasted 150 min and was uneventful. The patient’s postoperative course was satisfactory, with adequate pain control with continuous infusion of bupivacaine and acetaminophen 1 g i.v. as rescue analgesia. Maximum
doi:10.1093/bja/aep350
Anaesthetic management of a patient for femoral correction using a new multi-axial fixation system Editor—Multi-axial correction (MAC) monolateral external fixation system (Biomet, Parsippany, NJ, USA) is a non-circular fixator that was developed as a response to the difficulties, for both patients and physicians, of placing, managing, and tolerating a circular fixator, in
Fig 1 MAC fixation system in right femur for correction of the knee with varus deviation.
117
Copyright of BJA: The British Journal of Anaesthesia is the property of Oxford University Press / UK and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.