Online Letter to the Editors
not have a true exhalation valve and uses a single-limb circuit. Single-circuit pressure-targeted ventilators provided with a calibrated leak (called “bilevel ventilators”) are most commonly used for NIV. For their trial, Roche Campo et al used valve-based ventilators. Several differences in technical performances of NIVD are largely reported. So, how these results Figure 1. Pathways for the horizontal transmission of Acinetobacter baumannii from a colonized/infected could be applied to all bilevel patient to a noncolonized patient. devices is not known (3). Third issue concerns type 4. Munoz-Price LS, Arheart KL, Mills JP, et al: Associations between bacof ventilator used in the prerandomization period. We lack for terial contamination of health care workers’ hands and contamination this information. Furthermore, three patients were not naïve of white coats and scrubs. Am J Infect Control 2012; 40:e245–e248 for NIV. It is well known that previous adaptation could influ 5. Munoz-Price LS, Quinn JP: Deconstructing the infection control bundles for the containment of carbapenem-resistant Enterobacteriaceae. ence efficacy of NIV, and this could lead to a bias (4). FurtherCurr Opin Infect Dis 2013; 26:378–387 more, the fact that the setting of ventilators was not different 6. Munoz-Price LS, Namias N, Cleary T, et al: Acinetobacter baumanin nighttime versus daytime sessions of NIV is not trivial as it nii: Association between environmental contamination of patient is well known that ventilatory needs largely change during the rooms and occupant status. Infect Control Hosp Epidemiol 2013; 34:517–520 sleep especially in patients with sleep-related syndromes (5). 7. Munoz-Price LS, Ariza-Heredia E, Adams S, et al: Use of UV powLeaks have neither measured nor estimated. They can affect der for surveillance to improve environmental cleaning. Infect Control trigger function by preventing the detection of patient inspiratory Hosp Epidemiol 2011; 32:283–285 effort but also delay switching into expiration. To limit this last 8. Munoz-Price LS, Fajardo-Aquino Y, Arheart KL: Ultraviolet powder versus ultraviolet gel for assessing environmental cleaning. Infect effect, it is important to set a maximal inspiratory time, a safety Control Hosp Epidemiol 2012; 33:192–195 feature to prevent unsuitable lengthening of inspiratory duration 9. Munoz-Price LS, Birnbach DJ, Lubarsky DA, et al: Decreasing (5). For case, the occurrence of that the authors called “prolonged operating room environmental pathogen contamination through improved cleaning practice. Infect Control Hosp Epidemiol 2012; cycle” only in NIVICU is probably a negative consequence of leaks 33:897–904 due to the impossibility to set a Timax in this device. DOI: 10.1097/CCM.0b013e3182a84bf7 Finally, a higher ineffective effort with NIVD is at least surprising. To limit the negative effects of leaks on trigger function, NIVD devices include sophisticated algorithms supposed Noninvasive Mechanical Ventilation and Sleep to improve trigger responses in front of leaks. So, we can expect Quality in ICU: Intensivists Are Waking Up! that these devices have a better response during leaks. More leakage in NIVD patients, trigger setted too insensitive or even To the Editor: an inadapted triggering response in this particular ventilator, leep in critically patients during noninvasive mechanical the presumable higher rate of obstructive sleep apnea in NIVD ventilation (NIV) is a growing topic (1). We read with patients are all possible explanations for this apparent paradox. great interest the article published by Córdoba-Izquierdo So, starting from this study, it is time to call for other bricks in et al (2) in a recent issue of Critical Care Medicine. Neverthe- the wall of “sleep and NIV in ICU.” less, some important questions need to be raised. The authors have disclosed that they do not have any potenFirst, due to some methodological bias of the study (greater tial conflicts of interest. amount of hours spent on NIV in nighttime with less sleep Antonio M. Esquinas, MD, PhD, FCCP, Intensive Care interferences, unavailable statistical power data, and lack of Unit and Non-Invasive Ventilation Unit, Hospital Morales crossover randomized design), unfortunately, we have no Meseguer, Murcia, Spain; Raffaele Scala, MD, Respiratory robust data to assert that sleep quality was better on NIV than Ward and Respiratory Intensive Care Unit, San Donato during unassisted breathing. Hospital, Arezzo, Italy; Claudio Rabec, MD, Service de Second, due to the huge heterogeneity of NIVICU and NIVD, Pneumologie et Réanimation Respiratoire, Centre Hospitalier et Universitaire de Dijon, Dijon, France the “take-home message” should be mitigated as these findings could not be applicable to all ventilators belonging to the two categories. For example, two different types of circuits can be REFERENCES used in NIVD. The first type uses a similar assembly to those 1. Roche Campo F, Drouot X, Thille AW, et al: Poor sleep quality is assoused in ICU devices in which inspiration and expiration are ciated with late noninvasive ventilation failure in patients with acute separated and an expiratory valve is present. A second type does hypercapnic respiratory failure. Crit Care Med 2010; 38:477–485
S
Critical Care Medicine
www.ccmjournal.org
e481
Online Letter to the Editors 2. Córdoba-Izquierdo A, Drouot X, Thille AW, et al: Sleep in Hypercapnic Critical Care Patients Under Noninvasive Ventilation: Conventional Versus Dedicated Ventilators. Crit Care Med 2013; 41:60–68 3. Pérel Jaillet A, Letellier C, Bounoiare D, et al: Evaluation de l’adaptation lors de la mise en route d’une ventilation non invasive (VNI). Rev Mal Resp 2011; 28:A5 4. Fanfulla F, Delmastro M, Berardinelli A, et al: Effects of different ventilator settings on sleep and inspiratory effort in patients with neuromuscular disease. Am J Respir Crit Care Med 2005; 172:619–624 5. Rabec C, Rodenstein D, Leger P, et al; SomnoNIV Group: Ventilator modes and settings during non-invasive ventilation: Effects on respiratory events and implications for their identification. Thorax 2011; 66:170–178 DOI: 10.1097/CCM.0b013e3182a5258f
The authors reply:
W
e thank Esquinas et al (1) for their comments and the opportunity to clarify a number of points from our work. One of the most interesting findings of our study was that patients could sleep during noninvasive ventilation (NIV) because no data concerning sleep quality of critical care patients under NIV existed before. However, the better sleep quality during NIV compared with unassisted breathing needs to be considered cautiously regarding all the limitations that they note and that are listed in the article. Future studies are needed to evaluate the real impact of NIV on the sleep of these critical care patients. For conducting our study, we used one dedicated NIV ventilator (NIVD) and two conventional ICU ventilators (NIVICU) that perform very well in bench evaluations compared with other ventilators of their families (2). The results obtained with them cannot be applied to other ventilators as you point out. Regarding the ventilator used in the prerandomization period, most of the patients were ventilated using a NIVICU because of higher availability of these devices in our ICU. This could have constituted a bias as well as the fact that three patients (two in the NIVICU group and one in the NIVD group) had previously received NIV for an acute hypercapnic respiratory failure. Nevertheless, conscious of the NIV adaptation effect, we excluded all home-ventilated patients. During the night study period, no ventilatory adjustments were made. First, because we assumed that setting a pressure support to obtain a tidal volume of 8 mL/kg of predicted body weigh during the daytime would keep the tidal volume between 6 and 8 mL/kg during the sleep time, as it happened; and second, because no monitoring of respiratory events for positive end-expiratory pressure adjustment in obstructive sleep apnea (OSA) patients was possible. We agree with Esquinas et al (1) that leaks could play a role in the trigger function and promote ineffective efforts. We have recovered qualitative information regarding the leak levels that, graded from 0 (absence) to 3 (high amount), were similar between groups (0.75 [0.35–1] in the NIVD group vs 1 [0.5–1.5] in the NIVICU group, p = 0.49). Leaks are also implicated in delaying the ventilator cycling to expiration, and limiting inspiratory time prevents prolonged cycles. As we explain in the article, this patient-ventilator asynchrony just happened in the NIVD group (not the NIVICU) because this variable was not adjustable in the NIVD, but its prevalence was very low. e482
www.ccmjournal.org
Finally, the higher prevalence of ineffective efforts in the NIVD groups also surprised us. All the possible explanations that Esquinas et al (1) mention have been discussed in the article (except for the presence of leaks that has been discussed above). We suspect that the main reason lies in the differences between groups, with more OSA, higher Epworth sleepiness scale, and higher body mass index in the NIVD group. In summary, some of our results were unplanned or unexpected. This is often one of the most interesting aspects of science but needs further confirmation. This work was performed at Réanimation Médicale, AP-HP, Groupe Hospitalier Albert Chenevier-Henri Mondor, Créteil, France. Dr. Brochard consulted for Draeger; institution lectured for General Electric. His institution received grant support from Philips Respironics (not related to this study), Covidien, Vygon, and Draeger and lectured for General Electric. Dr. Cordoba-Izuierdo disclosed that she does not have any potential conflicts of interest. Ana Córdoba-Izquierdo, MD, Réanimation Médicale, AP-HP, Groupe Hospitalier Albert Chenevier-Henri Mondor, Créteil, France, and Servei de Pneumologia, Hospital Universitari de Bellvitge, L’Hospitalet de Llobregat, Barcelona, Spain; Laurent Brochard, MD, Réanimation Médicale, AP-HP, Groupe hospitalier Albert Chenevier-Henri Mondor, Créteil, France, INSERM Unité 922 Equipe 13, Créteil, France, Faculté de Médecine, Université Paris 12, Créteil, France, and Service de Soins Intensifs, Hôpitaux Universitaires de Genève, Geneva University, Geneva, Switzerland
REFERENCES
1. Esquinas AM, Scala R, Rabec C: Noninvasive Mechanical Ventilation and Sleep Quality in ICU: Intensivists Are Waking Up! Crit Care Med 2013; 41:e481–e482 2. Carteaux G, Lyazidi A, Cordoba-Izquierdo A, et al: Patient-ventilator asynchrony during noninvasive ventilation: A bench and clinical study. Chest 2012; 142:367–376 DOI: 10.1097CCM.0000000000000023
Vasopressin Guidelines in Surviving Sepsis Campaign: 2012 Dear Editor:
W
e would like to comment and ask questions about the recommendations in the 2012 Surviving Sepsis Campaign International Guidelines (1) regarding the use of vasopressin for hemodynamic support. Although we agree with the recommendation that “Vasopressin 0.03 units/min can be added to norepinephrine (NE) with intent of either raising [mean arterial pressure] or decreasing NE dosage,” we are surprised that this recommendation is ungraded. We believe that there is strong evidence that when vasopressin is administered in septic shock, it acts as a vasoconstrictor and thus both raises mean arterial pressure and decreases norepinephrine dosage. Data from the Vasopressin in Septic Shock Trial study, a large randomized controlled trial (2), clearly show that patients randomized to vasopressin December 2013 • Volume 41 • Number 12
not have a true exhalation valve and uses a single-limb circuit. Single-circuit pressure-targeted ventilators provided with a calibrated leak (called “bilevel ventilators”) are most commonly used for NIV. For their trial, Roche Campo et al used valve-based ventilators. Several differences in technical performances of NIVD are largely reported. So, how these results Figure 1. Pathways for the horizontal transmission of Acinetobacter baumannii from a colonized/infected could be applied to all bilevel patient to a noncolonized patient. devices is not known (3). Third issue concerns type 4. Munoz-Price LS, Arheart KL, Mills JP, et al: Associations between bacof ventilator used in the prerandomization period. We lack for terial contamination of health care workers’ hands and contamination this information. Furthermore, three patients were not naïve of white coats and scrubs. Am J Infect Control 2012; 40:e245–e248 for NIV. It is well known that previous adaptation could influ 5. Munoz-Price LS, Quinn JP: Deconstructing the infection control bundles for the containment of carbapenem-resistant Enterobacteriaceae. ence efficacy of NIV, and this could lead to a bias (4). FurtherCurr Opin Infect Dis 2013; 26:378–387 more, the fact that the setting of ventilators was not different 6. Munoz-Price LS, Namias N, Cleary T, et al: Acinetobacter baumanin nighttime versus daytime sessions of NIV is not trivial as it nii: Association between environmental contamination of patient is well known that ventilatory needs largely change during the rooms and occupant status. Infect Control Hosp Epidemiol 2013; 34:517–520 sleep especially in patients with sleep-related syndromes (5). 7. Munoz-Price LS, Ariza-Heredia E, Adams S, et al: Use of UV powLeaks have neither measured nor estimated. They can affect der for surveillance to improve environmental cleaning. Infect Control trigger function by preventing the detection of patient inspiratory Hosp Epidemiol 2011; 32:283–285 effort but also delay switching into expiration. To limit this last 8. Munoz-Price LS, Fajardo-Aquino Y, Arheart KL: Ultraviolet powder versus ultraviolet gel for assessing environmental cleaning. Infect effect, it is important to set a maximal inspiratory time, a safety Control Hosp Epidemiol 2012; 33:192–195 feature to prevent unsuitable lengthening of inspiratory duration 9. Munoz-Price LS, Birnbach DJ, Lubarsky DA, et al: Decreasing (5). For case, the occurrence of that the authors called “prolonged operating room environmental pathogen contamination through improved cleaning practice. Infect Control Hosp Epidemiol 2012; cycle” only in NIVICU is probably a negative consequence of leaks 33:897–904 due to the impossibility to set a Timax in this device. DOI: 10.1097/CCM.0b013e3182a84bf7 Finally, a higher ineffective effort with NIVD is at least surprising. To limit the negative effects of leaks on trigger function, NIVD devices include sophisticated algorithms supposed Noninvasive Mechanical Ventilation and Sleep to improve trigger responses in front of leaks. So, we can expect Quality in ICU: Intensivists Are Waking Up! that these devices have a better response during leaks. More leakage in NIVD patients, trigger setted too insensitive or even To the Editor: an inadapted triggering response in this particular ventilator, leep in critically patients during noninvasive mechanical the presumable higher rate of obstructive sleep apnea in NIVD ventilation (NIV) is a growing topic (1). We read with patients are all possible explanations for this apparent paradox. great interest the article published by Córdoba-Izquierdo So, starting from this study, it is time to call for other bricks in et al (2) in a recent issue of Critical Care Medicine. Neverthe- the wall of “sleep and NIV in ICU.” less, some important questions need to be raised. The authors have disclosed that they do not have any potenFirst, due to some methodological bias of the study (greater tial conflicts of interest. amount of hours spent on NIV in nighttime with less sleep Antonio M. Esquinas, MD, PhD, FCCP, Intensive Care interferences, unavailable statistical power data, and lack of Unit and Non-Invasive Ventilation Unit, Hospital Morales crossover randomized design), unfortunately, we have no Meseguer, Murcia, Spain; Raffaele Scala, MD, Respiratory robust data to assert that sleep quality was better on NIV than Ward and Respiratory Intensive Care Unit, San Donato during unassisted breathing. Hospital, Arezzo, Italy; Claudio Rabec, MD, Service de Second, due to the huge heterogeneity of NIVICU and NIVD, Pneumologie et Réanimation Respiratoire, Centre Hospitalier et Universitaire de Dijon, Dijon, France the “take-home message” should be mitigated as these findings could not be applicable to all ventilators belonging to the two categories. For example, two different types of circuits can be REFERENCES used in NIVD. The first type uses a similar assembly to those 1. Roche Campo F, Drouot X, Thille AW, et al: Poor sleep quality is assoused in ICU devices in which inspiration and expiration are ciated with late noninvasive ventilation failure in patients with acute separated and an expiratory valve is present. A second type does hypercapnic respiratory failure. Crit Care Med 2010; 38:477–485
S
Critical Care Medicine
www.ccmjournal.org
e481
Online Letter to the Editors 2. Córdoba-Izquierdo A, Drouot X, Thille AW, et al: Sleep in Hypercapnic Critical Care Patients Under Noninvasive Ventilation: Conventional Versus Dedicated Ventilators. Crit Care Med 2013; 41:60–68 3. Pérel Jaillet A, Letellier C, Bounoiare D, et al: Evaluation de l’adaptation lors de la mise en route d’une ventilation non invasive (VNI). Rev Mal Resp 2011; 28:A5 4. Fanfulla F, Delmastro M, Berardinelli A, et al: Effects of different ventilator settings on sleep and inspiratory effort in patients with neuromuscular disease. Am J Respir Crit Care Med 2005; 172:619–624 5. Rabec C, Rodenstein D, Leger P, et al; SomnoNIV Group: Ventilator modes and settings during non-invasive ventilation: Effects on respiratory events and implications for their identification. Thorax 2011; 66:170–178 DOI: 10.1097/CCM.0b013e3182a5258f
The authors reply:
W
e thank Esquinas et al (1) for their comments and the opportunity to clarify a number of points from our work. One of the most interesting findings of our study was that patients could sleep during noninvasive ventilation (NIV) because no data concerning sleep quality of critical care patients under NIV existed before. However, the better sleep quality during NIV compared with unassisted breathing needs to be considered cautiously regarding all the limitations that they note and that are listed in the article. Future studies are needed to evaluate the real impact of NIV on the sleep of these critical care patients. For conducting our study, we used one dedicated NIV ventilator (NIVD) and two conventional ICU ventilators (NIVICU) that perform very well in bench evaluations compared with other ventilators of their families (2). The results obtained with them cannot be applied to other ventilators as you point out. Regarding the ventilator used in the prerandomization period, most of the patients were ventilated using a NIVICU because of higher availability of these devices in our ICU. This could have constituted a bias as well as the fact that three patients (two in the NIVICU group and one in the NIVD group) had previously received NIV for an acute hypercapnic respiratory failure. Nevertheless, conscious of the NIV adaptation effect, we excluded all home-ventilated patients. During the night study period, no ventilatory adjustments were made. First, because we assumed that setting a pressure support to obtain a tidal volume of 8 mL/kg of predicted body weigh during the daytime would keep the tidal volume between 6 and 8 mL/kg during the sleep time, as it happened; and second, because no monitoring of respiratory events for positive end-expiratory pressure adjustment in obstructive sleep apnea (OSA) patients was possible. We agree with Esquinas et al (1) that leaks could play a role in the trigger function and promote ineffective efforts. We have recovered qualitative information regarding the leak levels that, graded from 0 (absence) to 3 (high amount), were similar between groups (0.75 [0.35–1] in the NIVD group vs 1 [0.5–1.5] in the NIVICU group, p = 0.49). Leaks are also implicated in delaying the ventilator cycling to expiration, and limiting inspiratory time prevents prolonged cycles. As we explain in the article, this patient-ventilator asynchrony just happened in the NIVD group (not the NIVICU) because this variable was not adjustable in the NIVD, but its prevalence was very low. e482
www.ccmjournal.org
Finally, the higher prevalence of ineffective efforts in the NIVD groups also surprised us. All the possible explanations that Esquinas et al (1) mention have been discussed in the article (except for the presence of leaks that has been discussed above). We suspect that the main reason lies in the differences between groups, with more OSA, higher Epworth sleepiness scale, and higher body mass index in the NIVD group. In summary, some of our results were unplanned or unexpected. This is often one of the most interesting aspects of science but needs further confirmation. This work was performed at Réanimation Médicale, AP-HP, Groupe Hospitalier Albert Chenevier-Henri Mondor, Créteil, France. Dr. Brochard consulted for Draeger; institution lectured for General Electric. His institution received grant support from Philips Respironics (not related to this study), Covidien, Vygon, and Draeger and lectured for General Electric. Dr. Cordoba-Izuierdo disclosed that she does not have any potential conflicts of interest. Ana Córdoba-Izquierdo, MD, Réanimation Médicale, AP-HP, Groupe Hospitalier Albert Chenevier-Henri Mondor, Créteil, France, and Servei de Pneumologia, Hospital Universitari de Bellvitge, L’Hospitalet de Llobregat, Barcelona, Spain; Laurent Brochard, MD, Réanimation Médicale, AP-HP, Groupe hospitalier Albert Chenevier-Henri Mondor, Créteil, France, INSERM Unité 922 Equipe 13, Créteil, France, Faculté de Médecine, Université Paris 12, Créteil, France, and Service de Soins Intensifs, Hôpitaux Universitaires de Genève, Geneva University, Geneva, Switzerland
REFERENCES
1. Esquinas AM, Scala R, Rabec C: Noninvasive Mechanical Ventilation and Sleep Quality in ICU: Intensivists Are Waking Up! Crit Care Med 2013; 41:e481–e482 2. Carteaux G, Lyazidi A, Cordoba-Izquierdo A, et al: Patient-ventilator asynchrony during noninvasive ventilation: A bench and clinical study. Chest 2012; 142:367–376 DOI: 10.1097CCM.0000000000000023
Vasopressin Guidelines in Surviving Sepsis Campaign: 2012 Dear Editor:
W
e would like to comment and ask questions about the recommendations in the 2012 Surviving Sepsis Campaign International Guidelines (1) regarding the use of vasopressin for hemodynamic support. Although we agree with the recommendation that “Vasopressin 0.03 units/min can be added to norepinephrine (NE) with intent of either raising [mean arterial pressure] or decreasing NE dosage,” we are surprised that this recommendation is ungraded. We believe that there is strong evidence that when vasopressin is administered in septic shock, it acts as a vasoconstrictor and thus both raises mean arterial pressure and decreases norepinephrine dosage. Data from the Vasopressin in Septic Shock Trial study, a large randomized controlled trial (2), clearly show that patients randomized to vasopressin December 2013 • Volume 41 • Number 12
