Analysis of the effects of the alveolar recruitment maneuver on blood oxygenation during bariatric surgery

Abstracts

JUSTIFICATIVAS E OBJETIVOS: A manobra de recrutamento alveolar (MRA) é indicada no tratamento de atelectasias intraoperatórias. O objetivo do presente estudo foi comparar duas técnicas de MRA por meio da resposta da relação PaO2/FiO2 e da soma [PaO2+PaCO2], em pacientes obesos grau III. MÉTODO: Estudo prospectivo aberto em pacientes adultos, obesos grau III, submetidos a procedimento cirúrgico bariátrico em ventilação controlada a volume, pressão positiva no final da expiração (PEEP) de 5 cmH2O e divididos em três grupos: G CONT: PEEP de 5 cmH2O; G MRA10/15/20 após sutura da aponeurose: aumento progressivo da PEEP para 10,15 e 20 cmH2O, pausa de 40 segundos e manutenção de cada valor da PEEP por 2 minutos; G MRA30: após sutura da aponeurose: aumento súbito da PEEP para 30 cmH2O, 40 segundos de pausa e manutenção da PEEP em 30 cmH2O por dois minutos. Foram analisadas as variáveis frequência cardíaca, pressão arterial média, sistólica, diastólica, pressão média das vias aéreas (P MVA) e de platô (P PLAT), pressão arterial de oxigênio (PaO2), pressão arterial de CO2 (PaCO2), relação PaO2/FiO2 (fração inspiratória de oxigênio) e soma [PaO2+PaCO2]. RESULTADOS: As variáveis que apresentaram diferença estatística significativa entre os três grupos foram: P PLAT, P MVA, PaO2, relação PaO2/FiO2 e soma [PaO2+PaCO2] (p < 0,0001). Na comparação dos grupos dois a dois, verificou-se diferença estatística significativa para as variáveis P PLAT e P MVA: G CONT X G MRA10/15/20 e G CONT X G MRA30 e para as variáveis relação PaO2/FiO2 e soma [PaO2+PaCO2]: G CONT X G MRA30. CONCLUSÕES: A técnica de MRA com aumento súbito da PEEP para 30 cm H2O mostrou a melhor resposta da relação PaO2/FiO2.

CIRURGIA; COMPLICAÇÕES; VENTILAÇÃO; VENTILAÇÃO

SCIENTIFIC ARTICLE

Analysis of the effects of the alveolar recruitment maneuver on blood oxygenation during bariatric surgery^*

Análisis de los efectos de la maniobra de reclutamiento alveolar en la oxigenación sanguínea durante el procedimiento bariátrico

Alda Paiva de Souza^I; Márcia Buschpigel^II; Ligia Andrade Silva Telles Mathias, TSA^III; Carlos Alberto Malheiros^IV; Vera Lucia dos Santos Alves^V

^IFisioterapeuta Respiratória do Departamento de Recuperação Pós-anestésica, UTI do Departamento de Cirurgia e UTI - Neurocirurgia da ISCMSP; Mestre em Ciências da Saúde - Faculdade de Ciências Médicas da Santa Casa de São Paulo (FCMSCSP)

^IIAnestesiologista do Hospital Central da ISCMSP

^IIIDiretora do Serviço e Disciplina de Anestesiologia da ISCMSP e FCMSCSP; Responsável pelo CET/SBA da ISCMSP

^IVMédico-Cirurgião; Diretor do Departamento de Cirurgia e Diretor da Disciplina de Área IV: Estômago, Duodeno e Obesidade da ISCMSP

^VProfessora da FCMSCSP; Chefe do Serviço de Fisioterapia Respiratória do Hospital Santa Isabel; Doutora em Ciências da Saúde - FCMSCSP

Correspondence to

SUMMARY

BACKGROUND AND METHDS: Alveolar recruitment maneuver (ARM) is indicated in the treatment of intraoperative atelectasis. The objective of the present study was to compare two techniques of ARM using the response of the PaO₂/FiO₂ ratio and [PaO₂ + PaCO₂] in patients with grade III obesity.

METHODS: This was an open prospective study with adult patients with grade III obesity who underwent bariatric surgery under volume-controlled mechanical ventilation with positive end-expiratory pressure (PEEP) of 5 cmH₂O, divided in three groups: G_CONT: PEEP of 5 cmH₂O; G_ARM10/15/20 after suture of the aponeurosis: progressive increase in PEEP to 10, 15, and 20 cmH₂O with a 40-second pause and maintaining each level of PEEP for 2 minutes; and G_ARM30 after suture of the aponeurosis: sudden increase in PEEP to 30 cmH₂O with a 40-second pause and maintaining a PEEP of 30 for 2 minutes. Heart rate, mean arterial pressure, systolic and diastolic blood pressure, mean (P_AW) and plateau (P_PLAT) airways pressure, partial pressure of oxygen (PaO₂), partial pressure of carbon dioxide (PaCO₂), PaO₂/FiO₂ ratio (inspired fraction of oxygen), and [PaO₂ + PaCO₂] were analyzed.

RESULTS: The following parameters showed statistically significant differences among the study groups: P_PLAT, P_AW, PaO₂, PaO₂/FiO₂ ratio, and [PaO₂ + PaCO₂] (p < 0.0001). Comparing the groups two by two, the following parameters showed statistically significant differences: for P_PLAT and P_AW: G_CONT x G_2ARM10/15/20 and G_CONT x G_ARM30; and for PaO₂/FiO₂ ratio and [PaO₂ + PaCO₂]: G_CONT x G_ARM30.

CONCLUSIONS: Alveolar recruitment maneuver with sudden increase of PEEP to 30 cmH₂O showed a better response of the PaO₂/FiO₂ ratio.

Key Words: COMPLICATIONS: atelectasis; SURGERY, Bariatric; VENTILATION: alveolar recruitment maneuver, positive end-expiratory pressure

RESUMEN

JUSTIFICATIVAS Y OBJETIVOS: La maniobra de reclutamiento alveolar (MRA) se indica en el tratamiento de atelectasias intraoperatorias. El objetivo del presente estudio fue comparar dos técnicas de MRA por medio de la respuesta de la relación PaO₂/FiO₂ y de la suma [PaO₂+PaCO₂], en pacientes obesos con grado III.

MÉTODO: Estudio prospectivo abierto en pacientes adultos, obesos grado III, sometidos a procedimiento quirúrgico bariátrico en ventilación controlada a volumen, presión positiva al final de la expiración (PEEP) de 5 cmH₂O y divididos en tres grupos: G_CONTROL: PEEP de 5 cmH₂O; G_MRA10/15/20 después de la sutura de la aponeurosis: aumento progresivo de la PEEP para 10,15 y 20 cmH₂O, pausa de 40 segundos y mantenimiento de cada valor de la PEEP por 2 minutos; G_MRA30: después de la sutura de la aponeurosis: aumento súbito de la PEEP para 30 cmH₂O, 40 segundos de pausa y mantenimiento de la PEEP en 30 cmH₂O por dos minutos. Se analizaron las variables frecuencia cardíaca, presión arterial promedio, sistólica, diastólica, presión promedio de las vías aéreas (P_MVA) y de meseta (P_PLAT), presión arterial de oxígeno (PaO₂₎, presión arterial de CO₂ (PaCO₂), relación PaO₂/FiO₂ (fracción inspiratoria de oxígeno) y suma [PaO₂+PaCO₂].

RESULTADOS: Las variables que presentaron una diferencia estadística significativa entre los tres grupos fueron: P_PLAT, P_MVA, PaO_2, relación PaO₂/FiO₂ y suma [PaO₂+PaCO₂] (p < 0,0001). En la comparación de los grupos dos a dos, se verificó una diferencia estadística significativa para las variables P_PLAT y P_MVA: G_CONTROL X G_MRA10/15/20 y G_CONTROL X G_MRA30 y para las variables relación PaO₂/FiO₂ y suma [PaO₂+PaCO₂]: G_CONTROL X G_MRA30.

CONCLUSIONES: La técnica de MRA con aumento súbito de la PEEP para 30 cm H₂O mostró la mejor respuesta de la relación PaO₂/FiO₂.

INTRODUCTION

The development of atelectasis is common during general anesthesia due to the reduction in residual functional capacity (RFC) ^1,2. This situation tends to be worse in patients with grade III obesity since their RFC is already reduced during spontaneous breathing ³.

Alveolar recruitment maneuver (ARM) consists of sustained insufflations, mainly with the use of positive end-expiratory pressure (PEEP). The use of ARM is indicated in the presence of atelectasis or alveolar hypoventilation, in the initial stages of pulmonary lesion and acute respiratory distress syndrome, and in patients with alveolar instability ^4-6. In open bariatric surgery, the use of PEEP to prevent the development of areas of atelectasis has been suggested, although the levels have not been established, which motivated this study.

The objective of the present study was to compare two techniques of ARM using the response of the ratio between the partial pressure of oxygen and the inspired fraction of oxygen (PaO₂/FiO₂) and the sum of the partial pressure of oxygen with the partial pressure of carbon dioxide [PaO₂ +PaCO₂] in patients with grade III obesity undergoing open bariatric surgery.

METHODS

After approval by the Ethics Committee of the Irmandade da Santa Casa de Misericórdia de São Paulo, patients from the Department of Surgery of the Stomach, Duodenum and Obesity Division with the diagnosis of grade III obesity undergoing sylastic ring gastric bypass with Y-en-Roux anastomosis, from March 2004 to June 2005, were enrolled in this open, prospective study.

Patients underwent preoperative evaluation by a multidisciplinary team, all necessary explanations were given, and an informed consent was signed.

Patients were randomly divided in three groups:

• Control group (G

  _CONT): ventilation with PEEP of 5 cmH

  ₂O;

• ARM 10/15/20 group (G

  _ARM10/15/20): progressive ARM with PEEP of 10, 15, and 20 cmH

  ₂O;

• ARM 30 group (G

  _ARM30): conventional ARM, according to the American-European Consensus, using PEEP of 30 cmH

  ₂O and plateau pressure (P

  _PLAT) of 35 cmH

  ₂O

  ^5,6.

Inclusion criteria were as follows: BMI > 40 kg.m^-2; and normal pulmonary function tests or with mild abnormalities. Patients with history of spontaneous pneumothorax and laparoscopic gastroplasty were excluded.

The sequence of care of patients in all three groups was identical. In the operating room, a peripheral vein was cannulated with an 18G catheter and hydration with Ringer's lactate was initiated.

Patients were placed in dorsal decubitus with discrete head-up tilt. The following parameters were monitored: heart rate (HR); electrocardiogram (ECG); non-invasive systolic (SBP) and diastolic (DBP) blood pressure; and peripheral hemoglobin saturation (SpO₂).

Ventilation was initiated with 100% O₂ with a face mask, followed by anesthetic induction with the sequential administration of intravenous midazolam (5 to 10 mg), alfentanil (300 µg), propofol (2 to 3 mg.kg^-1), and atracurium (50 mg). Anesthesia was maintained with propofol, 0.075 to 0.1 mg.kg^-1. min^-1, and alfentanil, 0.75 to 1.0 µg.kg^-1.min^-1 .

After tracheal intubation, patients were maintained with volume-controlled mechanical ventilation using the anesthesia equipment in a semi-closed circular system (model LINEA A Intermed^1® Brazil), with tidal volume (VT) of 8 to 10 mL.kg^-1 of ideal weight, limiting pressure to 45 cmH₂O, inspired fraction of O₂ (FiO₂) of 0.5, respiratory rate of 12 to 14, and PEEP of 5 cmH₂O.

Study groups:

• G

  _CONT: ventilation with PEEP of 5 cmH

  ₂O until the end of the surgery (

  Figure 1).

In the other two groups, ARM was done after suture of the aponeurosis as follows (Figure 1):

• G

  _ARM10/15/20:

  - progressive increase of PEEP to 10 cmH₂O; 40-second pause; PEEP of 10 cmH₂O maintained for 120 seconds;

  - progressive increase of PEEP to 15 cmH₂O; 40-second pause; PEEP of 15 cmH₂O maintained for 120 seconds;

  - progressive increase of PEEP to 20 cmH₂O; 40-second pause; PEEP of 20 cmH₂O maintained for 120 seconds; and

  - gradual reduction in PEEP to the initial level of 5 cmH₂O every 5 ipm.

• G

  _ARM30:

  - sudden increase of PEEP from 5 to 30 cmH₂O; 40-second pause; PEEP of 30 cmH₂O maintained for 120 seconds;

  - gradual reduction in PEEP to the initial level by 5 cmH₂O every 5 ipm.

Parameters analyzed included: age, gender, weight, height, and BMI; length of surgery; HR, SBP, and DBP; SpO₂, PaO₂, PaCO₂, PaO₂/FiO₂ ratio, [PaO₂ + PaCO₂], plateau pressure (P_PLAT), and mean airways pressure (P_MAV); and intraoperative complications.

Heart rate, SBP, DBP, and SpO₂ were analyzed before induction and every 5 minutes until the end of the procedure. Partial pressure of oxygen, PaCO₂, PaO₂/PaCO₂ ratio, [PaO₂ + PaCO₂], plateau pressure (P_PALT), and mean airways pressure (P_AW) were analyzed immediately after suture of the aponeurosis (before ARM) and at the end of ARM.

ANOVA was used to compare quantitative parameters in relation to the three groups, and the Kruskal-Wallis test and the Tukey method were used for multiple comparisons. The chi-square test was used to compare qualitative parameters. The level of significance adopted was 5%.

The software SPSS (Statistical Package for the Social Sciences) for Windows 10.01 and the Epi Info version 3.2.2 were used for the statistical analysis.

RESULTS

The final sample was composed of 47 patients, 14 in G_CONT, 17 in G_ARM10/15/20, and 16 in G_ARM30. Demographic data, length of surgery, and initial hemodynamic parameters and SpO₂ did not show statistically significant differences (Table I).

Hemodynamic parameters and SpO₂ did not show statistically significant differences throughout the study.

Immediately before ARM, PaO₂, PaCO₂, PaO₂/FiO₂ ratio, [PaO₂ + PaCO₂], P_PLAT, and P_AW did not show statistically significant differences among the three groups (Table III).

At the time of ARM (Table III), a statistically significant difference was observed among the three groups for: PaO₂, PaO₂/FiO₂ ratio, [PaO₂ + PaCO₂], P_PLAT, and P_AW. Subsequently, the Tukey test was used to analyze those parameters, which showed statistically significant differences between G_CONT and G_ARM30 (p < 0.05) for PaO₂, PaO₂/FiO₂ ratio, and [PaO₂ + PaCO₂]. For P_PLAT and P_AW, Tukey test showed statistically significant differences in all groups when compared two by two (G_CONT x G_ARM10/15/20, p < 0.001; G_CONT x G_ARM30, p < 0.001; G_ARM10/15/20 x G_ARM30, p < 0.01), except when G_PLAT was compared with G_ARM10/15/20 and G_ARM30 (p > 0.05).

Intraoperative complications were not observed.

Table II

DISCUSSION

Perioperative pulmonary complications represent a significant cause of morbidity and mortality ⁸, and atelectasis affect almost 90% of the patients undergoing general anesthesia, with a positive correlation with the perioperative values of pulmonary shunts ^1,8-12; this explains why the moment of the surgery and respiratory monitoring were chosen to evaluate the ventilation/perfusion imbalance.

Immediately after general anesthesia, atelectasis, which are responsible for the perioperative changes in oxygenation, develop in dependent areas of the pulmonary parenchyma; PEEP, maintained at 5 cmH₂O throughout the surgery, led to the opening and maintenance of alveolar permeability ¹⁰, which was confirmed by the analysis of the levels of hyperoxia demonstrated by SpO₂ and PaO₂ in all three groups before and after alveolar recruitment maneuver (ARM), in which PaO₂ was elevated in every phase. It was possible to demonstrate it even when obese patients were ventilated with lower levels of VT (between 10 and 11 mL.kg^-1) and FiO₂ (0.4) ⁷.

Maintenance of the tidal volume is also debated in the literature and, when above 12 mL.kg^-1 it is associated with alveolar hyperinflation, compression of the adjacent pulmonary capillary, and inadequate gas exchange. Hedenstierna ¹³ stated that the main causes of alveolar collapse include the loss of muscular tone and high inspired fractions of oxygen (FiO₂). In the present study, the orientation of the Brazilian consensus on mechanical ventilation, maintaining constant VT at 10 mL.kg^-1 and FiO₂ of 0.5, was followed, leading to results similar to those of Coussa et al. ² and Pelosi et al. ¹⁴, in which obese patients ventilated with a VT of 10 mL.kg^-1 showed a significant improvement in PaO₂, since the BMI is related with the reduction of RFC.

The use of PEEP is typically associated with an increase of P_AW, which was constant in all three groups from the beginning of the surgery on, with a proportional increase with increasing levels of PEEP ³².

The elevated P_AW suggests greater mechanical pulmonary vulnerability, because the increase in PEEP increased P_PLAT significantly. The resistance exerted by the adipose tissue in the thoracic region of the patients in this study could also have contributed to the significant change in P_AW in all phases of changes in PEEP ^1,7,15.

The relationship between BMI and FRC has been reported by several authors who study the changes in gas exchange in obese individuals ^7,15-19. The reduction in FRC is also common after the institution of mechanical ventilation, as reported by Pelosi et al. ⁹, who proposed the inverse relationship between the reduction in oxygenation and pulmonary volume and the BMI.

In view of what was explained above, the alveolar recruitment maneuver (ARM) is a technique that leads to the opening of collapsed alveolar units through the sustained increase in airways pressure, increasing the pulmonary area available for gas exchange and, consequently, arterial oxygenation ²⁰.

The response of acute pulmonary lesion (APL) and acute respiratory distress syndrome (ARDS) to ARM with pressures of 45 cmH₂O in non-obese patients can present different pulmonary profiles, which are classified as: difficult to recruit, reasonably recruitable, or potentially recruitable ¹⁸. Obese patients can also be classified, in a similar fashion, by the elevated BMI as compromised thoracic cage, increased resistance, and decreased complacence. This can hinder comparison of the results obtained for alveolar recruitment, as reported by several studies ^8,9,15.

The PaO₂/FiO₂ ratio and [PaO₂ + PaCO₂] in the three study groups increased progressively, but without changes among the groups and [PaO₂ + PCO₂], demonstrating the absence of pulmonary lesion (normal level: e 400 mmHg with FiO₂ = 1.0). However, patients in G_ARM30 showed better response of the PaO₂/FiO₂ ratio and [PaO₂ + PaCO₂], but this last index is not commonly used during studies on the response to ARM in patients with APL and ARDS.

Borges et al. ²⁴, analyzing patients with acute pulmonary lesion associated with early hypoxemia, demonstrated that APL can be reverted when elevated pressures are used in the airways (above 60 cmH₂O). However, the harmful effects (barotrauma, hyperinsufflation, decreased cardiac index, and disrupted hemodynamics) are more commonly seen when the same levels of inspiratory pressure are used for prolonged times ²⁵.

The alveolar recruitment maneuver with PEEP of 30 cmH₂O used in G_ARM30 was idealized according to the American-European Consensus, and showed better response of the PaO₂/FiO₂ ratio and [PaO₂ + PaCO₂] ²⁶.

According to the literature, CPAP (continuous positive airways pressure), with pressure levels ranging from 30 to 40 cmH₂O for 30 to 90 seconds in patients with ARDS, is the method used more often by authors to sustain airways pressure ^20,27,28.

In other studies ^6,29, this level of pressure was maintained for 15 seconds and the area of recruitment was followed-up by CT scan during ARM. The authors noticed that, after seven seconds of recruitment, PaO₂ improved significantly and the areas of atelectasis reduced. The lower incidence of reduced cardiac output and blood pressure is the main advantage of the shorter ARM ⁹; however, the study population is small, being classified as a level D scientific evidence recommendation. In the present study, increased PEEP levels were maintained for two minutes, which did not change the hemodynamic parameters of the patients.

Under the conditions of the present study, the best response of the PaO₂/FiO₂ ratio was seen with the alveolar recruitment maneuver with PEEP of 30 cmH₂O for two minutes.

REFERENCES

• 01. Perilli V, Sollazzi L, Bozza P et al. - The effects of the reverse trendelenburg position on respiratory mechanics and blood gases in morbidly obese patients during bariatric surgery. Anesth Analg, 2000;91:1520-1525.
• 02. Coussa M, Proietti S, Schnyder P et al. - Prevention of atelectasis formation during the induction of general anesthesia in morbidly obese patients. Anesth Analg, 2004;98:1491-1495.
• 03. Biring MS, Lewis MI, Liu JI et al. - Pulmonary physiologic changes of morbid obesity. Am J Med Sci, 1999;318:293-297.
• 04. Slutsky AS - Consensus Conference on Mechanical Ventilation. Part 2. Intensive Care Med, 1994;20:150-162.
• 05. Artigas A, Bernard GR, Carlet J et al. - The American-European Consensus Conference on ARDS, part 2: Ventilatory, pharmacologic, supportive therapy, study design strategies, and issues related to recovery and remodeling. Acute respiratory distress syndrome. Am J Respir Crit Care Med, 1998;157:1332-1347.
• 06. Beppu OS, Guanaes A - PEEP (Pressão Positiva ao Final da Expiração), em: Carvalho CRR - Ventilação Mecânica I - Básico - Relatório do II Consenso Brasileiro de Ventilação Mecânica. São Paulo, Atheneu, 2003;327-330.
• 07. Benseñor FEM, Auler JOC - P_ETCO₂ e SpO₂ permitem ajuste ventilatório adequado em pacientes obesos mórbidos. Rev Bras Anestesiol, 2004;54:542-552.
• 08. Warner DO - Preventing postoperative pulmonary complications: the role of the anesthesiologist. Anesthesiology, 2000; 92:1467-1472.
• 09. Pelosi P, Croci M, Ravagnan I et al. - The effects of body mass on lung volume, respiratory mechanics, and gas exchange during general anesthesia. Anesth Analg, 1998;87:654-660.
• 10. Auler Jr JOC, Galas FRBG, Hajjar LA et al - Ventilação mecânica no intra-operatório. J Bras Pneumol, 2007;33:137s-141s.
• 11. Gander S, Frascarolo P, Suter M et al. - Positive end-expiratory pressure during induction of general anesthesia increases duration of nonhypoxic apnea in morbidly obese patients. Anesth Analg, 2005;100:580-584.
• 12. Paisani DM, Chiavegato LD, Faresin SM - Volumes, capacidades pulmonares e força muscular respiratória no pós-operatório de gastroplastia. J Bras Pneumol, 2005;31:125-132.
• 13. Hedenstierna G - Atelectasis and gas exchange during anaesthesia. Electromedica, 2003;71:70-73.
• 14. Pelosi P, Croci M, Ravagnan I et al. - Total respiratory system, lung, and chest wall mechanics in sedated-paralyzed postoperative morbidly obese patients. Chest, 1996;109:144-151.
• 15. Miyoshi E, Margarido CB, Oliveira MAV et al. - Obeso mórbido e anestesia. Atual Anestesiol - Saesp, 2001;6:102-116.
• 16. Bardoczky GI, Yernault JC, Houben JJ et al. - Large tidal volume ventilation does not improve oxygenation in morbidly obese patients during anesthesia. Anest Analg, 1995;81:385-388.
• 17. Neumann P, Rothen HU, Berglund JE et al. - Positive end-expiratory pressure prevents atelectasis during general anaesthesia even in the presence of a high inspired oxygen concentration. Acta Anaesthesiol Scand, 1999;43:295-301.
• 18. Gattinoni L, Caironi P, Cressoni M et al. - Lung recruitment in patients with the acute respiratory distress syndrome. N Eng J Med, 2006; 354:1775-1786.
• 19. Auler Jr JOC, Miyoshi E, Fernandes CR et al. - The effects of abdominal opening on respiratory mechanics during general anesthesia in normal and morbidly obese patients: a comparative study. Anesth Analg, 2002;94:741-748.
• 20. Dyhr T, Nygard E, Laursen N et al. - Both lung recruitment maneuver and PEEP are needed to increase oxygenation and volume after cardiac surgery. Acta Anaesthesiol Scand, 2004;48: 187-197.
• 21. Richard JC, Maggiore SM, Jonson B et al. - Influence of tidal volume on alveolar recruitment. Respective role of PEEP and a recruitment maneuver. Am J Respir Crit Care Med 2001;163: 1609-1613.
• 22. Henzler D, Rossaint R; Kuhlen R - Is there a need for a recruiting strategy in morbidly obese patients undergoing laparoscopic surgery? Anesth Analg, 2004;98:268.
• 23. Whalen FX, Gajic O, Thompson GB et al. - The effects of the alveolar recruitment maneuver and positive end-expiratory pressure on arterial oxygenation during laparoscopic bariatric surgery. Anesth Analg, 2006;102:298-305.
• 24. Borges JB, Okamoto VN, Matos GFJ et al. - Reversibility of lung collapse and hypoxemia in early acute respiratory distress syndrome (ARDS). Am J Respir Crit Care Med, 2006;174:268-278.
• 25. Bugedo G, Bruhn A - Is maximal lung recruitment worth it? Am J Respir Crit Care Med, 2006;174:1159.
• 26. Benseñor FEM - Ventilação artificial: anestesia para pacientes com obesidade mórbida. Atual Anestesiol - Saesp, 2005;10: 53-58.
• 27. Grasso S, Mascia L, Del Turco M et al. - Effects of recruiting maneuver in patients with acute respiratory distress syndrome ventilated with protective ventilatory strategy. Anesthesiology, 2002;96:795-802.
• 28. Amato MBP, Barbas CSV, Medeiros DM et al. - Effect of a protective-ventilation strategy on mortality in the acute respiratory distress syndrome. N Engl J Med, 1998;338:347-354.
• 29. Mancini MC, Aloé F - Obesidade, Apnéia Obstrutiva do Sono e Distúrbios Respiratórios, em: Halpern A, Matos AFG, Suplicy HL et al. - Obesidade. São Paulo, Lemos Editorial, 1998;153-170.

*

Recebido do Departamento de Cirurgia da Irmandade da Santa Casa de Misericórdia de São Paulo (ISCMSP), São Paulo, SP

Publication Dates

• Publication in this collection
  17 Apr 2009
• Date of issue
  Apr 2009

History

• Accepted
  10 Dec 2008
• Received
  02 Aug 2007