Social and contextual etiology of coronary heart disease in women

We explored the social and contextual etiology of coronary heart disease (CHD) prevention and management in women. Social and contextual influences on CHD risk include such factors as socioeconomic status, access to healthcare, cultural mores, working conditions including work overload, multiple role responsibilities, and social isolation. Women, particularly economically disadvantaged women, occupy lower levels on the social status hierarchy and, therefore, experience more stressful life experiences, less favorable living conditions, and less opportunity to affect positive health behavior and outcomes. Women are often discriminated against economically, politically, and socially, and this discrimination may adversely affect their efforts at CHD health promotion and treatment. Multiple role responsibilities within the family and psychosocial factors, including chronic life stress, are critical to an understanding of the health status of women, particularly poor and minority women. Although community-based interventions appear to be ideal for addressing the contextual risks related to CHD in women, a number of issues need to be considered, for example, the limited acknowledgment of secular trends in economic development that influence lifestyle decisions and health promotion efforts. Directions for research and interventions include recognition of the full spectrum of CHD risk in women, recognition of culturally competent interventions, and recognition of the need for empowerment of women.

A fibreoptic scoring system to assess the position of laryngeal mask airway devices. Interobserver variability and a comparison between the standard, flexible and intubating laryngeal mask airways

We determined the interobserver reliability of a fibreoptic scoring system for assessing the position of the laryngeal mask airway (LMA), the flexible laryngeal mask airway (FLMA) and the intubating laryngeal mask airway (ILM). We also compare fibreoptic position between the devices. Thirty anaesthetised adult patients were studied in random order in a triple crossover manner. Two observers blinded to each others findings scored the fibreoptic position as follows: 4, only vocal cords visible; 3, vocal cords plus posterior epiglottis visible; 2, vocal cords plus anterior epiglottis visible; 1, vocal cords not seen. Interobserver reliability was examined using intraclass correlation coefficient (ICC). Interobserver reliability was graded as excellent for the LMA (ICC = 0.89), FLMA (ICC = 0.87) and ILM (ICC = 0.79). Fibreoptic scores were higher for the LMA and FLMA compared with the ILM (both p < 0.001). We conclude that interobserver reliability for the fibreoptic scoring system is excellent for the LMA, FLMA and ILM. Fibreoptic position is better for the LMA and FLMA compared with the ILM. Fibreoptic scoring has potential utility for research and clinical practice with laryngeal mask devices.

Cervical spine motion during airway management: a cinefluoroscopic study of the posteriorly destabilized third cervical vertebrae in human cadavers

We conducted a randomized, controlled, crossover study to determine cervical spine motion for six airway management techniques in human cadavers with a posteriorly destabilized third cervical (C-3) vertebra. A destabilized C-3 segment was created in 10 cadavers (6-24 h postmortem). Cervical motion was recorded by continuous lateral fluoroscopy. The following airway management techniques were performed in random order on each cadaver with manual in-line stabilization applied: face mask ventilation (FM), laryngoscope-guided orotracheal intubation (OETT), fiberscope-guided nasal intubation (FOS-NETT), esophageal tracheal Combitube((R)) (Kendall-Sheridan, Neustadt, Germany) insertion (ETC), intubating laryngeal mask insertion with fiberscope-guided tracheal intubation (ILM-OETT), and laryngeal mask airway insertion (LMA). Afterward, maximum head-neck flexion (FLEX-MAX) and maximum head-neck extension (EXT-MAX) without manual in-line stabilization was performed to determine maximum motion. The maximum posterior displacement of C-3 and the maximum segmental sagittal motion of C2-3 were determined. There was a significant increase in posterior displacement for the FM (1.9 +/- 1.2 mm, P: < 0.01), OETT (2.6 +/- 1.6 mm, P: < 0.0001), ETC (3.2 +/- 1.6 mm, P: < 0.0001), ILM-OETT (1.7 +/- 1.3 mm, P: < 0. 01), LMA (1.7 +/- 1.3 mm, P: < 0.01), FLEX-MAX (3.7 +/- 1.9 mm, P: < 0.0001), EXT-MAX (1.8 +/- 1.7, P: < 0.01), however, not for FOS-NETT (0.1 +/- 0.7 mm). Posterior displacement was less for the ILM-OETT and LMA than for the ETC (both P: < 0.04). There were no significant increases in segmental sagittal motion with any airway manipulation other than with FLEX-MAX (-4.5 +/- 4.0 degrees, P: < 0.01). Posterior displacement was similar to FLEX-MAX for the OETT and ETC; however, it was less for the FM, FOS-NETT, ILM-OETT, and LMA (all P: < 0.01). Posterior displacement was similar to EXT-MAX for all airway manipulations other than for FOS-NETT (P: < 0.001). For cervical motion and the techniques tested, the safest method of airway management in a patient with a posteriorly destabilized C-3 segment is FOS-NETT. LMA devices may be preferable to the ETC.

IMPLICATIONS

In the cadaver model of a destabilized third cervical vertebrae, significant displacement of the injured segment occurs during airway management with the face mask, laryngoscope-guided oral intubation, the esophageal tracheal Combitube (Kendall-Sheridan, Neustadt, Germany), the intubating and standard laryngeal mask airway; but not with fiberscope-guided nasal intubation. For cervical motion and the techniques tested, the safest airway technique with this injury is fiberscope-guided nasotracheal intubation. Laryngeal mask devices are preferable to the esophageal tracheal Combitube.

Does efficacy of seal and fibreoptic view change during anaesthesia with the laryngeal mask airway: a comparison of oxygen and oxygen-nitrous oxide gas mixtures

BACKGROUND

We test the hypothesis that oropharyngeal leak pressure (OLP) and fibreoptic position (FP) are stable for the laryngeal mask airway (LMA) during anaesthesia with and without nitrous oxide.

METHODS

Forty paralysed anaesthetised patients (ASA 1-2, aged 18-80) were randomly allocated to receive 100% oxygen (O2 group) or 33% oxygen in nitrous oxide (O2-N2O group) for maintenance. In vivo intracuff pressure (CP) using a size 5 LMA was adjusted to 60 cm H2O. OLP, FP and CP were measured every 5 min for 30 min.

RESULTS

CP was higher in the O2-N2O group than the O2 group, other than at time zero (all: P<0.0001). CP increased every 5 min in the O2-N2O group (all: P<0.0001), but not in the O2 group. There were no differences in OLP and FP between groups at any time. There were no significant changes in OLP or FP with time within each group. There were no changes in OLP greater than 1.5 cm H2O and no change in FP for any patient.

CONCLUSION

We conclude that OLP and FP are stable for the LMA during anaesthesia lasting 30 min with or without nitrous oxide.

Does the ProSeal laryngeal mask airway prevent aspiration of regurgitated fluid?

In this randomized, cross-over cadaver study, we determined whether a new airway device, the ProSeal laryngeal mask airway (PLMA; Laryngeal Mask Company, Henley-on-Thames, UK), prevents aspiration of regurgitated fluid. We studied five male and five female cadavers (6-24 h postmortem). The infusion set of a pressure-controlled, continuous flow pump was inserted into the upper esophagus and ligated into place. Esophageal pressure (EP) was increased in 2-cm H(2)O increments. This was performed without an airway device (control) and over a range of cuff volumes (0-40 mL) for the classic laryngeal mask airway (LMA), the PLMA with the drainage tube clamped (PLMA clamped) and unclamped (PLMA unclamped). The EP at which fluid was first seen with a fiberoptic scope in the hypopharynx (control), above or below the cuff, or in the drainage tube, was noted. Mean EP at which fluid was seen without any airway device was 9 (range 8-10) cm H(2)O. EP at which fluid was seen was always higher for the PLMA clamped and LMA compared with the control (all, P<0.0001). The mean EP at which fluid was seen for the PLMA unclamped was similar to the control at 10 (range 8-13) cm H(2)O. For the PLMA unclamped, fluid appeared from the drainage tube in all cadavers at 10-40 mL cuff volume and in 8 of 10 cadavers at zero cuff volume. Mean EP at which fluid was seen above the cuff was similar for the PLMA clamped and LMA at 0-30 mL cuff volume, but was higher for PLMA clamped at 40-mL cuff volume (81 vs 48 cm H(2)O, P = 0.006). Mean EP at which fluid was seen below the cuff was similar at 0-10 mL cuff volume, but was higher for the PLMA clamped at 20, 30, and 40 mL cuff volume (62, 68, 73 vs. 46, 46, 46 cm H(2)O, respectively, P<0.04). For the PLMA clamped and the LMA, fluid appeared simultaneously above and below the cuff at all cuff volumes. We concluded that in the cadaver model, the correctly placed PLMA allows fluid in the esophagus to bypass the pharynx and mouth when the drainage tube is open. Both the LMA, and PLMA with a closed drainage tube, attenuate liquid flow between the esophagus and pharynx. This may have implications for airway protection in unconscious patients.

Effect of low-dose citrate anticoagulation on the clinical safety and efficacy of direct adsorption of lipoproteins (DALI apheresis) in hypercholesterolemic patients: a prospective controlled clinical trial

Direct adsorption of lipoproteins (DALI) is the first lipid apheresis system compatible with whole blood with the advantage of a very simple procedure. A mixture of heparin plus citrate (ACD-A) is used for the anticoagulation regimen (AR). A clinical, prospective, controlled crossover study was performed to test the safety and efficacy of low-dose citrate (LDC) anticoagulation in DALI. Five chronic DALI patients suffering from coronary heart disease and hypercholesterolemia underwent 3 DALI sessions each using the LDC anticoagulation regimen (60 IU heparin/kg body weight as initial bolus; 1:40 ACD-A: blood as perfusion). This was compared to 3 sessions per patient with the standard AR (bolus of 20 IU heparin/kg, 1:20 ACD-A as perfusion). Patient blood volumes (1.6; average of 7,040 ml) were treated with 750 ml adsorber gel per session at a blood flow rate of 60 ml/min. Mean LDL and Lp(a) reductions exceeded 60% with both AR. No clinical side effects were observed. Both AR controlled the coagulation well as evidenced by a sufficient prolongation of the partial prothrombin time (PTT) and activated clotting time as well as low thrombin-antithrombin (TAT) formation. Biocompatibility parameters exhibited favorable results (low activation of complement and cells, and only slight formation of C3a, C5a, beta-thromboglobulin, elastase, and TNF-alpha). The asymptomatic bradykinin generation was comparable in both study arms. LDC optimized the ionized calcium levels and pH in the efferent blood postadsorber. LDC anticoagulation was safe and effective, and may further improve the tolerance of DALI apheresis in hypercholesterolemic patients.

A pilot study of left tracheal pulse oximetry

We tested the hypothesis that left tracheal pulse oximetry (SpO(2)) is more accurate than finger SpO(2) when compared with oxygen saturation from arterial blood samples (SaO(2)) in anesthetized patients with normal thoracic anatomy. We also tested the hypothesis that tracheal oximetry readings are primarily derived from the tracheal mucosa. We studied 20 hemodynamically stable, well oxygenated, anesthetized patients with normal anatomy (ASA physical status I-III, 18-80 yr old). A single-use pediatric pulse oximeter was attached to the left lateral surface of a tracheal tube cuff. Tracheal and finger SpO(2) (dominant index finger), and SaO(2) (nondominant radial artery) were taken with the intracuff pressure at 0-60 cm H(2)O. Tracheal SpO(2) was the same as SaO(2) at an intracuff pressure of 10-60 cm H(2)O, but was less when the intracuff pressure was zero (P<0.0001). Tracheal SpO(2) was higher than finger SpO(2) at an intracuff pressure of 10-60 cm H(2)O (all: P <0.001), but was lower when the intracuff pressure was zero (P< 0.0001). SaO(2) was always higher than finger SaO(2) (P<0.0001). Tracheal SpO(2) was lower at an intracuff pressure of zero (P< 0.0001), but was otherwise similar over the range of intracuff pressures. SaO(2) and finger SpO(2) did not vary with intracuff pressure. Tracheal SpO(2) agrees more closely with SaO(2) than finger SpO(2) at an intracuff pressure of 10-60 cm H(2)O (mean difference < 0.2%). We conclude that left tracheal SpO(2) is feasible and provides similar readings to arterial blood samples and more accurate readings than finger oximetry in hemodynamically stable, well oxygenated, anesthetized patients with normal thoracic anatomy. Tracheal oximetry readings are not primarily derived from the tracheal mucosa. The technique merits further evaluation.

Successful pharyngeal pulse oximetry in low perfusion states

PURPOSE

We describe pharyngeal oximetry with the laryngeal mask airway in two patients with low perfusion states where finger oximetry failed.

CLINICAL FEATURES

One patient was a 47-yr-old man with septic shock and the other a 64-yr-old man with multiorgan failure. In both patients, a # 4 laryngeal mask airway with a pediatric pulse oximeter probe was inserted behind the tracheal tube. A good waveform was obtained and oxygen saturation was 0-2% lower than arterial samples.

CONCLUSION

Pharyngeal oximetry with the laryngeal mask airway is feasible in low perfusion states when finger oximetry fails.

Continuous positive airway pressure at 10 cm H(2)O during cardiopulmonary bypass improves postoperative gas exchange

Postbypass pulmonary dysfunction including atelectasis and increased shunting is a common problem in the intensive care unit. Negative net fluid balance and continuous positive airway pressure (CPAP) have been used to reduce the adverse effects of cardiopulmonary bypass (CPB) on the lung. To determine whether CPAP at 10 cm H(2)O during CPB results in improved postoperative gas exchange in comparison with deflated lungs during CPB, we examined 14 patients scheduled for elective cardiac surgery. Seven patients received CPAP at 10 cm H(2)O during CPB, and in the other seven patients, the lungs were open to the atmosphere (control). Measurements were taken before and after CPB, after thoracic closure, and 4 h after CPB in the intensive care unit. CPAP at 10 cm H(2)O resulted in significantly more perfusion of lung areas with a normal ventilation/perfusion distribution (V(A)/Q) and significantly less shunt and low V(A)/Q perfusion 4 h after CPB in comparison with the control group. Consequently, arterial oxygen partial pressure was significantly higher and alveolar-arterial oxygen partial pressure difference was significantly smaller. We conclude that CPAP at 10 cm H(2)O during CPB is a simple maneuver that improves postoperative gas exchange.

IMPLICATIONS

Inflation of the lungs at a pressure of 10 cm H(2)O as compared with leaving the lungs deflated during cardiopulmonary bypass was examined. Lung inflation during bypass resulted in significantly improved postoperative gas exchange.

Performance of the size 5 laryngeal mask airway in males and females

We compare the functional performance (ease of insertion, oropharyngeal leak pressure and anatomic position) of the size 5 LMA in males and females over a range of cuff volumes. We also determine 1) if age, height, weight and body mass index predict functional performance and 2) the relationship between oropharyngeal leak pressure (OLP) and anatomic position (judged by fibreoptic scoring). One hundred male and one hundred female paralysed, anaesthetised patients were studied. The number of insertion attempts and time to placement were recorded. OLP and fibreoptic score (FOS) were measured during inflation of the cuff from 0-40 ml in 10 ml increments. There were no failed insertions. Insertion times were similar for males and females. There were no differences in OLP or FOS between males and females at any cuff volume. For males, OLP increased from 0 to 10 ml and 10 to 20 ml (p < 0.001), but was unchanged from 20 to 30 and 30 to 40 ml. For females, OLP increased from 0 to 10 ml, 10 to 20 ml (p < 0.001) and decreased from 20 to 30 ml (p = 0.02), but was unchanged from 30 to 40 ml. For males, FOS increased from 0 to 10 ml (p = 0.02) and 10 to 20 ml (p < 0.001), but was unchanged from 20 to 30 and 30 to 40 ml. For females, FOS increased from 0 to 10 ml (p = 0.02), 10 to 20 ml (p < 0.001), decreased from 20 to 30 ml (p = 0.001), but was unchanged from 30 to 40 ml. There was a significant positive correlation with height and OLP in males and females at higher cuff volumes, but no correlation with any other variable. There was no correlation between OLP and FOS at any cuff volume for males, but there was a correlation at 0 (p = 0.03) and 10 ml (p = 0.01) for females. We conclude that ease of insertion, efficacy of seal and anatomic position for the size 5 LMA is similar in males and females. Age, weight and body mass index do not predict performance, but efficacy of seal improves with increasing patient height. Fiberoptically determined anatomic position is a poor predictor of efficacy of seal. The shape of the pharynx may be different between tall and short adults.

Mucosal pressure and oropharyngeal leak pressure with the ProSeal versus laryngeal mask airway in anaesthetized paralysed patients

The ProSeal laryngeal mask airway (PLMA) is a new laryngeal mask device with a larger, wedge-shaped cuff and a drainage tube. We tested the hypothesis that directly measured mucosal pressure and oropharyngeal leak pressure (OLP) are higher for the PLMA compared with the laryngeal mask airway (LMA). We also assess the mechanism of seal, and the reliability of cuff volume, in vivo intracuff pressure and calculated mucosal pressure (in vivo minus in vitro intracuff pressure) to predict directly measured mucosal pressure. Thirty-two anaesthetized, paralysed adult patients were randomly allocated to receive either a size 4 LMA or PLMA. Microchip sensors were attached at locations corresponding to: (a) base of tongue; (b) distal oropharynx; (c) hypopharynx; (d) lateral pharynx; (e) posterior pharynx; and (f) pyriform fossa. In vitro and in vivo intracuff pressures, OLP and directly measured mucosal pressure were documented at zero volume and after each 10 ml up to 40 ml. Directly measured mucosal pressure was similar between devices for a given cuff volume, but was lower for the PLMA for a given OLP. Directly measured mucosal pressure was highest in the distal oropharynx for both devices, but rarely (< 5%) exceeded 35 cm H2O. OLP was higher for the PLMA at all cuff volumes. Directly measured mucosal pressure was usually lower than OLP for both devices, and there was a positive correlation between directly measured mucosal pressure and OLP. Cuff volume, in vivo intracuff pressure and calculated mucosal pressure were poor to moderate predictors of directly measured mucosal pressure for the LMA and PLMA. We conclude that the PLMA forms a better seal than the LMA without an increase in directly measured mucosal pressure.

The intubating laryngeal mask airway: effect of handle elevation on efficacy of seal, fibreoptic position, blind intubation and airway protection

We conducted three studies to test the hypothesis that elevation of the intubating laryngeal mask (ILM) handle increases efficacy of seal, changes fibreoptic position, prevents aspiration of regurgitated fluid and improves intubation. In study 1, the ILM was inserted into 20 paralysed, anaesthetized patients and 20 cadavers. Oropharyngeal leak pressure and fibreoptic position were measured at an intracuff pressure of 0, 60 and 120 cm H2O with 0, 20 and 40 N of elevation force. In study 2, the oesophageal pressure at which regurgitation and aspiration occurred was measured in 20 cadavers with the ILM at the above intracuff pressures and elevation forces and 10 cadavers without the ILM (controls). In study 3, ease of blind intubation (first attempt only) was determined in 20 paralysed, anaesthetized patients at 0 and 40 N elevation force. In study 1, there was a significant increase in oropharyngeal leak pressure with increasing elevation force at an intracuff pressure of 0 and 60 cm H2O. There were no changes in fibreoptic position. Oropharyngeal leak pressure and fibreoptic position were similar between patients and cadavers. In study 2, oesophageal pressure for regurgitation and aspiration was usually greater for the ILM than controls (all: P < 0.05. Aspiration and regurgitation usually occurred at the same oesophageal pressure. In study 3, blind intubation was more successful at 0 N than 40 N (15/20 v 8/20, P = 0.03). We conclude that elevation of the ILM handle has little clinical utility other than as a temporary measure to improve the efficacy of the seal.

Physical activity maintenance in elders with cardiac problems

Clinicians who work with elderly people after acute cardiac events need strategies to facilitate the continuance of physical activity learned in cardiac rehabilitation programs. This exploratory study examined three factors related to this maintenance in 31 men and women: self-efficacy, stages of change, and social support for exercise. Self-efficacy was significantly correlated to stages of change and physical activity. Clinicians can use these factors to develop strategies to enhance the maintenance of exercise in elders with cardiac problems.

The ProSeal laryngeal mask airway: A randomized, crossover study with the standard laryngeal mask airway in paralyzed, anesthetized patients

BACKGROUND

The ProSeal laryngeal mask airway (PLMA) is a new laryngeal mask device with a modified cuff to improve seal and a drainage tube to provide a channel for regurgitated fluid and gastric tube placement. In the present randomized, crossover study, the authors tested the hypothesis that ease of insertion, airway sealing pressure, and fiberoptic position differ between the PLMA and the standard laryngeal mask airway (LMA). For the PLMA, we also assess ease of gastric tube placement and the efficacy of an introducer tool.

METHODS

Sixty paralyzed, anesthetized adult patients were studied. Both devices (only size 4) were inserted into each patient in random order. Airway sealing pressure and fiberoptic position were determined during cuff inflation from 0 to 40 ml in 10-ml increments. Gastric tube insertion was attempted with the PLMA if there was no gas leak from the drainage tube. In 60 additional patients, ease of insertion for the PLMA was compared with and without an introducer.

RESULTS

First-time success rates were higher (60 of 60 vs. 52 of 60; P = 0.003) and the effective airway time shorter (9 +/- 3 s vs20 +/- 18 s; P < 0.0001) for the LMA. There were no failed uses of either device within three attempts. Airway sealing pressure was 8-11 cm H2O higher for the PLMA at all cuff volumes (P < 0.00001) and was higher in females for both devices. Fiberoptic position was better with the LMA at all cuff volumes (P < 0.00001), but vocal cord visibility was similar (LMA, 59 of 60; PLMA, 56 of 60). For the PLMA, gastric tube placement was successful in 58 of 58 patients and took 9 +/- 5 s. First-time success rates were higher (59 of 60 vs53/60; P = 0.03) and the effective airway time shorter (15 +/- 13 s vs 23 +/- 18 s; P = 0.008) with the introducer.

CONCLUSION

The PLMA is capable of achieving a more effective seal than the LMA and facilitates gastric tube placement, but it is more difficult to insert unless an introducer tool is used. When correctly positioned, the PLMA isolates the glottis from the upper esophagus with possible implications for airway protection.

Pharyngolaryngeal, neck, and jaw discomfort after anesthesia with the face mask and laryngeal mask airway at high and low cuff volumes in males and females

BACKGROUND

There is controversy over (1) the relative incidence of sore throat between the face mask (FM) and laryngeal mask airway (LMA), (2) the efficacy of LMA intracuff pressure reduction as a mechanism for minimizing sore throat, and (3) the relative incidence of sore throat with the LMA between males and females. In a randomized double-blind study, the authors compared laryngopharyngeal, neck, and jaw discomfort with the FM and LMA at high and low cuff volumes in males and females.

METHODS

Three hundred adult patients were randomly assigned to three equal-sized groups for airway management: (1) the FM, (2) the LMA with a fully inflated cuff (LMA-High), or (3) the LMA with a semi-inflated cuff (LMA-Low). Anesthesia was administered with propofol, nitrous oxide, oxygen, and isoflurane. In the FM group, a Guedel-type oropharyngeal airway and jaw thrust were used only if necessary. In the LMA groups, cuff inflation was achieved with either 15 or 30 ml for the size 4 (females) and 20 or 40 ml for the size 5 (males). The LMA was removed when the patient was awake. Patients were questioned 18-24 h postoperatively about surgical pain, sore throat, sore neck, sore jaw, dysphonia, and dysphagia, and about whether they were satisfied with their anesthetic.

RESULTS

The incidence of sore throat was lower in the FM (8%) than the LMA-High (42%) and LMA-Low (20%) groups (both: P < or = 0.02). The incidence of sore neck was higher for the FM (14%) than the LMA-High group (6%; P = 0.05) but similar to the LMA-Low group (8%). The incidence of sore jaw was higher in the FM (11%) than the LMA-High (3%) and LMA-Low (3%) groups (both: P = 0. 02). There were no differences among groups for surgical pain or dysphonia. The incidence of dysphagia was lower in the FM (1%) than the LMA-High group (11%; P = 0.003), but similar to the LMA-Low group (1%). The incidence of sore throat and dysphagia was lower in the LMA-Low group than the LMA-High group for both males and females (all: P < or = 0.04). There were no differences in discomfort levels between males and females in any group. Two patients from the FM group and one from the LMA-High group were not satisfied with their anesthetic. These complaints were unrelated to postoperative morbidity.

CONCLUSION

The LMA causes more sore throat and dysphagia but less jaw pain than the FM. Sore throat and dysphagia are more common with the LMA if the initial cuff volume is high. There are no differences in discomfort levels between males and females. However, these discomforts do not influence patient satisfaction after LMA or FM anesthesia.

Pressure support ventilation versus continuous positive airway pressure with the laryngeal mask airway: a randomized crossover study of anesthetized adult patients

BACKGROUND

The authors tested the hypothesis that pressure support ventilation (PSV) provides more effective gas exchange than does unassisted ventilation with continuous positive airway pressure (CPAP) in anesthetized adult patients treated using the laryngeal mask airway.

METHODS

Forty patients were randomized to two equal-sized crossover groups, and data were collected before surgery. In group 1, patients underwent CPAP, PSV, and CPAP in sequence. In group 2, patients underwent PSV, CPAP, and PSV in sequence. PSV comprised positive end expiratory pressure set at 5 cm H2O and inspiratory pressure support set at 5 cm H2O above positive end expiratory pressure. CPAP was set at 5 cm H2O. Each ventilatory mode was maintained for 10 min. The following data were recorded every minute for the last 5 min of each ventilatory mode and the average reading taken: end tidal carbon dioxide, oxygen saturation, expired tidal volume, leak fraction, respiratory rate, noninvasive mean arterial pressure, and heart rate.

RESULTS

In both groups, PSV showed lower end tidal carbon dioxide (P < 0.001), higher oxygen saturation, (P < 0.001), and higher expired tidal volume (P < 0.001) compared with CPAP. In both groups, PSV had similar leak fraction, respiratory rate, mean arterial pressure, and heart rate compared with CPAP. In group 1, measurements for CPAP were similar before and after PSV. In group 2, measurements for PSV were similar before and after CPAP.

CONCLUSION

The authors concluded that PSV provides more effective gas exchange than does unassisted ventilation with CPAP during LMA anesthesia while preserving leak fraction and hemodynamic homeostasis.

Airway management during spaceflight: A comparison of four airway devices in simulated microgravity

BACKGROUND

The authors compared airway management in normogravity and simulated microgravity with and without restraints for laryngoscope-guided tracheal intubation, the cuffed oropharyngeal airway, the standard laryngeal mask airway, and the intubating laryngeal mask airway.

METHODS

Four trained anesthesiologist-divers participated in the study. Simulated microgravity during spaceflight was obtained using a submerged, full-scale model of the International Space Station Life Support Module and neutrally buoyant equipment and personnel. Customized, full-torso manikins were used for performing airway management. Each anesthesiologist-diver attempted airway management on 10 occasions with each device in three experimental conditions: (1) with the manikin at the poolside (poolside); (2) with the submerged manikin floating free (free-floating); and (3) with the submerged manikin fixed to the floor using a restraint (restrained). Airway management failure was defined as failed insertion after three attempts or inadequate device placement after insertion.

RESULTS

For the laryngoscope-guided tracheal intubation, airway management failure occurred more frequently in the free-floating (85%) condition than the restrained (8%) and poolside (0%) conditions (both, P < 0.001). Airway management failure was similar among conditions for the cuffed oropharyngeal airway (poolside, 10%; free-floating, 15%; restrained, 15%), laryngeal mask airway (poolside, 0%; free-floating, 3%; restrained, 0%), and intubating laryngeal mask airway (poolside, 5%; free-floating, 5%; restrained, 10%). Airway management failure for the laryngoscope-guided tracheal intubation was usually caused by failed insertion (> 90%), and for the cuffed oropharyngeal airway, laryngeal mask airway, and intubating laryngeal mask airway, it was always a result of inadequate placement.

CONCLUSION

The emphasis placed on the use of restraints for conventional tracheal intubation in microgravity is appropriate. Extratracheal airway devices may be useful when restraints cannot be applied or intubation is difficult.

Emergence characteristics and postoperative laryngopharyngeal morbidity with the laryngeal mask airway: a comparison of high versus low initial cuff volume

In this study we tested the hypothesis that the initial cuff volume of the laryngeal mask airway influences emergence characteristics and postoperative laryngopharyngeal morbidity. One hundred and sixty adult patients undergoing minor surgery were randomly assigned for airway management with the laryngeal mask airway with either a fully inflated cuff (LMA-High) or a semi-inflated cuff (LMA-Low). Anaesthesia was with propofol, nitrous oxide, oxygen and isoflurane. Following insertion, the cuff was inflated with either 15 or 30 ml for the size 4 (females) and 20 or 40 ml for the size 5 (males). At the end of surgery, a blinded observer documented the presence or absence of adverse airway events (hypoxia, hypercapnea, coughing, retching, regurgitation/vomiting, airway obstruction, hypoventilation, hiccupping, biting, body movement or shivering) during every 1 min epoch and cardiorespiratory variables (heart rate, mean blood pressure, arterial oxygen saturation, end-tidal carbon dioxide and respiratory rate) every 5 min until the patient was awake and the laryngeal mask airway removed. Patients were interviewed about pharyngolaryngeal morbidity (sore throat, dysphonia and dysphagia) immediately before leaving the postanaesthesia care unit and 18-24 h following surgery. Analysis by epoch showed more partial airway obstruction in the LMA-High group, but analysis by patient numbers revealed no difference. Heart rate was slightly higher in the LMA-High group upon arrival in the postanaesthesia care unit, but otherwise there were no differences in cardiorespiratory responses. Sore throat and dysphagia were more common in the LMA-High group. We conclude that, in general, emergence characteristics with the laryngeal mask airway are not influenced by the volume of air used to inflate the cuff, but that postoperative sore throat and dysphagia are more likely at high initial cuff volumes.

Smoking does not alter the dose-requirements and the pharmacodynamics of rocuronium

PURPOSE

Controversial data about the effect of smoking on the dose-requirements and the pharamcodynamics of rocuronium have been reported recently. This study was conducted to evaluate the dose-requirements and the pharmacodynamics of rocuronium in smokers using target controlled infusion.

METHODS

The dose-requirements of rocuronium for 60 min relaxation, using target controlled infusion, given under intravenous anaesthesia with propofol, fentanyl and nitrous oxide was studied in 37 smokers and 37 non-smokers. Initially 450 microg x kg(-1) rocuronium were administered, neuromuscular effects were quantified by recording the single twitch response of the adductor pollicis muscle after ulnar nerve stimulation using a force transducer, and the neuromuscular block was kept at 80% by target controlled infusion throughout the procedure.

RESULTS

The dose-requirements for one hour relaxation were 867 +/- 116 microg x kg(-1) x hr(-1) for smokers (S) and 839 +/- 149 microg x kg(-1) x hr(-1) for non-smokers (NS). The duration to 10% and the spontaneous recovery from 25% to 75% of the control twitch response also showed no differences between S (17.2 +/- 3.4 min, 10.6 +/- 0.9 min) and NS (18.9 +/- 4.3 min, 10.9 +/- 3.2 min), as well as maximum block, onset time and infusion rate.

CONCLUSION

Smoking does not alter the dose-requirements for rocuronium and no effects on the onset time, degree of block, time to maximum block, duration 10% and spontaneous recovery index were observed.