Biomedical subjects

Sairam Parthasarathy

Publications and source records attributed to Sairam Parthasarathy.

11 recordsLinked to original sources

PubMed2007

Mechanical ventilation: let us minimize sleep disturbances.

PURPOSE OF REVIEW: This review provides a background in mechanical ventilation and sleep. RECENT FINDINGS: Sleep pattern in mechanically ventilated patients differs largely from physiological sleep. The ventilatory mode and the ventilatory settings could have an influence on the sleep quality and quantity. Pressure support ventilation can increase the sleep fragmentation and decrease the sleep quantity, due to central apneas when compared with assist control ventilation. An excessive level of ventilatory assistance during sleep promotes central apneas and ineffective efforts. These two respiratory events can trigger arousals and awakenings, thus altering the sleep quality and quantity in mechanically ventilated patients. Ventilatory settings adjusted according to the patient's effort during pressure support allow reducing the number of ineffective efforts and improve sleep quality when compared with a clinical adjustment. A physiological approach to set the ventilator and the ventilatory mode may improve sleep quality and quantity. SUMMARY: Minimizing the sleep alterations in mechanically ventilated patients could be obtained by setting the ventilator in such a way to avoid hyperventilation during the sleep stage. The impact of sleep derangements in patient outcomes is, however, unknown.

Humans↗

PubMed2006

Nocturic frequency is related to severity of obstructive sleep apnea, improves with continuous positive airways treatment.

OBJECTIVE: The purpose of this study was to determine the relationship between nocturia and obstructive sleep apnea (OSA), and the effect of continuous positive airways pressure (CPAP) therapy on nocturic frequency. STUDY DESIGN: This was a retrospective review of sleep studies including patients with and without evidence of OSA, before and during CPAP treatment (where relevant). Chi-squared tests compared nocturia prevalence according to sleep diagnosis, logistic regression determined predictors of nocturia, and regression analyses determined predictors of nocturic frequency. RESULTS: In 196 eligible studies, predictors of nocturia included increasing age and diabetes mellitus; nocturia was equally likely to occur in patients with and without OSA. In patients with OSA and nocturia, nocturic frequency was related to age, diabetes, and severity of OSA (P < .001). Patients with OSA and nocturia who were treated with CPAP demonstrated a significant decrease in nocturic frequency (P < .001). CONCLUSION: OSA severity predicts nocturic frequency. The role of testing in the triage of patients with nocturia remains to be determined.

Adult↗

PubMed2005

Weaning prediction: esophageal pressure monitoring complements readiness testing.

Several variables are recommended for identifying if a patient is ready for a trial of weaning from mechanical ventilation, but there is no agreement as to whether monitoring any variable during the trial enhances patient management. To determine whether repeated measurements of esophageal pressure throughout a trial are more reliable than measurements of esophageal pressure or frequency-to-VT ratio during the first minute of the trial, we studied 60 patients. A trend index that quantified esophageal pressure swings over time was more reliable than the first-minute measurements: sensitivity, 0.91, and specificity, 0.89. Area under receiver operating characteristic curve for trend index (0.94) was greater than for first-minute measurement of esophageal pressure (0.44, p < 0.05) and tended to be greater than that for frequency-to-VT ratio (0.78, p = 0.13). The likelihood ratio was highest for the trend index (8.2, p < 0.05). The advantage of the trend index may be related to the progressive increase in esophageal pressure throughout a failed weaning trial, whereas breathing pattern changed little after 2 minutes of spontaneous breathing. In conclusion, continuous monitoring of esophageal pressure swings during a spontaneous breathing trial provides additional guidance in patient management over tests used for deciding when to initiate weaning.

Aged↗

PubMed2005

Effect of air leak on the performance of auto-PAP devices: a bench study.

Automatic positive airway pressure (auto-PAP) devices, used in the treatment of patients with obstructive sleep apnea (OSA), may not function optimally in the presence of an air leak. We set out to determine the magnitude of air leak that prevents auto-PAP devices from responding to respiratory events of OSA in a bench model. We simulated apnea, flow limitation, obstructive hypopnea, nonobstructive hypopnea, and snoring events of OSA with an artificial airway and a loudspeaker in a bench model connected to a commercially available auto-PAP device. Four auto-PAP devices were tested, but two of the "older-generation" devices (Tranquility and Virtuoso) did not respond to events of OSA that involved changes in flow contour; hence, we studied the effects of air leak and humidifier in the two "newer-generation" auto-PAP devices only (GoodKnight 418P, Autoset-T). When the air leak was progressively increased from baseline levels recommended by the manufacturer to levels seen clinically--5 to 7, 10, and 30 l/min--the GoodKnight 418P decreased pressure response by 56% (5.6+/-1.8 cm H(2)O, p=0.04). The pressure response of the Autoset-T, however, did not change from baseline during similar levels of air leak. The GoodKnight performed appropriately when the air leak was within 20 l/min, but the corresponding value for the Autoset was higher at 50 l/min. For both devices combined, air leak caused the pressure to drop between the device and the airway: 2.8+/-0.3 cm H(2)O at 30 l/min of air leak (p<0.001). Air leaks cause auto-PAP devices to underestimate the pressure required to treat events of OSA and to overestimate the pressure delivered at the upper airway. Physicians should be aware of performance limitations of auto-PAP devices in the presence of an air leak.

Automation↗

PubMed2005

Effects of sleep on patient-ventilator interaction.

Sleep influences patient-ventilator interaction. Adjustment of ventilator settings in critically ill patients may require understanding and monitoring of the influence of the sleep-wakefulness state on patient-ventilator interaction. Research studies of patient-ventilator interactions should be controlled for the confounding influence of changes in the sleep-wakefulness state.

Humans↗

PubMed2005

Comparison of nasal pressure transducer and thermistor for detection of respiratory events during polysomnography in children.

STUDY OBJECTIVES: The results of small studies have suggested that a nasal-cannula pressure transducer has a higher sensitivity than a thermistor in detecting hypopneas and diagnosing sleep-disordered breathing in both adults and children. We compared a thermistor alone, and in conjunction with a pressure transducer, for detection of sleep-disordered breathing in children during in-home polysomnography. DESIGN: Retrospective analysis of a subsample of a prospective cohort study. SETTING: Students attending elementary school in the Tucson Unified School District. PARTICIPANTS: A subsample of the Tucson Children's Assessment of Sleep Apnea study population. MEASUREMENTS AND RESULTS: Polysomnographic recordings of 40 children (24 girls and 16 boys, mean age 9.2 +/- 1.7 years; range 6-11 years) were analyzed to compare the detection of sleep-disordered breathing events by 2 different methods of measuring airflow: thermistor alone and thermistor with nasal-cannula pressure transducer (transducer) used simultaneously. The transducer detected all the respiratory events detected by the thermistor, but the thermistor detected only 84% of the transducer-defined events. Consequently, the transducer-derived mean respiratory disturbance index was higher than that detected by the thermistor (7.0 +/- 3.8 vs 5.9 +/- 3.4, P < .001). The bias error between transducer respiratory disturbance index and thermistor respiratory disturbance index on a Bland-Altman plot was 1.08 (95% confidence interval, 0.8 - 1.4). There was good agreement between the thermistor and the transducer for making the diagnosis of sleep apnea using a cutoff of a respiratory disturbance index greater than 5 (kappa = 0.69). The quality of the tracings with the transducer was comparable to that of the thermistor, but the transducer dislodged more frequently. CONCLUSION: The use of a nasal transducer in conjunction with a thermistor was more sensitive than the thermistor alone in detecting sleep-disordered breathing in children during unattended polysomnography.

Catheterization↗

PubMed2005

Sleep and the medical profession.

PURPOSE OF REVIEW: This review addresses the way in which sleep physiology influences the medical profession and health care delivery. RECENT FINDINGS: The training process for the medical professional has undergone dramatic changes over the past century. In recent times, however, the complexity and level of care delivered has out-stripped a trainee's ability to forego sleep and is compromising both physician and patient safety and thereby threatens the foundation of the profession. Recently, significant strides have been made in our understanding of sleep loss and consequences to physicians-in-training. Nevertheless, the implementation of changes fostered by such findings faces numerous conceptual and practical obstacles. This review updates the reader on recent evidence for changing the way medical professionals are trained, and opines on how solutions generated from such research should be embraced. Additionally, the deficiencies in our current understanding of sleep and medical training are identified so that future research can be undertaken in such areas. SUMMARY: Acknowledging the defects in our current system of training physicians and enacting further changes is sorely needed to improve patient safety and the well-being of physicians-in-training.

Clinical Competence↗

PubMed2004

Sleep during mechanical ventilation.

PURPOSE OF REVIEW: This review addresses the growing interest in the study of sleep during critical illness. RECENT FINDINGS: We know that sleep, in all of its measurable aspects, is severely deranged in critically ill patients during mechanical ventilation. There is growing evidence that mode of mechanical ventilation, medications, and acuity of illness may contribute to such sleep derangements and that conventional factors such as noise and health care delivery may be playing a much smaller role than previously thought. Alternatively, changes in sleep-wakefulness state can alter patient-ventilator interaction, which may in turn influence physicians' decision-making. Sleep organization may predict functional outcome in patients with head trauma. Additionally, there is evidence that poor sleep is an important factor influencing long-term quality of life in survivors of critical illness. SUMMARY: A more complete understanding of the etiopathogenesis of sleep derangements during mechanical ventilation may identify new interventions to help improve sleep, and possibly favorably influence short-term and long-term outcomes.

Critical Illness↗

PubMed2003

Sleep in the intensive care unit.

Abnormalities of sleep are extremely common in critically ill patients, but the mechanisms are poorly understood. About half of total sleep time occurs during the daytime, and circadian rhythm is markedly diminished or lost. Judgments based on inspection consistently overestimate sleep time and do not detect sleep disruption. Accordingly, reliable polygraphic recordings are needed to measure sleep quantity and quality in critically ill patients. Critically ill patients exhibit more frequent arousals and awakenings than is normal, and decreases in rapid eye movement and slow wave sleep. The degree of sleep fragmentation is at least equivalent to that seen in patients with obstructive sleep apnea. About 20% of arousals and awakenings are related to noise, 10% are related to patient care activities, and the cause for the remainder is not known; severity of underlying disease is likely an important factor. Mechanical ventilation can cause sleep disruption, but the precise mechanism has not been defined. Sleep disruption can induce sympathetic activation and elevation of blood pressure, which may contribute to patient morbidity. In healthy subjects, sleep deprivation can decrease immune function and promote negative nitrogen balance. Measures to improve the quantity and quality of sleep in critically ill patients include careful attention to mode of mechanical ventilation, decreasing noise, and sedative agents (although the latter are double-edged swords).

Procedural Sedation↗

PubMed2002

Is weaning failure caused by low-frequency fatigue of the diaphragm?

Because patients who fail a trial of weaning from mechanical ventilation experience a marked increase in respiratory load, we hypothesized that these patients develop diaphragmatic fatigue. Accordingly, we measured twitch transdiaphragmatic pressure using phrenic nerve stimulation in 11 weaning failure and 8 weaning success patients. Measurements were made before and 30 minutes after spontaneous breathing trials that lasted up to 60 minutes. Twitch transdiaphragmatic pressure was 8.9 +/- 2.2 cm H2O before the trials and 9.4 +/- 2.4 cm H2O after their completion in the weaning failure patients (p = 0.17); the corresponding values in the weaning success patients were 10.3 +/- 1.5 and 11.2 +/- 1.8 cm H2O (p = 0.18). Despite greater load (p = 0.04) and diaphragmatic effort (p = 0.01), the weaning failure patients did not develop low-frequency fatigue probably because of greater recruitment of rib cage and expiratory muscles (p = 0.004) and because clinical signs of distress mandating the reinstitution of mechanical ventilation arose before the development of fatigue. Twitch pressure revealed considerable diaphragmatic weakness in many weaning failure patients. In conclusion, in contrast to our hypothesis, weaning failure was not accompanied by low-frequency fatigue of the diaphragm, although many weaning failure patients displayed diaphragmatic weakness.

Adult↗

PubMed2002

Effect of ventilator mode on sleep quality in critically ill patients.

To determine whether sleep quality is influenced by the mode of mechanical ventilation, we performed polysomnography on 11 critically ill patients. Because pressure support predisposes to central apneas in healthy subjects, we examined whether the presence of a backup rate on assist-control ventilation would decrease apnea-related arousals and improve sleep quality. Sleep fragmentation, measured as the number of arousals and awakenings, was greater during pressure support than during assist-control ventilation: 79 +/- 7 versus 54 +/- 7 events per hour (p = 0.02). Central apneas occurred during pressure support in six patients; heart failure was more common in these six patients than in the five patients without apneas: 83 versus 20% (p = 0.04). Among patients with central apneas, adding dead space decreased sleep fragmentation: 44 +/- 6 versus 83 +/- 12 arousals and awakenings per hour (p = 0.02). Changes in sleep-wakefulness state caused greater changes in breath components and end-tidal CO2 during pressure support than during assist-control ventilation. In conclusion, inspiratory assistance from pressure support causes hypocapnia, which combined with the lack of a backup rate and wakefulness drive can lead to central apneas and sleep fragmentation, especially in patients with heart failure.

Carbon Dioxide↗