New ventilators for the ICU--usefulness of lung performance reporting

A Possible, Non-Invasive Method of Measuring Dynamic Lung Compliance in Patients with Interstitial Lung Disease Using Photoplethysmography

BACKGROUND

Measuring lung compliance is useful for evaluating progression of interstitial lung disease (ILD), because reduced lung compliance due to fibrosis progression is the main cause of decreased vital capacity. However, because insertion of a balloon into the esophagus is invasive, lung compliance is rarely measured. A recently developed method uses fingertip photoplethysmography to estimate intrathoracic pressure. This method non-invasively measures lung dynamic compliance (Cdyn) by simultaneously measuring tidal volume. We evaluated the efficacy of this method in assessing ILD.

METHODS

This single-center, cross-sectional, observational study evaluated the efficacy of this method in patients with ILD and healthy controls. The primary outcome was estimated Cdyn (eCdyn), as determined with this method. We also evaluated baseline characteristics that are potential confounding factors for eCdyn.

RESULTS

Median eCdyn was significantly lower in the ILD group (n = 14) than in the control group (n = 49) (0.122 vs. 0.183; P = 0.011). In univariate regression analysis, eCdyn was significantly correlated with height, weight, forced vital capacity, forced expiratory volume in 1 second, diffusing capacity for carbon monoxide, and usual interstitial pneumonia. In multivariate regression analysis, weight (β = 0.49, P = 0.011) and usual interstitial pneumonia (β = 0.52, P = 0.007) were significantly correlated with eCdyn.

CONCLUSIONS

Using photoplethysmography, we noted a significant reduction in Cdyn in patients with ILD. This novel non-invasive method is a promising tool for evaluating fibrosis progression in ILD.

Advanced Modes of Mechanical Ventilation: Introduction for the Critical Care Pharmacist

Mechanical ventilation continues to be an evolving modality in the critical care environment. Technological advances in microprocessor-controlled ventilation integrated with the complexity of new ventilator modes has provided the multidisciplinary team opportunities to further improve the care of the critically ill ventilator patients. As members of the critical care multidisciplinary team, pharmacists require a basic understanding of both conventional and advanced modes of mechanical ventilation in order to assist in optimizing medication use and ultimately patient health-care outcomes. Pharmacists have a key responsibility to practice vigilance to maintain safe drug therapy use by preventing drug-drug or drug-disease interactions and optimal dose selection based upon pharmacokinetics and pharmacodynamics principles. Pharmacists also assist in the development of drug utilization guidelines and pharmacological ventilator-weaning protocols based upon evidence-based practice. The result of these responsibilities must include the continued longitudinal assessment and reporting of quality measures to assess ventilator weaning, time to liberation of mechanical ventilation, and length of care in intensive care unit. The purpose of this article is to provide the clinical pharmacist a guide to a basic understanding of advanced modes of mechanical ventilation in adults and to apply the knowledge gained to assist in the care of the critical care patients.

Diagnosis and conservative management of late tracheotomy complications in chronic ventilator-dependent patients

BACKGROUND

Complications associated with long-term tracheotomy are obstruction of the distal end of the tube by granulation tissue and tracheomalacia. These complications have traditionally been surgically treated.

METHODS

Prospective study in a chronic ventilator-dependent division, including 234 consecutive patients with tracheotomy and mechanical ventilation. Endoscopic evaluation was performed in patients in whom there was respiratory distress with difficulty in passing a suction catheter through the tube, and/or increased inspiratory resistance and increased peak inspiratory pressure.

RESULTS

Nineteen patients were diagnosed with granulation or tracheomalacia. Two patients were treated by surgical removal of the obstructing tissue. Nonsurgical patients were conservatively managed with symptoms' resolution by bypassing the pathology with a longer tube than the previous one or by an adjustable flange tube under endoscopic visualization, with a median symptom-free period of 433 days (range, 55-1230 days).

CONCLUSION

In nonsurgical candidates, insertion of a longer tube is a conservative and feasible long-term treatment.

Dynamic and quasi-static lung mechanics system for gas-assisted and liquid-assisted ventilation

Our aim was to develop a computerized system for real-time monitoring of lung mechanics measurements during both gas and liquid ventilation. System accuracy was demonstrated by calculating regression and percent error of the following parameters compared to standard device: airway pressure difference (Delta P(aw)), respiratory frequency (f(R) ), tidal volume (V(T)), minute ventilation (V'(E)), inspiratory and expiratory maximum flows (V'(ins,max), V'(exp,max)), dynamic lung compliance (C(L,dyn) ), resistance of the respiratory system calculated by method of Mead-Whittenberger (R(rs,MW)) and by equivalence to electrical circuits (R(rs,ele)), work of breathing (W(OB)), and overdistension. Outcome measures were evaluated as function of gas exchange, cardiovascular parameters, and lung mechanics including mean airway pressure (mP(aw)). Delata P(aw), V(T), V'(ins,max), V'(exp,max), and V'(E) measurements had correlation coefficients r = 1.00, and %error < 0.5%. f(R), C(L,dyn), R(rs,MW), R(rs,ele), and W(OB) showed r > or = 0.98 and %error < 5%. Overdistension had r = 0.87 and %error < 15%. Also, resistance was accurately calculated by a new algorithm. The system was tested in rats in which lung lavage was used to induce acute respiratory failure. After lavage, both gas- and liquid-ventilated groups had increased mP(aw) and W(OB), with decreased V(T), V'(E), C(L,dyn), R(rs,MW), and R(rs,ele) compared to controls. After 1-h ventilation, both injured group had decreased V(T), V'(E) , and C(L,dyn), with increased mP(aw), R(rs,MW), R(rs,ele), and W(OB) . In lung-injured animals, liquid ventilation restored gas exchange, and cardiovascular and lung functions. Our lung mechanics system was able to closely monitor pulmonary function, including during transitions between gas and liquid phases.