A Systematic Review of the Clinimetric Properties of the 6-Item Version of the Hamilton Depression Rating Scale (HAM-D6)

BACKGROUND

In a study aimed at identifying the items carrying information regarding the global severity of depression, the 6-item Hamilton Depression Rating Scale (HAM-D6) was derived from the original 17-item version of the scale (HAM-D17). Since then, the HAM-D6 has been used in a wide range of clinical studies. We now provide a systematic review of the clinimetric properties of HAM-D6 in comparison with those of HAM-D17 and the Montgomery Asberg Depression Rating Scale (MADRS).

METHODS

We conducted a systematic search of the literature in PubMed, PsycInfo, and EMBASE databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline. Studies reporting data on the clinimetric validity of the HAM-D6 and either the HAM-D17 or MADRS in non-psychotic unipolar or bipolar depression were included in the synthesis.

RESULTS

The search identified 681 unique records, of which 51 articles met the inclusion criteria. According to the published literature, HAM-D6 has proven to be superior to both HAM-D17 and MADRS in terms of scalability (each item contains unique information regarding syndrome severity), transferability (scalability is constant over time and irrespective of sex, age, and depressive subtypes), and responsiveness (sensitivity to change in severity during treatment).

CONCLUSIONS

According to the published literature, the clinimetric properties of HAM-D6 are superior to those of both the HAM-D17 and MADRS. Since the validity of HAM-D6 has been demonstrated in both research and clinical practice, using the scale more consistently would facilitate translation of results from one setting to the other.

Validation and clinical feasibility of nitrogen washin/washout functional residual capacity measurements in children

BACKGROUND

The functional residual capacity (FRC) is an important parameter in pediatric respiratory monitoring but it is difficult to assess in the clinical setting. We have introduced a modified N(2) washout method utilizing a change of F(I)O(2) of 0.1 for FRC measurement in adult respiratory monitoring. This study validated the algorithm in a pediatric lung model and investigated the stability and feasibility in a pediatric peri-operative and intensive care setting.

METHODS

The lung model was ventilated in combinations of ventilatory modes, CO(2) production, model FRC and respiratory rates. Sixteen children from 10 days to 5 years were studied peri-operatively with controlled ventilation using a Mapleson D system and in the intensive care unit using a Servo-i ventilator in a supported spontaneous mode. FRC was measured during stable metabolic, respiratory and circulatory periods at positive end expiratory pressure of 3-4 and 7-8 cmH(2)O.

RESULTS

In the model and in the clinical setting, we found an excellent agreement between washout and washin measurements of FRC as well as acceptable coefficients of repeatability.

CONCLUSION

FRC was satisfactorily measured by a modified N(2) algorithm and may be included as a monitoring variable in pediatric respiratory care. Pediatric FRC monitoring demands strictly stable conditions as measurements are performed close to the limits of the monitor's specifications.

Dead-space reduction and tracheal pressure measurements using a coaxial inner tube in an endotracheal tube

OBJECTIVE

To evaluate the effects on CO(2) washout of the coaxial double lumen tube (DLT) as compared to a standard endotracheal tube (ETT) and tracheal gas insufflation (TGI). Precision of tracheal pressure monitoring through the DLT and safety issues, including intrinsic PEEP (PEEPi) formation during DLT ventilation, were also evaluated.

DESIGN

Lung model study.

SETTING

University research laboratory.

MEASUREMENTS AND RESULTS

CO(2) washout was analysed in a lung model by measuring single alveolar CO(2) concentration during DLT ventilation as compared to standard ETT ventilation, at different minute ventilation (6-14 l/min) and different CO(2)-output levels (180 ml/min, 240 ml/min, and 300 ml/min). At a CO(2) output level of 240 ml/min the CO(2) washout was also compared to tidal volume-adjusted continuous TGI and expiratory synchronised TGI. Precision of tracheal pressure monitoring and PEEPi formation during DLT ventilation was evaluated by comparing pressure in each limb above the tube to reference tracheal pressure, varying I:E ratios (1:2, 1:1, and 2:1), tidal volumes (300-700 ml), breathing frequencies (15-25), and compliance (20-50 ml/cmH(2)O). DLT ventilation had the same efficacy in removing CO(2) as continuous and expiratory synchronised TGI, reducing single alveolar CO(2) concentration by 9-21% compared to normal ventilation. Tracheal pressure could be measured through the DLT with high precision. There was only marginal formation of PEEPi at tidal volumes <or=600 ml, I:E ratio <or=1:1, and compliance <or=35 ml/cmH(2)O.

CONCLUSIONS

The double lumen tube is as effective as tracheal gas insufflation in reducing CO(2) tension. Tracheal pressure and formation of PEEPi can be monitored with high precision without interrupting ventilation.

Monitoring functional residual capacity (FRC) by quantifying oxygen/carbon dioxide fluxes during a short apnea

BACKGROUND

Clinically applicable methods for measuring FRC are currently lacking. This study presents a new method for FRC monitoring based on quantification of metabolic gas fluxes of O2 and CO2 during a short apnea.

METHODS

Base line exchange of oxygen and carbon dioxide was measured with indirect calorimetry. End-tidal ( approximately alveolar) O2 and CO2 concentrations were measured before and after a short apnea, 8-12 s, and FRC was calculated according to standard washin/washout formulas taking into account the increased solubility of CO2 in blood when the tension is increased during the apnea. The method was tested in a lung model with CO2 excretion and O2 consumption achieved by combustion of hydrogen and implemented in six ventilator-treated patients with acute respiratory failure (ARF).

RESULTS

In the lung model the method showed excellent correlation (r = 0.98) with minimal bias (34 ml) and a good precision, limits of agreement being 160 and -230 ml, respectively, compared to the reference method. In six ARF patients changes in FRC induced by increase or decrease in PEEP and measured with the O2/CO2 flux FRC method corresponded well with changes in reference values of FRC (r = 0.76-0.94).

CONCLUSIONS

A new method has been proposed in which FRC could be monitored from measurements of physiological fluxes of gases during a short apnea with the use of standard ICU equipment and some calculations. We anticipate that with further development, this technique could provide a new tool for monitoring respiratory changes and ventilator management in the ICU.

Continuous on-line measurements of respiratory system, lung and chest wall mechanics during mechanic ventilation

OBJECTIVE

We present a concept of on-line, manoeuvre-free monitoring of respiratory mechanics during dynamic conditions, displaying calculated alveolar pressure/volume curves continuously and separating lung and chest wall mechanics.

DESIGN

Prospective observational study.

SETTING

Intensive care unit of a university hospital.

PATIENTS

Ten ventilator-treated patients with acute lung injury.

INTERVENTIONS

Different positive end-expiratory pressure (PEEP) and tidal volumes, low flow inflation.

MEASUREMENTS AND RESULTS

Previously validated methods were used to present a single-value dynostatic compliance for the whole breath and a dynostatic volume-dependent initial, middle and final compliance within the breath. A high individual variation of respiratory mechanics was observed. Reproducibility of repeated measurements was satisfactory (coefficients of variations for dynostatic volume-dependent compliance: < or =9.2% for total respiratory system, < or =18% for lung). Volume-dependent compliance showed a statistically significant pattern of successively decreasing compliance from the initial segment through the middle and final parts within each breath at all respiratory settings. This pattern became more prominent with increasing PEEP and tidal volume, indicating a greater distension of alveoli. No lower inflection point (LIP) was seen in patients with respiratory rate 20/min and PEEP at 4 cmH2O. A trial with low flow inflation in four of the patients showed formation of a LIP in three of them and an upper inflection in one.

CONCLUSIONS

The monitoring concept revealed a constant pattern of successively decreasing compliance within each breath, which became more prominent with increasing PEEP and tidal volume. The monitoring concept offers a simple and reliable method of monitoring respiratory mechanics during ongoing ventilator treatment.

Direct tracheal airway pressure measurements are essential for safe and accurate dynamic monitoring of respiratory mechanics. A laboratory study

BACKGROUND

All monitoring of respiratory mechanics should depend on tracheal pressures (Trach-P) as endotracheal tube resistance (ETT-Res) will otherwise distort them. The aim of this study was to investigate factors that may vary ETT-Res, causing difficulties in ETT-Res estimation clinically, and to evaluate a method for direct Trach-P measurements to obviate these problems.

METHODS

In a model we studied: 1) The influence on ETT-Res caused by different connectors and secretions; 2) Direct Trach-P measurements with a catheter (o.d. 2 mm, i.d. 0.9 mm) with either end or side hole, filled with either air or liquid, introduced through the ETT lumen and evaluated regarding response time and position.

RESULTS

The pressure drop between trachea and Y-piece increased by 15% when respectively a swivel connector and a humidification device were connected to the ETT. When injecting 1 ml and 2 ml gel into the ETT lumen the inspiratory resistance increased 100% and 600% respectively. The response time of all catheters was < or = 12 ms. During constant flow in inspiratory and expiratory directions the pressure difference between an end hole catheter positioned from 2 cm above the ETT tip to 4 cm below and a reference pressure in the artificial trachea was less than 1.5 cmH2O.

CONCLUSIONS

ETT connections and secretions cause a variance in resistance. Tracheal pressure can be measured with high precision with an air- or liquid-filled catheter. An end hole catheter placed within 2 cm above or below the ETT tip will give sufficiently precise measurements for clinical purposes.

A new method for non-invasive, manoeuvre-free determination of "static" pressure-volume curves during dynamic/therapeutic mechanical ventilation

BACKGROUND

Lung mechanics are usually measured using static or quasistatic methods, abandoning normal ventilatory treatment. We have developed a method to calculate the alveolar pressure during dynamic/therapeutic conditions, "the dynostatic pressure" (P(dyn)), using airway pressure (P) measured in the trachea and volume (V) and flow (V) at the Y-piece.

METHODS

P(dyn) is calculated according to the formula P(dyn)= (P(insp) x V(exp)-P(exp) x V(insp))/(V(exp)-V(insp)), making the assumption that inspiratory and expiratory resistances are equal at isovolume. The method was evaluated in a lung model during dynamic conditions comparing measured alveolar pressure (P(alv)) and P(dyn) at equal and unequal inspiratory and expiratory resistances and P/V-curves obtained during static and dynamic conditions. The algorithm was then applied in patients with acute lung injury (ALI).

RESULTS

When inspiratory and expiratory resistances were equal there was an excellent agreement between the P(dyn) and the P(alv), irrespective of ventilator settings, r(2)=0.995 (range 0.981-0.999). P(dyn) derived compliance was equal to static values. When the ratio between inspiratory and expiratory resistance was varied between 2.3:1 and 1:2.3 the r(2) was above 0.95 (range 0.952-0.996). Development of intrinsic PEEP and overdistension was easily revealed in patients, as shown by the dynostatic P/V-curve.

CONCLUSION

The dynostatic method gives a breath-by-breath reflection of the interaction between ventilatory settings and lung mechanics in patients during ordinary ventilator treatment. It is only marginally affected by the moderate differences in inspiratory versus expiratory resistances present in patients with ALI.

Evaluation of pressure/volume loops based on intratracheal pressure measurements during dynamic conditions

BACKGROUND

The aim of this study was to evaluate and compare information about lung mechanics obtained by dynamic pressure/volume loops based on Y-piece and intratracheal airway pressure.

METHODS

Airway pressure was measured simultaneously at the Y-piece and trachea. Flow/tidal volume was measured by sidestream spirometry at the Y-piece. The effect of an intraluminal catheter in the tube was evaluated in a lung model. Ten adults with acute lung injury and mechanical ventilation were studied. Measurements were performed during volume-(VC) and pressure-controlled (PC) ventilation at different ventilator settings.

RESULTS

Lung model: There was a statistically significant difference (P<0.001) between trachea and Y-piece pressure/volume loop areas during both VC and PC ventilation. The ratio trachea area/Y-piece area decreased with increased endotracheal tube resistance (r=0.96).

PATIENTS

The difference between trachea and Y-piece P/V-loops was statistically significant at all 21 ventilatory settings (P<0.05-0.001). The tracheal loop revealed clearly intrinsic PEEP and lowered compliance during overinflation, which was difficult or impossible to see in the Y-piece pressure/volume loop.

CONCLUSION

By measuring airway pressure at the trachea the effect of endotracheal tube resistance during inspiration is excluded while it is included during expiration, yielding correct end-points of inspiration and expiration. This makes it possible to calculate accurately total compliance of the respiratory system during dynamic conditions. By monitoring of airway pressure in the trachea, respiratory mechanics can be assessed more accurately and ventilatory settings adjusted to attenuate ventilator induced lung injury.

Evaluation of a Pitot type spirometer in helium/oxygen mixtures

OBJECTIVE

Mixtures of helium and oxygen are regaining a place in the treatment of obstruction of the upper and lower respiratory tract. The parenchymal changes during the course of IRDS or ARDS may also benefit from the reintroduction of helium/oxygen. In order to monitor and document the effect of low-density gas mixtures, we evaluated the Datex AS/3 Side Stream Spirometry module with D-lite (Datex-Engstrom Instrumentarium Corporation, Finland) against two golden standards.

METHODS

Under conditions simulating controlled and spontaneous ventilation with gas mixtures of He (approx. 80, 50, and 20%)/O2 or N2(approx. 21 and 79%)/02, simultaneous measurements using Biotek Ventilator Tester (Bio-Tek Instr., Vermont, USA) or body plethysmograph (SensorMedics System, Anaheim, USA) were correlated with data from the spirometry module. Data were analyzed according to a statistical regression model resulting in a best-fit equation based on density, voltage, and volume measurements.

RESULTS

As expected, the D-lite (a modified Pitot tube) showed density-dependent behaviour. Regression equations and percentage deviation of estimated versus measured values were calculated.

CONCLUSION

Measurements with the D-lite using low-density gases are satisfactorily contained in best-fit equations with a standard deviation of less than 5% during all ventilatory modes and mixtures.