In vitro aerodynamic characteristics of aerosol delivered from different inhalation methods in mechanical ventilation

Can humidifier reservoir bacteria colonize the circuit during mechanical ventilation: An in vitro study

BACKGROUND

Although the circuit condensate, an ideal bacterial reservoir during mechanical ventilation, may flow into the humidifier reservoir, no studies have investigated if humidifier reservoir colonized bacteria colonize other circuit locations with airflow.

AIMS

We aimed to prove whether the humidifier reservoir colonized bacteria colonize other circuit locations with airflow and provide some advice on the disposal of condensate in the clinical setting.

STUDY DESIGN

An in vitro experiment was conducted. Mechanical ventilation simulators (n = 90) were divided into sterile water group (n = 30) and broth group (n = 60). In the sterile water group, sterile water was used for humidification, either Acinetobacter baumannii or Pseudomonas aeruginosa were inoculated to humidifier water in the humidifier reservoir, each accounted for 50% of the simulators. The broth group was performed the same as the sterile water group except for the addition of broth into the humidified water. After 24, 72, and 168 h of continuous ventilation, the humidifier water and different locations of the circuits were sampled for bacterial culture.

RESULTS

All bacterial culture results of the sterile water group were negative. Bacteria in the humidifier water continued to proliferate in the broth group. With prolonged ventilation, the bacteria at the humidifier reservoir outlet increased. The bacteria at the humidifier reservoir outlet were much more in the Pseudomonas aeruginosa subgroup than in the Acinetobacter baumannii subgroup and the difference was statistically significant (p < .05). During continuous ventilation, no bacterial growth occurred at 10 cm from the humidifier reservoir outlet and the Y-piece of the ventilator circuits.

CONCLUSIONS

Sterile water in the humidifier reservoir was not conducive to bacterial growth. Even if bacteria grew in the humidifier reservoir and could reach the humidifier reservoir outlet, colonization of further circuit locations with the airflow was unlikely. During a certain mechanical ventilation time, the amount of bacteria reaching the outlet of the humidifier reservoir varied due to different mobility of bacteria.

RELEVANCE TO CLINICAL PRACTICE

In a clinical setting, nurses should not worry about a small amount of condensate backflow into the humidifier reservoir. Draining condensate into the humidifier reservoir can be used as a low risk and convenient method in clinical practice.

Risk factors for postoperative surgical site wound problems after metastatic and primary spine tumour surgery: A meta-analysis

A meta-analysis study was conducted to assess the risk factors (RFs) for postoperative surgical site wound problems (POSSWPs) after metastatic and primary spine tumour surgery (STS). A comprehensive literature examination until February 2023 was implemented, and 1786 linked studies were appraised. The 18 picked studies contained 18 580 subjects with surgery in the studies' baseline with and without different RFs. Odds ratio (OR) in addition to 95% confidence intervals (CIs) were used to calculate the consequence of RFs for POSSWPs after metastatic and primary STS using the dichotomous and continuous styles and a fixed or random model. Subjects with surgical instrumentation in their surgery had a significantly higher rate of POSSWPs in STS (OR, 2.28; 95% CI, 1.49-3.49, P < 0.001) compared with those without surgical instrumentation. Subjects with preoperative chemotherapy had a significantly higher rate of POSSWPs in STS (OR, 1.81; 95% CI, 1.09-3.00, P = 0.02) compared with those without preoperative chemotherapy. Subjects with preoperative radiotherapy had a significantly higher rate of POSSWPs in STS (OR, 1.93; 95% CI, 1.12-3.34, P = 0.02) compared with those without preoperative radiotherapy. Subjects with corticosteroid intake had a significantly higher rate of POSSWPs in STS (OR, 2.89; 95% CI, 1.73-4.82, P < 0.001) compared with those without corticosteroid intake. No significant difference was found between males and females in the rate of POSSWPs in STS (OR, 0.95; 95% CI, 0.66-1.37, P = 0.78). Surgical instrumentation, preoperative chemotherapy, preoperative radiotherapy and corticosteroid are RFs for the higher rate of POSSWPs in STS; however, gender was not shown to be a risk factor. Though precautions should be taken when commerce with the consequences since some of the studies picked for this meta-analysis had low sample sizes.

Effect of instant surgery compared with traditional management on paediatric complicated acute appendicitis post-surgery wound: A meta-analysis

A meta-analysis study to assess the influence of instant surgery (IS) compared with conservative therapy (CT) on paediatric complicated acute appendicitis (CAA) post-surgery wounds. A comprehensive literature examination until January 2023 was implemented, and 2098 linked studies were appraised. The picked studies contained 66 674 subjects with paediatric CAA post-surgery wounds in the picked studies' baseline; 64 643 of them were using IS, and 2031 were using CT. The odds ratio (OR) in addition to 95% confidence intervals (CIs) were used to calculate the consequence of the IS compared with the CT on paediatric CAA post-surgery wounds using the dichotomous and continuous styles and a fixed or random model. The IS had a significantly higher wound infection (OR, 4.97; 95% CI, 2.35-10.54, P < .001) with moderate heterogeneity (I2  = 57%) compared with the CT in a paediatric CAA post-surgery wound. However, no significant difference was found between IS and CT in total antibiotic duration (MD, -5.34; 95% CI,-12.67 to -1.98, P = .15) with high heterogeneity (I2  = 95%) in paediatric CAA post-surgery wounds. The IS had a significantly higher wound infection; however, no significant difference was found in total antibiotic duration compared with the CT in paediatric CAA post-surgery wounds. Although precautions should be taken when commerce with the consequences because most of the studies picked for this meta-analysis had low sample sizes.

Effect of endoscopic loop ties in acute appendicitis on wound infection rate: A meta-analysis

A meta-analysis study to measure the consequence of endoscopic loop ties (ELT) in acute appendicitis (AA) on wound infection rate. A comprehensive literature inspection till February 2023 was applied and 2765 interrelated studies were reviewed. The 27 chosen studies enclosed 15 093 subjects with AA in the chosen studies' starting point, 7141 of them were ELT, and 7952 were open surgery. Odds ratio (OR) in addition to 95% confidence intervals (CIs) were used to compute the value of the effect of ELT in AA on wound infection rate by the dichotomous and continuous styles and a fixed or random model. Open surgery had a significantly higher postoperative surgical site wound infection (SSWI). (OR, 1.41; 95% CI, 1.09-1.83, P = 0.009) with low heterogeneity (I2  = 34%) compared to ELT in AA subjects. Although no significant difference was detected between open surgery and ELT in intra-abdominal abscess rate (OR, 0.88; 95% CI, 0.56-1.40, P = 0.59) with moderate heterogeneity (I2  = 51%) in AA subjects. Open surgery had a significantly higher postoperative SSWI, however, no significant difference was found in intra-abdominal abscess rate compared to ELT in AA subjects. However, caused by the small sample sizes of several chosen studies for this meta-analysis, care must be exercised when dealing with its values.

Effect of mesenchymal stromal cells-derived extracellular vesicles as a treatment to heal diabetic wounds: A meta-analysis

A meta-analysis study to assess the influence of mesenchymal stromal cells-derived extracellular vesicles (MSC-EVs) as a treatment to heal the diabetic wound (DW). A comprehensive literature examination till February 2023 was implemented and 2975 linked studies were appraised. The picked studies contained 381 animals with diabetes mellitus in the picked studies' baseline, 217 of them were using MSC-EVs, and 173 were using control. Odds ratio in addition to 95% confidence intervals (CIs) were used to calculate the consequence of MSC-EVs as a therapy to heal DWs by the dichotomous and continuous styles and a fixed or random model. MSCs-EVs had a significantly higher rate of wound closure of DWs (Mean deviation [MD], 22.20; 95% CI, 19.16-25.24, P < .001), lower width of the scar (MD, -2.57; 95% CI, -3.35 to -1.79, P < .001), higher collagen deposition (MD, 30.82; 95% CI, 20.77-40.86, P < .001), and a higher rate of re-epithelialisation (MD, 34.36; 95% CI, 20.13-48.58, P < .001) compared with the control. MSCs-EVs had a significantly higher rate of wound closure of DWs, lower width of the scar, higher collagen deposition, and higher rate of re- epithelialisation compared with the control. Although precautions should be taken when commerce with the consequences because all of the picked studies for this meta-analysis was with low sample sizes.

Prevalence of different types of wound infection in subjects with Parkinson's disease and total joint arthroplasty: A meta-Analysis

A meta-analysis study to assess the influence of Parkinson's disease (PD) on different types of wound infection (WI) in total joint arthroplasty (TJA) patients. A comprehensive literature examination till January 2023 was implemented and 1976 linked studies were appraised. The picked studies contained 76 661 subjects with TJA in the picked studies' baseline, 19 188 of them were PD, and 57 473 were non-PD. Odds ratio (OR) in addition to 95% confidence intervals (CIs) were used to calculate the consequence of PD on different types of WI in TJA patients by the dichotomous and continuous styles and a fixed or random model. PD had a significantly higher postoperative surgical site WI (OR, 1.76; 95% CI, 1.15-2.67, P = .009), superficial WI (OR, 3.36; 95% CI, 1.41-7.99, P = .006), and periprosthetic WI (OR, 4.89; 95% CI, 2.13-11.22, P < .001) compared to the non-PD in TJA patients' post-surgery wounds. PD had a significantly higher postoperative surgical site WI, superficial WI, and periprosthetic WI compared to the non-PD in TJA patients' post-surgery wounds. Though precautions should be taken when commerce with the consequences since some of the picked studies for this meta-analysis was with low sample sizes.

Knee and hip arthroplasty joint surgical site wound infection in end-stage renal disease subjects who underwent dialysis or a kidney transplant: A meta-analysis

A meta-analysis study to assess the knee and hip arthroplasty joint surgical site wound infection (SSWI) in end-stage renal disease (ESRD) subjects who underwent dialysis or a kidney transplant (KT). A comprehensive literature examination till February 2023 was implemented and 1046 linked studies were appraised. The picked studies contained 5 471 898 subjects with total joint arthroplasty (TJA) at the baseline, 13 049 of them were haemodialysis or renal transplant, and 5 458 849 were control. Odds ratio (OR) in addition to 95% confidence intervals (CIs) were used to calculate the consequence of knee and hip arthroplasty SSWI in ESRD subjects who underwent dialysis or a KT by the dichotomous and continuous styles and a fixed or random model. Haemodialysis or renal transplant had a significantly higher postoperative SSWI (OR, 2.13; 95% CI, 1.73-2.62, P < .001) compared with control in TJA subjects. However, no significant difference was observed between haemodialysis and renal transplant in postoperative SSWI (OR, 0.93; 95% CI, 0.16-5.54, P = .94) and between haemodialysis or renal transplant and control in prosthetic joint infection (OR, 1.07; 95% CI, 0.25-4.55, P = .93) in TJA subjects. Haemodialysis had a significantly higher prosthetic joint infection (OR, 1.92; 95% CI, 1.21-3.03, P = .005) compared with renal transplant in TJA subjects. Haemodialysis or renal transplant had a significantly higher postoperative SSWI in TJA subjects. Also, haemodialysis had a significantly higher prosthetic joint infection compared with renal transplant in TJA subjects. Although precautions should be taken when commerce with the consequences because a low number of selected studies was picked for certain comparisons in this meta-analysis.

The wound adjuncts effect of closed incision negative pressure wound therapy on stopping groin surgical site wound infection in arterial surgery: A meta-analysis

A meta-analysis study was conducted to assess the influence of the wound adjuncts therapy of closed incision negative pressure wound therapy (ciNPWT) on stopping groin site wound infection (SWSI) in arterial surgery. A comprehensive literature examination till January 2023 was implemented and 2186 linked studies were appraised. The picked studies contained 2133 subjects with groin surgical wounds of arterial surgery in the picked studies' baseline, 1043 of them were using ciNPWT, and 1090 were using standard care. Odds ratio (OR) in addition to 95% confidence intervals (CIs) were used to calculate the consequence of the wound adjuncts therapy of ciNPWT on stopping groin SWSI in arterial surgery by the dichotomous and continuous styles and a fixed or random model. The ciNPWT had a significantly lower SWSI (OR, 0.42; 95% CI, 0.33-0.55, P < .001), superficial SWSI (OR, 0.46; 95% CI, 0.33-0.66, P < .001), and deep SWSI (OR, 0.39; 95% CI, 0.25-0.63, P < .001) compared with the standard care in groin surgical wound of arterial surgery. The ciNPWT had a significantly, lower SWSI, superficial SWSI, and deep SWSI compared with the standard care in groin surgical wounds of arterial surgery. Although precautions should be taken when commerce with the consequences because some of the picked studies for this meta-analysis was with low sample sizes.

Aerosol therapy in adult critically ill patients: a consensus statement regarding aerosol administration strategies during various modes of respiratory support

BACKGROUND

Clinical practice of aerosol delivery in conjunction with respiratory support devices for critically ill adult patients remains a topic of controversy due to the complexity of the clinical scenarios and limited clinical evidence.

OBJECTIVES

To reach a consensus for guiding the clinical practice of aerosol delivery in patients receiving respiratory support (invasive and noninvasive) and identifying areas for future research.

METHODS

A modified Delphi method was adopted to achieve a consensus on technical aspects of aerosol delivery for adult critically ill patients receiving various forms of respiratory support, including mechanical ventilation, noninvasive ventilation, and high-flow nasal cannula. A thorough search and review of the literature were conducted, and 17 international participants with considerable research involvement and publications on aerosol therapy, comprised a multi-professional panel that evaluated the evidence, reviewed, revised, and voted on recommendations to establish this consensus.

RESULTS

We present a comprehensive document with 20 statements, reviewing the evidence, efficacy, and safety of delivering inhaled agents to adults needing respiratory support, and providing guidance for healthcare workers. Most recommendations were based on in-vitro or experimental studies (low-level evidence), emphasizing the need for randomized clinical trials. The panel reached a consensus after 3 rounds anonymous questionnaires and 2 online meetings.

CONCLUSIONS

We offer a multinational expert consensus that provides guidance on the optimal aerosol delivery techniques for patients receiving respiratory support in various real-world clinical scenarios.

Effect of oxygen flow on aerosol delivery from a vibrating mesh nebulizer with a holding chamber

Background

A holding chamber (HC) was created to work with a vibrating mesh nebulizer (VMN) to boost the total inhalable dose for patients. In addition to the optional supply of supplemental oxygen, it facilitates intermittent and continuous nebulization. Our goal was to see how well a VMN coupled to a HC with a mouthpiece or valved facemask performed at varied oxygen flows starting at 0–6 L/min. In this study, we used a breathing simulator to simulate adults' spontaneous breathing patterns with a tidal volume of 500 mL and a 1:1 inhalation–exhalation ratio. For the combination of nebulizer and HC adapter with a valved facemask or mouthpiece, five determinations were made. Salbutamol was recovered and evaluated using high-performance liquid chromatography from the inhalation filter connected to the breathing simulator, the nebulizer reservoir chamber, and the HC.

Results

The amount of salbutamol in the nebulizer reservoir chamber and within the HC did not differ significantly when using a mouthpiece or a valved facemask. However, the supplied dose to the inhalation filter was increased until oxygen flow reached 2 and 3 L/min using the mouthpiece and valved facemask as interfaces, respectively. The supplied salbutamol was much higher at this flow than at the other oxygen flows. This was followed by a progressive reduction in the supplied salbutamol until the lowest given dose was reached at 6 L/min oxygen flow, p < 0.005.

Conclusions

The supplied doses of salbutamol to the inhalation filter were variable with the VMN connected to the HC and mouthpiece or valved facemask, with significant improvements until an oxygen flow of 2 L/min with a mouthpiece and 3 L/min with a valved facemask, followed by gradual decreases to lower values at an oxygen flow of 6 L/min. An in vivo investigation is required to further validate the findings.

Effect of pressures and type of ventilation on aerosol delivery to chronic obstructive pulmonary disease patients

Background

Continuous Positive Airway Pressure (CPAP), BiPhasic Positive Airway Pressure (BiPAP), and high flow nasal cannula (HFNC) show some evidence to have efficacy in COVID-19 patients. Delivery during noninvasive mechanical ventilation (NIV) or HFNC gives faster and more enhanced clinical effects than when aerosols are given without assisted breath. The present work aimed to compare the effect of BiPhasic Positive Airway Pressure (BiPAP) mode at two different pressures; low BiPAP (Inspiratory Positive Airway Pressure (IPAP)/Expiratory Positive Airway Pressure (EPAP) of 10/5 cm water) and high BiPAP (IPAP/EPAP of 20/5 cm water), with HFNC system on pulmonary and systemic drug delivery of salbutamol. On the first day of the experiment, all patients received 2500 μg salbutamol using Aerogen Solo vibrating mesh nebulizer. Urine samples 30 min post-dose and cumulative urinary salbutamol during the next 24 h were collected on the next day. On the third day, the ex-vivo filter was inserted before the patient to collect the delivered dose to the patient of the 2500 μg salbutamol. Salbutamol was quantified using high-performance liquid chromatography (HPLC).

Results

Low-pressure BiPAP showed the highest amount delivered to the lung after 30 min followed by HFNC then high-pressure BiPAP. But the significant difference was only observed between low and high-pressure BiPAP modes (p = 0.012). Low-pressure BiPAP showed the highest delivered systemic delivery amount followed by HFNC then high-pressure BiPAP. Low-pressure BiPAP was significantly higher than HFNC (p = 0.017) and high-pressure BiPAP (p = 0.008). No significant difference was reported between HFNC and high-pressure BiPAP. The ex-vivo filter was the greatest in the case of low-pressure BiPAP followed by HFNC then high-pressure BiPAP. Low-pressure BiPAP was significantly higher than HFNC (p = 0.033) and high-pressure BiPAP (p = 0.008). Also, no significant difference was found between HFNC and high-pressure BiPAP.

Conclusions

Our results of pulmonary, systemic, and ex-vivo drug delivery were found to be consistent. The low BiPAP delivered the highest amount followed by the HFNC then the high BiPAP with the least amount. However, no significant difference was found between HFNC and high BiPAP.

Aerosol delivery of inhalation devices with different add-on connections to invasively ventilated COPD subjects: An in-vivo study

Aerosol delivery to mechanically ventilated patients requires add-on connections to place the inhalation device within the ventilation circuit. The study aimed to evaluate the performance of Combihaler in dual limb invasive mechanical ventilation (IMV). A ventilator with a humidified dual limb circuit was adjusted to volume-controlled mode to imitate the adult breathing parameters. 24 (12 females) intubated chronic obstructive pulmonary disease (COPD) subjects had undergone the study. All patients were prescribed inhaled salbutamol dose delivered by either a metered-dose inhaler (pMDI) or vibrating mesh nebulizer (VMN). Each subject received salbutamol in four different inhalation device/connection conditions; pMDI+VMN+Combihaler, VMN+Combihaler, VMN+T-piece, and pMDI+T-piece. They were individually placed in the inspiratory limb at Y-piece. 5mg salbutamol was delivered by VMN with and without 2 pMDI puffs of salbutamol (100 µg), and 500µg was delivered by pMDI+T-piece. After aerosol delivery, two urine samples were collected from the patient; 30 min post-inhalation (USAL0.5) and cumulatively 24 h post-inhalation (USAL24) as indexes of lung deposition and systemic absorption, respectively. For the ex-vivo study, a collecting filter was placed before an endotracheal tube (ETT) to collect the delivered inhalable dose. In-vitro aerodynamic characteristics were also investigated. pMDI+VMN+Combihaler delivered more salbutamol to the lung and the ex-vivo filter than VMN+T-piece (p˂0.05, p≤0.01, respectively). VMN delivered a higher salbutamol amount to the lung, systemically, and the ex-vivo filter than pMDI+T-piece (p˂0.001). pMDI+VMN+Combihaler and VMN+Combihaler delivered aerosols with a less mass median aerodynamic diameter (MMAD) and higher fine particle fraction (FPF) compared to VMN+T-piece (p≤0.01 for MMAD, p˂0.01 for FPF) and pMDI+T-piece (p˂0.01 for both MMAD and FPF). Results of the study showed that pMDI+VMN+ Combihaler delivered more salbutamol than VMN+T-piece in IMV and demonstrate that 5 puffs (500-µg) of salbutamol with pMDI+T-piece has a lower aerosol delivering power at the level of USAL0.5, USAL24, and the ex-vivo inhalable dose than 5 mg nebulized salbutamol by VMNs in IMV.

Aerosol delivery through high flow nasal cannula compared to biphasic positive airway pressure, at two different pressure: an in-vitro study

Background

Both non-invasive ventilation and high flow oxygen therapy are preferred over low flow oxygen therapy in many conditions. Nebulizers, for aerosol delivery, can be used within them without interrupting the circuit. The present study aimed to compare the efficiency of drug delivery within high flow nasal cannula (HFNC) and biphasic positive airway pressure (BiPAP) ventilation mode using two different inspiratory positive airway pressures. The aerosol delivery was examined in HFNC system at low flow, 5 L min−1, and BiPAP non-invasive ventilation under 2 different pressures [high pressure; inspiratory positive airway pressure/expiratory positive airway pressure (IPAP/EPAP) of 20/5 cm water, and low pressure; IPAP/EPAP of 10/5 cm water]. The total inhalable dose (TID) was measured by inserting an Aerogen Solo nebulizer installed with 1 mL salbutamol respiratory solution (5000 μg mL−1) within the circuit, and the salbutamol was collected on an inhalation filter placed in a filter holder connected to a breathing simulator. The breathing simulator was adjusted at a tidal volume of 500 mL, respiratory rate of 15 breaths min−1, and inhalation to exhalation (I:E) ratio of 1:1 for the adult setting. In each technique of the three (HFNC, and low, and high-pressures BiPAP), TID was determined 5 times (n = 5). For particle size characterization, cooled Anderson Cascade Impactor (ACI) was inserted instead of the inhalation filter and the breathing simulator with the same scheme. In each technique of the three, particle size characterization was determined 3 times (n = 3).

Results

The BiPAP mode at low inspiratory pressure had the highest TID, followed by HFNC at flow 5 L min−1, then BiPAP mode at high inspiratory pressure. There was a significant difference only between low and high inspiratory pressure modes of BiPAP mode. Low-inspiratory pressure BiPAP delivered the highest mean ± SD fine particle dose (FPD). It was significantly higher than that delivered in high inspiratory pressure BiPAP, and HFNC. Also, FPD in HFNC was significantly higher than that in high inspiratory pressure BiPAP. HFNC system had the smallest mass median aerodynamic diameter (MMAD) and the highest FPF followed by low then high inspiratory pressure BiPAP.

Conclusions

Increasing the inspiratory positive airway pressure in BiPAP, from 10 to 20 cm water, decreased the total inhalable dose and FPF nearly by half. Low inspiratory pressure BiPAP delivered the highest TID and FPD. The HFNC system at low oxygen flow resulted in the least MMAD, and the highest FPF. Using HFNC delivered a TID that was non-significant from that delivered by low inspiratory pressure BiPAP.

Graphical Abstract

Impact of different nebulisers' connections on aerosol therapy

BACKGROUND

Aerosol therapy has the advantage of a higher safety because of the local deposition of inhaled medication to the lung; however, the main drawback is the low and variable amount of delivered drug to patients. Hence, this study aimed to investigate the effect of different accessory connections on aerosol delivery from different nebulisers.

METHOD

This study consisted of 3 main models: in vitro, in vivo and ex vivo models. In vitro model, 6 nebulisers (3 Jet (Dolphin (2030 2001), Philips (SideStream) and Tylenol (TL009002)) and 3 vibrating mesh nebulisers (VMNs) (Aerogen Pro, Solo, an Nivo)) were charged with 5 mg/2 mL salbutamol and connected to 2 different connections (T-piece and Circulaire II Hybrid) with an inhalation filter attached to a breathing simulator. Inhaled amounts of drug (inhalation filter) and that remained inside nebuliser were measured. Concerning ex vivo and in vivo models, 24 subjects were involved in the study and they received 5 mg/2 mL salbutamol from 1 Jet nebuliser and 1 VMNs using both connections. Two urine samples were collected post 30 minutes and pooled 24 hours urine collection. For the ex vivo model, inhaled amounts of salbutamol were collected on filters placed between the subjects and the nebuliser.

RESULTS

Inhaled amounts of salbutamol expressed by the amount of drug detected on inhalation filters (for both in vitro and ex vivo) were significantly higher from both Jet and VMNs connected to the Circulaire II Hybrid connection than that released from nebulisers connected to T-piece. VMNs delivered a higher amount compared with jet nebulisers. The amount released from jet nebulizers were variables, unlike VMNs. Regarding in vivo results, amounts of drug detected in 30 minutes urine samples were consistent with in vitro and ex vivo models reflecting higher and significant amounts of drug delivered to the patient's lung for Circulaire II Hybrid connection compared with T-piece regarding both nebulisers.

CONCLUSION

Using a valved chamber with jet and VMNs significantly improved the inhaled amount of the emitted aerosol. VMNs were more effective than jet nebulisers with both connections.

Lung deposition and systemic bioavailability of dose delivered to smoker compared with non-smoker COPD subjects

INTRODUCTION

Inhaled drugs are the most commonly used class of medications for COPD subjects. No studies have been performed to assess the influence of smoking on lung deposition of aerosolized medication, especially for the exacerbated COPD subject. The present study aimed to assess the influence of smoking on the lung deposition of the aerosol delivered to exacerbated COPD subjects.

METHODS

Twenty-four exacerbated COPD subjects using automatic continuous positive airway pressure (Auto-CPAP), 12 smokers (six females) and 12 non-smokers (six females) were recruited in the study. The subjects participated in the study received four salbutamol study doses; 1200 µg (12 puffs 100 µg/puff) of salbutamol emitted from pMDI canister connected to AeroChamber MV spacer; 1200 µg of salbutamol emitted from pMDI canister connected to Combihaler spacer; 1 mL of salbutamol respirable solution (5000 µg/mL) nebulized by Aerogen Solo connected to its T-piece; and 1 mL of salbutamol respirable solution nebulized by Aerogen Solo connected to Combihaler spacer with 2 puffs salbutamol MDI (200 µg salbutamol) before nebulisation. The subjects were randomised to receive the four selected dose-adaptor combination in a sealed envelope design on days 1, 3, 5 and 7. A washout period of 24 hours was provided between each salbutamol dosing. Auto-CPAP was adjusted at non-invasive ventilation mode with the integrated heated humidifier, as a source of humidity. Urine samples were provided by subjects, 30 minutes and cumulatively 24 hours post inhalation, as an index of the relative and systemic bioavailability, respectively, and aliquots were retained for salbutamol analysis using solid-phase extraction and high-performance liquid chromatography (HPLC). On day 2 of the study, a collecting filter was placed between the aerosol generator and the subject's mask so that the subjects would not inhale the salbutamol delivered. The same study doses and/or adapters were delivered to each subject, with filters changed with each dose-adapter combination. Salbutamol entrained on the filter was desorbed to be analysed by the HPLC.

RESULTS

Significantly higher lung deposition (30 minutes urinary salbutamol) was detected with the non-smoker compared with smokers (P < .05). Significantly higher systemic bioavailability (pooled 24-hour urinary salbutamol) for smokers compared with non-smokers was found with Aerogen Solo connected to its T-piece and CombiHaler spacer with pMDI (P < .05) only. Significantly higher amount desorbed from the ex-vivo filter were found from pMDI with both spacers in non-smokers (P < .05) compared with the smokers.

CONCLUSION

The study demonstrated that smoking reduced the lung deposition of inhaled salbutamol delivered by nebulizer or pMDI. However, the smoking effect on cytochrome p450 was observed to increase systemic absorption of the ingested portion of the inhaled dose. The lower lung deposition and possible higher systemic absorption should be taken into consideration while prescribing inhaled medication to COPD smokers especially exacerbated patients that need ventilation. Further studies are needed.

The impact of changing patient interfaces on delivering aerosol with titrated oxygen in the high flow system

INTRODUCTION

Despite the widespread oxygen-culture as more is better in prehospital and hospital settings, the use of titrated oxygen-flow within a high-flow system can be beneficial especially when combined with aerosol-delivery and also save the patient from unnecessary-hyperoxia.

METHODS

Forty-five COPD patients were included in this study where they allocated in three-groups (nasal-delivery, oral-delivery, and oronasal-delivery groups). All patients were received their inhaled-salbutamol dose using Aerogen Solo nebuliser by one of the three interfaces, eg, nasal-cannula, mouthpiece, and facemask in two conditions; with oxygen-flow and without any oxygen-flow. Pulmonary and systemic salbutamol deposition was estimated by collecting two urine-samples from the patient; 30 min post-inhalation and cumulatively 24 hr post-inhalation. The quantity of salbutamol in these collected samples was measured by high-performance liquid chromatography. Lung function measurement was performed pre-bronchodilator inhalation and 30 min post-bronchodilator to estimate the change in pulmonary functions post-inhalation regarding all tested interfaces.

RESULTS

COPD patients showed the highest salbutamol percentage excreted 30 min post-inhalation of 5.7% (1.4) with mouthpiece interface when combined with oxygen at P < .002. While with the same condition using oxygen, valved-facemask showed the highest salbutamol percentage excreted in 24 hr post inhalation samples but the difference is only significantly compared with nasal cannula (P < .006). Moreover, without oxygen delivery, mouthpiece and valved facemask showed approximately the same salbutamol percentage excreted in 30 min post-inhalation samples, higher than that delivered by nasal cannula (P < .001). Of note, salbutamol delivery is significantly increased with oxygen flow for all interfaces (P < .05) except with nasal cannula.

CONCLUSIONS

The nasal cannula is a more comfortable and tolerable interface despite the lower fraction of the delivered drug compared with other tested interfaces. The use of oxygen-flow with aerosol delivery within a high flow system positively affects the delivered drug fraction and the pulmonary deposition of the drug.

Aerosol delivery via noninvasive ventilation: role of models and bioanalysis

Non-invasive ventilation (NIV) is external support for respiration to assist breathing in case of respiratory failure (either hypercapnic or hypoxemic) without patient intubation. Nowadays, medicated aerosols are normally delivered to mechanically ventilated patients by nebulizers and pressurized metered-dose inhaler (pMDI) attached to adapter or spacer that fit into the ventilated circuit. Studies with obstructive lung disease patients have shown that aerosol delivery during mechanical ventilation is possible and of benefit. There are several models for investigating the aerosol delivery and deposition during mechanical ventilation such as in vitro, in vivo, and ex vivo models, these models depend on the technique used for quantitative or qualitative measurement of the deposited aerosol. In vitro models could be used for calculating the total emitted doses from different aerosol-generating devices or for aerodynamic characterization of the deposited inhaled medications. In vivo models dependents of extracting drugs from biological samples for measuring its concentration and bioavailability (pharmacokinetic model) or be dependent on the imaging technique of the radioactive aerosol. Applying different methods to predict aerosol efficiency before starting NIV and to quantify aerosol delivery during NIV are promising approaches that guide clinicians to avoid treatment failure before and during patient therapy.

Future Trends in Nebulized Therapies for Pulmonary Disease

Aerosol therapy is a key modality for drug delivery to the lungs of respiratory disease patients. Aerosol therapy improves therapeutic effects by directly targeting diseased lung regions for rapid onset of action, requiring smaller doses than oral or intravenous delivery and minimizing systemic side effects. In order to optimize treatment of critically ill patients, the efficacy of aerosol therapy depends on lung morphology, breathing patterns, aerosol droplet characteristics, disease, mechanical ventilation, pharmacokinetics, and the pharmacodynamics of cell-drug interactions. While aerosol characteristics are influenced by drug formulations and device mechanisms, most other factors are reliant on individual patient variables. This has led to increased efforts towards more personalized therapeutic approaches to optimize pulmonary drug delivery and improve selection of effective drug types for individual patients. Vibrating mesh nebulizers (VMN) are the dominant device in clinical trials involving mechanical ventilation and emerging drugs. In this review, we consider the use of VMN during mechanical ventilation in intensive care units. We aim to link VMN fundamentals to applications in mechanically ventilated patients and look to the future use of VMN in emerging personalized therapeutic drugs.

Aerosol Delivery to a Critically Ill Patient: A Big Issue Easily Solved by Developing Guidelines

Nowadays, therapeutic aerosols are commonly delivered to mechanically ventilated patients by nebulizers and pressurized metered dose inhaler attached to an adapter or a spacer. Studies with asthmatics and chronic obstructive pulmonary disease patients have confirmed that aerosol delivery during mechanical ventilation is feasible. They have also reported that the inhaled drugs administered during mechanical ventilation provide greater and faster clinical outcomes than when delivering during spontaneous unassisted breathing. Researchers studied factors that would affect aerosol delivery during mechanical ventilation. Even with the tremendous amount of publications in this area, there have still been no recommendations or guidelines released to help respiratory therapists in their decision as to when to deliver aerosol to ventilated patients. Mostly, respiratory therapists read the literature and decide accordingly what to do and which device to use for their patients. This puts the patients at risk of receiving a sub-therapeutic or toxic dose of the inhaled aerosol. Some studies raise an alarm of physician decision upon reading any released publication related to aerosol delivery in mechanical ventilation without a trusted recommendation and guidelines. This increases the need for the development of recommendations and guidelines, by a trusted board or society, for aerosol delivery to such critically ill patients. To summarize, inhaled drugs administered to critically ill patients is of benefit compared to taking the patient off the ventilator and delivering during spontaneous unassisted breathing. However, dependable guidelines are needed to optimize aerosol delivery.

Modeling and optimization of nebulizers' performance in non-invasive ventilation using different fill volumes: Comparative study between vibrating mesh and jet nebulizers

BACKGROUNDS

Substituting nebulisers by another, especially in non-invasive ventilation (NIV), involves many process-variables, e.g. nebulizer-type and fill-volume of respirable-dose, which might affect patient optimum-therapy. The aim of the present work was to use neural-networks and genetic-algorithms to develop performance-models for two different nebulizers.

METHODS

In-vitro, ex-vivo and in-vivo models were developed using input-variables including nebulizer-type [jet nebulizer (JN) and vibrating mesh nebulizer (VMN)] fill-volumes of respirable dose placed in the nebulization chamber with an output-variable e.g. average amount reaching NIV patient. Produced models were tested and validated to ensure effective predictivity and validity in further optimization of nebulization process.

RESULTS

Data-mining produced models showed excellent training, testing and validation correlation-coefficients. VMN showed high nebulization efficacy than JN. JN was affected more by increasing the fill-volume. The optimization process and contour-lines obtained for in-vivo model showed increase in pulmonary-bioavailability and systemic-absorption with VMN and 2 mL fill-volumes.

CONCLUSIONS

Modeling of aerosol-delivery by JN and VMN using different fill-volumes in NIV circuit was successful in demonstrating the effect of different variable on dose-delivery to NIV patient. Artificial neural networks model showed that VMN increased pulmonary-bioavailability and systemic-absorption compared to JN. VMN was less affected by fill-volume change compared to JN which should be diluted to increase delivery.

Lung deposition and systemic bioavailability of different aerosol devices with and without humidification in mechanically ventilated patients

BACKGROUND

During mechanical ventilation medical aerosol delivery has been reported to be upto two fold greater with dry inhaled gas than with heated humidity. Urine levels at 0.5 h post dose (URSAL0.5%) has been confirmed as an index of lung deposition and 24 h (URSAL24%) as index of systemic absorption. Our aim was to determine the effect of humidification and aerosol device type on drug delivery to ventilated patients using urine levels.

METHODS

In a randomized crossover design, 36 (18female) mechanically ventilated patients were assigned to one of three groups. Groups 1 and 2 received 5000 μg salbutamol using vibrating mesh (VM) and jet nebulizers (JN), respectively, while group 3 received 1600 μg (16 puffs) of salbutamol via metered dose inhaler with AeroChamber Vent (MDI-AV). All devices were placed in the inspiratory limb of ventilator downstream from the humidifier. Each subject received aerosol with and without humidity at >24 h intervals with >12 h washout periods between salbutamol doses. Patients voided urine 15 min before each study dose and urine samples were collected at 0.5 h post dosing and pooled for the next 24 h.

RESULTS

The MDI-AV and VM resulted in a higher percentage of urinary salbutamol levels compared to the JN (p < 0.05). Urine levels were similar between humidity and dry conditions.

CONCLUSIONS

Our findings suggest that in-vitro reports overestimate the impact of dry vs. heated humidified conditions on the delivery of aerosol during invasive mechanical ventilation.