La ventilazione non-invasiva a pressione positiva nell’insufficienza respiratoria acuta ipercapnica: 10 anni di esperienza clinica di una Unità di Terapia Semi-Intensiva Respiratoria

PremessaSebbene numerosi studi prospettici, controllati e randomizzati abbiano dimostrato il successo della ventilazione non-invasiva a pressione positiva (NIV) in casi selezionati di insufficienza respiratoria acuta ipercapnica (IRA) in setting con intensità di cura differenti, i dati di pratica clinica relativi all’uso della NIV nel “mondo reale” sono limitati. Scopo Riportare i risultati della nostra esperienza clinica sulla NIV nell’IRA applicata nell’Unità di Terapia Semi-Intensiva Respiratoria (UTSIR) allocata all’interno dell’Unità Operativa di Pneumologia di Arezzo negli anni 1996-2006 in termini di: tollerabilità, effetti sui gas ematici, tasso di successo e fattori predittivi del fallimento.MetodiTrecentocinquanta dei 1484 pazienti (23.6%) consecutivamente ammessi per IRA nella nostra Unità Operativa di Pneumologia durante il periodo di studio hanno ricevuto la NIV in aggiunta alla terapia standard, in seguito al raggiungimento di criteri predefiniti impiegati di routine.RisultatiOtto pazienti (2.3%) non hanno tollerato la NIV per discomfort alla maschera, mentre i rimanenti 342 (M: 240, F: 102; età: mediana (interquartili) 74.0 (68.0-79.3) anni; BPCO: 69.3%) sono stati ventilati per >1 ora. I gas ematici sono significativamente migliorati dopo 2 ore di NIV (media (deviazione standard) pH: 7.33 (0.07) versus 7.28 (7.25-7.31), p<0.0001; PaCO2: 71.4 (15.3) mmHg versus 80.8 (16.6) mmHg, p<0.0001; PaO2/FiO2: 205 (61) versus 183 (150-222), p<0.0001). La NIV ha evitato l’intubazione in 285/342 pazienti (83.3%) con una mortalità ospedaliera del 14.0%. Il fallimento della NIV è risultato essere predetto in modo indipendente dall’Apache III (Acute Physiology and Chronic Health Evaluation III) score, dall’indice di massa corporea e dal fallimento tardivo della NIV (> 48 ore di ventilazione) dopo iniziale risposta positiva.ConclusioniSecondo la nostra esperienza clinica di dieci anni realizzata in una UTSIR, la NIV si conferma essere ben tollerata, efficace nel migliorare i gas ematici e utile nell’evitare l’intubazione in molti episodi di IRA non-responsivi alla terapia standard.

La ventilación no invasiva con presión positiva en la insuficiencia respiratoria aguda hipercápnica: diez años de experiencia clínica de una unidad de terapia semiintensiva respiratoria

Premisa: Si bien numerosos estudios prospectivos, controlados y aleatorizados han demostrado el éxito de la ventilación no invasiva con presión positiva (VNI) en casos seleccionados de insuficiencia respiratoria aguda (IRA) hipercápnica, en contexto con intensidad de cuidado diferente, los datos de práctica clínica relativos al uso de la VNI en escenarios reales son limitados.Objetivo: Reportar los resultados de nuestra experiencia clínica sobre la VNI en la IRA aplicada en la Unidad de Terapia Semiintensiva Respiratoria (UTSIR), de la Unidad Operativa de Neumología de Arezzo, entre 1996-2006, en términos de tolerabilidad, efectos sobre los gases arteriales, tasa de éxito y factores predictivos del fracaso.Métodos: Trescientos cincuenta de los 1.484 pacientes (23,6%) ingresados consecutivamente por IRA en nuestra Unidad Operativa de Neumología, durante el periodo de estudio, recibieronla VNI asociada a la terapia estándar, posterior al cumplimiento de criterios predefinidos, empleados de rutina.Resultados: Ocho pacientes (2,3%) no toleraron la VNI por incomodidad producida por la máscara, mientras los 342 restantes (M: 240; F: 102; edad: mediana [intercuartiles] 74,0 años [68,0-79,3]; enfermedad pulmonar obstructiva crónica (EPOC) [69,3%]) fueron ventilados por más de una hora. Los parámetros de ventilación (y su efecto sobre el pH) y de oxigenación mejoraron significativamente después de dos horas de VNI (media [desviación estándar] pH: 7,33 [0,07] contra 7,28 [7,25-7,31 ], p < 0,0001; PaCO2: 71,4 mmHg [15,3] contra 80,8 mmHg [16,6], p < 0,0001; PaO2/FiO2: 205 [61] contra 183 [150-222 ], p < 0,0001). La VNI evitó la intubación en 285/342 pacientes (83,3%), con una mortalidad hospitalaria del 14,0%. El fracaso de la VNI resultó ser predicho de modo independiente por el puntaje acute physiology and chronic health evaluation III (Apache III), por el índice de masa corporal y por el fracaso tardío de la VNI (mayor a 48 horas de ventilación), después de una respuesta positiva inicial.Conclusiones: Según nuestra experiencia clínica de diez años en una UTSIR, la VNI confirma ser bien tolerada, eficaz en el mejoramiento de los gases arteriales y útil en evitar la intubación en muchos episodios de IRA que no responden a la terapia estándar.

The effect of intracuff alkalinized 2% lidocaine on emergence coughing, sore throat, and hoarseness in smokers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of the isoflurane-sparing effects of lidocaine and fentanyl during surgery in dogs

Objective-To evaluate the isoflurane-sparing effects of lidocaine and fentanyl administered by constant rate infusion (CRI) during surgery in dogs.Design-Randomized prospective study.Animals-24 female dogs undergoing unilateral mastectomy because of mammary neoplasia.Procedures-After premedication with acepromazine and morphine and anesthetic induction with ketamine and diazepam, anesthesia in dogs (n = 8/group) was maintained with isoflurane combined with either saline (0.9% NaCl) solution (control), liclocaine (1.5 mg/kg [0.68 mg/lb], IV bolus, followed by 250 mu g/kg/min [113 mu g/lb/min], CRI), or fentanyl (5 mu g/kg [2.27 mu g/lb], IV bolus, followed by 0.5 mu g/kg/min [0.23 mu g/lb/min], CRI). Positive-pressure ventilation was used to maintain eucapnia. An anesthetist unaware of treatment, endtidal isoflurane (ETiso) concentration, and vaporizer concentrations adjusted a nonprecision vaporizer to maintain surgical depth of anesthesia. Cardiopulmonary variables and ETiso values were monitored before and after beginning surgery.Results-Heart rate was lower in the fentanyl group. Mean arterial pressure did not differ among groups after surgery commenced. In the control group, mean +/- SD ETiso values ranged from 1.16 +/- 0.35% to 1.94 +/- 0.96%. Fentanyl significantly reduced isoflurane requirements during surgical stimulation by 54% to 66%, whereas the reduction in ETiso concentration (34% to 44%) observed in the lidocaine group was not significant.Conclusions and Clinical Relevance-Administration of fentanyl resulted in greater isoflurane sparing effect than did liclocaine. However, it appeared that the low heart rate induced by fentanyl may partially offset the improvement in mean arterial pressure that would be expected with reduced isoflurane requirements.

Comparação entre a ventilação com pressão positiva intermitente ou pressão controlada em equinos anestesiados com isofluorano

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of continuous rate infusion of butorphanol in isoflurane-anesthetized calves

PURPOSE:To assess the hemodynamic changes and bispectral index (BIS) following administration of a continuous rate infusion (CRI) of butorphanol in isoflurane-anesthetized calves.METHODS: Eight calves weighing 110 ± 12 kg were included in the study. Anesthesia was induced with 5% isoflurane in O2 delivered via face mask and maintained with end-tidal concentration of 1.4%. IPPV was set to a peak inspiratory airway pressure of 15 cmH2O and respiratory rate of six breaths minute-1. Forty minutes after the start of anesthetic maintenance, 0.1 mg kg-1butorphanol was administered intravenously, followed by a CRI of 20 µg kg-1 minute-1. Hemodynamic variables and BIS were recorded before butorphanol administration (T0), and at 10, 20, 40 and 80 minutes following the CRI. Anesthesia was discontinued after the last recording and the calves were allowed to recover. The time to sternal recumbency (SRE) and standing (ST) were evaluated.RESULTS: There were no significant differences between the moments in all hemodynamic variables and BIS. The time to SRE and ST was 9 ± 5 and 14 ± 7 minutes, respectively.CONCLUSION: The continuous rate infusion did not produce clinically relevant changes in hemodynamic or bispectral index values compared to baseline in mechanically ventilated and unstimulated calves anesthetized at 1.4% isoflurane.

Bispectral index in calves anesthetized with xylazine, midazolam, ketamine, isoflurane and subjected to continuous rate infusion of lidocaine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

[Spontaneous dural arterio-venous fistula at the cavernous sinus: detected by decompensation following endoscopic sinus surgery]

Spontaneous dural arterio-venous fistulas can imperceptibly develop over a long time period before they suddenly develop symptoms like bruit, loss of vision, exophthalmos and conjunctival injection. We present the rare case of an occult, para-infectious, dural arterio-venous fistula which became symptomatic after endoscopic sinus surgery. Conjunctival injection and slight exophthalmos developed due to decompensation of venous drainage probably by intraoperative positioning of the patient, positive pressure ventilation and nasal packing.

Effect of chest compressions only during experimental basic life support on alveolar collapse and recruitment

AIM: The importance of ventilatory support during cardiac arrest and basic life support is controversial. This experimental study used dynamic computed tomography (CT) to assess the effects of chest compressions only during cardiopulmonary resuscitation (CCO-CPR) on alveolar recruitment and haemodynamic parameters in porcine model of ventricular fibrillation. MATERIALS AND METHODS: Twelve anaesthetized pigs (26+/-1kg) were randomly assigned to one of the following groups: (1) intermittent positive pressure ventilation (IPPV) both during basic life support and advanced cardiac life support, or (2) CCO during basic life support and IPPV during advanced cardiac life support. Measurements were acquired at baseline prior to cardiac arrest, during basic life support, during advanced life support, and after return of spontaneous circulation (ROSC), as follows: dynamic CT series, arterial and central venous pressures, blood gases, and regional organ blood flow. The ventilated and atelectatic lung area was quantified from dynamic CT images. Differences between groups were analyzed using the Kruskal-Wallis test, and a p<0.05 was considered statistically significant. RESULTS: IPPV was associated with cyclic alveolar recruitment and de-recruitment. Compared with controls, the CCO-CPR group had a significantly larger mean fractional area of atelectasis (p=0.009), and significantly lower PaO(2) (p=0.002) and mean arterial pressure (p=0.023). The increase in mean atelectatic lung area observed during basic life support in the CCO-CPR group remained clinically relevant throughout the subsequent advanced cardiac life support period and following ROSC, and was associated with prolonged impaired haemodynamics. No inter-group differences in myocardial and cerebral blood flow were observed. CONCLUSION: A lack of ventilation during basic life support is associated with excessive atelectasis, arterial hypoxaemia and compromised CPR haemodynamics. Moreover, these detrimental effects remain evident even after restoration of IPPV.

Development of post-pump syndrome in a sheep after mitral valve stenting

A one-year-old healthy sheep received an implant stenting the mural ('posterior') leaflet of the mitral valve. The experiment was authorized by the Cantonal Ethical Committee. The surgery was performed on the open, beating heart during cardiopulmonary bypass (CPB). Management of anaesthesia was based on isoflurane with mechanical intermittent positive pressure ventilation (IPPV) of the lungs, combined with intercostal nerve blocks and intravenous fentanyl and lidocaine. Marked cardiovascular depression occurred towards the end of CPB time and required high doses of dopamine, dobutamine, lidocaine and ephedrine to allow for weaning off the CPB pump. Moreover, severe pulmonary dysfunction developed when IPPV was re-initiated after CPB. Hypoxaemia persisted throughout the recovery from general anaesthesia. Multiple organ failure developed gradually during the three postoperative days, leading to euthanasia of the animal. As described in this case, marked lung injury associated with some degree of failure of other vital organs may occur in sheep after CPB. Intraoperative cardiorespiratory complications when weaning-off may indicate the development of 'post-pump syndrome'.

Hemodynamic Effects of Noninvasive Ventilation in Patients with Venocapillary Pulmonary Hypertension

Background: The hemodynamic effects of noninvasive ventilation with positive pressure in patients with pulmonary hypertension without left ventricular dysfunction are not clearly established. Objectives: Analyze the impact of increasing airway pressure with continuous positive airway pressure on hemodynamic parameters and, in particular, on cardiac output in patients with variable degrees of pulmonary hypertension. Methods: The study included 38 patients with pulmonary hypertension caused by mitral stenosis without left ventricular dysfunction or other significant valvulopathy. The hemodynamic state of these patients was analyzed in three conditions: baseline, after continuous positive pressure of 7 cmH2O and, finally, after pressure of 14 cmH2O. Results: The population was composed of predominantly young and female individuals with significant elevation in pulmonary arterial pressure (mean systolic pressure of 57 mmHg). Of all variables analyzed, only the right atrial pressure changed across the analyzed moments (from the baseline condition to the pressure of 14 cmH2O there was a change from 8 ± 4 mmHg to 11 ± 3 mmHg, respectively, p = 0.031). Even though there was no variation in mean cardiac output, increased values in pulmonary artery pressure were associated with increased cardiac output. There was no harmful effect or other clinical instability associated with use application of airway pressure. Conclusion: In patients with venocapillary pulmonary hypertension without left ventricular dysfunction, cardiac output response was directly associated with the degree of pulmonary hypertension. The application of noninvasive ventilation did not cause complications directly related to the ventilation systems.

Patient-ventilator asynchrony during noninvasive ventilation: a bench and clinical study.

BACKGROUND: Different kinds of ventilators are available to perform noninvasive ventilation (NIV) in ICUs. Which type allows the best patient-ventilator synchrony is unknown. The objective was to compare patient-ventilator synchrony during NIV between ICU, transport-both with and without the NIV algorithm engaged-and dedicated NIV ventilators. METHODS: First, a bench model simulating spontaneous breathing efforts was used to assess the respective impact of inspiratory and expiratory leaks on cycling and triggering functions in 19 ventilators. Second, a clinical study evaluated the incidence of patient-ventilator asynchronies in 15 patients during three randomized, consecutive, 20-min periods of NIV using an ICU ventilator with and without its NIV algorithm engaged and a dedicated NIV ventilator. Patient-ventilator asynchrony was assessed using flow, airway pressure, and respiratory muscles surface electromyogram recordings. RESULTS: On the bench, frequent auto-triggering and delayed cycling occurred in the presence of leaks using ICU and transport ventilators. NIV algorithms unevenly minimized these asynchronies, whereas no asynchrony was observed with the dedicated NIV ventilators in all except one. These results were reproduced during the clinical study: The asynchrony index was significantly lower with a dedicated NIV ventilator than with ICU ventilators without or with their NIV algorithm engaged (0.5% [0.4%-1.2%] vs 3.7% [1.4%-10.3%] and 2.0% [1.5%-6.6%], P < .01), especially because of less auto-triggering. CONCLUSIONS: Dedicated NIV ventilators allow better patient-ventilator synchrony than ICU and transport ventilators, even with their NIV algorithm. However, the NIV algorithm improves, at least slightly and with a wide variation among ventilators, triggering and/or cycling off synchronization.

Monitoring of noninvasive ventilation by built-in software of home bilevel ventilators: a bench study.

BACKGROUND: Current bilevel positive-pressure ventilators for home noninvasive ventilation (NIV) provide physicians with software that records items important for patient monitoring, such as compliance, tidal volume (Vt), and leaks. However, to our knowledge, the validity of this information has not yet been independently assessed. METHODS: Testing was done for seven home ventilators on a bench model adapted to simulate NIV and generate unintentional leaks (ie, other than of the mask exhalation valve). Five levels of leaks were simulated using a computer-driven solenoid valve (0-60 L/min) at different levels of inspiratory pressure (15 and 25 cm H(2)O) and at a fixed expiratory pressure (5 cm H(2)O), for a total of 10 conditions. Bench data were compared with results retrieved from ventilator software for leaks and Vt. RESULTS: For assessing leaks, three of the devices tested were highly reliable, with a small bias (0.3-0.9 L/min), narrow limits of agreement (LA), and high correlations (R(2), 0.993-0.997) when comparing ventilator software and bench results; conversely, for four ventilators, bias ranged from -6.0 L/min to -25.9 L/min, exceeding -10 L/min for two devices, with wide LA and lower correlations (R(2), 0.70-0.98). Bias for leaks increased markedly with the importance of leaks in three devices. Vt was underestimated by all devices, and bias (range, 66-236 mL) increased with higher insufflation pressures. Only two devices had a bias < 100 mL, with all testing conditions considered. CONCLUSIONS: Physicians monitoring patients who use home ventilation must be aware of differences in the estimation of leaks and Vt by ventilator software. Also, leaks are reported in different ways according to the device used.

Volemic status influences the response of plasma atrial natriuretic factor to positive airway pressure.

STUDY OBJECTIVE; To evaluate interactive effects of volemic status and positive end-expiratory pressure (PEEP) on the plasma levels of atrial natriuretic factor (ANF) in assist-controlled mechanical ventilation (MV). DESIGN: Three successive protocols applied in randomized order to each participant. SETTING: Clinical investigation laboratory. PARTICIPANTS: Twenty-one young, healthy adults. INTERVENTIONS: The three protocols were as follows: (1) MV+PEEP, normovolemia; (2) MV+PEEP, hypervolemia; and (3) spontaneous breathing (SB), hypervolemia. In protocols 1 and 2, a preliminary period of SB lasting 2 h was followed by MV alone (0.5 h), MV+20 cm H2O PEEP (1 h), and a recovery period of SB (1.5 h). Hypervolemia was induced by the continuous i.v. infusion of 3 L of 0.9% NaCl in 5 h (protocols 2 and 3). MEASUREMENTS AND RESULTS: Heart rate, BP, and the plasma levels of immunoreactive ANF and catecholamines were measured serially. During hypervolemia, ANF significantly decreased when PEEP was added to MV (protocol 2: from 31.1 +/- 2.7 to 20.7 +/- 1.5 fmol/mL; p < 0.01). This did not occur in normovolemia (protocol 1: from 20.0 +/- to 16.7 +/- 1.2 fmol/mL; p = NS). The different effects of MV+PEEP in normovolemia and hypervolemia were not related to differences in circulating catecholamine levels. CONCLUSIONS: These results demonstrate for the first time (to our knowledge) that volemic status modulates the response of plasma ANF to PEEP in humans. The role of ANF in the water and salt retention induced by MV with PEEP might be limited to hypervolemic conditions.

Effect of expiratory positive airway pressure on sleep disordered breathing.

STUDY OBJECTIVES: We sought to determine the effect of expiratory positive airway pressure on end expiratory lung volume (EELV) and sleep disordered breathing in obstructive sleep apnea patients. DESIGN: Observational physiology study PARTICIPANTS: We studied 10 OSA patients during sleep wearing a facial mask. We recorded 1 hour of NREM sleep without treatment (baseline) and 1 hour with 10 cm H2O EPAP in random order, while measuring EELV and breathing pattern. RESULTS: The mean EELV change between baseline and EPAP was only 13.3 mL (range 2-25 mL). Expiratory time was significantly increased with EPAP compared to baseline 2.64 +/- 0.54 vs 2.16 +/- 0.64 sec (P = 0.002). Total respiratory time was longer with EPAP than at baseline 4.44 +/- 1.47 sec vs 3.73 +/- 0.88 sec (P = 0.3), and minute ventilation was lower with EPAP vs baseline 7.9 +/- 4.17 L/min vs 9.05 +/- 2.85 L/min (P = 0.3). For baseline (no treatment) and EPAP respectively, the mean apnea+hypopnea index (AHI) was 62.6 +/- 28.7 and 56.8 +/- 30.3 events per hour (P = 0.4). CONCLUSION: In OSA patients during sleep, the application of 10 cm H2O EPAP led to prolongation of expiratory time with only marginal increases in FRC. These findings suggest important mechanisms exist to avoid hyperinflation during sleep.