Sherwin Morgan

Oxygenation in status asthmaticus improves during ventilation with helium-oxygen.

OBJECTIVES To determine the effect of breathing helium-oxygen (HELIOX) mixtures on pulmonary gas exchange during severe asthma. DESIGN A retrospective case-match control design was used to compare the changes in alveolar to arterial gradient [(A-a)gradient] in the first 2 hrs of mechanical ventilation (MV) for status asthmaticus (SA) in patients who received HELIOX with those who did not. Patients were matched for diagnosis of asthma, ventilatory failure, ventilator mode and settings, and equivalent pharmacologic therapy. SETTING The adult and pediatric intensive care units of a tertiary-care hospital. SUBJECTS Adult and pediatric patients undergoing MV for SA. INTERVENTIONS Use of HELIOX or standard nitrogen-oxygen mixtures during MV. MEASUREMENTS AND MAIN RESULTS A total of 11 patients receiving HELIOX in the first 2 hrs of MV for SA were compared with 11 case-matched controls who did not. At baseline, the HELIOX and control groups had similar (A-a)gradients (216+/-92 torr and 226+/-82 torr, respectively). The (A-a)gradient decreased significantly to 85+/-44 torr after initiation of ventilation with HELIOX (p < .0003), whereas it did not change significantly in the control group in a similar time frame and during identical treatment without HELIOX. The reduction in (A-a)gradient in the HELIOX group facilitated a reduction in F(IO)2 from 0.8+/-0.2 initially to 0.4+/-0.1 at the time of the second blood gas determination, thus permitting greater concentrations of helium to be administered. CONCLUSIONS MV with HELIOX improves (A-a)gradient in patients with SA. Although this improvement adds little to routine therapy with supplemental oxygen, it does permit reduction in concentration of inspired oxygen to levels that maximize helium concentration and thus permit full benefits of HELIOX on lung mechanics to be realized in even the most severely ill asthmatics.

Modeling the effect of progressive endotracheal tube occlusion on tidal volume in pressure-control mode

A recognized hazard of prolonged endotracheal intubation is progressive airway occlusion resulting from deposition of secretions on the inner surface of the endotracheal tube (ETT). When volume-controlled ventilation is used, progressive ETT occlusion may be detected by monitoring the difference between peak and plateau airway pressures. In pressure-controlled modes, however, inspiratory airway pressures are preset and thus cannot act as a warning indicator. Instead, changes in delivered tidal volumes may aid the diagnosis of ETT occlusion. To determine whether tidal volume monitoring effectively de-tects progressive ETT occlusion, we mathematically modeled the response of a ventilator operating in pressure-controlled mode to increasing airway resistance. To corroborate our model, we then bench-tested the Siemens 300 and Puritan-Bennett 7200 ventilators by using a test lung and a series of ETTs ranging in size from 9.0 to 3.5 mm inner diameter to simulate progressive occlusion. We found that when pressure-controlled mode was used, progressive ETT occlusion did not reduce delivered tidal volumes until occlusion was nearly complete. We conclude that prolonged use of pressure-controlled mode may allow significant ETT obstruction to build up undetected, risking complete ETT occlusion and complicating the perioperative care of patients ventilated with this mode.

High-Flow Nasal Cannula and Aerosolized β Agonists for Rescue Therapy in Children With Bronchiolitis: A Case Series

Asthma and bronchiolitis are episodic obstructive pulmonary diseases characterized by bronchoconstriction, airway wall inflammation, increased mucus production, and air-flow obstruction. We present the cases of 5 infants treated for acute bronchiolitis with respiratory distress using a combination of high-flow nasal cannula oxygen (HFNC) and an Aerogen nebulizer to deliver aerosolized β-agonist therapy. In all infants, we found that HFNC resulted in a greater heart rate increase than delivery via a facemask. We also found that patients tolerated inhaled therapy better with HFNC than a facemask.

CARDIOPULMONARY EFFECTS OF NEBULIZED SODIUM NITROPRUSSIDE IN TERM INFANTS WITH HYPOXIC RESPIRATORY FAILURE

OBJECTIVE To study whether nebulized nitroprusside (neb-NP) improves oxygenation in term infants with hypoxic respiratory failure (HRF). STUDY DESIGN We studied 22 newborn term infants (gestational age, 39.7+/-0.4 weeks [mean+/-SEM]; birth weight, 3.6+/-0.1 kg) with hypoxia (Pao2<100 mm Hg) during mechanical ventilation (Fio2=1.0). Sodium nitroprusside (5 mg followed by 25 mg) was nebulized into the inspiratory arm of the ventilator circuit. Vital signs and arterial blood gas values were recorded after 20 minutes at each dose and before and after initiation of inhaled nitric oxide (iNO). RESULTS Pao2 increased significantly with 5 mg neb-NP (from 64.6+/-5.6 to 90.1+/-15.3 mm Hg, P=.04) and with 25 mg neb-NP (113.2+/-20.4 mm Hg, P=.009). Differences between mean Pao2 at 5 mg versus 25 mg neb-NP were also statistically significant (P=.03). When comparing the effect of neb-NP to iNO, the treatment-induced increases in Pao2 were similar (52.1+/-18.7 vs 62.2+/-18.2 mm Hg, respectively, P=not significant). CONCLUSIONS Neb-NP causes a dose-dependent increase in oxygenation in term infants with HRF, similar in magnitude to iNO* Neb-NP may be beneficial in infants with HRF when iNO is not readily available.

Cerebrovascular effects of nebulized nitroprusside (Neb-NP) during hypoxia-induced pulmonary hypertension in piglets |[diams]| 336

Intra-pulmonary administration of nitric oxide (iNO) or nitric oxide analogs such as nitroprusside produces selective pulmonary vasodilation. However, nitric oxide has been implicated in control of the cerebral as well as the pulmonary circulation. We tested the hypothesis that Neb-NP (a user-friendly analog of iNO) would adversely affect the cerebral circulation while improving pulmonary artery pressure (PAP) during hypoxia-induced pulmonary hypertension in piglets.

Effects of nebulized nitroprusside (Neb-NP) during hypoxia-induced pulmonary hypertension in piglets: tachyphylaxis, rebound, effect of pre-administration with Dipyridamole (Dip), and comparison with nebulized tolazoline (Tz) |[dagger]| 213

Inhaled nitric oxide (iNO) has been shown to selectively reduce pulmonary hypertension in several biologic models. However, iNO is not as convenient as one might wish. We tested the effects of Neb-NP (a user-friendly analog of inhaled nitric oxide) on pulmonary and systemic hemodynamics during pulmonary hypertension induced by hypoxia in piglets.

Use of heliox delivered via high-flow nasal cannula to treat an infant with coronavirus-related respiratory infection and severe acute air-flow obstruction.

Heliox, a helium-oxygen gas mixture, has been used for many decades to treat obstructive pulmonary disease. The lower density and higher viscosity of heliox relative to nitrogen-oxygen mixtures can significantly reduce airway resistance when an anatomic upper air-flow obstruction is present and gas flow is turbulent. Clinically, heliox can decrease airway resistance in acute asthma in adults and children and in COPD. Heliox may also enhance the bronchodilating effects of β-agonist administration for acute asthma. Respiratory syndromes caused by coronavirus infections in humans range in severity from the common cold to severe acute respiratory syndrome associated with human coronavirus OC43 and other viral strains. In infants, coronavirus infection can cause bronchitis, bronchiolitis, and pneumonia in variable combinations and can produce enough air-flow obstruction to cause respiratory failure. We describe a case of coronavirus OC43 infection in an infant with severe acute respiratory distress treated with heliox inhalation to avoid intubation.

Predictive Power of Oxygenation Index for Subsequent Development of Bronchopulmonary Dysplasia in Premature Infants

Predictive Power of Oxygenation Index for Subsequent Development of Bronchopulmonary Dysplasia in Premature Infants

Hemodynamic Effects of Nebulized Sodium Nitroprusside and Inhaled Nitric Oxide on Hypoxic Pulmonary Vasoconstriction in Piglets

Hemodynamic Effects of Nebulized Sodium Nitroprusside and Inhaled Nitric Oxide on Hypoxic Pulmonary Vasoconstriction in Piglets